Note: Descriptions are shown in the official language in which they were submitted.
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PATENT
Attorniey Docket No 5243-4
~T~OD ~N~ APPAR~U~ FOR hA8ER CUT~IN~
REPETITIVE PATTBRN8 IN A CONTIN~OU~LY
NOVING 8TREAM OF MATERIA~
Bac~round o~ th~ Invention
I. ~iald o~ th Inv~itio~-
The present inventlon relatos generally
to a method and apparatus for using a laser to cut
patterns repetitively in a oontinuous}y moving
sheet o~ material.
The known method of laser cutting
patterns in a itream o~ ma~erial i8 to sequentially
advance the material by a conveyor into a cutting
zone, and then while the material is stationary,
U9Q an x-y aptical positioner to cut a pattern ~rom
the material by moVing a ~ocused beam o~ coherent
radiation over the materlal. The beam 1s caused to
~raverse the patt~rn under control of a digital
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computer and numeric machine controller which
process ~tored data representing the pattern to be
cut~ After the pattern is cut, the conveyor starts
up to advance cut parts out of, and fresh material
into, the cutting zone. Significantly gr~ater
throughput can be achieved by laser cutting the
patterns if ~he material never stops moving while
the cutting takes place.
The present invention is directed to
laser cutting patterns in a continuously moving
sheet of material. The method of cutting may be
characterized as cutting patterns in a moving
reference frame. The method and apparatus of the
present invention achieves significantly higher
throughputs than conventional ~top-to-cutn laser
pattern cutting machines because no extra time is
needed to move cut parts out of the cutting zone
and bring in fre~h material. Also cutting time is
reduced by moving the focused laser beam along the
conveyor axis in6tead o~ relying only on conveyor
movement.
The presen~ invention has particular
utility in cutting pa~terns o~ ~abric for mass
produced apparel. The advantage-~ of using a laser
to cut patterns in fabrio for garments include
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enhanced cutting accuracy, numerical control of the
cutting process, little waste, ease of change over
to different sizes or patterns and the ability to
cut all of the patterns for a single garment out of
the same section of cloth. The laser cutting
apparatus, however, can efficiently cut only a
limited number of layers at a time whereas other
pattern cutting devices, such as mechanical
cutters, can cut a large number o~ layers to enable
increased throughput. This may make them
economically competitive with laser cutters when
unit production, repeatability and unbundling are
not critical. By providing the ability to
continuously move material, the present invention
enhances the capability of laser cutters to compete
with conventional cu~ters by providing increased
throughput.
Although the present invention is
exemplified by laser cutting patterns in fabric for
clothing, it is not so limited. The present
invention i6 applicable to cutting patterns in many
types o~ continuously moving material where the
cutter, such as a focused beam of coherent
radiation, can be directed to traverse a repeatable
set of cut lines.
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The present invention is also directed to
a device ~or removing material from the conveyor~
When the present laser cutter i6 used to cut cloth,
the resultant patterns are highly flexible and
difficult to physically manipulate. The present
invention provides a device ~or easily and
conveniently removing material from the conveyor
surface.
II. De3criptio~ o~ th~ Prior Ar~
U.S. Patent No. 3,761,675 for a Material
Cutting and Printing System isæued September 25,
1973 to Hughes Aircraft Co. discloses a method and
apparatus for cutting material, especially ~abric,
using a focused beam of coherent radiation. An x-y
positioner under the control of a digital computer
scans the beam to cut a pattern in the material.
The computer al60 controls the lasers on-off
se~uence. The material is stationary while the
pattern is cut.
Laser cutters of the type disclosed in
U.S. Patent No. 3,761,675 have been sold by General
Systems Research, Inc. o~ Edmonton, Alberta,
Canada. These laser cutters use computer programs
to generate patterns and control the laser, x-y
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optical positioner and conveyor. Throughput has
been enhanced by using dual laser beams and two or
more seguential cutting zones. The conveyor tops
while the material is being cut by the laser.
U.S. Patent Nos. 3,811~554 and 3,828,697
for Working Surface for Radiant ~nergy Beam Cutter
issued ~ay 21, 1974 and August 13, 1974,
respectively, and U.S. Patent No. 3,828,159 issued
August 6, 1974 for Laser Cutting Surface disclose
honeycomb conveyor slats or ~urfaces which have
been used in the prior laser cutters dascribed
above.
U.S. Patant No. 3,832,948 for Radiation
Method for Making a Surface in Relief issued
September 3, 1974 discloses a method and apparatus
for making printing plates and other products with
an embossed surface by ~canning a beam of csherent
radiation over the surface. The on-off sequence
for the laser beam is controlled by a dig~tal
computer. The printing plate is stationary while
its surface is embossed by the cohexent radiation.
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III. Bum~ar~ o~ the Inve~tion
In accordance with the invention, a
pattern is repetitively cut by coherent radiation
incident on a continuously moving stream of
material. A conveyor continuously advances the
material through a cutting æone where an
electronically controlled x-y positioner traverses
ths pot where the coherent radiation is incident
on the material through a repetitive set of cut
lines. These cut lines, which ultimately define
the 6hape of the desired patterns, provide an
effici~nt way o~ cutting the pattern in a moving
reference frame; that i~, in a continuously moving
stream of material~ The terms ~continuous stream"
and ~continuous sheet~ are used interchangeably
throughout this description of the invention to
mearl material of inde~inite length.
A problem with cutting moving material is
that there is a possibility that the positioner
will try to ~ollow the material out of the cut zone
1~ the conveyor is moving too rapidly or too
810wly. The problem o~ the positioner drifting out
o~ the cut zone is eliminated, in accordance with
~he present invention, synchronizing the sequence
o~ cut lines with the conveyor speed so that the
positioner returns the beam o~ coherent radiation
to the same incident ~pot within the cut zone where
it began. To accomplish this result the beam is
directed to traverse a repeatable set of lines
defining a geometric 6hape, herein called a
s~mmetry unit, where the final spot is the starting
spot for the next repetition. And the conveyor is
controlled to advance the material so that these
two points occur at the same location within the
cut zone.
Starting and stopping at the Bame spot
has a furthsr advantage. The number of pattern
repetitions that are going to be cut is entirely
variable. Whether it is 5, 15 or 5,000, the
Btrategy used to define a symmetry unit must be the
~ame. Starting and stopping the set o~ cut lines
at the same spot allows the positioner to cut as
many repetitions as desired without drifting out of
the cut zone.
Since, in accordance with t~e present
lnvention, the conveyor and material move
continuously thro~gh the cutting zone, the x-y
positioner must compensate for the moving condition
ot the conveyor and maintain the same relative
veloai~y over the material regardless of the
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direction of motion. Even though the conveyor is
moving, the positioner is capable o~ automatically
adjusting its ~peed to accommodate the motion and
keep the cutting velocity constant with respect to
the material. ~hus the control ystem of the
present invention i synchronized to the conveyor's
movement.
As described in more detail hereinafter,
the laser cutter uses a ~equential set of cut lines
defining a symmetry unit whose geometric shape
represents the space between patterns. This
symmetry unit enhances cutting efficiency while
also obviating problems inherent to the process of
cutting in a moving referenced frame. Because the
conveyor is constantly moving while the cutting is
taking place there i~ a fini~e amount of time ~o
cut each individual line o~ the pattern. To be cut
a line must be pre~ent in the cutting zone. Also,
a line must be cut before it leaves the cukting
zone. The 6ymmetry unit compensates for this
problem by minimizing the total length of cut lines
and optlmizing their cutting sequence while
innuring that oaoh line c~n be cut while it is
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present in the cut zone. The ~ymmetry unit also
permits unlimited selection of the number of
repeated patterns to be cut.
The set of cut 1 ines within the 6ymmetry
unit traver~ed by the incident ~pot of radiation
defines the pattern cut in the material. The cut
lines selected for the symmetry unit, and their
sequenc~, therefore af~ects the capabilities o~ the
laser cuttPr. By reducinq the ~otal cut length of
a symmetry uni~, the ~ime required to cut a pattern
is also reduced, and the cutting process is made
more ef~icient assuming a constant cutting
velocity. Likewise, efficiency is enhanced by
properly ordering the sequence o~ cut lines within
a symmetry unit. Also common cut lines need be
traversed only once. Thu~ the present invention
uses the sy~metry unit to provide a more e~ficient
way of cutting a pattern or pattarns in a moving
sheet of material.
The symmetry unit of the present
invention represents the space between two or more
patterns. More particularly, the symmetry unit of
the present invention represent~ the minimum number
of lines which when cu~ repetitively will produce
the desired pattern in the fastest time. Since
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patterns are to be r~petitively cutl and ~ince they
are almost always irregular in shape, there is
always a certain amount of material between the
patterns. ~ather than cut the pattern the x-y
positioner causes the coherent radiation to cut the
spaces between patterns to create the desired
pattern. The result is the ~ame as traversing the
pattern itself but the efficiency o~ the cutting
process is enhanced. One reason for enhan~ed
efficiency is that the perimeter of the space
between the patt~rns is less than the perimeter o~
the patterns themselves. By cutting symmetry units
it is not necessary to cut out a complete pattern.
Instead the cut lines of a symmetry unit can finish
a previous pattern and 6tart the next pattern,
which is completed by the next repetition of the
symmetry unit. Another way a symmetry unit
enhances effi~iency is by minimization o~
~dryhaulN. Dryhaul is when the laser beam has to
be turned off to move the beam to a new part of the
pattern. Since the cu~ line~ in a 6ymme~ry unit
are closQr together than those of a pattern,
dryhaul is minimized.
The present invention also provides a
device for ef~ectively removing material from the
laser cutter's conveyor.
The convsyor surface itself must be
specially constructed for use with coherent
radiation. Generally, it must be constructed 80 as
to support the material for accurate cutting and
yet not to be damaged by the radiation. Prior
support surfaces have used pins. Hon~ycomb
surfaces have also been used to provide a cutting
bed. See U.S. Patent Nos. 3,811,554 and 3,828,159.
These ~urfaces, however, do not provide for ready
removal of flexible materials such as cloth.
The present invention uses a conveyor
~urface which i8 both suitable ~or use with
coherent radiation and cooperates with an apparatus
for ~acilitating the removal of the material.
Specifically, the conveyor sur~ace is defined by
spaced longitudinally aligned ribs which are
suitable for use as a outting ~ed for the in~rared
coherent radiation used by the laser cutter. The
ribs cooperate with an extractor plate which
includes a comb-like edge in inter-spatial
engagement with the conveyor ribs. T~e extractor
plate pre~erably engages the conveyor at an upward
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angle to the horizontal so that the pattern pieces
slide onto the extractor plats. The pieces are
drawn over the extractor plate by a conveyor
positioned over its surface. ~his conveyor draws
the pattern pieces onto and over the extractor
plate.
~r~f De~¢riptlon o~ the Drawing3
For the purpose of illustrating the
invention, there is shown in the drawings forms
which are presently preferred; it being understood,
however, that this invention is not limited to the
precise arrangements and instrumentalities shown.
Fig. 1 is a side elevational view o~ the
laser cutter of the present inventionO
FigO 2 is a top plan view of the laser
cutter except the laser is not shownO
Fig. 2A is an enlarged plan view of the
extractor plate.
Fig. 3 i~ an end view of the laser
cutter.
Fig. 4 is an enlarged sectional view of
the x-rail and drive motor taken ~rom the aircled
portion in Fig. 3.
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Fig. 5 is an enlarged partial view of the
x-y positioner.
Fig. S i~ a signal ~low diagram for the
laser cutter.
Fig. 7 illustrat~s a sleeve pattern as
presented on a video monitor.
: Fig. 8 illustrates the relationship
between nested, repetitive sleeve patterns.
Fig. 9 illustrates repetitive sleeve
patterns as they would appear on an video m~nitor
for creation of a ~ym~etry unit.
Fig. 10 illustrates the cut lines for an
exemplary symmetry unit.
Fig. 11 illustrates the co~mon lines for
the exemplary symmetry unit.
Fig. 12 illustrates an exemplary symmetry
unit.
Fig. 13 illustrates repetitive symmetry
units.
Fig. 1~ is a diagrammatic top view of the
x-y po~itioner and optical path.
- Fig. 15 is:a diagrammatic side view
illustrating the optical path.
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D~BOriP~iO~ of ~e Pre~erre~ ~mbo6iment
The laser cutt~r of the present invention
operates under control of a set of signals (i.e.
numeric control) defining the cut lines traversed
by the ~oherent radiation generated by the laser.
These signals, herein called a symmetry unit, are
created from pre-existing pat~ern graphical
information. It is known to electronically store
patterns in digital ~ormat. It is also known to
use available computer programs to position the
patterns to minimize waste (i.e. maximize the use
oP the cloth)O The pattern information sig~als
represent 6patial (x-y) coordinates which are used
to control position in existing x-y positioners for
stop-to-cut las~r cutter6.
: The process of defining a symmetxy unit
begins by displaying an existing pattern and then
re-ordering and re-seguencing the pattern cut lines
~or directing the laser to cut more efficiently.
The process o~ generating the symmetry
unit may be performed on an IBM PC or compatible
computer with an EGA/VGA color monitor. An IBM
PS/2 computer ~ay al80 be used. The operating
system must be DOS 3.0 or higher versions. DOS 3.3
is suitable. All graphical information (both
patterns and sequenced symmetry units) is ~tored in
the Computer Graphics Metafile (ANSI Standard
X3.122 1986). Grap~ical informa~ion may be
supplied by a Microdynamics or Auto-Cad program and
then converted to CGM format for subs2quent
manipulation into symmetry unitr-llumeric controls
for opsrating ~he laser cutter. The data
represents a set o~ coordinate points, velocity and
time.
The first step in the process is to
display an existing pattern: that is, a pattern for
which sequenced cut lines have not been created. A
typical pattern replica screen ~or a garment sleeve
ic ~hown in Fig. 7. The pattern i~ shown in
duplicate since repetitive patterns are to be cut.
For purposes o~ explanation, the pattern shown in
Fig. 7 is considered to be advancing as on a
conveyor from right to left, and out the left side.
The next step i5 to nest the two pattern
replicas shown in Fig. 70 This minimizes wa~te by
moving the patterns together along the conveyor
axi~. The patterns, under program control, are
moved only along the conveyor axis. Although it
could ~e provided in other circumstances, no
vertical or lateral movement of one pattern replica
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with respect to the o~her is allowed ~ince it is
assumed ~hat a tubular piece of cloth is being cut.
(The dotted lines represent the ~olded edges of the
cloth.) However, both patterns may be moved
laterally (vertically on ~he ~creen) in respect to
the conveyor. Fig. 9 shows the two nested
patterns. Specifically, the patterns have been
moved axially into abutment with each other.
The next step in the process is to
generate the symmetry unit, or more particularly to
select the cut lines included in a ~ymmetry unit.
As previously noted, a ~ymmetry unit is a minimal
set of cut lines of a nested pattern which enable
the laser cutter to cut repetitive patterns
efficiently, that is, in optimal time. Instead of
cutting the original pa~tern, the laser cu~ter cuts
all o~ the ~paces between patterns, thus creating
the original pattern. Moreover, a symmetry unit
does not ne¢essarily cut out a complete pattern,
rather it ~ay initially finish cutting the prsvious
pattern and start the next pattern, which i6
¢ompleted by the next repetition o~ the symmetry
unit.
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Symmetry units are explained in more
detail by reference to the drawings. Fig. 8 shows
a typical sleeve pattern. Since the pattern is to
be cut a number of times during a single run of the
laser cutter, repetitive illustrations of the
sleeve are ~hown representing repetitions o~ the
sleeve following each o~her along the longitudinal
axis of the tube of cloth. However, cutting
actually takes place at only one cut zone. Curved
lines are shown in straight line segments because
the pattern is built from a ~eries of straight
lines. Also the sleeve patterns are shown nested:
that is, moved into end-~o-end abutting relation.
The hatched lines highlight the space between
patterns.
Inspection o~ Fig. 8 reveals that it
makes no difference to the ultimate result whether
the laser cutter cuts each pattern or the space
between patterns. In the end, the desired pattern
i8 formed. However, there are significant
operational advantages to autting the space between
pattarns. The problems inherent in repetitively
auttin~ a moving piece of material are reduced.
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Fig. 8 illustrates how the symmetry unit
occupies less space than the pattern. Thus, there
is l~ss distance to be traversed while the cloth is
moving through a cut zone. A cut zone is the
operative area over which the laser cutter can scan
the beam of radiation. Inspection of Fig. 8 also
reveals that dryhaul i~ minimiz~d because of the
proximity of the cut lines to each other. Finally,
the problem of in~initely variable multiple
repetitions without dri~ting or chasing the pattern
out o~ the cut zone is resolved because ~uccessive
symmetry units can be linked to each other.
Specifically, the last point of each symmetry unit
can always be the first point o~ the next one, and
the geometric location of that point remains
identical. This is so even if a dryhaul must be
added at the end o* a cut in order to link the
symmetry unit to the next repetition. Movement of
the laser beam by the laser cutter's x-y positioner
is synchronized to the conveyor's movement to
assure first and last point identity.
Fig. 9 illustrates two nested patterns.
To create a s~mmetry unit, the minimum number of
cut lines to cut a complete pattern are selected.
A line may come from either the left or right
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pattern as long as every line in the pattern is
cut. The highlighted lines in Fig. lo illus~rate
the cut lines o~ a ~mmetry unit for the sleeve
pattern.
The ~leeve pattern used to exemplify the
present invention can be nested close enGugh
together that ~hey share 60me lines. Also the 8~W
line which separates one sleeve from the other
within a si~gle pattern is really two cut lines,
one for each sleeve. There are four such common
line segments in the example.pa~tern as shown in
Fig. 11 by the highlighting. One o~ each such
common or duplicate line segments may be removed.
~owever, not all common cut line egment~ should be
removed. For example, the two ~hort common line
segments extending to the ~dgelines of the cloth
should not b~ modified. The Iaser should be
directed to traverse these lines twice because
deleting one of the common lines will not improve
over all throughput o~ the laser cutter since the
x-y positioners will still have to travel ~ack over
these lines during cutting. Indeed, removing these
lines could actually increase cutting time because
the positioner must come to ~ complete halt to turn
off the laser.
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The procedural steps for identifying
common line segments in a group of cut lines is to
first examine each line selected as part of the
sy~metry unit, determine its shape, and pair all
lines of equal slope together. All other lines are
disregarded. The second step is to calculate the
y-intercept of ~ach line in a pair. If the y-
intercepts are equal, then the lines are co-linear.
All other pairs are disregar~ed. The third step is
t~ examine the end poin~s o~ the lines to determine
if they overlap. Three basic cases exist: (1) no
overlap; there~ore not a common line; (2) line
segments overlap; therefore there is a common line
sagment; (3) one line segment is completely inside
the second line segment; there~ors there is a
common line segment.
~ he ~equence of cut lines followed by the
laser is also important. Throughput is enhanced
not only by selection of a minimal set of nut lines
but also by ordering the sequence in which the cut
lines are traversed to be as ef~icient as possible.
The factors which affect cut line se~uence are:
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1. A continuously moving conveyor
provides the x-y positioners with only a limited
amount o~ time and work area in which to cut each
line.
2. Time wa~ted due to dryhaul further
res~ricts cutting time and influences the
sequ~ncing strategy.
3. The direction of cutting with
respec~ to the conveyor af~ects performance of the
laser cutter as well as overall cutting time.
4. A cut line must be cut be~ore the
material leaves the cut zone.
The ¢riterial sequencing of lines is
there~ore a~ follow~ The cut sequence 6hould
attempt ts traverse the cut lines which will be the
earliest to leave the cut zone. The symmetry
unit's cut lines generally should be seguenced left
to right: that is, against the direction of
movement of the conveyor. Dryhaul cannot alway~ be
avoided, but it should be reduced to a minimum.
Consequently, the se~uence should be from le~t to
right a~ long as it does not require any extra
dryhaul.
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The cut 1 ine sequence may be arranged in
any order 6elected by the machine ~Iser. The
choice, however, ~;hould follow the suggested
criteria for efficient laser cutting. ~qoreoYer, a
cut line may be ~elected once and only onceO
Traversing the ~ame cut line in opposite directions
is considered to be two cut lines. A programmed
algorithm 6uggests cut lines according to this
heuristic .
1. Look for an unselected cut line
which shares an end point with the f inal point of
the most recently selected line.
2. Look Por the closest unselected cut
line to the most recently selected cut line. A cut
line is considered ~closest~ by determining the
shortest distance from the final point of the last
cut line selected to the candidates ' end points .
3. Look for an unselected cut line
whose end point is closest to the origin. This cut
line will be the first to leave the cut zone.
The foregoing rules should be followed in
the order given but may be reversed.
The algorithm for selecting the end
points ia actually a selection of the direction in
which the cut iB to be made since the end point
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coordinates are already known as part of the
graphical data. ~he cut direction i~ therefore
determined by selecting the starting point. The
rule for ~election is to choose a~ the cut line
starting end point an end point that shares its
location with the last point of the previously
selected cut line, i~ any.
Fig. 12 shows the symmetry unit for the
sleeve patterns. Point 20 is both ~he start and
stop position.
As explained above, the x-y positioner
must return the laser beam to the same position
within the cutting zone where cutting began~ This
may necessitate adding a dryhaul (non-cutting line)
to the cut path. Whether a final dryhaul is
required is determined by comparing seyuential
symmetry units as shown in Fig. 13. A program
calculates the relative distance from the last
point 22 of the first symmetry uni~ to the ~irst
point 24 of the second symmetry unit. Point 24 i~
by dafinition the same as point 20. A dryhaul is
then added to link the two units. Thus, the x-y
positioner 66 will star~- and end its motion at the
same point relative to the symmetry unit.
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To synchronize the start-stop point to
the conveyor, it is nece~sary to determine conveyor
velo~ity. If the time to trace a symmetry unik is
t, and the absolute distance from the start point
to the end point is ~, then the conveyed material
velocity is s/t. By advancing the conveyor at this
velocity, the laser cutt r can cut any selected
number of symmetry units without leaving t~e
cutting zone.
In order to control the physical natura
of the cut or kerf actually made by the laser, the
laser should always traverse the material being cut
at a con~tant velocity. Thus, the power of the
coherent radiation on the material remains
constant. The conveyor i8 set to move at a
constant velocity. Accordingly, the x-y positioner
slows down in the x-direction when cutting against
the direction of the conveyor motion. It has to
speed up when cutting in the direction of the
convey~r motion. Hence all cutting should be done
against the direction of the conveyor's mo~ion to
tho extene po~sible.
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Figs. 1, 2 and 3 illustrate the laser
cutter apparatu6 60 of the present inventionO
Laser cutter 60 includes a rigid super structure
62, a conveyor 64, x-y po~itioner 66, exhaust
system 68 and laser 130.
Super tructure 62 is mad~ to ~upport the
optical positioner, laser an~ conveyor in as near
Yibration ~ree relation as possible for accurate
cutting. It includes vertical columns 70 and 72 at
spaced intervals. Columns 70 a~d 72 are visible in
Fig. 3. Super structure 62 also includes
horizontal cross-pieces, such as cross-piece 74,
joinin~ horizontal side-pieces 76 and 78. Columns
and cros~-pieces are braced by trusse6, such as
trusses 80 and 82. ~ubular steel and I-beams are
used ~or the super structure to provide rigidity.
The rails for the x-y optical positioner
66 are rigidly mounted on cross-pi~ces 84 and side
pieces 86, 88 welded to support pieces ~0 mounted
in the columns.
Convsyor 64 comprlses rectangular slats
~2 hingedly ~oined to the conveyor. The con~eyor
i~ supported by slides (not shown) and rotatably
mounted pulleys 98, 100 at each end o~ the
conveyor. The conveyor is driven by chains ~4, 96
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passing over sprockets 102, 104, 106 and 108.
Sprockets 102, 108 are driven by an a-c electric
motor (not show~).
Each o~ the slats comprises a set of
elongated ribs llo aligned with the longitudinal
axis of the conveyor. Ribs 110 are made o~ brass.
Brass is chosen because it re~lects the coherent
infrared radiation (wavelength 10.6 microns) used
in the laser cutter 60. 8rass is also selacted
because it has good heat transfer properties.
Copper may also be used. The ribs are mounted with
one side edge at the support surface of the
conveyor, and are spaced apart 0.375 inches ~or
extraction of the cut pieces as hereinafter
explained. Each rib i~ .025 inches thick.
Exhaust 6ystem 68 provides hood 114 below
the conveyor ~or drawing gaseous emissions away
from the cutting zone.
x-y positioner 66 comprises y-rail 116
upon which is mounted carrier 142 supporting
~ocusing optiaal systems 118, 120, and adjustable
45~ mirrors 122, 124 for directing and focusing
dual beams of coherent radiation on the material
tran~ported by the conveyor 64. Dual beams are
used so two patterns can be cut at once.
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Adjustable mirrors 126, 128 mounted on the y-rail
at 45 to the longitudinal axis of the conveyor
re~lect the coherent radiation to mirrors 122, 124
mounted on carrier 142.
The ~ource of coherent radiation i~ laiser
130 mounted to the top of super structure 62.
Laser 130 is a dual beam CO2 CW Liaser. By way o~
example, laser 130 may be a ~odulase 800 C02 CW
Laser available from GSR Technologies, Ltd. of
Edmonton, Alberta, Canada. Thiis laser produces two
beams of infrared radiation at a wavelength of 10.6
micron~ at a rated power of 400 watts. Each beam
at the output coupler is 7.5 mm with a divergence
of 1.8 mrad.
As shown ~chematically in Figs. 14 and
15, the two coherent radiation beams 132 and 134
genorated by laser ~30 are reflected downwardly by
45 mirrors, only mirror 136 being ~hown. Mirrors
138 and 140 located toward the feed end of conveyor
64 dir~ct the radiation beams horizontally and
axially toward mirrors 126 and 128. Mirror~ 12~
and 1~8 direct the light parallel to y-beam 116 to
mirrors 122, 124 which direct the radiation through
the focusing optlcs 118, 120 to the conveyor
~ur~ace.
.
; , . :. .: . ~ : :: . , , - : : : .:
., . . . . ,: : : . , . - .. . .: .. . .. . . . ,: ..
. .. . - ~ . .
-- 28 --
As shown in Fig. 3, the 45O mirr~rs 122,
124 and ~ocusiny op~ics 118, 120 are mounted on the
carrier 1~2. Carrier 142 i8 slidably engaged with
and supported by y-rail 116~ Carrier 142 also
supports y-mo~or 1~4 whose output ~haf~ 145 drives
pinion 147 engaged with the rack 151 fixed to y~
rail 116. See Fig. 5. The mo~or 144 moves th~
carrier 142 along y-rail 116, and hence shiPts the
coherent radiation transversely or across the
conveyor surface. Such transverse motion may als~
be re~erred to as the y-direction.
Movement along the conveyor's
longitudinal axis is accomplished by moving the y-
rail 116 along the x-rails 117 and 1~9. As shown
in Fig. 4, y-rail 116 iB movably mounted on x-rail
117 by slide 146. x-rail 117 i joined to angle
piece 148 which is fixed to side piece 88. x-rail
119 is attached to side piece ~9. Both x-rails
117, 119 extend along the conveyor a sufficient
length so that y-rail 116 can be traversed over the
full length of the outting zone, which may be by
way o~ example 60 inches. y-rail 116 also supports
x-motor 150 whose output shaPt 152 drives pinion
154. Rack 156 i~ mounted on angle piece 148 and is
engaged by pinion 154. Thus, x-mo~or 150 moves y-
.` ' ' ~ '' , . ' ., ' .. ' ' ` ' ' ' ,
-- 29 --
rail 116 to any desired position along thelongitudinal axis o~ the conveyor, just as y-motor
I44 moves the carrier 142 to any desired transverse
position along the y rail. Bo~h motors,
functioning under control of the electronic x-y
controllers de cribed herein, ~unction to cause the
coherent radia~ion to cut material on the conveyor
surf~ce. The sequence o~ cut lines followed by the
coherent radiation is, in accordance with this
invention, a ~ymmetry unit.
Fig. 6 ~hows the signal ~low for the
laser cutter 60. The geometric pattern
information, that is the symmetry unit machine
control information, is loaded into computer 160.
By way of example, computer 1~0 may be a Zenith
380/40 computer with a IBY 7534 touch Gcreen
monitor. The control information represents
graphiaal data (i.e. coordinate points for the cut
lines in a symmetry unit). It also includes
velocity information based upon the physical
limitations o~ the laser cutter 60. Specifically,
velocity is calculatad ba~ed upon the maximum
acceleration of the moving elements o~ the x-y
.... . .. : : :: :. :.- .: : . . . - . . : .
- 30 -
positioner 66 and the properties of the material to
be cut. Thus, each cut line is in fac~ a vector in
that it has bo~h dlrection and magnitude.
The x~y positioner operate~ under the
control of the Smart Motion Control Card (SMCC) 162
available from Delta Tau Data Systems Inc. of
Canago Park, CA. The conveyor operates under the
control of the SMCC 164 available from the same
manufacturer. Each SMCC conver~s digital data
provided by the computer into command ~ignals ~or
driving the x-motor 150, y-motor 144 and conveyor
motor 166. SMCC 162 provides both x-axi~ and y-
axis control for the x-y positioner. SMCC 164
provide6 only x-axis control for the conveyor.
The ~pecific digital data from computer
160 (the command signals) comprises for each cut
line vector:
- 1. the end position for the x-motor and
y-motor (which together define the end position for
the beam of coherent radiation~:
2. the x-motor and y-motor end
velocity:
3. the time to get to the end position.
Thase command signals are processed by the SMCC
cards.
.
.. , .~ .. . . , ., ~ , . . . . .. .
~ - }
- 31 -
Once a ~mmetry unit has been sequenced
an~ the ~inal dryhaul added (if nec~ssary), this
cutting info~mation is translated into numeric
control commands unders~andable by each SMCC. In
addition to the geometry of each vector, these
numeric control command~ also contain velocity and
timing information used to control the positioner.
Motion information such as maximum acceleration,
cutting velocity, laser dwell time and tube overcut
are dependent on the target material and are added
to the pattern data at cut time. The individual
vectors or cut lines of a pattern are described in
numeric control commands by acceleration, constant
velocity and ~eceleration move commands to insure
that the x-y posi~ioner does not exceed these
limits. I.aser beam on/of f commands are added to
insure that the laser comes on at the right time.
once the numeric control data ~or the
symmetry unit are provided, the conveyor velocity
is set to insure that the positioners will return
to the same location within the cut zone. The
computer controls the starting and stopping of the
machine, but the SMCC's is responsible for the
movement of the x-y positioner along the cut path.
- 32 -
The output o~ SMCC 162 includes x-axis
control signals for x-axi~ vel~city control unit
(VCU) 168 and y-axis control signals for y-axis
velocity control uni~ (VCU~ 170. These are x-axis
and y-axis velocity status control signals.
Speci~ically, ~he x-axis and y-axis control ~ignals
control each VCU'~ amplifier and hence the
frequency and voltage for energizing the x-motor
150 and y-motor 144. Each SMCC 162 functions as a
servo-controller. The x-motor 150 and the y-motor
144 are a-c motors and are each coupled to an
optical encoder 172 and 17~, respectively. Each
encoder 172, 174 feeds back a pulsed motion signal
(e.g. 2,000 pulse per 360 revolution o~ the motor)
to its respective VCU and to the S~CC 1620 The
SMCC r~ads the encoder ~eedback signals, which
represent where the beam of radiation is on both
the x-axis and y-axi~. The SMCC calculat~ where
the beam should be based on the command signals.
The SMCC then generates frequency and voltage
command ~ignals which ara converted into actual
chan~es in frequency and voltage to con~rol the
velocity of the x-motor 150 and y-motor 144.
- 33 ~
The x-y positioner is synchronized to the
conveyor. SMCC 164 controls the conveyor's
velocity. Conveyor velocity is adjustable to
provide sufficient time to cut each pattern.
However, the select~d csnveyor velocity is
maintained constant while the x-y positioner is
tracing a symmetry unit, and each repetition
thereof. As with the x-y positioner, the conveyor
is driven by an a-c motor 16~ coupled to an optical
encoder 176 whose resolution is also 2,000 pulses
per 360. The output signal of encoder 176 is fed
back to conveyor VCU 178 and also ~o both conveyor
SMCC 164 and x-y positioner SMCC 162. As thus
con~igured, SMCC 164 maintains the conveyor at the
constant velocity selected for the particular
symmetry unit being cuk. Thus, accuracy in
returning the x-y positioner to the same starting
point for each repetition of a symmetry unit is
provided.
Computer 160 also provides on-off control
signals ~or the laser 130 as is required for
dryhaul.
As best shown in Figs. 1, 2 and 2A, the
extractor device 180 for removing cut pieces from
conveyor 64 aomprises extractor plate 182
- 34 -
positioned at an acute angle to the horizontal.
Extractor plate 182 includes a planar extension
plate 184 and integral teeth 186 extending in
comb like fashion across the receiving edge o~ the
extractor plate. Teeth 186 are positioned so that
the ribs 11) in each conveyor slat pass betwee~
them. ~hus, each pattern piece is literally combed
from the conveyor onto the extractor plate.
The extractor plate 182 is supported on
slides tnot shown) so that it may be adjustably
positioned between khe ribs 110 or even removed
therefrom.
Removal of the pattern pieces is assisted
by the extractor conveyor 1~8. Extractor conveyor
188 consists o~ a conveyor frame 190 supporting a
driven and idler roller upon which are carried
æpaced belt~ 192 which engage the pattern pieces
and pull them over the extractor plate. There are
16 belts regularly spaced across the width of the
conveyor. Sprockets are driven by chains 94 and
96. Sprockets 194 are ~ixed to the same shaft as
the chain driven sprockets and drive chains 196
which drives ~prockets 198 ~ixed on the shaft for
the drlven roller, thus driving the belts 192.
Gearing ~or the sprockets is sek to move the belts
.
,
- 35 -
192 at a lightly faster velocity than the
conveyor; e.g. 1% ~aster. Thus, the pattern pieces
are moved away from the conveyor for collection and
further processing.
The extra¢t~r plate in engagement with
the elongated, longitudinally extending ribs 110
provides an ef~ective way to remove cloth and other
flexible materials from a conveyor which also
serves as an e~fective cutting bed for a laser
cutter,
The present invention may be embodied in
other specific forms without departing ~rom the
spirit or essential attributes thereof and,
accordingly, reference should be made to the
appended claims, rather than to the foregoing
specification, as indicating the scope of the
invention.
.
... . ~.. . . . . I ~ . .. . - . .. . . . . . ..
