I came home and found that my Y pulley had snapped. I was running that belt quite tight. Luckily it seems to have broken after finishing the current print. So I’m running an 8 tooth pulley there now since it’s all I had sitting around.
Since I had to get the Y platform off to re-tention the belt for the 8 tooth pulley anyway, I took the opportunity to switch to an iteration 2 style platform, with the bushing holders glued straight to the bottom of the upper platform with no leveling provision.
It’s working and it’s a good thing. Much simpler, no need to level, much less moving mass, signficantly less hardware, the print surface is more tightly bound to the drive belt, so it probably will help with the overshoot and oscillation I’ve seen on the Y axis sometimes. And now the belt attaches to the bottom, so there’s a ton of room for putting on a belt tightener clamp. And there’s a mile of room under the printer now, enough for power supplies and electronics. I may try designing an electronics holder that fits under there.
I still haven’t figured out exactly what to do with the heated print bed, specifically where to put the thermistor. I think I might drill a hole up through the center of the bed and use a dremel or just a sharp knife to carve a small slot for it. Right now I spaced the heating board up with a couple of fender washers on each corner but that’s messy.
Also I think I’m going to recommend going slightly rectangular with the top plate and print surface. 225mm square is really pretty tight to try to get clips on the edges and still get 200mm of print surface. There’s no reason it can’t be quite a lot longer, I think I’m going to make my next one at least 250mm long.
I did offset it to the right a bit to allow for the asymmetrical extruder. I think I might have very close to 200mm of both X and Y travel now.
I also want to do something a little nicer than the Z axis adjustment I have now, which is a thing printed from Thingiverse. It’s ok but a little klunky. Also the endstop holder for the Z axis can wobble a bit, I’m going to think about a more solid mount for that, since on that axis a fraction of a millimeter matters.