The fire was in my universal x-660.
It looks like I got pretty lucky. None of the lenses were damaged,the x,y,z all work and the laser still fires. The x belt is melted and so is one of the wheels/bearings on the carriage. The new belt should arrive on Monday and I already have a new set of bearings. The plexi/poly in the lid is also melted but since that doesn't affect how the machine runs I wont worry about that until I get everything else up and running.
The fire extinguisher I used was a dry chemical. It put the fire out with a 1 second blast so the mess from that isn't too bad. I also have a halon fire extinguisher. It is literally leaning up against the laser that had the fire. But in the excitement (panic) I couldn't find it so I grabbed the one on the wall 6 feet away. Then I tried spraying it and forgot to pull the pin, it took a second or two to figure out why it wasn't spraying and then another few seconds to fiddle with the pin to get it out. If nothing else I learned it is very easy to forget very common sense things when you panic.
As far as the part erupting into flame when I opened the lid. I think the flame was burning on the inside hollow area of the jig for a couple minutes before I noticed the flame on the surface of the of the wood part. And the air flowing over from the exhaust was blowing out what few flames were coming out of the cuts the laser was making. When I opened the the airflow stopped and allowed the flame to burn on the top of the wood and since it was already hot from the fire underneath it burst into flames. I don't think having a stronger exhaust would have prevented this, if anything it would have made it worse because it would have allowed the fire inside the jig to continue growing much longer before I noticed it. And then once the fire got to the surface of the wood the extra air that the exhaust provides would have caused the fire to grow much quicker.
The jig I was using allowed me to cut 18x32 inch pieces of plywood by holding the plywood up of the table, the plywood was supported by a plastic grid to prevent the tar on the cuts that happens if I cut directly on the aluminum table. I think it was the plastic that caused the fire. Most of the plastic under the plywood was burned away but only a small maybe 8 inch circle of the plywood burned which makes me think the fire was burning underneath for a while before the wood actually caught on fire.