4B. Upgrading the Nextruder (MMU3)

Relevant for:

MK4S MK3.9S

Last updated 7 days ago

Difficulty

Moderate

Steps

Available languages

Step 1 Tools necessary for this chapter

⬢For this chapter, please prepare:

⬢2.5mm Allen key

⬢Torx key T6

⬢Torx key T10/8

⬢Wrench 13-16

⬢Universal wrench

Step 2 Protecting the heatbed

It is HIGHLY RECOMMENDED to protect the heatbed.

⬢Use any cloth or piece of fabric, which is thick enough and cover the heatbed. This will ensure you won't damage (scratch) the surface during the disassembly.

Step 3 Uncovering the Nextruder

Some pictures may show three or four screws on the gearbox cover, but this does not affect the assembly process. You will be instructed if needed.

⬢Move the Nextruder approximately to the center of the X-axis to gain better access to the entire assembly.

⬢Remove the LoveBoard-cover by sliding it up.

⬢From the right side of the Nextruder, release and remove the M3x10 screw.

⬢Remove the LoveBoard-cover-right from the printer.

Step 4 Disconnecting the Nextruder cables

Note there are safety latches on each of the connectors which must be pushed in, in order to remove the connector.

⬢Disconnect all the small connectors from the left side of the LoveBoard.

⬢Disconnect the Nextruder motor (labeled E).

⬢Disconnect both cables from the right side of the Nextruder.

Step 5 Removing the print fan assembly

⬢Remove the M3x40 screw from the fan-door hinge.

⬢Pull the print fan assembly from the Nextruder.

⬢Remove all the cables from the cable channel.

Step 6 Removing the heatsink fan&hotend

⬢Release two M3x20 screws securing the heatsink fan and remove the fan from the Nextruder.

⬢Loosen both thumb screws.

⬢Pull out the hotend assembly from the Nextruder.

Step 7 Removing the Nextruder

⬢Loosen all three M3x10 screws mounting the Nextruder assembly.

When loosening the Nextruder, hold it with your hand to prevent it from falling.

⬢Remove the Nextruder assembly from the X-carriage.

⬢Put the printer aside for a moment and let's get on with Nextruder.

⬢Remove both thumb screws from the heatsink.

Do not discard any parts.

Step 8 Uncovering the gearbox

There are two variants of the gearbox cover, one with three screws and one with four screws. The procedure is the same for both.

WARNING: The following procedure must be carried out with extreme care and caution. No part of the gearbox itself should be removed.

If any part of the assembly becomes loose, please contact our customer support.

⬢Release and remove the screws securing the PG-case.

⬢When removing the screws, hold the PG-ring (gold-brass part) to prevent it from sliding out.

Some versions of the printer have three, some have four screws.

⬢Extremely carefully and slowly remove the PG-case from the Nextruder.

Prevent any dirt or debris from entering the gearbox.

Step 9 PG-case: parts preparation

⬢For the following steps, please prepare:

⬢PG-case (1x) new part

The older printed PG-case on MK4 required a washer on the inside. The new injection-molded MK4S version does not need the washer.

⬢M3x25 screw (3x) you removed earlier

Only in case you have the 4-screw Nextruder, you also need:

⬢Socket set screw M3x25 (1x)

Step 10 Installing the new PG-case

In case you have the 4 screw version of the nextruder:

⬢Install the set screw into the marked opening, running through the ring gear and the idler. Tighten it up fully.

⬢Place the new PG-case onto the gearbox.

⬢Secure it with three M3x25 screws. Do not tighten them completely at this moment.

The screws on the PG-case will be completely tightened during the self-test in the final chapter.

Step 11 Assembling the Nextruder: parts preparation

⬢For the following steps, please prepare:

⬢MK4S fan holder (1x)

⬢Heatsink spacer (1x)

⬢M3x12 screw (3x)

Do not reuse the M3x10 screws you removed earlier. Due to the new parts, longer M3x12 screws are now required.

Step 12 Assembling the Nextruder

⬢From the front side of the Nextruder (side with the printer logo pg-case), insert three M3x12 screws in the heatsink.

⬢From the opposite side of the Nextruder, fit the heatsink spacer onto the three screws.

⬢Make sure the protrusion protrudes towards you (like the screws).

⬢From the extruder motor side of the heatsink, attach the MK4S fan holder to the heatsink.

Avoid pinching the NTC thermistor cable. Guide it through the cutout as shown in the detail.

Step 13 Attaching the Nextruder

⬢Place the Nextruder assembly onto the spacers on the X-carriage. Line up the three screws with the three spacers.

⬢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 screws with the spacers on the X-carriage and join both parts together by tightening them. Start with the middle one.

Step 14 Connecting the NTC thermistor

⬢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.

Step 15 Assembling the hotend fan: parts preparation

⬢For the following steps, please prepare:

⬢Hotend fan (1x) you removed earlier

⬢M3x18 screw (2x) you removed earlier

Step 16 Assembling the hotend fan

⬢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 through the cutout in the fan holder.

⬢Guide the fan cable between the thumb screws under the cable channel up and connect it to the lower slot on the LoveBoard.

Step 17 Print fan blower: parts preparation

⬢For the following steps, please prepare:

⬢MK4S Print fan blower (1x)

⬢Fan-case (1x)

⬢Fan-case-cover (1x)

⬢Fan-shroud (1x)

⬢3x8sT screw (2x)

⬢M3x5rT screw (5x)

⬢M3nS nut (5x)

Step 18 Assembling the print fan case

⬢From the flat surface of the Fan-case, insert two M3nS nut all the way into the holes.

⬢Double-check from the side that the inserted nut is aligned with the hole in the part.

⬢From the opposite side, insert two M3nS nuts all the way into the holes. Check that nuts are fully inserted.

⬢Insert one M3nS nut into the hole in the Fan-shroud.

Step 19 Assembling the print fan blower

⬢Insert the MK4S print fan blower into the print fan blower case.

⬢Guide the print fan blower cable through the cable channel in the Fan-case.

⬢Close the fan with Fan-case-cover.

⬢Secure the cover with two 3x8sT screws.

The screws cut thread directly into the plastic, so there might be some resistance.

Step 20 Assembling the fan shroud

Attach the Fan-shroud to the print fan blower assembly. Notice two teeth on the fan shroud and two rectangular holes in the blower assembly.

⬢First, insert those teeth into the rectangular cutouts.

⬢Close the Fan-shroud and secure it with the M3x5rT screw.

Use reasonable force to avoid breaking the parts.

Step 21 Mounting the print fan blower assembly

⬢Take the print fan blower assembly and guide the fan cable through the cutout on the left side of the fan holder.

Use the same cutout through which the heatsink fan cable already guides.

⬢

Attach the print fan blower assembly so that the metal forks of the fan holder engage into the printed part.

⬢Ensure that the holes of both parts are aligned.

⬢From the left side of the fan holder, secure both parts together using two M3x5rT screws.

Step 22 Connecting the print fan blower

⬢From the right side of the fan holder, secure both parts together using two M3x5rT screws.

⬢Guide the print fan blower cable through the cable channel in the X-carriage and plug the connector to the middle slot on the LoveBoard.

Step 23 Prusa Nozzle info

There are two variants of the Prusa Nozzle that we ship with the printers:

⬢Prusa Nozzle brass CHT high flow (marked CHT)

⬢Prusa Nozzle brass (marked PR)

⬢For an MK4S, the Prusa Nozzle CHT is usually a default option. However, when using the MMU3, we recommend to continue using the standard Prusa Nozzle for optimal performance.

While it is possible to print with the Prusa Nozzle CHT, please note that specific settings are required to achieve high-quality multi-color prints.

⬢To replace the nozzle on the MK4S/MK3.9, please follow the instructions provided in the dedicated manual How to replace the Prusa Nozzle (MK4S/MK3.9S).

Step 24 Inserting the hotend assembly: parts preparation

⬢For the following steps, please prepare:

⬢Hotend assembly (1x) you removed earlier

⬢Thumb screw (2x) you removed earlier

Step 25 Inserting the hotend assembly

⬢Insert two thumb screws into the heatsink. Do not tighten them completely. Two turns are enough for now.

⬢Look closely at the underside of the heatsink and find the hole for the hotend assembly.

⬢Insert the hotend assembly tube in the hole and slide the whole thing into the heatsink.

⬢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!

⬢From the underside, check that the hotend is oriented correctly. It must fit between the cutouts in the X-carriage.

Step 26 Nozzle insertion check

⬢Verify that the nozzle is fully inserted. The copper ring on the nozzle should not be visible if it’s properly seated.

If not fully inserted, poor heat transfer may occur, potentially leading to issues like nozzle clogs.

⬢To adjust the nozzle position, loosen the thumbscrews, reposition the nozzle, and then retighten the screws, while pushing the hotend assembly up.

Step 27 Connecting the hotend cables

⬢Guide the hotend thermistor through the cable channel in the X-carriage and connect it to the LoveBoard.

⬢Guide the hotend heater through the cable channel in the X-carriage and connect it to the LoveBoard.

Step 28 Fan door cover: parts preparation

⬢For the following steps, please prepare:

⬢Fan-door-cover (1x)

⬢M3x30 screw (1x) you removed earlier

Step 29 Attaching the Fan-door-cover

⬢Attach the Fan-door-cover hinge to 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!

Step 30 Connecting the extruder cables

⬢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.

Step 31 LoveBoard: Wiring check

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

Step 32 Covering the LoveBoard: parts preparation

⬢For the following steps, please prepare:

⬢LoveBoard-cover (1x) new part

⬢LoveBoard-cover-right (1x) new part

⬢M3x10 screw (1x) you removed earlier

Step 33 Covering the LoveBoard: side cover

⬢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.