I can't figure out what our laser is doing. When you start a cut at the surface of some wood quickly it cuts wonderfully with a nice fine line down about 2mm into the wood with 3 to 4 passes. And then it doesn't really cut past that even if you let it go for 20 or 30 passes.
But it won't really cut deeper.
The weird bit is that this seems to be the case when you change the distance between the lens and the wood by up to around 4mm. I have no idea what is going on.