Guide
Laser, plasma or waterjet: which cutting method for your part
Updated
The cutting method is usually the fabricator's decision, but it drives the edge you get and part of the price, so it is worth understanding what they are choosing between.
The four processes
| Process | Strengths | Limitations |
|---|---|---|
| Laser | Excellent edge quality and accuracy on thinner material, fast, clean holes and fine detail, minimal secondary work | Thickness limits depending on the machine, and reflective materials such as copper and brass need the right laser type |
| Plasma | Fast and economical on thicker steel plate, widely available | Coarser edge with more taper and dross, so it suits structural work more than visible or precision parts |
| Waterjet | Cuts almost any material, no heat-affected zone, good for thick sections and heat-sensitive alloys | Slower and generally more expensive per metre, and the edge has a characteristic texture |
| Sawing and shearing | Cheapest way to cut sections and straight lines to length | Straight cuts only, no profiling |
The heat-affected zone, and why it can matter
Laser and plasma cut with heat, which changes the metal locally at the cut edge. For most fabrication that is irrelevant. It becomes relevant on hardened materials, some aluminium alloys, parts that will be heavily formed near the edge, and anything where the specification restricts it. Waterjet cuts cold, which is precisely why it is used on those jobs despite costing more per metre.
How the choice shows up in your price
- Edge quality you asked for. If the cut face is visible or gets welded to a tight fit, the cheaper process may need grinding afterwards, and that labour can exceed the saving.
- Nesting. How efficiently your parts pack onto a sheet decides how much material you pay for. Simple, similar shapes nest well; awkward one-offs do not.
- Number of pierces. Every hole starts with a pierce, which takes time. A plate with two hundred holes is a very different cutting job from one with four.
- Small internal features. Very small holes relative to material thickness may not be cuttable and will be drilled instead, which is a separate operation.
What to tell the fabricator
Rather than specifying the process, tell them the outcome: whether the cut edge is visible, whether it needs to be square rather than tapered, whether it is a mating face, and whether heat input near the edge is restricted. A good fabricator will pick the cheapest process that meets those, and they may well have all of them in the building. Specifying "laser cut" on a thick structural bracket that nobody will ever see just adds cost.
Send a DXF or STEP file if you have one. Cutting from a PDF drawing means someone redraws your part, which costs time and introduces mistakes.