Mild Steel Cutting with CO2 Lasers

Cutting mild steel with a laser is a balance of how much material is heated with the laser beam and how much assist gas flows through the cut. Rather than having a proper kerf, you could end up with either a narrow or wide kerf, which can affect part quality and appearance.

Narrow Kerf

Heating up an area that’s too small or not having enough assist gas flow through the cut will result in the kerf (width of the cut) being too narrow. Some common characteristics are a very smooth cut edge on the top with a lack of oxidation on the bottom of the cut and/or heavy dross. These characteristics suggest that the:

• Focus is too low
• Feed rate is too fast
• Gas pressure is too low
• Nozzle size is too small
• Standoff is too low

Wide Kerf

Conversely, heating up a large area or having too much assist gas flow will result in the kerf being too wide. Common characteristics include a rougher cut edge, more self-burning in the corners of the part, more angularity on the cut edge, and occasional dross. These characteristics can suggest that the:

• Focus is too high
• Feed rate is too slow
• Gas pressure is too high
• Nozzle size is too big
• Standoff is too high

How to Optimize Cut Quality

You can optimize the cut quality for any material using the following steps (to isolate the issue please be sure to make only one change at a time):

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 centered properly.
5. Adjust the focus up and down until the cut starts to get bad, and then set it to the middle.
6. Move the gas pressure up and down until the cut gets bad, and then set it to the middle.
7. Modify the feed rate upward in increments of 5%. When the cut begins to get bad, set the feed rate 10% slower.