Dual Z Steppers - ZA moves, ZB Twitches.

wmmc01

All the steppers work fine - I confirmed this by attaching to other ports. The only port that has issues is ZB. Any stepper connected to ZB only twitches when I actuate Z motion, ZA works fine.

dc42

ZA and ZB are wires in series, so motors connected to them should get exactly the same current. Perhaps there is a short between two pins of the ZB connector? I suggest you check whether there is a solder bridge on the underside of the board. Also check for a short between the pins using a multimeter if you have one.

wmmc01

@dc42 - Makes sense. Thanks for your suggestion, I'll take a look and check for shorts when I can get back to this Friday. Thanks!

wmmc01

@dc42 How do I check for shorts with a multimeter? Sorry for the dumb question.

dc42

With no stepper motors connected, measure the resistance between pins 1 and 2 of the ZB connector, and also between pins 3 and 4.

wmmc01

OK, ZB has solder bridging L1 and 1A. Assuming that is not supposed to be there?! !! DO I just clip it, or hit it with a soldering iron?

dc42

That explains the problem! I suggest you remove it with a soldering iron, if you have a suitable one.

wmmc01

Thanks for pointing me in the right direction! Still getting different behavior with Z (both) making plenty of noise, but only moves in spurts. X&Y seem normal. Are my settings messed up?

; Drives
M569 P0 S1 ; Drive 0 goes forwards
M569 P1 S1 ; Drive 1 goes forwards
M569 P2 S1 ; Drive 2 goes forwards
M569 P3 S1 ; Drive 3 goes forwards
M350 X32 Y32 Z32 E32 I0 ; Configure microstepping without interpolation
M92 X160 Y160 Z3200 E476.5 ; Set steps per mm
M566 X900 Y900 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
M203 X12000 Y12000 Z6000 E1200 ; Set maximum speeds (mm/min)
M201 X500 Y500 Z250 E250 ; Set accelerations (mm/s^2)
M906 X800 Y800 Z800 E800 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

dc42

As your Z steps/mm is very high (3200), you should reduce your Z acceleration in M201 (try 50) and Z max speed in M203 (try 300).

wmmc01

I think I miscalcualted the Z steps by missing a point in this guide: https://betrue3d.dk/duet-wifi-generating-firmware-using-configurator/
I redid the calc to 800 steps/mm and they run fine now.

Thanks so much for your prompt attention! Great forum!