Hi: I have a VMC that had a Fanuc 6MB controller. I've converted it to Linux CNC but kept the AC Spindle servo unit and I'm having a problem.
The systems works great most of the time. The spindle works as commanded, takes speed commands, is stopped when it thinks it's stopped, does orient, etc just as it should. However, sometimes when the unit comes on it spins backwards slowly. When this happens, a speed command works but not really.
The machine reports it's come up to speed (and the command voltage is correct) but the spindle spins really slowly. For example, it I send an M3 S5000 command, it only spins a few hundred RPM but thinks it's come up to speed. When I send an S0 command, it thinks it stopped but it's still spinning slowly. Orient works just fine, holds the position as stopped but as soon as I release orient, it keeps spinning.
Sometimes it works great. Sometimes it comes up on this mode. No alarms in either case.
What do you all think? Any ideas?
It's a "Model 3" AC Spindle Servo. A06B-60AA-H007.
SOLVED - Intermittent slow reverse motion when "stopped"
Hi All;
So I solved my own problem. The wound was entirely self inflicted.
I converted my Fanuc 6MB electronics to a cool new LinuxCNC based system driven by Jon Elson @ Pico's PPMC boards, the only original electronic component I kept was the spindle controller since it has orient.
I had a problem originally, the new electronics on the PPMC DAC drove 0-10V as they should but they couldn't source enough current to drive the old transistors on the spindle controller. The thing would work great up to 4-5 Volts and then couldn't push the current needed by the Fanuc spindle controller. Took me forever to figure out.
To solve the problem, I made a little current amplifier circuit that acts as a voltage follower.
Something went wrong with that little custom board an it was outputting the wrong voltages, the spindle amp was working just as it should.
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Fanuc 6MB Spindle controller - Intermittent slow reverse motion when "stopped"
