On Thu, 06 Oct 2005 15:55:13 -0700, Eric R Snow
wrote:

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

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 **** out of you
for torturing the cat." Gunner