⬢For this chapter, please prepare:
⬢1.5mm Allen key
⬢2.5mm Allen key
⬢Torx key TX6
⬢Torx key TX10/8
⬢Needle-nose pliers
⬢Permanent marker
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- Original Prusa i3 MK3/MK3S/MK3S+ to MK4 upgrade
- 5. Nextruder assembly
5. Nextruder assembly
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- Original Prusa i3 MK3/MK3S/MK3S+ to MK4 upgrade
- 1. Introduction
- 1a. Parts check
- 1b. Printer disassembly
- 1c. Parts preparation
- 2. Frame assembly
- 3. X-axis & X-carriage assembly
- 4. Z-axis assembly
- 5. Nextruder assembly
- 1. Tools necessary for this chapter
- 2. Filament sensor: parts preparation
- 3. Assembling the filament sensor
- 4. Assembling the filament sensor
- 5. Nextruder idler assembly: parts preparation
- 6. Assembling the extruder idler
- 7. Assembling the extruder: parts preparation I.
- 8. Assembling the extruder: parts preparation II.
- 9. Assembling the extruder
- 10. Assembling the gearbox
- 11. Assembling the PG-ring
- 12. Assembling the PG-assembly
- 13. Checking the PG-assembly
- 14. Assembling the Nextruder idler
- 15. Covering the planetary gear
- 16. Assembling the Idler-swivel: parts preparation
- 17. Assembling the Idler-swivel
- 18. Assembling the Idler-nut
- 19. Mounting the Idler-swivel assembly
- 20. Attaching the extruder: parts preparation
- 21. Assembling the heatsink
- 22. Attaching the extruder
- 23. Connecting the NTC thermistor
- 24. Assembling the hotend fan: parts preparation
- 25. Assembling the hotend fan
- 26. Inserting the hotend assembly: parts preparation
- 27. Inserting the hotend assembly
- 28. Connecting the hotend cables
- 29. Assembling the fan-door: parts preparation
- 30. Assembling the fan door
- 31. Assembling the fan-door
- 32. Assembling the fan-door
- 33. Assembling the fan-door
- 34. Assembling the fan-door
- 35. Connecting the extruder cables
- 36. Connecting the print fan
- 37. LoveBoard: Wiring check
- 38. Covering the LoveBoard: parts preparation
- 39. Covering the LoveBoard
- 40. Covering the LoveBoard
- 41. Tensioning the X-axis belt
- 42. Belt tension check
- 43. Testing the X-axis belt
- 44. Haribo time!
- 45. The extruder is assembled
- 6. xLCD assembly
- 7. Y-carriage & Heatbed assembly
- 8. Preflight check
- Manual changelog
5. Nextruder assembly
Relevant for:
Last updated 2 months ago Difficulty
Moderate Steps
45 Available languages
⬢For the following steps, please prepare:
⬢Nextruder heatsink (1x)
⬢Hall filament sensor (1x)
⬢Prusa ball holder (1x)
⬢Magnet 3x3x3 mm (1x)
⬢Spring 3x9 mm (1x)
Note: the small spring can sometimes be stuck in the large spring in the package. Carefully inspect the contents of the bag.
Note: the small spring can sometimes be stuck in the large spring in the package. Carefully inspect the contents of the bag.
⬢Steel ball 4 mm (1x)
⬢M2.5x6rT screw (1x)
⬢Place the Hall filament sensor into the similarly shaped pocket in the heatsink.
⬢Fix it with M2.5x6rT screw. Tighten it very carefully, you can crack the electronics board.
⬢Assemble the Prusa ball holder in the following order:
⬢Steel ball
⬢Magnet
⬢Spring
Be sure to insert only one magnet. One extra magnet is included as a spare. The magnets may snap together and appear as one. Check carefully.
⬢Insert these parts into the Prusa ball holder with the steel ball up.
⬢Insert the Prusa ball holder assembly into the heatsink. Make sure the steel ball part is closer to the side of the heatsink.
Note the correct orientation of the Prusa ball holder assembly. There is a protrusion on the part. The protrusion must be facing down.
⬢Push the assembly into the heatsink.
⬢For the following steps, please prepare:
⬢Idler-lever-b (1x)
⬢Idler-lever-a (1x)
⬢Bearing 693 2RS (2x)
⬢Pin 2.9x8.5 (2x)
⬢M3x6 screw (1x)
⬢Tubular spacer 13.2x3.8x0.35 (1x)
⬢Insert the pin 2.9x8.5 into each bearing 693 2RS, as seen in the picture.
⬢Place both bearings with the pins into the Idler-lever-b.
⬢Close it up with the Idler-lever-a part and secure it with the M3x6 screw. Do not overtighten the screw. Both bearings must be able to rotate without significant resistance.
⬢From the same side, push the tubular spacer into the assembly. The "bottom" of the tubular spacer must be flush with the bottom part of the Idler assembly.
⬢For the following steps, please prepare:
⬢PG-case (1x) you will use it later
If your package contains an injection-molded PG-case, these instructions are for a different model. These parts are for MK4S and MK3.9S printers. Please visit help.prusa3d.com to find the correct manual.
⬢Main-plate (1x)
⬢PG-assembly-adapter (1x)
⬢PG-assembly (1x)
⬢PG-ring (1x)
The list continues in the next step...
⬢Extruder motor (1x)
⬢M3x25 screw (3x)
⬢Spacer 5x10x0.1 mm (1x)
⬢Socket set screw M3x25 (1x)
⬢Lubricant (1x)
⬢Attach the 5x10x0.1 spacer over the shaft on the extruder motor.
⬢Place the heatsink on the extruder motor. Note the orientation of both parts.
⬢The motor cable must be facing "up".
⬢The heatsink cables must be on the right side.
⬢Place the main-plate on the heatsink. Note the orientation of the part. Use the cutout as a guide.
Before proceeding to the next step, make sure that the 5x10x0.1 spacer is placed on the extruder motor.
The following instructions need to be done correctly and carefully. Achieve better understanding and successful assembly by watching the video alongside the guide: prusa.io/PG-assembly
⬢After watching the video, follow the steps in this guide.
⬢Attach the PG-assembly-adapter on the PG-assembly. Note the pockets for the gears in the adapter.
Do not assemble the gearbox without the PG-assembly-adapter. This tool is intended to ensure that the gears are correctly fit together.
⬢Slide the PG-ring onto the adapter.
⬢Note there is a chamfer on one side of the PG-ring teeth. This side must be facing down (to the PG-assembly).
⬢Grasp the entire assembly in one hand so that it can be rotated with the PG-ring.
⬢With the other hand, slide the PG-ring onto the PG assembly in a wobbling motion (move the PG-ring left and right repeatedly) - a quarter turn is enough.
⬢Stop when the surfaces of the gears are approximately flush with the surface of the PG ring.
Proceed very carefully in this step.
⬢Maintain the position of the PG-assembly and attach it on to extruder motor shaft.
⬢Very gently and freely rotate with the whole PG assembly (PG-assembly-adapter, PG-assembly and PG-ring) until it drops down so that there is no gap between the assembly and the main-plate. Do not push on the assembly.
⬢Remove the PG-assembly-adapter.
⬢Attach the PG-assembly-adapter back on the PG-assembly again to verify that all parts are properly seated.
⬢Rotate with the PG-assembly-adapter. The movement of the PG assembly must be smooth and there should be no significant resistance.
⬢Remove the PG-adapter. You will no longer need it during assembly. We recommend keeping it for maintenance.
⬢Ensure that the PG-assembly is not sticking out above the PG-ring. It should be positioned lower than the level of the PG-ring's surface or at the same level as the ring.
⬢Ensure that the gap between the PG-ring and the Main-plate is minimal. If a significant gap is observed, disassemble the planetary gear assembly and reposition it.
⬢Insert the idler assembly between the PG-ring and the extruder motor. There is a cutout for the spacer in the main-plate. Line up the idler spacer with the hole in the PG-ring.
⬢Secure both parts with the socket set screw 3x25. Do not overtighten the screw! The screw protrudes from the PG-ring after tightening.
⬢Apply a small amount of Prusa Lubricant all around the PG-ring and PG-assembly teeth.
Tip: apply a small amount of lubricant to the tip of the zip tie and then spread the lubricant over the gears.
⬢Using a paper towel, wipe off any excess lubricant on the front surfaces.
⬢Take the PG-cover and make sure the plastic ring is already inserted in the part.
⬢The color of the plastic ring might vary. The properties are the same.
⬢Cover the planetary gear and secure the PG-case with three M3x25 screws. Do not overtighten the screws!
⬢For the following steps, please prepare:
⬢Idler-nut (1x)
⬢Idler-swivel (2x)
⬢M3x30 screw (2x)
⬢M3x20rT screw (2x)
⬢M3nN nut (2x)
⬢Spring 15x5 (2x)
⬢Spacer 6x3.1x8 (1x)
⬢ In some older packages this part is called "Spacer 5.5 mm".
⬢Push the M3x20rT screw all the way through one of the idler-swivel.
⬢Slide the spacer onto the screw.
⬢Place the second idler-swivel from the opposite side on the screw.
⬢From the other side, attach the M3nN nut onto the screw. Hold the nut using the universal wrench and tighten the screw. Tighten just lightly! The spacer must rotate freely.
⬢Insert the Idler-nut into the Idler-swivel assembly. Make sure that both parts are oriented correctly according to the picture.
⬢Secure both parts together by inserting the M3x20rT screw from the same side, like the first screw.
⬢Secure the screw with M3nN nut. Do not overtighten the nut. It must be possible to move with the Idler-swivel on the Idler-nut.
⬢Attach the spring 15x5 on both M3x30 screws.
⬢Push the two screws with the springs through the holes in the protrusion on the heatsink. There are no threads inside.
⬢Attach the Idler-swivel assembly on the screws. See the correct orientation of the Idler-nut. The side with version marking must be visible. See the picture.
⬢Tighten both screws. Stop tightening as soon as the screw tips reach the front face of the idler nut.
⬢For the following steps, please prepare:
⬢Thumb screw (2x)
⬢M3x10 screw (3x)
⬢M3x4T grub screw (1x)
⬢NTC thermistor 90 mm (1x)
The color variant of the cable may vary.
⬢On the extruder motor side, insert the NTC thermistor into the hole in the heatsink.
⬢Secure it with the M3x4T grub screw. Screw it all the way in. Tighten gently, but firmly using two fingers and the short side of the T6 Torx key. Applying more force may cause permanent damage to the thread.
⬢Insert two thumb screws into the heatsink. Do not tighten them completely. Two turns are enough for now.
⬢Place the Nextruder onto the spacers on the X-carriage.
⬢There is a cutout in the plastic part. Guide the thermistor cable through this cutout.
DO NOT PINCH ANY OF THE CABLES!
⬢Align the heatsink holes with the spacers on the X-carriage and join both parts together with three M3x10 screws. Start with the middle one.
⬢Locate the cable channel on the left side of the X-carriage. We will guide some of the cables through this channel in the following steps
⬢Guide the NTC thermistor through the cable channel in the X-carriage up to the LoveBoard slot and connect the plug to the marked socket.
⬢For the following steps, please prepare:
⬢Hotend fan (1x)
⬢M3x18 screw (2x)
⬢Attach the hotend fan onto the heatsink with two M3x18 screws on the left side. Tighten the screw gently, but firmly, otherwise the plastic housing may crack. The cable must be pointing towards the lower-left corner.
There is a sticker on the hotend fan, the sticker must be on the rear side of the fan - not visible.
⬢Guide the fan cable between the thumb screws under the cable channel up and connect it to the lower slot on the LoveBoard.
⬢For the following steps, please prepare:
⬢Hotend assembly (1x)
⬢Locate the hole in the heatsink from the bottom of the extruder and insert the hotend into the heatsink.
⬢Guide the hotend cables freely to the left.
⬢Push the hotend assembly all the way into the heatsink. There should be approximately a 2 mm gap between the heatsink and the brass part of the nozzle.
⬢While pushing the hotend assembly in, firmly tighten both thumb screws.
Avoid pinching any cable between the screws and the heatsink!
⬢Orient the hotend assembly so that the HOT symbol on the heaterblock faces forward.
⬢Guide the hotend thermistor through the cable channel in the X-carriage and connect it to the LoveBoard.
There are several variations of the hotend thermistor. They differ in color and length. Functionally they are the same.
⬢If you have the hotend thermistor with a long cable, make a loop near the connector. Do not twist the cable too much.
⬢Guide the hotend heater through the cable channel in the X-carriage and connect it to the LoveBoard.
⬢For the following steps, please prepare:
⬢Fan-door (1x)
⬢Fan-shroud (1x)
⬢Print fan (1x)
⬢M3x30 screw (1x)
⬢M3x10 screw (2x)
⬢M3x6 screw (2x)
⬢Magnet 20x6x2 (2x) Keep the magnets apart in a sufficient distance. They can break each other!
⬢Insert the magnet into the pocket on the inside of the fan-door.
⬢Arrange the print fan as seen in the picture. Guide the cable through the channel in the plastic part. Keep a small gap between both parts.
⬢Turn (close) the fan around and attach it to the fan-door by using two M3x6 screws.
⬢Pull the fan cable very gently to reduce the slack as much as possible.
⬢Turn the fan-door assembly as shown.
⬢Attach the fan-shroud to the fan-door and align the holes in both parts.
⬢Join both parts together with two M3x10 screws.
It is recommended to prepare the permanent marker for this step.
⬢Slowly get the free magnet close to the magnet in the fan-door and find out which two sides are attracted to each other.
Be careful that the magnets do not stick together, it will be difficult to separate them.
⬢Mark the sides that are attracted to each other with a permanent marker.
⬢Locate the hole for the magnet on the left side of the X-carriage.
Before inserting the magnet into the part, double-check that the marked part of the magnet is FACING YOU. The magnet cannot be removed from the part afterward.
⬢Insert the magnet into the hole so that the marked side is facing out of the X-carriage (to you).
⬢Push the magnet all the way down.
⬢Attach the fan-door hinge into its counterpart in the X-carriage. Holes in both parts must be aligned
⬢Insert the M3x30 screw in the hinge on the fan-door. Fully tighten the screw, then loosen it by a quarter turn. The fan-door must move freely!
⬢Connect the Extruder motor cable to the connector on the top side of the LoveBoard.
⬢Connect the Loadcell cable coming from the right of the heatsink to the upper slot on the right side of the LoveBoard.
⬢Connect the filament sensor cable to the lower slot on the right side of the LoveBoard.
⬢Connect the print fan cable to the middle slot on the left side of the Loveboard.
Before covering the electronics, check the connection of all cables. Click on high-resolution preview in the top left corner.
⬢Close the idler mechanism before proceeding to the next step if you haven't already done so. Use the following sequence:
⬢Close the extruder idler to the extruder
⬢Close the idler-swivel and lock it over the extruder idler assembly
⬢For the following steps, please prepare:
⬢LoveBoard-cover (1x)
⬢LoveBoard-cover-right (1x)
⬢M3x10 screw (1x)
⬢Curve and arrange the cables on the right side of the extruder as you can see in the picture.
⬢Cover the cables with the LoveBoard-cover-right.
Do not pinch the cables!
⬢Secure it with the M3x10 screw.
Make sure the LoveBoard-cover-right fits snugly against the right side of the extruder. If not, it may cause the X-axis test to fail during the self-test because it will prevent the X-carriage assembly from moving all the way to the right.
⬢Push all cables to the extruder to make more space around them. See the picture.
⬢Slide the Loveboard-cover on the extruder. And push it all the way down.
Be careful not to pinch any cables.
⬢Ensure that the two plastic covers fit together perfectly.
In this step, we will finish tensioning the belt. Please read the instructions first, your belt might have proper tension already, then there is no need for additional screw adjustment.
⬢First, slightly release all the screws holding the motor, otherwise, the "tensioner" won't work (the motor must be able to move).
⬢Using ball-end Allen key start tightening the screw on the rear side of the X-end-motor, but after each turn or two check the tension in the belt.
⬢For the optimal performance, the belt must be a bit harder to press with your fingers. Move the extruder all the way to the X-end-idler and try the belt tension in the middle of the X-axis.
⬢When you achieve optimal tension, please tighten the screws again.
This step is recommended, but optional. If you don't have a phone at your disposal, continue to the next step. You can do this check later on.
⬢To verify or fine-tune the X or Y-axis belt tension on your printer, visit prusa.io/belt-tuner and open up the webpage on your mobile device. Or using your phone, scan the QR code in the picture.
⬢Watch the instructional video on prusa.io/belt-tuner-video and fine-tune your X belt tension, if required.
The belt tuner app was tested on multiple phones and should work across all most common phone manufacturers. However, in some rare cases it might not work as expected. Please state your brand and model in the comments below the step.
⬢Use the technique described below to test if the belt is properly stretched.
⬢Grasp and hold the flat part of the X motor shaft with pliers. This will prevent it from rotating in the pliers.
⬢Move the extruder towards the X motor. Don't use excessive force.
⬢If the belt is stretched properly, you should feel a resistance and the extruder 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.
⬢Eat five gummy bears.
Did you know that gummy bears have a long shelf life, typically lasting for up to two years if stored properly in a cool and dry place. But don't do that now.
⬢That was tough. But we made it!
⬢Let's go the next chapter: 6. xLCD assembly
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