Rock Tumbler





Introduction: 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.

Step 1: Getting Parts

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

Step 2: Wood Construction

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.

Step 3: Electronic

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.

Step 4: Add Stones

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....

Step 5: Wait

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):

Step 6: 1 Week Tumbling

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



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    Great project! Just wondering--how are you powering the motor for this project? Are you using an underpowered (lower voltage/amperage) power supply, or are you taking the power from the printer itself? I'm stumped on this. Also, do you have any idea what "GAIN" could mean on the pinout for a BLDC motor?

    As a part-time gold prospector, the old-fashioned way, my first thought in pouring out the grit was to grab a gold pan. That is the ideal receptacle for separating water from grinding media, and cutting down expensive grind media replacement. Then the grit can dry in normal, ambient air, and be ready to reuse. :) I also recommend cutting off the "elbow end" of a plastic clothes hanger and wedging it up under the lip of the inside of the tumbler, permanently so that it acts as a lift. In particle physics/material handling science we learned that the maximum "grinding" occurs at what is called the "TOE" of the revolving drum. That is the point at the bottom of the tumbler where the most impact
    is generated by the weight and movement of the charge, in this case, rocks that need polishing, occurs. This is where gravity loses out near the top of the revolution and cascades down to the bottom of the tumbler/barrel/mill. An "elbow" lift device such as I've incorporated into mine, is really useful in that 'crashing into the toe" area sweet spot in grinding/polishing. THANKS for this -ible. Voting for you!!!

    Ballmill Toe.jpg

    A few years ago I had a bunch of those BLDC motors I pulled out of some heavy duty office laser printers, but I had no luck getting them to run despite my best efforts, even looking at the data sheet for the driver chip! I knew I had to send pulses, but I still could never get it to work. Now with this 'Ible I have the missing piece of the puzzle - the need to send a "START" pulse to initialise the chip - but I no longer have the motors :-(

    I take it these can be found on Ebay for good prices?

    5 replies

    i just had quick look on ebay, single motors like mine on ebay are quit expensiv. If you need to buy something you should better take a gear motor for around ten bucks

    I had a look on ebay minutes after posting my comment, and they are indeed quite pricey :( Though not *so* pricey that it's a viable option. I could use a cheaper motor like a gear motor or synchronous motor, but the appeal for me is the way these motors run with the driver circuit generating the various waveforms.
    For me it *looks* cooler :P

    * that it's not a viable option

    I meant to say :P

    Two words: Thrift store.

    Or garage sale. XD

    I rather fear I'd have to buy an entire laser printer. No mean feat getting that back home! Though it would yield some amazing parts :D

    Pretty cool.
    I must finish mine off. It's been sitting for about 5 years waiting!

    You could use a microwave AC motor! Much simplier

    I suggest to avoid using the arduino as not many people have spare arduinos. It would be nice if you could make use of parts from the pronter itself.

    Thank you very much for this instructable! Your stepper driver is a bit of overkill for a rock tumbler, but I had not before known how to hook up a commercial printer stepper. I grabbed the nearest one to my desk and sure enough, the pins are labelled as you indicated. If I can drive them this easily, I could put together a CNC router from several of these and drive the motors with a cheap ebay breakout board.

    The tumbler is going to be fairly slow with so much rock- a rough-stone tumbler usually uses maybe 1/3 full and a baffle inside so the rocks fall further when they slide and hit each other harder. Your tumbler would be a good finishing tumbler for mostly-smooth hard stones and for tumbling soft stuff like turquoises and malachites.

    1 reply

    The Motor i found is indeed not a stepper, it is BLDC Motor. The included electronic is not good for use in a CNC machine. But it is a good motor for running all day long as it has no brush that can be worn out.

    This is a very unique way of making a tumbler. Great use of resources! Very clear write up, thanks for sharing!


    "Put down"? Are you serious? Please point out any "putting down" in my comment. You must view all the world through the very narrow aperture of your own opinion.

    2 replies

    It was perhaps the WAY you pointed out an alternative. The site was a great resource- now deleted. Some people are already self conscious about putting themselves out there, but good for you for not having old stuff around- either you choose well or edit frequently. Apparently you are not saving everything...just in case....

    Agreed. Pointing out you can buy a cheap motor (And where to find it) to replace the electronic assembly moved this project from "interesting" to "I want to make one ASAP".

    Great project! I love that you used the parts out of an old printer. So resourceful!

    It would be neat to see a few photos of some finished stones you tumbled in this, if you felt so inclined to add some. I'd love to see how they turned out!

    2 replies

    I will add pictures soon, need to wait some weeks. I will have a peak on weakend on how is it in the inside...
    Next time i will try to polish broken colorful glas pieces, they should also look nice in the end.

    You've got a good thing going there !!! Being 'of age, (don't ask)', I'm not real familiar with these techno motors and stuff. I took an old 12 volt motor, put a rheostat on it. It does take a bit of time to get a constant speed. I used basically your design and let the 'picker' in me find the parts I needed. Thanks for the write up and the pictures !!!