During the process of plasma cutting, many times the operator can make cutting mistakes that not only result in the consumables wearing out faster, but also result in poor quality cuts and downtime. Some common cutting mistakes are:
The distance between the tip of the torch and the workpiece, also known as the standoff, is crucial to both the consumable’s life as well as the cut quality. The slightest of variations in the torch height can affect the angle of the cut surface. The torch height is important, especially during piercing.
A very common error is when the piercing is very low. This results in the molten metal spattering in front of the shield and nozzle. This damages the parts and results in reduced cut quality. If the torch pierces while touching the metal or drags along the metal surface when cutting, arc snuffing can occur. This causes the nozzle, electrode, swirl ring and even the torch to be damaged. Piercing that is done at a height of twice the recommended cut height helps to protect the parts as well as the torch from damage.
Cutting Very Fast or Too Slow
If you cut very fast or too slow with the plasma cutter, you will have problems with the cut quality. If the speed of the cutter is very slow, there will be an accumulation of low- speed dross at the bottom edge of the cut metal. Slow speeds can also cause too much of spatter on the top and the kerf will be widened.
If the speed of the plasma cutter is too fast, there will be a lag in the arc resulting in a narrow kerf, bevelled edge and hard dross along the bottom of the cut workpiece. It is very difficult to remove the high speed dross. The correct cutting speed will result in clean edge cuts that do not require any finishing and minimal dross.
Stretching the Plasma Arc
If the plasma arc has to stretch or it moves away from the straight path to find the metal, arc stretching occurs. This can occur at the beginning and the end of the cutting process. Arc stretching will result in the side wall of the nozzle being cut by the arc when the plasma cutter is in operation.
When doing an edge-start, the arc must be started with the orifice of the nozzle directly at the centre of the edge of the metal being cut. Arc stretching may also occur at the end of the cutting process if the torch runs off the workpiece with the plasma arc on or if the lead out of the metal cut previously follows the kerf. This effect can be minimized by adjusting the timing of the arc being turned off and programming the lead out.
Thus, we have looked at how commonly occurring cutting mistakes can affect the cut quality and also damage the plasma torch and its parts, thereby reducing productivity and efficiency of the cutting process.