Check the tension of the Ultimaker 3 short belts

Maintaining correct tension on the short belts is important to ensure good print quality. The short belts transfer the movements of the X and Y motors to the print head. If the belts are too loose, print head movement may not be accurate, which can cause print inaccuracies. Over time, the belts may become slack.

It is recommended to check the tension of the short belts at least once every three months or when you notice inaccuracies in your prints.

Checking instructions

Caution: Turn off the printer or ensure the Ultimaker 3 cannot accept new print jobs through the Digital Factory.

Pluck the two short belts to check their tension. They should resonate, like guitar strings. It should not be possible to press the belt against itself. Furthermore, the tension of the two belts should be equal.

Correct-belt-tension.jpeg Loose-belt-tension.jpeg
Correct belt tension

Belt too loose


Tightening the short belts

To restore the tension, perform the following steps. Use the 2 mm hex screwdriver from the Ultimaker 3 accessory box.

  1. Loosen the Y motor by using the hex screwdriver to loosen the four bolts that hold the Y motor to the left panel. Do not remove the bolts. The motor should be able to slide up and down.
  2. Firmly press down on the motor with one hand. This ensures maximum tension on the short belt.
  3. While still pressing the motor down, tighten the four bolts of the Y motor in a cross pattern. First tighten the top-left bolt, then the bottom-right, followed by the bottom-left and ending with the top-right. This ensures that the motor is attached straight.
  4. Perform the above steps for the X motor that is attached to the back panel. Afterwards, check the tension of both belts again.
02_Push-down-Y-motor-optimized.jpg 01_Loosen-bolts-Y-motor-optimized.jpg
Firmly push down on the motor Tighten the motor bolts in the frame
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