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| awemawson:
Bill it's a long story but covered in depth here: http://madmodder.net/index.php/topic,9439.0.html The axis is travelling too far - the only possibilities that I see are: a/ gear ratios wrong (seems very unlikely) b/ obscured 'gap' in encoder disk so loosing one or more pulses per rev. I was about to delve into that thread on building the 4th axis to refer back to the ratios to see if b/ is mathematically likely :coffee: |
| awemawson:
OK so the encoder is 125 counts per rev It is tooth belt driven by the servo motor 20:25 reducing the count to 100 per servo motor rev The servo motor is geared to the worm gear 4:1 in a low backlash set up The worm to the worm wheel is 90:1 - again low back lash set up so 90 x 4 x 100 is 36,000 encoder pulses per axis rev Now to be out 1/2% seems very strange unless the worm / wormwheel isn't exactly 90:1 and I can't believe Nikken would make something with an odd ratio - it was originally a stepper motor driven rotary axis with the same 4:1 gearing 0.5% (approx) is 180 steps being lost if that's the cause :bugeye: ... I'm befuddled - none of this makes sense :bang: Short of pulling it apart and physically checking each ratio in the drive chain accurately I don't see a way forwards :scratch: :scratch: :scratch: (I re-did the test and it is absolutely consistent, so unlikely to be a loose coupling or something like that - I also, having run forwards 3 revs to 1080 degrees, ran back to -10, then forwards to zero and it was bang on) |
| John Stevenson:
PM or email your address aGain [ best Forrest Gump voice ] and I'll stick another 125 count Heidenhain encoder on the carrier for you. That should then take one option out of the scenario [ unless this encoder is pants as well ? ] |
| RussellT:
The worm can't be out by half a percent - the wheel would need a half tooth. If it was consistently missing one gap in the encoder disc it would be out by 0.8 percent - but could it miss one gap about 60 percent of the time. Can you try it with slower movement and see if that's the same? Russell |
| BillTodd:
does the Heidenhain encoder have a zero output? (i know some do ) Can you confirm using the zero output that you are getting 125 counts per rev ? |
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