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Problem: Z-Axis doesn't work during a print. It attempts to work, maybe climbs on the Z-Axis, but screws back down. It whines, too. But, Z-Axis DOES work while not printing. It doesn't matter if the bed and nozzle heating or not, if it's not printing, it works as it should. I don't know what else I can do to troubleshoot this problem.

I have:

  • Changed the Ramps 1.4 board twice
  • Swapped drivers around, bought new drivers
  • Swapped X-Axis and Z-Axis motor connections
  • Cleaned threaded rod.
  • Leveled two Z-Axis threaded rod riders to near atomic perfection.
  • Changed firmware to each of the 3 latest updates
  • Remounted motor so both face same cardinal direction
  • Cursed
  • Changed jumper configurations from 16th microstepper to 8th for more power. No dice. Fried two drivers that way.
  • Dialed and redial and tridialed and quaddialed the driver pots
  • Recalled the Z-motors work while not printing so it isn't the driver pots
  • Cursed again
  • Scoured the web for similar issues
  • Looked for G-code that might limit Z-Axis elevation
  • Died a little. Just a little


  • RepRap Guru DIY Prusa i3 V2 3D Printer Kit
  • Ramps 1.4
  • A4988 Driver
  • Firmware:
    • Marin 1.1.8,
      • 1.1.7 (screen didn't function),
      • 1.1.6 (screen didn't function),
    • RepRapGuru_Marlin_v4,
    • RepRapGuru_Marlin_v2

Additional information:

  • My power supply is the original 12 V 360 W supply with the kit.
    • The 5 amp power in is 12.02 V, the 11 amp power port is 11.96 V and 12.18 V depending on which heater is on.
    • The bed measures 11.50 V and the hotend is 3.4 V
  • While heating the bed and hotend I am using the LCD screen and rotary encoder to move my axes. It works as expected until printing. I have upgraded to an aluminum 12/24 V hotbed from the original PCB.
  • Currently getting Repetier. Will update.
  • The z-axis leadscrew is M5-0.8 mm

1 Answer 1

I would check the gcode you're generating to make sure it's not full of "bad" z-commands.

Further, I'd take any gcode file you have and manually edit it, leaving in all the initializations, heatings, zeroing, etc., and then delete everything except some z-motion commands. Run that as a test case to see what happens.

I think it's extremely unlikely that the gantry has enough mass to force the z-screws to counter-rotate (lowering the gantry), and you'd see that with power off in any case.


As Greenonline discovered, a bad choice of lead screw might cause the behavior you're seeing. It would be a bit scary if a stock kit such as the one you bought provided high-pitch Z-screws. Better check that out!