⬢Please prepare tools for this chapter:
⬢Needle-nose pliers
⬢1.5mm Allen key for nut alignment
⬢2.5mm Allen key for M3 screws
⬢A measurement tool (optional), a digital caliper would work the best.
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- Original Prusa MMU3 Assembly
- 6. Pulley Body Assembly
6. Pulley Body Assembly
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- Original Prusa MMU3 Assembly
- 1. Introduction
- 2. MMU2S Disassembly (UPG)
- 3. MMU2S Buffer Disassembly (UPG)
- 4. Idler Body Assembly
- 5. Selector Assembly
- 6. Pulley Body Assembly
- 1. Tools necessary for this chapter
- 2. Pulley-body parts preparation
- 3. Pulley body: Inserting bearings
- 4. Pulley-body parts preparation
- 5. Front-PTFE-holder assembly
- 6. Collet holder parts preparation
- 7. Collets installation
- 8. Collet holder installation
- 9. Pulley motor parts preparation
- 10. Pulley assembly
- 11. Pulley motor assembly (part 1)
- 12. Pulley motor assembly (part 2)
- 13. Pulley alignment
- 14. Selector: parts preparation
- 15. Selector installation
- 16. Selector movement check / motor prep
- 17. Selector motor installation
- 18. Trapezoid nut positioning
- 19. Idler body installation parts preparation
- 20. Idler body installation (part 1)
- 21. Idler body installation (part 2)
- 22. Idler body installation (part 3)
- 23. Control board parts preparation
- 24. Control board assembly
- 25. PD-board parts preparation
- 26. Installing the PD-board-cover
- 27. PD-board installation
- 28. Connecting the cables
- 29. Electronics assembly
- 30. Textile sleeve parts preparation
- 31. Cable management (part 1)
- 32. Cable management (part 2)
- 33. Frame holders parts preparation
- 34. Frame holders assembly
- 35. Label plate installation
- 36. Rear PTFE parts preparation
- 37. Rear PTFE installation
- 38. Setting the Idler tension
- 39. Stickers parts preparation
- 40. Applying the stickers
- 7. Cassette Buffer Assembly
- 8. Spool holder Assembly
- 9A. MK4/S, MK3.9/S Nextruder mod
- 9B. MK3S+ / MK3.5 Extruder mod (KIT)
- 9C. MK3S+ Extruder (UPG)
- 10A. MK4/S, MK3.9/S Setup and Calibration
- 10B. MK3S+ Setup and Calibration
- 10C. MK3.5 Setup and Calibration
- 11. First Flight
6. Pulley Body Assembly
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Last updated 3 months ago Difficulty
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⬢For the following steps, please prepare:
⬢Pulley body (1x)
⬢625 bearing (3x)
⬢Insert one of the 625Z bearings into the marked side opening on the back of the Pulley body. Push it in until flush with the surface.
In case you have trouble getting the bearing inserted fully, try pushing it in against a side of a table.
⬢Insert the second bearing into the groove on the opposite side of the pulley-body.
⬢Insert the third bearing into the marked groove on the inside of the Pulley body. Insert it at an angle and tilt it in place.
⬢For the following steps, please prepare:
⬢Front PTFE-holder (1x)
⬢M3nS nut (4x)
⬢M3x10 screw (4x)
⬢PTFE tube 19mm (5x)
MMU2S and MMU3 PTFE tubes differ. If you are upgrading your MMU, Make sure you are not re-using the MMU2S PTFE tubes.
All the PTFE tubes are supplied pre-cut to the correct size. There is no need to cut the tubes.
⬢Insert the four M3nS nuts into the marked openings on the idler body. Push the nuts all the way down with the 1.5mm Allen key.
⬢Insert the five 19mm PTFE tubes into the marked openings in the pulley body.
There is a small chamfer on one side of the PTFE tubes. The chamfer should be facing out.
⬢Attach the Front PTFE holder onto the PTFE tubes and push it all the way towards the Pulley body. Mind the correct orientation seen in the picture.
⬢Secure the holder with four M3x10 screws from the front.
⬢For the following steps, please prepare:
⬢Collet holder (1x)
⬢M3n nut (2x)
⬢M3x10 screw (2x)
⬢Collet (5x)
⬢Take the collet holder. Note the correct part orientation marked by the imprinted arrow.
⬢Insert the collets into the marked openings on the collet holder.
⬢For the sake of easier installation, you might need to squish the fins on the collet with your fingers while you insert the collet. Then it will click in easily.
⬢Insert two M3n nuts into the marked openings on the bottom of the pulley body. Push the nuts all the way in.
⬢Attach the nut to the end of the M3x30 screw. Use the screw as a handle for inserting the nut.
⬢Attach the collet holder into the pulley body. Note the correct part orientation marked by the arrow.
The arrow on the collet holder should be pointing towards the pulley body.
⬢Secure the collet holder in place by two M3x10 screws.
⬢For the following steps, please prepare:
⬢
Pulley motor (1x)
⬢Pulley (5x)
In case you're upgrading from the MMU2S, the pulleys might be already attached to the motor.
⬢M3nS nut (1x)
⬢M3x10 screw (3x)
⬢Orient the motor as seen in the pictures. Make sure the motor cable is facing to the back.
⬢Rotate the motor shaft so that the flat part is facing up.
⬢Slide the first pulley onto the shaft. Ensure the lock screw is on top (facing the flat part of the shaft). Tighten the grub screw just slightly.
⬢The first pulley should be around 30 mm (1.18 inches) from the motor. Don't tighten the grub screw fully yet!
⬢Ensure the grooved part of the pulley is on the motor side.
⬢Slide the other pulleys onto the shaft using the same technique. Tighten the grub screws just slightly for now.
⬢Insert the M3nS nut into the marked slot on the pulley body. Push it all the way in.
⬢Orient the motor shaft so that all the grub screws on the pulleys are facing up.
⬢Make sure the motor cable is facing to the right (to the back of the MMU unit)
⬢Insert the motor into the pulley body as seen in the picture.
⬢Make sure the motor shaft has engaged into the bearing at the end of the groove.
⬢
Attach the motor with one M3x10 screw on top.
Just start the thread so that it holds in, don't tighten it up yet!
⬢
Turn the unit around and attach the motor with the other two M3x10 screws at the bottom. Use the ball-end 2.5mm Allen key at an angle to tighten up the screws fully.
Make sure, the screw is perfectly perpendicular to the motor while tightening. If it is hard to turn, release the screw fully, re-align it, and start tightening it from the beginning to avoid cross-threading it.
⬢Now, turn the unit around again to tighten up the top screw fully too.
WARNING: this step is crucial in order for the MMU unit to work properly! Please check your pulley alignment multiple times!!!
⬢
The groove inside the pulley must be perfectly aligned with the filament openings in the pulley body.
Align the pulleys one by one.
⬢Take a perfectly straight piece of filament and guide it through the first opening. Align the pulley so that the filament is perfectly centered.
⬢Make sure the lock screw is still perpendicular to the flat part of the shaft. Then tighten it. Use reasonable force as you might strip the screw.
⬢Align and tighten the remaining four pulleys using the same technique.
Check the proper positioning of all of the pullies again. Adjust it if necessary.
⬢For the following steps, please prepare:
⬢Selector assembly (1x) you prepared earlier.
⬢Selector motor (1x)
⬢5x120sh Shaft (2x)
⬢M3nS nut (2x)
⬢M3x10 screw (3x)
⬢
Insert two M3nS nuts into the marked openings in the pulley body. Push the nuts all the way in.
⬢Insert the selector into the pulley body as seen in the picture.
⬢Insert the two shafts through the marked openings in the pulley body. The shafts must pass through the selector and engage into the other side of the pulley body.
⬢Push the shafts in until they are fully inserted - slightly below the surface on the side.
⬢Verify the selector can move around freely while the rods are in place.
⬢Insert the selector motor so that its trapezoidal shaft goes through the pulley body as seen in the picture.
⬢Make sure the selector motor cable is pointing up before you proceed to attach the motor.
⬢
Rotate the threaded rod while pushing it towards the selector to engage it into the trapeze nut.
Continue rotating the rod until it passes entirely through, leaving around 2cm / 1in. of the shaft exposed on the left side of the selector.
⬢Ensure that the selector motor cable is oriented upwards.
⬢Push the motor all the way in. Check there is some clearance between the selector and the end of its travel on the left.
⬢Attach the selector motor to the pulley body with two M3x10 screws in the marked openings. Tighten them up using the ball-end 2.5mm Allen key.
⬢Add the last M3x10 screw in the corner. Tighten it snugly. Don't overtighten the screw in the corner! Otherwise, you might tilt the selector motor.
⬢Using the ball-end 2.5mm Allen key, slightly loosen the two screws holding the trapezoid nut on the selector. Don't remove them completely.
⬢Verify the selector can move when forced left and right. There should be no hiccups along the way. Note that you have to excert some force to move it as the motor has physical resistance.
⬢Move the selector all the way to the left.
⬢Fully tighten the two screws that secure the trapezoid nut.
⬢Idler assembly(1x) with the idler and motor installed
⬢M3nS nut (1x)
⬢M3x10 screws (2x)
⬢M3x30 screws (2x)
⬢15x5 Springs (2x)
⬢5x16sh Shaft (2x)
⬢Attach the Idler assembly onto the pulley body as seen in the picture. The Idler motor should be on the left.
⬢Now, take a look from the opposite side of the unit.
⬢Insert the 5x16 shaft into the marked opening and push it all the way in until it engages into the bearing in the pulley body.
⬢Insert the other 5x16 shaft into the marked opening on the other side. Push it all the way in.
⬢Fix the shaft in place by attaching the M3x10 screw into the opening above it.
⬢Fix the shaft on the other side in place by attaching the M3x10 screw into the opening above it too.
⬢Open up the Idler body.
⬢Insert the M3nS nut into the marked opening on the inside of the Pulley body. Push it all the way in.
You may need to move the selector away slightly, in order to access the opening.
⬢Attach both springs onto the two M3x30 screws.
⬢Close the Idler, insert the M3x30 screws with the springs into the marked openings. Tighten them until the screws are just above the surface.
Do not tighten the screws too much. The top of the screw heads shouldn't be below the surface.
Later on, we will use these screws to set the Idler tension.
Later on, we will use these screws to set the Idler tension.
⬢For the following steps, please prepare:
⬢Electronics cover (1x)
There have been several versions of this part available, which might look slightly different. The version shipped after April 2024 is slightly taller to comply with ESD regulations.
⬢MMU Electronics - Control Board (1x)
⬢M3n nuts (3x)
⬢M3x6 screws (3x)
⬢Insert the three M3n nuts into the marked openings on top of the electronics cover. Push them all the way in.
⬢Slide in the Control board into the cover. Note the three buttons in the front have to go in first.
To prevent electrostatic discharge (ESD) damage, handle the board by its sides during manipulation. Avoid touching the chips, capacitors, and other electronic components.
⬢Fix the board in place with three M3x6 screws.
Be careful not to damage any of the small components on the board.
⬢For the following steps, please prepare:
⬢MMU / printer cable (1x) MK3S+ version is in the first picture.
Use the correct cable for your printer type e.g. MK3S+ or MK3.5 / MK3.9 / MK4
Note, this cable is different from the old MMU2S cables. Don't use the old cables.
⬢M3x18 screw (2x)
⬢M3nS nut (1x)
⬢PD-board addon (1x)
⬢PD-board-cover (1x) may not be included in some of the earlier MMU3 packages. If your MMU3 package or printed parts does not contain this item, you can proceed without it.
⬢This step is for those units that have the PD-board-cover in the package. If your package does not contain this part, skip this step.
⬢Slide the PD-board into the brackets on the PD-board-cover. Note the correct orintation of the parts.
Start sliding in at a slight angle.
⬢Plug the PD-board into the leftmost connectors on the electronics board. Gently push down on the PD-board.
⬢Attach the PD-board into the marked connectors on the electronics board so that it occupies the two connectors on the side of the control board
⬢The white connector on the PD-board is pointing inwards.
Make sure the PD-board is connected the exact same way as seen in the picture.
If you plug in the PD-board incorrectly, you will damage the electronics. Any damage caused to the printer due to an incorrect electronics assembly is not covered by warranty.
Don't connect or disconnect the cable if the printer is connected to the power outlet or is powered on.
⬢Connect the MMU/printer cable into the PD-board.
⬢Prepare the unit and the electronics board assembly as seen in the picture. Follow the cables to plug them in the correct order.
⬢MMU/Printer cable
⬢SuperFINDA sensor cable
⬢Pulley motor cable
⬢Selector motor cable
⬢Idler motor cable
Rule of thumb for the motor cables is; if you look from the back of the unit, the motor connectors are on the same sides as the motors, while the motor at the front (selector) occupies the middle connector.
⬢Insert the M3nS nut into the marked opening and press it all the way in.
⬢
Attach the electronics assembly to the MMU unit.
Make sure the side with the buttons is pointing to the front.
⬢Look at the back to see if the PD-board doesn't interfere with the cables. The cables should be guided over the PD-board, not beneath.
⬢Fix the electronics in place by two M3x18 screws.
Use the correct type of screws. In case you used longer ones, the unit might not work as expected.
⬢For the following steps, please prepare:
⬢Textile sleeve 5x450 (1x)
Note the MK3.5 / MK3.9 / MK4 cable comes with the textile sleeve already pre-installed.
⬢Zip-tie (4x)
⬢Ensure that the selector is fully moved to the left.
⬢Arrange the SuperFINDA cable so that it joins the motor cables on the side of the unit as seen in the picture.
Leave enough slack in the cable so that it doesn't bend too much with the selector reaching even the first filament position!
⬢Join the Selector motor cable with the SuperFINDA cable using a zip-tie in the marked position, as seen in the picture.
⬢Join the cables together with the Pulley motor cable in the marked position using a zip-tie.
⬢Wrap the MMU/Printer cable in the textile wrap if it isn’t wrapped already.
⬢Join the Idler motor cable with the MMU/Printer cable on the right side. Tuck any excess cable length under the electronics cover.
⬢Fix these cables to the marked attaching point on the ele-cover using a zip-tie.
Ensure there is enough slack in the cables so that the zip-tie does not pull by them when tightened.
⬢Leave as much slack as possible in the cable bundle between the motors and the electronics so the unit can be opened up later on without the risk of damaging the cables!
⬢Bundle the loose cables together using a zip tie.
⬢Frame holder (2x)
⬢Label-plate (1x)
⬢M3x10 screws (6x)
⬢M3nS nut (2x)
⬢Turn the unit around.
⬢Insert the two M3nS nuts into the marked openings on the side of the unit. Push the nuts all the way in using the 1.5mm Allen key.
⬢Add the frame holders onto the unit. Make sure the part with the hooks is on the selector side of the MMU.
⬢Fix the frame holders to the unit with four M3x10 screws.
⬢If the bolt doesn't go in easily, use the 1.5mm Allen key to adjust the nut position inside the Pulley body.
⬢Insert the label plate into the recess on the front of the frame holders.
⬢Fix the label plate in place using the two M3x10 screws.
⬢For the following steps, please prepare:
⬢PTFE tube 4x2.5x650 (5x) five of the ten long ones.
⬢Insert the five long PTFE tubes into the openings with the black collets on the back of the MMU unit.
From now on, if you need to remove the PTFE tube, push the black collet in, and pull the PTFE tube out.
⬢Undo the two idler tension screws and open up the unit.
Don't worry, the screws won't fall out.
⬢There are small windows next to each of the pulley positions. Verify the PTFE tube is fully inserted and its end is visible inside the window. If not, push the tube in some more.
⬢Close the unit and tighten the idler tension screws slightly.
⬢Adjust both of the idler tension screws so that the top of the screw head is slightly above the top surface of the idler-body.
This is the setting which works for the majority of materials. Some specific filaments might require a slightly different idler tension setting.
The correct idler tension is crucial and might require further adjustment on your MMU unit.
⬢With too low idler tension, the MMU unit might struggle with grabbing the filaments properly.
⬢With too high idler tension, the idler will struggle with determining its home position and the MMU unit won't work properly.
⬢For the following steps, please prepare:
⬢Serial number sticker (1x)
⬢Safety sticker (1x)
⬢Remove the safety sticker from the protective layer.
⬢
Apply the safety sticker onto the right side of the MMU3 unit. The correct position is depicted in the second picture.
⬢Apply the serial number sticker on the bottom of the MMU3 unit using the same method as before. Ensure that it is attached securely and aligned properly.
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