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A small milestoneMonday, March 9. 2009In which your narrator cuts a power transmission gear out of
3/8" inch HDPE, the thickest milling job yet...
Nophead went over my I2C controller board layout and showed me how to deal
with back-EMF with diodes and a zener diode this afternoon, so that I know now
what to do with that. His electronics advice is priceless.
This evening I did several trial milling jobs to get the diameter right for
the stepper gear for the tin can stepper axis for Tommelise 3.0 and, possibly,
eD's new wedge Darwin 2.0. I wanted the gear to have a tight, compression fit
with that weird half inch shaft sleeve on the old Airpax stepper. After two
tries I got that right and then set out to see if I could cut the gear out of
heavy, 3/8" HDPE. I wanted the stepper gear thick so that the lead screw gear,
which I will cut tomorrow out of 1/4" HDPE won't have to be in perfect alighment
with it.
In any case, it took me about an hour and a half to cut the gear. It came
out looking pretty good.
Here you see me using an ordinary C-clamp to press-fit the gear onto the
stepper shaft sleeve. 
The nice thing about compression fitting is that you don't need set screws or glue or anything of the sort. You just put the gear on the shaft under compression and it's on to stay. I'd have to cut that wood mounting block apart to get the stepper out of there. That or cut the gear apart. Trackbacks
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Forrest, you could use a lighter, or a propane torch to clean up all the hairs on your milled parts. Pretty much just cosmetic though.
Yeah, I could. I don't bother with stuff like that, though. I take the old Russian engineering approach. If it works, it doesn't have to be pretty. That puppy works. :-D
For your next mounting block you could cut a slot from one edge to the point where the stepper axle comes through so that you can unscrew the stepper and just slide it out rather than destroying the block, the gear or both.
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