Z steppers interfering with each other.

So my Z steppers have started interfering with each other. At first I thought they were slipping but upon further inspection I noticed that one will stop moving altogether. It almost seems as if they are getting feedback from each other when moving at faster speeds and sometimes randomly at slower speeds. I've tried wiring them in parallel and in series. When in series one stepper will just sit there and spaz. If you spin it with your fingers it'll go in that direction but then the other one will stop moving.


Any ideas?

Thanks.

Have you tried adjusting the pot on the driver? Up the reference voltage a bit. If it's been sitting in the same spot for a while they can build up a litte resistance.

I've tried that and I've tried swapping the driver out for another as well.

Some more information that I forgot to include:
Z steps = 3023.62
1/16 steps with a pololu clone driver
I'm basically using this mod: [www.thingiverse.com]

To test it I'm running this GCode which is the starting code for anything Cura generates:
;Sliced at: Sat 12-04-2014 11:26:53
;Basic settings: Layer height: 0.3 Walls: 0.8 Fill: 30
;Print time: #P_TIME#
;Filament used: #F_AMNT#m #F_WGHT#g
;Filament cost: #F_COST#
;M190 S70 ;Uncomment to add your own bed temperature line
;M109 S200 ;Uncomment to add your own temperature line
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z15.0 F5000 ;move the platform down 15mm
G1 F9000


I have my Z Max acceleration set to 5. I've noticed that if I set it to 3 it doesn't have any issues.

Edited 1 time(s). Last edit at 04/12/2014 05:14PM by jaeg.

A couple of things...

1) Check to make sure there is no binding with the printed parts- be sure there is minimal extra resistance besides the nuts on the x-axis.
2) Check for broken/damaged wires and shotty soldering. Very bent wire? Loose pin in the connector?
3)Switch the wire connections, does it matter which motor is plugged in where?
4)What hardware are you using? If you are using a ramps board or something, check for testing firmware. It simply makes the motors move back and forth and cuts out many of the variables that printing software will give you.
5) Try a known working different stepper driver if you are using them.

Have you checked the resistance on the connectors? Are they consistent?

Edited 1 time(s). Last edit at 04/13/2014 05:25AM by Istale.

1) All seems to be ok.
2) The connections seem to be pretty solid.
3) Individually the motors work fine. But when connected together they seem to fight each other at higher speeds.
4) I'm using Ramps 1.4 running Marlin. I'll look around for some testing firmware.
5) I've swapped the drivers out with 2 known working ones.


I think the steppers I have are just really electronically noisy. When in parallel when I move one by hand the other will move too. (which may be normal behavior since the motors would generate an electrical current when moved by hand)

What are the torque requirements for a Prusa i2? I'm curious if the Z steppers aren't torquey enough.

I bought my steppers in a lot of 5.

The sticker says:
16v 1.2A
1.8 degrees / Step
Japan Servo
Kh42jm2b140c

It's a Unipolar stepper

Edited 1 time(s). Last edit at 04/14/2014 10:07PM by jaeg.

"16v steppers" - I think high voltage steppers perform poorly with reprap electronics.

Unipolar steppers are fine, just don't wire up the connection to the central tap (I have one working like this)

You really want low voltage steppers. 16v steppers won't achieve their full potential on a 12v supply.

From reprap wiki:
"Power and current
All recent stepper controllers use a current-limiting design. Because of this, the resistance (ohms, Ω) of the coils doesn't matter, as long as it is low enough for the current to rise fast enough for the current-limiting design to come into play. If the resistance is too high (i.e. 24 V steppers) the current simply doesn't raise enough. For this reason, stepper motors rated for 3-5 V and 1-1.5 A are generally recommended, as these motors will perform near their peak torque with a current-limiting stepper controller (such as a Pololu A4988)."

You can probably get away with 16v steppers on your other axes - but running two on Z will have issues.

Doh! That makes perfect sense and possibly explains my issues with my extruder motor having to have it's retraction speed cranked down really low.


Thanks!