Motor skipping steps

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Sometimes a motor can "skip" steps, making one layer shifted with respect to the previous one. There are a number of reasons why this can happen, and it can be due to a mechanical malfunctioning/miscalibration, or electronic.

[edit] Mechanical problems

  • The filament is not turning freely
  • Belt tensions might be too loose, too tight, or different between right and left belt
    • If it is the Y axis belt, first check the printed front corner idler pulley bracket, if it cracks or pulls off the screw over time, the belt will seem too loose and the motor will skip steps, but tightening the belt in the usual way will put more tension on it, cracking it further and making the bracket weaker
    • Adjust the belt tension by using a hex key on the bolts that attach the belts to the carriages. The belt must be tight, but the carriages should be easily movable by hand when the machine is off
  • Inadequate lubrication
    • Add lithium grease to the rods
  • Set screws on the pulley collars can be loose
  • The nozzle is bumping on prints as it traverses the bed. This might be caused by the prints curling.
    • Add a "z-lift" height of 1 mm in Repetier-Host (Slic3r options) to see if this helps.
    • Use an extruder fan to prevent overhangs and other features from curling upward.

[edit] Problems in the electronics

  • The stepper drivers can be too hot
    • Attach a fan to the electronics in the back of the printer
  • Trimpots are miscalibrated
    • See the official solidoodle page.
      • Be aware that attaching a different computer to the printer can cause the voltages to vary. Always calibrate the trimpots with the machine and the computer on and attached.
      • Fluctuations on the USB voltages can cause random skips even when the trimpots are correctly adjusted. In this case, it is possible to cut the 5V USB line as described here: http://forums.reprap.org/read.php?158,109719,123850#msg-123850
  • Power Supply (12V) failure: dropouts in the power supply will definitely cause X and Y shifts.
    • Check 12V power supply connections on the electronics board
    • Test the 12V output of the power brick, and see if it is intermittent with movement or vibration.
      • Advanced users may be able to resolder loose joints in the power brick, but use extreme caution and unplug the supply from all outlets before attempting.
    • If needed, replace the power supply brick.
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