I use this to smooth out my metal fill prints. At some point I might even try it on some gemstones as well. It works very well and is fairly silent. I had to try a couple of different motors. With this direct drive solution you need a pretty powerful geared one.
Print the main parts with support. No support needed for other than that. I printed the motor block in Ninjaflex to make it noise cancelling. But you can print the motor block with other filaments as well.
The ninjaflex infill for the box is not mandatory but it reduce the noise significantly and gives some friction in the box. That friction makes the tumbling more effective.
It is divided into two parts so that it is possible to print on smaller printers as well. I printed mine on my LulzBot Mini. It has a max printing size of approx 15x15x15 cm.
I used the 72 rpm version of this motor:
That motor is brushless, reliable and very powerful. I run it on 12 V and it gives me approx 40 rpm at that voltage. The tumbler will work well with a weaker and not as expensive motor, but if you are going to use this seriously the tumbler will run for hours and hours. Even several days. So I think it might be wise to invest in a good motor.
But there are cheaper alternatives out there that might be powerful enough and still actually fit more or less perfectly in the same motor block:
Aim for 30-60 rotations pr. minute.
The way I have designed this with a separate motor block makes it easy for you to make your own special motor block without having to redesign the whole construction. The motor block is 50 mm wide, 53 mm deep and 30 mm high.
Standard 250 g ILLY that is available more or less all over the world:
The box outer dimensions are 90 mm diameter and 144 mm height.
I use loads of these to smooth out my metal fill prints:
Motor block: https://a360.co/2Hji8CR
Center Parts: https://a360.co/2GXgsPW
NinjaFlex Infill: https://a360.co/2HkibOG