I thought I was about done with my R2E3 retrofit project.
But, doing some testing, I found it was losing a little bit
of position when moving. Every axis shows this, but it is
worst on the Y axis. I have a program that moves Y 3" back
and then returns to the indicator. It seems like at 12IPM or
below, it doesn't seem to lose position, but above that
speed it loses from a half to a full thousandth on each
repeat. I've looked at the A and B quadrature signals with a
scope, and they look good, the differential complements look
like complements. I am using my PPMC boards, and I've never
seen this on my older Bridgeport using the same hardware.
This retrofit is using AMC 30A20AC analog servo amps, and
the original motors. I reterminated the original Bridgeport
encoder cables to the PPMC encoder board, and have checked
all that wiring. The cables are individually shielded
twisted pairs until the last couple inches at the controller
end.
Anybody have any suggestions? I'm strongly considering
replacing all the encoders, there are some nice ones on eBay
<http://www.ebay.com/>right now, but I would have to make
shaft and mounting adapters.
The encoders are DataMetrics S-9481A-250.
Thanks for any comments,
Jon
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