The X axis is taking shape, I used an H shaped layout for the carriage, with drywall screws and skate bearings. There is no spring tensioner, the placement of the bearings press slightly against the rails, and there is enough give in the bed to fit it in without any play. This was accomplished by using washers as spacers between the end of the cross piece. With the two screws, after getting close to the right number of washers, the exact alignment is done by tightening or loosening the screws a small amount, this results in the end piece twisting, with a bit of finesse eventually it ends up being exactly right. The vertical alignment is simple by comparison, just use a single screw on the other end and tighten it, it should be no problem to force all four bearing wheels onto the track with the wood friction keeping the joint tight.
I also trimmed some plastic from the bed near the end to make clearance for the motor to be mounted to a threaded rod. There is a small tendency of the carriage to ride up out of it's slot, but when the rod is attached that will act to keep it from riding up. The profile of the rail should not matter much. The same setup should work fine with metal rod, pipe, angle iron, etc. Any profile where you have a straight inner surface, and a straight top surface.
Monday, September 8, 2008
I found a fan that looks a lot like a computer fan, but it's 110V and bigger. It was seized, so I removed the center from the bearings by persuading it with a hammer and a set. That released the blades and rotor. I cleaned away all the corrosion with emery paper, and sprayed it well with WD40. The bearings were still fine, so after pressing it back together the blades spun freely. I soldered a power cord to it and it runs OK; it's not too loud. I also rubber banded a 45 Gallon garbage bag to it to get an idea of the airflow, it filled the bag in five or six seconds, so it's probably about 60 cubic feet per minute.
Tuesday, September 2, 2008
I melted some more HDPE, this time I did it in the garage on a gasoline burner. I wrapped the plastic in aluminum foil to keep it from sticking to the pan. Then I squashed it flat between two pans and left some heavy chain on it while it cooled. I ended up with a 1/4" x 8" cookie of plastic sheet, it's mostly flat, and the foil is well stuck to it. I'm not sure what I'll use it for. Mostly I've just been cleaning and storing stuff from the pile. My second computer won't boot any more, it sat too long, or it needs a battery, and the power supply was always extra noisy, it locks part way through boot up usually. I wonder if this was related to the ethernet problem I had last month, even though that computer is off most the time. All the time now I guess, maybe I'll get a couple new power supplies, and try one in that. I need another computer for the garage anyways, so I can do the RepRap stuff there.