Another 7i76 Spindle Setup Question

Chaps,

I've used PnCConf to configure a 5i25/7i76 setup for a lathe on Version 2.5.5 of Linuxcnc. It's all gone well, so a big thanks to Mesa and those who develop/support Linuxcnc.

I have configured the spindle drive using the TB4 spindle output to control a ABB VFD, and the TB3 encoder input to read a spindle encoder. Reading a few other posts, I've managed to get spindle enable, direction, and speed sort of working, and would be thankful if someone could run a critical eye over the following settings, and let me know where I've messed it up. Note that the maximum rpm of the spindle motor is currently set at 1465rpm, and the encoder is quadrature 1024ppr.

Cheers, Steve.

Well, nothing desperately wrong, just little buggy things. When operating with the Manual Control (F3), I can get full spindle speed at 100%, but spindle speed drops to 0rpm when the Spindle Override slider is at 28%. (This could be a separate VFD issue.) When running the spindle in reverse in Manual Control, the + button slows the spindle down, and the - button speeds it up. And I did have the S Axis Test feature working, but now it has stopped.

So, I assume I've messed something up.

Cheers, Steve

PS. The spindle count now increments by a value of 1 every revolution of the spindle, I'm guessing that's what it is expected to do?

Had another fiddle today, and the spindle speed control problem is definitely the ABB VFD. The MESA card outputs a nice linear 0 to 10 VDC over the 0 to 100% range. The issue is a parameter in the VFD, which prevents the motor turning until the analogue control signal is 20% of the full 10 VDC range (2VDC). The manual notes that they do this as in some configurations, a loss of the analogue signal, or a 0 VDC signal, could cause the drive to go into reverse . (How this could happens when the Mesa card controls the spindle direction is beyond me - the manual must be referring to another configuration.) This parameter can be changed, so I will have another fiddle tomorrow.

I'm still not sure I've got the Output Info limit and scale values in the spindle motor configuration correct. I've tried a few combinations of: -10, 10, 1450, 0, 10, 1450, and eventually returned to -1450, 1450, 1450, as it seems to work best.

Cheers, Steve

OK, reducing the minimum analogue control signal parameter in the ABB VFD from 20% to 0% has rectified the spindle speed range problem. With manual, Midi, or a program control, the range from 0 to a maximum 1450 rpm is linear over the 0 to 10 volts output from the Mesa card.

However, I still have a weird problem when running the spindle in reverse. It's as if the 0 to 10 volts output from the Mesa card is linear, but reversed. You call for slow speed, and you get fast, you call for high, and you get slow. Checking the voltage output from TB4 SP OUT (wiper) while using Midi control gives the following result.

M3 (forward rotation) S500 - 3.4v and 480rpm, S1000 - 6.8v and 1020rpm. Speed control. All good here.
M4 (reverse rotation) S500 - 6.5v and 1000rpm, S1000 - 3.1v and 440rpm. Speed control, but reversed.

The above results were with the spindle motor configuration Output Info limit and scale values set at -1450, 1450, 1450. Trying a number of different values has not helped.

Any observations or suggestions on my problem would be gratefully received.

Cheers, Steve

The 7I76's analog out circuits is unipolar so you need to drive it from the absolute spindle speed pin (always positive)

Thanks guys, I now get the core concept of using an absolute value to ensure a positive signal.



I've dived into the danger zone HAL file and had a crack at: tacking -abs onto the end of some spindle motion signals; and/or adding completely new lines in the spindle control signals section based on what I've read in similar posts. The results were as expected - spectacularly unsuccessful, varying from no effect, to crashing the program on start-up with a "motion.spindle-speed-out-rps-abs pin does not exist" error. (I did read in the basic HAL manual, that, "If the signal does not exist net creates the new signal", so this adds to the confusion.)

The below text is the spindle section from the original HAL file before I started editing it. I am going to keep fiddling with it, but if anyone could point out the bleeding obvious to me it would be greatly appreciated.

Time for a quad-shot espresso,

Steve

# SPINDLE S
#*******************

# ---digital potentionmeter output signals/setup---

setp hm2_5i25.0.7i76.0.0.spinout-minlim [SPINDLE_9]OUTPUT_MIN_LIMIT
setp hm2_5i25.0.7i76.0.0.spinout-maxlim [SPINDLE_9]OUTPUT_MAX_LIMIT
setp hm2_5i25.0.7i76.0.0.spinout-scalemax [SPINDLE_9]OUTPUT_SCALE

net spindle-vel-cmd => hm2_5i25.0.7i76.0.0.spinout
net machine-is-enabled => hm2_5i25.0.7i76.0.0.spinena
net spindle-ccw => hm2_5i25.0.7i76.0.0.spindir

# ---Encoder feedback signals/setup---

setp hm2_5i25.0.encoder.00.counter-mode 0
setp hm2_5i25.0.encoder.00.filter 1
setp hm2_5i25.0.encoder.00.index-invert 0
setp hm2_5i25.0.encoder.00.index-mask 0
setp hm2_5i25.0.encoder.00.index-mask-invert 0
setp hm2_5i25.0.encoder.00.scale [SPINDLE_9]ENCODER_SCALE

net spindle-revs <= hm2_5i25.0.encoder.00.position
net spindle-vel-fb <= hm2_5i25.0.encoder.00.velocity
net spindle-index-enable <=> hm2_5i25.0.encoder.00.index-enable

# ---setup spindle control signals---

net spindle-vel-cmd-rps <= motion.spindle-speed-out-rps
net spindle-vel-cmd <= motion.spindle-speed-out
net spindle-on <= motion.spindle-on
net spindle-cw <= motion.spindle-forward
net spindle-ccw <= motion.spindle-reverse
net spindle-brake <= motion.spindle-brake
net spindle-revs => motion.spindle-revs
net spindle-at-speed => motion.spindle-at-speed
net spindle-vel-fb => motion.spindle-speed-in
net spindle-index-enable <=> motion.spindle-index-enable

# ---Setup spindle at speed signals---

sets spindle-at-speed true