Y-splitter (new version) - QSM fittings and steel tubes are assembled in the factory. Use 8mm side of the wrench to tighten them. Y-splitter (older version) Extruder-adaptor-MM
  • Y-splitter (new version) - QSM fittings and steel tubes are assembled in the factory. Use 8mm side of the wrench to tighten them.

  • Y-splitter (older version)

  • Extruder-adaptor-MM

  • Starting August 2017, there is a small update to the design of P.I.N.D.A. probe holder, only one M3nS nut and one M3x10 is needed. See the second picture.

  • 3D printed parts are in the bag 2.MULTIPLEXER

FWIW - my kit did not come with the QSM fittings installed. So maybe that’s worth mentioning here?

Jamie Clay - Reply

Hi Jamie, fittings should be already assembled, I will investigate this.

Jakub Dolezal -

So I guess if you’re like me and do not have these installed yet, now is the time to do so.

Jamie Clay - Reply

In case the fitting are not installed already, please follow the manual. Now it is not the time to install them, as you need one more component.

Jakub Dolezal -

Sorry, this is confusing….

I don’t have the QSM-M5’s installed either and I do see them in the bag of step 3.

Do I take them out of that bag and install the now or do I just skip the QSM’s and place them in step 3…..??

Achim Boers - Reply

Hi Achim, this is strange. How old is the MMU upgrade kit? Anyway if you have the QSM-M5 fittings separately, please leave them for now and proceed according to the manual. You will install them later on.

Jakub Dolezal -

M3n nut (2x) M3nS nut (2x) Extruder-adaptor-MM (1x)
  • M3n nut (2x)

  • M3nS nut (2x)

  • Extruder-adaptor-MM (1x)

  • Insert M3n nut into the front part of Extruder-adaptor-MM all the way in.

  • Insert M3n nut into the rear part of Extruder-adaptor-MM all the way in.

  • Insert M3nS nuts into the side slots of Extruder-adaptor-MM all the way in.

  • Use nuts from MK2/MK2S extruder + take new ones from the bag 2.MULTIPLEXER

The side slots should be M3nS nuts, not M3n nuts, should they not?

William Karnesky - Reply

Hi, William, yes the side slots are for M3nS nuts. Thanks for the feedback.

Jakub Dolezal -

Go ahead and install the nuts from step 8 now as the nut traps are very tight. You might risk breaking a wire trying to get them after the extruder is installed.

Paul Betz - Reply

Thanks Man! I did this, I have found a few times while building the Prusa where it would be better do some things before other steps.

Jeff D -

One of my M3n nuts had no threads! Found a spare in the printer kit.

William Hughes - Reply

Just for clarity, there are two bags labeled 2. Multiplexer (one with printed parts, one with metal parts).

Fred Cunningham - Reply

M3nS nuts (2x) Insert M3nS into the P.I.N.D.A. mount.
  • M3nS nuts (2x)

  • Insert M3nS into the P.I.N.D.A. mount.

  • Check the proper alignment with 1.5mm Allen key.

  • Move the part carefully from now on, or the nuts will fall out.

If you didn’t read the comments from step 2 go ahead and install the nuts from step 8 now. The nut traps are very tight and you might risk breaking a wire if you wait until step 8 because the extruder will be installed by then.

Paul Betz - Reply

My Pinnda mount only has holes for one screw and nut on the 3d printed part, maybe its the latest version?

Travis Houry - Reply

Idem for me : only 1 hole

Prigent Jean-Marie -

Yes it was mentioned in a previous step, new versions only have 1 hole.

Mery -

Yes Travis, newest revision has only one screw. See the first step of this chapter ;)

Jakub Dolezal -

Cover the holes of the nuts with a small piece of tape after placing them so you can move it without them falling off. You can take it off later when you’re finished :)

Mery - Reply

Before you start, ensure you have both nuts in the Extruder cover (from previous assembly). Take extra CAUTION while moving with the Hotend cables!!! Place the new Multi Material Hotend into the Extruder-adaptor-MM.
  • Before you start, ensure you have both nuts in the Extruder cover (from previous assembly).

  • Take extra CAUTION while moving with the Hotend cables!!!

  • Place the new Multi Material Hotend into the Extruder-adaptor-MM.

  • Close the Hotend with the Extruder cover and tighten it by:

  • M3x25 (1x)

  • M3x18 (1x)

  • Ensure the Hotend cables are facing away from the P.I.N.D.A. mount.

  • The new Hotend is in the bag 2.MULTIPLEXER. Use the Extruder cover from MK2/MK2S.

Be very careful with the leads from the hotend, I would possibly remove the cable tie holding the heater cartridge leads in a bundle to remove extra strain on the wires going into the heater cartridge , I broke mine (the connection puled out of the cartridge) when moving the hotend around for the next steps, I'm having to wait for a spare to be delivered :-(

Raymond - Reply

Hi, Raymond, don't worry, I'm sure the package will arrive soon ;) Thanks for the feedback, warning added to the description.

Jakub Dolezal -

Having just build the MK2S, I really did not like the way that the wires from the heater cartridge and thermistor are bent at 90 degrees immediately after exiting the heater cartridge and thermistor. It looks so fragile with the strain being taken on this joint and is bad practice. I was taught during my electronics degree course not to bend wires at the component and instead leave a mm or so and to radius the bend. They are particularly at risk during the build stage and it is only reasonably supported once wrapped. I am hoping that they won't fail.

John -

Is there a difference between hotend from MK2S ... I am building a MK2S then proceeding to upgrade. Do I need to wire in MK2S hot end then remove - unwire and use hot end from upgrade? or Can I build the MK2s with the upgrade hot end thus removing some re-work?

Garth Olivier - Reply

Hi Garth, the hotend for MK2S and MK2S Multi Material is different. Build your MK2S, calibrate it, print some models and then upgrade to MK2S Multi Material. You won't save much time trying to combine parts together since you have to completely disassemble the Extruder anyway. So my recommendation is to follow the manual for MK2S kit and then to follow manual for MK2S Multi Material.

Jakub Dolezal -

My extruder cover piece cracked and has some heat/impact with print damage on the lip, I would recommend that Prusa not try to save money by having us reuse this piece from the Mk2s. I am going to try to super glue my piece to get it work, but will likely have to order a replacement part (my thermistor also broke so I couldn’t print a replacement part before disassembling). It just would have been a lot easier if you would provide a replacement part for this too, rather than rely on the part being in good shape after a bunch of printing.

Jason Hendeson - Reply

Before performing steps 4 through 8 I recommend you read the comments in Step 9 and perform a dry fit of the Extruder Adapter, Hot End, Y Splitter, and Y Splitter M3x30 bolt before doing Steps 4 through 8. If the Extruder Adapter, Hot End, Y Splitter, and M3x30 bolt due not mate well I recommend making the tube modification mentioned in Step 9 before performing steps 4 through 8.

norm cushing - Reply

hello - the fitting on the end of my E3d v6 hot end is different than that show here — can anyone advise what the fitting type is so i can avoid having to buy an entire new one??

Stephen Eacuello - Reply

Hi Stephen, I need to see pictures to help you more. Please start a thread in the “Answers” section, see the top of this page.

Jakub Dolezal -

M3x18 screws (4x) Take the smaller Left hotend fan and place it on the side of the Multiplexeru, tighten all 4 screws. M3x20 screws (2x)
  • M3x18 screws (4x)

  • Take the smaller Left hotend fan and place it on the side of the Multiplexeru, tighten all 4 screws.

  • M3x20 screws (2x)

  • Take the larger Front print fan and place it on the front of the Multiplexer, tighten both screws.

  • If you can't mount screws on the Front print fan, ensure there are nuts in the Extruder cover.

  • Use the Left hotend fan and the Front print fan from MK2/MK2S

For some reason I only had one M3x20 left from the MK2. The printer came assembled from Prusa. It seems you guys used an M3x18 screw for the front fan...? Luckily I had new M3x20 screws available. I would include screws just in case... They are cheap anyway.

Jose Miranda - Reply

Hi, Jose,

the Front print fan should be mounted using two M3x20 screws. I just check on a newly assembled printer. I suspect our worker accidentally used M3x18 during the assembly. I'm sorry about that.

Jakub Dolezal -

I suggest using additional washers to hold print fan (available in spare parts bag). Screw head is only just a little bigger than a hole in the print fan and it may break very easily.

Artur Filipiak - Reply

Hi Artur, thanks for the suggestion. However, using only screws is completely fine. You have to tighten carefully.

Jakub Dolezal -

Since you didn't specify that the fans and PINDA probe must be taken out, I left them connected to the controller board and it is easier like this. However, here you must specify that we must take care to correctly assemble these (the cables must remain between belt and rod).

m.Th. - Reply

Dear m.Th, there are two chapters for extruder disassembly and both imply to disconnect the electronics. However, you can leave the wires connected, but it might be more difficult to follow the manual later on. The proper cable arrangement is described starting step 11.

Jakub Dolezal -

Is better to insert the PINDA probe first because if the nuts aren't aligned you can fix them easily. If we put the print fan first, we cannot adjust the PINDA's nuts anymore (not enough space) if we realize that the screws don't fit.

m.Th. - Reply

That is a good point, only thing is the cable from the front print fan should go in the "L-shaped" holder first. I will try to adjust the manual.

Jakub Dolezal -

These pictures don’t show re-connecting the fan discharge deflector (labelled as ‘fan nozzle’ in the original instructions) on the Left hot-end fan, which seems necessary to me. You need to add that step and a photo back in. Refer to the extruder assembly instructions for the Mk2S.

Andrew W Grover - Reply

I meant front print fan, not left hot-end fan.

Andrew W Grover -

Hi Andrew, it is mentioned in the next chapter, step 20. However, you can do it now as well.

Jakub Dolezal -

The holes for the left fan were too small and the Multiplexer cracked near the hot end.

Daniel Segel - Reply

I agree the same thing just happened to me. I ordered a new extruder cover because my old one had cracked, I screwed the small fan and the upper right screw cracked the new extruder cover! It wasn’t in that tight - seems like the hole is just too small…

Jason Hendeson -

I too experienced a left Hotend fan screw (lower front facing screw), used from the original MK2S kit along with the original extruder cover, being about 1.5 to 2 mm too long. I removed it and ran a smaller diameter drill into the bottom of the hole to loose what I believed to be dislodged thread material from when the original unit was disassembled. I turned the unit over and gave a few taps and noticed a big of small plastic came out. The screw then seated properly. I did notice during disassembly these four screws required more force to turn for extraction than I expected. The extract force was most likely damaging the threads in the plastic.

norm cushing - Reply

Locate the P.I.N.D.A. probe and place it in the holder, proper position doesn't matter, we will calibrate it later. Take the cable from the front print fan and place it as shown in the picture. Twist the cable from the P.I.N.D.A. probe as shown in the picture. This will enable probe movement for future calibration.
  • Locate the P.I.N.D.A. probe and place it in the holder, proper position doesn't matter, we will calibrate it later.

  • Take the cable from the front print fan and place it as shown in the picture.

  • Twist the cable from the P.I.N.D.A. probe as shown in the picture. This will enable probe movement for future calibration.

  • Use P.I.N.D.A. probe from MK2/MK2S.

Guide 1A, Step 13, Leaves the Pinda Probe with a nut attached that sat into a recess in the old extruder body. It is not clear from the pictures in this step that it should have been removed and you can't see it clearly until Step 17 of this guide.

James Slater - Reply

Hi James, thanks for the feedback. Step 13 in 1A adjusted.

Jakub Dolezal -

My PINDA probe holder has only one screw hole location, not the 2 shown in the picture!

Ed Siegal - Reply

Hi Ed, please head back to the Step 1 and see all the pictures and description ;)

Jakub Dolezal -

M3x10 screws (2x)
  • M3x10 screws (2x)

  • M3nS nuts (2x) - already in the mount

  • Place the screws in the mount and tighten the probe gently, we will adjust the probe later and then tighten it fully.

  • If you can't tighten the screws, ensure you have both M3nS nuts in the mount.

The M3x10 screws do not reach deep enough to catch on the nuts. I've replaced them by M3x12 sized screws.

Placing the M3x10 screws from the outside of the assembly makes it evident that they are too short. Don't know why this is the case, maybe printing tolerances?

MartinMajewski - Reply

Hi, Martin,

M3x10 screws are long enough to reach the nuts, I suggest you follow the manual, otherwise, you might end up missing the correct screw length in one of the next steps.

Jakub Dolezal -

i also found that the m10 screws did not quite reach the mounting nuts. M12 did the trick. I wonder if this is a printing variation? Some of the bolt-head countersunk holes have slightly rough bottoms in many of the abs parts in my kit.

craig deforest - Reply

that's m3x10 and m3x12 of course...

craig deforest - Reply

Hi Craig, you should be always able to use M3x10 screws. It might be possible that the P.I.N.D.A. wasn't seated properly, therefore opening up the holder and in such case, the M3x10 can be "short".

Jakub Dolezal -

Also could not get the M10's to work so dug out some old M12s. Appears to be a design flaw in the countersunk holes - about 1mm too high on mine

Martin - Reply

Hi Martin, thanks for the feedback. I already discussed this with our designers, some adjustments are in progress.

Jakub Dolezal -

I found the M3-10 to be OK if you give it a bit of pressure while turning -- it will grab the nut and pull the clamp closed. However, if you later have to loosen the screw to adjust the PINDA, the screw comes free from the nut before the PINDA is adjustable. I prefer to use the M3-12 here so the screw can be loosened without coming free.

Robert Wallace - Reply

Agreed. I used the short arm of the hex key so that I could put more stable pressure. A half a turn later it was pretty much tight.

Justin Hopkins -

There is only 1 hole for Pinda NOT 2 in MMU kit I receive this week. Probably design has changed.

M10 is to short on first insert. Start with M12- screw it-then unscrew it - then put M10 back and it must be ok.

Prigent Jean-Marie - Reply

M3-10 is definitely not long enough. It barely catches the nut.

Daniel Segel - Reply

Hi Daniel, M3x10 should be enough, but in case you can't reach the nut, please use M3x12.

Jakub Dolezal -

I used an m3x10 screw and a half turn after getting it engaged it broke the pdna mount

Kenneth Buckingham - Reply

Hi Kenneth, in case you are unable to fix the probe in place, please contact our support to get replacement part or you can print it yourself, if you have another printer nearby: https://www.prusa3d.com/prusa-i3-printab...

Jakub Dolezal -

M3nS nuts (2x) Insert nuts in the traps, all the way in. Ensure  correct placement by the 1.5mm Allen key.
  • M3nS nuts (2x)

  • Insert nuts in the traps, all the way in.

  • Ensure correct placement by the 1.5mm Allen key.

Both square buts needed a really descent amount of force to be put in place - maybe those should be added at the beginning - its very hard with cable, fan and hotend installed to press them in.

Richard Rohan - Reply

Hi, Richard, did you check the correct placement with Allen key?

Jakub Dolezal -

I had also to heat the nuts up to get them into the traps. Those traps are very tight.

MartinMajewski - Reply

Hi, Martin, thanks for the feedback.

Jakub Dolezal -

Far too tight! I've tried heating the nut; ended up having to open the hole with a hot craft knife, even then still very tight!

Martin - Reply

Hi Martin, noted and will be discussed with the designer. Thanks for the feedback.

Jakub Dolezal -

Very, very tight - redesign please. Yes, I heated the nuts and a craft knife (thanks to the others!). Also I heated an Allen key to push the nuts inside. I melted a little the ABS around. By far the most difficult step, especially considering that we have to drag all the cables (including the hotend's ones) to complete this. Redesign please. Make bigger holes.

m.Th. - Reply

Dear m.Th., I will discuss this with the designer. The holes are tight because we want the nuts to stay in place during the whole assembly.

Jakub Dolezal -

Pushing the nut in really should be done at start. With all the sensitive pieces on you risk damage while you fiddle with this

Shawn - Reply

As others have said, the traps are very tight. This really should be in one of the earlier steps so you don’t risk breaking a wire while trying to get them in.

Paul Betz - Reply

This step really should be a part of step 2 or 3.

Paul Betz - Reply

I concur, the holes are tight and it’s better to place the nuts at an earlier stage to don’t damage anything. The issue about not losing the nuts while rotating the piece can be easily solved by placing a piece of tape on the hole to cover it after the nut is inserted, then it can be removed after screwing the corresponding part.

Mery - Reply

Oh and if you don’t have something to heat as previously stated, a small mallet and a thin file or screw driver do the trick! Push the nut gently with the mallet, then place the point of the file/ flat screw driver touching the nut and hit its opposite side with the mallet until it’s at the correct position. If you push it too much, just move it to the correct place inserting a thin allen key in the hole and push it upwards. It doesn’t need any force.

Mery - Reply

As of when I got mine, my nuts do not have the same problem as the rest of these people have been describing, so it must have been fixed.

Nicholas Vellenga - Reply

Slide the Y-splitter into the Extruder-adaptor-MM as shown in the pictures. Screw the M3x30 screw to secure the Y-splitter in place. If you can't tighten the screw, return to the previous step and ensure the correct position of the M3nS nut.
  • Slide the Y-splitter into the Extruder-adaptor-MM as shown in the pictures.

  • Screw the M3x30 screw to secure the Y-splitter in place.

  • If you can't tighten the screw, return to the previous step and ensure the correct position of the M3nS nut.

  • In case the Y-splitter isn't fitting, please check the PTFE tube in hotend has the correct length: How to trim PTFE tube - Multi Material

The splitter will not seat all the way down. There is a gap at the bottom of about 1mm. I checked all the parts for burs, etc and it looks like the PTFE tubing is a little too long and is bottoming out in the recess for it. What do you recommend to do?

Michael Hackney - Reply

I removed the PTFE tube and the Y splitter fits perfectly without it. So it is the PTFE that is too long. I ensured that it was seated all the way. I also inserted the PTFE in the Y splitter and attempted to assemble it and it still bottoms out.

I see that the PTFE is tapered at the lower end and countersunk at the upper end. Would it be better to trim the tube (probably the lower tapered end) or bore the recess in the Y splitter 1 mm? (I am skilled and have a complete machine shop so I know how to do this, just looking for best recommendation).

Michael Hackney - Reply

I also had a lot of debris inside the splitter adaptor. This should be removed bevor assembly - or the Prusa team should perform some quality check before shipping.

MartinMajewski - Reply

Same problem here. The splitter will not sit all the way down. I would aveto apply a lot of force to push it down. It does not feel safe...

Jose Miranda - Reply

I had to use an 11/64 in. drill bit to carve a little bit of material (about 1/16 in. or less) in order for this part to fit.

Jose Miranda - Reply

I too had problems mounting the splitter but don't think interference is with the tube. Think the problem is with the mating of the splitter at the bottom with the extruder adaptor housing. Barely able to assemble but did so and didn't worry about it at the time.

Then, during first calibration printing, the filament jammed in the nozzle. Rather than disassemble the entire extruder adapter, I removed the splitter (with difficulty) and cut the filament. Past experience with the MK2 says that after removing the nozzle (when hot), I could push the small piece of filament through enough to clear out the hot end. Then, replace the nozzle and go.

To prevent the hot end from turning while removing the nozzle, I "wedged" a thin, 1/8" aluminum, strip between the hot end and the plastic fan housing. Of course, you need to be quick or risk melting the fan housing. The space between the hot end and fan housing is less for the new extrude adapter so I'll need to find a thinner strip of metal.

Gary Linn - Reply

I am also having issues with this step. My PTFE tube was 41.85mm in length. Chat support had me cut it down to 41mm, but that still wasn't enough to get the screw holes to line up. The only issue was that after trimming it down to size, I was unable to reproduce the internal taper without creating a mess at the top of the tube.

I am now waiting on a replacement tube from Prusa.

James Slater - Reply

After a second look, There is a spare PFTE tube in the bag and it is the same size as the original. I have twice now had square nuts strip out of their holders in the Extruder Assembly. The first was the nut for the Splitter and the second was just now the one at the top corner for connecting to the X-Axis. I'm starting to think the New extruder is out of tolerances.

James Slater - Reply

I also had problems here. There were rough burrs inside the printed abs adaptor. I took these out with a drill bit and the assembly was ok. Prusa needs to allow more clearance or improve their print quality control.

craig deforest - Reply

@sublimelayers @martinmajewski @josemiranda @gary @geneticus @drzowie Guys, thank you for the feedback. We are on it, for future shipments it is solved already. For you I will create a step-by-step manual, so all the parts fit in nicely ;)

Jakub Dolezal - Reply

Really bad fit, doesn't butt-down to the base. had to use drill bit to allow extra room.

Martin - Reply

Same problem. Advice please.

m.Th. - Reply

Nevermind. Contacted the support and they told me to cut the PTFE tube. Cut it. Let's see if it works.

m.Th. - Reply

I read the comments but still don't have an answer. Surely support would see this to save lots of people contacting support for the suggestion of cutting the tube shorter ?

Greg - Reply

I measured the depth of the hole in the y splitter (where the PTFE tube goes) and for me it was 4.2mm. I made sure I had less than 4.2mm of tubing coming out of the nozzle and that solved the problem. Due to tolerances your measurements may vary, so make sure you measure yourself before cutting!

Joe Fiorini - Reply

Dude, thanks for this. I was going crazy trying to figure this out until your comment.

Shawn -

The pfte tube was 2-3mm to long. Seems from comment thread several people are having this issue

Shawn -

Hi guys,

in case the tube is too long to fit in the Y-splitter part, please follow this guide to trim it. Read all the instructions twice and if there are any questions please ask first before trimming the tube.

How to trim PTFE tube - Multi Material

@splitscreen55 @mth @greg @joefiorini

Jakub Dolezal - Reply

This article was helpful, but it says the length is 41mm????

Also needs a verification step to verify your boring is correct

Shawn -

Hi Shawn (@nextproject), yes 41 mm is the correct length.

Jakub Dolezal -

It is great that the Troubleshooting article was written for this. i didn’t realize this was an issue until after I trimmed the round end of the PTFE tube and finished the assembly.

It may be helpful to add a link to the troubleshooting article, on this step, if it doesn’t fit well. There is only a note on this step if the nut is improperly seated, possibly making people think they installed something wrong.

Brent W -

Not only was the tube too long but the large shoulder on the Y-splitter was preventing the holes from lining up. I had to trim more then a mm from the shoulder and cut the tube down to 39mm.

William Hughes - Reply

Mine won’t fit either. I took the tube out and it’s 41mm. I measured the tube sticking out of the nozzle and it measures 6.24mm from the black ring to the tip. Does this sound about right ? Somebody had posted above they had 4.2mm. If I only had 4.2 life would be good !

Dave Cook - Reply

Hi Dave, are you sure the tube is fully seated inside the hotend? Lift up the black ring and push the tube down.

Jakub Dolezal -

Yes, I lifted the ring, and pushed until my finger turned blue. Still sticks out 6.1 to 6.2 mm from the black ring.

Dave Cook - Reply

This would be a lot easier to do earlier, before the fans and PINDA probe are attached with wires hanging all over the place.

Daniel Segel - Reply

Hi Daniel, you can arrange the cables as in the picture, put them together and carefully twist them few times.

Jakub Dolezal -

I had to sand the bottom part of the Y splitter (not the part near the hot end, the one halfway down) in order for it to fit, and cut a small part of the tube. Even without the tube the holes didn’t line up and it was impossible to put a screw in.

Joris Mans - Reply

I had to sand the bottom part of the y splitter to make it fit, and cut a small part of the tube. The sanding was done not on the part that touches the hot end, but on the bottom part halfway down. Even without the tube the y splitter wouldn’t fit as the holes didn’t line up

Joris Mans - Reply

Before you shorten the PTFE tube make sure the rounded end is adequately round (see the How to trim PTFE tube - Multi Material). My tube’s rounded end was not very round and that may have been a contributor to the problem. If you cut the tube, the material is very soft and cuts very easily with a new razor or utility knife blade. Almost no downward pressure needed.

norm cushing - Reply

To remove the PTFE tube the black collar must be pushed down to remove the clamping force on the tube. Now the tube can be removed by pulling it up.

norm cushing - Reply

My tube measured 41mm. The tube hole in the hotend is approximately 34.5 mm deep as measured from the top of the black collar when the collar is all the way down. No debris in that hole. When installed the tube sticks up above the black collar approximately 7.5 mm. The holes in the Y Adaptor and Extruder Adaptor are not perfectly aligned approximately 1mm. So, either the Hotend hole is too shallow, or the tube hole in the Y adaptor is too shallow, or the tube is too long, or the tube’s rounded end is not round enough, or all of these items are out of spec. After trimming to 40mm the system assembled without being much of a problem other than the bolt threads catching very early stopping it from slipping through to the nut and needed to be turned all the way.

norm cushing - Reply

I cut 2 mm off of the PTFE, fits perfectly.

Michael G. - Reply

For me - it’s both - the “shelf” part way down the Y-splitter preventing full mating as well as the PTFE tube. I removed the PTFE tube and still had a 0.5-1mm gap. Looks like a slight bulge at the corners, but beyond that, it appears that the shelf extends too far “down” by the amount of the gap. A little work with a file resolved that issue, but then installing with the PTFE tube in place still had a gap about the same size. Original length of tube is 40.85mm, removed about 0.5mm.

Mark P Ottensmeyer - Reply

When the length and shape of this part (PTFE tube) is so important, one wonders why you do not make it fit perfectly from the factory or provide a proper tool in the kit to make / adjust it right

Morten H Pedersen - Reply

Hi Morten, trimming shouldn't be part of the assembly. Tube provided by us was designed to fit. Would mind sharing, when you've purchased the MMU kit? This should be already solved.

Jakub Dolezal -

Hmmm, I am not happy about this part. Until now, the assembly was smooth and as usual, I was impressed. Just finished to cut the tube and to drill the widening. I have no clue if the feeder will be able to reliably replace the filament.

Of course I checked the “trimming recommendations”, but please explain to me how to remove the white tube before showing how to cut/and drill? And at the same time PRUSA is denying any responsibility if anything goes bunkers? Come on - we had to pay 329 EURO for this extension and then - at one of the most critical steps in this assembly, the bloody tube is too long and requires trimming.

Harald Horn - Reply

Hi Harald, I'm sorry to hear the tube doesn't fit. Developers addressed the issue and I will alert them it occurred again. To remove the tube, please push the black ring on the top of the hotend, then you can remove the tube. When returning the tube, make sure you press the tube down, while moving this ring back up. In case the tube is longer and needs trimming, please follow the instructions provided and if the trimming goes wrong, contact our support, we will do our best to sort it out ;)

Jakub Dolezal -

Thanks Jakob, now I managed to remove the tube. Thanks for that - maybe some info you can add into the manuals under “Tipps and Tricks”?

So, after successful removal I decided to replace the tube with the spare one I found in the bag (which measured 41.07mm) and I reassembled the print head with the splitter. Will test tomorrow and will get back with feedback.

BR, H

Harald Horn - Reply

Hi Harald, I have in preparation full guide on complete hotend disassembly (include tips and tricks), but still working on it. For assembly this shouldn't be necessary, it should be just about assembling parts together.

Jakub Dolezal -

Just for completeness - by now I have managed to print single color items as well as 3 color items, using 3 extruders. I am still breaking in extruder number 4 and will go for the 4 color model soon. In parallel I have tried to work with soluble filament, but this is just not working yet. All in all I can say: Multimaterial printing is working, though the first steps were not as straight forward as one might expect, reading through the marketing information.

Harald Horn - Reply

This step was some B.S. I messed up the extra tube, which was actually bigger than the one already in there, so what I did was force press it real tight and had my brother screw it, luckily with brute force the screw was able to make it through, hopefully it works. They expect me to just have a 60 degree conical bit lying around. I ordered my kit 3/2018 and it still aint fixed.

Jeff D - Reply

Steel tubes 25x3x1.9 mm (4x) Push the tubes all the way into the Y-splitter as shown in the picture. Don't use an excessive force.
  • Steel tubes 25x3x1.9 mm (4x)

  • Push the tubes all the way into the Y-splitter as shown in the picture. Don't use an excessive force.

  • The 25x3x1.9t tubes are in the bag 2.MULTIPLEXER

One of the steel tubes was very far off center. I removed it with a 1mm ball head Allen wrench and looked in the bore. There was plastic burs from the heat set insert that were interfering. I carefully cleaned them out with a SHARP X-acto knife.

Michael Hackney - Reply

Hi Michael, thanks for the feedback. Plastic burs should be removed by my colleagues before shipping, I will let them know.

Jakub Dolezal -

This step took me a very long time to finish due to burrs that needs to be cleared inside the holes. I actually had to do this step before mounting the Y-splitter (Step 9) to ensure that PTFE tube is clear from plastic pieces from the burrs that I cleared while inserting the tube.

Ruchie Custan - Reply

None of my tubes were centered in the holes due to burrs. I’m not sure how to the inserts so I can remove the burrs. I installed the bowden tube connectors and put a piece of filament in each hole to check if makes it down to the heat block. It doesn’t go down as smooth as I would like but it does make it all the way down. Hopefully I won’t run into problems later on while printing because of it.

Paul Betz - Reply

I couldn’t find any steel tubes in any of my packages. However I did locate teflon tubes that are exact same sizes. Should I use these instead?

Drew Kang - Reply

The metal tubes should be in the bag 2 marked Multiplexer. Do not use the PTFE tubes yet.

Paul Betz -

Hi Drew, the steel tubes are used for cooling down the filament at certain shape, you can't replace them with PTFE tubes. In case you are missing them in your upgrade kit, please contact our support.

Jakub Dolezal -

note there are actually TWO bags labelled “multiplexer”. The small one, and the large one. My tubes were in the large bag.

Joe Burdge -

I suggest putting the bowden tube fittings on now to keep the metal tubes in so you don’t lose one later. Just screw them down hand tight for now.

Paul Betz - Reply

Good idea. Thank you.

Paul Hornbrook -

Hi,

Since this is open source, would you be so kind to help me / us to find the OD 3mm / 1.9 ID steel tubing, have spendt a day now without finding it, dont have time to way for you to have it in stock again so building my own , have everything now except those steel tubes :/

Thanks

Morten

Morten - Reply

Hi Morten,

please contact our support. Depending on our stock we might be able to ship them to you, or if they are not available, please ask for the supplier.

Jakub Dolezal -

Hi

I too am having troubles with the tube self centering. Looking at the data the hole on the y-splitter starts at approx 4mm then tapers down. The steel tube is 3mm. Is this clearance required for the cooling aspect of the tubes? Is there anything else that helps with making the tubes concentric to the QSM-M5 fittings. When I have fully tightened the fittings you can see the tube is not contcentric, with part of the tube hole mask by the QSM-M5 fittings.

Kind Regards

Simon

Simon - Reply

Hi Simon,

the non-centric placement is there by design. You need the system to be a bit loose in case of some filament and structural imperfections. Anyway as soon as the filament enters the tube, it will centre itself.

Jakub Dolezal -

My tubes are off-center at the top as well, but I didn’t look for burrs before putting them in, and they seem like it would be hard to get them out now without damaging them. Do they need to be centered? It felt like they were all bottoming out properly, so I assume the bottom end is in the proper place.

Daniel Segel - Reply

Dan, The comment just above yours say they will self-center when the filament enters. If you need/want to take them out, just push a piece of filament in them, then pull them out.

Dave Cook - Reply

I didn’t receive any steel tubes in my kit. The bag that is supposed to contain them contains the steel tubes image on the packaging but there is a white sticker over that image, as to mark that they should not be included. I didn’t see them in any other bag. What’s up with that?

Joris Mans - Reply

I didn’t get any steel tubes. Moreover my Y splitter looks completely different. It has these blue extensions sticking out of it. Those steel tubes aren’t on the image on the bag either. Well, technically they are but someone put a white sticker over them. I guess this is some kind of upgrade?

Joris Mans - Reply

Hi Joris, it is written in the first step of this chapter. We changed the manufacturing process in our factory and the Y-splitter comes with steel tubes inside and Festo fittings assembled.

Jakub Dolezal -

The tubes just dropped right in. The fall out if I turn the Y-Splitter upside down. I seems like there should be something inside the splitter to keep them in place. In the picture there are little rings inside the splitter. I think my Splitter did not come with those rings.

Charles - Reply

Hi Charles, can you please share pictures in the Answers section? (http://manual.prusa3d.com/Answers) Thank you

Jakub Dolezal -

hello! were the specifications of the steel tubes ever made open to the public? I am also interested in ordering additional spares if possible as well as the brass fitting inserts for the y splitter.. cheers!!

Stephen Eacuello - Reply

These steel tubes are a real pain :-( Is there any reaseon why they flip around in the multiplexer? None of my tubes is centered and even if I take some filament during monting… as soon as i take the filament out they snap to the side. (no burrs which I could see)

First time I didn’t recognice it and as I wanted to do the first layer calibration, the filament cound’t be loaded.

Even if gently trying to unmount the tube connectors, my Z gets misaligned and I have to go through the whole double calibration process again.

Why is this part designed so difficult? :-(

Anyone any tips how I can center the tubes? Shall I cut some thinner cable tie bits and stuff them in to stop the tubes wiggle around?

Alexander Fazekas - Reply

ATTENTION, follow the instructions properly. Correct position of the cables from the Multiplexer is crucial!
  • ATTENTION, follow the instructions properly. Correct position of the cables from the Multiplexer is crucial!

  • Begin by placing the Multiplexer like shown in the picture (the Front print fan facing the heatbed).

  • First step: Lead the cables from the hotend through the aluminium frame and below the X-axis!

Previous steps did not direct to remove the PINDA or the two fan cables from the controller board.

James Slater - Reply

Hi James, depending on your printer you either had to follow chapter 1A or 1B and both mention the disconnection of wiring from Extruder.

Jakub Dolezal -

At the time of writing, there isn't a concrete step guiding us (at least in the chapter 1B) showing us if it is needed to plug the wires from the controller board and how to plug these out. Reaching here, we figure that these must indeed taken out. Or perhaps I am missing something?

m.Th. - Reply

Dear m.Th. please see the 1B step 4, where is described to be careful while unplugging the cables. I will try to rewrite the sentence so it is more direct.

Jakub Dolezal -

BTW, if we do not pull out the hotend fan, the print fan and the P.I.N.D.A. probe from the controller board, the reassembly is easier. Just that you need to rewrite some steps.

m.Th. - Reply

If you don't disconnect all the cables, then you have to disassemble the extruder close to the printer, which might be inconvenient and you can also break the cable or the connector. This is why we are taking the safest path.

Jakub Dolezal -

Second step: Take cables from the P.I.N.D.A. probe and the print fan and place them between  the lower smooth rod and belt on the X-axis!
  • Second step: Take cables from the P.I.N.D.A. probe and the print fan and place them between the lower smooth rod and belt on the X-axis!

This step isn't necessary if we leave the PINDA and print fan plugged into controller board.

m.Th. - Reply

Please see my comment for step 11.

Jakub Dolezal -

Third step: Take the cable from the Left hotend fan and place it between the lower smooth rod and the belt on the X-axis!
  • Third step: Take the cable from the Left hotend fan and place it between the lower smooth rod and the belt on the X-axis!

This step isn't necessary if we leave the hotend fan plugged into controller board.

m.Th. - Reply

Please see my comment for step 11.

Jakub Dolezal -

Prepare following screws for mounting the extruder: M3x10 screw
  • Prepare following screws for mounting the extruder:

  • M3x10 screw

  • M3x30 screw

  • M3x18 screw

  • Tighten the screws to secure the extruder in place.

  • Note the cable arrangement as highlighted in the picture. The P.I.N.D.A and print fan cables have to go together through left slot. The Left Hotend fan cable has to go through the right one. Hotend (nozzle) cables have their slot below the nylon.

The Note marked with red isn't necessary if we have the fans and PINDA plugged in from the beginning.

m.Th. - Reply

Please see my comment for step 11.

Jakub Dolezal -

Correction: just say about hotend (nozzle) cables.

m.Th. - Reply

There were no M3x18 or M3x30 screws in the kit or this step, so I assumed I was meant to use the screws they came out of the old extruder. I just tried reusing the old screws in the position they came out of when I dissassembled the old part. On trying to fit them however it became clear that what I thought was the M3x18 screw was too long. But only after I split the Extruder-adaptor-MM. so now I have a broken part and no screws to fit! What can I do?

Darren Wallace - Reply

I found a M3x18 screw in the 9/1 SPARE bag from the MK2s kit.

Panayiotis -

I did exactly the same thing - trying to work out now if I can get it to temporarily work in order to print a new part. Looks like I might have to reassemble the original to print the new part and start again

Ken Spence -

Thumbs up on the tip on where to find the M3x18 !!

Bill Nicely -

Prusa Support were great, sent me a new part and some spare screws

Darren Wallace - Reply

Hi Darren, thanks for the feedback. Satisfied customer is our top priority! ;)

Jakub Dolezal -

If you have the MK2S printer, you can skip this step and continue with the next.
  • If you have the MK2S printer, you can skip this step and continue with the next.

  • If you have the MK2 printer, follow the these chapters:

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Slide the zip tie through the left X-carriage slot as shown in the picture. Guide the zip tie under the hotend cables. Make sure that all the cables are in the correct position. The P.I.N.D.A. probe and Front print fan cables have to go in the left slot and under the zip tie. The Left hotend fan cable has to go in the right slot and under the zip tie. The hotend cables have to go in the bottom slot and have to be inside the zip tie loop.
  • Slide the zip tie through the left X-carriage slot as shown in the picture.

  • Guide the zip tie under the hotend cables.

  • Make sure that all the cables are in the correct position. The P.I.N.D.A. probe and Front print fan cables have to go in the left slot and under the zip tie. The Left hotend fan cable has to go in the right slot and under the zip tie. The hotend cables have to go in the bottom slot and have to be inside the zip tie loop.

  • Tighten the zip tie and cut the remaining part.

The pictures shows wires to the right of the black support, when I built the MK2S I had wires on this side and they hit the RAMBO case preventing the X-axis limit switch from triggering. I would suggest routing ALL wires to the LEFT (looking from the back).

John - Reply

It looks like the zip tie here is inserted in the opposite direction to the equivalent step in the mk2s assembly instructions.

Ben Gruver - Reply

Hi Ben, yes you are right, there is a difference and sorry for the inconsistency. However, more important is to have the cables in the correct arrangement.

Jakub Dolezal -

Wrap the spiral wrap around the cables to have one turn of wrap on cables, but without the lower Hotend cables. Place two zip ties on the beginning of the spiral wrap and tighten them. Cut the remaining part. Continue by wrapping all the cables from the Multiplexer, all the way to the  end.
  • Wrap the spiral wrap around the cables to have one turn of wrap on cables, but without the lower Hotend cables.

  • Place two zip ties on the beginning of the spiral wrap and tighten them. Cut the remaining part.

  • Continue by wrapping all the cables from the Multiplexer, all the way to the end.

  • On the end of the wrap, take out the nylon and have at least two turns of the wrap. See the picture.

As noted above, ensure all wires are routed to the LEFT side of the black arm when looking at the back of the extruder and check that X-axis limit switch triggers before finalising the wrapping.

John - Reply

my nylon is prusa orange will this effect this step in any way?

Travis Houry - Reply

Hi Travis, nylon colour doesn't matter. Important is the material properties and those are the same ;)

Jakub Dolezal -

Guide the cables through the top of the Rambo cover. Ensure you have placed the nylon into the slot and the spiral wrap is going through the cover. Place a zip tie into the slot on the top of the Rambo cover and tighten it. Don't use an excessive force or you might damage the cables. Place a zip tie into the slot on the top of the Rambo cover and tighten it. Don't use an excessive force or you might damage the cables.
  • Guide the cables through the top of the Rambo cover. Ensure you have placed the nylon into the slot and the spiral wrap is going through the cover.

  • Place a zip tie into the slot on the top of the Rambo cover and tighten it. Don't use an excessive force or you might damage the cables.

It is easier to not take out the nylon cable in first place together with other cables (fan, PINDA etc.). See my other comments on this topic.

m.Th. - Reply

It might happen the nylon was pulled out during the disassembly, this step is here to ensure it is properly pushed in.

Jakub Dolezal -

I think this hole needs to be larger. I am unable to get the cables through this opening with the cable wrap on them.

Mike Finn - Reply

This is the worst part of the assembly so far, some guideance on how to insert the cables with the spiral through the hole would be helpful ;)

[EDIT]: turns out sheer force helps, bent the right sight of the top up and you can slip them in, but be extra extra careful.

Raphael - Reply

I also had difficulty with this step on first assembly last year. The hole needs to be a little bigger, or there needs to be some kind of clamp to hold the whole bundle instead of a zip tie.

Robert Klein - Reply

Hi Robert, thanks for the feedback, new design is being tested ;)

Jakub Dolezal -

Leave the cables unplugged for now, we will connect them later.
  • Leave the cables unplugged for now, we will connect them later.

  • Multiplexer is finished! Let's move on to the 3. Extruders assembly

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Jakub Dolezal

Member since: 02/20/2017

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6 Comments

I recommend doing step 8 before step 4. Step 8 might need some tough handling which is better to do before the hotend and its fragile cables. This tip is especially important if the M3nS (square) nuts are a tight fit.

Jonn-Idar Fjæra - Reply

My printer is a MK2 upgraded to a MK2s, but as it was too much faffing around to re-do all the electronics I still use the original MK2 Rambo case, so the pictures above do not match up ....

Julian Stone - Reply

While re-doing the configuration after everything was finished, I found that the PINDA probe clamping wasn't working & that the 10mm screws weren't long enough, Luckily I have some 12mm screws which work ok.

So either the supplied screws are too short (they measure 9.5mm) or the extrusion is wrong...

Julian Stone - Reply

Hi Julian, the PINDA probe holder is designed for use with 10mm screws. Ensure the PINDA probe is seated in properly and if you still can't reach the nuts, please use M3x12 screws. We will make some adjustments in the design, so the 10mm screw is always enough.

Jakub Dolezal -

What about the fan nozzle? There is no mention about it.

Andres Stang - Reply

Hi Andres, it is in the next chapter: 3. Extruders assembly

Jakub Dolezal -

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