Introduction to Plasma Pattern Cutting

Artistic plasma cutting

Cutting simple designs and patterns with a plasma cutter is a great way to liven up many DIY or artistic welding projects. But if you are new to plasma pattern cutting, you may have questions about how to get started. 

Follow these tips to get more information about equipment selection, pattern design, safety, machine setup and more that will help you achieve success in plasma pattern cutting.  

Getting started

Perhaps the easiest way to perform artistic plasma cutting, or to cut identical pieces, is to use a CNC-driven plasma cutting table and a computerized art file. However, these tables often carry a hefty price tag and may not be feasible for your needs — or space. You can still complete quality plasma pattern cutting using a hand-held plasma cutter and a plasma cutting table. 

Once you’ve developed your design,  either by hand or using a graphics program, the first step is to transfer it to your metal workpiece. There are various methods of accomplishing this, including tracing a cardboard cutout or using carbon paper to transfer a sketch and then retracing it with a black marker so it can easily be seen while cutting. Carbon paper is available in many art supply stores.

Plasma cutter selection

If you don’t already have a plasma cutter, there are some considerations to keep in mind when choosing one. Probably most important is the machine’s cut rating, which is the thickness of material that may be cleanly cut when traveling at a rate of about 10 inches per minute (ipm). The cut rating is in direct proportion to the output amperage of the machine.

You should choose a plasma cutter that cuts the thickness of metal you will work with most often. There is an exception, however. If you will begin most of your cuts by piercing the metal, as opposed to starting from an outside edge, a good rule of thumb is to use a machine capable of cutting twice the thickness you are cutting. It’s important to be able to pierce the material quickly; otherwise molten material can splash back into the torch tip and shorten tip life.

The choice of plasma cutter also affects the type of tips that can be used. For plasma cutters rated below 40 amps (about 5/8-inch cut rating), the cutting tip can rest directly on the metal when cutting. For those rated 40 amps or more, the cutting tip cannot rest on the metal, since double-arcing can occur and quickly damage the tip. Because of this, the operator must maintain a standoff distance of about 1/16 to 1/8 inch or use a drag shield that can rest on the surface and maintain proper standoff.

One option is the Miller® Spectrum® 375 X-TREME™ plasma cutter, a 30-amp, inverter-based plasma cutter with a cut rating of 3/8 inch at 18 ipm. It has more than enough power to quickly pierce the 1/8-inch steel used, and it allows placing the tip directly on the metal. Because the unit is about the size of a lunch box and weighs only 19 pounds, it also lends itself to a portable or easily storable setup.

Compare Miller plasma cutters here.

Plasma pattern templates

If you’re designing a piece to be used as a template, you need to account for the radius of the cutting tip or drag shield in your initial design. For instance, to cut the circle (solid line) shown below from a piece of metal, your template would need to be drawn to the size of the outer dotted line. Another option for cutting circles is to use a circle cutting guide, which helps maintain recommended standoff distance to maximize cutting performance and improve tip life.

The thickness of the template material should be approximately 1/4 inch. This is to provide a firm vertical surface for the side of the tip to press against without slipping.

Plasma cutting safety 

Familiarize yourself with the machine’s owner’s manual, paying particular care to the safety section. Among the requirements for plasma cutting are wearing gloves, long sleeves and an appropriate pair of shaded safety glasses.

Plasma pattern cutting setup

Place the template and workpiece on metal blocks and securely clamp them to the worktable. The ground clamp is secured to the table to provide a good electrical connection to the workpiece. Although a plasma cutter can cut through paint, the connection from the ground clamp to the workpiece should be free of paint or other contaminants.

Use a marker to outline the design. Be aware that if your pattern has tight angles, you may need to make some of the cuts by hand. If your pattern requires a great deal of cutting, warping may occur. In those instances, consider stitch cutting — similar to stitch welding.

Starting the cut