20
OPERATION
Before starting any welding or cutting activity ensure that you have suitable eye protection and
protective clothing. Also take the necessary steps to protect any persons within the welding
area.
Modes of cutting
Piercing
is the process in which a quick hole is made in the work piece. Piercing is often just a starting hole
that will be used to make a circular cut within the work piece. You can use standard cutting tips for
piercing although ensure the plasma machines output amperage matches the cutting tips amperage
rating. No accessories are required when piercing. The thickness of the material to be pierced will need
to fall in the proper amperage range for the machine and tip you will be using. There are two different
techniques for piercing depending on the thickness of the work piece. If the work piece is less than 2mm
sheet metal, the torch should be held at a 15-30° angle with the cutting tip touching the work piece.
Begin by establishing the pilot arc, as soon as the pilot arc penetrates the work piece, use a smooth,
rolling motion to move the torch to a 90° (perpendicular) angle. At this point, the pierce has been created
in the work piece allowing you to begin the cutting process. If the material being cut is thicker than 2mm
the torch should be held at a 90° (perpendicular) angle approximately 12mm or more above the work
piece.
Begin by establishing the pilot arc and slowly move the torch towards the work piece until the cutting arc
transfers. Once the transfer has occurred, hold the torch still until the arc exits the bottom of the work
piece. Once the pierce has been made, the torch can be lowered to normal cutting height and the cutting
process can begin.
Bevelling
allows you to angle the edge of a flat plate or pipe to allow for deeper weld penetration. This
process is normally used for materials that are 9mm or thicker. You can utilize standard cutting tips for
bevelling again, you need to ensure you utilize the correct plasma machine amperage to match the
cutting tips used. Ensure that the thickness of the material to be bevelled falls in the amperage range of
the plasma machine and cutting tip that you will be using. If bevelling by hand, a roller and/or angle guide
can be helpful in maintaining the consistent bevel face and the desired angle which is usually determined
by the weld joint design. The industry standard angle ranges are from 15-45°. The cutting tip would
normally be between 3-6mm from the work piece.
Gouging
creates a smooth, clean concaved groove within the material being gouged which is often weld
ready. This process is primarily used for weld removal or back gouging. Gouging has specific consumables
and settings depending on the gouge you need to produce which include the gouging tip and often the
shield cup and possibly a gas distributor would be specific to gouging. To begin the gouging process, hold
the tip of the torch approximately 12mm from the work piece angling the torch approximately 20-40° to
the surface, engage the pilot arc and once established, slowly move the tip closer to the work piece until
the main arc has transferred. Once the main arc is established, retract the tip until the distance from the
work piece to the tip is approximately 15mm. Make sure that you keep the tip of the torch angled
approximately 20-40° during this entire gouging process. To create a narrow u-groove in the work piece,
the operator should maintain a constant, smooth travel speed. With this technique the gouge created
will be approximately 6mm wide by 6mm deep but this may depend on the gouging tip profile.
To create a wider groove, you can oscillate the plasma torch side to side in a half-moon sequence while
maintaining a constant, smooth travel speed. The gouge created will be wider but not as deep.
Due to the nature of the gouging process, lead covers, gouging deflectors and torch covers are some
accessories that will help to protect the equipment used in the gouging process. Gouging can be done on
all conductive materials.
