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cabbage63
(@cabbage63)
New Member
extruder body replacement

new owner and the extruder body needs to be replaced. The M3nS nut holding the superpinda probe is stripped in its slot and spinning making it impossible to tighten or release the probe for adjustment. Prusa was kind enough to replace the extruder body (will receive next week), my question is : Am I able replace the body without fully disassembling  the whole printer? Can I replace this part in place on the printer? The printer is fully assembled and functioning as far as the self test goes and XYZ calibration goes, I was adjusting my (first print) first layer and needed to make an adjustment. I went to loosen the superpinda and the nut just spun in its slot, now it will not come out. After chatting with tech support they determined warranty replacement was in order for the extruder body. The question remains, can the extruder body replaced on the printer and could anyone point me in the right direction if there are any specific disassembly instructions? This part of the assembly was indeed the hardest and now I get to do it again. Many thanks to anyone who can respond and offer some assistance to me to make this part replacement easier on my stress levels, thanks again

Posted : 15/06/2022 9:19 pm
Diem
 Diem
(@diem)
Famed Member

You will find all the information you need listed here,  'though you will need to dip into two or three articles:

https://help.prusa3d.com/tag/mk3s-2

Posted : 15/06/2022 9:33 pm
Si1verEag1e
(@si1vereag1e)
New Member
RE: extruder body replacement

Hello

I happened to do the same operation a few days back (after a more serious crash in which the probe broke off), and the procedure is actually pretty easy, (much easier than i thought, I was so happy when i finished, that i had to send a "thank you designers" mail to Prusa):

You won't need to cut any zip-ties, the X-carriage parts and the bearings will stay assembled and you basically need only one 2,5mm allen key. It helps to have the kit assembly manual ( https://help.prusa3d.com/guide/5-e-axis-assembly_169235) ready, just so you can check how the parts you're going to remove look on the inner side.

 

Don't get scared by the wall of text, i tried to describe it in detail:

  • First, i recommend moving the extruder to the middle of X-axis and about 20-30mm above the bed in Z. Then turn the printer off, disconnect the main power and let it cool down if it was heated...
  • Take a piece of clean cloth (old t-shirt or something similar) and cover the bed so you don't scratch it. (you can leave the steel sheet on, under the cloth, of course.)
  • Assume the printer is oriented with the LCD/control panel to you. You won't need much access from other sides.
  • Start removing all the stuff attached to the extruder - first both fans (unless you have some extruder rotation indicator, fan grilles or other user mods - these need to be taken off first). The fans can be wedged between the X-belt on both sides of the extruder (see a guide for nozzle replacement, if you aren't sure - it shows removal of the print fan. Because the extruder is so low, you might have issues with the print-fan's right screw, but you'll see the advantage later. You can also move the extruder down manually after you dismount the fan, turning both "Z" screws by hand at once - you'll need to do Z-calibration anyway.).
  • When both fans are dismounted and safely stowed in the belt,  remove the "Extruder-cover" part - there are two (very long) screw right under the E-motor (the "print fan support" is between them and you might need to wiggle it around to avoid the motor's cables.)
  • Remove the top cover ("FS-cover") and (carefully) the fillament sensor board. I left it plugged in and just kinda hanging by its cable - but you can disconnect it and stow it somewhere safe, if you prefer, it's quite delicate after all.
  • Loosen and remove the screw that tensions the "extruder idler" door (above where the left "extruder" fan used to be). Pull it out including its spring. 
  • Finally, remove the motor: there are two long screws in the upper corners, accessible from behind. (if you moved the extruder down as i advised, you should have easy access even thought the screws are facing away from you (don't forget that you need to turn the other way - clockwise, because they're facing away.
    Start with the one that also acts as an axis for the Idler door. Remove the Idler door as well.
  • Removing the left (last) screw, be very careful, as the motor will tend to fall of, and the Hotend probably as well. I unscrewed with my left hand, while the right one was holding the motor on. After it loosened, i grabbed the motor with my left hand (gently pull about 10-20mm directly to you, before you sway the motor away - because of the fillament sensor magnet) and laid it on the cloth-covered print bed (that's the main reason, why i advised to have the extruder so low - the cables are rather short and you don't want the heavy motor hanging on them). Your right hand can catch the Hotend and also lay it on the bed. (the cables are even shorter and delicate, but if you're not too violent, they should survive the hotend hanging on them for a short while.)
  • You're almost done: Two screws behind where the Hotend was are all that holds the Extruder-body on. Remove the P.I.N.D.A.  unscrew the sensor arm and carefuly pull the other magnet out, and mount them in the new part immediately. (take care about the magnets orientation, as shown in the assembly manual) Don't forget to also replace the "adapter printer" cube that houses the steel ball (don't let the ball roll away, it loves to get lost - there should be a spare one in the "spares" fastener pack if you have the kit. Also some spare magnets.) There are also some nuts in the Extruder body, refer to the manual.

 

  • Assemble in reverse order (make sure no cable get pinched between parts). You can take the opportunity to double-check the bondtech gear position on the motor axis.
  • Set the SuperP.I.N.D.A. position using a zip-tie as the last chapter in the assembly manual shows. ( https://help.prusa3d.com/guide/9-preflight-check_176167)

I hope it helped.

Once you have the printer up and running, it is a good idea to print spare parts (at least the extruder body, cover and motor-plate), just in case - these should be available to download ( https://www.printables.com/cs/model/57217-i3-mk3s-printable-parts) - Black PETG and the textured sheet are the default way, however I'm now printing the entire extruder in PC Blend Carbon for my machine.

Posted : 21/06/2022 12:59 pm
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