Bowden tube connector fail?

[oeginc]

I was attempting to print this (which obviously has a LOT of retractions!). About 1/2 way thru the print, my bowden tube came out of the connector on my extruder. I stopped the print, retracted the filament and pushed the tube back in, clicked continue and it immediately came back out. So I took it apart and noticed that it was not gripping onto the tube at all anymore. I looked inside and I couldn't see any teeth. I pressed down on the blue part, and it would just go down (no springyness (is that a word? lol)) to it like on a fresh one. Luckily, I had a spare laying around - I swapped it out and everything is working again.

That being said, I have only made about 20 complete prints so far - is it common for these to fail? And so quickly?? If I have to replace this adapter every 20 prints that could get really expensive...


P.S. Does anyone know which connector this is on SeeMeCNC's website, the 4mm or 6mm OD? Also, which tube is used to go from the extruder to the hotend w/1.75mm filament? I am guessing it's the 4mm OD tube and adapter (2mm ID), but I just want to be sure. I don't forsee any plans to use 3mm filament.

Thanks!

[foshon]

Yes, the 4mm adapter (2mm Id) is the connector you want. I have ordered a couple of spares myself, and used one of the spares. My issue was with a nozzle jam while printing. It's damn near impossible to remove the tube from the fitting with plastic in the tube.

[dbarrans]

Because the filament is held at both ends, to remove either end of the Bowden tube, you need to heat up the hot end, or free up the drive end by loosening or removing the idler.

- dan

[foshon]

Because the filament is held at both ends, to remove either end of the Bowden tube, you need to heat up the hot end, or free up the drive end by loosening or removing the idler.

- dan

Yes, unless the hot end is jammed. then you are somewhat screwed.

[cpunches]

After my recent hot-end meltdown I had to completely disassemble it and try and remove the melted PEEK insulator. Once it was taken apart I had to completely clean all the plastic from the nozzle as well as removing pieces of the melted peek from the threads of the part the nozzle screws in to. I had to use a combination of soaking everything in acetone to clear the nozzle and then heating the other piece over a stove burner to melt the residue from the threads. To make a long story short, foshon is entirely correct

[Eaglezsoar]

Foshon is always entirely correct, unless he is wrong.

[foshon]

Foshon is always entirely correct, unless he is wrong.

I AM NEVER WRONG.... unless I am.

[dbarrans]

Yes, unless the hot end is jammed. then you are somewhat screwed.

Not really. Then you pull the extruder idler and you can disconnect either end of the Bowden tube.

- dan

[foshon]

Yes, unless the hot end is jammed. then you are somewhat screwed.

Not really. Then you pull the extruder idler and you can disconnect either end of the Bowden tube.

- dan

Not in my experience. Unless you can get the filament out of the tube, you can not compress the push pits teeth to disconnet the tube. I'm easy bro, make a short video of how you disconnect the bowden from the push fit with the filamment inside.

[dbarrans]

1) Remove the extruder idler. This will free up the filament at the extruder.
2) Push down on the tube fitting release at the extruder and pull out the tubing a couple inches. The filament will come along with it since the extruder isn't holding the filament.
3) Push down on the tube fitting release at the hot end and pull out the tubing a couple inches. The filament will slide inside the tubing wile you do this.
4) Now you have access to the filament just above the hot end. Have your way with it.

Hopefully no video needed.

- dan

[dbarrans]

Hmmm. Maybe I push on the tube while I'm pushing on the release. Now that I think of it, I'm pretty sure that makes it easier to release the tube from the fitting.

Think of it like a Chinese finger puzzle. You need to push in your finger to get it to release.

- dan

[foshon]

Hmmm. Maybe I push on the tube while I'm pushing on the release. Now that I think of it, I'm pretty sure that makes it easier to release the tube from the fitting.

Think of it like a Chinese finger puzzle. You need to push in your finger to get it to release.

- dan

You have to either compress the tube or strip it, compression isn't happening with filament in the hole. Stripping it will eventually lead to buying a new one, hence it's a pain in the ass.

[dbarrans]

OK, I had to go try it. It still works for me. There's filament inside the tube. The tube doesn't compress, and doesn't need to. It's much easier to push the release while applying a small amount of downward pressure on the tube, but the release will still work without putting any pressure on the tube.

This thing is pretty much the same design as a SharkBite plumbing joint, and the plastic release sleeve acts pretty much like the release tool for a SharkBite. It pushes the teeth away from the tube, without compressing the tube. A SharkBite can be used (and released) with copper pipe, and it doesn't need to compress the pipe to do it. Why would our Bowden fittings be any different?

- dan

[dbarrans]

When you insert the tube into the fitting, the teeth dig into it, pointing towards the end of the tube. When the extruder pushes filament, it tries to push the tube out, which makes the teeth dig in more, allowing the tube to slide out of the fitting slightly while the teeth dig in deeper.

That's why it's easier to push the release when you push on the tube. That tends to ramp the teeth out of the tube, then you can push the release, which levers the teeth away from the tube allowing the tube to be pulled out.

Think about it -- you can push the tube into the fitting with filament in it to install it, so all you need to do to pull the tube back out is to push it in as far as you did when you first installed it and release the teeth.

- dan

[foshon]

When you insert the tube into the fitting, the teeth dig into it, pointing towards the end of the tube. When the extruder pushes filament, it tries to push the tube out, which makes the teeth dig in more, allowing the tube to slide out of the fitting slightly while the teeth dig in deeper.

That's why it's easier to push the release when you push on the tube. That tends to ramp the teeth out of the tube, then you can push the release, which levers the teeth away from the tube allowing the tube to be pulled out.

Think about it -- you can push the tube into the fitting with filament in it to install it, so all you need to do to pull the tube back out is to push it in as far as you did when you first installed it and release the teeth.

- dan

I don't need to think about it, I lived it, several times. Could not pull out the compress the push to fit (blue part) with filament in the tube. Maybe it was becuase the filament was also jammed in the hotend, don't know, don't care. Like I said I'm easy, show me.

[dbarrans]

Pull out? No, you need to push (not pull) the plastic piece to release the tube.

Sorry, don't have an easy way to hold my phone to take a video while I use both hands to show you. Not interested in spending more time on this. Like I said, it works for me.

- dan

[foshon]

Pull out? No, you need to push (not pull) the plastic piece to release the tube.

Sorry, don't have an easy way to hold my phone to take a video while I use both hands to show you. Not interested in spending more time on this. Like I said, it works for me.

- dan

Your right, two thoughts, didn't backspace enough. I was wrong. You can pull the tube out with filament in it, just tried it. In the case of a hot end jam though, the pressure on the tube prevents this. Also, not everyone uses the Steve's extruder. In my case, I would have pressure between the fialment drive and the hotend (partially caused by my driver altering the cross-sectional geometry of the filament). I'm not absolutely positive it would have helped in a lot of these cases.

Steve's hot end has a fairly large melt zone (from what I gather) which leads to heat creeping a considerable way up the filament. With the large (10mm) retracts some folks are using to run this setup, it is not difficult to understand how softened plastic could be caught in the (or near the) pushfit connector itself. This is the scenario that led to the destruction of my first fitting.

[dbarrans]

Sorry if I got a bit short. I assumed we were talking about the extruder and hot end as supplied by SeeMeCNC. And it's hard to stay calm with that guy in the orange shirt screaming at me.

- dan

[geneb]

I'm more worried about him leaping off the screen at me...Dude could give Freddy Kruger sleep issues...

g.

[foshon]

No worries Dan, I hate internet discussions that get "heated". It's hard to judge inflection and intent on a computer screen. : )

I like to consider him my "inner self", he stays there most of the time.

[JohnStack]

Y'all jinxed me today. I was reading this thread this AM.....

My problem happened recombinantly.

First, I had changed spools but put back on the 3/4 inch cable shield I was using that prevents the cable getting caught on the Z-stop adjusters.

So, the tube gets caught and I have to do a powerdown. I tried doing another print; however, I noticed it was jamming. I pull the hot end tube out and this is what I end up with. Sorry but for the photo quality but I think you can see what happened. It simply broke.

After reading the forum for a while and anticipating some possible problems, I'm very glad I bought an entirely new hot end assy when I bought my machine.

I think this is another candidate for a fix @SeeMeCNC.

[geneb]

Is that PLA? It looks like a classic PLA jam to me.

g.

[JohnStack]

It was PLA! No getting this tube back.

[geneb]

Do you have a small fan on the PEEK section of the hot end?

To clear a jam like that, you normally heat the hot end to about 185C and quickly "jerk" the filament out of the hot end. There's a guide online where this is described, but I can't find it for the life of me. I suspect asking on the irc channel #reprap will turn it up in short order.

g.