Laser O2 cutting guide for mild steel

Optimizing the cut quality for any material should be done using the following steps.

1. Use the closest known settings to the material you are trying to cut.
2. Use a test part that has some interior and exterior features.
3. Verify that the lens and/or window is clean, and in good condition.
4. Verify that the nozzle is in good condition and is centered properly.
5. Adjust the Focus up and down until the cut starts to get bad, then set it to the middle.
6. Adjust the Gas Pressure up and down until the cut gets bad, then set it to the middle.
7. Adjust the feedrate up in increments of 5%, when the cut begins to get bad, set the feedrate 10% slower.

Cutting mild steel with a laser is balance of how much material is heated up with the laser beam and how much assist gas flows through the cut. Heating up too small of an area or not having enough assist gas flow through the cut will result in the kerf, (width of the cut) being too narrow. Heating up too large of an area or having too much assist gas flow through the cut will result in the kerf being too wide.

Below are examples of 12, 6, and 3.2mm (1/2”, 1/4”, and 10ga) mild steel cut with oxygen on a 2kw fiber laser and examples of the same part cut with 1 variable changed to show how it affected the cut quality. The examples of the adjustments made will be similar for any CO₂ or fiber laser cutting mild steel with O₂.

Factory cut chart settings

Kerf too narrow

Common characteristics would be a very smooth cut edge on the top, with a lack of oxidation on the bottom of the cut, and/or heavy dross.

Possible causes:

The focus is too low	The feedrate is too fast
The gas pressure is too low	The nozzle size is too small
The standoff is too low

Kerf too wide

Common characteristics would be a rougher cut edge, more self burning in the corners of the part, more angularity on the cut edge, and occasionally dross.

Possible causes:

The focus is too high	The feedrate is too slow
The gas pressure is too high	The nozzle size is too big
The standoff, is too high	The nozzle type is incorrect