Introduction to Plasma Pattern Cutting
Do you have questions about plasma pattern cutting? Get some tips and learn about equipment selection, pattern design and setup.
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.
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
When piercing the metal at the beginning of a cut, start in an area outside of the design and hold the torch at an angle, as shown here. Push the trigger and roll the gun until it’s perpendicular to the metal. Then move to the side of the template and begin cutting.
For straight cuts, one tool that may come in handy is a standoff roller guide. Fix the guide to the standoff and roll the cutter along a straight edge. The roller also allows you to maintain the recommended standoff distance. This maximizes cutting performance and keeps your tip in good shape for longer.
Remember to keep the gun perpendicular while cutting. If the gun is angled, it will create a beveled edge.
If you need to see the cutting arc, angle your head to the side for a better view.
Use your non-cutting hand as a brace to maintain the proper position. Rehearse it beforehand to ensure that you can make the cut without changing position.
Once the template cutting is complete, the template is removed. Areas too small for the template to accommodate are then cut by hand, following the outline.
The dross that remains after the cut can be knocked off easily using a piece of scrap metal.
Consider using a grinder to finish the piece, cleaning up rough edges and providing another aesthetic element.