Hi Sjefke!
Sounds great that you're going to build a CO2 laser from scatch, and I'm looking forward to see your projekt evolving.

As I had the discussion a couple of days ago, I'm woundering why you go with a CO2 laser if your main application is cutting MDF.

Looking at the cheap China CO2 lasers, they often state that this is not good for cutting wood.
On the other hand the diode lasers 10W to 20W are advertised to cut up to 10mm of plywood (more with an air assist).

That's why I asked a friend (who shoud know). And he said that he can imagine that this is because of the hugely larger wave length of the CO2.
This allows the CO2 to cut through transparent materials like plexi and even glass, but creates problems with wood.

BTW 10W diode lasers should be fine (just to save some money)

Regards Andreas