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View Full Version : How did they make this?



lakeside53
08-02-2012, 11:58 AM
http://www.youtube.com/watch?v=sMfjangd0ds

dockterj
08-02-2012, 12:16 PM
two ball bearings and a wire edm?

gwilson
08-02-2012, 12:20 PM
Could have been done in Photoshop. Look carefully at the surface and you'll see darker areas where the shapes are made.

dockrat
08-02-2012, 12:34 PM
wire EDM See 3:20 in this video

http://www.youtube.com/watch?v=FfNPkqDOqd4&feature=relmfu

Evan
08-02-2012, 12:37 PM
That alone is a good enough reason to build a wire edm.

cuemaker
08-02-2012, 01:36 PM
As a non machinist.. here is my answer (guess)....

EDM the elephants out of 1 block, then EDM the reverse of the elephants out of a different block, taking into account waste and wire thickness for a close fit..

Then mate the 2 parts, doing whats necessary for fit where. Then take the whole block and turn round.

Dan Dubeau
08-02-2012, 02:04 PM
two ball bearings and a wire edm?

My vote too.

Not really that difficult really, just an impressive visual display. Fixturing would be the fun part, but I'd just weld a stub on each sphere, and grind/polish it off after.

George Bulliss
08-02-2012, 02:16 PM
Definitely a wire EDM. Every EDM both at IMTS will have lots of these types of things for people to play with. I know the Mitsubishi machines used to come with some assorted programs loaded for making little items like this. I’ve been to a few classes and we always made a few similar items to take back to the owners to help justify the enormous chunk of cash they shelled out for the machine and my training.

Although it’s a fairly common trick, getting that kind of fit between the two pieces takes a good amount of skill. It doesn’t take much to leave a visible line between them. If these pieces were machined as round, it would be even trickier due the constantly changing cross-section during the cut. Picking up a round piece close enough to make the uncut surfaces match would also be difficult.

Although they may have cut these things while round, I think there was at least a little post finishing work done. No matter how careful you are, you will get a small (very small) amount of erosion along the corner between the cut and uncut portion. Also, if you wanted the fit to remain tight, you would need to very lightly stone (or light bead blast) the EDM surface and leaving a sharp corner would be impossible to achieve.

With the things I made, we typically tossed them on the surface grinder to dust the parting line clean. It didn’t take much, probably a half-thou, so it wouldn’t be too hard to polish up the ball after machining.