What does laser cutting mean in fabrication?

In a fabrication shop, laser cutting usually means profile cutting flat parts from sheet or plate on a CNC laser, most often a fibre laser. A drawing comes in, gets nested onto a sheet, and the machine cuts each part's outline, holes and slots.

The process runs like this:

1. The beam is focused to a small spot on the surface of the metal.
2. It pierces through, then follows the cut path at the programmed feed rate.
3. Assist gas, usually oxygen, nitrogen or compressed air, blows the molten metal out through the bottom of the cut.
4. Small tabs called micro-joints can hold finished parts in the sheet until it's unloaded.

Oxygen reacts with mild steel and speeds up cutting on thicker plate, but leaves an oxidised edge. Nitrogen gives a clean, bright edge on stainless steel and aluminium, at a higher gas cost.

How is laser cutting used?

Laser cutting makes flat parts: brackets, plates, gussets, panels, enclosure blanks before folding, signage, and parts for kits and assemblies. It handles one-offs and production runs equally well, which suits job shops with a wide mix of customers.

Typical capability on a fibre laser:

• Materials: mild steel, stainless steel, aluminium and galvanised steel, plus brass and copper
• Thickness: from under 1 mm up to about 20 mm (3/4 in) of mild steel on a 3 kW machine, and 25 mm (1 in) or more at 6 kW and above, with lower limits for stainless and aluminium
• Accuracy: around ±0.1 mm (±0.004 in) on thin sheet, a little looser on thick plate
• Kerf: about 0.1 to 0.5 mm (0.004 to 0.02 in)

Parts usually move on to other work afterwards, such as folding, welding, tapping or powder coating.

Why does laser cutting matter?

For many shops, the laser is the first machine every job passes through, so its speed and accuracy set the pace for everything after it. Accurate laser-cut parts fold, fit and weld with less rework, and tab-and-slot designs can locate parts for welding without jigs.

For pricing, cut time and material are the two biggest numbers in most laser quotes. An error in either repeats on every part in the job.

Laser cutting vs plasma, waterjet and punching

Laser cutting isn't the only way to cut profiles, and the alternatives each have their place:

• Plasma cutting costs less per hour on thick steel and the machines are cheaper, but the kerf is wider (about 1.5 to 3.5 mm), holes are less accurate and edges have a slight bevel.
• Waterjet cutting uses no heat, so there's no heat-affected zone, and it cuts almost anything, including stone, glass, composites and very thick metal. It's much slower than a laser on thin sheet.
• Turret punching is fast for high volumes of parts with lots of standard holes and formed features like louvres, but it needs tooling.

Many job shops run a laser for most work and buy in plasma or waterjet cutting for the jobs that suit it.

Laser cutting and quoting

A laser cutting quote comes down to a few numbers: cut length and pierce count from the drawing, feed rates and pierce times for the material and thickness, the hourly rate, and how much sheet the parts use once nested. Setup, secondary processes and margin go on top.

Tempus Tools quotes laser cutting straight from the customer's file, and also handles plasma and waterjet with their own rates, so one system covers all the profile cutting a shop does.

Further reading: How to set laser cutting prices that are competitive and profitable