Smooth-O-Matic Parts Polisher and Rock Tumbler

by 2n2r5, published

Smooth-O-Matic Parts Polisher and Rock Tumbler by 2n2r5 Apr 8, 2013

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Tired of having to use a exact-o knife to clean off your 3d printed parts?

Well then, just throw you parts in a 1 quart paint can with some rocks, wait several hours and voilà! You have partially cleaned parts that still need to be deburred. err, well .... Maybe I did something wrong. I am sure you will have better luck.

This is a video of it working.

This is a great low cost DIY solution for those who don't want to pay an arm and a leg for a rock tumbler. I have had mine running now for a coupler hours. I don't know if the parts are getting cleaned but I do know that it seems to be functioning as expected. I will probably be selling the kits. I don't really know what to use as an abbrasive. I went with a bag of small gravel from home depot. The gravel doesn't seem to work at all for me. It might just need a lot more time. I think I will head to Harbour Frieght and get a bag of walnut shells tomorrow.

REV 2.0 Coming Soon

Improvements in version 2:

  • addition of a 3rd gear
  • a new frame
  • all new gears
  • Gear box cover
  • Electronics upgrade including Speed control*

*depends on if the parts come in before I am done


REV 1.0

Parts List:

Home Depot -

  • 3/8" x 36" Round Rod - Aluminum
  • 1 1/2" x 2' PVC Pipe Section
  • 3M Safety Walk 2 in. x 15 ft. Step and Ladder Tread Tape
  • 1 Roll of Duct Tape (if you don't already have some laying around. You won't need much)
  • 2 x BEHR 1 Qt. Metal Paint Bucket and Lid

American Science & Surplus (ASS)


Settings: 2 shells, 20% infill, .3mm layers


  • 1 x Frame_Front or Frame_Front_Half_Width (half width is shown)
  • 1 x Frame_Back
  • 4 x Roller_End_Cap
  • 1 x Motor_Housing
  • 4 x PVC_Bushing
  • 1 x Motor_Gear
  • 1 x Roller_Gear
  • 4 x Can_Fins_Insert (2 per can)



  1. Cut 24" PVC Pipe into 2 equal pieces of 12" long
  2. Cut 2 x 16" lengths from 3/8" Aluminum Round Bar ( this will be a little long but will be trimmed after you dry fit everything)

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It doesn't really work - doesn't cut the plastic. The only really effective media I've tried is tiny (#2 and/or #4) flathead brass wood screws, but you need a lot of them for a good-sized tumbler.

I made one of these and the motor died after 1 day of use. Using a more heavy duty motor might be a good course of action. Otherwise it worked well. Nice design.

Any chance to put up some pictures? I would love to see some results. I figured the motor would have longevity issues. Which motor did you switch to? I haven't looked at this project in quite some time. I might have to revisit it and update the project again.

So... did you ever get this to work with 3D-printed parts?

Rock tumblers work because rocks are heavy... They bang and grind against each other.

So to polish plastic parts I think you will need a fine grit AND heavy rocks/things of some sort.

I've been looking at lapidary parts finishing for a while now, but haven't yet jumped in and spent money due to a lack of knowledge. From what I've gathered, I think a vibratory machine might be better suited to printed parts than a tumbler. Honestly I think a blasting chamber might be best but I can't have that amount of mess and dust in my shop. I'll be interested to hear your results with various media.

It may be my browser, but I believe the instructions stop at step 2. Just wondering if there were completed instructions?

This looks exactly like a lego ball mill i designed, were you per chance inspired by my design?

Damn, i was planning on soon making a 3D printed similar version.

Some helpful tips from experience with my own mill. your barrel may gradually shift to one end or the other if its not perfectly flat, then it will fall off. to fix this, just put a small lip on the outer segments of the driving tube, even a smooth barrel can do surprising damage in an hour of rubbing on ABS. Also, use a brushless motor for heavier loads, brushed motors wont last too long if the are drawing a fair load, such as if your using this for milling aluminium powder for example.
Lastly, lubricate every moving part, abs does infact wear, even the supernaturally tough lego ABS does.

Edward R. Swoboda, of Los Angeles supposedly made the first in 1950 and I'm willing you haven't been waiting 50 years to make a 3d printed version. The design you want to take credit for is probably the most common one there is.

What is the best media to use for tumbling PLA any suggestions on where to get it? Cheers!

I'm planning to try regular old sand.

well, if you knew anything about how lapidary polishing works, youll know that anything softer, will polish the surface and grind itself, anything of equal hardness with polish both surfaces, and anything harder will grind the surface and polish itself. aka, quartz will polish quartz, steel will grind away aluminium, and plastic will plolish, and not grind away, plastic


This site suggests hardwood to finish plastics. I think I will try that next, Unfortunately, I won't be able to try anything for a couple weeks. If someone else does. Please post your results.

Harborfreight has media for polishing or cutting.

Wow, they have a dual barrel tumbler for almost as cheap as I made this one! I know it's not always about the cost. It's about taking pride in building something yourself but that's kind of discouraging. Looks like I better make mine work very well. On that note, I am currently working on a fix to double the speed of the rollers. You can see what I am printing @ http://2n2r5.nethttp://2n2r5.net:8585 If all goes well I will update the files and provide the fix as a package.

="thingiverse-2ab65a72cef0f72196d92ae1eab2580f:disqus" href="http://disqus.com/thingiverse-2ab65a72cef0f72196d92ae1eab2580f/alphapirho I have thought about that. I don't have too much of a choice with the current setup. The container is some where around 11 RPM right now. I would love to double that but I don't think I have enough room to double the size of the drive gear. I will look into it though. Thanks!

You may also want to experiment with different speeds. Maybe something higher like 60 to 100 RPMs on the container.

="b93dc36bbaeb6ce2eb4dd9ad839aac8c:disqus" href="http://disqus.com/guest/b93dc36bbaeb6ce2eb4dd9ad839aac8c/Mike Audette Great idea for the fins. I am making a 2 piece insert for the paint cans. I have uploaded the STL for the insert

Try a #10 can or add some small fins in it so the media tumbles instead of rolling.

="thingiverse-492114f6915a69aa3dd005aa4233ef51:disqus" href="http://disqus.com/thingiverse-492114f6915a69aa3dd005aa4233ef51/yzorg I think your right about the gravity being an issue. That might just mean that I need to use something that is very abrasive for a longer period of time. I could always go with beach sand or something of that nature. I will pick up some materials today and let you know how they work. I am going out of town for business so I will try to get this done before I leave.

i dare to say that you wont find a way to skip the exacto knive completely.

the tumbler will grind material from all outer sides.. i think PLA is to soft to be "tumbled" in useful time.. or is even too light for the gravity to force it against the abrasive hard enough.