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Blob maker captured in time lapse  

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tdk408
(@tdk408)
Eminent Member
Blob maker captured in time lapse

A few months ago, I was suddenly plagued with giant print-killing blobs.  Finally, I completely replaced the hotend, using a genuine E3D hotend. I took great care to assemble it and install it according to the documentation provided by E3D and Prusa.  I used a new piece of PTFE tubing. I printed a 3 nm torque wrench specifically for this purpose, and precisely calibrated it to ensure it was genuinely 3 nm.

Yet, as you can see in the time-lapse video, my new hot end continues to ooze PETG filament.  Over the course of about an hour, you can see one big drip coming down near the heater wires, and also a smaller ooze down the front, and some on the nozzle.

I am a technical writer, so I am sure I followed the documentation to the letter. What the heck could I have done wrong? If I should not follow the directions, what should I do differently?

(On a side note, are there instructions for disassembling and cleaning a hotend in preparation for reassembly? I am concerned that bits of leftover stuck-on filament will goof up the reassembly.)

 

This topic was modified 1 month ago by tdk408
Posted : 19/06/2021 5:19 pm
jsw
 jsw
(@jsw)
Noble Member
RE: Blob maker captured in time lapse

I had to disassemble the hot end once to clear a jam.

I wire-brushed all of the scorched remnants off of the surfaces and 'chased out' the threads until they smoothly screwed and unscrewed, then assembled with the spacing shown in the diagram and torqued the nozzle.

Posted : 19/06/2021 5:29 pm
Tobbe
(@tobbe)
Active Member
RE: Blob maker captured in time lapse

A few things.

I assume you took apart the whole hotend including the heatbreak.
While assembling it, you screw in the nozzle the unscrew it a full turn, this part is very important, and then you screw in the heatbreak from the top.
And afterwards you must hot tighten the nozzle.

If your nozzle when screwed in stops right against the heater block you will have a leak between the nozzle and heatbreak inside the heater block and then when you print, because of the pressure molten plastic will ooze out.

This is easily overlooked and i've done this myself.

Posted : 19/06/2021 5:34 pm
tdk408
(@tdk408)
Eminent Member
Topic starter answered:
RE: Blob maker captured in time lapse

@tobbe

No, I unscrewed the nozzle one revolution, as described in the instructions. 

But! I think I just solved it, and you were super close. While shopping Amazon for 0.20 nozzles, I made an interesting discovery. The replacement nozzles I got with the new hot end are not the same size as the E3D original.  I just never noticed. Have a look at the attached comparison. There must be a 1.5 mm difference, plenty enough to explain the filament leak.

So it looks like the problem is, I assembled the hot end with the longer stock E3D nozzle, and later switched it for a generic nozzle with a much shorter threaded part.  Man, I'm mad at myself for not noticing! (It just never thought there would be such a big difference in a part listed as compatible with the MK3S.)

(Yes, these shorter nozzles could be compatible with the MK3S, if I had assembled the hot end with one in the first place.  I'm a little irritated that the seller didn't mention this problem when listing them as MK3S compatible.)

Posted : 20/06/2021 7:18 am
tdk408
(@tdk408)
Eminent Member
Topic starter answered:
RE: Blob maker captured in time lapse

A better solution is to throw away the nozzles that don't fit, and buy another set of nozzles that are confirmed to fit the MK3S without tearing down the hotend.

These nozzles are confirmed by a buyer to fit the MK3S, contain 24 nozzles in a variety of sizes from 0.2mm to 1.0mm.

https://www.amazon.com/Nozzles-BigcaseTech-Extruder-Filament-Spanners/dp/B08861N5RQ

Cheap, quick, easy.

Posted : 20/06/2021 2:56 pm
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