Cut to the chase

Considering plasma arc cutting for your applications

PRACTICAL WELDING TODAY® MARCH/APRIL 2002

April 15, 2002

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This article outlines some of the benefits, limitations, and applications of plasma arc cutting. It also provides questions to ask when considering the process for your business.

Many applications that traditionally didn't use plasma cutting now can consider it a viable tool. End-user markets for plasma arc cutting have expanded over the last several years.

Newer technologies—such as advanced, digitally controlled inverters—have resulted in developments that can make these systems more affordable and can provide robustness that most typically existed in more cumbersome machines.

In the beginning, plasma development was limited to drooper or chopper technology. Though this technology is reliable, the architecture tends to be large. New inverter technology can provide durability in a smaller footprint. This provides portability, which can be a benefit in construction applications in which cutting often takes place in multiple locations on one site.

Advancements such as microprocessors, solid-state hardware, and self-resetting fuses add to newer systems' reliability. Other developments include advances in system and torch design, elimination of breakable consumables, and a more cut-resistant torch cable jacket.

In addition, the flexibility of operating equipment with 115-volt input power has brought plasma cutting to the home owner and hobbyist. No longer does a potential plasma user need to be concerned about the complexities of operating the equipment. Today torch design and functionality can improve convenience and ease of use for the unseasoned operator. Nozzle shield technology allows the operator to place the torch on the material when cutting, allowing for greater control and precision.

Many cutting applications can take place in remote areas, where power is not readily available. Welding professionals now can incorporate a plasma system onto their trucks, along with an engine-driven generator and an air compressor, to perform remote operations. Common examples include repairs to construction equipment, such as dump trucks and bucket loaders. Other on-site applications include railcar repairs and bridge construction.

Determining whether your application is an appropriate candidate for plasma arc cutting can be as simple as answering a few questions about the work you do:

1. What are the primary costs in your production or repair processes? If the primary costs are cutting or finishing steps, plasma can offer savings.

2. What are the critical issues or quality parameters? If conformance to specifications and high quality are critical, plasma systems can offer a controlled arc that minimizes metal warping.

3. What new capabilities could plasma cutting bring to your operation? Plasma can gouge existing welds and cut thin-gauge material with minimal warping.

4. What is your skill level in welding and maintenance?

The plasma process requires slightly greater welder skill and training than oxyfuel welding. Also, maintenance skill and training must be greater than for gas tungsten arc welding (GTAW) because the equipment is more complex.

Applications

Aside from the well-known applications for plasma cutting, it can be used in many other, less familiar operations.

Metal Artwork, Ornamental Iron-working. In the past plasma systems have not been considered able to provide the precision cutting required for intricate artwork. Now new advances in cutting capabilities and torch design offer a new perspective.

For cutting intricate shapes or designs, plasma systems offer a focused arc and compact torch design, providing ease when following a line or tracing a template. Furthermore, the controlled arc and high travel speeds reduce heat input to the workpiece, reducing metal warping.

Plasma also can provide high cut quality on a variety of both ferrous and nonferrous metals, such as steel, aluminum, stainless, copper, and brass, which is important for metal artists.

Roofing and Siding. This industry uses thin-gauge, finished steel that must be customized for the structure. A controlled arc offers the ability to cut finished material with minimal effect on the paint. As in ironworking and metal artwork, minimal warping occurs because of plasma's high travel speeds and controlled arc.

For cutting holes needed for air conditioners, vents, and pipes, drag cutting can be used with a focused arc to follow a line or trace a template.

Solid Waste Removal. In this industry, dumpsters, storage containers, and hoppers become worn and require routine maintenance and repair. For most repairs requiring metal cutting, oxyfuel is the method of choice. However, plasma systems can provide gouging capabilities for removing existing welds on metal dumpsters and collection vehicles. This can shorten the time needed to make repairs, such as siding or frame replacement on dumpsters or storage bodies.

Plasma cutting can minimize the need for secondary finishing steps by using a controlled arc and high cutting speeds. In addition, plasma systems require no preheating and minimize heat input to the workpiece during cutting. This can result in a reduction in the cool-down period required before using the workpiece.

It's important to remember that plasma is restricted to metal cutting. The plasma process uses an electrical arc that needs to be transferred to an electrically conductive material.

John Brennan is manual systems product manager and Clayton Gould is assistant product manager with Hypertherm Inc., Etna Road, P.O. Box 5010, Hanover, NH 03755, phone 603-643-3441, fax 603-643-5352, e-mail john.brennan@hypertherm.com, clayton.gould@hypertherm.com, Web site www.hypertherm.com. Hypertherm Inc. is a provider of plasma cutting equipment and services.

Reference

Leonard P. Connor, ed., Welding Handbook, 8th edition, Vol. 1 (Miami: American Welding Society, 1987), p. 12.



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