PTC connector unscrewd

[buttim]

My brass fitting unscrewd during a print. I stopped everything and tried to screw it again in place. It doesn't seem to fit anymore.
I would contact SeeMeCNC support but I already tried for a different problem and got no answer.
Any suggestion to fix my problem?

[Tinyhead]

Which end does it fit into, and how it it not fitting anymore? It won't thread in?

Could you take your filament out and release the bowden tube so that you can inspect the PTC fitting entirely? See if you have damaged threads or anything?

[buttim]

Yes, the problem is with the brass fitting that seems impossible to thread in.
I cut the filament and examined the thread with a lens but it seems ok.
Here is a picture of the opposite side

[McSlappy]

Looks like there's something blocking the hole - what's surrounding the filament there?

[buttim]

I was thinking the same but... who knows? I mean: I had no idea what the open end should look like. Might it be that the PTFE bowden broke inside?
How am I supposed to remove it? Will I be able to find another bowden should it be too short now? I mean easily/cheaply as I'm from Europe (Italy)

[Holy1]

What you are seeing is a smaller length of bowden tube that stays inside hot end. When the fitting came out it must have moved up a bit so you can't see the threads. You can unscrew the nozzle and push the short Bowden out. You can reuse the short piece of Bowden again but The filament will be stuck inside the nozzle. If you were using abs the you can soak the nozzle in acetone to remove it. If it was pla then you can heat the nozzle to remove pla. The short piece of Bowden tube will fit inside the nozzle when reassembling. Hope that helps.

[buttim]

So, if I understood everything I should do the following:

• soak the nozzle heating it (will this suffice or should I make something else?)
• let it cool down
• unscrew the big bolt
• push down the small PTFE tube
• screw back the big bolt
• screw the brass fitting
• insert the bowden tube

Am I correct?
Thanks you for all the time you're losing in replying to a noob

[Tinyhead]

You'll want to remove the brass nozzle which should draw out that piece of filament with it. The PTFE tube should just be sitting on the inside of the extruder. You should be able to pop it out with something. I know mine can be a bit tight. The tubing should slide into the brass nozzle, I'm sure you'll see how it fits. In the picture it looks like it came up with your PTC fitting and maybe won't pop back down.

When you have your brass fitting, you'll want to make sure that the area where the PTFE tubing sits is free of any melted filament. I think if there's melted stuff pooled in there, you're just going to end up with a jam. If you're using PLA, you could throw the nozzle with the melted bit in the freezer for a few hours to break the whole melted piece away.

A user name mhackney details how he did it:

Made some measurements of the bore length of some nozzles. First, here's the setup. I make sure the bore is clean then hold it in needle nose pliers. I have a 3" length of PLA at the ready. I then heat the nozzle with a little butane torch MILDLY. When the too is just hot enough to allow the PLA to flow (takes about 10 seconds or less) I push the PLA in until a little nipple comes out of the end like this:

J-Head 1.JPG

Let this cool, do not touch the protruding nipple. When it is cool enough to touch, cut the protruding filament off with a single edge razor blade and place in the freezer for several hours. Put a pair of needle nose pliers in the freezer too. When ready, use the frozen pliers to pick up the nozzle - that way it does not warm up too fast. Grab the PLA and pull gently. Don't force it. It takes about 10-15 seconds for the brass to warm up from air temp and expand enough to let the PLA slide out. It will and will look like this:

J-Head.JPG

As you can see, this J-Head is dead-nuts on at .5mm bore length. Interestingly, the cone is also very flat like the E3D.

I also measured three other nozzles and they were all within .5 to 1mm in length. Only the E3D has been anywhere close to 2mm.

Today I am going to chuck one of the E3D nozzles in my lathe and rebore the 2mm lead up to the nozzle bore. I'm shooting for .8mm. I don't have any data that substantiates this but I'm thinking a length to diameter ratio of 2 is a reasonable ballpark. I've googled to try to find any information and there is very little discussion about bore length in the RepRap world, everyone is focused on bore diameter. But, at these small diameters, there is a significant friction component and the longer the bore, the more friction. Stay tuned!

I think I'm going to try this method next time instead of digging around there with a drill bit to get the clogged filament out.

[buttim]

Very detailed explanation, thanks.
Meanwhile SeeMe support did reply:

Try heating the hotend up first, as if it came out, and the ptfe liner raised up to where the threads are, then it might not go back in if the hotend is cold

Seems coherent with your ideas and much simpler, so I think I'll try this way first and remove the nozzle only if it does not work. I'll let you know

[buttim]

The simpler solution from support actually worked. Thanks once more for providing insight to the problem, I was far more confident in what i was doing.

[geneb]

For future information this is what happened....

When the ptc fitting came loose, there was nothing to hold the inner PTFE liner in place. As plastic was melted, the material began to push up against the base of the liner as it shifted. By the time you stopped the printer, a plastic filled gap had formed between the bottom of the hot end and the ptfe liner. In order to press the liner back in without tearing the hot end down, you just needed to heat it up and use the blunt tip of a pencil or other dull (back end of a 1/16" drill bit would work too) tool to push the liner back down far enough to allow the PTC fitting to grab the threads.

g.