Z-axis homing stutter (solved)

Hey guys, just finished my first prusa mendel v2 earlier this week, midway through calibrations now.

Not sure if this is the correct place to ask for advice but here goes. I can't home my Z-axis reliably. I can move it up and down in 0.1-10mm increments fine (motion is smooth and no jitters/snags etc) But when i home the axis, one end will hit the endstop and stop, while the other end will try to move forwards a few mm. It does this on the double tap motion on the endstop. Both motors also emit a grinding sound, and i can see the leadscrews vibrate as though they are struggling to rotate (or the left motor, endstop side, grinds, while the other motor rotates down, resulting in a slanted x-carriage)

Attached my firmware values below.I have tried tweaking the z-home rate (which practically breaks the whole axis) and the acceleration with no improvements.

Have no idea if its a hardware or software issue. Trying to fix only this issue for 2 nights now, and i ended up dreaming about it last night too.


Am running RepetierHost and Repetierfirmware on Ramps1.4.

PS: a random travel line appears to the right in the 3d 'space' of rep-host when i move any axis, not sure if its related to my z issues

Edited 1 time(s). Last edit at 02/21/2013 03:21AM by Luftw4ffles.

slow down homing feedrate, and or increase motor current.

Tried that last night, tried again. Reducing homing feedrate makes it stutter and grind without rotating. Increased current with feedrate and it makes it better (somewhat) but still sounds like theres sand in the motors.

All in all, it homes slower and slants my carriage while making an awful racket

I had a similar problem with my machine when I was running 2 motors from one driver, I couldn't move more than 1-2mm/s without problems.

So try reducing federate to 1mm/s and see what happens. Another option is to drive the second motor from the RAMPS 5 driver if you have a driver installed, I did it this way in the end and can now do 40mm/s and never had a problem since.

Hope that helps

do you have wires hooked up the same way on each motor such as red to red, black to black , green to green, blue to blue, and are you sure motors are wired up properly. try changing wires 2 and 3 around. see if this fixes it.

A B A B
1 2 3 4

if it does not then your z axis stepper driver may be fried, or you are way way to high step speed still. can you switch the stepper driver as well?

your z axis homing feed rate in your pictures is insane 30mm/s try 3mm/s. about 180mm/m is reasonable.

Edited 1 time(s). Last edit at 02/21/2013 02:59AM by jamesdanielv.

@james: Reset my settings to default and started again. Shoved 3mm/s in homing feedrate. Works fine now

How embarrassing...i tried low values (5-10mm/s) before and it just made things worse...

Appreciate yours and everyone elses help in here. Many thanks.

Edit: I went back and tried to replicate the problem. Noticed that homing_feedrate values effect the endstop retract/double tap speed and not the speed when homing towards endstop?

Edited 1 time(s). Last edit at 02/21/2013 03:30AM by Luftw4ffles.

It should also affect the speed on the travel to the endstops.