There are many factors that can affect laser cutting quality; the machine, the operator and material can all have a bearing on quality of the cut edge. However, the most critical parameters to laser cut quality are material thickness and material type.
Striations are regular lines on the cut-edge where the molten zone meets the cool zone, which lowers the quality of the surfaces produced. The thicker the material the more pronounced the striations are, for example, at the thickness scale for laser cutting stainless steel the following striations are left by CO2 lasers on 10mm stainless steel.
These striations affect the tolerance achievable. For example, in steel less than 1.0mm thick, we would offer +/- 0.12mm, in 10mm steel the repeatable tolerance would increase to +/-0.25mm and mild steel at 20mm thick we would be maintaining +/-0.75mm tolerances.
One way to improve the effects and reduce the appearance of striations , more powerful laser machines can be used. Using a higher powered laser enables the beam to cut through thicker sheets of metal easier and thus produces a better edge quality compared to less powerful counterparts.
Material type can cover a large remit of different factors, the most obvious is the type of metal itself. Different metals possess different properties,so each react differently when being laser cut.
Laser profiling is more reliant on a consistent surface quality that other cutting methods. The surface finish quality of the sheet can drastically affect the quality of the cut. We recommend that steel should be clean, pickled, rust and oil-free.
Low-grade steels represent a considerable problem for laser cutting. The impurities within these low grades can be highly reactive to the thermal cutting process, especially if using oxygen assisted laser cutting.
Hot rolled steel can also prove to be problematic for laser cutting due to its surface scale. The surface can melt in with the metal, creating a low quality cut finish. If the surface is not smooth and free of imperfections, the laser focus can be altered, affecting the cleanness and quality of the cut.
In an effort to produce steel sheet that is perfectly suited to laser cutting, many steel mills now offer “laser grade” or “laser ready” steel. These materials have low impurities, guaranteed flatness and aim to provide the best quality laser cut profiles.
Ensuring you get the best laser edge quality
When it comes to providing you with laser cut profiles, we always ensure to use sheet and plate that is suitable for laser cutting.
However, if you are providing your own free-issue material, please ensure that it meets the requirements set out above, namely it needs to be:
- Rust free
- Oil free
- Free from surface impurities – such as mill scale etc.