Laser cutting is a thermal cutting process in which a tightly focused laser beam locally melts or vaporises the material while an assist gas blows the melt out of the cut. The beam follows a computer-controlled path, so the part comes out of the sheet exactly as drawn.
Because the heat is put into a very small zone, distortion stays limited and the cut is narrow and clean. In construction it has become the standard way of having steel gusset plates, base plates, decorative railings, facade panels and fixing details made to size.
Two main types
- Fibre laser — the beam is generated in and delivered through a glass fibre. Cuts metals: steel, stainless steel, aluminium, copper and brass. By far the most common type for building work.
- CO2 laser — a gas laser with a longer wavelength. Suited to non-metals such as timber, MDF, acrylic and textile, and to thicker steel plate.
Note that galvanised and coated sheet gives off fumes when cut and leaves a damaged zinc layer along the edge. Cut bare material and galvanise or coat afterwards.
The assist gas sets the cut quality
- Oxygen on mild steel: the oxygen burns with the process and adds energy, so greater thicknesses are reachable. The cut edge does gain an oxide skin that must be removed before painting.
- Nitrogen on stainless steel and aluminium: cuts oxide-free and bright, so the part can be welded or coated straight away. More expensive in gas consumption.
What to expect from the process
- Kerf: in the order of a few tenths of a millimetre. Expect holes to come out slightly wider than the path.
- Dimensional accuracy: on sheet parts typically within tenths of a millimetre over small dimensions; over long sheets the deviation grows because of heat input.
- Sheet thickness: depends on machine power. Mild steel is cut into the centimetre range, while stainless steel and aluminium go considerably thinner at the same power.
- Small holes: a hole smaller than the sheet thickness is often not cleanly cuttable. Rule of thumb: hole diameter ≥ sheet thickness.
Points to watch when subcontracting
- Supply a vector drawing (DXF or DWG) with closed contours, no duplicate lines, and everything at 1:1 scale. A PDF or a scanned sketch has to be redrawn first, and that costs money.
- State material, thickness and grade (for example S235 or stainless 304), and whether you want bright or oxidised cut edges.
- Nest your parts sensibly. Cutting cost is driven by cut length plus pierces; many separate small pieces are expensive each. Combine orders and ask for nesting in one sheet.
- Deburr and degrease before welding or coating; the cut edge is hard and can retain a small burr.
- Allow for set-up. For a one-off you are mainly paying programming and set-up time; from a handful of pieces the unit price drops quickly.
Related terms
- Milling
- Welding on
- Reinforcing steel
- Corten steel
- Aluminium
- Cold-formed steel
- BIM
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.