On 01/15/2020 09:10 PM, Brent Loschen wrote:
In addition to the split pulleys, my "mechanical" concerns
are more along the lines of the heavy duty electrical
contactors clunking every time the fixed speed, 3 phase AC
spindle motor is called to switch back and forth;
increased heat in the motor windings due to those
reversals; and the air powered, mechanical spindle brake
snapping on and off hundreds of times. Yes it was very
tempting, and yes, I'm sure some of my concerns could be
mitigated, however I feel that this old mill (cira 1985)
just isn't the right tool for the job.
OH! I'm not sure you can do rigid tapping by plug-reversing
the motor on mains power. At our shop, where the mills run
off 480 V mains, the plug reversing is so fast you can't
even hear it. I doubt any Z axis could keep up. But, don't
worry about
the motor, it can handle this "abuse". I do rigid tapping
using a VFD and analog spindle speed control. Even with that,
I generally reverse the spindle in about 3/4 second, from
1000 RPM forward to 1000 RPM reverse. That is slow enough
for the Z axis to follow.
Jon
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