Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02913288 2015-11-24
3D METAL PRINTING DEVICE AND PROCESS
BACKGROUND OF THE INVENTION
[0001] Various systems that utilize 3D polymer printing have been
developed.
However, the polymer parts produced utilizing known 3D printers may have
limited use.
BRIEF SUMMARY OF THE INVENTION
[0002] One aspect of the present invention is a 3 dimensional (3D) printing
device/machine/apparatus that deposits successive layers of molten metal
utilizing a
welding system to fabricate a metal part corresponding to a 3D model that may
be
generated using computer aided design (CAD) software. The machine also
includes a
powered cutting tool that may be utilized to remove a portion of the metal
deposited by
the welder after the molten metal has solidified. Numerous layers of metal can
be
deposited and machined to form complex 3D metal parts that have exact
tolerances as a
result of the machining steps. Parts fabricated using the 3D apparatus/process
of the
present invention do not suffer from imperfections between the layers of metal
found in
parts made from other 3D metal printing processes (e.g. laser sintered metal
particles)
because the molten metal layer melts and fuses completely with the metal layer
below
it. The machine may include a head assembly having a welding head and a
machine
tool. During fabrication of a metal part, the part may be positioned on a
metal plate or
other suitable support whereby the part can be fabricated (3D printed) by
welding and
machining operations without removing the part from the support.
[0003] Parts may be designed utilizing CAD software, and the CAD model/data
may be
converted to a stereolithographic (STL) model/data or computer aided
manufacturing
(CAM) software. The STL model data may be imported to three dimensional
"slicing"
software to create individual slices based on desired parameters such as layer
height,
solid layer, in fill, fill pattern, pattern spacing, diameter of the wire
size, size of the
objects, starting point, etc. The slicing software or CAM software can be
utilized to
produce Computer Numerical Control (CNC) G-code.
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[0004] The
welding head may comprise a gas metal arc welding (GMAW) device
(also known as MIG welding). Steel, aluminum, or other metals may be utilized
in the
process. The machining head may comprise a rotary milling unit having a rotary
cutter.
Alternatively, the machining head may comprise a grinder or other suitable
device as
required for a particular application.
According to one aspect, there is provided an apparatus for fabricating 3D
metal
components, the apparatus comprising: a support configured to retain a
partially
formed metal component during fabrication of the metal component; a two-axis
device
secured to the support, wherein during fabrication of the metal component, the
two-
axis device is configured to rotate the partially formed metal component about
a
rotation axis and to pivot the partially formed metal component about a pivot
axis that
intersects the rotation axis; a head assembly including a welding head and a
machining
head, the machining head including a tool that is configured to remove metal
deposited
by the welding head during fabrication of the metal component; and a control
system
configured to move the welding head relative to the support and to deposit
molten
metal in successive layers, wherein the control system is configured such that
the tool
removes metal from at least one layer of metal deposited by the welding head
after the
molten metal has solidified.
According to another aspect, there is also provided a method of forming 3D
metal components, the method comprising: depositing molten metal onto a
support in
successive layers while rotating the deposited molten metal about a rotating
axis and
pivoting the deposited molten metal about a pivot axis that intersects the
rotational axis
using a two-axis device secured to the support to form a 3D metal structure
utilizing a
machine that controls the depositing of metal according to a predefined
program; and
removing at least a portion of the 3D metal structure utilizing a machining
process that
is controlled according to a predefined program, wherein the machining process
is
performed without removing the 3D metal structure from the support.
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[0005] These and other features, advantages, and objects of the present
invention will be further understood and appreciated by those skilled in the
art by
reference to the following specification, claims, and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Fig. 1 is an isometric view of a machine/apparatus according to
one
aspect of the present invention;
[0007] Fig. 1A is an isometric view of the machine/apparatus of Fig. 1;
[0008] Fig. 2 is an elevational view of a portion of the machine of Fig.
1;
[0009] Fig. 3 is an isometric view of a portion of the machine of Fig. 1;
[0010] Fig. 4 is an isometric view of a 3D CAD model of a part;
[0011] Fig. 5 is an isometric view of an STL or CAM model;
[0012] Fig. 6 is a schematic isometric view of a 3D metal printing
apparatus and
process according to one aspect of the present invention;
[0013] Fig. 7 is an isometric view of a machining process according to
the
present invention;
[0014] Fig. 8 is an isometric view of a machining process according to
the
present invention in which additional layers of metal have been added;
[0015] Fig. 9 is a schematic drawing of the electrical components of the
system;
[0016] Fig. 10 is a schematic view of the welder electrical system;
[0017] Fig. 11 is a schematic view of the electrical motor control;
[0018] Fig. 12 is a schematic view of an electrical system for the A and
B axes
device of Fig. 3; and
[0019] Fig. 13 is a schematic view of an electrical system for the A and
B axes
device of Fig. 3.
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DETAILED DESCRIPTION
[0020] For purposes of description herein, the terms "upper," "lower,"
"right," "left,"
"rear," "front," "vertical," "horizontal," and derivatives thereof shall
relate to the
invention as oriented in Figs. 1 and 1A. However, it is to be understood that
the
invention may assume various alternative orientations and step sequences,
except
where expressly specified to the contrary. It is also to be understood that
the specific
devices and processes illustrated in the attached drawings, and described in
the
following specification, are simply exemplary embodiments of the inventive
concepts
defined in the appended claims. Hence, specific dimensions and other physical
charac-
teristics relating to the embodiments disclosed herein are not to be
considered as
limiting, unless the claims expressly state otherwise.
[0021] With reference to Figs. 1 and 1A, a 3D metal printing apparatus or
machine 1
according to one aspect of the present invention includes a welding gun or tip
54 and a
machining head 42 that are operably mounted to a base 2 for powered 2 axis
movement
relative to base 2 in the Y and Z directions. Base 2 may be mounted on rollers
4. A
support 6 is movably mounted to the base 2 for linear reciprocating movement
along
the X axis. The support 6 may be movably mounted to base 2 by linear guides
comprising elongated rods 8 and pillow blocks 9. Other suitable linear guides
may also
be utilized. A powered actuator such as a first electric motor 10 having a
ball screw
drive may be selectively actuated by a control system such as controller 12 to
shift the
support 6 along the X axis. It will be understood that controller 12 comprises
a control
system that may include numerous components. Thus, the terms "controller" and
"control system" as used herein are not limited to a specific controller, but
rather
broadly refer to a control system/device that provides for control of 3D metal
printing
machine 1 and/or related components utilized therewith. As discussed in more
detail
below, a work plate assembly 14 may be mounted to a two-axis mechanism 16 that
is
mounted to the support 6. In use, parts are fabricated on the work plate
assembly 14,
and the two-axis mechanism 16 provides for powered rotation of the work plate
assembly 14 about two additional axes A and B (Fig. 3) to provide 5 axis
capability.
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,
,
[0022] Base 2 includes an upper mounting structure 18. Including a
pair of upwardly
extending side portions 20 and a horizontal upper portion 22 that extends
between the
upright side portions 20. A bracket structure 24 is movably mounted to the
upper
mounting structure 18 for powered back and forth movement along the Y-axis.
The
bracket structure 24 may be movably mounted to horizontal upper portion 22 of
upper
mounting structure 18 by a linear guide including elongated rods 26 and pillow
blocks
28. A second electric motor 30 and ball screw 32 provide for powered
horizontal (Y
direction) movement of bracket structure 24 relative to base 2. The second
electric
motor 30 is also operably connected to the controller 12.
[0023] An upright plate 34 is movably mounted to the bracket
structure 24 for
reciprocating vertical (Z direction) movement by a linear guide including rods
36 and
pillow blocks 38. A third electric motor and ball screw 40 provide for powered
vertical (Z
direction) movement of plate 34 relative to bracket structure 24. The third
electric
motor 40 is also operably connected to the controller 12.
[0024] A machine head 42 (see also Fig. 2) is mounted to the plate 34
by brackets 44 or
other suitable means. The machine head 42 includes an electric motor 46 and a
spindle/collet 48 that rotates upon actuation of the electric motor 46. The
electrical
motor 46 is also operably connected to controller 12. A cutting tool 50 may be
mounted
to the spindle 48 utilizing a suitable collet or other such arrangement. In
the illustrated
example, cutting tool 50 comprises a mill having cutting edges 52 that are
configured to
cut/remove metal from a part during fabrication thereof. It will be understood
that the
machining head 42 may comprise a drill, grinder, laser, or other suitable
machine tool
configured to remove metal.
[0025] Referring again to Fig. 2, a welding gun/tip 54 is mounted to
a bracket 56.
Bracket 56 includes a vertically extending portion 58 and an upper horizontal
portion 60.
Thus, in the illustrated example, the bracket 56 has a shape that is somewhat
similar to
an upside down L. The bracket 56 is movably mounted to the plate 34 for
vertical (Z
direction) movement relative to plate 34 by linear guides such as rods 62 and
pillow
blocks 64. A fifth electric motor 66 and ball screw 68 operably interconnect
the bracket
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56 and plate 34 to provide powered vertical (Z direction) movement of bracket
56
relative to plate 34. The fifth electric motor 66 is also operably connected
to the
controller 12. The welding tip 54 is connected to a welding unit 70 (Fig. 1)
by one or
more lines 72. The welding tip and welding unit 70 preferably comprise a metal
inert
gas (MIG) welding unit, and inert gas and wire are fed to the weld tip 54
through the
lines 72 in a known manner. As discussed in more detail below, the welding tip
54 can
be vertically shifted upon actuation of electric motor 66 from a retracted
position shown
in solid lines in Fig. 2 to an extended position shown in dashed lines in Fig.
2. This causes
welding tip 54 to extend and retract relative to the machining head 42. When
welding
tip 54 is extended, it deposits molten metal onto metal plate 84 (Fig. 3).
Extensions of
weld tip 54 ensures that cutting tool 50 of machine head 42 has clearance and
does not
interfere with the welding operation. It will be understood that machining
head 42
could extend and retract vertically relative to welding tip 54, and the
present invention
is not limited to the specific arrangement shown and described herein.
[0026] With further reference to Fig. 3, two axis mechanism 16
includes a base 74 that
is secured to support 6. A second portion 76 of two axis mechanism 16 is
rotatably
mounted to the base 74 for rotation about a horizontal axis as shown by the
arrow "B."
An upper portion 78 of the second portion 76 is movably mounted for rotation
about a
second axis as indicated by the arrow "A." A work plate assembly 14 may be
secured to
the upper portion 78 of two-axis mechanism 16. The work plate assembly 14 may
comprise a ceramic plate 82 and a metal foundation work plate 84 that is
secured to the
ceramic plate 82. A powered actuator and drive unit 80 is operably connected
to
controller 12, and provides for powered rotation of upper portion 78 and plate
assembly
14 about the A and B axes. The two-axis mechanism 16 may comprise a known
device
utilized in CNC machines and the like, such that a detailed description of the
two-axis
mechanism 16 is not believed to be required. Also, it will be understood that
the 3D
metal printing machine 1 would not necessarily need to include a two-axis
mechanism
16 to create a 5 axis 3D metal printing machine if 3 axis movement is
sufficient for a
particular application.
CA 02913288 2015-11-24
[0027] During operation, the weld tip 54 is shifted to the extend position
shown in
dashed lines in Fig. 2, and weld tip 54 is brought into close proximity with
the metal
foundation plate 84. The welding unit 70 is then actuated by controller 12,
and the weld
tip 54 is moved along the metal foundation plate 84 according to a software
program
loaded into controller 12 to create a bead of molten metal having a predefined
shape
and size as required to form a first layer of a part. The welding tip 54 can
be moved
along the desired path by actuating electric motor 10 to shift support 6 (Fig.
1) and /or
by actuating electric motor 30 to shift bracket structure 24. The two axis
mechanism 16
may also be actuated by controller 12 to provide movement of plate assembly 14
relative to welding tip 54. The electric motor 40 (and/or electric motor 66)
may also be
actuated to control the height of plate 34 to provide proper vertical
positioning of weld
tip 54 relative to the metal foundation 84. As discussed in more detail below
in
connection with Figs. 6-8, the molten bead of metal produced by weld tip 54
may have a
shape and size that is specifically selected to provide a layer corresponding
to a shape of
a finished metal part. The metal wire supplied by welding unit 70 may comprise
steel,
aluminum, titanium, stainless steel, or other suitable metal.
[0028] After the metal bead is deposited utilizing the weld tip 54, the
weld tip 54 may
be retracted relative to the machining head 42 by actuation of electric motor
66. The
machining head 42 may then be actuated by controller 12, and the cutting tool
50 may
be brought into engagement with the weld bead after the molten metal has
solidified.
Cutting tool 50 can be utilized to remove a portion of the weld bead to
thereby shape
the bead. The machining head 42 is then deactivated, and the welding tip 54 is
then
extended, and an additional layer of molten metal is then deposited on top of
the
previously deposited metal bead to form a "new" metal bead. The new metal bead
can
then be machined utilizing machining head 42. As discussed below in connection
with
Figs. 6-8, this process may be repeated to build up successive layers of metal
having a
shape corresponding to a component that was designed utilizing CAD software.
It will
be understood that successive layers of metal may be deposited utilizing the
weld tip 54
without machining of each layer. Alternatively, the machining head 42 may be
utilized
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,
to machine one or more layers of metal after the layers are deposited by
welding tip 54
if required to produce a particular part.
[0029] With further reference to Figs. 4 and 5, a CAD model 86 is shown on
a display
screen 88. CAD model 86 may be developed utilizing known CAD software. The CAD
model 86 may be utilized to produce a stereolithographic (STL) model/data 90
utilizing
known software. The STL model data format is then imported to a 3D slicing
software
program to create individual slices (layers) based on desired parameters such
as layer
height, solid layer, in fill, fill pattern, pattern spacing, diameter of the
wire, size of the
objects, starting point, etc. Software may also be utilized to produce CNC G-
code that is
used to control machining head 42 and the position of weld tip 54. CAM
software may
also be used to produce CNC G-code. Thus, additional information such as
speeds, feed
rates, and cooling requirements may also defined for a specific machining head
42 and
part being produced by 3D metal printing machine 1 as required. Depending on
the
desired surface quality, machining can be done on the top and/or on the sides
of the
layer(s).
[0030] The CNC program is then loaded into the controller 12. During
operation, the
controller 12 provides controlled movement of the weld tip 54 and machine head
42 in
the three linear X, Y, Z and two rotational directions A, and B which are
controlled by the
CNC program. The power and feed rate is controlled by weld unit 70 and
controller 12.
As noted above, after a layer of metal is deposited, the welding head or tip
54 may be
retracted utilizing motor 66 to permit machining operations prior to
depositing the next
layer of metal. The cutting tool path is also guided by the CNC program.
[0031] As shown schematically in Fig. 6, a partially completed metal part
92 comprises
layers of metal 92A-92C deposited onto metal plate 84 by weld tip 54. As shown
in Fig.
7, the partially fabricated metal part 92 may be machined utilizing cutting
tool 50 and
machining head 42 upon retraction of the welding tip 54. With further
reference to Fig.
8, the part 92 may be finished utilizing the cutting tool 50 after the
required number of
layers of metal have been deposited. After the part has been fabricated, it
can be cut
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from the metal foundation 84. The thickness, height, and size of the built-up
walls can
be controlled precisely through deposition and machining control at each step
and layer.
[0032] Referring again to Fig. 1, a measuring unit 94 may be utilized upon
completion of
the work piece to verify that the part that has been fabricated meets the
dimensional
requirements. The measuring unit 94 may comprise a probe (mechanical contact
device) or a laser measuring head. Measuring unit 94 may comprise a 5 way
mechanical
contact device with a spherical ruby tip (sizes 1, 2, 3, or 4 mm). The probe
94 is
mounted in the spindle collet 48 or on a separate fixture. Through digital
input
interface, a CNC controller is coupled to a probing input. For measurement, a
G-code
based predefined routine is used. A G-code or CNC code program controls
welding/machining operations. Because the G-code is based on a standard, the
probe
94 works independently of the type of the CNC machine controller. When used
with the
machine 1, the probe 94 scans the 3D surface and X, Y, Z coordinates on each
contact
point are obtained and saved to the same computer controlling the CNC machine
1.
Using CAD or 3D modeling software, a 3D model can be created from these
measured
coordinates. The 3D (measured) model may be used for inspection, reverse
engineering, or to create a new CNC program for welding/machining. In contrast
to the
process utilized in Coordinate Measuring Machines (CMM), the CNC scan
movements
are utilized in this process.
[0033] A process according to the present invention does not require
removing and
alignment of the measured workpiece because the probe 94 may be mounted in
machine 1 while the part being measured remains in place on machine 1. The
number
of measurements can be controlled depending on the type of the measured
surface
within the resolution of the machine. For common surfaces such as cylinders,
spheres,
cones, and planes, relatively few points are sufficient to establish the
measured surface.
For 2D profiles or 3D free form surfaces the number of measured points can be
increased to achieve a required resolution.
[0034] Probe 94 can be utilized to measure a part that has been fabricated
utilizing
machine 1 without removing the part. If measurements show that the part does
not
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,
have the required shape/size, the part can be modified by adding additional
metal
utilizing weld tip 54 and/or machined utilizing cutting tool 50. In this way,
the part can
be modified by adding and/or removing metal as required to provide the
required
dimensions.
[0035] Also, existing metal components that are worn or damaged may be
positioned in
machine 1, and probe 94 can be utilized to measure the component. The measured
3D
model can be compared to a 3D model of the component without wearing/damage,
and
machine 1 can be utilized to add and/or remove metal as required to repair the
component.
[0036] Exemplary electrical circuits 96, 98, 100, 102, and 104 are shown
in Figs. 9-13. It
will be understood that the 3D metal printing machine 1 is not limited to the
specific
configuration described herein, and the electrical circuits of Figs. 9-13 are
merely
examples of suitable arrangements.
[0037] It is to be understood that variations and modifications can be
made on the
aforementioned structure without departing from the concepts of the present
invention, and further it is to be understood that such concepts are intended
to be
covered by the following claims unless these claims by their language
expressly state
otherwise.
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