Tuesday, July 04, 2006


ARNIE z-run performance

ARNIE's studding tranmission upgrade was tested on Friday. The stepper motor was directed to rotate 1000 steps and back again 10 times with a delay of 100 cycles per step. A calliper was used to measure the position of the z-bed at the start and end of each run. The figure below shows the results for this test.

It shows a variation of ± 0.04 mm and ± 0.03 mm variation for both start and end positions respectively using the studding transmission for the z-bed. Not bad, 'specially since we're aiming for an initial accuracy of 0.1 mm. Happy days.

BRILLIANT! Congratulations! :-D
So how are you determining that you've got back to start? Simple counting or a limit detector?
No - Ed bolts a digital caliper to the machine, which is accurate and repeatable to 0.01mm.
I'm impressed with the accuracy, great stuff. I guess with gravity providing the antibacklash, it will stay accurate even as the threaded rod wears out with use.
Well, there's actually an anti-backlash mechanism built into the design to give gravity a helping hand. And I'm sure that's the reason for such good repeatability. The mechanism is simply: driven nut forced down onto the thread with a spring pushing against a trapped nut which travels at a set distance with the driven nut. That might be easier witha picture... let me know
Pics are good! I'd also like to see a pic of how you bolted that digital caliper onto your z-stage. I'm thinking about buying a digital caliper. :-)
Ed, Yes, that would be nice to see more photos, I think I half understand your anti-backlash device, but would like to understand the other half! ;)

Plaas, and digital calipers are so inexpensive, I could of bought three for the price I paid for a mechanical one 20 years ago. Argh!
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