Skip to main content
  1. Needle-nose pliers for tension check
    • Needle-nose pliers for tension check

    • 2.5mm Allen key for M3 screws

    • Slotted screwdriver for the belt insertion

    • Use the bag "MK2.5 1"

  2. Before we proceed further in the upgrade to MK2.5 it is a great time for quick maintenance. Move the bearings to side, to create a longer path for cleaning the smooth rods.
    • Before we proceed further in the upgrade to MK2.5 it is a great time for quick maintenance.

    • Move the bearings to side, to create a longer path for cleaning the smooth rods.

    • Take a cloth/towel and wipe the smooth rods. Focus on the parts next to the X-ends where most of the dust is accumulated.

    • You can also apply a little bit of general purpose machine oil on the smooth rods and move the bearings back and forth a couple of times.

    • Regular maintenance is described in the Handbook for MK2.5, see chapter 12.1

  3. For the following step, please prepare: X-carriage for MK2.5 (1x) M3nS nut (5x)
    • For the following step, please prepare:

    • X-carriage for MK2.5 (1x)

    • M3nS nut (5x)

    • Zip tie (2x)

    • Insert nuts in the traps, as in the second picture. Ensure proper alignment with Allen key.

    • Insert zip ties in the slots as shown in the last picture.

    • Note: Design of your X-carriage printed part might slightly differ, but the assembly process is the same.

  4. Take your printed X-carriage for MK2.5 and place it on the X-axis. Double check the correct orientation as in the picture!
    • Take your printed X-carriage for MK2.5 and place it on the X-axis.

    • Double check the correct orientation as in the picture!

    • Align bearings and tighten the zip ties. When ready, trim the zip ties using pliers.

  5. There is an update to the  X-carriage, the belt holding system was redesigned for better performance and endurance. The assembly manual covers both versions.
    • There is an update to the X-carriage, the belt holding system was redesigned for better performance and endurance. The assembly manual covers both versions.

    • Compare yours against the picture and choose from following:

    • The old design is on the left side of the photo. Please proceed to Step 13

    • The new design is on the right side of the photo. Please proceed to Step 6

  6. Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture.
    • Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture.

    • Use a screwdriver or the smallest Allen key to push the belt in.

    • Your design of the x-carriage might slightly differ. It does not affect the belt assembly.

  7. Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back. Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables. Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.
    • Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back.

    • Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables.

    • Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.

  8. Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end. Rotate the X-axis motor as indicated towards the frame.
    • Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end.

    • Rotate the X-axis motor as indicated towards the frame.

    • Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.

    • Use a screwdriver or the smallest Allen key to push the belt in.

    • There will be belt overhang on this side, DON'T TRIM IT yet.

  9. Using right hand rotate the motor to its original position and hold it. Using a finger on your left hand push the belt down. Some force should be needed for bending the belt, BUT don't try to overstretch the belt as you might damage the printer.
    • Using right hand rotate the motor to its original position and hold it.

    • Using a finger on your left hand push the belt down. Some force should be needed for bending the belt, BUT don't try to overstretch the belt as you might damage the printer.

    • If you are struggling to rotate the motor back into position the belt tension is too high.

    • Depending on the belt being under or overstretched, adjust the amount of the belt in the X-carriage.

    • When done, rotate the motor to its original position and tighten the M3 screws again.

  10. Both top and bottom part of the belt should be parallel (above each other).
    • Both top and bottom part of the belt should be parallel (above each other).

    • To adjust the belt position, release the screws on the pulley and move it slightly until you reach the best position.

    • Tighten both screws on the pulley.

  11. Use the technique described below to test if the belt is properly stretched.
    • Use the technique described below to test if the belt is properly stretched.

    • Use pliers to hold the X-axis motor shaft.

    • Move the X-carriage towards the X-axis motor. Don't use excessive force.

    • If the belt is stretched properly, you should feel a resistance and the X-carriage won't move at all. If the belt is too loose, it will deform (create a "wave") and jump over the teeth on the pulley.

    • Belt too loose? Return to step 8 and repeat all steps until now. You have to rotate the motor and retighten the belt in the X-carriage. Shortening the belt length by moving one or two teeth outside X-carriage should be enough.

  12. For the following step we recommend getting a white marker, but you can also trim the belt without it. Measure the part, which must be trimmed and gently take the end of the belt away, from the X-carriage, but make sure at least 3-4 teeth are still in the X-carriage, as you don't want to lose the tension. If possible make a mark, where to cut the belt. Ensure again your mark is in the correct position and the belt is still stretched.
    • For the following step we recommend getting a white marker, but you can also trim the belt without it.

    • Measure the part, which must be trimmed and gently take the end of the belt away, from the X-carriage, but make sure at least 3-4 teeth are still in the X-carriage, as you don't want to lose the tension. If possible make a mark, where to cut the belt.

    • Ensure again your mark is in the correct position and the belt is still stretched.

    • Using pliers cut the belt and push it inside X-carriage. Use screwdriver or Allen key, if needed.

    • You can cut the belt also with scissors (not included in the kit).

    • Ready? Please jump to step Step 19

  13. Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture. Press the belt all the way in, use a screwdriver or an Allen key. It's very IMPORTANT that the short end of the belt isn't sticking out of the X-carriage.
    • Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture.

    • Press the belt all the way in, use a screwdriver or an Allen key.

    • It's very IMPORTANT that the short end of the belt isn't sticking out of the X-carriage.

  14. Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back. Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables. Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.
    • Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back.

    • Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables.

    • Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.

  15. Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end. Rotate the X-axis motor down. Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.
    • Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end.

    • Rotate the X-axis motor down.

    • Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.

    • Press the belt all the way in, use a screwdriver or an Allen key.

    • There can be a slight belt overhang on this side, no need to trim it.

  16. Using right hand rotate the motor to its original position and hold it. Using a finger on your left hand push the belt down. Some force should be needed for bending the belt, BUT don't try to overstretch the belt as you might damage the printer.
    • Using right hand rotate the motor to its original position and hold it.

    • Using a finger on your left hand push the belt down. Some force should be needed for bending the belt, BUT don't try to overstretch the belt as you might damage the printer.

    • If you are struggling to rotate the motor back into position the belt tension is too high.

    • Depending on the belt being under or overstretched, adjust the amount of the belt in the X-carriage.

    • When done, rotate the motor to its original position and tighten the M3 screws again.

  17. Both top and bottom part of the belt should be parallel (above each other). To adjust the belt position, release the screws on the pulley and move it slightly until you reach the best position.
    • Both top and bottom part of the belt should be parallel (above each other).

    • To adjust the belt position, release the screws on the pulley and move it slightly until you reach the best position.

    • In case you can't make the belt parallel, check if the belt is properly inserted in the X-carriage.

    • Tighten both screws on the pulley.

  18. Use the technique described below to test if the belt is properly stretched.
    • Use the technique described below to test if the belt is properly stretched.

    • Use pliers to hold the X-axis motor shaft.

    • Move the X-carriage towards the X-axis motor. Don't use excessive force.

    • If the belt is stretched properly, you should feel a resistance and the X-carriage won't move at all. If the belt is too loose, it will deform (create a "wave") and jump over the teeth on the pulley.

    • Belt too loose? Return to step 15 and repeat all steps until now. You have to rotate the motor and retighten the belt in the X-carriage. Shortening the belt length by moving two or three teeth outside X-carriage should be enough.

  19. X-axis is done!
    • X-axis is done!

    • Did you use the new X-carriage and tighten the belt properly?

  20. Check the package and look for the spiral wraps or textile sleeves inside. There are two possibilities: There are only textile sleeves present in the kit, then proceed according to the: 4. E-axis assembly (textile sleeve)
    • Check the package and look for the spiral wraps or textile sleeves inside. There are two possibilities:

    • There are only textile sleeves present in the kit, then proceed according to the: 4. E-axis assembly (textile sleeve)

    • There is a combination of spiral wraps and textile sleeve in the kit, then proceed according to the: 4. E-axis assembly (spiral wrap)

Finish Line

111 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

222 Guides authored

Team

Prusa Research Member of Prusa Research

Community

3 Members

364 Guides authored

10 Comments

No problems whatsoever!!

Used the opportunity to clean all rods.

Theo Gerrits - Reply

This took me about 30 minutes to complete.

Jared Deckard - Reply

For me the new style serrated belt tightening slots were too tight and I could not force the belt is more than 2/3 or so. I had to use scalpel type knife to carefully cut away some material from the smooth sides of the left and right slot.

Ergo Esken - Reply

My Mk2.5 loose steps on X randomically when Travel Speed is 180 (Slic3r default), 120 is fine. Belt too loose? It seems tight.

Francisco Bischoff - Reply

Yes, you definitely want to check the belt tension, you have to be able to pluck the belt like a guitar string. Also check the pulleys alignment and correct orientation on the shaft.

Martin L. - Official Prusa CS -

Add Comment

View Statistics:

Past 24 Hours: 5

Past 7 Days: 23

Past 30 Days: 143

All Time: 15,158