Monday, March 12, 2007


Moulding thin walled gears, succeeds (!)

Moving the X & Y on darwin to resoultions of 0.1 mm directly from a 400 step motor equates to drive gear diameters of about 12mm. For Darwn's Y, these need to sit on a ø8mm shaft. This means very thin walled gears. Vik's idea of moulding the capa into the belt to create the toothed gear has worked brilliantly in the past so I was trying to do that again. But this time things got tricky because stuffing the capa into such a small volume was extremely tricky (see pic).

The final solution was to pack the capa into a former section wich held the teeth, mount that on a blade section with a ø8mm hole, hold the two concentrically in a pot and ram a file'd-up 8mm spike through the lot. Pre-packing the former guarantees the toothed impression, as does the angle of the spike, the blade nips off the excess, and the whole lot is easy to break apart after the capa's set.

After a bit of trimming, Bob's your uncle, as we say over here. (And, if your from the wrong part of over here, bob can also be your dad).

Nice going eD. I guess you need to put a lip on the other end now. Any worries about the longevity of gear that thin?
Lips - managed to RP up a snap on circlip which does the biz.

Longevity - good question! The capa's pretty hard stuff so we're optimistic. [I guess the repeatability program could test it to infinity and beyond, so me might have to leave it over a weekend]. Curse, if it did wear out, it's nice knowing that all you've got to do really is put the kettle on!
An ordinary M8 washer and splattering of CAPA might also make a nice lip.

Vik :v)
Just to follow up on the working lifespan of these gears - as of the date of this posting I'm still using them!
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