If anyone has a good ventilation fan that would be helpful. I saw one at AxMan for $27 but thought that maybe it would be too large. Speaking of consumables, I did some calculations...
Since the 40 watt laser tube is rated at 1500 to 1800 hours of use (after which point it will only be at 90% of original power) and replacement is only $168 to $200, it probably doesn't have a significant consumables cost associated with it. Even if you add in replacing mirrors and focusing lens. The 3D printer filament, welder wire, and the CNC router bit wear probably cost more in consumables than this thing does.
Even assuming that people were very productive and were firing the laser half the time they were using it (workpiece setup seems to take longer than the actual burn time) then we would have to have people on it 40 hours a week for a year and a half to two years to reach that point. Vastly more than any other equipment at the Hack Factory gets used.
However, I don't think that we will have more than a few hours of use a week at most. If people start to use it significantly then maybe consumables might become an issue in a several years. Otherwise we might be looking at 10 or more years before we need a new laser tube. And by then maybe they will have diode lasers for $20 at that power. Prices on these things keep dropping.
Therefore, I don't think there should be a charge for using the laser cutter because we don't do that for any other equipment, it would set a horrible precedent, and seems, to me, contrary to the philosophy of the whole TC Maker concept.
I have pretty much decided to just retain ownership of the laser cutter/engraver and just let people use it after some training. A key benefit of that, is that when I do upgrades, to give it a larger work area for example, and if I accidentally break it, then I only broke my own thing, and no one can play victim.