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I've tried using a throat with a PTFE tube, but encountered the problem described in this question. It seems only a small amount of excess pressure in the extruder is enough to force out the inner tube. This makes me worry that with this particular part, I won't achieve a reliable configuration (and I'm experiencing some binding with the original plain steel throat, so a PTFE liner seems worth exploring).

I was wondering about the advisability of using a retainer to apply some pressure at the cold end - a nut with a washer soldered on maybe.

My goal is to prevent the teflon tube from rising up, so I can use this part and retain some resilience against excess extrusion pressure. I was assuming I had a slightly sub-standard throat part (in a pack of 6).

However, I now wonder if the problem was caused by too high a temperature (this is ABS filament) and maybe the teflon will be too soft to function as designed, so if I go back to PLA filament, maybe it is more likely to work without modification.

Extruder

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Sean Houlihane
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  • Why do you think you need this modification? I am not sure what you are trying to accomplish. That said so long as it's outside of the melt zone... else use metal. – StarWind0 Dec 31 '16 at 21:30
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    @SeanHoulihane I have temporarily closed this question as it is currently unclear what you are asking. I believe you're trying to prevent the teflon tube from being forced out, but I'm not sure. Seeing as how this question has been active for a little while now, I would recommend trying to make your question a little clearer. I will keep tabs for a few days and re-open if it becomes better. If I forget, don't be afraid to PM/ping myself or another moderator. Thank you. – tbm0115 Jan 08 '17 at 21:34
  • @Sean Thank you for updating your question. Hopefully our answers help. – tbm0115 Jan 09 '17 at 16:15

2 Answers2

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In this case I would like to first recommend replacing your PTFE tube with a better quality product. Unfortunately, the quality:price ratio is as to be expected here. My reasoning:

PTFE has great thermal properties for a polymer, just like ABS. In fact, the glass-transition state begins at relatively the same temperature between the two materials. ABS starts transitioning at about 105°C and about 127°C for PTFE.

However PTFE, traditionally, has a much higher melting point at about 327°C as opposed to the usual 125° we use in 3D printing.

My Point: I think the hardware you currently have has low-quality PTFE.

PTFE can be recycled for re-use in other PTFE products. In recycled PTFE, you can lose a lot of the desired properties in the material (true for any material). This includes both the ideal "friction-less" and thermal resistance we need in 3D Printing.

What I think happened: The higher print temperatures of ABS transitioned the PTFE into its glass-state. As the throat expands, the path of least resistance in the assembly is towards the extruder motor since the nozzle holds more pressure.

I would not recommend "fixing" this problem with a retainer! By forcing the PTFE throat to stay in position, you could potentially force the PTFE to expand in other ways. Most likely resulting in constricting the filament, leading to grinding of filament on the drive gear and clogging of the nozzle. Worst case, you end up with gooey PTFE in your nozzle and/or around your retainer.

tbm0115
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I see, you want to Block the tefflon tube from going Up and Out of the extruder. Yes I see no reason why you would not fid a nut cap. Drill a hole and have it work. There is likely a special nut cap with a pre existing hole in it already but I decided the keywords was asking for bad results on a work computer.

The only thing I can see happening is you will 1) possibly not have the clearance. 2) have a larger thermal mass.

enter image description here

StarWind0
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