Round peg, round hole
Sep. 22nd, 2012 10:44 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
rbandrewsPrinting ducks and housewares is nice, but I really wanted to print machines. Gears. Objects that do stuff. A good place to start is the wheel, so I need to be able to print a hole and a pin that fits in it.
So, I made this model on Tinkercad and printed a bunch of variants. The final verdict seems to be that making the hole 1mm larger than the peg yields a hole/peg that fits snugly but not too snugly to turn, and 2mm is loose enough to be a wheel for a toy car or something like that. Next stop, gear town: I have a bunch of stuff (all public domain, naturally) about the geometry of gears and the designs of machines that cut them. It's not as simple as you'd think to make them mesh correctly.
Also this weekend I messed with the bed:
The way the printer works is, you have a print head that extrudes plastic and moves in X and Y, and a flat metal plate that it extrudes it on to that moves in Z. So the head lays down a layer, the platform lowers 0.3mm, and the head lays down another layer. Molten plastic sticks really well to other plastic, but that still leaves the first layer as a problem: The plastic won't tend to stick to the bed, it'll tend to stay on the nozzle and glob up. So you have to heat the bed (hotter the better, 90-110 C). But you also want the print to detach cleanly when it's done, and not stick to the metal bed. So, tape.
It came with two squares of Kapton tape, a nice smooth tape with a super-high melting temperature, because you're essentially covering the surface of a griddle with the stuff. The problem with that is, it scratches and tears really easily (like when you're prying the build off afterwards) and there's a price factor: not only is it like $40 a roll, but nowhere around here sells it.
Enter blue tape. Painter's tape. Smells terrible when you heat it up, but it's super cheap, and prints seem to adhere to it at a lower temperature (which means the bed heats up sooner, and there's less danger of burning out the heating element.
So, I made this model on Tinkercad and printed a bunch of variants. The final verdict seems to be that making the hole 1mm larger than the peg yields a hole/peg that fits snugly but not too snugly to turn, and 2mm is loose enough to be a wheel for a toy car or something like that. Next stop, gear town: I have a bunch of stuff (all public domain, naturally) about the geometry of gears and the designs of machines that cut them. It's not as simple as you'd think to make them mesh correctly.
Also this weekend I messed with the bed:
The way the printer works is, you have a print head that extrudes plastic and moves in X and Y, and a flat metal plate that it extrudes it on to that moves in Z. So the head lays down a layer, the platform lowers 0.3mm, and the head lays down another layer. Molten plastic sticks really well to other plastic, but that still leaves the first layer as a problem: The plastic won't tend to stick to the bed, it'll tend to stay on the nozzle and glob up. So you have to heat the bed (hotter the better, 90-110 C). But you also want the print to detach cleanly when it's done, and not stick to the metal bed. So, tape.
It came with two squares of Kapton tape, a nice smooth tape with a super-high melting temperature, because you're essentially covering the surface of a griddle with the stuff. The problem with that is, it scratches and tears really easily (like when you're prying the build off afterwards) and there's a price factor: not only is it like $40 a roll, but nowhere around here sells it.
Enter blue tape. Painter's tape. Smells terrible when you heat it up, but it's super cheap, and prints seem to adhere to it at a lower temperature (which means the bed heats up sooner, and there's less danger of burning out the heating element.
