Z Motors not moving

dc42

If the two Z motors are connected to the Za and Zb connectors but they are not moving in sync, that suggests to me that the Z axis is binding, or you have set the Z acceleration or speed too high, or the Z motor current is set too low.

sfinlon

@dc42 it might be the current set too low, I took the lead screws out of the spider couplers to just let them free spin.

They dont seem have much torque. If I just touch my finger to it, it almost immediately stops spinning.

dc42

What motors are they?

sfinlon

@dc42 stock anet a8 motors.
I did just order 2 new nema17’s and new couplers because I can’t tell what part is failing.

dc42

@sfinlon said in Z Motors not moving:

@dc42 stock anet a8 motors.
I did just order 2 new nema17’s and new couplers because I can’t tell what part is failing.

Perhaps they are high-inductance motors that need to be connected in parallel instead of in series.

wilriker

@sfinlon I can see two errors in your config (having just converted my own Anet A8 to Duet I made the same mistakes):

For one Z Motor direction needs to be reversed so change
M569 P2 S1 ; Drive 2 goes forwards
to
M569 P2 S0 ; Drive 2 goes backwards

and (assuming you have not changed the lead screws) also your steps/mm for Z axis are wrong. Change
M92 X80 Y80 Z4000 E420 ; Set steps per mm
to
M92 X80 Y80 Z400 E420 ; Set steps per mm

If you are still using the original 16-tooth pulley also the values for X and Y need to be 100 instead of 80. And using the original extruder gear these steps would be 95 instead of 420.

I had my steps/mm for Z calculated wrong (should have trusted Marlin config more) and had set it to 1600 which led to horrible asymmetric jumping of the Z axis. I am glad that it did not break or bend anything (at least I hope it did not).

P.S.: Here is my complete section of drive settings for all motors, rods and leadscrews being stock. Note that motor currents are currently set to their rated current. I will tune this probably tonight to a lower value.

; Drives
M569 P0 S1                                         ; Drive X goes forwards
M569 P1 S1                                         ; Drive Y goes forwards
M569 P2 S0                                         ; Drive Z goes backwards
M569 P3 S1                                         ; Drive E0 goes forwards
M350 X16 Y16 Z16 E16 I1                            ; Configure microstepping with interpolation
M92 X100 Y100 Z400 E95                             ; Set steps per mm
M566 X600 Y600 Z18 E300                            ; Set maximum instantaneous speed changes (mm/min)
M203 X24000 Y24000 Z480 E3000                      ; Set maximum speeds (mm/min)
M201 X2000 Y2000 Z100 E10000                       ; Set accelerations (mm/s^2)
M906 X900 Y900 Z900 E900 I20                       ; Set motor currents (mA) and motor idle factor in per cent
M84 S30                                            ; Set idle timeout

One last addition: if you are also still using stock thermistors you could use the following settings:

M305 P0 T100000 B4725 C7.060000e-8 R4700           ; Set thermistor + ADC parameters for heater 0
M305 P1 T100000 B4725 C7.060000e-8 R4700           ; Set thermistor + ADC parameters for heater 1

sfinlon

@dc42 "Perhaps they are high-inductance motors that need to be connected in parallel instead of in series."

That's exactly what I was thought too! Because if I left the jumpers on Z2 and only plugged one or the other motor in to Z1 that one motor was fine.

So I cut the wire, and spliced and soldered them together in parallel, and plugged the combined connector in to Z1 and left the jumpers on Z2 and it's working fantastically now.

sfinlon

@wilriker I know marlin had the steps per mm at 100 100 400 for x y z but wasn’t sure if the steppers changed any of that.

I modified the thermistors like you exampled though.

What do you use for a bed offset? It looks like I’m not quite centered.

wilriker

@sfinlon I have my minima for X -35mm and Y -7mm. Might be slightly different on your machine but generally should be quite close.

Except for my mistake with Z direction and steps/mm I basically started with the settings from Marlin and they are working.

As I said, I would tune my motor currents and can already say that 50% (=450mA) for X, Y and Z (which by the way is regularly wired in series in my setup) work fine for print speed of 75mm/s and travel speed of 120mm/s. I only tested this in a dry-run yet, though.
By dry-run I mean I took the GCODE of one of my prints that I knew contained parts of all kinds (long slow and fast extrusions, long travels, diagonals, circles, zig-zag infill with fast direction changes, etc) and reduced it to two selected layers Andrew removed heating and all extrusions. Then I set my motor currents and "printed" this file and checked that there are no skipped steps. I have not yet fine-tuned extruder motor but at it to around 750mA for now.

P.S.: if anyone is interested in my dry-run file, I am happy to she l share it.

Phaedrux

@wilriker A dry-run file is a good idea. I'd be interested in seeing it.

wilriker

@phaedrux Here you go with my dry-run file Testmoves.gcode.

I used https://www.thingiverse.com/thing:2895187 as a basis, sliced it with 0.2mm layer height (all the settings are appended by Cura at the end of the file anyway) and removed all layers except 11 and 16. After that I removed all Ennn parts of movements and also cleaned up start code to not heat up anything. It only does a G28 at the beginning and a M18 at the end.

This has some pretty gnarly paths with fast zig-zag infill that are going to shake your printer - also a good way to find loose screws or other rattling things.

EDIT: Your printer needs at least to be able to reach X175 Y175 to be able to use this - even though this has not to be a printable area as no extrusions happen.