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Pierce delay is the time a CNC plasma cutter waits after starting the arc before it begins moving along the cut path. The pause lets the arc pierce the plate and reach a stable cutting height. Set it too short and the torch may travel before it has cut through; set it too long and it wastes time, enlarges the starting hole, and wears the consumables faster.
What pierce delay controls
At the start of a cut, the torch fires while stationary. The arc melts through the material, and molten metal blows out below the plate. Pierce delay tells the CNC motion controller how long to wait before moving the torch. It is not the same as torch height, pierce height, or cut height, though all three affect whether a pierce succeeds.
Use the delay recommended in your plasma cutter’s cut chart as a starting point. The right value depends on material, thickness, amperage, pierce height, air pressure, consumable condition, and the machine’s motion. A value that works on 1/8-inch mild steel may fail on 1/2-inch plate.
Set a starting value
Check the cutter manual or cut chart for the material thickness and amperage you plan to use. Many machines include pierce delay values or specify a pierce sequence. If the chart gives a range, begin near the middle. If it gives a fixed value, use that before making adjustments.
As a rough diagnostic starting point—not a substitute for the manufacturer’s chart—thin sheet may pierce in roughly 0.2 to 0.5 seconds, while thicker plate may need 1 to 3 seconds or more. Some systems handle timing automatically, so do not add a manual delay without checking how the CNC and cutter share control of the sequence.
Set the correct pierce height as well. Piercing too close to the plate exposes the nozzle to molten splash; piercing too high can make the arc struggle to reach the work. Follow the torch maker’s specified pierce height, then test. If you are choosing a machine for CNC work, compare CNC-compatible plasma cutters by their cut charts, machine interface, and pierce-height requirements rather than maximum amperage alone.
Test and adjust the delay
Use scrap from the same material and thickness as the job. Secure it flat, confirm the torch is square, and run a short test with the same amperage, air supply, and settings you intend to use. Keep clear of the torch and wear suitable eye, hand, and body protection; plasma cutting throws hot metal and produces intense light and fumes.
Inspect the first pierce from above and below. A clean through-pierce should leave an open hole and a cut that starts without a heavy uncut tab. If the torch begins moving while metal remains, increase delay in small steps—about 0.1 to 0.2 seconds at a time on thin material, or 0.2 to 0.5 seconds on thicker plate. Retest after each change. Avoid compensating for bad air pressure, worn consumables, or incorrect height by adding a long delay.
| What you see | Likely cause | What to check |
|---|---|---|
| Cut starts with an uncut tab | Delay too short, or pierce did not complete | Increase delay slightly; check pierce height, air, and consumables |
| Large crater or excessive splash at the start | Delay too long, pierce height too low, or slow piercing | Reduce delay after confirming the specified height and settings |
| Arc fails or cuts start inconsistently | Air, ground, torch connection, or consumable issue | Check the manual’s air requirements, work clamp, and torch parts |
| Starting hole is much wider than the kerf | Stationary arc is dwelling too long | Use the shortest delay that reliably pierces through |
Account for thickness and consumables
Thicker material generally needs more time to pierce, but delay does not increase in a simple linear way with thickness. A high-amperage torch, correct pierce height, and good air can pierce faster than a poorly set-up system. Use the cut chart for each thickness and amperage rather than scaling the time by guesswork.
Consumable condition matters. A worn electrode or nozzle can produce a weak or wandering arc, making a previously reliable delay seem too short. Inspect and replace parts as the torch maker specifies. A compatible set of plasma torch consumables is useful to keep on hand, but match the parts to your torch; similar-looking nozzles are not necessarily interchangeable.
Also verify the air supply. Moisture, oil, low pressure, or restricted flow can prevent a clean pierce. Check the cutter’s pressure and flow requirements while air is flowing, not just the compressor’s tank gauge. If the pierce is inconsistent, fix these basics before making a large timing change.
Use lead-ins when the part allows
A lead-in moves the pierce point away from the finished edge, then brings the cut into the part. This keeps the pierce crater and splash out of the visible contour and reduces the chance of damaging a narrow feature. It does not eliminate the need for a successful pierce. Set the lead-in length and shape in your CAM software, allowing enough room for the torch to complete the entry without crossing the finished edge.
For production work, save separate tested settings by material, thickness, and amperage. Recheck them when you change the torch, consumables, air system, or machine speed. The practical target is not the longest delay or the cleanest-looking isolated hole: it is the shortest repeatable delay that fully pierces without leaving a start defect or damaging the torch.