Process troubleshooting -9, Process trouble-shooting – Hypertherm PAC500 Water Injection Plasma Cutting System User Manual
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PAC500
Instruction Manual
5-9
4
MAINTENANCE
Process Trouble-Shooting
The two major quality problems encountered in plasma cutting are excessive cut angle and dross. This section
describes these conditions and recommends corrective action.
The cut angle should generally be square to within 2°. A small amount of rounding of the top edge is normal. The
cut angle is said to be positive if the cut slants away from the high quality side, and negative if the cut slants in
toward the high quality side (figure 5). Both of these conditions can be corrected by properly adjusting torch-to-work
distance, cutting speed and arc current.
Dross is resolidified metal that adheres to the bottom edge of a cut. The tendency to form dross depends on
metallurgical composition, plate surface condition, cutting speed, arc current and torch-to-work distance. Under
normal conditions dross should be virtually nonexistent, or if it is present, easily removed.
Positive Cut Angle
1. Wrong direction of travel.
High quality side is on the right with respect to the forward motion of the torch, except where CCW Swirl
Ring, Part No. 020042 is used.
2. Excessive torch-to-work distance.
3. Excessive cutting speed.
4. Arc current set too low.
5. Damaged nozzle.
Negative Cut Angle
1. Torch-to-work distance is too low.
2. Cutting speed is too slow.
3. Excessive arc current.
Excessive Dross
1. Cutting speed is too slow.
Increase cutting speed up to the point where the arc becomes unstable and excessive lag lines are evident.
Reduce the speed just enough to obtain a stable condition. If dross still persists, follow the suggestion
outlined in Step 3.
2. Arc current set too low.
Increase arc current up to the maximum current rating of the nozzle and increase speed as outlined above.
3. Nozzle size too small.
If steps 1 and 2 do not eliminate the dross, go to the next nozzle size and set the current 100 amperes
below the maximum current rating of the nozzle; adjust the cutting speed accordingly.