Z axis calibration

Hi,

I am running Marlin on a Prusa i3.

I am having trouble trying to calibrate the Z axis;

The default value in Marlin for steps/mm on the Z axis is 200.0*0.8/3.

with this value, the Z axis is not moving anywhere near enough...

So I do some calibration tests, and work out that it should be approximately 4000 steps/mm

When I enter this value into marlin, and upload to RAMPS 1.4, the Z axis no longer works- Both Stepper motors 'Squeal'/ Vibrate/ dont rotate atall.....

Any Ideas whats going wrong?

Many thanks in advance.

I would just deleted the formula (200.0*0.8/3) and enter a straight number of 4000 like the X and Y. You should be able to calculate the exact number by how many steps your motor is and the pitch of your lead screw.

Try this calculator
[calculator.josefprusa.cz]

When I calculated mine it was 1.8 degree motor divided by 360 =200 steps per revolution. 200*16 (micro stepping) =3200 micro steps per revolution. 3200/ball screw pitch of 5= 640 steps per MM.

Hope I understood your question correctly

thank you for your help- I had got rid of the calculation, and was simply entering the decimal value, but the motors were just stalling etc.

I have since found this thread;

[forums.reprap.org]

Which seems to describe a similar problem to mine. Haven't had a chance to test yet, but hoping reducing the feed rate will solve the issue.

EDIT: Just tested with reduced feed rates and shes working like a dream!

Cheers

Edited 1 time(s). Last edit at 10/27/2013 03:18PM by w.harris87.