On 08/01/2020 11:10 AM, Matthew Herd wrote:
I'm still having issues with the rigid tapping. It works sometimes and
fails other times. After scoping the motion.spindle-revs, it appears to be
consistent with what we would expect aside from one possible issue. The
spindle revs reset to zero upon G33.1 being called, then count up until
they stop, reverse, go negative past zero, then return to clockwise
motion. However, on the second zero crossing (going positive) the revs go
positive, only to be reset to zero momentarily thereafter. I'm not sure if
this is normal behavior or not.
I'm not exactly sure what you are describing here. Most of
it sounds normal, but I am not aware of a second cycle of
the index sync function at the end of the G33.1 If you
have a Halscope picture, that could be interesting to look at.
However, what isn't normal behavior is that the ppmc.0.encoder.03.index
value is loaded with noise. Not occasional noise, but constantly
triggering in irregular intervals regardless of whether the spindle is
turning. I'm baffled as to how this could be so noisy and was wondering
where you might look next. Grounds look fine aside from the fact that the
control cabinet and the power cabinet have a ground wire connecting them in
addition to being grounded through the machine. When removed from the USC
board, the index can be measured with a multimeter as the spindle is
rotated. I forgot to bring my scope to the shop today (I didn't think I'd
need it) so I can't scope anything until tomorrow. Is it possible there's
a pull-up resistor missing?
Well, the index is not actually used except once for each
G33.1 operation, to start the spindle synch motion. So, it
is only important for multiple-pass threading.
But, note that while the A and B transitions are filtered by
requiring a valid quadrature state transition, the index
pulse is not. Even a 10 ns wide dip from +5 to near ground
will trigger the index logic.
What is the resting voltage of the index signal? Does it
need a pull-up resistor to +5 V? The logic threshold is 2.5
V. The USC does NOT provide any pull-up resistor. If your
encoders need such, consult the encoder data sheet to
determine what resistor value is best.
Jon
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