Z axis problems when running 2 steppers

Hello
Im in the proces of building my own 3d printer, im using the arduino mega and a ramps 1.4 shield and 5 polulu drivers.
I have set the vref to 0,50 on x and y axis and both extruders, and vref on z is 0,82
My steppers are nema17 1.8A 1.8degrees.
Im currently running the marlin test software and repetier host.
When i start the arduino running with 1 stepper on extruder0, x-axis, y-axis and 2 steppers on Z-axis, the extruder,x and y axis are running fine,(toggeling between directions), but both the z axis just have some noise and dont turn.
If i try only 1 stepper on the z axis polulu it runs fine.
I have tried to change the steppers and the steppers with the same result!
I have also tried to run 1 stepper on vref 0.35 which still works fine.
Hope some of you have a solution to my problem.

Best regards Andreas

Be sure that both Z-steppers turn the same and set max Z speed in firmware to 3mm/s (180mm/min)

In Marlin if the DEFAULT_MAX_FEEDRATE for the Z axis is 5 try change it to 1 or 2

Steve

You need to increase the power to the motors.
As i understand you run with only one Stepper Drive to both your Z-motors
On the stepper you have a smal screw. Turn this clockwise to increase the power to the Motors.
Just turn it so that you cant turn the rods with your hand. The more power you give it the hotter it will get. So make sure to have cooling on your board if you need to set it to max power.

Check your wiring to each motor
is it identical shielded >20 gauge wire
does it cross over other wires or the power supply?

I have been running TWO motors (NEMA 17) on my RAMPs Z axis for years
without a problem (after I re-wired with shielded cable),
without diddling with driver setting

Quote
sap_joakim
You need to increase the power to the motors.
As i understand you run with only one Stepper Drive to both your Z-motors
On the stepper you have a smal screw. Turn this clockwise to increase the power to the Motors.
Just turn it so that you cant turn the rods with your hand. The more power you give it the hotter it will get. So make sure to have cooling on your board if you need to set it to max power.

[attachment 48125 DRV8825-Drive-Board-03-350x350.jpg]

As I'm having a problem with not enough motor-power, too, I'll just ask here:
What is the maximum power that should be used? I got some bent threaded rods which lead to the motors needing more power. I turned the potentiometer to about 3/4 (means 3o'clock), then the
motors apparently work, but the driver is getting hot pretty quickly. Wasn't sure, if that's ok or if it will die when in this state for a longer period.

I

Edited 1 time(s). Last edit at 01/30/2015 10:48AM by sap_joakim.

Quote
Ano

Quote
sap_joakim
You need to increase the power to the motors.
As i understand you run with only one Stepper Drive to both your Z-motors
On the stepper you have a smal screw. Turn this clockwise to increase the power to the Motors.
Just turn it so that you cant turn the rods with your hand. The more power you give it the hotter it will get. So make sure to have cooling on your board if you need to set it to max power.

[attachment 48125 DRV8825-Drive-Board-03-350x350.jpg]

As I'm having a problem with not enough motor-power, too, I'll just ask here:
What is the maximum power that should be used? I got some bent threaded rods which lead to the motors needing more power. I turned the potentiometer to about 3/4 (means 3o'clock), then the
motors apparently work, but the driver is getting hot pretty quickly. Wasn't sure, if that's ok or if it will die when in this state for a longer period.

I have burned 2 Steppers on my printer already do to the same problem as you have.
Now i have the power on 3/4 and with cooling flanges. No problem so far but it get so hot that if you touch it you will get burned :/
Thinking of adding a Fan to the ramp so it will cool the Stepper drivers.

If you have a spare Stepp Drive you can just max the one you have and test if it works or not without fan.
But if you wanna be on the safe side just add a Fan smiling smiley

The Steppers will get hot anyway so do freak out about it . They are made for some heat atleast tongue sticking out smiley

Also make sure to OIL THE RODS so they turn easyer. i use sewing machine oil on everything.

Edited 1 time(s). Last edit at 01/30/2015 10:49AM by sap_joakim.

Ok, I just found out, that my problem was NOT the power, but the steps settings. See: http://forums.reprap.org/read.php?151,460534