Student Material 001: CNC Plasma Operation Quick Reference¶
Material ID: U5M3-MAT-001 Purpose: Quick reference for CNC plasma table setup, operation, and consumable management Updated: 2026-03-19
Complete Setup Checklist¶
AIR SYSTEM:
[ ] Compressor tank drained
[ ] Water separator drained
[ ] Coalescing filter — condition OK
[ ] Desiccant dryer — indicator green (dry)
[ ] Air pressure: _____ PSI (target: 65-75)
CONSUMABLES:
[ ] Electrode pit depth: _____ " (max: 0.040"-0.080")
[ ] Nozzle orifice: round and clean
[ ] Swirl ring: no cracks or discoloration
[ ] Shield cup: clean, no heavy spatter
[ ] All assembled in correct order
TABLE & MATERIAL:
[ ] Water table at correct level
[ ] Slats in serviceable condition
[ ] Material positioned on slats (spans 3+)
[ ] Work clamp on workpiece (bare metal contact)
[ ] Cable routed clear of torch path
[ ] Material is flat (or weighted/clamped flat)
MACHINE:
[ ] Machine origin set (X=0, Y=0)
[ ] THC voltage set for material/amperage
[ ] G-code file loaded and previewed
[ ] Toolpath within material boundaries
[ ] Cut sequence: holes first, profiles last
SAFETY:
[ ] Fire extinguisher within 15 feet
[ ] Welding screens deployed
[ ] All personnel: PPE on or behind screens
[ ] E-stop tested and accessible
[ ] Shop alert: "Plasma cutting starting"
Consumable Assembly Order (Inside to Outside)¶
1. ELECTRODE — Push fully seated into torch body
↓
2. SWIRL RING — Align gas passages, push into place
↓
3. NOZZLE — Orient correctly, hand-tight
↓
4. SHIELD CUP — Thread on retaining cap, snug only
Consumable Wear Reference¶
Electrode Pit Depth Gauge¶
New Acceptable Replace Soon REPLACE NOW
| | | |
0" 0.020" 0.040" 0.060-0.080"
● ◐ ◑ ○
(flat) (shallow pit) (moderate pit) (deep pit)
Nozzle Condition¶
New: ○ (perfectly round orifice)
OK: ○ (round, slight wear ring)
Worn: ⬭ (oblong — cut quality degrading)
REPLACE: ◇ (obviously out-of-round, arc wanders)
THC Voltage Reference (Approximate)¶
| Amperage | Mild Steel | Stainless Steel | Aluminum |
|---|---|---|---|
| 25-30A | 115-125V | 118-128V | 120-130V |
| 40-45A | 108-118V | 112-122V | 115-125V |
| 55-65A | 120-135V | 125-140V | 128-142V |
| 80A | 130-145V | 135-150V | 138-152V |
These are starting values. Fine-tune based on cut quality. Higher voltage = greater standoff.
Troubleshooting Quick Reference¶
| Problem | Likely Cause | Fix |
|---|---|---|
| Arc won't transfer | Work clamp loose; consumables worn; material too thick for amperage | Check clamp contact; replace consumables; increase amperage |
| Arc wanders | Worn nozzle; contaminated air | Replace nozzle (and electrode as set); check air filters |
| Excessive dross (bottom) | Speed too fast; amperage too low | Slow down 10-20%; increase amperage one step |
| Wide kerf, rounded top edge | Speed too slow | Increase speed 15-25% |
| Double arcing (nozzle destroyed) | Standoff too low; piercing too thick; wrong nozzle for amperage | Verify THC settings; reduce material thickness; match nozzle to amperage |
| THC hunting (oscillating) | THC sensitivity too high; voltage set point wrong | Reduce THC sensitivity; adjust target voltage |
| Inconsistent cut quality | Moisture in air; consumables partially worn | Drain air system; replace consumables |
| Parts tipping into water table | No skeleton tabs; parts too small | Add tabs in CAM; increase minimum part size |
Cut Sequence Rules¶
CORRECT ORDER:
1. All interior holes and features (CCW direction for good edge inside)
2. Interior cutouts/windows
3. Exterior profiles (CW direction for good edge outside)
4. Cut from center of nest outward to maintain material rigidity
WRONG ORDER (causes problems):
✗ Exterior profile first → part is free, may shift for hole cuts
✗ Random order → thermal distortion affects later cuts
✗ Edge-to-center → material loses rigidity too early
Operating Limits Reference¶
| Parameter | Minimum | Maximum | Notes |
|---|---|---|---|
| Air pressure | 60 PSI | 80 PSI | Below 60: poor cut. Above 80: consumable damage |
| Water table level | ½" below workpiece bottom | Touching workpiece bottom | Too high: arc interference. Too low: poor fume capture |
| Standoff distance | 0.050" | 0.120" | Per amperage/consumable spec |
| Pierce height | 1.5× standoff | 2.5× standoff | Higher for thick material |
| Pierce delay | Per chart (0-2s) | Per chart + 0.5s max | Too short: incomplete pierce. Too long: excessive hole |
| Maximum continuous cut time | N/A | Per duty cycle rating | 60% @ 65A = 6 min on, 4 min cool |
Emergency Quick Reference¶
ANY EMERGENCY → E-STOP FIRST, THEN:
Electrical Shock: DO NOT TOUCH victim → Main disconnect OFF → Call 911 → CPR if needed
Burns: Cool 20 min running water → Do NOT apply ice → Seek medical attention
Arc Eye Flash: Dark room → Cool compress → Do NOT rub → See doctor (may worsen in 6-12 hrs)
Fire: CO₂ or ABC extinguisher → If spreading: EVACUATE → Call 911
Material Ejection: Wait for all motion to stop → Check for injuries → Secure area
Last Updated: 2026-03-19