djf21
off to a rocking start
Member since March 2016
Posts: 1
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Post by djf21 on Mar 23, 2016 9:36:36 GMT -5
I'm completely new to rock tumblers, and I had a manufacturing problem that I wasn't sure could be solved by using a rock tumbler. I just wanted to run it by some people experienced with rock tumblers to see if it would be feasible and how would be best to go about it. I have these slightly non-spherical plastic balls some of which are between about 1/8" to 1/2" and some of which are made out of PVC and some from teflon. I want to be able to shape them so that they are more spherical and have a smooth surface. The most important feature being that they are made to be very spherical. I was thinking of trying to use a rock tumbler to achieve this, but I wasn't sure if this would work since I have never used a rock tumbler before and as far as I know they are only intended for rocks. Would this work? And if so, how would one go about it? What type of rock tumbler would be best? And what type of abrasive material should be put into the tumbler to shape the aspherical plastic pieces I put in it? Alternatively, I was thinking of using a sphere machine by Covington www.kingsleynorth.com/skshop/product.php?id=46522&catID=1040, but it seems to be rather expensive and it doesn't seem to be able to grind down below 1/4" which I might want to do. Would using a rock tumbler give just as good results and be cheaper?
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Post by Drummond Island Rocks on Mar 23, 2016 9:54:20 GMT -5
A rock tumbler is not a good solution. Rock tumblers create random shapes and sizes with zero control. You said that making them "very spherical" is important so as far as rock grinding equipment goes a sphere machine is the only solution. There are bead mills but even those do not create "very spherical" shapes. bead mill covington-engineering.com/bead-mill/Chuck
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Post by jakesrocks on Mar 23, 2016 11:59:18 GMT -5
I'm not even sure that a sphere machine or bead mill would be the answer. With either you need to use an abrasive grit. Plastics being soft, the grit will be forced into the plastic balls. You may end up with plastic spheres which are full of very abrasive grit.
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Mar 23, 2016 20:50:14 GMT -5
PVC and Teflon are completely different animals. PVC is rigid and can be altered by abrasives just like how you can cut and sand sprinkler pipe. But Teflon is basically a reeeeally slow moving liquid. That why it is used as a lubricating surface for non stick cookware and other places where a pseudo-surface is desired. Teflon "cold flows" meaning it will move away from any applied pressure, just like nylon which is in the same family. Therefore, attempting to shape teflon by abrasion is somewhat futile since it will cold flow back into the shape it wants to be.
The only way to get perfect spheres that small in plastic is to shoot the plastic into perfectly spherical mold cavities in the first place. Teflon wouldn't stay perfectly spherical even if you molded them that way. Teflon is really weird stuff. I used to work with chunks of it in a lab and pieces would become distorted if they sat on the shelf in one position too long. A sphere sitting on the shelf would quickly develop flat spots.
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Post by manofglass on Mar 23, 2016 22:17:15 GMT -5
Use a mini wood lathe
Walt
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