Cheap jar rock tumbler, drum polisher

thingiverse

A super cheap, low material rock tumbler/polisher. Designed to use one of 3 low cost 5v hobby motors! This is an advanced project, some knowledge of electronics and mechanics are required. There are other tumbler polishers on Thingiverse, I found these either need a lot of filament, metal drums or specialist motors. As I was just requiring something small and cheap to polish metal filament prints I decided to design my own using cheap parts I had to hand. I also wanted to build 4 polishers so I could have parts in every stage of processing so it needed to be as cheap as possible. Overall I found the geared 130 DC motor design to work best, with high speed and good reliability. Construction notes:- It is important to make sure the horn parts that attach the jar lid to the motor is perfectly centered to the jar lid, if it is not, it will cause a lot of wear on the motor and gearbox. This may cause the gearbox to fail or stall. I used this printable centre finder to help https://www.thingiverse.com/thing:3283699. When pushing the horn/lid assembly onto the gearbox axle, do not it push it all the way home, this allows the horn to flex slightly and make up for any inaccuracy in the horn mounting. This part will suffer high wear, and will need replacing from time to time. Seal holes drilled in the jar lid, the process of tumble polishing produces fine dust that WILL get out of any gap. It's probably not a good idea to breath any dust created by tumble polishing! For geared designs I suggest you lubricate the gearbox with some light oil before use to increase the gearbox lifespan, this is a demanding use of such gearboxes. DO NOT USE WD40, this is not a lubricant! Use the shims provided in the bottom of the bearing clamp parts to make sure the jar is central to the gearbox axle, and as level as possible to prevent stress and binding. The shims allow a variety of jar diameters to be used you should be able to get away with 87-79mm diameter. As mentioned before it's essential to make sure the jar is level and centered on the gearbox axle. To glue the agitators to the inside of the jar, 2 part epoxy glue works well, make sure the inside of the jar is clean and grease free before gluing. Agitators are not required, but will speed up the polishing process. Agitators will wear out over time. Depending on the length of your jar, 1 or 2 bearing assemblies are required, I found 1 to be the easiest to set up and level. As jars are not precision parts, you will probably find different configurations of shims are required if you use 2 bearing assemblies. In use:- Wear a dust mask when handling polishing medium! Do not overload the polisher, keep the number of parts low and light, only 2 heaped teaspoons of media is required per process. Depending on materials to be polished, patience is required, it may take days to complete polishing cycles. Surprisingly I found rocks polished faster than PLA parts, go figure. Polishing medium:- I Have used 3mm bearings, builders sand, and National Geographic silicone carbide grit to good results https://www.amazon.co.uk/gp/product/B01MRKI4W0 Different mediums produce different effects, research what is most suitable for your requirements. I found it useful to place the whole assembly in a plastic food container to capture stray dust, this also stopped the motor horn sliding off the motor axle as it inevitably wore. Required for all designs:- 2x or 4x 608 bearings. 1x ~85mm diameter jam jar or similar. 4x M3 4-5mm nuts and bolts. 1x M3 14mm nut and bolt. 1x M3 20mm nut and bolt. 2 part epoxy glue (optional) Printed parts:- 1 or 2x part bearing clamp.stl 2 or 4x part bearing holder.stl shims as required. 3x part agitator.stl (optional) 100mm or 160mm frame.stl 5v power supply, I leave connection details up to you! For 3d pen motor design (https://www.amazon.co.uk/gp/product/B01GZWN9BS):- 1x small motor horn.stl No other parts are required. Be warned this is a delicate motor with a delicate gearbox, it is recommended only a lightweight plastic jar is used for the polishing drum. For 28BYJ-48 stepper design (quite slow, requires Arduino skills) 28BYJ-48 stepper motor. ULN2003 driver board Arduino or similar + stepper program (provided in files). 2x M6 nuts and bolts. Printed parts:- 1x stepper adaptor.stl 1x stepper horn.stl For geared DC 130 motor design (recommended design) Geared DC 130 https://www.amazon.co.uk/Gikfun-3V-6V-Motor-Arduino-EK1300x4U/dp/B07GGF4KLR 2x M3 5mm self tapping screws 1x 25w+ 10 to 15ohm shunt resistor in series to reduce speed.https://www.amazon.co.uk/gp/product/B07H342P28 Printed parts:- 1x gearbox horn.stl 1x gearbox mount.stl Some parts heavily modified from https://www.thingiverse.com/thing:3438837