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 brake.

Numerous Challenges

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 assistance.

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 assistance.

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 plasma cutter.

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 good.

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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