Inconsistent Z axis movement

Hello,

I've built Prusa i3 rework printer. X and Y axis are working fine, but I have some issues with Z axial movement being inconsistent.
Printer is running on RAMPS 1.4 with A4988 stepsticks. I have uploaded Marlin software to the printer's arduino mega. I am controlling the printer with Repetier-host v1.5.6.

Below are the issues which I am currently facing with the Z axis. Motor cables are soldered together, and connected to a 4-pin socket in the RAMPS board. I have disconnected the motors from the threaded rods, so that I can see better how the motors are trying to move.

• The motors are rotating, but every few steps they are moving into wrong direction. So the rotation is more like back and forth movement, with very little progress in positioning the shaft.
• It looks like the motors are skipping steps.
• Motors seem to be powered when not moving. Is this normal?
• After a while the stepstick gets very hot. Is this normal?
  
  • I have posted the axis movement settings below. I have tried to change the acceleration and feed rates, but the issue remains. Do you think that above issues are software or hardware issues?
• After completing entered movement command, the motors remain in a state which sounds like they are between steps, but don't have necessary power to complete it. I disconnected the other motor, and tried running single Z axis motor, which seemed to dramatically to decrease this issue.
  
  • Would diodes soldered into each motor's cabling solve this issue?

• Here are the feed settings I'm currently using. If any other settings are relevant to this case, please let me know and I will post them.
  
  

  #define DEFAULT_AXIS_STEPS_PER_UNIT {100,100,4000,1000} // default steps per unit for Ultimaker

  #define DEFAULT_MAX_FEEDRATE {100, 100, 2, 25} // (mm/sec)

  #define DEFAULT_MAX_ACCELERATION {100,100,10,1000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for Skeinforge 40+, for older versions raise them a lot.

Thank you for your support in advance. I'm looking forward to your replies.

Br,
Quathlor

Hot drivers are a sign of overvoltage. Turn them down! Overheating drivers also cause motors to loose steps.

Thanks for your input. I'll try turning the voltage down and report back with the results.

EDIT:

• I lowered the output voltage on the stepstick to 400mV so that while driving with only 1 z axis motor, the phase get's it's maximum amps which is 1A.
  
  • The motor is now doing a single step, and then it's not rotating anymore until I disconnect the power and put it back on again.
• I took out the Z axis stepstick and tried it on the X axis. The Z axis stepstick is working there perfectly.

Is it possible that I've fried my RAMPS board? I have never disconnected any motors while the board is powered.
Any help here is greatly appreciated.


EDIT 2: I sourced the problem to be in the wirings. I re-did the z motor connection which is coming to RAMPS board, and now Z axis is working perfectly!

Edited 2 time(s). Last edit at 10/23/2015 08:04AM by Quathlor.