Skip to main content
  1. For the following steps, please prepare:
    • For the following steps, please prepare:

    • Adapter-printer-mmu2s

    • The package should include only the orange adapter. If you have printed parts yourself, please don't use the version with the hole for steel ball.

  2. Insert the adapter inclined, first to the motor side.
    • Insert the adapter inclined, first to the motor side.

    • Push it down and check its upper surface is aligned with the extruder.

    • DON'T use any screw to secure the Adapter-printer-mmu2. It should hold inside the Extruder-body by itself.

  3. For the following steps, please prepare:
    • For the following steps, please prepare:

    • M3x18 screw (1x)

    • M3x10 screw (1x)

    • M3n nut (1x)

    • FS-cover-mmu2s (1x)

    • IR-sensor-holder-mmu2s (1x)

    • IR-sensor-cover-mmu2s (1x)

    • The list continues in the next step...

  4. For the following steps, please prepare:
    • For the following steps, please prepare:

    • Prusa IR-sensor (1x)

    • M2x8 screw (1x)

    • BE CAREFUL with the filament sensor, do not touch the black PCB nor the chips on it. Hold the PCB from sides.

    • Following assembly should be done close to the extruder, no need to pull the IR-sensor cable out. However, for a better visibility of this guide, some parts of the assembly were done separately from the printer.

    • MK3S/MK2.5S and MMU2S share the same new generation of the IR-sensor, just in a different position inside the extruder.

  5. First, pull the IR-sensor cable up, so you have a slack for the assembly of the printed parts. At the same time watch the other end of the textile sleeve, if you pull the cable too much, the connector will disappear in the sleeve ;) Take the smaller connector WITHOUT THE SENSOR! and carefully push it all the way through the IR-sensor-holder-mmu2s.
    • First, pull the IR-sensor cable up, so you have a slack for the assembly of the printed parts. At the same time watch the other end of the textile sleeve, if you pull the cable too much, the connector will disappear in the sleeve ;)

    • Take the smaller connector WITHOUT THE SENSOR! and carefully push it all the way through the IR-sensor-holder-mmu2s.

    • Once the connector is through, connect the cable and the sensor together.

    • Make sure the safety latch is facing up.

    • The sensor must be facing down.

    • Pictures show MK3S IR-sensor cable, but use the same procedure for the MK2.5S cable. This is valid for the entire manual.

  6. Take the IR-sensor and place it in the holder, make sure the orientation is the same as in the picture. Take cover and place it on the top. The cover is asymmetrical, see the picture.  The smaller gap in the cover should be on the left. Secure the IR-sensor and the cover using an M2x8 screw.
    • Take the IR-sensor and place it in the holder, make sure the orientation is the same as in the picture.

    • Take cover and place it on the top. The cover is asymmetrical, see the picture. The smaller gap in the cover should be on the left.

    • Secure the IR-sensor and the cover using an M2x8 screw.

  7. Carefully insert the cable in the channel, make sure it is all the way in. Take the FS-cover-mmu2s and push in the M3n nut. Slide the holder on the cover, again make sure it is all the way in, otherwise, the holes won't align properly.
    • Carefully insert the cable in the channel, make sure it is all the way in.

    • Take the FS-cover-mmu2s and push in the M3n nut.

    • Slide the holder on the cover, again make sure it is all the way in, otherwise, the holes won't align properly.

    • Secure both parts using an M3x10 screw, see the picture for the correct hole.

    • This entire IR-sensor assembly is also called "chimney" in the Handbook.

    • Tip: If you can't reach the nut, try pulling it up using a longer full-threaded screw from the spare bag.

  8. Place the entire IR-sensor assembly on top of the extruder. Align the left edge with the extruder body.
    • Place the entire IR-sensor assembly on top of the extruder.

    • Align the left edge with the extruder body.

    • Use a M3x18 screw to join both parts together.

    • Carefully pull the cable down until the loop disappears completely. However, don't stretch the cable.

    • Finish the sensor assembly by inserting an M3x40 screw.

    • Make sure all the gaps are gone.

  9. Tighten both M3x40 screws, make sure the printed parts are aligned before tightening. Tighten both M3x10 screws between the Extruder-body and X-carriage. Before you do so, ensure no cable is pinched between both parts, there is a channel in the X-carriage for all the cables.
    • Tighten both M3x40 screws, make sure the printed parts are aligned before tightening.

    • Tighten both M3x10 screws between the Extruder-body and X-carriage. Before you do so, ensure no cable is pinched between both parts, there is a channel in the X-carriage for all the cables.

  10. The fan has two sides, one has a Noctua sticker. Make sure, this side is facing inside the extruder. First, create a loop on the cable. Make sure the black protective wrap is close to the edge of the fan. See the picture. Slide the fan close to the X-carriage and GENTLY PUSH the cable in using an Allen key. Before you push the fan all the way to the left, place the cable in the X-carriage channel.
    • The fan has two sides, one has a Noctua sticker. Make sure, this side is facing inside the extruder.

    • First, create a loop on the cable. Make sure the black protective wrap is close to the edge of the fan. See the picture.

    • Slide the fan close to the X-carriage and GENTLY PUSH the cable in using an Allen key. Before you push the fan all the way to the left, place the cable in the X-carriage channel.

    • Fix the fan using following screws:

    • M3x14 (3x)

    • M3x18 (1x)

    • The M3x18 screw is also fixing the fan-shroud place it back, in case it fell down.

  11. For the following steps, please prepare: Extruder-idler-mmu2s (1x) Bondtech WITHOUT the hole for the lock screw (1x)
    • For the following steps, please prepare:

    • Extruder-idler-mmu2s (1x)

    • Bondtech WITHOUT the hole for the lock screw (1x)

    • Bearing (2x) might be stuck inside the gear

    • Shaft (1x)

    • M3n nut (1x)

    • M3x40 screw (2x)

    • Idler spring (1x) place the spring on the screw. The screw with the spring might be already in the extruder

  12. Insert both bearings in the pulley. Be aware that bearings can slip out during assembly.
    • Insert both bearings in the pulley. Be aware that bearings can slip out during assembly.

  13. Take M3n nut and place it in the Extruder-idler-mmu2s. Use the screw pulling technique. Insert the pulley in idler as shown in the picture.
    • Take M3n nut and place it in the Extruder-idler-mmu2s.

    • Use the screw pulling technique.

    • Insert the pulley in idler as shown in the picture.

    • Slide the shaft through the idler and pulley. Use reasonable force or you will BREAK the printed part.

    • Place your finger on the bearing and ensure it can rotate freely.

  14. For this step, please prepare: M3x40 screw (1x) Place the Extruder-idler-mmu2s in place and secure it using a M3x40 screw.
    • For this step, please prepare:

    • M3x40 screw (1x)

    • Place the Extruder-idler-mmu2s in place and secure it using a M3x40 screw.

    • Don't tighten the screw too firmly, it serves as a shaft for the idler. Check that the idler can rotate freely (the range of the movement is small).

    • Use the M3x40 screw with the spring to introduce tension to the Extruder-idler.

    • Hold the Extruder-idler on the other side, until the screw reaches the nut. Since there is only one screw, you need to introduce a large force. The head of the screw, should be aligned or slightly below the surface.

  15. Rotate the X-carriage-back back and push it gently towards the extruder. Ensure no wires are pinched between both parts!!!
    • Rotate the X-carriage-back back and push it gently towards the extruder. Ensure no wires are pinched between both parts!!!

    • Tighten all four M3x10 screws.

    • Tighten the screws with a reasonable force, make sure you won't deform/squeeze the bearings between the printed parts.

  16. For the following steps, please prepare:
    • For the following steps, please prepare:

    • Zip tie (5x)

    • MK2.5S extruder differs from now on! Please use another chapter and then return here. MK2.5S extruder cable management Follow the linked chapter to the very end, apart from the cables you need add one printed part.

  17. Gently twist the sleeve to make it smaller and tighter around the cables and slide the sleeve towards the extruder. Take 3 zip ties and insert them into the lower row of holes on the cable-holder. Twist the sleeve again (without twisting the cables inside) and tighten the zip ties.
    • Gently twist the sleeve to make it smaller and tighter around the cables and slide the sleeve towards the extruder.

    • Take 3 zip ties and insert them into the lower row of holes on the cable-holder.

    • Twist the sleeve again (without twisting the cables inside) and tighten the zip ties.

    • IMPORTANT: Cut the remaining part of each zip tie using pliers as closest to its head as possible. Note the correct position of each zip ties's head (slightly off-centre to the left).

    • Use two zip ties and push them through the upper slots on the cable-holder. Add the cables from the hotend and use the channel in the printed part to arrange them properly. Tighten the zip ties, cut the remaining parts.

  18. Carefully and quietly open the bag with the Haribo sweets.  High level of  noise might attract nearby predators!
    • Carefully and quietly open the bag with the Haribo sweets. High level of noise might attract nearby predators!

    • Sort the bears into six rows according to the following scheme (colours might differ):

    • Previous and current chapter were very difficult, at least 25 % of total amount is needed.

    • Idler assembly is quite easy, 10 % is enough.

    • Pulley body assembly requires your attention, eat no less than 20 % of all bears.

    • Electronics assembly is the last chapter with high level of difficulty, consume 25 %.

    • Spool holders with the buffer are easy to make, research shows that 10 % is enough.

    • Preflight check is almost effortless. Experienced user will require no more than 10 %.

  19. Are we there yet? We are just getting started! Important info only for those, who are upgrading from MMU2 to MMU2S (MMU2S unit already assembled), you can skip to chapter 6. Electronics and MMU2S unit assembly (Step 23)
    • Are we there yet? We are just getting started!

    • Important info only for those, who are upgrading from MMU2 to MMU2S (MMU2S unit already assembled), you can skip to chapter 6. Electronics and MMU2S unit assembly (Step 23)

    • Check the final look, compare it to the picture.

    • Don't worry about the cable, we will connect it later ;)

    • Checked everything? Let's move to: 4. Idler body assembly

Finish Line

205 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

2 Comments

There is no mentioning of reconnecting the filament sensor cable to the controller board in this guide.The cable is a 4 pin connector but my board has 8 pins, 4 top and 4 bottom. Where should I connect the connector?

Jesper Henriksen - Reply

Mr Henriksen, this chapter is dedicated to building the extruder, please follow the next chapters to learn how to connect the sensor cable to the controller board. Spoiler alert: always use the bottom row for the filament sensor.

Martin L. - Official Prusa CS -

Add Comment

View Statistics:

Past 24 Hours: 67

Past 7 Days: 493

Past 30 Days: 2,310

All Time: 18,841