Rock Tumbler

With a Rock Tumbler you can clean all sort of metals and make round and shiny rocks. Old metal parts look like new after some hours in the tumbler with corn cob or walnut shells. For real rocks you need something stronger like SiC Powder, but we will come to that later.

I used on one old printer, a Samsung CLX-2160 multifunction laserprinter. It has nearly all the parts needed to build a rock tumbler inside.

- Strong 24V Servomotor including a controller PCB

- Several metal rods with rubbers to hold the drum

Some old wood is transformed in to a frame for the rock tumbler. Screwed together with 4 screws from the underside. The motor position needs to be adjusted so the gear fits.

The motor controler needs a clock signal to maintain his constant speed. The cheapest solution would be to use NE555 or someting similar to generate a clock around 500-1000 Hz, but i used an abandoned arduino for this. Maybe i can add reversing the direction after some minutes to get a better result.

The motor controler has 10 PINs:

1: CW/CCW change the direction of the motor. Connect to GND or to a PIN of your Arduino

2: CLK Clock signal to set the desired speed of the motor. Around 400 to 1000 Hz.

3: READY We don't need this.

4: START We need a single pulse here to start the motor. Connect to arduino

5: 5V connect to the 5V of the arduino

6: SG Signal Ground connect to GND of arduino

7,8: PG Power Ground connect to GND of arduino

9,10: 24V Powersupply for the motor. Connect with VIN on the arduino board, then you can supply arduino and motor with a single 12V powersupply.

For the Drum i took a pice of drain pipe (100mm diameter) and two endcaps. You have to drill a hole in one endcap otherwise you can not close or open them, because of the airpreassure.

Then you fill 1/2 or 2/3 of the drum with rocks add 3-4 soup spoons of SiC 80 milling powder and add water just up to the upperside of the rocks.

Close the drum and lets start....

Depending on your rock you need to tumble 2 weeks withs SiC 80 grain, then wash the stones, carefuly remove all the grains and go further with SiC 220 grain. Wait another week then one more week with SiC 400 grain. With SiC 800-1000 grain it will take another 1 or 2 days and then 1 day to polish with polishing powder X3.

Take care not to flush the stone powder and grain to your waste tube as it will harden there and make nasty things...

May be some more Information (in german):

http://www.wenger-online.de/blog/2015/01/05/trommelschleifmaschine/

After 7 days of tumbling... i think i will need minimum another week to get round stones. I will publish more pictures soon.