Note: Descriptions are shown in the official language in which they were submitted.
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A method for machining sheet parts by using a mecatronic
machine tool
The invention relates to a method for machining sheet parts
from continuous strip-like sheet material, such as coiled
sheet metal, or sheet material in sheets, by means of a meca-
tronic machine tool.
Sheet parts can be machined from sheet material by numerous
methods. If we consider the entire chain of work steps, for
example, from coiled sheet material to a completed sheet
product, which has been machined by applying several working
methods, the combinations of methods can at the roughest
level be divided into methods for short production runs and
those for long production runs.
In short production runs the machining of sheet parts is
usually done by first slitting the sheet into strips, where-
after the strips are cut into pieces of suitable length.
Thereafter the machining of the pieces is continued according
to need by punching, drilling, notching, etc. When this method
is used, the tool costs are moderately low and the delivery
time is short. l'he manufacturing costs are high because the
work stages are numerous and there are several transfers from
one work station to another. The dimensional precision is poor.
The latest equipment for short production runs consists of
so-called sheet-working centers, in which the machining is
carried out by punching, nibbling, and laser cutting. The
characteristics of sheet-working centers are in general as
follows:
- dimensional precision is good,
- standard tools can be used,
- standard sheet sizes can be used,
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- delivery time is short,
- equipment is very e~pensive,
- the share oE capital outlays in manufacturing costs is
large t
- arranging unmanned production is difficult and expensive,
- manufacture of small parts is not competitive.
one method of handling sheet material in these sheet-working
centers is to cut the sheet material coming from a coil first
into sheets, which are transferred automatically to the actual
working center. At the working center the sheet is machined
by one or several of the above-mentioned methods, the tools
themselves being fixed and the point to be machined being
directed into place by moving the sheet. Such equipment is
large in size and also very expensive.
Strip-like sheet material has been handled in short production
runs by hot-cutting methods and, fully analogously with this
method, also by using a laser cutter. Here the small number
of alternative machining methods, i.e. only one work method,
restricts the uses, owing either to deficient dimensional
precision or to low speed. If the piece re~uires substantial
cutting in proportion to its size and the shapes to be cut
are such that they can be done more easily by other machining
methods, low speed becomes the problem.
Punching has also been applied to the machining of strip-like
sheet material. In this method the band is fed ~orward a~
transfer intervals corresponding at least to the size of the
final product, the cutting of the product and its detaching
from the strip being synchronized with this transfer. In
addition, the method includes a beam which contains the
punching tools and can be moved transversely in relation to
the travel direction of the sheet. By means of these tools
the punching takes place after the tool or the tools have
been brought to the intended point by transferring the sheet
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forwards over a suitable step in the longitudinal direction
and the tool beam over a suitable distance in the transverse
direction. In this methodr also, there are the following
problems: (1) the longitudinal movement is only forwards in
steps and by moving the sheet, and therefore imprecision and
detrimental restrictions regarding the shape of the piece
result; (2) the work method is limited to one, i.e. punching;
(3) all pieces across the entire width of the sheet are cut out
at the same time, in which case either a) only one piece is
cut over the entire width, which limits the size of the piece
or presupposes previous slitting of the sheet into the correct
width, or b) if there are several pieces in parallel, several
similar cutting tools in parallel are needed , aligned both
with one another and with the preceding punch, which results
in complicated and expensive tools; (4I the interspacing of
the patterns of the final product so that the sheet surface
is used effectively is successful only in special cases.
A long production run takes place by means of presses and
feeding devices from a strip coil which has been previously
slit to the correct width. The machining is by serial tools,
the workpiece being completed in one pressing. The advantages
of this method include high dimensional precision and low
manufacturing costs, if the production run is long enough. The
disadvantages include:
- long delivery time (preparing of the tool, cutting of the
coil of strip in advance),
- expensive tool (usually suitable for the manufacture of
only one product),
- in the slitting of the coil of strip in advance, a proportion
of the raw material goes to waste,
- the strip slit in advance must be ordered in the correct
amount, otherwise either the number of products is too small
or a quantity of the strip is left over r
- the production cannot be carried out in an unmanned system
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for longer than it takes to come to the end of a coil of strip,
- in short production runs the manufacturing costs are high.
The greatest disadvantages of the current machining methods
are either that the manufacture of the end product must be
divided into several partial work steps on different machines,
or that it is necessary to invest in an unreasonably
complicated and expensive machine. In both cases the costs
are too high.
Furthermore, the difficulties are increased by the fact that,
regardless of which alternative has been chosen, it must
further be decided whether to choose a setup suitable for -
short production runs or for long production runs, in which
case one of the alternatives respectively suffers. A dis-
advantage common to all other methods and combinations of
methods~ with the exception of hot/laser cutting, is the
considerable waste of material between the patterns cut or
between the cut pattern and the edge of the strip. The
disadvantage of hot/laser cutting, for its part, was the use
of only one work method, which is not suitable for all pieces.
.
Let us now set the following requirements for the method for
implementing the machining:
1) It must be possible to use as raw material a standard
stored material, either in flat form or colled, so that during
the entire manufacturing procedure it is not cut into sheets
or slit into a strip corresponding to the width of the product.
This must be done in order to reduce the number of work steps
substantially, to reduce the number of alternative materials
substantially, and to reduce material waste substantially.
2) The method must be such that, when it is used, it must be
possible to apply at least nearly all known methods of
machining, such as punching, nibbling, drilling, laser cutting,
- etc., in combinations chosen freely according to the situation.
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3) The method must be such that, when it i5 used, the tool
type can be selected individually to correspond to the size of
each specific batch of pieces. For e~ample, a short production
run is by laser cutting and drilling, a longer run by multi-step
punching and cutting, and a very long run by using a conventional
serial tool in a press.
4) It must be possible to change the product at any moment,
without additional waste of material.
5) The method must be easy to automate so that continuous
manning is not needed.
6) The dimensional precision achieved must be good.
All of the above objectives cannot be achieved by any of
the known methods described previously.
By the method according to the invention, a crucial
improvement is achieved regarding all of the disadvantages
described above. In order to achieve this, the invention provides
a method for sequentially continuous machining or shaping of sheet
pieces from sheet material of nonfixed width, wherein only part of
the sheet material at a time is under machining, the sheet
material is fed in steps and only in one of its longitudinal
directions forwards to the machining area, and on the sheet
surface, in a direction perpendicular to its travel direction,
there have been positioned in parallel one or several workpieces,
and the tool holders, together with the tools, are transferred, in
one working unit, only in a direction, which is substantially
perpendicular to the travel direction of the sheet, starting from
one longitudinal edg of the sheet and ending at the other
longitudinal edge of the sheet, while the sheet material remains
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stationary, and that when, after a longitudinal transfer of the
sheet material, this unidirectional straight transfer of said
working unit is repeated, the workpieces of this working lane have
been arranged to fit or adjoin, without steps, the other
workpieces in the other, in the travel direction of the sheet
adjacent, work~ng lanes, wherein one or several machine tools are
attached, Ln accordance with a machining method or machining
method combination used simultaneously or separately, to tool
holders on at least one side of the sheet; that a machine tool
attached to one tool holder, together with its driving mechanism,
can be guided to operate with a pre-planned sequencing differing
from that of the other machine tools attached to the same tool
holder, but in synchronization with them; and that each of the
different tools in use carry out its machining operations during
said unidirectional straight transfer controlled on the basis of a
predetermined, even, small-stepping.
The following factors can be considered to be the most
essential advantages of the invention:
- standard sheets and standard coils of strip can be
used as raw material,
- by combining standard tools it is possible to
manufacture many different types of pieces,
- great dimensional precision,
- manufacturing costs are low also in short production
runs,
- it is possible to use the cheapest possible raw
material,
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- the loss of raw material is smaller than in other
methods,
- it is possible to use full coils of strip, for example
10,000 kg/coil, in wh.ich case the manufacture can continue
unmanned throughout the len~th of the coil, for example for 400
hours,
- the manufacture can be computer-controlled; in this
case
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all of the operations of the enterprise can be computerized,
the subsequent refining of the piece can be carried out
easily by using manipulators or robots,
- it is directly suitable as a part of an automatic production
line,
- replacements and settings of the tool can be automated,
- changes of series can be carried out by using a computer
program,
- it is possible to apply various manufacturing methods r
drilling, punching, cutting, drawing, slotting, nibbling,
plasma cutting, laser cutting,
- the quality control of the workpiece can be carried out by
a computer immediately, 100 %,
- it is possible to machine most raw materials,
- it is possible to manufacture exactly the required number
of products. The remaining material can be used for other
production, since standard sizes are used.
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~ The invention is described below in detail with reference to
the accompanying figures.
,
Figure 1 depicts schematically, as an axonometric representa-
tion, an application according to one embodiment of the
inve~tion,
Figure 2 depicts a schematic side view o~ an application
according to the embodiment of Figure 1,
Figure 3 depicts schematically one method of interspacing the
products on the sheet, made possible by the invention,
Figure 4 depicts a schematic representation, from below, of
one tool/work method setup aGcording to the invention,
Figure 5 depicts another method of interspacin~ the products
on the sheet, made possible by the invention,
Figure 6 depicts one product form easily achieved by the
method according to the invention.
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Figure 1 shows an overall representation of an embodiment of
322~
the invention. In the embodiment concerned, the machining
method is punching, but the use of some other machining method
changes only one single tool, and not the way or method of the
invention for using them together or separately.
In Figures 1 and 2 the sheet raw material 15 comes from a
sheet coi.l 5, which is standard stored material. The feeding
of the sheet forwards is here implemented by means of a power
engine 13 and rolls 10, the sheet 15 pressed between them
being moved forwards over the distance necessary at each given
time. Transfer devices of other types can also be used. In
this case, to the frame 9 of the tool holder there have been
attached three hydraulic presses 8 in which the tools are two
punching dies 2 and one upper cutter blade 1~ Opposite to these
there are, attached to the same frame 9, bolsters 4 and a
lower cutter blade 3. This is possible to accomplish by making
the frame 9, for example, in the shape of a U, to the branches
of which, at mutually corresponding points, the upper and
lower tools are attached by means of, for example, mounting
plates, not shown in this figure. The tool-holder frame 9 is
mounted, for example on guides 11, which may be several in
number and/or be positioned in different ways. The frame 9 is
moved transversely in relation to the travel direction 16 of
the sheet 15, in direction 17, by a transfer device 12, for
example in the form of a ballscrew with the aid of a power
engine 14.
The machining of the workpieces and their detaching from the
sheet 15 is done here transversely relative to the travel
direction 16 sf the sheet, starting from the first edge 18 of
the sheet 15. In the first machining step the foremost of the
punching dies 2 makes the hole of the first workpiece in area
a of this workpiece The cutter and the latter of the punching
dies 2 are at this time outside the edge 18 of the sheet. In
the following step the foremost of the punching dies 2 makes
the first hole of the second workpiece in area b of this
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workpiece, and the latter of the punching dies 2 at the same
time makes the second hole in area a of the first piece,
detaching both scrap pieces 7. In the third step the punching
dies work in areas c and b, as above, while the cutter 3, 4
detaches the first comple~ed workpiece 6 from area a. There-
after the punching dies move to areas d and c and the cutter
to area b, where the above-mentioned work steps are repeated.
When the cutter 3, 4 has detached the last completed workpiece
in this row, from area m, at which time the punching dies are
outside the other edge 19 of the sheet, the entire frame 9
together with the tools returns to the first edge 18 and
starts repeating the above-described chain of work steps
towards the other edge 19 of the sheet. The procedure continues
in this way until the sheet 15 has been used up, or until the
ordered series of workpieces has been made, whereupon either
the sheet coil is replaced with another or, in the lat~er
case, the tools are replaced with others and the machining of
a new piece is started, for example further from the same
sheet, if the material remains the same.
When operating ~y the method described above, only one set of
tools corresponding to the piece is needed, and the tools
need to be aligned only in relation to one another, in which
case the tooling costs remain low and high precision is
achieved. The waste material is as small as it in general can
theoretically be in the machining method in question, since
pre-slitting into strips is not needed. The interval between
replacements o~ material is long, since the coil contains
considerably more material than, for example, slit coils
corresponding to the width of one product. The savings of
material are further increased by the fact that, as the
procedure starts from sheet edge 18, machining all the way
to edge 19, it is possible in different machining lanes I-II,
etc. (Figure 3) to interspace the products 20 in the manner
which is considered best, either in the travel direction 16
of the sheet 15, as in Figure 3, or in the travel direction
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17 of the frame 9 of the tool holder, or in both directions
simultaneously over the entire surface of the sheet 15. In
Figure 3, in which the length of the workpiece is A, the
saving thus achieved is of the magnitude B (this is only to
illustrate the principle, there may be found an even more
efficient layout for the pieces concerned). The workpiece 20
can be replaced, in the middle of the sheet, with workpiece
21, the only limiting condition being that the sheet material
is the same. Such bi-directional interspacing and replacement
is not possible in other combinations of machining methods.
The method described above is perhaps one of the most primitive
embodiments according to the invention. However, the method
is suitable for use with considerably more complicated
equipment. There may be a considerably larger number of tools
2, 4 and 1, 3, they can be easily replaced by means of bolt
attachment or automatically; and their positions can for this
reason be easily changed. When control logic is added to the
method, such as numeric control, for example nibbling function
is produced. In this case the punching die can be ~itted to
make, for example, 50 punchings while the frame 9 moves at an
even, small-step speedr whereafter the other tools make one
punching. This nibblin~ can be diversified by making in the
tool holder frame 9 one or several tool holders 23 guidable
in different directlons.
Figure 4 depicts such an arrangement, in which the tool holder
23 has been arranged to be movable by means of a transfer
device 37 in direction 22, which is transverse or perpendicular
to the travel directions 17 of the frame. In this case the
nibbling, slotting or laser cutting can be controlled
simultaneously in two mutually perpendicular directions 17
and 22, which are at the same time independent of one another.
By means of this arrangement, the moving of the sheet 15
during the machining of one row of workpieces is also avoided;
such moving would easily cause flaws in the piece. In terms
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of control the most advantageous manner of moving the tool
holder frame 9 and for transferring the tool holders relative
to the frame is to use a machine element producing a linear
transfer; there exist several types of such machine elements.
In the tool holder frame 9 there may be several tool holders
23, 25, and 27, all, some or one of which can be controllable
during work, such as the holder 23, or adjustable only in
connection with the replacement of the tools, and there may
be attached to each oE them several tool sets 2~, 26, and 27.
In an individual tool set there may be several tools, for
example several punching dies in a hydraulic press. Each of
these tool sets may be of any ~ype of mach~ning method with its
control devices and power sources. When necessary, it is of
course also possible to use a common power source. The tool
holders, or some of them, may be positioned below the sheet 15,
for e~ample, in the lower branch of the frame 9, or there may
be tool holders on both sides of the sheet 15 and simulta-
neously in use. In this case it is possible to take into
account the asymmetry of the machining trace in the direction
of sheet thickness and its effect on the completed workpiece.
It isj for example, possible to punch or cut the different
holes of one and the same workpiece from different directions.
The tools to be attached to the tool holders may carry out
any machining methods allowed by the limiting conditions of
an individual machine construction, such as drilling, punching,
cutting, nibbling, plasma cutting, slotting, e~c., and also
shaping methods such as chamfering, for example from the side
edge or front edge of the sheet, flanging, compression molding,
etc. In the present patent application and its claims,
machining is deemed to designate also shaping. ~-
The tool holder frame 9 transferrable and guidable transversely
to the travel direction 16 of the sheet 15, or in general the
entity made up of the tool holders; the tool holders 23, 25,
27, etc., transf~rrable and guidable in relation to this,
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which can be transferred by a linear movement or by means of
eccentrics, etc. relative to the frame; the tools attached to
each tool holder and usable independently of one another,
constitute a hierarchical entity (cE. decision tree, etc.).
Such an entity is suitable for control by using microprocessors
or complete computers, and particularly microcomputers, in
which case their programming can be carried out simply by
following the machining-technique hierarchy with the main
program-subprogram hierarchy. Although the frame, the tool
holders, and the tools with their actuating devices are as
such independent of one another, their operation in relation
to one another must, of course, be sequenced correctly, i.e.
they must be mutually synchronized.
When tool holders 23, 25, 27, etc. adjustable or controllable
in a sufficiently versatile manner are used and when a logic
control device sufficiently versatile and flexible, for example
a microcomputer, is used, the workpieces, for example, can be
positioned on the sheet 15 in a manner which greatly saves
surface. For example, in Figure 5, every other row of work-
pieces is a mirror image of the adjoi.ning rows. In reality
the workpieces can be positioned on the sheet arbitrarily,
even every individual workpiece 29-36 in a different position,
provided that the coverage of the sheet 15 surface is effective
and the machining itself takes place in a direction transverse
to the sheet 15.
Effective control and the versatile possibility to move the
tools in accordance with the invention also allow standardiza-
tion of the tools. This means that each opening, hole
combination and piece outline does not require a separate
tool made specifically for it. For example, the piece in
Figure 6
a~ if made by using a serial tool in a press, requires 32
punching dies and a cutting device in the tool, which is
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b) if made by laser cutting, the machining is slow;c) if made in several work steps using conventional workshop
techniques, the machining is both slow and expensive. By
using the method according to the invention it i5 possible to
select the machining methods and tools suitable for the size
of the series, for example, holes 37 by using punching die 1,
holes 38 by using punching die 2, all small holes 39 (compared
with the diameter, because of the ~reat sheet thickness) by
using drill 3, openings 40 and the outline by laser cutting.
In this case the drillings are controlled numerically, as is
the laser cutting. As the series to be produced lncreases in
size, a shift is made to punching and cutting to the extent
appropriate.
As regards the details of the tool holder frame 9 and the
machining technique, it must be taken into account that if the
frame is of the shape U presented, in the machine the tool
traveling last in the travel direction 17 on each row must
carry out the cutting step, in order that the result should
be a removed sheet lS area corresponding to the removed work-
piece, to provide room for the central part of the U-shape. If
the upper tool holders are guided without a U-shaped frame,
for example numerically, into alignment with the lower bolsters
concerned, or if the machining methods are such that lower
bolsters are not needed, the waste material can be left in
strip form because, in this case, the route along which it is
removed is always free. Usually it is, however, most advanta-
geous to cut off the waste material, because then the front
edge of the sheet 15 in its travel direction 16 remains neat,
which makes it easy to continue the work. The transfer of the
remaining coil of the sheet and its handling, if the work is
discontinued at such a stage, is then also possible without
additional work steps.
The invention is not limited to the examples described above;
the method can be modi~ied and various machining methods and
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machine elements not mentioned here, as well as computertechnology, can be used in carrying out the method.
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