MANUFACTURING PROCESS CONTROL SYSTEMS AND METHODS

MECANISMES DE COMMANDE DE PROCEDE DE FABRICATION ET METHODES

English Abstract

A method of controlling a manufacturing process having a machine to form a material in to a component. The method comprises the steps of establishing an initial set of operating parameters for the machine, producing an initial component from the machine, inspecting the component to determine its acceptability relative to a desired component, determining a variation in the operating parameters to improve the acceptability of the component, effecting changes in the operating parameters and inspecting subsequent components to determine their acceptability.

French Abstract

Il est décrit une méthode pour contrôler un procédé de fabrication comportant une machine destinée à transformer un matériau en un composant. La méthode comprend les étapes suivantes : établissement dun premier ensemble de paramètres de fonctionnement pour la machine, production dun premier composant à partir de la machine, inspection du composant pour déterminer son acceptabilité par rapport à un composant souhaité, détermination dune variation des paramètres de fonctionnement pour améliorer lacceptabilité du composant, modification des paramètres de fonctionnement et inspection des composants suivants pour déterminer leur acceptabilité.

Claims

CLAIMS
1. A method of controlling a manufacturing process having a production
system to form a
material into a component, said method comprising:
a) establishing an initial set of operating parameters for said production
system, the initial
set of operating parameters based on an original production data set and a
design model data set
stored in a data store, and forwarding the initial set of operating parameters
from the data store to
a parameter generator;
b) the parameter generator generating machine inputs from the forwarded set of
operating
parameters, wherein the parameter generator directly communicates the machine
inputs to the
production system;
c) the production system producing the component from the material;
d) an inspection system inspecting the component, wherein the inspection
system uses at
least a sensor to collect data specific to the component and accesses the data
store to compare the
collected data with at least the design model data set to determine whether
the component is
acceptable or unacceptable;
e) storing the collected data in the data store in either a good part data set
if the
component is acceptable or in a bad part data set if the component is
unacceptable;
f) a knowledge management system accessing the data store, wherein the
knowledge
management system automatically utilizes one or more algorithms to correlate
the collected data
with one or more data sets in the data store, including the original
production data set, the design
model data set, the good part data set, and the bad part data set, to create a
new set of operating
parameters for the production system without human intervention;
g) transferring the new set of operating parameters from the knowledge
management
system to the parameter generator; and
h) iteratively repeating steps b) to g) one or more times to refine quality of
further
components.
2. The method of claim 1 wherein each component produced by the production
system has a
unique identifier associated with the component and its collected data and
said unique identifier
allows each component to be individually identified and reproduced based upon
the collected
data corresponding to its unique identifier.
43

3. The method of claim 1 wherein said knowledge management system accesses
a digital
representation of said component to help create the new set of operating
parameters.
4. The method of claim 1 wherein said knowledge management system accesses
said initial
set of operating parameters to help create the new set of operating
parameters.
5. The method of claim 1 wherein an operator interface is provided to
optionally effect
adjustment of said operating parameters, said operating interface providing an
input to said
knowledge management system and said knowledge management system deteimining
changes of
said operating parameters as a result of inputs from said operator interface.
6. The method of claim 1 wherein the collected data is communicated to
other systems
producing similar components.
7. The method of claim 1, wherein the collected data includes dimensional,
surface, volume,
and micro structure data and data on structural inner inclusions or voids.
8. The method of claim 1, wherein the one or more algorithms include data
mining, artificial
intelligence (AI), neural networks, K-Nearest Neighbor (KNN), Restricted
Coulomb Energy
(RCE), or iterative learning control (ILC).
9. A machine to form a component, said machine comprising
a production system to form said component from a material based upon an
initial set of
operating parameters,
an inspection system, wherein at least one sensor of the inspection system
inspects the
component to collect data to allow the inspection system to determine
acceptability of said
component relative to reference data,
a data store in electonic communication with the inspection system, the data
store
containing reference data and storing the collected data obtained from said
inspection system,
wherein the reference data includes data of operating parameters associated
with an acceptable
44

component stored in one data set and data of operating parameters associated
with unacceptable
component stored in another data set, and wherein the collected data is stored
in either the one
data set or the another data set according to whether the component is
acceptable or
unacceptable, and
a knowledge management system in electronic communication with the data store,

wherein the knowledge management system automatically accesses said data store
after
collection and storage of the collected data to correlate the collected data
and the reference data
in order to automatically create a new set of operating parameters used to
create a subsequent
component, wherein the knowledge management system iteratively accesses the
data store,
correlates collected data from a most recently produced component and the
reference data, and
automatically creates a new set of operating parameters between each
successive component
production cycle.
10. The machine of claim 9 wherein said collected data includes a digital
representation of
said component.
11. The machine of claim 9 including an operator interface communicating
with said
knowledge management system.
12. The machine of claim 9 including a communication module to transfer
data between the
machine and one or more other machines.
13. The machine of claim 9 wherein the knowledge management system
selectively operates
on the reference data and collected data using at least one of a plurality of
data manipulation
algorithms to determine appropriate variation in said operating parameters.

Description

CA 02931412 2016-05-27
CA Patent Application
Agent Ref: 76798/00016
1 MANUFACTURING PROCESS CONTROL SYSTEMS AND METHODS
2
3 TECHNICAL FIELD
4 [0001] The present invention relates to a process control for a
manufacturing process,
such as a molding systems and methods for controlling such a process. The
present invention is
6 exemplified by application to a molding system, more specifically, to a
hot-runner system, a melt
7 flow modular assembly, an injection molding method, an injection mold,
hot runner, and a valve
8 gate device but is applicable to other manufacturing processes.
9
BACKGROUND
11 [0002] Injection molding (British English: moulding) is a
manufacturing process for
12 producing parts from both thermoplastic and thermosetting plastic or
other materials, including
13 metals, glasses, elastomers and confections. Material is fed into a
heated barrel, mixed, and
14 forced into a mold cavity where it cools and hardens to the
configuration of the cavity. After a
product is designed, usually by an industrial designer or an engineer, molds
are made by a mold
16 maker (or toolmaker) from metal, usually either steel or aluminum, and
precision-machined to
17 form the features of the desired part. Injection molding is widely used
for manufacturing a
18 variety of parts, from the smallest component to entire body panels of
cars.
19 [0003] Injection molding utilizes a ram or screw-type plunger
to force molten plastic
material into a mold cavity; this produces a solid or open-ended shape that
has conformed to the
21 contour of the mold. It is most commonly used to process both
thermoplastic and thermosetting
22 polymers, with the former being considerably more prolific in terms of
annual material volumes
23 processed.
24 [0004] Thermoplastics are prevalent due to characteristics
which make them highly
suitable for injection molding, such as the ease with which they may be
recycled, their versatility
26 allowing them to be used in a wide variety of applications, and their
ability to soften and flow
27 upon heating.
28 [0005] Injection molding consists of high-pressure injection of
the molten plastics
29 material, referred to as plastic melt, into a mold, which shapes or
forms the polymer into a
desired shape. Molds can be of a single cavity or multiple cavities. In
multiple cavity molds,
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1 each cavity can be identical and form the same parts or can differ and
produce multiple different
2 geometries during a single cycle. Molds are generally made from tool
steels, but stainless steels
3 and aluminum molds are suitable for certain applications.
4 [0006] Aluminum molds typically are ill-suited for high-volume
production or parts with
narrow dimensional tolerances, as they have inferior mechanical properties and
are more prone
6 to wear, damage, and deformation during injection and clamping cycles;
however, they are more
7 cost-effective in low volume applications as mold fabrication costs and
time are considerably
8 reduced. Many steel molds are designed to process well over a million
parts during their lifetime
9 and can cost hundreds of thousands of dollars to fabricate.
[0007] When thermoplastics are molded, typically pelletized raw material is
fed through
11 a hopper into a heated barrel with a feed screw. Upon entrance to the
barrel, the thermal energy
12 increases and the Van der Waals forces that resist the relative flow of
individual chains are
13 weakened as a result of increased space between molecules at higher
thermal energy states. This
14 reduces its viscosity, which enables the polymer to flow under the
influence of the driving force
of the injection unit. The feed screw, typically an Archimedean screw,
delivers the raw material
16 forward, mixes and homogenizes the thermal and viscous distributions of
the polymer, and
17 reduces the required heating time by mechanical shearing of the material
and adding a significant
18 amount of frictional heating to the polymer. The material is fed forward
through a check valve
19 and collects at the front of the screw into a volume known as a shot.
The shot is the volume of
material, which is used to fill the mold cavity, compensate for shrinkage, and
provide a cushion
21 (approximately 10% of the total shot volume which remains in the barrel
and prevents the screw
22 from bottoming out) to transfer pressure from the screw to the mold
cavity. When enough
23 material has gathered, the material is forced at high pressure and
velocity through a gate and into
24 the part-forming cavity by moving the screw along its axis. To prevent
spikes in pressure, the
process normally utilizes a transfer position corresponding to a 95-98% full
cavity where the
26 screw shifts from a constant velocity to a constant pressure control.
Often injection times are
27 well under one second and the cooling time of the part in excess of four
seconds. Once the screw
28 reaches the transfer position the packing pressure is applied, which
completes mold filling and
29 compensates for thermal shrinkage, which is quite high for
thermoplastics relative to many other
materials. In thermal gating the packing pressure is applied until the
material located in the mold
31 gate (cavity entrance) solidifies. The gate is normally the first place
to solidify through its entire
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1 thickness due to its small size. Once the gate solidifies, no more
material can enter the cavity;
2 accordingly, the screw returns and acquires material for the next cycle
while the material within
3 the mold cools so that it can be ejected and be dimensionally stable.
This cooling duration is
4 dramatically reduced using cooling lines to circulate water or oil from a
thermolator or
preferably using an organic refrigerant. Once the required temperature has
been achieved, the
6 mold opens and an array of pins, ejectors, etc. is driven forward to
remove the article from the
7 mold, referred to a "de-molding". Then, the mold closes and the process
is repeated. The thermal
8 gating, where the closing of the gate is accomplished by solidified
plastic, is possible for small
9 flow requirements with a melt flow channel with small gates. For high
plastic flow rates, a valve
gated hot runner is used in which mechanical valves control the flow of melt
from a common
11 supply, or hot runner, to the mold. A modulating assembly modulates the
melt flow. Faster cycle
12 time may be attained because no gate cooling is required to shut off the
melt flow, and no gate
13 re-heating is required to open the gate to the melt flow.
14 [0008] A parting line, sprue, gate marks, valve pin marks, and
ejector pin marks are
usually present on the final part, often even after prolonged cooling time.
None of these features
16 are typically desired, but are unavoidable due to the nature of the
process. Gate marks occur at
17 the gate that joins the melt-delivery channels (sprue and runner) to the
part-forming cavity.
18 Parting line and ejector pin marks result from minute misalignments. The
wear, gaseous vents,
19 clearances for adjacent parts in relative motion, and/or dimensional
differences of the mating
surfaces contacting the injected polymer also create marks on the molded
surface of the part. The
21 dimensional differences can be attributed to non-uniform, pressure-
induced deformation during
22 injection, machining tolerances, and non-uniform thermal expansion and
contraction of mold
23 components, which experience rapid cycling during the injection,
packing, cooling, and ejection
24 phases of the process. Mold components are often designed with materials
of various coefficients
of thermal expansion. These factors cannot be simultaneously accounted for,
without
26 astronomical increases in the cost of design, fabrication, processing,
and the part quality
27 monitoring. The skillful mold and part designers, will position these
aesthetic detriments in
28 hidden areas, if feasible.
29 [0009] Inevitably, to eliminate the gate marks, it is necessary to
improve gate performance. The
gate marks and gate residuals are called vestige. The molding quality is
directly apportioned to
31 shape, configuration, degradation of the vestige and vestige height and
shape. The gate quality is
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1 nowadays-major issue in injection molding art, particularly for food and
beverage packaging.
2 [00010] It is well-known in the field of injection molding art
that some structure must be
3 placed in the mold gate, at a particular time in the molding cycle, to
inhibit the flow of molten
4 material into the cavity of a mold, so that the molded part may be
cooled, and subsequently
opened to remove the molded parts. This must be done without creating drool of
the molten
6 material in the molding surface. This drool would create undesirable
marks on the next moldings,
7 and this is largely un-acceptable.
8 [00011] As noted above, there are essentially two broad
categories of melt flow
9 modulating assemblies, or flow inhibiting techniques known in the field
of injection molds,
namely, thermal gating in which the gate at the exit of the nozzle is rapidly
cooled at the
11 completion of the injection operation to form a solid or semi-solid plug
of the material being
12 injected into the gate; and valve gating in which a mechanical means is
employed to inhibit the
13 flow of material being injected into the mold cavity.
14 [00012] Each category has its own advantages and disadvantages
relative to the other.
Numerous systems using thermal gating are known in the art of the hot-runners.
16 [00013] Valve gating systems are generally of one of two types,
namely inline and lateral
17 systems of gate closing. A wide variety of systems of each type have
been developed. Referring
18 now to the inline gating choices, there is in the art of the injection
molding, mainly three types of
19 valve gate closing choices: axial pin motion, rotary pin motion with
shutoff, and a rotary pin with
dynamic melt flow control without positive shutoff.
21 [00014] Many valve mechanisms used in the injection molding
industry are constructed in
22 such a way as to move a valve pin assembly in an axial direction along
the nozzle melt channel
23 from fully open to fully closed position. This is the predominant
structure when comparing based
24 on the motion of the valve pin.
[00015] An example of this is found in U.S. Patent No. 4,268,240, U.S.
Patent No.
26 6,086,357, U.S. Patent publication No. 2011/0293761 Al, U.S. Patent No.
8,047,836 B2, U.S.
27 Patent No. 7,600,995 B2, or for example, U.S. Patent No. 7,044,728 B2
and U.S. Patent
28 publication No. 2005/0100625 Al where the plastic is transferred from a
hot-runner manifold to
29 a nozzle. This type of the melt delivery goes around the pin and then
rejoins the melts from each
side of the pin, and reconstitutes the tubular flow just below the valve pin
tip. Therefore, this
31 kind of the valve pin motion, being axial, causes melt flow, arriving
laterally at the pin, to be
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1 divided by the valve pin or stem.
2 [00016] The flow is rejoined again into a single path as it
passes in to the mold cavity,
3 resulting in moldings with undesirable weld lines created by the once
divided polymer volumes,
4 visibly affecting quality of the products. These weld lines can adversely
affect both the aesthetic
and performance qualities of the final molded product, and it is significantly
advantageous to
6 avoid their creation when molding certain products.
7 [00017] Some alternatives to prevent melt separation have been
proposed, e.g. the valve
8 pin may be shielded, as in U.S. Patent No. 4,412,807 which shows an
apparatus in which the
9 plastic flow channel in the nozzle is kept separate from the valve pin in
an effort to avoid
dividing the melt stream. The channel is a crescent shaped cross section,
which is known to be
11 less than ideal for encouraging plastic flow, especially in the opposing
sharp corners.
12 Furthermore, when the valve pin is in the open position to let plastic
material to pass into the
13 mold cavity, it creates a stagnant area of poor plastic flow directly
adjacent the front face of the
14 pin. These areas of poor plastic flow can result in material
degradation, which can adversely
affect the performance and physical properties of the molded product.
16 [00018] U.S. Patent No. 4,925,384 shows a similar design that
permits the plastic to come
17 into contact with the valve pin but restricts it from passing around the
pin to form a weld line.
18 This patent describes an approach that does not cause pronounced
division of the melt flow. This
19 design also suffers from a melt channel with sluggish flow areas and
requires difficult and
expensive machining processes to produce the nozzle housing, having an unusual
melt channel
21 cross section.
22 [00019] Alternatively, valve gates may be structured to rotate
the pin and close or open the
23 gate that way.
24 [00020] U.S. Patent No. 3,873,656 shows a valve having taps,
which rotate to open or
close. This is similar to the approach described above. It is not compact or
easy to manufacture
26 and has sharp edges, susceptible to damage, where it mates with the
sprue channels.
27 [00021] A rotating nozzle is shown in U.K. Patent No. 872,101.
The entire injection unit
28 nozzle rotates on an axis parallel to the flow of plastic as opposed to
the perpendicular or angular
29 rotation axis of the two patents mentioned previously. The nozzle front
portion remains in forced
contact with the delivery bushing, to prevent plastic leakage between the two.
The construction
31 shown is very bulky, consuming a substantial amount of space.
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1 [00022] Further example of the attempt to reduce weld line and
part marks is disclosed in
2 the U.S. Patent No. 5,499,916 where the stem rotates with limited contact
with the melt flow but
3 does not allow melt separation.
4 [00023] A further example to improve melt flow delivery, and
melt flow temperature
uniformity as well as hot runner balancing is attempted in the application of
the rotating pin is
6 disclosed in U.S. Patent Publication No. 2007/0065538 Al. The valve pin
is operatively
7 connected to a motor that has fast acceleration and deceleration rates.
The valve pin is made in
8 the form of an Archimedean screw or screw pump so that the pin is
positioned within the melt
9 flow assembly in the hot-runner nozzle. By rotating and pumping melt flow
in the direction of
the melt flow, the valve-pin "pump" reduces pressure drop within the melt flow
assembly,
11 supposable creating favorable melt delivery and melt conditioning.
12 [00024] However, when rotation is in the direction to retard
melt flow of the molten
13 material traveling in the direction of the cavity, higher-pressure drop
is created in the melt flow
14 assembly of the hot-runner and therefore, balancing the pressure and
flow to ensure that drop-to-
drop uniformity is maintained. Besides the positive effect on the uniformity
of the melt, that is
16 critical for food packaging and medical parts, this valve gate molding
system can effectively
17 produce acceptable quality gate vestige mark and at the same time ensure
that the closing of the
18 gate is accomplished by rotation of the pin screw "pump" within melt in
the melt flow assembly
19 and at the same time improve temperature uniformity of the melt in the
hot-runner nozzle.
[00025] In each of the systems described above, and in inline systems,
generally, a valve
21 pin aligned with the gate is moved parallel to the direction of movement
of molten material
22 (generally referred to as "melt") through the gate, between a position
wherein the pin extends
23 into the gate to block flow through the gate, and a position wherein the
pin is retracted from the
24 gate permitting flow there-through into the mold cavity. In order to be
aligned with the gate, the
valve pin is located inside the injection nozzle and is at least partially
within the flow path of the
26 melt.
27 [00026] For these and other reasons, inline valve gating
suffers from a variety of
28 problems.
29 [00027] One common problem is wear of the valve pin due to
contact with the nozzle
and/or gate, which can lead to leaks or failure of the valve.
31 [00028] Another common problem is the conversion of the melt
from the tubular flow
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1 entering the nozzle to an annular (or other non-continuous) flow, which
is caused by the valve
2 pin or other related components being within the melt flow. Such a non-
continuous flow can
3 result in weld or knot lines in the molded product produced as the melt
flow recombines within
4 the gate or mold cavity, and this can result in weakened or unacceptable
molded products. This is
particularly a problem when molding preforms for water containers where good
part appearance
6 and gate quality are an essential for successful sales of bottled water
or other clear liquids.
7 [00029] The water bottles are made in a two-stage process and,
require in a first stage to
8 produce a preform, and in a second-stage the preform is air inflated
against a cavity of the mold
9 in a shape of the bottle. The bottle preforms are made from the
polyethylene terephthalate,
abbreviated as PET. The PET preform molding process, in particular, requires
tubular melt flow,
11 and having the pin inside the melt flow, does not help improve melt flow
in the molding process.
12 [00030] During the injection process, the molten plastic
material is injected into the mold
13 cavity under very high pressure, often above 15,000 PSI. Once injected,
in a short injection time,
14 often less than one second, molten plastic enters cooling and
solidification phase lasting 2 to 30
seconds. During this process, a definite time is selected, within hold time in
the process, when to
16 close the valve gate. Closing valve gate means that gate volume should
be filled by pin tip
17 volume so as to block plastic flow through the gate.
18 [00031] The axial movement of the valve pin assembly
accomplishes this.
19 [00032] In principle, the valve pin conical surface and gate
conical surface each have a
complementary sealing surface. When these surfaces are brought together the
flow of the
21 material through the gate stops.
22 [00033] Usually, as it is well recognized in the injection
molding art, the gate closing is
23 initiated just about when the cavity is filled, and the injection time
hold interval is about to end.
24 After the valve pin is fully forward and in a predominantly closed
position, no more plastic melt
is possible to enter the cavity. Mold cooling helps to remove heat from the
molded part and helps
26 to solidify the part and cool it so that can be handled in post molding
cooling process. The post
27 molding process, by itself is the complex process when molding PET
preforms or any food
28 packaging containers like K-cups. The post molding process often
requires specialty equipment
29 and additional complexities.
[00034] The valve pin stays closed until the mold is fully open and perhaps
even just
31 before mold fully closed position after ejection of the molded part. Of
course, timing when to
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1 start opening the valve gate is largely dependent on the valve pin
driving apparatus.
2 [00035] Fast acting valve gate systems allow for more
flexibility and better timing and
3 control of the gate mechanism. Currently air piston operated valve gates
require closing time up
4 to one second due to lack of proportionality between air pressure and
axial force. Once air piston
start moving it only stops at the hard stop at the end of the stroke.
Similarly, servo motor driven
6 pins, introduce nonlinearity largely because gear box and nonlinearities
in magnetic structures of
7 the current servo motors and drives.
8 [00036] As noted above, there are various options for the valve
gate pin configuration and
9 ways for opening and closing the gate. There are, however, only a few
options for powering the
valve pins. It is known in the art of injection molding and hot runners to
provide an electrical or
11 fluid actuator to power the pin of the valve gate.
12 [00037] The electric motors, air motors or hydraulic motors
mostly power the rotary pins.
13 For axially moving valve pin, typically, the actuators are the pneumatic
or hydraulic type. The
14 moving air piston type actuator is predominantly used today to power
axially moving valve gate
pin due to its simplicity and compactness. All other motors, including servo
motors and drives
16 require conversion of rotary to linear motion via transmission elements
or gearbox.
17 [00038] The disadvantage of using an air piston cylinder to
power the valve gate
18 assembly, besides extensive drilling of the substantial number of air
channels, is that the
19 pneumatic piston actuator may require specialized valves and air hoses
to deliver and control the
compressed air. The pressure of the air supply in each location is different
and is very difficult to
21 ensure consistent high air pressure at each valve pin location. Even
when air pressure is
22 available, often in range 75 PSI (pounds per square inch) to 120 PSI,
flow rate, cleanliness and
23 capacity of the air compressors may not be always adequate. Often just
differences in hose length
24 will change the mold performance due to different air supply pressure
seen by each valve gate.
Just the fact that the piston seal stiction alone, in the multi cavity mold,
may be different at
26 different operating temperatures is material and illustrates the level
of randomness involved in
27 these systems. The mechanical tolerance, location in the mold, air
supply line arrangements, and
28 environmental contamination, maybe enough to result in less than an
optimal valve gate opening
29 or closing time. These and other variations result in differences in
part quality and quality of the
gate vestige. These and other variations are not desirable.
31 [00039] Yet another disadvantage of the air operated valve
gates is that the pin can only be
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1 positioned at the fully open position or at the fully closed position,
and cannot be positioned
2 between these two positions, unless additional pistons or complexities
are installed. Moreover, as
3 the compressed air temperature varies during the day, this inhibits
molding good parts without
4 continuous process adjustments and monitoring. A further disadvantage of
the air piston operated
valve gates is that they are relatively easy to get contaminated by the PET
dust or air impurities
6 and then get slow to move and not very accurate in the closing position
of the pin.
7 [00040] A further disadvantage is that the air exhaust
contaminates freshly molded parts,
8 and parts for medical and food packaging industry are very sensitive to
parts cleanliness.
9 [00041] The most important disadvantage of the air operated
valve gate systems is that air
is exhausted to the environment and large volume of air is used for these
operations.
11 Compressing and delivering air to the molding system is very expensive
and compressed air is
12 delivered with overall compressor efficiency less than 40%. That means
only a portion of the
13 electrical energy used for compressing and delivering compressed air is
used and converted into
14 a useful motion of the valve pin.
[00042] Hydraulic pistons are often used for large valve gated assemblies
and relatively
16 high axial force requirements, but using hydraulic oil and mist in the
vicinity of freshly molded
17 medical or food packaging parts, is not acceptable.
18 [00043] Electric motors with rotary motion are being used for
generating axial motion.
19 [00044] The motors and gear transmission assemblies are very
large in volume and mostly
not suitable for applications with a higher number of cavities.
21 [00045] In some applications, like food packaging and medical
molding industry, the use
22 of the electric actuators for the valve gates is demanded due to their
cleanliness. Air and
23 hydraulics just generate too much of the air contaminant dispersion to
be acceptable in clean
24 environments like medical moldings and food packaging.
[00046] Electrical actuators are becoming more compact and being now
available in a
26 variety of the configurations, which allows them to be used as actuators
for the valve gate
27 assemblies in injection molding systems.
28 [00047] One example of such an electrically operated valve gate
pin is disclosed in the
29 U.S. Patent Publication No. 2005/0100625 Al. In that patent, a valve
gate assembly for
regulating a flow of molten material into a mold is operated by the electric
motor. The electric
31 motor operates via a mechanical transmission to move the valve pin, and
infinitely positions the
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1 valve pin between the fully closed position and the fully open position
by using a position
2 feedback device in a closed loop servo control mode. Various electric
motors are proposed for
3 this application, but servo controls of this nature are largely
impractical for high cavitation molds
4 where 96 to 144 individual PET preforms may be molded within each machine
cycle. Besides, a
feedback device installed for each individual pin position feedback is
impractical and very
6 difficult to integrate in the molds and hot runner assemblies. Even if,
and when used, the closed-
7 loop servo motor powered valve pin, must maintain the valve pin in a
closed position when the
8 operator's gate is open to prevent hot plastic melt spray and injury to
operators entering the mold
9 area. The servomotor must maintain positioning accuracy and stiffness
throughout the injection
cycle, and that means high current is required to just maintain the position.
Motors must be rated
11 for 100% duty cycle. It is easy to see how overheating of the electric
motor can occur, and then
12 additional complexities must be built into a servo system to overcome
that. Molders today just
13 are not ready to put up with maintenance and servicing requirements of
hundreds of the
14 individually controlled servo motor systems, despite the valve pin
positioning accuracy and
associated benefits of the accurate individual valve pin positioning.
16 [00048] U.S. Patent No. 5,556,582 describes the system wherein
an adjustable valve pin is
17 operated by the servo controlled motor. The valve pin can be dynamically
adjusted by a
18 computer according to pressure data read at or near the injection gate.
If multiple valves are used,
19 each is independently controlled. A hot runner nozzle is not provided.
Also, as the system is
used, the repetitive actions of the valve pin cause significant wear on the
tip of the valve pin.
21 This wear, is a result of the repeated impact with the mold cavity.
Basically, an adjustable valve
22 is provided that is adjusted by the close loop servo system, while the
plastic melt material is
23 flowing through the gate into the mold cavity. The computer controls the
servo motor, based on a
24 sensor in the cavity, preferably stated as being cavity pressure closed
loop servo system. This
control is complex and not easy to implement in large cavitation molds.
26 [00049] U.S. Patent No. 6,294,122 B1 describes the system of
driving the pin axially
27 along the nozzle melt channel in a closed-loop control by operatively
connecting the pin with
28 linearly moving mechanical transmission assembly, which converts the
rotational movement of
29 the motor assembly into linear motion. The conversion assembly is a
gearbox or screw and a nut
threadingly engaged with each other or alternatively driven by the rack and
pinion gear
31 assembly. Positioning is based on the proportional integral and
derivative (PID) controls getting
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1 position feedback from an encoder. This approach, while sophisticated and
allowing for very
2 precise valve pin positioning, is complex and overly sophisticated for
the applications and the
3 current state of the art in the plastic industry today. Besides, having
transmission elements
4 between an electrical rotor and vale pin introduces unacceptable response
delay. The motor gear
assembly use is therefore limited to large molds often used in automotive
applications where fast
6 pin closing moves are not required. Besides, having bulky motor and a
gearbox between the
7 molding platens of the injection machine limits the opening stroke and
type of the parts that can
8 be molded with this arrangement. Again this is generally not practical
for high cavitation counts
9 and high production rates.
[00050] In a similar attempt to operate a valve pin with a clean electrical
motor and
11 accommodate a large number of drops, U.S. Patent Publication No.
2011/0293761 Al describes
12 a system where a plurality of pins is attached to an electro-
magnetically driven plate so the valve
13 pins are movable responsive to movement of the actuation plate. No
proposed driving logic is
14 offered as to how to control the largely uncontrollable force at the end
of the stroke. When two
magnetic assemblies of the type shown in this published application get very
close together, the
16 impact and noise generated by the plate contact is likely to damage
connecting elements of the
17 valve pin if not mitigated with additional complexities. It would also
likely result in a very slow
18 movement of the valve pin assembly because it would take substantial
time to establish a
19 magnetic field in a large magnetic storage like electromagnets, and to
subsequently reverse that
field. To collapse the electromagnetic field in assemblies of this size is a
lengthy and involved
21 process, even when sophisticated electronic devices are used. The
magnetic structures of this size
22 and mass do not allow for fast current switching, because the collapsing
magnetic field and
23 changing polarity will generate back electromotive force of significant
proportions. Simply, a
24 large mass does not lend itself for fast opening and closing valve pins.
[00051] At the opposite spectrum of valve pin actuations, small
electromagnetic actuators
26 have been proposed and tested. The most promising method of direct pin
activation is the method
27 of controlling pin closed and pin open position with two solenoids but
aided by a spring: one to
28 hold the valve open and one to hold the valve closed. Since the
electromagnetic solenoid
29 actuators are inherently unidirectional and a large force is required at
the end of the stroke, it is
very difficult to electronically control the movement of the pin.
31 [00052] Also the force exerted by these solenoid actuators is
proportional to the square of
11
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1 the current input, and decreases as the function of the air gap between
the actuator and the
2 armature. Therefore, as good as these actuators are, their control is
difficult for consistent
3 operation. Having a mechanical spring is also an undesirable feature.
4 [00053] It is critical for the valve pin to arrive exactly at
the end of the stroke with exactly
near zero velocity. This is often defined in state of the art as perfect "soft
landing". The receiving
6 end actuator must do exactly as much work as was done against friction
and adhesive force of
7 the melt along the entire transition from open-to-close or vice versa. If
the actuator does not do
8 this much work, the valve pin will stop before the end of the stroke. If
the actuator does any
9 more than the exact correct work, the valve pin arrives at the end of the
stroke with non-zero
velocity where it can impact valve seat if contacts it, or imparts the shock
and vibration on the
11 valve pin assembly by impacting against a hard stop. The non-uniform
force, and other effects
12 cause disturbances of the valve pin assembly and make this system very
difficult to control.
13 [00054] None of the foregoing valve pin activation and control
techniques offer
14 individually controlled valve pin structure in a small and compact size
that will move the pin
axially along the melt flow channel, without any interconnecting, converting
mechanical
16 transmission elements to reduce speed, or convert power or convert
torque. These and other
17 systems require installation of the position or process feedback devices
in areas that has limited
18 space. The mechanical structures have very small structural safety
margins, and any additional
19 requirements for installation of any feedback devices make the systems
very complex. This is
particularly difficult in applications with an increased number of cavity
drops and reduced drop
21 to drop (pitch) spacing.
22 [000551 The above discussion exemplifies the challenges in
controlling a manufacturing
23 process to produce components at a high production rate with a
consistently high quality.
24 Attempts to maintain machine operations with fixed input parameters
inevitably leads to a
variation of quality as ambient and input conditions change. For example a
small change in the
26 characteristics of the feedstock, or a change in the ambient temperature
in which the process is
27 performed, may produce a deleterious effect on the component being
produced, which will lead
28 to rejected components if an adjustment is not made.
29 [00056] Attempts to compensate for such variation utilize
feedback controls, either open
loop or closed loop systems. Feedback systems have part of their output signal
"fed back" to the
31 input for comparison with the desired set point condition. The type of
feedback signal can result
12
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1 either in positive feedback or negative feedback.
2 [00057] In a closed-loop system, a controller is used to
compare the output of a system
3 with the required condition and convert the error into a control action
designed to reduce the
4 error and bring the output of the system back to the desired response.
Then closed-loop control
systems use feedback to determine the actual input to the system and can have
more than one
6 feedback loop.
7 [00058] Closed-loop control systems have many advantages over
open-loop systems. One
8 advantage is the fact that the use of feedback makes the system response
relatively insensitive to
9 external disturbances and internal variations in system parameters such
as temperature. However
it has been found through experiments and customer feedback that close
controls executed in a
11 classical way do not produce the adjustments necessary to maintain good
quality articles. For
12 example, in the case of temperature, the sensor is the thermocouple.
(TC). It measures
13 the temperature at the single point and controller is attempting to
maintain the same temperature
14 at that point. Even if this is possible, quality of the final product
may not be good, because of the
very many variables that can affect the part physical dimensions, and perhaps
flow characteristic
16 of the melt.
17 [00059] It is therefore an object to the present invention to
obviate or mitigate the above
18 disadvantages.
19
SUMMARY
21 [00060] In an aspect of this invention, there is provided a
method of controlling a
22 manufacturing process having a machine to form a material in to a
component. The method
23 comprises the steps of establishing an initial set of operating
parameters for the machine,
24 producing an initial component from the machine, inspecting the
component to determine its
acceptability relative to a desired component, determining a variation in the
operating parameters
26 to improve the acceptability of the component, effecting changes in the
operating parameters and
27 inspecting subsequent components to determine their acceptability.
28 [00061] According to a further aspect of the present invention
there is provided a machine
29 to form a component. The machine includes a production system to form
the component from a
material, and an inspection system to determine acceptability of the component
relative to a
13
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1 reference. A data store retains information obtained from the inspection
system, and a knowledge
2 management system for analyzing and predicting data accesses the data
store and determines
3 variations in operating parameters of the production system.
4
BRIEF DESCRIPTION OF THE DRAWINGS
6 [00062] FIG. 1 is a sectional view of a multi-cavity valve
gated hot runner injection
7 molding system or apparatus to mold plastic articles like PET preforms;
8 [00063] FIG. 2 is a section on the line II-II of FIG. 1;
9 [00064] FIG. 3 is an enlarged section of an upper portion of
FIG. 2;
[00065] FIG. 4 is an enlarged section of a lower portion of Figure 2;
11 [00066] FIG. 5 is an enlarged section of a portion of FIG. 4
showing a valve pin closed
12 portion;
13 [00067] FIG. 6 is a section on the line VI-VI of FIG. 3;
14 [00068] FIG. 7 is an enlarged section of a portion of FIG. 3
showing a valve pin locking
assembly;
16 [00069] FIG. 8 is a view on the line VIII of FIG. 6;
17 [00070] FIG. 9 is a view on the line IX ¨IX of FIG. 7;
18 [00071] FIG. 10 is a simplified block diagram of an electronic
valve gate drive controller
19 used with the apparatus of FIG. 1;
[00072] FIG. 11 is a plot showing the relationship between force and
current over time
21 provided by the actuator of FIG. 2;
22 [00073] FIG. 12 is an enlarged section similar to Figure 3 of
an alternative embodiment of
23 a Lorentz force actuator assembly;
24 [00074] FIG. 13 is a section similar to FIG. IA showing a
further embodiment of a force
actuator assembly;
26 [00075] FIG. 14 is a section of the multi-pin array actuator
operated by a single Lorentz
27 force actuator assembly of FIG. 1;
28 [00076] FIG. 15 is a flow diagram of a single iteration of
waveform control signals;
29 [00077] Fig. 16 is a block diagram showing an open loop
positive feedback control
production system;
14
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1 [00078] Fig. 17 is a block diagram of a negative feedback
control system;
2 [00079] Fig. 18 is a representation of a data mining model
suitably used with the system
3 and apparatus of Fig. 16;
4 [00080] Fig. 19 is a schematic diagram of MAXIcastTM casting
machine working in an
open loop (operator modifies process parameters based on bad wheel x-ray
images) with
6 WHEELinspectorTM (ADR); and
7 [00081] Fig. 20 is a schematic diagram of MAXIcastTM casting
machine working in an
8 open loop positive feedback with WHEELinspectorTM (ADR-Automatic Defect
Recognition).
9 [00082] Corresponding reference characters indicate
corresponding components
throughout the several figures of the drawings. Elements in the several
figures are illustrated for
11 simplicity and clarity and have not necessarily been drawn to scale. For
example, the dimensions
12 of some of the elements in the figures may be emphasized relative to
other elements for
13 facilitating understanding of the various presently disclosed
embodiments. In addition, common,
14 but well-understood, elements that are useful or necessary in
commercially feasible embodiments
are often not depicted in order to facilitate a less obstructed view of the
various embodiments of
16 the present disclosure.
17
18 DETAILED DESCRIPTION OF THE NON-LIMITING EXEMPLARY EMBODIMENTS
19 [00083] Referring initially to Figure 1, a manufacturing
process is exemplified by a hot
runner system (100) that receives plastic in a molten state from an injection
nozzle (10).
21 [00084] The nozzle (10) is part of an injection machine that
includes a hopper (12), heater
22 (not shown), and feed screw (14) as is well known in the art. A control
(180) controls operation
23 of the machine to perform the required sequence of operations to produce
molded product. The
24 feed screw (14) delivers the plastic material under pressure to the
nozzle (10) from where it is
delivered through interconnected melt passages (16) to respective mold
cavities (141).
26 [00085] The cavities (141) are formed within mold plate
assemblies (140) that meet along
27 a common face. The mold plate assembly (140) includes a movable part
(140a), and fixed part
28 (140b) may be separated to allow access to the cavity (141) for ejection
of a molded article, and
29 are held closed during molding to contain the molten plastic.
[00086] The fixed part (140b) is connected to a cavity plate assembly (119)
that includes a
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1 manifold plate 120 to define the melt passages 16. A backup plate (121)
supports the cavity plate
2 assembly (119) to permit the cavity plate (119, 120) to be changed
readily without dismantling
3 the entire hot runner system.
4 [00087] Flow through the melt passages (16) in to the cavities
(141) is controlled by a gate
valve assembly (18) that is located in the backup plate (121) and extends
through the cavity plate
6 assembly (119) to the cavities (141). Alternatively, the gate valve
assembly may be incorporated
7 in the moveable part (140a) of the mold plate assembly (140) where the
configuration of the
8 molded article permits.
9 [00088] As shown in FIG. 1, the cavity plate assembly (119) is
configured for a multi
cavity gated arrangement with a gate valve assembly (18) associated with each
cavity (141).
11 [00089] The gate valve assembly (18) is shown in greater detail
in Figure 2 and includes a
12 melt flow modulating assembly (102) and an actuator assembly (101).
13 [00090] The modulating assembly (102) includes a manifold
bushing (132) that connects
14 through a manifold (131) located in a cavity of manifold plate (120) to
the melt passages (16).
The bushing (132) is connected to an injection nozzle (113) that includes a
melt flow channel
16 (112) to convey melt to a nozzle tip (114).
17 [00091] A backup pad (130) supports the bushing (132) against
axial displacement.
18 [00092] A valve pin (110) extends from the actuator assembly
(101) through the
19 modulating assembly (102) to control the melt flow from the nozzle tip
(114).
[00093] The manifold plate (120) is used to house the manifold (131) and to
distribute
21 molten plastic to each drop, as represented by an injection nozzle
(113). The injection nozzle
22 (113) is sealably attached to manifold bushing (132) via a seal off
(115) and detachably connects
23 the manifold bushing (132) with the injection nozzle (113).
24 [00094] Each the injection nozzles (113) is heated and the melt
flow channel (112)
extends therethrough from the rear end to the front end, and flowing into a
mold gate (160)
26 located at the interface of the mold plate (140) and the cavity plate
assembly (119). The mold
27 gate (160) is defined by a recess at the intersection of cavity plate
assembly (119) and mold plate
28 assembly (140) that may have a conical shape. The frontal end of the
drop is the nozzle tip (114)
29 and is a commonly replaceable part of the injection nozzle.
[00095] In the embodiments shown, the actuator (101) is illustrated as a
Lorentz force
31 actuator assembly (101) hereafter referred to as the LFAA assembly
(101). A Lorentz force
16
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1 actuator provides a linear force output proportional to a drive current
and thereby allows the
2 force generated by the actuator to be modulated by modulating the current
supplied.
3 [00096] The LFAA assembly (101) is generally placed in the
metal pocket machined in
4 the backup plate (121). The backup plate (121) is water-cooled, and the
LFAA assembly (101) is
in at least partial thermal communication with the backup plate (121).
Preferably, the LFAA
6 assembly (101) is thermally communicating with the backup plate (121) via
a partially threaded
7 connection or other type of connection means to permit thermal transfer.
8 [00097] By way of example, when cylindrically shaped, the LFAA
assembly (101) can be
9 placed in the pocket by partially or fully threaded connection that acts
as a thermal bridge and
improves cooling of the LFAA assembly (101). Alternatively, as shown in FIG.
6, a square-
11 shaped configuration of the LFAA assembly (101) can be installed with an
interference fit
12 generated by the operating temperature of the Lorentz force actuator
assembly (101) and the
13 backup plate (121), or by partially connecting the structure of the LFAA
assembly (101) with the
14 backup plate (121) by cover plates (252) extending across the pocket.
[00098] A major advantage of this type of the installation is that the LFAA
assembly (101)
16 is accessible from the back of the backup plate (121) but at the same
time, the installed LFAA
17 assemblies (101), being solid steel structure, strengthen the backup
plate (121) at the point where
18 the manifold backup pad (130) (FIG. 2 and 4) transfers the seal-off
forces generated by the melt
19 through the manifold bushing (132) from an injection nozzle seal off
interface (115).
[00099] With the recent advent of high energy density rare-earth magnets,
such as
21 Neodymium, Iron and Boron (Nd-Fe-B), and by modifying the electrical
coil (104) accordingly,
22 it is now possible to construct a quite compact, yet powerful, valve
gate actuator, such as the
23 LFAA assembly (101), that can under short duty cycle generate
substantial axial linear force. As
24 will be described below, this short duty cycle (pulsed) force generation
is used to position the
valve pin assembly (110) in a desired position along a melt flow path (112).
26 [000100] The LFAA assembly (101) has at least two distinct
assemblies: the magnetic
27 closed circuit assembly, and the electrical closed circuit assembly.
28 [000101] As shown in Figure 2, 3 and 6, the LFAA assembly (101)
has generally two
29 distinct mechanical assemblies acting as the magnetic closed circuit
assembly as well as
structural parts. A yoke magnetic assembly (105) is used to conduct magnetic
force, but also
31 provides a peripheral wall that bounds all parts of the LFAA assembly
(101). A core magnetic
17
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1 assembly (106) is located within the yoke magnetic assembly 105. An
annular air gap (116) is
2 located between the core magnetic assembly (106) and the yoke magnetic
assembly (105). An
3 electrical coil (104) is located in the air gap (116). The coil (104) is
wound on a bobbin (108)
4 that passes between the assemblies (105, 106) and has a base (145)
connected to one end of pin
(110), as described below. A yoke permanent magnet assembly (107) is placed
between the inner
6 surface of the yoke magnetic assembly (105) and the core magnetic
assembly (106), and thus
7 creates the magnetic flux.
8 [000102] The core magnetic assembly (106) and the yoke magnetic
assembly (105) are
9 preferably made from the electronic and magnetic alloys with high
magnetic permeability; the
higher the permeability, the better the magnetic performance of the magnetic
material. The core
11 magnetic assembly (106) presents a low magnetic resistance return path
for the magnetic
12 induction generated by the strong permanent magnets. These two parts are
operatively connected
13 to make up mainly uninterrupted closed magnetic circuit for the magnetic
induction from the
14 strong permanent magnets to pass perpendicularly through.
[000103] High saturation properties of the yoke magnetic assembly (105)
allow for higher
16 peak current in the coil, and therefore higher induction values before
saturation is reached. This
17 allows for the designs of the LFAA assembly (101) that will function
with greater force and
18 efficiency, but maintain a linear relationship between current and
generated force, according to
19 the Lorentz Force Law.
[000104] Some of the exemplary magnetic alloys suitable for high force
applications are:
21 Iron-Cobalt or Nickel¨Iron alloys with high magnetic permeability and
high flux density. Uses of
22 the 430FR type of the ferritic chromium steel alloys have demonstrated
good usability of the
23 application in the preferred embodiments.
24 [000105] It is highly desirable that the magnetic flux path of
the core magnetic assembly
(106) and the yoke magnetic assembly (105) is arranged so that the magnetic
flux generated by
26 the core magnetic assembly (106), or the yoke magnetic assembly (105),
or both the yoke
27 magnetic assembly (105) and the core magnetic assembly (106), which may
be permanent
28 magnets, are perpendicular to the electrical coil (104) within the air
gap (116), so that when an
29 externally applied current conducts through the electrical coil (104),
the electrical coil (104) will
be displaced axially along the axial magnetic air gap (116), and the amount of
the displacement
31 is linearly proportional to the applied current.
18
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1 [0001061 The yoke permanent magnet assembly (107) can be made
from any high quality
2 permanent magnets in the form of the magnet bars or elongated arcuate
segments, magnetized
3 through the thickness of the bars or segments, and suitably arranged to
cover the inner surface of
4 the yoke magnetic assembly (105) in a way to create a uniform unipolar
field in the axial
magnetic air gap (116). Preferably, a neodymium magnet (also known as NdFeB,
NIB, or Neo
6 magnet), is used in the preferred embodiments, and it is a strongest type
of rare-earth permanent
7 magnet. The neodymium magnet is a permanent magnet made from an alloy of
neodymium,
8 iron, and boron to form the Nd2Fe14B tetragonal crystalline structure
resistant to
9 demagnetization. General Motors and Sumitomo Special Metals developed
these neodymium
permanent magnets in 1982, but only recently are these magnets being made
readily available.
11 The neodymium magnet has replaced other types of magnets in the many
applications in modern
12 products that require strong permanent magnets. The most preferred type
is in the class N52,
13 specifically designed for demanding mechatronic applications and is
readily available. This type
14 of the permanent magnet is not susceptible to demagnetization due to
high current flow in the
electrical coil (104).
16 [000107] The permanent magnets (107) could also be placed on
the core magnetic assembly
17 (106). The permanent magnet assemblies could also be distributed between
the core magnetic
18 assembly (106) and the yoke permanent magnet assembly (107). These
assemblies can be
19 paralleled by using sets of the electrical coils in parallel, where
multiple coils would be acting on
the valve pin assembly (110) and thus increasing the axial force.
21 [000108] A high density magnetic field in the axial magnetic
air gap (116) is achieved by
22 the LFAA assembly (101). Other types of the magnetic structures like a
ring magnet with radial
23 magnetization can be used as long as a uniform, high density, unipolar
magnetic field is
24 produced within the axial magnetic air gap (116). In the preferred
structure of this embodiment,
as seen in the section of Figure 6 square bar magnets (117) are used to create
a uniform magnetic
26 field in the axial magnetic air gap (116) so that force due to a current
in the electrical coil (104)
27 is acting in the axial direction and is centered to drive the valve pin
assembly (110) axially along
28 the melt flow channel (112), and not imparting any side forces on the
valve pin assembly (110).
29 Bar magnets are used because no strong permanent magnet is available
today in the form of the
radially magnetized ring due to difficulty in manufacturing, but these may be
available for
31 consideration in a preferred embodiment in the future.
19
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1 [000109] Referring back to FIG. 2 and 3, an electrical coil
(104) is wound onto a coil
2 bobbin (108) that is positioned between the core magnetic assembly (106)
and the yoke magnetic
3 assembly (105), and is free to move along the axial magnetic air gap
(116). The electrical coil
4 (104) is preferably made from a highly conductive material like silver
and/or copper but an
aluminum coil may be used in some applications. The electrical coil (104) may
be wound on the
6 coil bobbin (108), which is made from plastic composites. A fine balance
is made between the
7 number of turns and the required axial force. Preference is given to
structures without a separate
8 coil bobbin (108) where the electrical coil (104) has a winding and coil
binder, or hardening
9 resins act together as self-supporting structures with solid integrity.
The electrical coil (104),
made from the rectangular profile wire, intertwines with the Kapton ribbons or
fibers and baked
11 in a high temperature resin, has the strength to support impulse forces
expected in the preferred
12 embodiment of this invention. An electrical coil can be made from
segmented individual turns,
13 preferably flat stamped, and only when assembled together are all the
turns (of the coil)
14 electrically interconnected. As well, the electrical coil (104), in form
of a "slinky", and/or made
from silver or pure copper material, can provide a distinct advantage in the
preferred
16 embodiments because the electrical coil (104) may provide a structure
without the coil bobbin
17 (108).
18 [000110] Among the materials suitable for application to
improve the structural integrity of
19 the electrical coil (104) is one of the DuPont (TRADEMARK) Kapton
(TRADEMARK) MT
polyimide film, a homogeneous film possessing three times the thermal
conductivity and cut-
21 through strength of the standard Kapton (TRADEMARK) HN film. This
polyimide film has
22 thermal conductivity properties that make it ideal for use in
dissipating and managing heat in
23 electronic assemblies, such as printed circuit boards and electrical
coils with high integrity
24 windings. It is anticipated that other materials and forms can be used
for making reliable coils
and, therefore, expand the applicability of this invention. High coil
integrity is required due to
26 high acceleration and deceleration rates of the electrical coil (104).
27 [000111] The material used in the electrical coil (104), in
some embodiments, could be
28 made from highly conductive soft magnetic alloys, to reduce the
effective air gap and to increase
29 the valve-pin closing force. However, the opening force may be nonlinear
and may be reduced
with the use of such a coil.
31 [000112] Also, highly conductive graphite used in the
electrical coil (104) when combined
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1 with oriented thermally-and-electrically-conductive nano-material
structures with high axial
2 integrity may be used to support the axial force, and may be an example
for some embodiments.
3 To modify coil performance, the air gap may be filled in with nano-
magnetic fluids.
4 [000113] It is likely that some applications may require an
electrical coil made over a
bobbin by techniques well known in printing with thin and/or thick film or
even by deposition of
6 the conductive coil material over layers of dielectric by spray
techniques also known in the
7 industry. Other embodiments may select to photo etch the coil patterns,
or even plate the coil
8 patterns but all of these and other techniques are anticipated by this
invention.
9 [000114] Flexible power leads connect the electrical coil (104)
to the control (180) that
provides a current pulse electrical signal. Suitable flat litz wire or flat
flexible ribbon can be used
11 for this application.
12 [000115] Referring again to FIG. 2, a mechanical pin locking
assembly (126) is installed in
13 the bottom portion of the yoke magnetic assembly (105). As illustrated
more fully in FIGS. 7 ¨ 9,
14 a pin-locking slide (122) is made to move laterally along lock slide
guides (125). As can be seen
in Figures 7 - 9, the assembly (126) includes a pair of jaws 502 that are
slidably mounted on the
16 guides (125). Each of the jaws (502) has a recess (503) configured to
conform to the outer
17 surface of the sliding pin (110). The opposed faces of the jaws (502)
have magnetic holding
18 springs (501) embedded therein to provide an attractive force in the
direction of closing around
19 the valve pin assembly (110). As can be seen in Figure 2, the pin (110)
includes surface
formations such as a lock thread 330, intended to be engaged by the jaws (502)
and prevent the
21 valve pin assembly (110) from moving axially when operating power from
the LFAA assembly
22 (101) is removed within the cycle of the molding of the plastics parts.
The axial length of the
23 surface formations is equal to an approximate length of the total axial
stroke of the valve pin
24 assembly (110).
[000116] A pin-locking coil (123) is placed inside the yoke magnetic
assembly (105) just
26 below the pin-locking slide (122). A set of pin locking permanent
magnets (124) is carried by
27 each of the jaws (502) so as to be horizontally disposed above the coil
(123). Energization of the
28 coil (123) causes the magnets (124) to apply a force to separate the
jaws (502) and thereby
29 release the valve pin assembly (110) to allow axial movement when the
LFAA assembly (101) is
energized. In the arrangement shown, it is advantageous to install the pin-
locking coil (123)
31 below the pin-locking slide (122) to facilitate assembly and improve
cooling of the pin-locking
21
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1 coil (123).
2 [000117] As noted above, the valve pin assembly (110) has a
surface formation indicated at
3 330 that provides a locking feature. The pin-locking feature (330) is
formed as a thread and is
4 positioned some distance from the distal end of the valve pin assembly
(110), and is located in
the axial position of the mechanical pin locking assembly (126). In the
preferred embodiment,
6 the pin-locking feature (330) is operatively engaged by the jaws of the
lock slide guides (125) to
7 prevent any axial movement of the valve pin assembly (110) when the LFAA
assembly (101) is
8 de-energized. In this way, the pin-locking feature (144) operatively
arrests motion of the valve
9 pin assembly (110) during a gate open condition or a gate closed
condition within a molding
operation.
11 [000118] Because of the short duration of the axial valve pin
movement (less than 35 ms or
12 milliseconds), a relatively high current pulse can be used and not
overheat the coil windings.
13 [000119] An active short duty cycle of the valve pin assembly
(110) allows for long power
14 off time with a separate instance of a mechanical pin locking assembly
(126) as will be discussed
below.
16 [000120] The pin-locking coil (123) and the electrical coil
(104) can be energized in a
17 required sequence determined by the mold sequence controller (180), or
can be energized at the
18 same time to open the pin-locking slide (122) and move the valve pin
assembly (110) axially.
19 [000121] The control of the coils (104,123) is provided by the
electronic valve gate drive
controller (400) that is part of the controller (180) and is shown as
simplified block diagram in
21 Figure 10.
22 [000122] An energy storage capacitor (405) is provided and is
capable of storing and
23 discharging, on demand, a certain calibrated amount of electrical energy
into the electrical coil
24 (104) of FIG. 1. The energy storage capacitor (405) is operatively
connected to conduct an
electrical charge via the electrical wire supply (406) and the electrical wire
return line (407) to
26 the electronic switch Q1 (410) and the electronic switch Q3 (430). The
electronic switch Q1
27 (410) and the electronic switch Q3 (430) operatively control the
directional flow of the electrical
28 current through the actuator coil (403) of the LFAA assembly (401). A
second set of electronic
29 switches Q2 (420) and Q4 (440) facilitates the flow of the electrical
current through the actuator
coil (403) by being operatively switched on and off in a precisely determined
order and with
31 particular timing based on the input from the control computer.
22
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1 [000123] The electronic switch Q1 (410) and the electronic
switch Q2 (420) cannot be in an
2 operatively ON state at the same time; this will cause a short circuit to
the energy storage
3 capacitor (405). Also, the electronic switch Q3 (430) and the electronic
switch Q4 (440) cannot
4 be closed in the ON state at the same time.
[000124] A duty cycle controller Qo (402) is provided to optimize and
control the level of
6 charge in the energy storage capacitor (405). The duty cycle controller
Qo (402) charges the
7 energy storage capacitor (405) via the electrical conductors that are
suitably connected from the
8 energy storage capacitor (405) to the duty cycle controller Qo (402). The
duty cycle controller
9 Qo (402) operatively charges the energy storage capacitor (405) in a
predetermined and
controlled sequence, operatively based and referenced to the operational cycle
of the molding
11 apparatus. This is done in a way that the LFAA assembly (101) will be
energized only when
12 axial motion of the valve pin assembly (110) is requested, with a
particularly controlled duty
13 cycle, and this arrangement prevents damage to the LFAA coil assembly
(104) due to
14 overheating temperature of the actuator coil (403) due to the high
current. Recharging the energy
storage capacitor (405) is required after each single axial movement of the
valve pin assembly
16 (110) to ensure accurate capacitor charge and improve accuracy in the
positioning of the valve
17 pin assembly (110). The LFAA assembly (101) is intended to operate only
with a limited duty
18 cycle. In the preferred embodiment, the duty cycle should not exceed
25%. In another
19 embodiment, process demand for a short cooling time duty cycle may be
less than 10%. The
axial move time is preferably less than 10 ms (milliseconds).
21 [000125] The duty cycle indicates both how often the LFAA
assembly (101) will operate
22 and how much time there is between operations. Because the power lost to
inefficiency
23 dissipates as heat, the actuator component with the lowest allowable
temperature, usually the
24 actuator coil (104), establishes the duty-cycle limit for the complete
instance of the LFAA
assembly (101).
26 [000126] The duty cycle is relatively easy to determine if the
LFAA assembly (101) is used
27 on a molding machine, since the repeatable cycle of the molding machine
has intervals when the
28 LFAA assembly (101) is demanded to be energized (during valve closing or
opening only), and
29 de-energized (during mold cooling and part handling time). The provision
of the pin locking
assembly 126 enables a very short electrical actuator power ON time as there
is no longer a need
31 to maintain power to the actuator coil (104) once the valve gate (110)
is closed or the valve gate
23
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1 (160) is opened. The actuator coil (104), is ON only during the axial
translation of the valve pin
2 assembly (110) from the first preferred position (usually open), to the
second preferred position
3 (usually closed). During all other process times, the LFAA assembly (101)
is locked into
4 preferred positions with no demand for power. The pin-locking stroke of
the jaws (122) is very
short, usually only as much as is required to maintain the arrest position of
the valve pin
6 assembly (110). It is anticipated that the opening time of the pin
locking assembly (126) is
7 scheduled before the valve pin assembly (110) is directed to move,
although some overlapping in
8 sequence may be conceivable.
9 [000127] Operating on the edge of the molding's power curves,
i.e. shortest possible mold
cycle time, might incur the risk of the LFAA assembly (101) running hot.
However, the generous
11 cooling time available for solidification of the plastic in the mold
enables heat in the coil (104) to
12 be dissipated. In most applications, molding PET or other food and
medical moldings, where the
13 duty cycle is 5% or less, the LFAA assembly (101) can run to the limit
of its power curves, once
14 the backup plate cooling is effective. The duty cycle of the electrical
locking coil (123) has no
limit on duty cycle because the coil impedance limits the excessively high
current flow to cause
16 any overheating. The longer part of the operational cycle of the valve
pin assembly (110) is
17 normally maintained by the permanent magnets, and all coils are without
power and are self-
18 cooled and are getting ready for the next movement cycle of short
duration.
19 [000128] Referring back to FIG. 10, the actuator axial force is
generated upon a request
from the controller (180) for the energy storage capacitor (405) to discharge.
The controller
21 (180) implements computer software instructions to effect control (as is
well known to those
22 skilled in the art of computers) of the gate drive controller (400). The
controller (180) may
23 request closure of the electronic switch Q1 (410) and the electronic
switch Q4 (440). The energy
24 storage capacitor (405) is operatively short-circuited by the electronic
switch Q1 (410) and the
electronic switch Q4 (440) and connected with the electrical wire supply (406)
and the electrical
26 wire return line (407), will discharge a certain calibrated amount of
electrical charge to move the
27 valve pin assembly (110) of FIG. 1 to the preferred position, be it in
the open direction or the
28 closed direction. The amount of charge in the energy storage capacitor
is selectable by the
29 operator, via the valve gate controller logic and the operator interface
screen (182). At the same
time, the coil (123) is energized to release the jaws (502).
31 [000129] Once a high current flows through the actuator coil
(403), an axial force in the
24
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1 direction of the air gap (116) will push the valve pin assembly (110)
axially to the desired
2 position. Once the position is reached with a slow speed (i.e., below 5
to 25 mm/s (millimeters
3 per second)). As shown in FIG. 11, the current pulse, shown by the dark
line, progressively
4 increases and then decreases over the duration of the pulse. The
corresponding force generated is
shown in the lighter line and follows the profile of the pulse. The force
applied to the pin (110)
6 initially accelerates the pin (110), causing it to move toward the closed
position. The acceleration
7 is opposed by the inertia of the pin (110) and by the resistance of the
motion of the pin (110)
8 through the plastic in the melt flow channel (112). As the current is
reduced, the force generated
9 by the actuator (103) is correspondingly reduced and the velocity of the
pin (110) progressively
reduces, due to the resistance of the plastic melt, so that, as the pin
attains the closed position, its
11 velocity approaches zero.
12 [000130] The shape of the pulse is selected to provide an
optimum velocity profile in both
13 the closing and opening direction. It will be appreciated that a more
aggressive declaration can
14 be obtained by reversing the direction of current flow in the coil 104
during movement, and that
the pulse shape may be different between opening and closing directions.
16 [000131] Upon attainment of the open and closed position, the
pin locking assembly (126)
17 will de-energize and lock the valve pin assembly (110) in the targeted
preferred position. No
18 power is applied, nor is required, for the locking coil to hold the
valve pin assembly (110) in the
19 arrested position. In a preferred embodiment of this invention, the
force of permanent magnets
(501) locks the valve pin assembly (110). When the valve pin assembly (110) is
locked, the
21 electronic switch Q1 (410) and the electronic switch Q4 (440) are open
(OFF).
22 [000132] Next, the duty cycle controller Qo (402) requests re-
charging of the energy
23 storage capacitor (405) from the suitable bus voltage power supply (480)
according to demanded
24 charge levels.
[000133] Once charged back to a demanded energy level, the request for
movement of the
26 pin (110) from the closed position to the open position may be initiated
by closing the electronic
27 switch Q3 (430) and the electronic switch Q2 (420). The locking coil is
energized to release the
28 latch and permit movement of the pin (110). The controller (402)
provides a current pulse to
29 move the pin (110) to the closed position and decelerate it at the
closed position. The latch is
released to hold the pin (110).
31 [000134] Since the transition time of the coil and energizing
coil (123) in the modem power
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1 switching device is a fraction of a microsecond, modulation and
intervention in the shape of the
2 energy pulse is possible to ensure formation of an accurate and most
desirable pulse shape.
3 [000135] Total stroke time for the axial distance of about 7 to
about 9 mm (millimeters) is
4 demonstrated to be about 5 to about 10 milliseconds, and is largely
dependent on the size of the
coil assembly of the LFAA assembly (101).
6 [000136] The control pin movement (110) by coil (104) and the
high forces available make
7 it possible, in the preferred embodiment, to profile the end of the
stroke to best meet the
8 demanding quality of the gate vestige without using complex servo
controlled positioning based
9 on the position feedback device.
[000137] The nature and the application of the preferred embodiment for an
injection mold
11 of the hot runner application allows for good vestige of the molded
parts to be examined by the
12 operator for each cycle of the machine during setup and pre-run
verification, and suitable
13 correction to the inputs can be made during the setup process to modify
the pulse shape and the
14 closed pin position. As shown in Figure 11, adjusting the pulse shape at
each iteration allows
incremental changes in the position of the pin (110) until the optimum
position is attained. Once
16 attained, the shape may be saved in the controller (402) for repetitive
molding operations. If
17 inspection shows deterioration of the vestige, an adjustment can be made
by the operator through
18 the interface (182).
19 [000138] The primary parameter for controlling movement of the
pin (110) is the current
supplied from the capacitor Q5. The rate of current is 50 to 100 A/millisecond
(amperes per
21 millisecond), and the limit for the peak current is set by comparing the
current feedback from a
22 current feedback device (455) at the electronic valve gate drive
controller (400) and the set peak
23 current. The set peak current is an operator-controlled set point from
the operator machine
24 interface computer (182) and is based on the preferred axial position
for the valve pin assembly
(110). This input, the capacitor charge, may be generated by the operator
based on the part
26 quality observed or it may be automatically selected from a molding
parameter set data matrix.
27 The log matrix in the form of the lookup table can be implemented to
compare the vestige
28 quality with the valve pin position, as attained using a selected
current pulse shape, and use this
29 information as a teaching tool for an optimum new position set point of
the valve pin assembly
(110). Controlling the current through the electrical coil based on a certain
set value may be
31 accomplished by implementing the hysteretic control model where the
hysteretic control circuit
26
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1 in the valve gate controller turns the electronic switch Q1 (410) or the
electronic switch Q3 (430)
2 OFF when the current amplitude reaches the upper set point value, and
then turns the electronic
3 switches back ON when it reaches the preset lower values amplitude point.
This control scheme
4 may be used in a standalone manner to improve valve pin positioning and
therefore improve the
part vestige, or in combination with other methods like iterative learning
control (ILC) as
6 discussed more fully below. It will be appreciated that the control 400
will incorporate memory
7 buffers, set point comparators, timers and devices like digital
microprocessors in the valve gate
8 driver circuit of FIG. 10, in various known ways, and packaged in the
electronic valve gate drive
9 controller (400) suitably built to operatively interface with the
operator input device and a
molding machine computer to logically control the vestige quality by
accurately positioning each
11 instance of the valve pin assembly (110). Control monitoring of the
electrical current pulse by
12 current-sensing power MOSFETs provide a highly effective way of
measuring load current
13 through the electrical coil (104) in FIG. 1 of the LFAA assembly (101).
14 [000139] The current plot of the current is compared to the
preferred plot to reduce
positioning error for the valve pin position. Valve pin positioning accuracy
of plus or minus five
16 micrometers can be achieved by implementation of-Iterative Learning
Control (ILC) in valve pin
17 positioning in the hot runner systems or injection molding, and can
improve valve pin
18 positioning.
19 [000140] The use of ILC is shown schematically in Figure 15 and
is a method of improving
control parameters for systems that function in a repetitive manner. The
repetition involved in
21 valve positioning provides typical conditions to use iterative learning
techniques. There is room
22 for significant positional accuracy improvement and, therefore,
improvement in the vestige
23 quality of the moldings when using the Lorentz force actuator assembly
(101) in FIG. 2. ILC can
24 be implemented in any system that is required to perform the same action
for millions of cycles
with high precision. Each repetition or cycle allows the system to improve
tracking accuracy,
26 gradually learning the required input needed to track the reference to a
small margin of error.
27 The learning process uses information from previous repetitions to
improve the control signal,
28 ultimately enabling a suitable control action to be found.
29 [000141] Through iterative learning perfect tracking of the
valve pin position can be
achieved. Perfect tracking is represented by the monotonic convergence of the
mathematical
31 model. Iteration allows for monotonic convergence to achieve more
accurate positional accuracy
27
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1 of the valve pin assembly (110) in a molding application of the hot
runners. Experiments
2 demonstrate convergence within 5 to 10 pin cycles. After achieving
convergence the valve pin
3 assembly (110) will be able to operate in a stable state.
4 [000142] To improve the speed of convergence fuzzy logic can be
implemented as part of
the ILC. Improved parameters for the ILC algorithms can be attained through
the use of external
6 sensor feedback. These sensors could include; x-ray sensors,
electromagnetic sensors, or other
7 appropriate sensors that would provide meaningful information. The ILC
algorithms and fuzzy
8 logic parameters can be updated in real-time or through analysis of
previously collected and
9 stored data, as will be described more fully below with respect to an
alternative embodiment of
molding apparatus. In the present embodiment the result of the combination of
real-time dynamic
11 parameter modification is a self-tuning system that will have automated
tracking accuracy of the
12 open loop valve pin positioning. The fuzzy system is used to precisely
position the valve pin tip
13 of FIG. 3 without installing any physical motion or position feedback
device or structure within
14 the valve pin stroke. Turning back to FIG. 10, the inherent
characteristic of the actuator coil
(403) of the LFAA assembly (104) to slow down in the magnetic field when coil
terminals are
16 short-circuited can be operatively used to slow down the axial movement
of the coil of the LFAA
17 assembly (104). This can be accomplished by opening the electronic
switch Q2 (420) and the
18 electronic switch Q4 (440), and closing the electronic switch Ql (410)
and the electronic switch
19 Q3 (430). The flyback diodes (451, 452, 453, 454) functionally support
the switching operation
of the electronic valve gate drive controller (400).
21 [000143] The operation of the gate valve assembly will now be
described, assuming
22 initially that the pin (110) is held in an open, i.e. retracted position
by the jaws 502 engaging a
23 lower portion of the screw thread (144). The coils (104, 123) are de-
energized and the jaws held
24 closed by action of the magnets (501). The first step in the operation
of the LFAA assembly
(101) involves application of the suitable electrical current pulse through
the electrical coil (104)
26 (FIG. 2), and at the same time the application of the voltage to the pin-
locking coil (123). The
27 pin-locking coil (123) reacts with the pin locking permanent magnets
(124) and separates the
28 jaws to unlock the valve pin assembly (110). The current applied to the
electrical coil (104)
29 operatively reacts to a magnetic field from the permanent magnets,
generates a force
perpendicular to the current flow through the electrical coil (104), i.e. in
the axial direction of the
31 pin 110. Therefore accelerates the valve pin assembly (110) in the
direction of the actuator force
28
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1 pushing downward to close the mold gate as per FIG. 1.
2 [000144] The next step in the operation of the LFAA assembly
(101) is to decelerate the
3 valve pin assembly (110) to the gate closing point, but not to impact the
mold gate (160) and to
4 cause any damage by hard stops. The electronic valve gate drive
controller (400) modulates the
current pulse to follow the shape of the current profile in the controller
memory predetermined
6 by experiments for the type of the product that is being molded. The
electronic valve gate drive
7 controller (400) follows a shape of the current signal already stored in
the controller memory
8 within the proportional hysteresis bandwidth and based on the current
feedback from the
9 electronic drive controller, and determines optimal deceleration slope of
the current pulse. The
electronic valve gate drive controller (400) has the ability to brake by
shorting the electrical coil
11 (104) by switching the appropriate electronic switches in FIG. 10
(specifically, the electronic
12 switch Q1 (410) and the electronic switch Q3 (430) are set OFF, and the
electronic switch Q2
13 (420) and the electronic switch Q4 (440) are set ON) to accurately stop
the valve pin assembly
14 (110) and "soft land" the valve pin assembly (110) into a gate closed
position or any preferred
position within the axial stroke of the LFAA assembly (101).
16 [000145] When it is anticipated that the valve pin assembly
(110) has arrived at the
17 preferred position, the pin-locking coil (123) de-energizes, and the
jaws (502) moved under the
18 influence of the magnets (501) to operatively engage the threaded
portion (144) (a high friction
19 area) of the valve pin assembly (110) by the attractive force of the
magnetic holding springs
(501) in FIG. 5. Any residual motion of the valve pin assembly (110) is
arrested. In this
21 condition, no current is required to hold the valve pin assembly (110)
in a gate-closed position,
22 as shown in FIG. 5.
23 [000146] In this position, the valve pin assembly (110) extends
through the mold gate (160)
24 and blocks the flow of the molding material through the mold gate (160)
(or the mold gate
channel).
26 [000147] The next step involves cooling of the moldings in the
mold cavity (141), ejecting
27 the molded part from the mold cavity (141) by opening mold (140), and
closing the injection
28 mold. The cooling process of plastic parts takes time. Plastic
solidification and part removal from
29 the mold cavity (141) is at best five to ten times longer than the time
to inject molten material
into the mold. Thus, there is a substantial amount of time where the valve pin
assembly (110) is
31 resting in a closed position and is de-energized. The mold core portion
(140a) and the mold
29
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1 cavity portion (140b) are movable relative to each other, and when the
part has solidified, the
2 mold is opened and the part ejected. After ejection, the mold core
portion (140a) and the mold
3 cavity portion (140b) are positioned to abut each other so that the mold
cavity (141) is formed,
4 and the resin or the molding material may again be injected into the mold
cavity (141).
[000148] The controller (400) thus energizes coil (104) to retract the pin
(110) and the coil
6 (123) to release the jaws (502). The pin (110) is retracted and braked by
the current pulse from
7 the controller (400) and the jaws again engaged to hold the pin (110) in
the open position.
8 [000149] Thus the mold gate (160) is opened by moving the valve
pin assembly (110)
9 upward in the preferred position within the axial stroke of the valve pin
assembly (110). The
valve pin assembly (110) is designed to open and/or increase the cross-
sectional area of the mold
11 gate (160) with the coil bobbin (108) and the pin-locking coil (123)
energized, to allow the flow
12 of molten resin into the mold cavity (141).
13 [000150] In some embodiments, the axial stroke can be 8 to10 mm
(millimeters) which is
14 deemed sufficient to avoid adverse effect of the annular flow for most
medical moldings and the
molding PET preforms.
16 [000151] The LFAA assembly (101) exploits the inherent
characteristic of the injection
17 molding process and the hot-runner system (100), where the plastic
cooling takes a much longer
18 time in the process than the injection of the polymer the molding
material) into the mold cavity
19 (141). Therefore, it is possible to operate the LFAA assembly (101) in a
condition of significant
current pulse overdrive, limited only by the thermal limitations of the LFAA
assembly (101).
21 The method for modulating melt flow within the hot-runner system is
obtained by generating a
22 significant axial electrical force for a very short time lasting 5 to 20
ms (milliseconds). In a
23 preferred embodiment, the valve pin assembly (110) moves along the melt
flow channel (112) by
24 the LFAA assembly (101) when powered from the current pulse power supply
(480). Thus,
positioning is accomplished by controlling the pulse current amplitude as a
function of time. This
26 allows the actuator operation only during axial movement of the
electrical coil (104), leading to
27 reduced operational time within the thermal limitation of the electrical
coil (104). During the
28 cooling part of the cycle, the electrical coil (104) is de-energized but
locked by the magnetic
29 holding springs (501) of the permanent magnet. The magnetic holding
springs (501) rely on
magnetic attraction or repulsion to control the force of the locking
mechanism. The magnetic
31 holding springs (501) have a significant life and are a very consistent
and reliable means of
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1 creating a spring force.
2 [000152] It will be noted that no mechanical spring is utilized
in the preferred embodiment
3 shown in Figures 2 through 10.
4 [000153] Experimentation with and measurements of the
embodiments shown
demonstrated operational efficiency with the duty cycle of the LFAA assembly
(101) up to 25%
6 for an application involving the packaging molding processes, like PET
preforms, closures and
7 coffee cap multi-material moldings.
8 [000154] An alternative embodiment of a Lorentz force actuator
assembly is shown in
9 Figure 12, in which like components are identified by like reference
numerals with a suffix "a"
for clarity. In the embodiment of FIG. 12, provision is made for enhanced
guidance of the pin
11 assembly (110a). Referring therefore to FIG. 12, a Lorentz force
actuator assembly (101a) is
12 operatively connected to a valve pin assembly (110a) having a yoke
magnetic conductor (105a)
13 and a core magnetic conductor (106a). The core magnetic conductor (106a)
and the yoke
14 magnetic conductor (105a) operatively support permanent magnets facing
an axial air gap
(116a). A yoke permanent magnet assembly and a core permanent magnet assembly
(209) are
16 each facing an electrical coil wound as a self-supporting structure or
being structurally supported
17 by the coil bobbin (108a). To close the magnetic circuit, a base plate
magnetic conductor (206) is
18 provided. The electrical coil (104a), designed to conduct a high current
pulse, is placed on the
19 coil bobbin (108a) that is designed to operatively move along the air
gap (116a) in the axial
direction under an electrical force acting in concert with a permanent magnet
field in the air gap
21 (116a), thus creating suitable a condition to generate an electrical
force that is perpendicular to
22 the coil current flow and, by definition, in a direction according to
polarity of the current pulse.
23 This force is directly and linearly proportional to the current
amplitude and increases in the valve
24 pin closing direction.
[000155] A pin locking assembly (126a) is positioned at the distal end of a
valve pin
26 retainer (240), and the pin locking assembly (126a) operatively arrests
any movement of the
27 valve pin assembly (110a) when the electrical locking coil (123a) is de-
energized. There is a
28 locking slides air gap (220) between the electrical locking coil (123)
and the locking magnet
29 (124a). The pin locking jaws (502a) are guided by the locking slide
bearings (125a). When the
electrical locking coil (123a) de-energizes, the permanent magnet assembly
attracts the two jaws
31 toward each other to close and engage the pin locking rib (230) formed
on the pin 110a and to
31
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1 arrest any motion of the valve pin assembly (110a). The pin locking
assembly (126a) can be
2 placed along a length of the valve pin assembly (110a), as well as
attached to any axially moving
3 part. Magnetic holding springs as shown in Figure 5 are used for
attracting the pin locking jaws
4 (502a) around the valve pin assembly (110a).
[000156] Referring now to FIG. 12, once placed in the backup plate (121a),
an actuator
6 cover plate (252) is installed. The actuator cover plate (252) is also
preferably manufactured
7 from a soft magnetic material. The actuator cover plate (252) has an
opening 253 where a valve
8 pin retainer (254) can be guided during the axial movements of the valve
pin assembly (110a).
9 This opening can also be used as an access for accurate pin height
adjustments. Additionally, the
electrical coil bobbin guides (250) are provided to prevent potential side
loading on the valve pin
11 assembly (110a) and improve axial motion of the electrical coil (104a).
Pin upper position
12 holding magnets (251) are provided for some embodiments to hold the pin
(110a) in an open
13 position.
14 [000157] To ensure accurate and precise alignment for the valve
pin assembly (110a) and
the electrical coil (104a) generating the axial motion, additional guides
(250) are incorporated in
16 the bobbin (108a).
17 [000158] Rib (230) is formed as a conical portion of
progressively enlarged diameter which
18 thereby provides a radial abutment surface facing the actuator (101a). A
number of such ribs
19 may be provided a discreet location on the pin (110a) to provide
multiple stable positions.
[000159] In use, the jaws (502a) operatively engage the valve pin assembly
(110a) through
21 the pin locking rib (230) and are separated as the pin (110) moves
toward the closed position by
22 the electrical coil (104a). The coil (123a) I used to separate the jaws
(502a) to release the pin
23 (110a) to move to the open position. The electrical locking coil (123a)
is placed below a locking
24 magnet to ensure better coil cooling by the backup plate (121 from FIG.
1). The locking magnet
may be a permanent magnet.
26 [000160] In the embodiment of Figure 12 the pin locking
assembly (126a) operatively
27 engages the valve pin assembly (110a) against the pin locking rib (230)
in a pin closed position.
28 When the valve pin assembly (110a) is in a fully opened position, the
pin upper position holding
29 magnets (251) are used as an alternative to bi-directional locking.
[000161] A further embodiment is shown in FIG. 13 where like elements are
identified with
31 like reference numerals with a suffix "b" for clarity. Referring now to
the example of FIG. 13,
32
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CA 02931412 2016-05-27
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1 there is a valve pin retainer (254b) shown at the distal end of the valve
pin assembly (110b) with
2 a suitably arranged structure for precise adjustments of the valve pin
protrusion, in a form of a
3 valve pin height adjustment assembly (651). A valve pin height adjustment
assembly (651)
4 comprises a valve pin guide bushing (604) and a fine-tuning pin indicator
providing auditory and
visual measure of adjustments in certain "clicks". Each incremental position
represents
6 selectively 5 to 25 micrometers of linear movement of the valve pin
assembly (110b). The
7 audible "clicks" are generated by the valve pin sound feedback lock (601)
in the valve pin
8 adjusting assembly (600) made with the permanent magnet spring (602)
shown in FIG. 6. This is
9 a technical structure that will benefit fast service and maintenance of
the valve pin assembly
(603). A slot (606) is a slot for inserting an adjusting tool for tensioning
the magnetic holding
11 springs (501).
12 [000162] As an alternative a method for arresting or locking
the axial movement of the
13 valve pin assembly (110), a rotary arrangement using rotary locking
slides may be used. This can
14 include a rotating lock using a collet assembly that can effectively
maintain the valve pin
assembly (110) at rest when the power to the LFAA assembly (101) is turned
off.
16 [000163] As a further alternative, a method for arresting or
locking the axial movement of
17 the valve pin assembly (110) can be done by utilizing principles of a
smart material that changes
18 the volume or the linear dimension by the application of the electrical
signal. Some materials of
19 this nature are crystals like quartz, often used to generate and receive
a signal. Other well-known
materials sensitive to a voltage charge are lead zirconate-titanate or well
known as PZT. The
21 science and art of smart materials are replete with materials that can
change size by the
22 application of an electrical charge. Material properties like
electrostriction, or crystal material
23 matrix reconfiguration, or molecular or particular realignment, are some
of the properties of
24 materials like Nitinol, electro rheological fluids or nano-ferofluides,
etc.
[000164] Since various aspects and structures are possible to use to arrest
the movement of
26 the valve pin assembly (110), one example of the preferred arrangement
is mentioned, where the
27 valve pin assembly (110) operatively incorporates an electrically-charge
sensitive smart material
28 that contracts radially when the electrical signal is applied to
opposite axial sides of the smart
29 material (in the form of an insert) to maintain easier axial motion of
the valve pin assembly
(110). When the signal is not present, the smart material recovers in the
normal condition of zero
31 energy state where the majority diameter is larger than the average
diameter of the valve pin
33
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CA 02931412 2016-05-27
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1 assembly (110). This may create a friction force against a tightly fitted
valve pin assembly (110),
2 and the surrounding coaxial structure may arrest any motion of the valve
pin assembly (110).
3 This is a simple and effective way to arrest the axial motion of the
valve pin assembly (110) in
4 situations where the mechanical perpendicular obstruction is not
desirable for whatever reason.
Opposite arrangements, where the contracting ring inner diameter may arrest
the movement of
6 the valve pin assembly (110) in position is envisioned.
7 [000165] The above description of the arrangement and operation
of a molding system and
8 apparatus has demonstrated the collection of data and the use of that
data to the control of the
9 injection apparatus to control the quality of the molded component. While
this approach is
possible, it requires a very skilled level of people involved with setup of
the machine and
11 process. Firstly, the person interpreting images of the gate vestige or
complete part(s) must be an
12 expert in analyses of the x-ray imagery or IR imagery or other very
specialized qualitative
13 inspection method, and then the same person or different must be expert
in process adjustments
14 and interpretation of the inspection findings. The second person must
take the quality inspected
part and convert the knowledge about the actual part into a set of relevant
parameters that can be
16 applied to input of the machine to hopefully produce new part with
better and more exact quality
17 characteristics.
18 [000166] To mitigate these challenges, a further embodiment of
a molding system and its
19 control system is shown in Figures 16 to 20. In that embodiment, the
manufacturing process is
exemplified as a metal casting machine, such as is used in the production of
"alloy" wheels,
21 although the general applicability to other processes, particularly the
molding of other parts,
22 including plastic parts will be appreciated.
23 [000167] In general terms, the molding machine will produce a
part and transfer it into an
24 inspection system (IS) with at least one part inspection sensor from
those well known in the state
of the art, like X-ray, UV, IR or visible light. The inspection system IS will
look into, for
26 example, gate vestige of the molded article, which is related to the pin
position, and create an
27 image or set of digital data that characterizes this specific part
vestige quality. Assuming that,
28 when compared to drawing digital data from the design, the part is good
and acceptable, the
29 process will automatically transfer serialized set of digital data
created by the inspection system
and store it in the Good Part Data Set block (GPDS) shown in Fig. 16. At the
next step this
31 GPDS data will also be shared with the KSDAP (Knowledge System for Data
Analyzing and
34
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CA 02931412 2016-05-27
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1 Prediction) which function block contains all mathematical algorithms for
retrieving necessary
2 information to comparing data and running algorithms to determine if a
change to the process is
3 required. Since in this step no changes are warranted because the process
has generated good part
4 vestige, information about part will be transferred into Parameter
Generator (PG) to create new
relevant set of inputs that do not change the process at this moment. The
machine continues to
6 produce parts with the valve stem positioning as before where the
iterative learning controls
7 maintains status. The process continues, and inspection continues, until
the inspection system
8 detects variations in the gate vestige. The gate vestige may be evaluated
for example by using a
9 visible image of good vestige as an image template and correlating this
image with proper valve
stem position. Subsequent images are then compared to the image template and
the information
11 transferred to the Parameter Generator (template matching).
12 [000168] If inspection shows the vestige is unacceptable and
part is no longer good quality,
13 information about this part is transferred in to Bad Part Data Set base
(BPDS). The KSDAP
14 takes BPDS and compares it to information from GPDS and creates set of
parameters indicating
need to adjust the valve stem to improve vestige. This information is now
transferred to PG to
16 generate new set of inputs for the machine (of any kind, molding,
casting, CNC, additive mfg. or
17 valve positioning) to iteratively adjust, in particular example, stem
position and injection
18 pressure. After Production system (PS) makes new part, and IS inspect
the new part, it was found
19 that next part is good and cycle continues.
[000169] This arrangement may of course be applied to inspection of any
produced part
21 and use of the data from the inspection, compare it to data from data
bases of good and/or bad
22 parts and compare this to original data set for the design model data
set (DMDS) and determine
23 in the KSDAP how to increment the process parameters to create new set
of inputs to the
24 machine that will produce next good part and continually do that for the
production run, until
interrupted by the operator locally at the machine or remotely stopped by the
intelligent system
26 operator.
27 [000170] A more detailed example of the application of the
invention is its use in the die-
28 casting of an alloy wheel rim shown in the Fig 19. A production system
PS represents the
29 typical well known die-casting machine. This machine may be any machine
according to
standard state of the art, high pressure, low pressure, cold chamber, hot
chamber, or
31 thixomolding injection molding machine as well as MAXIcastTM semi-solid
casting machine as
22928473.1

1 described in US patent application US 2015/0266086.
2 In the embodiment shown in Fig. 19, the material is supplied to
the mold
3 cavity from a solid feedstock which is melted to slurry and processed to
the runner system
4 associated with the mold used to produce the product. The production
system PS has the controls
necessary to adjust the operating parameters of the die casting machine as
described above,
6 including an iterative learning control to adjust operation of the valve.
Once cast, the die cast
7 wheels are ejected from the production system PS and transferred to an
inspection system IS.
8 [000171] The Inspection system(s) accepts the cast parts and
proceeds with automatic
9 inspection according to one of the known or customized testing and
inspection protocols. The
items are inspected for critical dimension or other critical features of the
part. If for example,
11 linear dimension of the item is critical for quality, the linear
dimension of the parts is measured
12 and digitized preferably by electromagnetic measurements like laser. If
however surface
13 appearance is critical to quality feature measurement for surface
irregularities with one of the
14 well-known methods is utilized. Usually, the surface profile and
roughness of a machined work
piece are two of the most important product quality characteristics and in
most cases a technical
16 requirement for mechanical products. Achieving the desired surface
quality of the finished
17 castings is of great importance for the functional behavior of a part.
The process-dependent
18 nature of the surface quality mechanism along with the numerous
uncontrollable factors that
19 influence pertinent phenomena, make it important to implement an
accurate prediction model.
Final improvements in prediction of surface profile using modern neural
network may be used to
21 ensure desired high quality surface of the part.
22 [000172] It is also necessary to inspect parts for internal
structural abnormalities like
23 discontinuation or large gas inclusions that may under operating
conditions create stress
24 concentration or will prevent heat treatment of the casted part in a
subsequent step. Ultimately, it
may be necessary to determine the micro structure of the part volume by
digitizing caste(' parts
26 and automatically determining if part is suitable for use for the
intended purpose. The parameters
27 measured by the inspection stations IS are communicated to a computer
system CS which also
28 communicates with the operator GUI and the TT system of the plant. The
control of the
29 production system is available through the GUI, but as will be explained
below, can be enhanced
through the integration with an integrated knowledge management system, IK.MS,
as shown in
31 Figure 16.
36
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CA 02931412 2016-05-27
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1 [000173] As shown schematically in Fig. 16, the integrated
knowledge management
2 system IICMS is organized as a network of interconnected functional
modules that co-operate to
3 produce molded components, assess their quality according to a variety of
criteria, collect and
4 store data on the components and adjust the production process as
necessary to attain the desired
quality. The system includes the production cell PS that produces the molded
component and
6 delivers it to an inspection system IS. The inspection system collects
data indicative of the
7 quality of the component and associates the information with a unique
identifier indicative of the
8 component that is stored in the part identifier PI. The part identifier
PI delivers the data to a
9 knowledge system KSDAP which communicates with a summing junction where
the manual
input at the process start from the user interface is provided. The output of
the summing junction
11 is used to generate operating parameters PG used as inputs to the
production cell PS.
12 [000174] The part identification PI and knowledge system KSDAP
exchange information
13 with supplementary data sets that include an original production data
set OPDS that represents
14 the original input parameters determined by the operator at the process
start, and a good part data
set GPDS which represents the corresponding parameters for those parts that
pass the quality
16 criteria at the inspection system IS. Similarly, a bad part data set is
compiled from the parameters
17 of components that fail the criteria set by the inspection system IS. A
DMDS data set containing
18 a 3D representation of the component is also available to the knowledge
system and the part
19 identification.
[000175] The inspection system may also communicate via communication
module WiC to
21 remote locations to share data on similar production facilities.
22 [000176] With such a system, there is a need to
see/check/measure micro structure density
23 of the melt or semi-solid slurry before injecting into a mold. This may
be achieved using a real-
24 time 2D x-ray grayscale image of melt/semi-solid slurry can be
correlated to pre-stored optimal
grayscale image (template matching). Or 1D density measurement using x-ray,
gamma or
26 radioactive sources with proper signal evaluation detector can be also
used. The data signals
27 obtained are used to control temperature of the main reactor at
MAXIcastTM semi-solid casting
28 machine in a close loop manner fully automatically to get optimum
content of solids in liquids.
29 These data signals are fed back to Parameters Generator (PG) to generate
improved input(s) at
the casting machine.
31 [000177] The Production System (PS) may not need to be modified
or any different than
37
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CA 02931412 2016-05-27
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Agent Ref: 76798/00016
1 the ones readily available on the market today which typically have
suitable interface
2 communication channels, to ensure fast data exchange. Data exchange over
the communication
3 channel is used to accept input parameter, transfer output parameters to
inspection system and
4 communication with a part identification module (PI), Knowledge System as
well as various data
set data basis as shown in the Fig 16. It is understood that Production System
(PS) may include
6 all required auxiliary equipment commonly associated with Production
System inputs and
7 outputs.
8 [000178] An event log of the process parameters for each cast
part is made available to
9 Original Production Data Set (OPDS) for warehousing and future
processing. Each part cast in
the PS will get assigned unique identification code for tracking and further
processing. Once
11 cast, the part is serialized and ejected from the machine, it is then
sent to at least one inspection
12 system(s) for inspection and analysis. It is understood that inspection
system (IS) can be remote
13 or distributed as well as fully integrated in each production system
(PS).
14 [000179] Even if inspection of the part indicates it is not of
satisfactory quality, this data set
of the bad part will be stored in the Bad Part Data set (BPDS) and some
valuable information
16 from the bad part will be used to accelerate convergence by using in the
new parameters
17 generation for the subsequent casting.
18 [000180] Output from the inspection system module is in digital
or analog format suitable
19 to be transferred to part identification module to associate information
about part received from
inspection system (IS) and store it with production System (PS) original data
set (OPDS). It is
21 also envisioned that some of the inspection and OPDS data sets will also
be transferred to
22 centralized or distributed data centers via wireless communication
networks or Internet for
23 further comparisons or processing. Some other location may be molding
similar or same part and
24 inspection system from this location may be beneficially used to improve
quality of the remote
castings.
26 [000181] The parts identification (PI) module associates
production data set for each part
27 and inspection system data sets and pass this to other modules as
required. The PI data set will
28 contain critical to quality parameters and defect recognition data based
criteria's. The part
29 machine parameters and inspection system parameters are available to
other parameters data base
structures for further processing and assignments via regular communication
channels indicated
31 with thin line. Critical communication protocols are used for high
volume data exchange
38
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CA 02931412 2016-05-27
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1 between data buses and production and inspection system and are shown in
Fig. 16 with a thick
2 line.
3 [000182] Any information useful for the process is shared by
remote users via wireless or
4 cable internet (intranet) communications protocols and stored in the
Knowledge System
(KSDAP) data block. Knowledge System for Data Analyzing and Prediction (KSDAP)
is a tool
6 box with access to a library of algorithms that can be called to analyze
and respond to the data
7 presented. Suitable algorithms include data mining, artificial
intelligence, neural networks, K-
8 Nearest Neighbor algorithm (KNN), Restricted Coulomb Energy algorithm
(RCE), SPC, QLF by
9 Taguchi, fuzzy logic and 1LC. These algorithms may be used alone or in
any other combination
to indicate to the parameter generator PG, the adjustments to the inputs to
the production system
11 PS.
12 [000183] As indicated in Figure 18, the Knowledge System for
Data Analyzing and
13 Prediction (KSDAP) manipulates the data received to extract information
applicable to the
14 control of the production system PS. The KSDAP compares the digital
information data set for
each part from the inspection systems with prior similar parts information
data sets and
16 determines best strategy for part quality improvements. The KSDAP
ensures that only relevant
17 data sets are modified and prepared to be iteratively varied so that
changes to some parameters
18 does not lead to worsening of others and convergence takes much longer
to be attained. Various
19 algorithms are used to prepare data set for Parameter Generator (PG).
[000184] The Parameter Generator (PG) utilizes vector Iterative learning
control (ILC) to
21 modify relevant parameters determined in KSDAP data base to ensure that
next iterative process
22 leads to improved part quality. An example is provided above where the
single axis positioning
23 of the valve pin operated by the electromagnetic actuator in molding
apparatus implements 1LC
24 to slowly approach desired pin position or control melt flow through the
gate. In a similar
manner, the Parameter Generator PG may influence other multiple machine axes
and processes
26 like heat and pressure to attain the required quality of the component.
27 [000185] Finalized input parameters are generated as machine
inputs at the parameter
28 generator PG and directly communicated to Production System to execute
as new iteratively
29 improved set of inputs.
[000186] During iterative learning process at least one of the set of data
for following data
31 bases is used: Good Part Data Set (GPDS), Bad Part Data Set (BPDS),
Designed 3D model Data
39
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CA 02931412 2016-05-27
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1 Set (DMDS) as well as Original Production Data Set (OPDS) for generating
and iteratively
2 improving at least some machine inputs to ensure higher quality part is
casted in subsequent
3 cycle.
4 [000187] The GPDS contain all digital information related to an
acceptable part. All
inspected parts that are acceptable to users are stored in this database. The
BPDS contain all
6 digital information related to defective parts. Defect may be
dimensional, surface or volume and
7 may contain information on the part micro structure and structural inner
inclusions or voids. The
8 DMDS contains data information about part original design and critical to
part inspection items.
9 The OPDS data set contains all production parameters related to each
produced part be it good or
bad.
11 [000188] During iterative process these and other information
will be used to improve
12 production system input parameters. These production parameters related
to high quality part
13 will be available as a record to be printed when part enters the stream
of commerce and requires
14 traceability. The design 3D model data set (DMDS) is used as a reference
for desired outcome.
All critical dimensions and digitized vector information about parts will be
stored in this data set.
16 [000189] The IKMS is incorporated in the production system PS
as indicated in Fig. 20.
17 From which it can be seen that the control input to the production
system PS is provided from the
18 parameter generator PG and the GUI communicates through the KSDAP, where
changes made
19 by the operator can be evaluated and adjustments implemented
accordingly.
[000190] On startup the operator will turn power to the production system,
follow initial
21 checklist related to supply of the material and initial parameters and
safety verification and press
22 the start button. The production system PS will start casting the first
part and upon completion
23 the component is output from the production machine and transported to
the inspection system
24 IS. The inspection system IS determines the quality of the part. If part
is bad, information is
stored in bad part data set data base BPDS. If part is good all information
about this good part
26 will be stored in good part data set data base GPDS. Assuming that the
part is bad, the
27 knowledge system KSDAP will determine which set of parameters needs to
be adjusted
28 iteratively to improve part deficient characteristics and a new set of
inputs is generated in
29 parameter generator PG. By way of a hypothetical example, the inspection
may indicate that the
wheel is not completely formed, indicating insufficient feedstock injected in
to the mold. The
31 inspection system produces a set of image(s) to construct 3D model or x-
ray 3D-Computed
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CA 02931412 2016-05-27
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Agent Ref: 76798/00016
1 Tomography model that when compared to the DMDS (3D design model) by the
KSDAP there
2 is an indication of a missing portion. The KSDAP interrogates the data
base for similar deficient
3 castings and determines the corrective action is to delay the closing of
the pin, KSDAP
4 communicates to the PG which iteratively instructs the parameter
generator to delay the closing
of the valve pin and increments the open period of the pin to provide a longer
injection period.
6 [000191] The next machine cycle is executed, serialized and
passed to the inspection
7 system. More data from the inspection system is generated and more
information allows for
8 faster convergence to a set of parameters that yields a good quality
part. Let us suppose that this
9 time part linear and surface dimensions are acceptable but an x-ray
interrogation uncovered air
entrapment in the body of the part with diameter 300 micrometer. The knowledge
system
11 determines an appropriate step in the iterative process will be to
increase vacuum in the mold and
12 increase pressure of the injection ram.
13 [000192] Again, the parameter generator PG will communicate
through the iterative
14 learning control to modify suitable relevant parameters and produce 3rd
part. When this part is
again x-ray inspected it is determined that inclusion is no longer there. The
component is
16 acceptable and information about good part is stored in the good part
data base GPDS. The
17 production system PS will now use those input parameters that produced a
good part as a new
18 reference set of good inputs and maintain and inspect all new parts
until deviation from good
19 quality is observed. At that point, the knowledge system KSDAP may
access the data collected
and determine the appropriate parameters to be adjusted through the iterative
learning controls.
21 All information stored will be retrievable and subject to comparisons
with design requirements.
22 Information about good set of parameters that produced good parts at
similar conditions may be
23 then made available to any system worldwide casting same wheel type.
24 [000193] Significant savings can be had with this approach for
very large production series
of the identical parts.
26 [000194] Having described preferred embodiment of process of
producing alloy wheel by
27 closing the loop with data from an inspection system and accelerating
convergence with data sets
28 from good parts and bad parts as well as 3D model of the original
design, it will be appreciated
29 that this approach allows processes to produce high integrity molded
components with minimal
rejects. It is believed that other modifications, variations and changes will
be suggested to those
31 skilled in the art in view of the teachings set forth herein. It is
therefore to be understood that all
41
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CA 02931412 2016-05-27
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1 such a variations, modification and changes are believed to fall within
the scope of the present
2 invention as defined by the appended claims. Although specific terms are
employed herein, they
3 are used in their ordinary and customary manner only, unless expressly
defined differently
4 herein, and not for purposes of limitations.
42
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Representative Drawing