CNC Plasma cuts many of the profile cut parts available from MechWerks. An explanation of the process will better explain the final product. CNC is “computer numeric control” and simply indicates that a computer controls the motion of the cutting machine. Plasma cutting uses an electric arc of around 9000 degrees with compressed air to cut through metal sheet and plate.
Parts drawn in CAD (computer aided drawing) can be quickly converted to a cutting file. The cutting file is used by the CNC computer to guide the plasma-cutting torch. Nearly any computer picture (or scanned hand drawing), can be converted to a line drawing and then converted to a cutting file to produce metal parts of complex shapes.
Most parts are provided “as-cut” indicating the edge of the metal has plasma torch marks and will require additional finish work. Most of the cuts made by a plasma cutter are actually pretty smooth and requires a small amount of sanding to clean up. Plasma leaves a taper when it cuts and leaves a couple degree angle to the cut side which becomes more noticeable on thicker materials like 3/8” and above. MechWerks supplies parts with this unfinished edge as a way to reduce cost of parts to the customer. Disc sanders, belt sanders and die grinders (even a Dremel type tool works for limited numbers of parts) work well to finish part edges.
This is a picture of a motor mount cut from ˝” HR steel. The dime offers some sense of scale. Note the “saw-toothed” edge from the plasma cutter. It is very similar to a saw cut and requires about the same amount of work to clean up. As the metal is heated to a high temperature in the immediate cut area and cools rather quickly, the metal tends to be rather hard and does not work well with metal files. Powered sanding methods mentioned above are recommended. This heat-affected zone doesn’t appear to go deep into the metal and is usually removed once clean metal is exposed.