Skip to main content
  1. This guide will take you through the most common assembly issues of the MMU2S unit and help you solve it :)
  2. Symptom: Bearings don’t rotate smoothly. This may cause issues during filament loading and unloading. Possible cause: wrongly inserted shaft; damaged bearings Solution:
    • Symptom: Bearings don’t rotate smoothly. This may cause issues during filament loading and unloading.

    • Possible cause: wrongly inserted shaft; damaged bearings

    • Solution:

    • Push the shafts out by using a 2,5mm wire or enough long Allen key and remove it. Use the smaller holes marked in the second and the third picture.

    • Remove the bearings and inspect them. In case of increased friction try to lubricate them. If it doesn't help, consider replacing them.

    • Assemble this part according to Idler bearings assembly

  3. Symptom: There is more friction than expected, which means that it the IDLER is colliding with the IDLER BODY either on the left or on the right side so the clearance isn’t as expected. This may cause issues during filament loading and unloading. Possible cause: wrongly centered idler
    • Symptom: There is more friction than expected, which means that it the IDLER is colliding with the IDLER BODY either on the left or on the right side so the clearance isn’t as expected. This may cause issues during filament loading and unloading.

    • Possible cause: wrongly centered idler

    • Solution:

    • Loosen both screws.

    • Move the idler a little bit from the idler body - a gap around 1 mm is more than enough, then tighten the screws.

    • Manually check idler rotation. It must not scrub on either side.

    • Assemble this part according to Idler body assembly

  4. Symptom: Too loose  screws or they were tightened too much and part of the IDLER has cracked. This may cause issues during filament loading and unloading or loading a wrong filament. Possible cause: loose screws; over-tightened screws
    • Symptom: Too loose screws or they were tightened too much and part of the IDLER has cracked. This may cause issues during filament loading and unloading or loading a wrong filament.

    • Possible cause: loose screws; over-tightened screws

    • Solution:

    • If too loose, tighten both M3x10 screws until you reach the motor's shaft. Make sure the idler is correctly centered and there is no friction on either side between the idler-body. According to the previous step. Tighten carefully, as you might crack the printed part!!!

    • Manually check the sideways movement after tightening. There must be no clearance! If so, tighten the screws a little more and check again.

    • If cracked, glue or replace the idler.

    • Assemble this part according to Idler body assembly

  5. Symptoms: The pulleys are misaligned (not centred) or installed backwards. It means the grub screws are facing towards the motor. The grub screws weren’t tightened properly or they got loose over time. This may cause issues during filament loading and unloading. Possible cause: misaligned or loose grub screw
    • Symptoms: The pulleys are misaligned (not centred) or installed backwards. It means the grub screws are facing towards the motor. The grub screws weren’t tightened properly or they got loose over time. This may cause issues during filament loading and unloading.

    • Possible cause: misaligned or loose grub screw

    • Solution:

    • Loosen all grub screws.

    • Push the piece of filament through the pulley body as in the picture.

    • Continue in the next step...

  6. In case your filament is bent, make sure it is bent down, so the part above the pulley is straight. Adjust the position of the pulley, the teeth must be directly below the filament. Check again the proper position relative to the teeth on the pulley.
    • In case your filament is bent, make sure it is bent down, so the part above the pulley is straight.

    • Adjust the position of the pulley, the teeth must be directly below the filament.

    • Check again the proper position relative to the teeth on the pulley.

    • Make sure the grub screw is still perpendicular to the flat part of the shaft and tighten it. Use reasonable force as you might strip the screw.

    • Repeat these instructions on the 4 remaining pulleys.

    • Assemble this part according to Pulley motor assembly

  7. The chamfer facing towards the spool holder. This causes the thicker tip of the filament cannot be hidden inside the PTFE tube. Possible cause: the tubes are incorrectly inserted Solution:
    • The chamfer facing towards the spool holder. This causes the thicker tip of the filament cannot be hidden inside the PTFE tube.

    • Possible cause: the tubes are incorrectly inserted

    • Solution:

    • There are two color versions of short PTFE tubes, orange and white. The other parameters are the same.

    • Loosen four screws on the front-PTFE-holder.

    • Remove the front-PTFE-holder.

    • Pull out and insert the PTFE tubing back all the way in. The chamfered end of the tube must be facing out!!!

    • Assemble this part according to Front-PTFE-holder assembly

  8. Symptom: The tube is sliding out. The issue might occur over time where the  tube or both tubes get loose. Possible cause: larger hole diameter of the printed part; dry rods Solution:
    • Symptom: The tube is sliding out. The issue might occur over time where the tube or both tubes get loose.

    • Possible cause: larger hole diameter of the printed part; dry rods

    • Solution:

    • Apply a small amount of glue into the holes for tubes.

    • Insert and align the tubes with the plastic surface. Then wipe off the rest of the glue. The glue must not get into the tube!!!

    • Apply a small drop of the lubricant on both smooth rods. Using your finger or the towel spread the paste around the diameter of each rod. Don't apply too much of the paste, it will have the opposite effect.

    • DON'T APPLY THE LUBRICANT ON THE LEADSCREWS OR TR. NUT!

    • Assemble this part according to Selector-finda assembly

  9. Symptom: Selector isn’t moving smoothly, hitting other plastic parts. That may cause a lot of selector movement issues. Possible cause: misaligned knife; loose screws
    • Symptom: Selector isn’t moving smoothly, hitting other plastic parts. That may cause a lot of selector movement issues.

    • Possible cause: misaligned knife; loose screws

    • Solution:

    • !!! WARNING: in this step you will be manipulating with the blade. Make sure you don't cut yourself. Use pliers or gloves to protect your fingers !!!

    • Release both screws on the blade holder.

    • Remove the blade-holder.

    • Align knife with the top left corner in the groove. Or replace it if necessary.

    • Assemble this part according to Blade-holder assembly

  10. The tension screws are supposed to be flush with, or better, a little bit below the plastic. That may cause loading and unloading filament issues. Possible cause:  too loose screws;  too tight screws
    • The tension screws are supposed to be flush with, or better, a little bit below the plastic. That may cause loading and unloading filament issues.

    • Possible cause: too loose screws; too tight screws

    • Solution:

    • Tighten the screw heads slightly below the surface of the printed part.

    • Assemble this part according to Tensioning system assembly

  11. The F.I.N.D.A. might be installed too low - which would cause non-stop triggering and the filament won’t be loaded. The F.I.N.D.A. might be installed too high - which would cause no triggering at all or false triggering = changing from 1 to 0 and would load endlessly the filament. Possible cause: incorrect F.I.N.D.A. alignment (sensor is too high or too low)
    • The F.I.N.D.A. might be installed too low - which would cause non-stop triggering and the filament won’t be loaded. The F.I.N.D.A. might be installed too high - which would cause no triggering at all or false triggering = changing from 1 to 0 and would load endlessly the filament.

    • Possible cause: incorrect F.I.N.D.A. alignment (sensor is too high or too low)

    • Solution:

    • Insert any 1.75mm filament in the selector.

    • Start tightening the sensor. During tightening try moving with the filament, as soon as the tip of the sensor presses the filament, stop tightening.

    • Turn the sensor counter-clockwise 90° to lift it up slightly.

    • Tighten the M3x10 screw.

    • Assemble this part according to F.I.N.D.A. sensor assembly

  12. Symptom: Overtightening these four screws might squeeze the PTFE tubes. This may cause issues during filament loading and unloading.
    • Symptom: Overtightening these four screws might squeeze the PTFE tubes. This may cause issues during filament loading and unloading.

    • Possible cause: too tightened screws

    • Solution:

    • Slightly loosen the screws. PTFE tubes must not fall out of the holder.

    • Assemble this part according to PTFE tubes assembly

  13. Symptom: The M2x8 screw may not fit properly in the bottom hole when the cover is installed. Possible cause: The screw isn't tightened to the end. Solution:
    • Symptom: The M2x8 screw may not fit properly in the bottom hole when the cover is installed.

    • Possible cause: The screw isn't tightened to the end.

    • Solution:

    • Make sure the screw hole is not obstructed.

    • At the beginning of tightening, slightly push the screw down by Allen key until you feel that the screw is trapped in the bottom hole. The screw must be perpendicular!

    • Tighten the screw to the end.

    • Assemble this part according to IR-sensor assembly

Finish Line

9 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

232 Guides authored

Team

Prusa Research Member of Prusa Research

Community

3 Members

374 Guides authored

0 Comments

Add Comment

View Statistics:

Past 24 Hours: 17

Past 7 Days: 159

Past 30 Days: 1,085

All Time: 4,411