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S5 Print Core Nozzle Replacement

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Posted · S5 Print Core Nozzle Replacement


Is it common and possible to need to replace the brass nozzle on the S5 print cores?  I don't see where you can buy them specifically for the S5 print core and wondering if this is needed after extended use.  If so does anyone know the part numbers I can only find ones marked for S2 online.  Thanks

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    Posted · S5 Print Core Nozzle Replacement

    To answer the first question:

    An Ultimaker print core is a consumable as a whole. It's not designed to repair single parts of it.


    It is - technically - possible of course, if you have the right tools and the patience. But not common, not at all.

    If the nozzle is worn out - replace the print core (as a whole) and you're done. That's the intended way.


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    Posted · S5 Print Core Nozzle Replacement

    I inherited some old print cores with this UM3X I am getting back into service.  One of the AA 0.4 was used to print something abrasive and is worn completely out.


    I had another order to place anyway and was below the min free shipping threshold, so decided to add some MicroSwiss UM3 PrintCore replacement nozzles.  I will attempt a swap once everything I need is in place.  My expectations are low but the core is otherise in good condition and the cost to try is low.


    @gr5 has an excellent video on disassembly, of course that core is pretty new and not encrusted in burned on filament.  I don't have George's technical knowledge or skill.  (Nor do I have a wonderful pooch to cheer me on, but I digress....) I do have a (home based) machine shop with some good micro vices and precision torque gauges, so hopefully will be able to muddle through.


    Areas that I expect trouble with are many:

    1) getting the nozzle thread to release without stripping anything (as tinkergnome correctly points out, it is not designed or promised to be unthreadable),

    2) protecting the steel heat break 'thin section' from getting any torque during disassembly and again during reassembly,

    3) not destroying the temp probe or heater which are probably more fragile than when they were new

    4) re-threading correctly to get a good seal with sufficient torque without breaking something.


    I expect at least part of this effort is going to require heating the block/tower and cooling the nozzle.  I don't think I will get too far with this on disassembly as everything is connected and the same material, however assuming I get everything apart without destruction, I'll use differential to get things as tight as I can without too much torque.


    I'll likely put the new nozzle in the freezer (or outside at -20!)  for a while, then warm the tower and block with a heated brass rod to about 45C or so - I don't want to get things too hot for the print core plastic housing.  I am hoping that with a chilled nozzle and clean threads I'll get things to seat all the way and get a good seal.


    I don't know what to expect with the PFTE liner.  That might be a temporary show stopper if I find it worn out on disassembly.  Depending on how good my workholding is,  that consideration may or may not be relevant at that point 😉



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    Posted · S5 Print Core Nozzle Replacement

    As a possible alternative use for a worn nozzle, you could change the programming of it to match the new hole diameter, obviously depending how badly worn it is. For example, I had a AA 0.25 print core that had some abrasive filament through it and its now been re-programmed to a AA 0.8 to act as my prototype core and prints exactly the same as an original AA 0.8mm.

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    Posted · S5 Print Core Nozzle Replacement

    That's a good fallback!  What's your experience with autolevelling been?  I haven't compared the heights of the 0.8 and 0.25 nozzles and from the hardcores I've reprogrammed (another nod here to @gr5) the only code I would think to use in this case would be


    AA 0.8

    sendgcode M151 T0 A8 D7800000000004141
    sendgcode M151 T0 A16 D20302E3800000000


    Does that look familiar in your process?


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    Posted · S5 Print Core Nozzle Replacement

    Not sure about the sendgcode but everything else is correct. I just did mine via USB with the attached file.


    I haven't noticed any issues with the auto-levelling but that's not to say it might be slightly different per nozzle. Hopefully auto-levelling sorts this (When it works!).


    And indeed, hats off to @gr5 for the information!



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    Posted (edited) · S5 Print Core Nozzle Replacement

    So, what's better than one questionable plan?  Why, two!!


    I note that among the concerns with DIY disassembly and reassembly of a print core is the potential for a lower quality seal than original and hence leakage. 


    Given that there is a PFTE liner between the cooling tower and the nozzle, I'm wondering what the pros and cons would be of using teflon thread tape in the nozzle to cooling tower connection.  The stuff I have says it is stable to 280C and then slowly degrades as the temp approaches 400C so I think it would be safe, especially since the section I would use this on would be effectively sealed from the surrounding air.


    Note this is with regard to an OEM AA 0.4 print core that is going to trash otherwise. (Not as lucky with the 0.8 experiment, but that may be an option for the sister of this one...)




    Update per post below.  Thanks to some good mentoring I learned that the critical point for seal is above the threads, so there is no need to complicate this process with teflon tape.

    Edited by JohnInOttawa
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    Posted (edited) · S5 Print Core Nozzle Replacement

    Just an update.  This is a very loooong read.


    TLDR version - it is possible to install a new nozzle on a print core.  With caveats.


    Longer version.


    I am printing with the re-nozzled AA 0.4.  All printing aspects appear to be as expected, including active levelling, so I'm happy!


    One aspect that I will likely have to live with is that the body of the old print core had sagged in the area under the cooling fins, which made installation and removal a challenge in the #1 position before this effort began.  The new nozzle of course did not fix this.


    Briefly, here are my thoughts about taking on nozzle replacement on an OEM print core.

    Before starting


    1) The video from @gr5 is the place to start.  I suggest several plays of this resource before attempting anything.

    2) Things are far more predictable if you have a vice that can hold just the heat block while allowing you to put a wrench on the heat break nut and a socket on the nozzle.  The heat break nut cannot be allowed to move when removing the old nozzle or the heat break is done.



    Removal and cleaning

    3) The nozzle holds the heat break and heat block together.  Once the nozzle starts to loosen, continue to hold the heat break nut until it disengages from the nozzle.  You'll know once the nozzle has disengaged from the heat break.

    4) Unlike the video, a print core with a worn out nozzle has a lot of carbon and deposits in the threads of the heat block and heat break, as well as on the surface inside the heat break connection that the nozzle seats against.  In order not to risk the nozzle binding before it got fully seated, I cleaned the threads and that seating surface. 

    5) The heat block, heater and sensor will all be fairly caked with carbon and long melted filament.  You'll have to remove the heater and sensor anyway to reinstall the new nozzle, so this is a good opportunity to clean everything up so you get a good thermal connection.  In my case, I had to carefully clean the socket on the tiny cap screw that holds the heater and sensor in place before I could get an allen key in there.

    6) The top of the heat block in my case  almost looked like I had some pitting or metal transfer from the heat break to the block, but in the end, it was really just heavy tarnish.

    7) I took the opportunity to clean the heating block, especially the top where the heat break was going to thread on later. Again, the priority was to ensure nothing caused the torque to max out before the thread was fully seated.   When cleaning the brass, I decided not to use any sort of metal polish, as I did not relish that stuff off-gassing later.  Instead, I went with an old school method - ketchup.  Worked great.  I finished the last of the surface with a quick pass on wet 2000 grit automotive standpaper and lapping compound.  The goal was to remove residue with as little effect on the metal as possible.


    Installing the new nozzle

    8 )The nozzle thread passes through the heat block into the heat break.  Both the heat block and heat break are threaded.  This means that the only way to get a tight threaded connection all the way through is to first fully install the nozzle on the heat block, then install that assembly onto the heat break.  The key interface to prevent leakage is between the top of the nozzle threaded portion and the internal mating 'ring' inside the heat break, so I decided to fully thread the nozzle into the heat block to get as much thread past the heat block as I could.  Reference my post above, because of where the seal is, there is no value in teflon tape or otherwise sealing the threads. 


    9) A test fit of the new nozzle felt like it was binding a bit, so I decided to go with a two-step process of freezing the thread and heating the receiver.  So for the first connection, I froze the nozzle, and heated the heat block to 200C.  They went together without issue and the nozzle seated fully in the block as hoped. 


    10) I then froze this assembly while I heated up the heat break/cooling tower assembly, again to about 200C.  While it was heating, I got the print core body,  heat break wrench and nozzle socket wrench ready.


    11) The heat break and tower were fitted back into the print core body, the wrench held the heat break nut stable and I hand threaded the heat block /nozzle assembly on as far as I could, in order to feel for cross threading.  Torque was very low and I was able to feel when the thread reached a physical hard stop inside the heat break.


    12) Reassembly from this point on is exactly per the @gr5 video.  I had to pay special attention to the heater and sensor wires, they are quite stiff, and if you don't position them correctly, they'll push the nozzle forward and complicate loading and unloading the nozzle.


    Testing and final thoughts


    One final step, and again, shout out to @gr5, for the first print, I used white PLA and only ran it for a few minutes (less than 10).  I then stopped and checked for leaks.  Finding none, I lengthened the print run to 30 minutes. 


    The nozzle appears to work pretty well.  It's plated brass which is supposed to be more wear resistant, I guess we'll see. 


    While I'm happy to have salvaged a print core, as you can see, this is a time consuming thing to do.  I happened to have the tools to hold everything square, safely clean the brass components,  chase the threads without shaving metal and isolate the fragile neck from torque, so my direct cost was just the new nozzle.   I'll likely do this for the next core that wears out.  In the end, though, the achilles heel of the print core may be the plastic parts and not the hotend.  I don't yet have a fix for that.


    Thanks for sticking with the long version!




    Edited by JohnInOttawa
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