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Technical Guide: How to Match Today's Laser Cutting
Technology to Application Requirements
By Markus Klemm,
R&D Software Engineer, Spartanics
Laser cutting,
a.k.a. digital die cutting, uses high-powered lasers to
vaporize materials in the lasers’ beam path. The powering
on and off of the laser beam and the way in which the beam
path is directed towards the substrate effects the specific
cuts that the artwork requires. Because cut away parts are
vaporized the hand labor or complicated extraction methods
otherwise needed for small part scrap removal is eliminated.
These basic facts
about laser cutting are as true today as they were when
laser cutting systems were first put to practical industrial
uses in the ‘80s. However, recent advances in laser cutting
technology, and especially those that relate to the
sophistication of the software engineering underlying laser
cutting controls, have created dramatic improvements in the
type of outputs that can be expected from laser cutters.
Today’s lower cost laser cutting systems made from less
expensive components have far superior capabilities to the
expensive systems that were designed and engineered only a
few years ago. At the top end, state-of-art laser cutting
systems are able to consistently cut far more intricate
designs in a wider range of substrates and with tighter
tolerances than ever before.
The challenge to
those making investments in laser cutting technology is to
source machines that are well-matched to application
requirements. One can still find laser cutting systems in
the marketplace that force compromises in quality or
production output that should not be brooked in light of
engineering advances in laser cutting technology. On the
other hand, those with more straightforward application
requirements are often well-served by lower cost models of
laser cutting systems that are powerful and versatile enough
for the jobs at hand. In this white paper, we will discuss
how to match today’s laser cutting technology to application
requirements and offer insights into how various features of
laser cutting systems translate into capabilities for
quality and throughput as summarized in Figure 1 – Laser
Cutting Technology Comparison Chart.
Choosing Between Laser Cutting vs. Tool-based Die Cutting
Systems
A preliminary
step to sourcing the right laser cutting technology is to
first determine if laser cutting capabilities are a good
addition to your finishing department.
There are
numerous advantages to laser cutters as compared to
tool-based die cutting systems. Most of these advantages
derive from the tool-free nature of laser cutters. Because
there are no tools, there are no costs for tools or
production delays for time to make tools. This is the major
reason why laser cutters provide a rapid prototyping niche
for those that use them. Laser cutting systems are called
digital die cutters because they can take any vector-based
digital image and import it into their operating software to
set up a job. Today’s best-in-class laser cutting systems
can complete set up from these imported digital images in
just a few minutes. The ‘digital die cutter’ term that is
used interchangeably with laser cutting speaks to this
advantage that tool-free cutting systems provide, especially
when used in combination with digital printers. This
combination allows one to move from artwork to finished
product in just a few hours, or even less for very short
runs.
In tool-based
mechanical cutting there are always intrinsic limitations
from the physical contact between the cutting edge and the
material being cut. A laser cutting systems bypasses that
situation, which makes them able to cut many materials that
are very difficult or impossible for tool-based cutting
systems to handle. For example, cutting adhesives is far
easier with laser cutting systems because of the tendency of
adhesives to literally gum up the works in mechanical
cutting systems. Similarly, the ability of tool-free laser
cutting systems to reliably handle thin substrates is a big
advantage. In these thin substrate applications,
cut-to-print registration is not constrained by the physical
limitations of weighty dies interacting with flimsy
substrates. Another example is in the better handling of
abrasive materials, which literally wear mechanical dies
down such that cutting abrasives with mechanical cutting
systems is often prohibitively expensive because dies have
to be continuously replaced. Here too, tool-free laser
cutting systems sidesteps this problem altogether.
The relative ease
with which laser cutting systems create special features is
also a considerable advantage. Perforations, score lines,
kiss cuts, consecutive numbering, creasing, personalizing
and other special features are done as a matter of course by
laser cutting systems. This is especially the case with
today’s laser cutting technology that uses far superior
software engineering to precisely control the movement of
laser beams making cuts. In fact, the only relevant
physical limitation in laser cutting systems is the width of
the laser beam--- for example in 200mm x 200mm working
fields or greater the spot size can be as small as 210
microns in best-in-class systems. While any die-based
cutting system would have difficulties in producing corners
that are less than 30 degrees, this is not in any way
challenging for a laser cutting system. And, laser cutting
technology also allows one to skip the step of creating
mechanical knicks to facilitate parts extraction as is
typically required with a tool-based cutting mechanism.
There are
limitations to laser cutting systems, as with any
technology, but also there are mistaken notions as to what
these limitations are. In some quarters laser cutters are
thought of only as prototyping tools and not up to the
requirements of full production runs. While there are many
applications where laser cutting may be slower as compared
to platen presses, rotary die cutters or
optically-registered gap presses, they are considerably
faster than the earlier laser cutting systems that used to
predominate. In fact, most users of today’s laser cutting
systems ARE using them for full production line
capabilities. For one thing, today’s laser cutters are
generally galvo (galvanometer) type lasers that make minute
adjustments in mirror angles to move laser beams around
artwork. This galvo mechanism is considerably faster than
gantry systems with XY plotters that physically move lasers
as a whole or the whole sheet of material being cut, not
just the laser beams. Newer galvo technology takes this
speed improvement to the next level by fine tuning software
to shave milliseconds off of most operations, with a
combined effect of significant speed improvements. The
higher the wattage of the laser, the faster the cutting
proceeds in most applications. The difference today is that
faster 200-watt and 400 watt lasers that were prohibitively
expensive five or so years ago are now available at
competitive prices. These new lasers also make a higher
quality laser beam, which in turn ensures that cutting
quality is maintained even at higher cutting speeds. The
upshot of all these combined speed improvements is that
today’s laser cutters do far more than prototype samples;
they are used for full production runs without creating
production bottlenecks. (Note: Manufacturers’ claims on
linear cutting speed are not meaningful in most instances.
Actual cutting speed is determined both by the complexity of
the artwork and ability of the control software to optimize
cutting in that geometry, as explained below.)
Another
misconception that one still finds is that laser cutting is
a dangerous operation that burdens a workplace with safety
risks. Though it may seem counterintuitive to some, laser
cutting systems are in many ways a safer alternative to
tool-based cutting systems. The initial installation of a
laser cutting system takes care to eliminate the chance of
stray beams creating workplace hazards if workers do not
wear safety glasses. Tool-based systems, on the other hand,
pose a continual risk of severe worker injury if they are
not operated properly. Although such accidents are rare,
they can be catastrophic. Costly injuries to tooling are
somewhat more common, such as when technicians leave tiny
screws in a cutting area that end up destroying the custom
tooling.
It is also
thought, and correctly so, that laser cutting systems cannot
handle any and all substrates. However, the boundaries of
that limitation continue to shift along with better
engineering of laser cutting technology. For example,
polycarbonate substrates used to be beyond the reach of
laser cutting technology because of the laser cutters’
tendency to leave poorly cut edges with a heavy brown
discoloration on the substrate. This is still true of the
thickest polycarbonates, but not so with the thin
polycarbonate substrates that older systems couldn’t
tackle. (Note: Unfortunately one can still find laser
cutting systems in the marketplace that leave edge
discolorations on thin polycarbonates, but there is no
reason to settle for this substandard technology.) Many
still think that PVC (polyvinyl chloride) is not a good
match with laser cutting technology, but that notion too is
a bit out-of-date. It is possible to cut PVC materials so
long as additional components are added to protect the
existing machine components near the laser beam from the
corrosive action of PVC cutting byproducts and that
appropriate filtering systems are added to protect operators
from noxious fumes.
The real
disadvantage of laser cutting technology – and the reason
that most companies that use laser cutters do so in
conjunction with one or another tool-based cutting system—is
that it is less cost-effective for many relatively
straightforward long run applications which are not beyond
the reach of mechanical cutting. If part geometries are
easy for a physical tool to achieve, if the substrate is not
too thin, too sticky, too abrasive or in some other way
troublesome for a physical die, and especially if it
involves a relatively long run length where the cost of the
die becomes a negligible factor, tool-based cutters (platen
presses, rotary die cutters, electro-optically controlled
gap press technology) often prove the better finishing
tool.
Quality and the Soft Marking Standard
Laser cutting
systems that were engineered just a few years ago were often
not up to the challenges of cutting complex designs,
especially when there were many sharp angles in the artwork
geometry. One can still find inferior laser cutting systems
being sold today that similarly are plagued by the quality
problems usually evidenced by pinholes at the start and stop
of cutting sequences or burnthroughs. For example, Figure 4
shows the difficulties that less sophisticated laser (see
PDF copy) cutting machines have whenever turns are required
in sharp edges. Here you can see the telltale black
burnthrough marks at turning points that show points where
the lasers lingered too long in that spot. One might think
of the analogy of a car making a turn, and the usual need to
decelerate in order to make the turn. Here the deceleration
of the laser beams was so pronounced that it burned through
at critical turning points.
Figure 5 (see PDF
copy) shows a laser cutting machine that has just the
opposite problem. In attempting to avoid the burnthroughs
shown in Figure 4, the lasers were accelerated. However,
the control of this acceleration was inadequate. Instead of
the sharp corners that the artwork requires, the edges are
rounded. Here, the laser beams are moving too fast to make
the sharp corner details.
 Improvements
in the software engineering of today’s better laser cutting
machines obviate these historic quality problems. Soft
marking, where the laser movements are better synchronized
with artwork geometry and tightly controlled during the
entire cutting sequence eliminate the burnthrough problems
yet make the sharp angles required, as show in close-up in
Figure 6 (see PDF copy) and in the finished product Figure
7. Older systems often left pinholes at the start of a cut
because of the time it took to move the scan head (mirrors
directing the laser beam) off from that initial start
point. In contrast, the better quality laser cutting
systems of today create better edges, don’t leave pinholes
at the start of cuts, don’t leave burnthroughs at sharp
corner turns. This is not because better lasers are used
but rather because better algorithms improve control of the
movement of the mirrors that point the laser beam. Soft
marking is no small feat for the control software of laser
cutting systems to achieve, and it is only the manufacturers
of laser cutting technology that have made significant R&D
investments in better software engineering that can deliver
the defect-free soft marking that most applications require.
To example how
cutting speed potentially affects quality, consider Figures
8, 9, 10 and 11 (see PDF copy) showing the laser cutting of
a small folded box. In Figure 8, the frequency of the laser
output is so slow, 10 kHz, that the single pulses of the
laser give the cut more the appearance of a dotted line as
opposed to the continuous line cut that is desired. Figure
9 shows a laser cutter without algorithms for optimizing the
laser movement to geometry and cutting speed when it is
operating at a fast cutting speed. Here the cutting speed
is too fast for the scan head mirrors to follow the contours
of the artwork in a synchronized way. What results is not
exact. Contours that should be sharp are rounded. What you
are looking at is the output of a less sophisticated laser
cutter where the mass of the scan head mirrors and what it
takes to move this mass are not adequately handled by its
software. These problems are even more pronounced when the
cutting speed is doubled as shown in Figure 10. In
contrast, laser cutting systems that can match the cutting
speed to the part geometry and optimize the powering on and
off of lasers accordingly is shown in the greatly improved
quality output of Figure 11. Here, the algorithms the laser
cutting software is using can match the speed of cutting to
the design in an optimized fashion.
Improved quality
in today’s better quality laser cutting systems is seen not
only in better edge quality but in the far more consistent
cut-to-print accuracy afforded by the new level of systems
integration in the best-in-class laser cutting machines.
For example, earlier systems had no way to compensate for
the rotation in the working field that can occur as the web
moves through the laser cutting machines. Today’s
best-in-class systems not only use high resolution cameras
but also integrate the camera information with the laser
software that is controlling cutting. This means that as
the camera systems determine any X/Y offset values, they
communicate these to the laser control software, which is
adjusted accordingly. If a laser cutting machine does not
integrate inputs from a camera system to the laser cutting
controls it does not have a way to make needed corrections.
Tight systems integration where one component (the camera)
communicates with another (the scan head) is key to the
higher quality output of today’s best-in-class laser
cutters.
The quality of
the laser source itself will also have bearing on the
cutting quality possible. Better lasers with smaller spot
sizes (e.g. 210 microns) will facilitate crisp cuts, IF the
control software uses advanced algorithms to move the better
shaped and smaller sized beam along. Better quality lasers
combined with advanced laser control software will also
avoid the excess heat that can literally muck up the works
in label applications where excess heat can melt adhesives
onto release papers making it difficult to automatically
remove labels from the release papers in subsequent
production steps.
The type of laser
tube one a system uses—open or closed—will also have bearing
on how the laser can be controlled and how this affects cut
quality. Although open unsealed lasers are getting better
in quality they are still rarely up to the demands of many
applications. There are several intrinsic problems with an
open laser tube design. CO2 is usually one of several gases
in a laser tube, with helium, nitrogen and hydrogen making
up the balance. The proportion of each of these gases in
the mixture will affect the laser power. This ratio is apt
to shift in an open laser tube design. With open tube
designs there is a requirement to frequently change one open
laser tube CO2 tank for another. This makes it is nearly
impossible to save settings because there almost always is a
difference in gas mixture ratios from one CO2 tank to
another. These shifting ratios affect how the laser powers
and the quality of its cut. To achieve the same quality cut
an operator will need to fuss with adjustments every time
they switch tanks, and even then, there will likely be
variations. In contrast, the sealed laser tubes are not as
likely to change in gas ratio composition and only require
replacement every 10,000+ hours of operation. This
translates into a much better ability to control cutting and
to get a consistent result.
Cutting Speed vs. Web Speed
Today’s laser
cutting systems are faster for a variety of reasons. One is
that higher-powered lasers that cut faster are more
affordable, such that most users of laser cutting technology
today opt for 200-watt+ systems. Secondly, the more
sophisticated algorithms used in today’s better quality
laser cutting machines are able to shave milliseconds off of
each cutting operation, which cumulatively result in faster
cutting speeds. The third and most important reason why the
better quality laser cutting machines of today are faster is
that they are able to better optimize the cutting sequence
resulting in much faster web speeds.
To illustrate the
impact of software that can optimize for web speed see the
first example of the US map shown in Figures 12 and 13 (See
PDF copy attached). In each figure the blue dotted lines
show where cutting has stopped while the laser repositions
for a next cut. In Figure 12 a cutting sequence is shown
where there is absolutely no optimization done by the
software on how the cutting sequence should proceed. In
such non-optimized cutting, the path follows the lines of
how the vector drawn image was first created in Solidworks
or equivalent software. This non-optimized cutting sequence
is so slow that the web would only be able to advance
intermittently. In Figure 13, we see a significant
improvement in web speed that is done automatically by the
sophisticated algorithms in the control software. This
improved web speed is determined during the setup of the
job, before it is run. A second step in the web speed
optimization during job set up is shown in Figure 14 and 15,
where the maximum web speed is 17% higher and is achieved by
splitting the single image of the US map up into two
separate images, and optimizing the web speed for the split
image. This optimization is also done automatically by the
software. In fact, the software can tell the operator
whether it is best to cut the geometry as a single image,
two images, four, etc. Today’s better laser cutting
technology can seamlessly stitch these multiple images
together, which is done in this case to maximize web speed,
and in other cases to allow for cutting a design with
dimensions longer than the width of the laser cutter’s
working field.
 It
is important to not be confused by various manufacturers’
claims on cutting speeds, as this is not particularly
relevant to the actual web speed in most applications, which
is the all important consideration in actual production.
Figures 16 and 17 showing a scalloped edge design created
with older technology that cannot optimize for web speed and
the same scalloped edge design created by today’s better
laser cutters that CAN optimize cutting sequences for web
speed. Note that the marking speed (a.k.a. cutting speed)
is 0.6 seconds in both cases. However, the cutting sequence
that is not optimized for web speed proceeds at
approximately 9% of the web speed shown in Figure 17, where
the cutting sequence is optimized for web speed.
Figures 18, 19,
and 20 (depicting the cut of three rows of Spartanics logos)
(see figures in PDF) show further examples of how
non-optimized cutting compares to cutting that is only
optimized for maximum cutting speed vs. cutting that is also
optimized for maximum web speed. In Figure 18 the cutting
sequence is not in any way optimized for speed, but instead
proceeds along the lines of how the artwork was originally
drawn. This is the worst case scenario and examples how
more primitive laser cutters without software improvements
of any kind operated. In this case this means that the
cutting proceeds at 37% of the cutting speed achieved as
that show in Figure 19 where the cutting sequences are
optimized for the fastest cutting speed. Until recently,
this was the best that laser cutting machines could do.
Now, the state-of-art algorithms in today’s better quality
laser cutting machines take this to the next step by
figuring in the adjustments in the cutting sequence that
would need to be done that take web speed into account. If
the web is moving from right to left this means, for
example, that the geometry details on the far left need to
be cut first and that the way in which the scan heads are
moved will depend on the web speed being used. This is
shown in Figure 20 (see PDF copy attached), where the
cutting sequence is also optimized for web speed, not just
cutting speed, such that a 350% faster web speed is
achieved. Thus, optimizing for cutting speed alone can
result in slower web speeds and buyers of laser cutting
systems are well-advised to ignore manufacturers’ claims re:
cutting speeds and instead focus in on demonstrations of the
ability of the system software to optimize for web speed.
These web speed optimizations are done automatically by the
better quality laser cutting systems and do not require any
operator training.
The more
sophisticated software algorithms in today’s better quality
laser cutters that optimize for web speed also give an
unprecedented ability to continuously laser cut pictures
that are longer than half of the working field. Obsolete
models of laser cutters that can only optimize cutting for
cutting speed, and not web speed, restrict the sizes of
pictures to be cut to be no larger than half the size of the
working field. These same algorithms that optimize for web
speed also eliminate the need for up to 90% of the hard cuts
and quality issues that arise when you try to stitch two
images together. They do this automatically, in contrast to
obsolete models of laser cutting machines that require
operators to manually reset the cutting sequence to avoid
hard cuts in the artwork.
Fallacy of the Double Scan Head Advantage
Another area that
can get confusing to those who do not understand the
specifics of laser scan head design is the use of so-called
double scan head systems in hopes of accelerating cutting
speed. These higher-priced double scan head laser cutters
are actually at times no faster or even a tad slower than
single scan head laser cutters that use higher wattage
lasers coupled with more sophisticated algorithms in the
laser control software. Although it might sound good, i.e.
the idea of using two lasers at once to double your
production speed, this both creates significant quality
issues and cannot truly double speed because of the physical
constraints of putting two laser scan heads next to each
other and the compromises that this forces one to make.
 When
you are stitching two halves of the web width together, it
is often possible to have more parts on one side of the web
as compared to the other side, as shown in Figure 21. In
such a scenario, with a double scan head machine you will
lose web speed because the laser on the overloaded side will
cause a slower web speed. To solve this problem,
manufacturers of double scan head systems usually position
the two laser scan heads as close together as possible
across the web width to create the greatest possible overlap
between their two cutting fields.
However, for
wider material there is always an interplay between the size
of the scan heads, how closely they are positioned together,
the spot size that results, and the extent to which there is
overlap in the cutting area of the two scan heads and the
related stitching involved. If the scan heads are large
such that they cannot be placed very close together, there
will be less overlap in the cutting area and more need to
stitch, which is an eventual challenge to quality, as shown
in Figure 22 (see PDF). Alternately, if small can heads are
used and positioned closely together, there might be a
greater overlap in cutting area but the spot size would need
to be much larger, as much as 280+ microns, which is also an
eventual challenge to quality. A third option, which also
undermines quality, would be to use small scan heads
positioned a distance apart for a smaller spot size, but
again creating a need for stitching because there is a much
smaller overlap in the cutting area, as in Figure 23 (see
PDF copy).
Another
constraint is that there are always areas beyond the reach
of the other laser scan head, as shown in Figure 24 (see PDF
copy attached), which means that you must contend with the
difficulties of stitching two objects together that have
been cut by different scan heads. This ALWAYS means some
compromise in quality, because different scan heads will
have different temperatures resulting in different drifts
during operation. Realistically, there are very few laser
cutting applications that are forgiving enough for the
quality issues that such stitching engenders. It is not
only applications with stringent cut-to-print registration
requirements that are challenged by stitching the cut images
from each of the dual scan heads. For example, if there is
an offset of the two cut parts by more than +/- 0.1 mm this
can create a knick during waste removal due to the
misalignment during stitching.
Thus, the higher
cost of double scan head systems is not justified especially
if one compares these systems to single scan head laser
cutters that are designed for cutting at higher speeds.
Double scan head systems often cannot use the 200 –210
micron spot size lasers that avoid the excess heat which can
cause problems such as burnthroughs, adhesives sticking to
release papers, etc. Moreover, the costs for higher wattage
single scan heads is considerably less than the dual scan
head designs, yet the production speed they afford is
typically the same or a bit faster.
Systems
Integration, User-Friendliness and Production Output
The quality
improvements that are possible when high resolution camera
systems communicate to scan head control software to
determine required X/Y offsets is only one example of the
benefits of systems integration in top quality laser cutting
machines. The extent of systems integration in one or
another laser cutting system can largely determine how
user-friendly they are to operate and has great bearing on
the production outputs that can be achieved. For example,
older systems required users to obtain a separate camera
system, and required operators to additionally master the
camera control software. In contrast, today’s better
quality laser cutting systems come with cameras fully
integrated with the laser software. Operators do not have
to learn set up of a separate camera system, as this is now
done directly from the laser control software, and in the
best-in-class systems only takes three simple steps.
The better
quality laser cutting systems with full integration of all
systems components are in fact the only laser cutting
machines one can find in the market today that work
seamlessly with variable images from digital printers.
These better quality laser cutters allow one to create laser
jobs with multiple pictures with different geometries and
different step-ups. This is only possible in today’s fully
integrated laser cutters where there is ongoing
communication between the PLC and the camera system. It’s a
good illustration of why laser cutters that do not feature a
high level of systems integration are now obsolete
machines. They simply can’t keep up with the demands of
working with variable data and variable images for which
digital printing is so ideally suited.
This same feature
of integrating cameras with machine controllers allows
today’s high quality systems to automatically compensate for
variations in prints, such as those that are created by
shrinking as inks dry. These better laser cutters
automatically account for variations in step-ups from one
part design to the next and can only do so because of that
ability for the machine controller to communicate with the
camera system. Because these better laser cutting systems
feature full communication between the camera system, the
laser software and the machine controller they can
automatically determine the step up of each job. They are
self-calibrating and operator input is not required to
measure or input step-ups. Antiquated technology that does
not have this level of systems integration simply has no
mechanism available to automate the start of jobs, the
calculation of step-ups, or to compensate for variations in
step-ups created by other steps in the production process.
In today’s
systems with a high level of systems integration, there is a
new ability to vary the job stop criteria by part count
rewound, by rewinder diameter, or the rewinder roll length
as shown in Figure 25 (see PDF copy). Here too, this is
only possible because the software that controls inputs,
outputs, and the laser cutting per se work in concert and
are fully communicating with each other.
This same systems
integration feature of top quality systems also facilitates
the fastest setup of repeat jobs. This is because ALL the
machine parameters needed for a specific job---web speed,
dancer arm pressure, camera system settings, etc.—are saved
in one file. This means that at the very start of the job
you can achieve required cut-to-print accuracy without
having to fuss with reloading parameters for different
system components separately.
You also can
always identify the better laser cutting systems that have
full systems integration by their smart stop systems, which
are lacking in lower quality laser cutters that are devoid
of systems integration. These smart stop systems monitor
all possible fault conditions such as web breaks and
off-positioning of the dancer arm, or full rewinder rolls.
When there is a fault condition anywhere in the system it
pauses and the error message is displayed on the operator
screen. Such smart error messaging facilitates maximum
throughput and is only possible in fully integrated systems
where there is seamless communications between operating
software for registration, lasers, laminators, slitters and
rewinders.
Thus, the upshot
of systems integration in the better quality laser cutting
machines is a faster throughput. Though throughput varies
from one plant to another, and one job to another, a
reasonable expectation is that throughput with today’s
better quality laser cutting machines will be significantly
faster than what is possible with non-integrated technology.
Better yet,
estimating production time is now automated by the software
in today’s better quality laser cutting machines. These
systems’ software creates a database that stores laser
settings for various types of cuts (e.g. kisscuts, creases,
etc.) for the particular substrate being cut. Using this
data, the same software capability that optimizes a job for
web speed will calculate this optimum web speed and the
production rate that is possible. This job simulation is
done by the software, before the job is run, and gives users
of today’s better quality laser cutters an ability to make
very accurate cost projections of new job runs.
Selecting System Components
You can expect a
cost difference of up to 20 % between laser cutting systems
made from high-end components and those that are made with
components of lesser quality. As a manufacturer of both
high-end and more affordable laser cutting systems,
Spartanics estimates that nearly four times as many
users–but certainly not all-- will be adequately served by
lower cost systems. It is important to know that your
source for laser cutting technology is not married to
particular component suppliers. Best-match components for
particular applications (laser source, laser scan heads,
etc.) can be sourced worldwide. Lower cost systems can
produce high quality outputs IF the underlying software
engineering and systems integration are expert.
Figure 1 & 26
(Laser Cutting Technology Comparison Chart) outlines some of
the key differences between lower cost and high-end systems,
and the obsolete technology that they both replace.
Knowing your real
quality requirements is the first step in zeroing in on
whether your operation is better served by low cost or
higher quality laser cutting systems. However, there is a
baseline of quality that should ALWAYS be achieved such as
avoiding burn-through marks and ensuring that there is a
crisp narrow cut precisely following the artwork geometry.
A laser cutting machine must have a high quality laser
source with a small spot size to achieve these results. In
label applications, this also allows for much better control
of the heat transmitted to the release paper on the back of
labels. Inferior laser sources with larger spot sizes often
make it difficult to remove the cut labels because melted
adhesives cause the labels and release paper to stick
together. If a laser cutting system presents burn-throughs
it usually reflects both a poorer quality of software
engineering to operate the laser power and an inferior laser
source with a large spot size. The soft marking
capabilities of today’s better quality laser cutters should
be considered as a non-negotiable feature, whether a system
is high-priced or low-priced. There are systems at all price
levels that can and cannot achieve this level of quality and
thorough investigation is required.
The wattage of
the laser should be carefully considered. Many of the
commercially available lasers have the best laser beam
quality with full power. For lasers of that type, if you
end up using only 10% or less of the laser power from your
laser source you can expect significantly diminished laser
beam quality. For example, a converter making kisscuts with
easy-to-cut materials that has a 300 watt laser in their
cutting system may be using only a small portion of
available laser power and would be better suited by a lower
watt laser. A converter making many throughcuts, including
more difficult to cut release paper, which also wants to
achieve high cutting speeds would need that 300 watt laser.
The smaller the
maximum working area the smaller will be the spot size of
the laser. Smaller spot size means better cuts because the
energy is concentrated and you need less laser power to
achieve the same depth of cut. Less heat is transferred to
the material being cut is always the desired scenario. One
of the differences you will find in lower-priced systems is
that they sometimes use lower cost air cooling for lower
power lasers, as opposed to the more costly water cooled
lasers.
The edge quality
that a particular laser cutting system delivers will vary
with the spot size of the laser. In systems with smaller
working fields (e.g. 200 x 200 mm field size) this is not as
much an issue and one can expect both the better high-end
and lower-priced systems to have a 210 micron spot size. If
the working field is larger, however (e.g. 300 x 300 mm
field size) one needs to be able to make due with a 280
micron spot size when considering the lower-priced
system. As an example, generic label converters might be
well-served by a system with such larger spot sizes but
those involved in RFID applications might need the greater
precision in cutting edge quality.
Smaller spot
sizes not only affect edge quality of the cuts but also will
have bearing on cutting speed. It is very important to
verify that a system can maintain the desired edge quality
and cut-to-print accuracy at the maximum cutting speed of
the system. Some of the more poorly designed laser cutting
systems cannot maintain cut-to-print accuracy over time.
The lower cost laser cutting systems may use sensors for
registration, or in more demanding applications use the
sophisticated camera technology to deliver the very tight
tolerances in cut-to-print registration that are typical of
high-end systems. If these camera systems are fully
integrated with the laser scan heads they are able to apply
the offset values to keep cuts to a precise registration.
Here too, it is not only the quality of the camera but the
underlying software engineering that has great bearing on
the tolerances that are achieved at varying speeds.
 Features
that bear on user friendliness and ease of operation are
found in both the low-priced and high-end better quality
laser cutting machines, reflecting the high level of systems
integration in better quality laser cutters at all price
points. Smart stop systems, job simulation software,
automatic image splitting and optimization for web speed,
variable job stop criteria, and one step job setups of all
operating parameters make these systems straightforward to
operate, even for lightly skilled workers. Because the
software is handling most operations behind the scenes---
registration, web control, laser powering, laminating,
slitting—and because there is full communication between
different system modules, the operator’s work is relatively
simple because the software does the difficult jobs
automatically. Obsolete technology does not have these
various features for ease-of-operation. Some out-of-date
designs do not even give operators the capability to change
job settings while the laser cutting machine is operating,
nor directly on the machine. These type of laser cutters,
that force operators to stop cutting operations entirely and
reload a job from scratch saddle users with unnecessary
drags on production that today’s better quality laser
systems bypass altogether by giving operators numerous ways
to amend job parameters without shutting down the production
line.
(Note:
Spartanics has taken user-friendliness to the next level
with the introduction of the only step-by-step instructional
video wizards for laser cutting as semi-interactive Help
Menu options on all Spartanics Finecut Laser Cutting Systems
as shown in Figure 27. These interactive video wizards do
not rely on language and are designed to help overcome
language barriers that exist in many workplaces around the
world and to quickly bring workers at all skill levels
up-to-speed in operating sophisticated laser cutting
technology. The instructional video wizards cover a range
of topics such as camera set up, performing test shots, and
job setup. When a topic is selected, a short step-by-step
interactive video plays showing the sequence of operational
steps required to perform that function. The videos play on
one screen while the operator can directly interact with the
laser system on another screen while the instructional video
wizard is in progress. Lessons are taught by visual example
rather than spoken or read-then-do techniques.)
Suggested Method for Sourcing Laser Cutting Technology
To begin sourcing
the best laser cutting technology for your operation, you
must first determine your application requirements in terms
of: complexity of geometries to be cut; production rates
required; sheet vs. web; type of materials (PET, ABS,
polycarbonate, etc.). One is best served by contacting
several manufacturers that build laser cutting systems to
request that samples be run on your materials using a few of
your part configurations. The manufacturers should then be
able to recommend the model of their laser cutting systems
that will be correct for cutting your parts from your
materials. Of course, it is very important to ensure that
these manufacturers are equally adept at creating
lower-priced laser cutting systems AND more sophisticated
technology such that they can deliver best-match solutions.
If a laser cutting system integrator is married to
particular components – whether they are lasers, scan heads,
etc.—consider it a red flag that they are not set up to
match laser technology to real application requirements.
After receiving
your cut samples from the prospective manufacturers of laser
cutting systems, and after receiving their recommendations
on the proper model of laser cutter and their budgetary
pricing, request a personal visit to manufacturers of
interest to see actual cutting of your parts and materials.
If you spend one day at the individual manufacturers you
should be able to get a good feel for the degree of
difficulty cutting your parts. A visit also provides an
excellent opportunity to see their plant, to understand
their people that you could be dealing with in the future,
and to examine the ease of use of importing drawings of
parts into the laser cutter and converting the drawings into
a useable cutting path.
As with any
equipment purchase, it’s also advisable to determine the
extent of service support that is available from each
manufacturer, as this can make the difference between a
relatively short period and a much longer period of downtime
in the future. Better quality laser cutters, both
low-priced and high-end, include complete remote diagnostic
capabilities.
The best case
scenario of comparative shopping would also include use of
laser cutting system manufacturers’ contract manufacturing
services. These would provide not only proof of concept but
would allow expert software integrators to fine tune
operations to your exact application requirements.
Markus Klemm is, R&D Software Engineer, of Spartanics
of(www.spartanics.com) which engineers and manufactures a
range of automated equipment for laser cutting, die cutting,
screen printing, card punching, counting, and inspection
used by global label manufacturers, converters, printers,
card manufacturers, among others finishing flat stock
material. Spartanics is headquartered in suburban Chicago,
USA and its worldwide service organization also maintains
offices and spare parts in Europe. Questions and comments
can be forwarded to info@spartanics.com.
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