PFTE tube (for 1.75 mm) pops out of j-head PEEK tube

I bought J-head compatible but the set screw doesnt keep the PFTE tube in the PEEK tube while operating. I tried putting tape on the PFTE tube so it would have to push off the tape to come out, but it just breaks through that..

It might be that the set screw is too small, the heater resistor is way smaller than the heater resistor itself. That would be fairly easy to deal with, but not at all an issue for me as i also i have a heater cardridge that fits. Hmm it seems that they use the same socket screw for the 3mm filament version.. that cant be right.. So i might need a matching socket screw? Or am i missing something? (Not sure if reprapworld got their stuff quite right..)

Edited 1 time(s). Last edit at 09/06/2013 09:48AM by Jasper1984.

"the heater resistor is way smaller than the heater resistor itself."

That does not make much sense? Do you mean the hole for the heater resistor is smaller than the resistor itself, if so it probably is made for a cartridge heater which mine are 6mm and the 6.8 ohm resistors i have are 5mm so I would use the heater cartridge. Pics would help people better understand what you are talking about.

To be clear the first paragraph is the problem; the PFTE tube pops out and the set-screw doesnt seem to be anywhere near small enough inner diameter able to hold it.

The second paragraph was wondering if this set was composed correctly.. Or am i misusing the set screw? surely you dont have to rotate it all the way down?

Right, pictures, sorry if they're bad, i only have a (pretty decent, but..)webcam and used a separate lens to get it in focus.


The whole thing, with the set screw next to it. (Something to keep in mind; the thermistor came loose very easily, tried to stick it down better afterward.)


How i am trying to keep the set screw stuck onto the pfte tube, dont think it will work. It is just a layer of gaffer tape with the set screw pushed over that, and then some more under it so it would have to push that out of the way.(However since it probably already had to move to get that effect it might be moot) Also i put kapton at the bottom with the idea that the tube would have less room to move


Rotated the hot end screwing the set screw on.(presumably if you use pliers with stuff like these, masking tape helps protect the screw?) Then i put everything back to the printer, and recalibrated the height, turned it on, checking the thermistor worked.

Then extruded a little while in the air, and it failed pretty quickly.. Looks like in this case i might not have rotated the set screw in far enough though. Try yet again...

Right 'trying again' waas just screwing the set screw further, i wanted to see if the tape approach would really fail, and it did.

On my j-head, the PTFE tube isn't held in by anything. The hollow set screw seems simply to fill the space between the PEEK and the PTFE tube.

I'm pretty sure you need another item to hold the tube in place; that is why you see things like this:

[www.thingiverse.com]

The small fitting has clamps that hold the tubing tightly into the j-head.

What emccarron said. With a Bowden configuration, you need some sort of compression fitting to hold the PTFE tube.

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I got the thing to not break out the tube, but i think things are still moving too much to avoid it clogging up. I figured the hot-ptfe-tube ends the reprappro came with can drill themselves into the PEEK causing only (afaics)irrelevant damage(making itself some threads in there), and has a good shot of creating a tight fit in there, so am giving it a shot.

Edit: note that i had to take ~3mm of PLA stuck in there out. Pushed pla through manually using a bit of PFTE tape until i saw the metal.

Edited 1 time(s). Last edit at 09/12/2013 08:03AM by Jasper1984.

Okay... If I got anything wrong/misunderstood, please correct me.

Having said that... I believe your problem is.. simply that your PFTE tube is coming out through the socket hole of the set screw, right?

Also, you are trying to use 1.75mm filament.

I have a J Head and I exclusively use it for 3 mm filament. I think this whole thing was made for 3 mm filament; the PTFE tube has 3 mm (probably ever so slightly larger than 3mm) inside diameter, and the socket hole in the set screw is big enough for 3 mm filament to pass through, too.

By the way, the bottom of the set screw presses the top of the PTFE tube, instead of PTFE sqeezed into the socket hole and relying on the friction/slight side way compression to hold it in place (just in case that's how you think the set screw is supposed to hold the PTFE tubing in place).

I would imagine (sorry, I haven't tried it myself or researched it) if I want to use 1.75 mm filament with this J Head, I would need to buy an "adapter" PTFE tube and also a different size set screw (the same outside diameter, but a smaller inside diameter/socket size). This PTFE tube should have 3 mm external diameter, so that I can just "plug it in" without removing the existing PTFE tube.

Like I said, I just think that's what it would take to modify my J Head for 1.75 mm filament.

Another possibility is, again in my imagination, to replace the existing PTFE tube all together, and the new PTFE tube would have the same outside diameter as the existing PTFE tube, but its internal diameter would be 1.75 mm. I should be able to use the existing set screw with this setup, since there still will be plenty of PTFE tube (toward the outside) for the set screw to catch and hold in place.


I wonder if you got this "adapter" PTFE tube without the 3 mm PTFE tube. You said you put some Kapton tapes around the tube 1) to make it not to come out through the set screw, and 2) to make it not move around inside of the hot end.

Those two things tells me that your PTFE tube is way too small (thin) - I believe the PTFE tube should fit tight inside of the hot end. Also, judging from the fact that it goes through the socket hole, I think there's a good chance your PTFE has 3 mm external diameter.

So, I think you just need to get a regular (for 3 mm filament) PTFE tube, stick it into the hot end, and then insert the PTFE tube you have into this "outer" PTFE tube you installed (well, assuming my imaginary process of outfitting 3 mm J Head to 1.75 mm filament described above was indeed correct).

You can buy ready made PTFE tube everywhere, or make one yourself out of raw materal (i.e. [www.mcmaster.com]).

I made this PTFE liner myself - it took me a couple of tries before I got it right (cutting 30 degree angle was trickier than I thought), but I still have more than half of raw material left and I spent less money than cost of one ready made PTFE tube.

Oh, and you would need to by a different size set screw. However, if you can find a washer, which is small enough to fit into the opening, and has a perfect size internal hole size (larger than 1.75 mm but smaller than the external radius of your 1.75 mm PTFE tube), you may be able to place it between the butt end (top) of the PTFE tubes and bottom of the set screw.

Edited 7 time(s). Last edit at 09/12/2013 06:56PM by Yamster.

I tried the stuff i talked about, it doesnt pop out anymore, but it does clog pretty quickly and the delay to extrude is pretty long, it is probably accumulating in there again.

Which part of making the liner consists of needing a 30-degree cut?

I have some pfte tube for 3mm, seemed like good due course to get some. It i can easily hand-drill the inside out to 4mm and then the smaller pfte tube fits inside. But it slides out pretty easily so both will have to be held in i think. Could look around for some glue but it has to work for pfte and the temperature..

Should check if the bigger tube has fits in the PEEK in the first place, after all, it is advertised for 1.75mm..

Right i dont think it would fit, there is just room for the 1.75mm pfte tube plus about one layer of kapton. The thicker layer of kapton was in the area where the set screw screws in..

For some reason the peek tube screwed off easily, maybe it is just thermal expansion. there was a layer of PLA in there i screwed it back up, heated to pla-melting temps and screwed it far enough that the PLA squiezed out.. Maybe it wasnt pushed in far enough? I also decreased insolation of the thing.

Edited 1 time(s). Last edit at 09/16/2013 10:44AM by Jasper1984.

Hmm... I am not quite clear your current situation... It's been a while and it's just way too confusing for me.

The 30 degree cut I was referring to can be found here: [reprap.org]

While revisiting the J Head RepRapWiki page above, I've noticed there's a set of instructions for outfitting a J Head for 1.75 mm filament. [reprap.org]

It seems like it basically requires us to stick in a 1/4" OD (outer diameter) PTFE in to the hot end/cold end, and drill out the center with 2 mm hole (so that the 1.75 mm will fit in).

The 1/4" OD for this "home made" PTFE tube for 1.75 mm filament is the same as 3 mm filament PTFE tube that we can buy. The only difference are 1) the ID (inner diameter) and 2) 3 mm PTFE tube has a hole in the middle already while we have to drill a hole ourselves with 1.75 mm tube (so it's more like a cylinder than a tube).

Well, that's what it looks like according to those instructions. However, I think I have seen a "adapter" tube on some vendor web site, and I would imaging some supplier are out there selling PTFE "tube" (not "cylinder") for 1.75 mm filament.


Having said that, what is the outer diameter of the 1.75 mm PTFE tube that you are using? It's hard to know for sure by looking at a couple of pictures, but to me it looked like smaller that 1/4". I wondered if it is actually 1/8" instead, based on the fact that it can slide through the opening hole/socket of the set screw.

And, that really was the key point of my previous response. I apologize if I wasn't too clear - I tried my best though. LOL.

So, anyway, can you measure the outside diameter of your PTFE tube and let me know? It won't have to be too precise - all I'm wondering is if its 1/4" or 1/8" - so you won't need a digital caliper.

The tube is 2mm inner, 4mm outer, 0.15inch..

Yeah, i suppose it is hard to follow by now. I think by now my problem comes down to there being space for partially melted PLA. The taper might help, but i think need a way to make sure there isnt any room in the first place. Basically i have to slide it down, feel the end, and this set screw is too tricky to move down for that. Probably i'll add a spring that should compress..(considering some of the talk here) anyway i'll make some photos so it is clearere what i mean.

Yep, like I said, it took me a couple of failed attempts before I got my PTFE tubing right.

First time I didn't have any taper. The second time I did have a tapered end, but I did not tighten the set screw tightly enough, there still was a gap between the (tapered) end of the tube and the top of the metal head/melt zone.

Both times, when I took the PTFE tube out I had to pull it very hard (I had to used a pair of pliers and deformed the tube into unusable shape) because the melted plastic seeped out through the opening and glued the (outside of) PTFE tube to the (inside) of PEET body.

When I finally got it right, I made the same 30 degree tapered end and this time I just made sure I tighten the set screw enough - since my PTFE tube is too wide to come out through the opening of the set screw, more I turn the set screw more pushes the PTFE down. Also, i was able to control the length of the PTFE tube since I made it myself. I did not have to use a spring or anything to get rid of the gap.

So.. what is the outside diameter of your PTFE tube? Is it 1/4" or 1/8"?

The width was 4mm, so neither 1/2'' or 1/4'' closer to the latter

I used the thing in the picture, the spring was way too weak, but i could tighten it a lot afterward, it is totally compressed now. I got a tiny print out of it so far, and bigger one is running. I dont really quite trust it, probably i should make a printed version of this, using screws instead of wires. this design looks good, though i prefer using openscad.(well havent used google sketchup)

It seems to go fine but then the extrude drive motor kept going but the gear failed to follow.. the axis got itself loose. hmm the screw is gone, decided to put it back and continue anyway..

Looks like the print is working otherwise. despite skipping the filament a bit now and then... Also had the spool hanging up. It goes into the filament drive right off the spool, but gets stuck when filaments cross in the spool..

Made an initial version for an openscad model(edit: some values for sizes of the j-head are incorrect) for basically this idea of holding the pfte tube but with screws.

Thing i made.(Note: i dont really like thingiverse, its too facebook-like, and rather have other players held it, but giving feedback is good... Though it is not really needed here because he already had some mades) Hmm, up close it actually looks pretty bad and structurally not decent either except for some early layers. At least it is something.. Not good enough to make the holder with if it is like this..

Maybe the thermistor is off.. I looked at it and i cannot figure out how to change the source code. So since it looked good i went with it.(bad, i know)

Edited 1 time(s). Last edit at 09/18/2013 12:43PM by Jasper1984.

Looks like temperature was blocking part of the problem, i raised it from 210 to 220 a bit and now it prints much more nicely.. Also tested ooze and that's much better than with my earlier nozzle.(which had a build mistake) Still little pips though.

Thanks for the answers, suggestions and emotional support.

Not sure how useful my design is, depends on what those pneufits really do and how those other designs avoid having that space to the tube.(when i reset i should still check how important temperature was) Pneufits look like they might be more convenient, 'press fit', does that mean you can easily take the bowden tube out? They're only 2€..

Right, think it warrants an update. The thing i used didnt work; it seems the tape is still slipping somehow. But the higher temperature made it work, kindah. It would get stuck later, presumably due to a gap between pfte and hot end again. I was able to print some things with which i made the thing i linked earlier, but modified(git is updated) not to use a widening of the pfte tube, instead keeping a second tube in.(pictures in attachment) This method has no chance of slipping. I used the pfte-tube-end-thing from the reprappro to hold the 'outer pfte tube' in place.(it'd be handy to avoid that.)

This seems to work near-perfectly.. Unfortunately the next print ran out of filament mid way >< i could not figure how to restart, cutting up the gcode made the printer go nuts. Otherwise though it is the best print so far.