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icon9.gif  Tiny Ping Pong Ball (10 or 20 mm) [message #67836] Sat, 11 May 2013 20:11 UTC Go to next message
avatar brockm87  is currently offline brockm87
Messages: 3
Registered: February 2013
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Junior Member
Hello,

I'd like to print some very small ping-pong-like balls.

The goal is for them to be as smooth as possible and be very lightweight. (definitely hollow)

Is it possible to do this with the strong and flexible material without leaving a hole in the ball? I know it says something about an escape hole in the design guidelines so maybe I need to do this with another material?

If it is impossible to print a completely enclosed hollow object with strong and flexible, would this work with any other material?

Any suggestions are much appreciated.

Thanks,
Brock
Re: Tiny Ping Pong Ball (10 or 20 mm) [message #67838 is a reply to message #67836 ] Sat, 11 May 2013 22:09 UTC Go to previous messageGo to next message
avatar mkroeker  is currently offline mkroeker
Messages: 1947
Registered: June 2012
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Shapie Expert
What is the intended application ? Building little spheres in thin layers does not strike me as particularly efficient, and indeed you
would trap support material inside.
Would styrofoam balls be sufficient ? Those are readily available in many sizes for various craft projects.
Also, hollow plastic or rubber balls have several industrial uses - your main problem there would probably be
to buy less than a truckload of them, but the first google hit for "hollow plastic balls" offers trial packs (100 pieces)
of e.g. 10mm diameter polypropylene balls weighing .2 grams for $37.50.
Re: Tiny Ping Pong Ball (10 or 20 mm) [message #67844 is a reply to message #67838 ] Sun, 12 May 2013 05:08 UTC Go to previous messageGo to next message
avatar brockm87  is currently offline brockm87
Messages: 3
Registered: February 2013
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Junior Member
Hello mkroeker,

Thanks for the quick reply.

I need the balls for an aerodynamics demonstration. I agree, it wouldn't be efficient normally, but I'm not yet sure of the exact size or weight of the ball I want, which is why it would be much easier print a few different test balls. However, if it is impossible to print, then yes I will go the route of premanufactured balls. I won't need any more than 1 of each size I try though, so it will be a pain.

I did already see what you googled, but I was just posting here to learn more about if any of the printing methods on Shapeways could print a hollow ball without holes. If not that's fine, I will find other less efficient solutions. Smile

-Brock
Re: Tiny Ping Pong Ball (10 or 20 mm) [message #67847 is a reply to message #67836 ] Sun, 12 May 2013 14:08 UTC Go to previous messageGo to next message
avatar barkingdigger  is currently offline barkingdigger
Messages: 122
Registered: January 2013
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Senior Member
If they must be hollow, you could print two half-shells and snap them together. For modelling tyres I do this and add a ridge to one part and a groove to the other so they fit together exactly. With clever design, the volumes of ridge & groove would cancel out to give the same density of "wall" as the rest of the ball, so shouldn't affect balance. (Make the ridge on one part, and then "subtract" a copy of the ridge from the other part to get an exact fit.) However, this approach will be an issue if the balls are subjected to impact forces, since using superglue rather than a dry-fit would a) add eccentric weight along the seam and b) probably fail under stress.

The other issue is smoothness - printed items are grainy and can be "stepped" in some of the materials. You may need to sand/polish them for best aerodynamics...
Re: Tiny Ping Pong Ball (10 or 20 mm) [message #67871 is a reply to message #67847 ] Mon, 13 May 2013 03:14 UTC Go to previous message
avatar brockm87  is currently offline brockm87
Messages: 3
Registered: February 2013
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Junior Member
barkingdigger,

Thanks, those are some great ideas! I didn't think of doing it in two halves like that, very clever!

I'm not worried about impact, and it's ok if the balls need to be polished a little after printing. With the technique you suggested it should be very easy to try different sizes and weights. And you're right, with that technique, the balance should stay exactly the same.

Again, thanks a lot for the help, you're advice was just what I needed!

-Brock

 
   
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