This ball mill was made for grinding sand and cleaning objects like rusty bolts. It works but takes a very long time to grind sand down, this is because of the size of the balls are too small. Getting larger balls will help.
Some professionals that design and manufacture mill for industry helped in the design of the lifter and the correct speed for milling. The professionals were interested in how long it would take for the lining of the mill to be worn out. This is yet to be tested.
The parts can be found here: https://www.thingiverse.com/thing:2713357
See more what I have done: http://tinkersprojects.com/Circuit and program:
After powering the mill with 12V DC power, settings can be seen/changed using the LCD and can be altered using the 3 buttons (up, down and enter). Speed and duration are the 2 settings that can be set to control the mill. While the mill is in operation, the LCD will display the current speed and the time left of milling. By pressing the enter button, the mill will stop.