Student Material 001: Plasma Arc Technology Quick Reference
Material ID: U5M1-MAT-001
Purpose: Quick reference for plasma arc cutting fundamentals, parameters, and system components
Updated: 2026-03-19
Plasma Arc Fundamentals
What is Plasma?
Plasma is the fourth state of matter β a superheated ionized gas that conducts electricity. In plasma cutting, compressed gas (air, nitrogen, oxygen, or argon/hydrogen mix) is forced through a constricted nozzle and an electrical arc ionizes the gas, creating a plasma jet at 25,000β45,000Β°F.
How Plasma Cutting Works
1. Compressed gas flows through torch β enters nozzle
2. Pilot arc ignites (HF start or contact start) between electrode and nozzle
3. Pilot arc ionizes gas β creates conductive plasma channel
4. Main arc transfers to workpiece (transferred arc mode)
5. Plasma jet melts metal and high-velocity gas blows molten metal away
6. Result: narrow kerf (cut width) through the metal
System Components Reference
| Component |
Function |
Key Specs |
| Power Supply |
Converts AC input to DC cutting power |
Output: 20-80A (makerspace), 200-300V OCV |
| Torch (Hand or Machine) |
Directs plasma arc to workpiece |
Rated amperage, duty cycle |
| Electrode |
Provides the cathode (-) for the arc |
Hafnium tip (for air/Oβ), tungsten (for inert gas) |
| Nozzle |
Constricts gas flow and shapes the arc |
Orifice size matches amperage (0.030"β0.065") |
| Swirl Ring |
Spins gas for arc stability |
Material and condition affect cut quality |
| Shield Cup |
Protects consumables, directs shielding gas |
Size matches nozzle/amperage |
| Work Clamp |
Provides return path for cutting current |
Must make solid contact with workpiece |
| Air Compressor/Gas Supply |
Provides cutting gas at required pressure |
60-90 PSI, dry and clean (moisture separator required) |
| CNC Table (if applicable) |
Moves torch over workpiece via G-code |
THC (Torch Height Control) maintains arc distance |
Consumable Life Reference
| Consumable |
Signs of Wear |
Replace When |
Approximate Life |
| Electrode |
Pit depth >1/16" |
Pit reaches 0.080" depth |
1-3 hours cutting |
| Nozzle |
Orifice oblong/oversized |
Visible wear, arc wanders |
1-3 hours cutting |
| Swirl Ring |
Discolored, cracked |
Visible damage |
5-10 hours cutting |
| Shield Cup |
Spatter buildup, cracks |
Heavy spatter or cracks |
3-8 hours cutting |
Critical rule: Always replace electrode and nozzle as a SET β mismatched wear degrades cut quality.
Cut Parameter Quick Reference
Mild Steel (Most Common)
| Thickness |
Amperage |
Speed (IPM) |
Kerf Width |
Gas |
Pierce Delay |
| 16 gauge (0.060") |
25-30A |
100-150 |
0.06" |
Air |
0.0s |
| 14 gauge (0.075") |
30-35A |
80-120 |
0.06" |
Air |
0.0s |
| 12 gauge (0.105") |
35-40A |
60-100 |
0.07" |
Air |
0.2s |
| 10 gauge (0.135") |
40-45A |
50-80 |
0.07" |
Air |
0.3s |
| 3/16" (0.1875") |
45-55A |
35-60 |
0.08" |
Air |
0.5s |
| ΒΌ" (0.250") |
55-65A |
25-45 |
0.09" |
Air |
0.8s |
| β
" (0.375") |
65-80A |
15-30 |
0.10" |
Air |
1.2s |
| Β½" (0.500") |
80A |
8-15 |
0.12" |
Air |
2.0s |
Stainless Steel
| Thickness |
Amperage |
Speed (IPM) |
Gas |
| 16 gauge |
30-35A |
70-110 |
Air or Nβ |
| 12 gauge |
40-50A |
40-70 |
Nβ preferred |
| ΒΌ" |
60-80A |
15-30 |
Nβ/Hβ or Nβ |
Aluminum
| Thickness |
Amperage |
Speed (IPM) |
Gas |
| 16 gauge |
30-35A |
90-130 |
Air |
| 12 gauge |
40-50A |
50-80 |
Air or Nβ |
| ΒΌ" |
60-80A |
20-35 |
Nβ or Air |
Note: Aluminum requires slightly higher amperage than steel for the same thickness due to higher thermal conductivity.
Cut Quality Indicators
| Indicator |
Good Cut |
Cut Too Fast |
Cut Too Slow |
| Drag lines |
Vertical or slightly trailing |
Heavy trailing angle (>15Β°) |
Vertical but excessive dross |
| Top edge |
Clean, slightly rounded |
Rounded with spatter |
Clean but excessive HAZ |
| Bottom edge |
Minimal dross, easy to remove |
Heavy dross, hard to remove |
Light/no dross |
| Kerf width |
Narrow, consistent |
Narrow, may be incomplete |
Wide, excessive material removal |
| Sound |
Steady, consistent buzz |
Interrupted, sputtering |
Smooth but too drawn out |
Torch Height & Standoff Distance
| Amperage Range |
Recommended Standoff |
Pierce Height |
| 20-40A |
0.060"β0.080" |
0.150" (2Γ standoff) |
| 40-60A |
0.060"β0.080" |
0.150" |
| 60-80A |
0.070"β0.090" |
0.180" |
Torch Height Control (THC): On CNC plasma tables, THC automatically adjusts the torch height during cutting by monitoring arc voltage. Target voltage varies by amperage and material β consult the machine's THC voltage chart.
Safety Quick Reference
BEFORE CUTTING:
[ ] 35-foot radius cleared of combustibles
[ ] Fire extinguisher within 15 feet
[ ] Ventilation/fume extraction running
[ ] Work clamp making solid contact
[ ] All personnel have proper PPE or behind screens
[ ] Welding shade: #8-9 (<40A) or #9-12 (40A+)
DURING CUTTING:
[ ] Never touch torch tip or workpiece while machine is armed
[ ] Monitor for fire continuously
[ ] Keep hands 12"+ from arc
AFTER CUTTING:
[ ] Let parts cool 5+ minutes
[ ] Mark hot metal "HOT"
[ ] Fire watch for 30 minutes
[ ] Power off at main switch
Last Updated: 2026-03-19