How to get the maximum circles cutting quality in plasma cutting?

Circle cutting demands precise motion control and circle cut quality will vary as the circle diameter approaches the thickness of the plate. In general, a circle that is equal in diameter to the thickness of the plate being cut is the minimum circle diameter possible. Cut quality will decrease markedly when the circle diameter is less than 1.5 times the thickness of the plate being cut.

For maximum circle cut quality:

1. Slow down cut speed. Smaller circles may require a cut speed that is 60-50% of the speed specified in system cut charts. A slower cut speed will eliminate trailing arc and allow the arc to cut at closer to 0° of bevel.

2. Maintain constant cut height through the circle. This may require locking out the height controller. As the cut speed slows, arc voltage increases and the height controller tends to drive the torch down, changing cut bevel. Avoid torch height movement by locking out the height controller during the circle cut.

3. Start the cut in the center of the circle and use a 90° lead-in to the circle. When the positioner is in top running condition, a 90° lead-in will produce less distortion at the circle initiation. A cutting table with backlash may produce a better cut when a radial lead-in is used.

4. End the cut by overburning the circle cut line rather than by using a lead-out. Time the cut to end just as the arc completes the circle. A lead out or too much of an overburn will cause the arc to cut more of the outside of the circle and cause a distortion at the point where the circle cut is completed. Many CNC systems use and advanced off feature to ramp down cutting current end of cut. Use of the advanced off feature will improve circle cutting.