Calculator Inputs
Example Data Table
| Material | Thickness (mm) | Current (A) | Gas | Quality | Speed (mm/min) | Pierce (s) | Kerf (mm) |
|---|---|---|---|---|---|---|---|
| Mild Steel | 6 | 60 | Air | Standard | 1523 | 0.68 | 1.58 |
| Stainless Steel | 8 | 80 | Nitrogen | Standard | 1169 | 0.77 | 1.74 |
| Aluminum | 4 | 45 | Air | Fine | 1850 | 0.61 | 1.45 |
| Mild Steel | 12 | 100 | Oxygen | Standard | 1141 | 0.98 | 1.94 |
Formula Used
The calculator starts from a baseline cutting-speed chart at a reference current, then applies multipliers for current, gas, quality, process, nozzle, consumables, torch height, and air cleanliness.
| Output | Model | Meaning |
|---|---|---|
| Travel speed | Speed = Base(Material,Thickness) × (A/60)^0.55 × Q × G × P × N × C × H × Air |
Starting point for consistent edge angle and minimal dross. |
| Pierce delay | Pierce = 0.20 + 0.08×Thickness×(60/A)^0.40 |
Time to fully pierce before moving to avoid blowback. |
| Kerf width | Kerf ≈ 1.10 + 0.006×A + 0.020×Thickness |
Planning allowance for fit-up, offsets, and nesting. |
| Heat proxy | J/mm ≈ (110×A) / (Speed/60) |
Higher values suggest more heat per length and distortion risk. |
These relationships are generalized for estimating. Manufacturer cut charts remain the best reference for a specific system.
How to Use This Calculator
- Select the material and enter the thickness.
- Enter your torch current and choose the gas.
- Pick a quality target based on finish needs.
- Set process and consumable condition to match your setup.
- Click Calculate; read travel speed, pierce delay, and kerf.
- Run a short test cut, then adjust speed in small steps.
- Download the summary as CSV or PDF for records.
Professional Notes for Construction Work
Dross direction as a speed clue
Heavy dross and rounded top edges often indicate slow travel. Small, hard dross beads can indicate excessive speed or inadequate current for the thickness.
Pierce protection
Use a longer pierce delay on thick plate, or pierce on a lead-in. This reduces blowback that damages consumables and improves repeatability on site.
Air quality matters
Portable compressors can carry moisture and oil. Filtration and drying help maintain arc stability, reduce kerf variation, and extend consumable life during long shifts.
Distortion control
High heat input per length can warp thin parts. Increase speed where possible, add tabs, and sequence cuts to balance heat, especially on fabricated frames and brackets.
Plasma Cutting Speed Guidance for Construction
1) Why cutting speed controls quality
Travel speed sets the balance between melting and ejection. Too slow increases top-edge rounding and heavy dross. Too fast creates lag lines, bevel, and incomplete penetration. A repeatable speed window improves fit-up and reduces grinding time on structural parts.
2) Thickness and current relationship
For most air systems, speed drops quickly as thickness rises. A practical rule is that doubling thickness can reduce speed by about one third to one half, depending on current. Higher current stiffens the arc, supports deeper kerf, and widens the stable speed band.
3) Material differences you can measure
Mild steel often cuts faster than stainless at the same thickness because oxidation assists energy transfer. Aluminum can cut quickly on thin plate, but heat spreads rapidly and may require steadier motion. Expect kerf variation by material, especially on mixed batches.
4) Gas choice and edge condition
Air is convenient on sites and works well for general fabrication. Oxygen on mild steel can improve speed and edge color but needs clean supply and correct consumables. Nitrogen helps stainless edges resist heavy oxidation. Mixed gases may trade speed for finish.
5) Nozzle, standoff, and kerf control
Orifice size influences arc constriction and kerf. A smaller nozzle may reduce kerf and improve detail but narrows the acceptable speed range. Standoff typically sits near 1–2 mm; excessive height increases bevel and dross, while too low risks tip damage.
6) Pierce delay and consumable life
Piercing is the harshest moment for the tip and electrode. Thick plate needs longer delay so the molten column clears before motion. If pierce delay is short, blowback pits the nozzle and speeds become inconsistent. Use lead-ins to move the pierce away from the part edge.
7) Using heat input as a planning metric
Heat per millimeter rises when speed drops or current rises. Higher heat increases distortion risk on thin brackets, gussets, and sheet. When tolerances matter, cut smaller features first, spread cuts across the sheet, and use tabs to keep parts stable during release.
8) Shop-ready workflow with records
Start with a calculated speed, run a 150–300 mm test, then adjust in 3–7% steps until dross and bevel are acceptable. Record speed, current, gas, and consumable condition. Export CSV or PDF so crews can repeat settings across shifts and job sites with fewer setup errors every single week.
FAQs
1) Why does dross increase even when speed looks correct?
Dross can come from wet air, worn consumables, incorrect standoff, or low current for the thickness. Check air filtration, replace the tip and electrode, confirm torch height, then fine-tune speed in small steps.
2) Should I slow down for small holes and tight corners?
Yes. Reduce speed slightly for tight radii so the arc stays centered and the kerf does not widen. For CNC, add corner slowdown and use a short lead-in to stabilize the cut.
3) What is a practical way to verify kerf for offsets?
Cut a straight slot, measure the removed strip, and subtract from the programmed width. Repeat after changing consumables or current. Use the measured kerf to set tool compensation and nesting gaps.
4) How do I choose between air and oxygen?
Air is the most convenient and works well for general steelwork. Oxygen can improve mild steel speed and edge appearance, but it needs correct consumables and clean supply. For stainless, consider nitrogen to reduce oxidation.
5) What causes a strong bevel angle on one side?
Bevel commonly indicates incorrect speed, torch height, or swirl ring issues. Ensure the torch is square to the plate, confirm standoff, and test a slightly faster speed. Replace consumables if the arc is not symmetrical.
6) Can I use the same settings for painted or rusty plate?
Surface coatings can change pierce behavior and arc stability. Clean the pierce point, increase pierce delay slightly, and verify speed on a short test cut. Expect more spatter and faster consumable wear on dirty material.
7) How often should I recalibrate travel speed on site?
Recheck whenever thickness, gas, compressor quality, or consumables change. For long shifts, verify at the start of the day and after tip replacement. A quick 200 mm test cut prevents wasted parts and rework.