At Aquascan we use a laser to cut the tender names, logos and much more.
Focusing on downtime reduction in laser cutting
Automated laser optics management can keep the laser cutting when it normally might not be
April 30, 2013
If a laser cutting machine is not cutting, it has
no chance of making money for the shop. Downtime related to maintenance
is understandable. Downtime related to the slow process of attending to
laser optics is frustrating. Automation, however, can help keep that
laser cutting machine running, even when it's cutting different material
thicknesses.
Figure 1
As metal fabricators take on more low-volume, high-mix work,
they have to minimize downtime of laser cutting machines to maintain a
high level of productivity. Automated management of laser optics can
save hours of downtime over a year’s worth of laser processing activity.
The metal fabrication industry has gone through several volatile
years—expanding during the dot-com and real estate booms and contracting
during the recessions that followed. This roller coaster ride (much
more tumultuous than my favorite childhood roller coaster, Mr. Pip’s
Wild Ride at Palisades Park, N.J.) feels like it is nearing its final
stages. The major gyrations are done, and things
are smoothing out just a little.
Somewhere between the start of this ride and today, business models
in the metal fabricating industry evolved into something different (see
Figure 1).
Business owners are struggling with uncertainty as they are unable to
forecast order streams confidently and faced with escalating operating
costs, especially as they relate to new government regulations and
health care.
Companies are still interested in increasing throughput, but unlike in
the past, they are not immediately hiring people to solve their
productivity problem.
These shop owners are instead relying on automation—both for material
handling and basic machine functions. These advanced features make
machine operation more efficient and productive.
Automated material handling increases green light time for laser
cutting machines. Material loading is done much more quickly than can be
done manually. Additionally, automated material handling allows for
unattended operation—loading blanks, unloading cut parts and the
accompanying skeletons, and repeating the operation until all sheets
have been processed.
Laser cutting equipment with material handling automation is
identified easily in fabricating operations. The machines have
single-level loading systems nearby or, in some instances, very large
material storage towers that have shelves for different sheet metal
sizes, material types, or even finished parts.
Productivity improvement because of the automation also is easy to
identify. Shop management typically can expect to see a 40 percent
increase in throughput after installing an advanced material loading and
unloading system.
Automation Beyond Material Handling
But what about downtime associated with setting up the laser cutting
machine? Other areas for downtime management are often less obvious than
material handling, but they also can have a dramatic effect on
throughput.
The downtime problem is exacerbated with today’s smaller batch sizes.
Orders aren’t as large as they once were, and companies are working
with thousands of part numbers, not hundreds. These volumes can lead to
drags on productivity and spikes in costs of operation if shops aren’t
prepared properly.
For example, laser cutting equipment without automated setup
functions use compromised settings when cutting varied materials. This
commitment to one type of cutting lens may enable the laser to cut with
limited operator intervention, which may be desired especially when
running with automated material handling, but the laser cutting machine
is not being run optimally.
For the record, laser cutting machines without these automated
functions can run efficiently. However, it is difficult to maintain
long-term, efficient production if the job shop has regular part
changeovers. Research done on actual machine changeovers reflects that
manual changes typically take around 26 minutes to complete, when done
properly. If the shop considers all of the steps involved
in a standard laser setup—set up lens, install nozzle, focus the lens,
set the gap, set the focal point, do a test cut, tweak the lens if
necessary, and start production—it can understand how setting up for a
job can get out of hand very quickly. Simply put, waiting for an
operator delays production while the machine sits idle.
Automated changeover functions are much more efficient and take less
than 1 minute, including a torch change and pallet transfer. Many
operators skip or shorten the changeover process and run the laser
cutter in a compromised cutting condition with general settings that can
reduce machine performance by 25 percent to 30 percent. The machine is
running and has the appearance of being a
productive, money-making investment, but it is actually costing the shop
added expense because the setup is not fine-tuned to the cutting
application.
Compromised laser cutting reduces cutting speeds dramatically, but
because shop owners are rarely involved directly in laser machine
operation, they are not aware of the lost revenue. This oversight can
offset the performance gains available with new technology and,
ultimately, devastate the return on investment that a company is looking
for with the purchase of a new machine.
Figure 4
Some metal fabricating shops stick with a 7.5-in. lens to cut
all material thicknesses, not just plate. By not changing over to a
5-in. lens for thinner materials, for example, the operator is taking
more time than necessary to complete the cutting job and simultaneously
consuming more assist gases.
Automated Setup Functions
These new functions automatically set up the machine, check for wear on
critical components, and make adjustments to optimize the cutting
parameters. Core automated setup functions include torch changing,
nozzle changing, intelligent focal distance measuring/adjusting, and
profiling.
Torch and Lens Changer. Some manufacturers have
designed torches that can adjust focal lengths to accommodate different
material types and thicknesses. All manufacturers, however, make a
variety of lens configurations that are optimized for specific
applications. Unless workpiece type and thickness don’t vary much, the
shop needs to change out torches for optimized cutting of
the material (see
Figure 4). If a fabricator elects to
use a standard lens for multiple cutting jobs, it risks slowing the
process down because feed rates are not maximized and the operator
likely has to spot-check the material to ensure clean cuts are being
made.
Nozzle Changer. Nozzle diameter is critical in
cleaning the molten debris from the cut path. If a nozzle diameter is
too small, it will need to slow down to clean the cut path. If the
nozzle is too large, it will need more gas to flush the path, which can
significantly increase laser gas costs.
Automated Focal Distance Adjustment. Measuring and
adjusting focal distance traditionally requires considerable setup time
as well as a skilled and experienced operator. Intelligent functions
enable an operator with limited experience to set the focal distance
automatically using programmed commands. This helps to ensure dross-free
cutting. Additionally, these systems
compensate for focal distance changes that occur as lenses become
contaminated.
Automated Profile Adjustment. The automated profiler recalibrates to ensure the optimal distance between the nozzle and workpiece is achieved.
Optimized Cutting = Improved Cash Position
Not only does automated setup technology typically result in a
significant increase in throughput by reducing operator intervention, it
also results in reduced assist gas consumption because the proper
nozzle is selected for the application. To illustrate the impact of this
type of automated laser optics management, all a shop has to do is take
a look at an analysis of its laser-related
production over a full year.
The wider the variation in materials and thicknesses, the greater the
economic advantage gains with automated setup. For these calculations, a
consistent nest configuration was applied to the annual production
analysis. Nozzles and other setup functions were performed automatically
to match optimal cutting parameters. With automated setup functions,
the laser cutter cut the annual production
volume in 3,287 hours as compared to 4,170 hours with a single lens. The
shop also has a considerable laser gas savings because of the automated
functions.
An experienced laser applications engineer can provide a detailed
review of an entire production model based on a metal fabricator’s
nested sheets using the shop’s actual materials. The economic impact
analysis specific for the shop should be comprehensive enough to show
the real cost benefit.
