Mostly printed adjustable rotary tumbler

thingiverse

This tumbler can be mostly printed, with the other required parts likely found or salvaged easily. The support can extend and shrink to fit various jar dimensions, requiring only a gear belt for each jar. Adjust the distance between wheels/gears large enough to keep the jar in place without excessive pressure. I built this to experiment with 3D-printed part smoothing, but I have mixed results so far: it takes days to see a difference, probably because the parts are very light and friction is gentle, and sharp corners tend to be rounded. Maybe it can be better suited for other purposes... All you need is: * A small electric motor (e.g., the tray opening motor from an old CD/DVD drive) * A power source * A jar with suitable dimensions for polishing items * Some abrasive material, such as silicon carbide Some parts are customizable to fit the motor and jar dimensions. You'll need to customize: * The motor support (to fit the motor diameter) * The pinion (to fit the motor shaft diameter) * The jar gear (to fit the jar outer diameter) * The paddles that go inside the jar This can be done with the OpenSCAD customizer after installing [this gears library](https://www.thingiverse.com/thing:1604369). Gears do not render in Thingiverse customizer as the library is not installed. Many other parameters can also be changed easily in the source code if needed. ### Instructions First, choose a motor to power the tumbler. I used an old CD-ROM drive tray motor with a diameter of 23.8mm and a height of 12mm, rotating at approximately 4000 rpm at 3V (the lowest transformer voltage I have), consuming about 0.2W with a tiny jar. Depending on the motor rotation speed and desired jar size and rotation speed, the number of teeth of the "large_gear" part can be adjusted to change the reduction ratio. I found two turns per second reasonable for a very small jar (5cm diameter). Print the required parts: * 1x axial_bar * 2x transversal_bar * 2x wheel (or wheel_solid) * 2x small_gear (or small_gear_solid) * 4x support_1 * 3x support_2 * 1x support_2_motor (customized) * 1x large_gear (optionally customized) * 1x pinion (customized shaft diameter) * 1x jar_gear (customized) * 3x jar_paddle (customized) All parts can be printed without support, but a low speed is recommended to ensure the teeth are as precise as possible. Almost no post-processing is required except some filing for adjusting the shafts to the holes. Assembly is straightforward: snap together the support parts with a wheel or small gear in-between, gluing is also possible. The pinion should be glued on the motor shaft (otherwise it will become loose after some time). The jar gear can be glued if it's too loose. The paddles are glued inside the jar. PLA works well (maybe a lower friction material such as PETG would be better). The curved beams for wheels and gears provide some elasticity, but they're fragile and difficult to print right; a solid version can be used instead for simplicity. I also put oil on the moving parts to lubricate them. Once everything is assembled and powered, watch the barrel rolling and be patient...