Okay, I admit it, I destroyed the blooming thing

It now has a new tube, tube mounts at the correct height, a proper power supply and it doesn't have a millimeter crust of black gunge on the lens. Probably from cutting plywood. Not me, I found bits in the bottom of the case

I've been doing the laser forums and there's more to this laser malarky than I realised. Back to school again I suppose. I see that Wee Davy Cameron thinks us over 60's should go to university

It's mostly a cooling thang. You pump water through the tube, perfect temperature is -28 C but you actually have to keep above the room dew point because 20kV and condensation can make life interesting. Room temperature is fine and dandy but if you let it rise much above 30 C you lose vast amounts of power. Bubbles in the tube are a big no-no because you get hot spots. I have to fit a radiator (on it's way from China) and a big fan. I also need a flow detector which cuts off the PSU if the water flow stops, but I can make that.

As far as I can make out, the best thing you can do with a 40W is cut perspex. It goes through it like a hot knife through butter even when turned right down, but apparently blowing air down through a nozzle mounted over the lens is a good idea. The perspex vapourises. You want to clear it without condensing it or something like that.

I also plan to attack it with an angle grinder to redesign the fume extraction. The current system has way too much fan for the ducting, plus he hasn't cottoned on to 2 simple facts. Air doesn't like abrupt changes in duct size. Getting the desired flow is as much about where you let the air in as where you take it out.