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Encoder sand belt creep

Looking at a link provided here about steel belts for driving the encoder shaft eventually led me to look a several web sites of companies that produce stainless steel belts, or drive bands. It seems that all the applications where a timing element, such as a toothed pulley, are not used, belt creep occurs. This happens because the belt is only moving at the same speed as the pulley for a small part of rotation. On one side of the pulley the belt is stretched. On the other it's compressed. A miniscule amount. But .0001" is also miniscule. This is probably where the "backlash" comes from that I'm seeing. Or, maybe belt creep and belt stretch. If I can get a little free time I can find out what is really going on. I'll keep the group posted. Eric

Reply to
Eric R Snow
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Reply to
Eric R Snow

Hey Eric,

There's another new one on me. What the heck is a "sand belt" ?

Brian Lawson, Bothwell, Ontario.

Reply to
Brian Lawson

Virtually ALL machine tool spindle encoders use rubber type timing belts, including C axis lathes. The OmniTurn cnc Lathe uses a .30 width rubber belt with "steps" about .08 apart between teeth.

This allows threading into a feature. The spindle repeatability on the C axis spindle positioning is .04 degree. with its larger ladder type spindle drive belt.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Reply to
Gunner

The sand belt is of course that part of town that lies along a sandy beach or the edge of the Mojave. In some places that would be the rock belt or cliff belt. Sorry about that. A sand belt is what you use in a belt sander. Oh wait. That's not it either. I know. It's a typo. The subject should have read "Encoders and belt creep". But you knew that. Eric

Reply to
Eric R Snow

Are you saying that you do NOT have toothed pulleys? How hard would it be to cut teeth?

Bob BTW - why isn't is "pullies"?

Reply to
Bob Engelhardt

...

Do they use toothed pulleys? Bob

Reply to
Bob Engelhardt

Belt creep doesn't produce backlash but rather repeatibility errors. Due to belt creep, there needs to be some indexing mecahnism to the transmission medium so that the mechanism doesn't creep. You can do a smooth belt if you repeatedly go back to a "start" calibration position more often than the expected creep ould produce but if you're running something like a mill or lathe, that really isn't practible, especially if the machine isn't motor driven and able to slew to the reset position.

-- Why do penguins walk so far to get to their nesting grounds?

Reply to
Bob May

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