A new plasma cutter is providing dramatic improvements in
production capabilities for one kiln manufacturer.
The plasma cutter cuts until the entire sheet has been
transformed into parts.
In the fall of 2006, Paragon Industries acquired a
MultiCam LP plasma cutter to improve our manufacturing process in the sheet
metal shop. We researched many of the other methods for cutting sheet metal,
including water jet, high-speed punch press and laser cutters, and determined
that the plasma cutter was the best fit for our needs and budget.
Until the addition of the plasma cutter, our technology
included two shears, three turret punch presses, two hydraulic press brakes and
the assorted other trappings of standard sheet metal production. The old
process required the shears to cut blanks to the required sizes for each
particular part. These blanks were then punched one at a time on the turret
punch presses and de-burred by hand or belt sander, then bent in the press
Paragon's growing business presented a number of challenges
to the old process, which required 20 sets of metal (12-24 gauge electro
galvanized, 16-24 gauge 300 series stainless, and low nickel 0.018 in.
stainless) to be produced, with each set including numerous pieces that needed
to be sheared, bent, de-burred and trimmed. Many small pieces, such as hinge
assemblies, mounting plates, etc., took a great deal of time to make.
All of the pieces for 20 kilns needed to be ready before
we started assembling the units. If one piece was bent wrong, misplaced or
damaged, the process was required all over again, and that one piece could
require a 15-min punch or die change. Delays were prevalent. Moreover, the
machines themselves were over 30 years old and required regular maintenance.
The process also provided many opportunities for small
errors. For example, the shearing had to be very close for the blanks. If the
punch presses were off slightly, the holes might not have lined up correctly or
the piece could have lost its square. The tables for the turret press had to be
manually reset regularly, and the high number of process steps increased the
potential for inaccuracies.
In addition, the use of punch presses limited the types
of shapes we could produce. Odd sizes or shapes required expensive dies and punches.
Non-linear shapes were very difficult, and this limited certain product.
The punch presses, which had been previously upgraded to
improve accuracy and speed, have a computer that controls the turret and the
X-Y motion of the table, and prompts the user to check that the correct punches
are in the proper station. Still, the machine-dominant process could only
produce a certain number of parts every day, and it was not enough to keep up
with demand. Moreover, other internal suppliers were able to increase their
output through regular incremental improvements in people, processes or
equipment, and the metal shop remained our primary constraint.
Assisted by a specially-designed cart (at right), one
operator can slide the 4 x 10 ft sheet metal onto the machine bed without
Crafting a Solution
In the spring of 2006, we decided to craft a definitive
solution that would take us beyond merely incremental improvements. David
Vives, plant manager, Bob Gieselman, engineering director, and I began
investigating potential solutions, and we engaged the Texas Manufacturers
Assistance Center (TMAC) to help. Our goals were to eliminate as many processes
as possible and improve accuracy.
The research gave us the opportunity to analyze the
benefits and detractions of each option, and, in the end, we decided that a
plasma cutter would suit our needs most effectively. MultiCam is located within
40 miles of Paragon's facilities, so we scheduled visits to test the cutting on
our materials and to review how the software interfaced with our AutoCad
engineering software. The visits and test cuttings were successful, and we
decided to move ahead.
Installation of the new machine required detailed
pre-planning. We made space inside the factory for not only the plasma cutter,
but also for its power supply, a fan to remove fumes, duct work, light screens
around the unit, and a grounding rod. We used a third-party equipment rigging
service to deliver and install the plasma cutter to the concrete pad.
The loading of the sheet metal was also an issue. We did
not want two people to be required to load the metal, so we manufactured a
large rolling cart prior to the plasma cutter's installation. The cart allows
one operator to slide the 4 x 10 ft sheet metal onto the machine bed without
Our prior planning allowed the plasma cutter to be
operational within two days of delivery. It was another three weeks before we
were manufacturing parts for our products, and our learning curve went vertical
during this time. Through trial and error, we discovered what mix of travel
speeds and power gave the best finish on each type and gauge of metal, how to
utilize the software, and all the other nuances of the equipment.
Enjoying the Benefits
The new plasma cutter provides a number of improvements
over the previous process. One operator now loads the metal sheet on the bed,
picks the program to use, sets the travel speed and power, and presses start.
The plasma cutter then cuts until the entire sheet has been transformed into
parts. As the cutter moves along, the operator removes the cut parts and uses a
brush sander to remove the slag from the part. When the entire sheet has been
cut, the operator removes what looks like a spider web of leftover material and
places another sheet on the bed. The cutting process is 50% faster with the new
The plasma cutter is accurate to around 0.003 in., which
is more than sufficient for our application. We traded two steps (shearing and
punching) for one step, and the accuracy of the machine's servo motors is very
Since the price of metal has only increased in the last
few years, reduced waste is another very attractive benefit. The software
designs the best layout for the required parts on a sheet of metal, and small
parts can be nested into previously discarded pieces. The plasma cutter can
also easily cut nonlinear shapes, which improves the aesthetics of the product
and offers more design capabilities than were previously available.
In addition, the plasma cutter provides reduced setup
times and labor requirements. For example, if a door is needed quickly, the
operator can place a piece of metal on the table and cut the piece in about 5
minutes. Also, the plasma cutter allowed us to move two people from the metal
shop to other areas of the factory. We view this as a win-win scenario because
Paragon retains the employees' knowledge and they learn new skills to assist in
the company's growth. We do not need to trim, de-burr and shear as we did with
the previous process, so labor costs have also decreased.
The plasma cutter was at full capacity within two months
and now operates through all lunches and breaks. We will be adding a second
plasma cutter this fall, since the current unit can handle only about 50% of
our sheet metal needs. The addition of the plasma cutter smashed a constraint
and showed us the potential of this technology in our production process. We
believe the addition of another unit will have the same dramatic improvement on
our production capability.
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