Z-Axis going 'negative'

On seemingly great prints the z-axis will just go 'haywire' and go negative. By that I mean the Z-axis endstop switch will engage but the axis won't stop and the motor keeps going until the metal strip on the endstop switch is completely flat.

In fact to goes so low that it will scrap the blue tape off the print bed.

During calibration the endstop switch works flawlessly so I don't believe its the switch.

Anyone run into this before?

 

Sounds like a g-code error. I was having an issue where after the first layer it would send a y=-1.2 and would zero out and drag filament.

Running the stl through netfabb repair fixed the issue generally. One time I had to change the gcode manually to .5 to get it to print properly.

If it goes negative without being told to your connection might be inversed.

 

I just got that problem also
I am having a problem with my z axis it was always working fine. Then one ny next print i did auto home like i

normally do it did that little bounce and set itself correctly.
I waited for everything to heat up the when the temp was right and the gcodes kicked in (checking the g28)
x and y was good but the z did not do the bounce instead it continues to go negative squishing the z endstop till it

can go no more then it tries to print. scrapping the glass.

I have swapped out the step drivers same issue i also swapped out the endstop. I also tried resetting. i was using cura and i also tried with pronterface. i am am using ramp 1.4 with marlin and stepsticks.
It works fine if i just hit auto home on my lcd. it's when it starts to print the second autohome it messes it up on the z knocking off the nuts on the z threaded rods. any ideas?

Did you figure it out yet?

 

what direction is your end stop facing

 

Hi! How do you resolve this problem? In my case the problem of extruder going to Z negatives comes during the print, my printer is a Rostock. I hope you have a solution for this problem and please post it here.
Thanks!