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Changing HotEnd  

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4 True Models
(@4-true-models)
Active Member
Changing HotEnd

Hello!

Please excuse me if this thread have been already talked about in the past. I'm new in the forums and didn't get to found nothing about my question...

Could you send some sort of instructions or manual in order to change the whole HotEnd with the fewer steps and in the most efficient way possible?
I've a Prusa i3 MK3 for a few weeks by now, although we are a workshop's team with plenty of 3D printing experience with a lot of other 3D printers such as Ultimaker or BCN3D Technologies ones.
This experience tell us to fully change the HotEnd of every 3D printer whenever you want to change the filament for one which works with a very different range of temperatures. The most classical case is switching between PLA and ABS. If you keep different HotEnds for different range temperatures you will see its life (and their nozzles) pretty much extended.

That is the reason why I'm asking about some sort of guidelines in order to change the HotEnd (no need to change the wires as you can put the heater and thermistor in the new one) for this awesome MK3 3D printer. I've fully assembled our MK3, and now that I'm willing to change the HotEnd I'm feeling it will be much more complicated than for other 3D printers, so I will be really grateful if the Prusa team help us with this and show us the best and easiest way to do so.

Thank you!

Postato : 02/09/2018 10:22 am
Chris
(@chris-50)
Eminent Member
Re: Changing HotEnd

The MK3 can print ABS without any physical changes, you simply select ABS for print material or set the print temperature in your slicer. There doesn't appear to be a more direct way to replace the hotend, you must take the extruder apart to remove the hotend.

Postato : 02/09/2018 10:41 pm
bobstro
(@bobstro)
Illustrious Member
Re: Changing HotEnd


[...] This experience tell us to fully change the HotEnd of every 3D printer whenever you want to change the filament for one which works with a very different range of temperatures. The most classical case is switching between PLA and ABS. If you keep different HotEnds for different range temperatures you will see its life (and their nozzles) pretty much extended.
Well, a full hotend swap would certainly work, but it's not necessary. The trick is to make sure you've fully cleaned the hotend of leftover filament when switching materials, particularly from high-temp (e.g. ABS) to low-temp (PLA). Try this process yourself and see if it meets your needs:

  • Raise Z to max.

  • Heat hotend to whatever temp the currently-loaded material prints at.

  • Eject the currently-loaded material.

  • Heat hotend to a temp higher than normal printing temps (e.g. 260C). The goal is to melt any material you might have used previously.

  • Load either ABS (white recommended) or cleaning filament. I personally use eSun cleaning filament and really like the results.

  • Let a good amount of material stream through to clean the hotend out. I usually answer "N" twice to the "is the filament loaded" question.

  • Reset the printer with the button below the knob on front.

  • Let the hotend cool off with your cleaning material still in the hotend.

  • While it's cooling, loosen the extruder tensioning screws on the left of the extruder housing.

  • Let the hotend cool to below 90C.

  • Set the temp to your next material temp.

  • Watch the hotend temp. When it gets up near 90, grab the cleaning filament with pliers and brace the extruder with your other hand. When it gets to 90C, pull firmly and steadily straight up. Don't jerk it, you want the filament to stretch and pull out without breaking. The material should be soft but not molten. This should have allowed any remaining material to loosen and mix with the cleaning filament. As you pull it up, it's warm enough to be slightly elastic, so should pop out. Inspect the removed filament and you should see the shape of the hotend interior. You may see loose bits of other filament that dislodged. If so, repeat this process. You may have to push cleaning filament through if extruder tension screws are still loose. (This is the "cold pull" procedure.)

  • Re-tighten the extruder tension screws to < 1mm above the cover. (I always forget this step.)

  • Heat the nozzle up to your next desired material temp.

  • Load your next material.
  • These steps will eliminate the need to do a full hotend swap just to switch materials. It's the same procedure when swapping nozzles out. The reason I really like the cleaning filament is that it will extrude at a wide range of temps, so if any is left in the hotend after the cold pulls, it'll melt out in the last step. I've been able to swap freely between PLA, PETG, NGEN, XT and a variety of carbon, wood, copper and other filled materials with no issues. My biggest extremes would be 3DXTech PETG that prints at 265C and PLA at 200C.

    My notes and disclaimers on 3D printing

    and miscellaneous other tech projects
    He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

    Postato : 02/09/2018 11:20 pm
    4 True Models
    (@4-true-models)
    Active Member
    Topic starter answered:
    Re: Changing HotEnd

    Hi there,

    Thank you for the answers...
    I already knew about that kind of procedures although I like most when you use some Nylon to fully clean the whole hotend, it seems to work better in our experience. However, the way the Prusa X-Carriage is built makes us to think the nylon-cleaning procedure will be dangerous and could damage the 3D printer.
    We also used cleaning filaments, our choice is the one from Smart Materials 3D, with pretty good results although not as good as with nylon.

    Anyway, thank you very much for the tips, we will try to make the cleaning procedure like you suggest and hopefully we won't suffer more clogs than usual regarding not changing the hotend. We would really love the Prusa MK3 design would be prepared to swap hotends more easily, maybe in the future their team will think about this, we think it would be a great feature.

    Thank you!

    Postato : 05/09/2018 11:11 am
    NarwhalBert
    (@narwhalbert)
    New Member
    Re: Changing HotEnd

    Hey,

    Just wanted to quickly reply since I found this post while searching for a way to get to the hotend. I am one of those poor souls that installed the hotend way to low and only realized the mistake when Z calibration kept failing. I found this video . You can basically take off both fans on the extruder and are then able to take of the front plate of the extruder assembly and access the hotend.

    Hope this helps.

    Postato : 03/10/2018 6:20 pm
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