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Replacing PTFE coupler

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Hi

I am trying to replace the PTFE coupler as the old one is badly worn out. This is the first time I am doing it on a several months old printer.

Pulling things apart was easy but I have few questions regarding the assembly:

1. The element that screws into the head and that the PTFE coupler slides into is lose. I mean it is not even fingertight. Is this right? How tight should this be?

I cannot see any leaks of plastic between the head and this part.

2. There is about 1mm gap between the new PTFE coupler and the part it slides into. From memory there was no gap with the previous coupler (but I may not remember correctly). Is this OK?

Please help. The printer is in pieces and it makes me cry looking at it in this condition :-)

Thanks in advance.

 

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Sorry about the confusion. The official name of the part in question is "Hot end isolator", photo is for example here.

It was very lose when I pulled out the PTFE coupler, it needed 1-2 turns to be tightened. I am about to assemble everything back but I am not sure if hot end isolator should be so lose or if it should be tight (and how tight).

Ignore my question 2. The space is normal.

 

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...

1. The element that screws into the head and that the PTFE coupler slides into is lose. I mean it is not even fingertight. Is this right?

...

2. There is about 1mm gap between the new PTFE coupler and the part it slides into. From memory there was no gap with the previous coupler (but I may not remember correctly). Is this OK?

...

 

Both is correct AFAIK.

There are nice instructions and pictures in this thread.

 

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I was looking at FFKM / Kalrez before we ended up with the I2K (Polyimide).

Some grades of FFKM are rated at 327 C, which is highly interesting. Chasing down one of those for a reasonable price in suitable dimensions was another thing though..

We ended up testing a grade of Polyimide that could be bought and which is rated at 280 C for continuous use (some sources say 300 C).

FFKM is interesting because it is a type of rubber and thereby should work really well both as a seal and as a heat break.

I am not sure how it will handle the pressure though. You have about 2.2 kg of pressure from the spring, pressing the PTFE down towards the heater block.

The advantage with Polyimide in this case is that it stays reasonably hard even at really high temperatures, which is not the case when it comes to PTFE for example.

 

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In case you are able to get different grades of Kalrez, you could have a look at the data here to select a suitable one: http://o-ring.info/nl/downloads/datasheets/kalrez-ffkm/

What might happen is that an o-ring used without internal support deforms under the pressure from the spring and ends up jamming the filament.

Originally, I wanted to get a 1-1,5 mm sheet of some reasonably hard high temperature grade of Kalrez and make a flat seal out of that one.

If you can get such material it is really worth trying, since at least theoretically, it seems like a very suitable material for this task!

 

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The time has finally come 10 months later.... time to change this coupler thingy.... i think? I clean my printer before every print and this happened. I know this is the result of a nozzle jam as ive seen it before during my early days of learning before I did atomic pulls, but it was perfect so....

20150714_103736.thumb.jpg.7739e0244bdfae9298d92670991c4f47.jpg

20150714_100632.thumb.jpg.6166ac4a228b090d5ce09d76eda4f8f6.jpg

20150714_100639.thumb.jpg.92301f7b068db7cac9961f925a4d9160.jpg

I may try just sliding it down first but then again why not just replace the damn thing once and for all and save my self all the messing around, lol.

20150714_103736.thumb.jpg.7739e0244bdfae9298d92670991c4f47.jpg

20150714_100632.thumb.jpg.6166ac4a228b090d5ce09d76eda4f8f6.jpg

20150714_100639.thumb.jpg.92301f7b068db7cac9961f925a4d9160.jpg

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not specific for the teflon but here's something that shows how to take the head appart;

http://ultimaker.com/en/community/view/11129-um2-replacing-heat-cartridge-and-pt100-b-sensor#reply-99197

here's the assembly manual pdf;

https://github.com/Ultimaker/Ultimaker2

I ussually first take the fan shout off, and hang it with a bend paperclip on the Y-rod, so it out of my way. You can also put some tape on the black plastic parts so they stay toghether nicely, but I usually don't do it ..

and, I would consider placing an olsson block if you are taking things apart anyhow.....

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Thanks for that, i did it last night because i couldnt wait any longer and just unscrewed everything didnt do the tape thing but seemed ok and realised i should have done the atomic pull and cleaned the inside, but if i have any problems i guess that will be my first port of call just wanted to get the damn thing in, was a real pain to get out needed to uncrew the entire metal thing it stuck in and wedge it out!

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Well i clearly did something wrong, did 3 atomic pulls with no luck after. gonna have to take it apart again, lol.

any idea why the coupler has decided to move real high leaving a huge gap between the metal and coupler? Was Ok when i fitted it? means the filament always gets snagged on atomic pulls?

20150715_112050.thumb.jpg.d412ce20bc8f85c92ba85381fa51136f.jpg

I may just try a print in the meantime and see how it goes out of curiosity while i wait for an answer.

20150715_112050.thumb.jpg.d412ce20bc8f85c92ba85381fa51136f.jpg

Edited by Guest

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OK there was some serious leakage around the couper end to where it meete the metal, so after burning my fingertips heating the metal thing up to get theplastic out, i still have the same issue of a big gap? im not sure if im twisting the main metal thing too much or too little and its pushing the coupler out as i do it?  here is a pic explaining what im not sure about.

what is the right amount of gaps for both?

It weirds because the coupler is identical to the one i replaced in size yet it doesnt fit the same?

20150715_124154.thumb.jpg.d69ff0cb4bd90e5707427cbdae3b05e7.jpg

gap 2 is where plastic was leaking out from btw

20150715_124154.thumb.jpg.d69ff0cb4bd90e5707427cbdae3b05e7.jpg

Edited by Guest

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OK on the road again, ended up giving it all a good clean and loosening the gap 2 after looking aroung on the pic from the above post, left a 1mm gap and even though the coupler is still far away it seems to be working....

got those funky lines a bit more than before, weird edges too which i dont think i had before but ill see how it goes...

20150715_132649.thumb.jpg.8398e2def7b068349429d5c2ccedf6b4.jpg

weird edges causing the wobbly looking first layer someone asked about, they join up fine which is even weirder.

20150715_132732.thumb.jpg.6cf2a8d25f470123cac25fac2c0d89d4.jpg

20150715_132649.thumb.jpg.8398e2def7b068349429d5c2ccedf6b4.jpg

20150715_132732.thumb.jpg.6cf2a8d25f470123cac25fac2c0d89d4.jpg

Edited by Guest

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I think your spacing is off.

file-Re8POn0Hr3.jpg

This picture shows the spacing really well. You're only supposed to have ~1mm between the hot end isolator (metal part above nozzle+heaterblock) and the PTFE.

picture1.jpg

Here's a diagram I found in another thread that shows it well too.

That's one nasty coupler! Definitely time for a change :) About how many hours of printing did it see?

  • Like 1

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It saw 10 months of pretty much non stop printing. I was forcing prints using a work around method for the last 3-4 months though lol!

this is how i was printing from the time it started to fail.

 

Yep! thats the picture i used to change the spacing before i just rushed it though not paying attention to all the measurements and spacings thinking it wouldn't matter, lol, it did. Its appears to be all good now. might even give it a bit more space. I gave it too much before and now i think a touch too little. Ill see how it goes and change it if i have any problems.

Thanks!

Edited by Guest
  • Like 1

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