CNC Plasma Cut-Quality Troubleshooting

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Which Variable Is Likely Wrong

Handheld dross forks (top vs bottom vs hard fin) are documented for torch work in handheld plasma troubleshooting. The physics of dross is the same. The knobs are not: you cannot roll a wrist on a gantry, so height and delay do the job the operator used to do by feel.

Dross on a CNC Table

After a new nozzle and dry air, use speed and cut height:

• Soft bottom dross — increase IPM toward the top of the calculator band, or confirm you are not over-amping thin sheet.
• Hard bottom dross — decrease IPM, then check cut height. A torch sitting at 0.15" during the cut (THC never dropped from pierce height) will hard-dross at any “correct” speed.
• Top spatter — usually slow, or the shield is too close. Raise cut height a couple hundredths only after speed is in band.

Poor Pierce and Incomplete Breakthrough

If the contour starts before the hole is through, you get a skip, a blowout later in the part, or a torch crash when the THC dives into a blind puddle.

• Delay too short → add 0.1–0.2 s, especially on stainless and on anything ≥ 3/8".
• Pierce height too high → arc does not transfer cleanly; drop 0.02" or check work clamp.
• Pierce height too low / piercing at cut height → blowback. Raise pierce. Do not pierce 1/2" at 0.06".
• Amps too low for thickness → the calculator flags “above quality range.” Edge-start or step up process amps. A 40A box will not happily pierce 3/8" in the middle of a nest.

Angled Edges

A few degrees of bevel is normal on air plasma. A consistent lean that makes the part oversized on one face is a setup fault:

• Square the torch to the plate (gantry tram, not “it looks vertical”).
• Cut height too high widens the top of the kerf and steepens bevel.
• Worn oval orifice bevels one side. Change tip and electrode together.
• THC lag on corners looks like bevel plus a gouge. Slow corners; do not slow the whole contour 40%.

If you only need a torch-in-hand diagnosis, the handheld settings guide covers standoff and angle for a human. This page stays on programmed Z.

Blown Consumables

Nozzles do not “just go.” On a table, the usual killers are low pierces, wet air, and moving before the pierce is through (the shield takes the splash). A nest that destroys a tip every three pierces is not an IPM problem.

1. Drain the dryer. Watch regulator PSI for a 20-second contour. Sag → compressor, not CAM. CFM / tank guide.
2. Confirm pierce height is above cut height. If both are 0.06", that is the bug.
3. Edge-start when the nest allows. Center pierces on thick plate are consumable eaters.
4. Then re-enter the calculator and run a coupon. Still dying? Compare CNC vs handheld expectations on CNC vs handheld settings — a drag-tip habit on a machine torch will crater the stack.

FAQ