Blog by Steve Haddrell.

Recently I was asked by a customer to go and investigate an issue they were having with cutting thick mild steel.

We did the obvious checks on a fibre laser; clean optics, good nozzle, and alignments.

Having done these and having changed the protective window, as this had spots on it, we did some test cuts and the results weren’t bad at all, but the edge wasn’t perfect.

We tweaked the oxygen down, and the result was deemed good enough for production by the customer.

This issue in this case was twofold.

The marked protective window. Even though it would cut thinner material ‘ok’, it wasn’t suitable for this more difficult cutting.

The quality of the material. The sheet didn’t look good at all, light rust, and a lot of surface scale. The fact that we had to reduce the gas pressure pointed to poor chemical balance in the sheet.

We looked at a copy of the mill certificate for the sheet, and the same document for another thick sheet of mild steel that the customer had. This second sheet had processed completely differently, with an excellent edge finish when cut with laser.

The difference was the sheet that had cutting issues had a lot more silicates in it than the other sheet, 200% more in fact.

The sheet with the excellent edge had come from a German mill and the sheet with issues didn’t have an origin marked on the mill certificate.

The lesson learned here is you don’t need to buy Laser Plate to get a good piece of mild steel for laser cutting. If you buy steel from a good mill that manufactures high standards, you will have fewer cutting issues and better part finishes.

You should avoid materials of unknown origin with high silicate levels. You will save time and money!