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  1. Needle-nose pliers for zip tie trimming.
    • Needle-nose pliers for zip tie trimming.

    • 2.5mm Allen key for M3 screws

    • 2mm Allen key for nut alignment

    • 1.5mm Allen key for tightening the pulley

    • Use the bag "MK2.5 1"

    • Use the bag "2. Extruder"

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

    • Extruder-idler (1x)

    • Bondtech pulley WITHOUT the lock screw (1x)

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

    • M3nS nut (2x)

    • Pulley shaft (1x)

    • Note there are two types of the Bondtech pulley in the package (one with and without lock screw). Make sure you are using the correct one. For this step use the one WITHOUT the lock screw.

  3. Press the nuts to the slots on both sides of the idler. Insert both bearings in the pulley. Be aware that bearings can slip out during assembly.
    • Press the nuts to the slots on both sides of the idler.

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

    • Layers might be visible in this printed part due to the geometry. The functionality and strength remain unaffected.

  4. Ensure both bearings are inside the pulley! In case you have issues inserting the shaft in, please use 3mm drill bit and widen the hole first. Otherwise, you might crack this part.
    • Ensure both bearings are inside the pulley!

    • In case you have issues inserting the shaft in, please use 3mm drill bit and widen the hole first. Otherwise, you might crack this part.

    • 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.

  5. ATTENTION: 3D printed extruder parts were improved in order to achieve better cooling. More information including direct comparison can be found on our Prusa Research forum.
    • ATTENTION: 3D printed extruder parts were improved in order to achieve better cooling. More information including direct comparison can be found on our Prusa Research forum.

    • The assembly of the printed parts is mostly the same. You will be informed in case extra attention is needed. Before you proceed to the next step, let's learn how to recognize your parts:

    • Previous design has a grill on one side of the extruder body. This iteration has a label B6 (printed by us) or R2 (available on GitHub).

    • The latest design has NO grill to improve airflow. This iteration has a label B7 (printed by us) or R3 (available on GitHub).

    • If you have already printed the B6/R2 design you can proceed or if possible reprint the latest parts B7/R3.

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

    • Extruder-body (1x)

    • Filament sensor (1x)

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

    • M3x10 screw (1x)

    • M3n nut (2x)

  7. Before we continue with the assembly, we need to insert nuts in the Extruder-body. Take the extra time and effort to place them in properly. You won't be able to reach them later. Rotate the front part towards you and insert the M3 nut in the slot, all the way in.
    • Before we continue with the assembly, we need to insert nuts in the Extruder-body. Take the extra time and effort to place them in properly. You won't be able to reach them later.

    • Rotate the front part towards you and insert the M3 nut in the slot, all the way in.

    • Rotate the rear part towards you and insert the M3 nut in the slot, all the way in.

    • If you can't push the nuts in, use a longer screw from the other side and tighten it until you "pull" the nut in.

  8. Carefully insert the filament sensor in the slot, do not use force or you might damage the PCB! Carefully insert the filament sensor in the slot, do not use force or you might damage the PCB!
    • Carefully insert the filament sensor in the slot, do not use force or you might damage the PCB!

  9. Turn the extruder-body like in the picture. The pins of the filament sensor must be facing up. Locate the opening for the M3 screw.
    • Turn the extruder-body like in the picture. The pins of the filament sensor must be facing up.

    • Locate the opening for the M3 screw.

    • Take the M3x10 screw and tighten the sensor in place.

    • The sensor must be tightened completely to prevent its movement BUT BE CAREFUL during tightening to avoid damage to the sensor.

    • Layers might be visible in this printed part due to the geometry. The functionality and strength remain unaffected.

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

    • M3x30 screw (1x)

    • M3 translucent washer (2x)

    • Translucent washers are placed on the idler for better visibility. No need to place them as in the picture ;)

  11. Turn the Extruder-body like in the picture. The pins must be facing to the right. Insert M3x30 screw in the hole.
    • Turn the Extruder-body like in the picture. The pins must be facing to the right.

    • Insert M3x30 screw in the hole.

    • Place a washer from the other side.

    • Assemble the idler on the M3x30 screw.

    • Finish the assembly with the second washer.

  12. For the following step, please prepare:
    • For the following step, please prepare:

    • Extruder motor (1x)

    • Bondtech pulley WITH the lock screw (1x)

    • In case there is a pulley from the MK2S on the motor's shaft, please remove it now!

    • There is a second spare lock screw in the package.

  13. There is a flat part on the motor shaft, rotate it towards you. Slide the pulley on, note the CORRECT orientation. The screw must be facing directly against the pad (flat part) on the shaft. Slightly tighten the screw, the final adjustment will be done later.
    • There is a flat part on the motor shaft, rotate it towards you.

    • Slide the pulley on, note the CORRECT orientation.

    • The screw must be facing directly against the pad (flat part) on the shaft. Slightly tighten the screw, the final adjustment will be done later.

    • Don't press the pulley against the motor. Leave it on the very top of the shaft, see the picture.

    • Before moving to the next step, rotate the pulley 90-degrees clockwise ( the lockscrew will be facing to the left).

  14. Find in the package two M3x30 screws and insert them into the holes. Mount the motor on the extruder body as shown in the picture, double check the proper orientation of the motor cables.
    • Find in the package two M3x30 screws and insert them into the holes.

    • Mount the motor on the extruder body as shown in the picture, double check the proper orientation of the motor cables.

    • Tighten both screws firmly.

    • Tighten the screw, but only slightly, keep in mind the idler must rotate freely.

  15. Open idler fully to have direct access to the pulley. Use a piece of 1.75 mm filament (from the spool) to align the pulley with the openings for the filament (see the picture).
    • Open idler fully to have direct access to the pulley.

    • Use a piece of 1.75 mm filament (from the spool) to align the pulley with the openings for the filament (see the picture).

    • Adjust the pulley and tighten it with 1.5mm Allen key. Use reasonable force as you might damage the thread.

    • When ready with the alignment, please remove the filament.

  16. For the following step, please prepare: M3x40 screw (2x) Extruder spring (2x)
    • For the following step, please prepare:

    • M3x40 screw (2x)

    • Extruder spring (2x)

    • Assemble springs on both screws, see the second picture.

    • Close the idler, so the screws can reach it.

    • Place both screws into the Extruder body and tighten them. The screw's head should be almost aligned with the printed surface.

  17. Take two M3nS nuts from the package and insert them in the slots, all the way in. Check proper alignment with the 1.5mm Allen key.
    • Take two M3nS nuts from the package and insert them in the slots, all the way in.

    • Check proper alignment with the 1.5mm Allen key.

  18. ATTENTION: 3D printed extruder parts were improved in order to achieve better cooling. More information including direct comparison can be found on our Prusa Research forum.
    • ATTENTION: 3D printed extruder parts were improved in order to achieve better cooling. More information including direct comparison can be found on our Prusa Research forum.

    • The assembly of the printed parts is mostly the same. You will be informed in case extra attention is needed. Before you proceed to the next step, let's learn how to recognize your parts:

    • Previous design has a grill on one side of the extruder cover and extra fan arm. This iteration has a label B6 (printed by us) or R2 (available on GitHub).

    • The latest design has NO grill to improve airflow and also the arm is not present. This iteration has a label B7 (printed by us) or R3 (available on GitHub).

    • If you have already printed the B6/R2 design you can proceed or if possible reprint the latest parts B7/R3.

  19. For the following steps, please prepare: Extruder-cover (1x) M3nS nut (1x)
    • For the following steps, please prepare:

    • Extruder-cover (1x)

    • M3nS nut (1x)

    • M3n nut (1x) - skip for R3/B7

    • M3x25 screw (2x)

    • B6/R2 - insert both nuts in the printed part. See the second picture.

    • B7/R3 - insert only M3nS nut. See the last picture.

    • In case you can't press the M3n nut in, don't use excessive force. Take M3 screw thread it from the opposite side of the printed part, as you tighten the screw, it will pull the nut in. Be careful not to break the printed part during tightening.

  20. Take the E3D hotend and place it inclined into the Extruder body. Make sure the white PTFE tube (already part of the hotend) fits in properly. Push the hotend into the Extruder body, see the picture.
    • Take the E3D hotend and place it inclined into the Extruder body. Make sure the white PTFE tube (already part of the hotend) fits in properly.

    • Push the hotend into the Extruder body, see the picture.

    • Make sure the hotend is fully seated and the upper part aligned (almost in contact) with the surface of the printed part.

    • Note the CORRECT orientation of the hotend.

    • Be VERY CAREFUL with the hotend wires from now on, you can damage them.

  21. Rotate the extruder as shown in the picture. Take the extruder-cover and place it on the extruder body. Both printed parts must be in direct contact. Using M3x25 screws tighten both parts together.
    • Rotate the extruder as shown in the picture.

    • Take the extruder-cover and place it on the extruder body. Both printed parts must be in direct contact.

    • Using M3x25 screws tighten both parts together.

    • Ensure again the hotend is properly assembled. The surface of the heatsink (part of the hotend with cooling ribs) must be aligned with the surface of the printed parts. See the last picture.

    • Note the B7/R3 extruder cover is missing the "arm". Otherwise the assembly is the same.

  22. For the following steps, please prepare: M3x18 screw (6x)
    • For the following steps, please prepare:

    • M3x18 screw (6x)

    • New Left hotend fan (1x)

    • Front print fan (1x)

    • The new Left hotend fan has two sides, but the side with sticker must be always facing the hotend (not visible when the fan is mounted). Otherwise, the cooling won't work properly.

    • The left hotend fan (Noctua) can be also in a black colour without the rubber corners, other hardware parameters are the same.

    • Note for B7/R3 design only five M3x18 screws are needed, at the end of this chapter you might have one M3x18 left, which is OK ;)

  23. Place the Extruder on the side and guide the wires from the motor in the slot. Place the Left hotend fan on the Extruder. The cable must be placed in the top left corner, see the picture. Note the correct orientation of the fan. The sticker has to face towards the hotend!
    • Place the Extruder on the side and guide the wires from the motor in the slot.

    • Place the Left hotend fan on the Extruder. The cable must be placed in the top left corner, see the picture.

    • Note the correct orientation of the fan. The sticker has to face towards the hotend!

    • Insert M3x18 screws and tighten them slightly.

    • Now, tighten ALL screws, but on a diagonal. After tightening check, the fan can rotate freely.

    • DON'T tighten the screws too hard, all parts are made of plastic and you can break them.

  24. This step is valid only for the design B6/R2 if you have new parts B7/R3 without the grill please skip to the Step25. Rotate the Extruder as in the first picture.
    • This step is valid only for the design B6/R2 if you have new parts B7/R3 without the grill please skip to the Step25.

    • Rotate the Extruder as in the first picture.

    • Mount the Front print fan using two M3x18 screws.

    • DON'T tighten the screws too hard, all parts are made of plastic and you can break them.

  25. Following steps are valid only for the latest design B7/R3, if your Front print fan is already mounted,  then skip to the  Step28
    • Following steps are valid only for the latest design B7/R3, if your Front print fan is already mounted, then skip to the Step28

    • For the following steps, please prepare:

    • nozzle-fan-45deg-support (1x)

    • nozzle-fan-45deg (1x)

    • M3x18 screw (1x) - already prepared in step 22

    • M3x10 screw (2x)

    • M3n nut (1x)

    • Note your nozzle-fan might be black. If you received one M3x10 screw in a bag with the nozzle-fan, use it now.

  26. Press the M3n nut in the support, all the way in. It will be barely visible. If needed use a screw from the other side to pull the nut in, then remove the screw. WARNING: there are pins of the filament sensor on the other side of the extruder. Be careful as you might bend them during the following steps!!! Connect the support to the extruder using the M3x10 screw. Note the correct orientation in the picture.
    • Press the M3n nut in the support, all the way in. It will be barely visible. If needed use a screw from the other side to pull the nut in, then remove the screw.

    • WARNING: there are pins of the filament sensor on the other side of the extruder. Be careful as you might bend them during the following steps!!!

    • Connect the support to the extruder using the M3x10 screw. Note the correct orientation in the picture.

    • The inclined part of the support must be facing to the extruder cover.

    • Place the nozzle-fan on the extruder and secure it using M3x10 screw.

  27. Slide the Front print fan in the nozzle-fan. Secure the fan using a M3x18 screw.
    • Slide the Front print fan in the nozzle-fan.

    • Secure the fan using a M3x18 screw.

    • In case you are upgrading already assembled printer, it might happen the fan cable is too short and you can't incline the fan. First, try gently pull the cable from the spiral wrap. If this doesn't help unhook the cable (see the picture), but be extremely careful as you might disconnect the wires from the fan!

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

    • New P.I.N.D.A. probe (1x)

    • M3x10 screw (1x)

    • M3nS nut (1x)

    • The probe is a sensitive device, please handle it with care during the assembly!

    • The P.I.N.D.A. cable can be either black or grey, both probes are the same.

  29. Start with the front print fan wire and place it under the cable clip. Gently push the P.I.N.D.A. probe through the mount. Create a loop on the probe wire, then place the wire under the cable clip.
    • Start with the front print fan wire and place it under the cable clip.

    • Gently push the P.I.N.D.A. probe through the mount.

    • Create a loop on the probe wire, then place the wire under the cable clip.

    • Slide the M3nS nut in the slot and tighten the probe SLIGHTLY with the M3x10 screw.

    • The exact position of the P.I.N.D.A. probe will be adjusted later (in Chapter 9, Preflight check), so there is no need to adjust the probe or tighten the screw fully at this point.

  30. Place the Extruder on the Y-carriage as in the first picture. Take the cables from P.I.N.D.A. probe and Front print fan, slide it between the lower smooth rod and belt. Take the cables from Extruder motor and Left hotend fan, slide it between the lower smooth rod and belt.
    • Place the Extruder on the Y-carriage as in the first picture.

    • Take the cables from P.I.N.D.A. probe and Front print fan, slide it between the lower smooth rod and belt.

    • Take the cables from Extruder motor and Left hotend fan, slide it between the lower smooth rod and belt.

    • IT IS VERY IMPORTANT to place the cables as shown in the pictures. Please double check your steps.

    • Cables from hotend will be placed under the lowest smooth rod. We will arrange them later.

  31. For the following step, please prepare: M3x40 screw (1x) M3x30 screw (1x)
    • For the following step, please prepare:

    • M3x40 screw (1x)

    • M3x30 screw (1x)

    • M3x18 screw (1x)

    • Mount the Extruder on the X-carriage using the screws above. Tighten all screws, but not fully. We need to arrange the cables first.

    • Guide the cables through slots (channels) on both sides of the Extruder. On the left side, it is Front Print fan and P.I.N.D.A. probe, on the right side Extruder motor and Left Hotend fan.

    • Ensure the cables are in the channels and not pinched between printed parts. Now, tighten all screws, equally to prevent issues.

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

    • X-carriage-back (1x)

    • Cable-holder (1x)

    • M3n nut (2x)

    • M3x10 screw (1x)

    • The M3x10 screw will be used temporarily. Use any you have at your disposal.

    • M3x40 screw (1x)

  33. Insert the M3x10 screw in the X-carriage-back. Tighten it completely. Rotate the printed part and insert the M3n nut. Tighten the M3x10 screw until the nut slides in the printed part. Note the shape of the cutout for the nut, you might need to adjust (rotate) the nut.
    • Insert the M3x10 screw in the X-carriage-back. Tighten it completely.

    • Rotate the printed part and insert the M3n nut.

    • Tighten the M3x10 screw until the nut slides in the printed part. Note the shape of the cutout for the nut, you might need to adjust (rotate) the nut.

    • Remove the M3x10 screw and place it back in the spare bag.

  34. Prepare the M3x40 screw, M3n nut and cable-holder from the previous step. Tighten the screw all the way through the printed part.
    • Prepare the M3x40 screw, M3n nut and cable-holder from the previous step.

    • Tighten the screw all the way through the printed part.

    • Add the M3n nut, stop at about half the length of the screw's thread.

  35. Place the X-carriage-back as in the picture. Tighten the X-carriage-back and the cable-holder together. The screw's tip should be aligned with the nut on the other side. Don't screw it "deeper", or you will have issues with assembling the X-carriage-back on the X-carriage.
    • Place the X-carriage-back as in the picture.

    • Tighten the X-carriage-back and the cable-holder together.

    • The screw's tip should be aligned with the nut on the other side. Don't screw it "deeper", or you will have issues with assembling the X-carriage-back on the X-carriage.

    • Secure the screw by tightening the nut all the way to the surface. Do not use excessive force, as you might crack the printed part.

  36. Locate the cable for filament sensor in the package. There are two types of the connectors on the cable:
    • Locate the cable for filament sensor in the package.

    • There are two types of the connectors on the cable:

    • Connector for the sensor (used now)

    • Connector for the RAMBo board (used later)

  37. Use the cable from the previous step and connect it carefully to the filament sensor. Note the connector has two different sides. The side with safety pin must be on the left (white wire is facing up and red down). Gently rotate the cable (clockwise) to create a small loop, see the second picture.
    • Use the cable from the previous step and connect it carefully to the filament sensor.

    • Note the connector has two different sides. The side with safety pin must be on the left (white wire is facing up and red down).

    • Gently rotate the cable (clockwise) to create a small loop, see the second picture.

    • Push the cable through the opening on the X-carriage.

  38. Push the cables from the Extruder THROUGH the X-carriage-back. Start with the Front print fan and P.I.N.D.A. probe cables. In the next step add  Extruder motor and the Left hotend fan. Cables from hotend and filament sensor are NOT GOING through the X-carriage-back!
    • Push the cables from the Extruder THROUGH the X-carriage-back. Start with the Front print fan and P.I.N.D.A. probe cables.

    • In the next step add Extruder motor and the Left hotend fan.

    • Cables from hotend and filament sensor are NOT GOING through the X-carriage-back!

    • Slide the X-carriage-back towards the X-axis.

  39. Before pressing the X-carriage-back against the X-axis, place the filament sensor cable through the slot. See both pictures. Check the cables are not pinched between the X-carriage-back and the X-axis!!!
    • Before pressing the X-carriage-back against the X-axis, place the filament sensor cable through the slot. See both pictures.

    • Check the cables are not pinched between the X-carriage-back and the X-axis!!!

  40. Using five M3x10 screws tighten the parts together in following order: Start in the middle and ensure proper alignment.
    • Using five M3x10 screws tighten the parts together in following order:

    • Start in the middle and ensure proper alignment.

    • Continue in the corners, tighten all screws equally.

  41. There is a NYLON filament included in the kit with length 50 cm and Ø 3 mm. DON'T TRIM it! Using the pliers cut one end of the filament to create a tip. Check the tip is similar to the third picture.
    • There is a NYLON filament included in the kit with length 50 cm and Ø 3 mm. DON'T TRIM it!

    • Using the pliers cut one end of the filament to create a tip.

    • Check the tip is similar to the third picture.

  42. The NYLON filament must be pressed through the opening in the X-carriage-back to a circular slot in the X-carriage. See the second picture, where both printed parts are shown without cables.
    • The NYLON filament must be pressed through the opening in the X-carriage-back to a circular slot in the X-carriage.

    • See the second picture, where both printed parts are shown without cables.

  43. Using the pliers insert the black NYLON filament in the slot. BE EXTREMELY CAREFUL as the pliers tend to slide and you can easily damage the wires!!!
    • Using the pliers insert the black NYLON filament in the slot.

    • BE EXTREMELY CAREFUL as the pliers tend to slide and you can easily damage the wires!!!

    • To check if the filament is seated properly, gently pull it with your hand. The X-axis should bend a little, but the filament must remain in the slot.

    • If you have issues, try to adjust the tip on the filament.

  44. Guide the filament sensor cable through the slot in the X-carriage-back and join the remaining cables. Wrap the spiral wrap (the largest and the longest one) around the cables and the nylon filament.
    • Guide the filament sensor cable through the slot in the X-carriage-back and join the remaining cables.

    • Wrap the spiral wrap (the largest and the longest one) around the cables and the nylon filament.

    • Start with cables from the upper part, after 3-4 turns slide the wrap on the cable-holder. If possible, press the wrap slightly in the X-carriage-back.

  45. Use three zip ties to fix the spiral wrap on to the cable-holder Check for the last time both the wrap and cables are seated properly.
    • Use three zip ties to fix the spiral wrap on to the cable-holder

    • Check for the last time both the wrap and cables are seated properly.

    • PAY GREAT ATTENTION to the final position of the zip ties. If you don't follow the manual, you will have issues during prints!

    • Tighten zip ties and cut remaining parts.

  46. Now, use two zip ties and before tightening them add the cables from the hotend. Once the hotend cables are included, tighten the zip ties and cut remaining parts.
    • Now, use two zip ties and before tightening them add the cables from the hotend.

    • Once the hotend cables are included, tighten the zip ties and cut remaining parts.

  47. Make one more turn of the spiral wrap, then add the cables from the hotend. Wrap the whole cable bundle.
    • Make one more turn of the spiral wrap, then add the cables from the hotend.

    • Wrap the whole cable bundle.

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

    • Idler-plug (1x)

    • Filament-sensor-cover (1x)

    • PTFE tube (1x)

    • M3x10 screw (2x)

  49. Locate the largest circular opening for the PTFE tube on the top of the Extruder. Push the PTFE tube in. Most of the tube's length will stick out.
    • Locate the largest circular opening for the PTFE tube on the top of the Extruder.

    • Push the PTFE tube in. Most of the tube's length will stick out.

    • In case the PTFE does not hold properly in the hole, you can assembly it to the cover first, BUT MAKE SURE the is no obstacle in the hole as you can easily deform the tube while placing as a part of the cover.

  50. Carefully slide the filament cover on the PTFE tube. Using two M3x10 screws mount the cover.
    • Carefully slide the filament cover on the PTFE tube.

    • Using two M3x10 screws mount the cover.

  51. Locate the part, where the idler is cut out (M3 screw is visible). Assemble the idler-plug and ensure it fits properly. Otherwise, it might fall down during the print.
    • Locate the part, where the idler is cut out (M3 screw is visible).

    • Assemble the idler-plug and ensure it fits properly. Otherwise, it might fall down during the print.

  52. In case of parts B7/R3 your fan-nozzle is already mounted, skip this step. For the following step, please prepare: Fan-nozzle (1x)
    • In case of parts B7/R3 your fan-nozzle is already mounted, skip this step.

    • For the following step, please prepare:

    • Fan-nozzle (1x)

    • M3x10 screw (1x)

    • Carefully slide the X-axis up so you have access to the lower part of the Extruder.

    • Release slightly both screws on the front print fan.

    • Assemble the fan-nozzle and tighten all three screws.

  53. Are we there yet? Almost! You've just finished the hardest part of the assembly. Awesome job!
    • Are we there yet? Almost! You've just finished the hardest part of the assembly. Awesome job!

    • Check the final look, compare it to the picture. Note with B7/R3 parts the extruder looks different.

    • Checked everything? Let's move to: 5. Heatbed assembly

Finish Line

115 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

222 Guides authored

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Prusa Research Member of Prusa Research

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364 Guides authored

8 Comments

Step 38: it is much easier to insert the nylon filament BEFORE the X-carriage back is attached.

Philip de Lang - Reply

Hi Philip, yes the procedure is already changed for the MK3 and update for MK2.5 is on the way.

Jakub Dolezal -

Step 24: my pinda holder broke off trying to get the probe in. Tip: alter the extruder body so that the pinda probe holder has a separate loose cover, it is also much easier to adjust the height of the probe this way. By breaking of the holder, I actually have this situation.

Philip de Lang - Reply

Clicked the +30 button… considered complaining that it should be less because this sequence is so complicated, but really the fix would be to split it into two parts… so the +30 is only half what that would be :-)

David H. Brown - Reply

Step 20 should specify also the Bowden tube length… people who upgrade from a machine with MMU1.0 would have too short of a Bowden tube

Ergo Esken - Reply

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