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(edit on 1/24: turn clockwise, not counter-clockwise)

My .35 nozzle on my Rostock MAX v2 clogged yet again. Tired of the ritualistic nozzle cleaning, I decided to finally switch to a different nozzle (.7 this time) and switch to PLA while I was at it. I took pride in printing ABS with a fine nozzle, and I'm feeling unmanly for downgrading. Please pity me.

Anyway, I'm embarrassed to admit I just spent 2 hours trying to replace my hot end nozzle. I simply cannot figure out how to get this new nozzle in. It is a very, very tight fit, but that's true of the nozzle I took out. I cannot get the threads to catch. I am perplexed on how to overcome the non-threaded portion of the assembly. What am I missing?

Seems like I have to do all of the following at once:

• Push the nozzle in with great force
• DO NOT push directly on the nozzle tip, or I risk denting it, screwing with extrusion
• Turn the nozzle clockwise
• Keep a wrench elsewhere on the hot end to prevent the rest of it also turning
• Avoid damaging or disturbing any wiring.

I wasn't able to find instructions or other threads of people with issues attempting this. I have tried several different methods with a assortment of hand tools.

At this point I'm confused as to whether something is broken, such as maybe stripped threads.

What is probably happening is that the edge of your nozzle (on the non-business end) is probably getting hung up on the PTFE insert inside the PEEK heatbreak. Try to carefully align the nozzle so the PTFE slides down into the nozzle and you should be golden.

EDIT: I also noted you mentioned you need to turn the nozzle COUNTER-clockwise, however, counter-clockwise would be LOOSENING the nozzle. Try turning it clockwise and see if you have better results.

I suspect your jamming issue involves the diameter constriction of the PTFE liner that happens over time. I can see the brow spot on it where it happens. (over time hottest portion of the PTFE liner will shrink a bit, causing jamming & feed issues)

The simplest way to swap nozzles is to remove the PTC connector from the top of the hot end, then insert the PTFE liner into the nozzle and then try to install the nozzle. What may be happening is the PTFE liner might be a tiny bit long (I don't recall what the length is supposed to be.) and it's hitting the bottom of the PTC fitting. By removing the PTC fitting, you can get the nozzle installed properly and then see if you need to trim the liner a tiny bit to allow the PTC fitting to fully seat.

g.

Before attempting to install this replacement nozzle, I removed both the PTC fitting and the inner small PTFE tubing/lining. Maybe that was a mistake? Should I keep the tubing in there for alignment reasons?

I'm glad to hear the brown spot on the tubing is normal. I am careful about temperature (I heeded the warnings regarding melting PEEK). I was a little worried the brown spot indicated that the temperature exceeded the maximum and screwed something up.

I expect my clogging issues were normal, and my most recent clogs were due to dust on the dormant printer. Using a .35 nozzle with black ABS filament seems like worst case scenario. I know the "cold pull" method, which usually worked (and I'd cut off the end of the filament). If that failed, I also have guitar string if I have to get aggressive. I've only resorted to the blow torch once.

Note: I've fixed my original post in which I said "counter-clockwise" instead of "clockwise".

I solved it! (somewhat)

The main problem was that hot end was still clogged with plastic, even with the nozzle removed. I heated up the hot end without a nozzle, and used tweezers to clean it out from below. I would prefer a more thorough cleaning, but I would have to cut wires..

This was not a normal clog. It occurred while I was trying to clean out the .35 nozzle. I had attempted manual feeding the filament, which I often do in the cleaning ritual. It backfired time time around. It pushed up the PTFE quite far. This was far enough to pass the nozzle therefore stuck in the "raw" hot end. This was ABS plastic, and I'm switching to PLA, so this residual plastic is a bummer. I'm hoping the liner protects me. Also, I'm using a .7 nozzle now, so hopefully any unmelted ABS can extrude without too much fuss.

It was still incredibly hard to get the new hot end on there. I'm not really clear on why, but it's understandable that the threads are precise and picky. There isn't a good way to get leverage on the hot end itself since the two flat sides of the tip also host the thermistor and heating elements. I managed to do it without damaging anything, apparently. So here's hoping it holds together. Otherwise I'll need a new hot end. I'm happy enough that my mystery is solved.

--Johnny

When I've had clogged nozzles with ABS, I usually "torch" out the clog with a small butane torch. I don't think you can do that with PLA though - I think the PLA just carbonizes inside the nozzle and makes the jam rather permanent.

I'm glad to see you got it sorted out!

g.

geneb wrote:When I've had clogged nozzles with ABS, I usually "torch" out the clog with a small butane torch. I don't think you can do that with PLA though - I think the PLA just carbonizes inside the nozzle and makes the jam rather permanent.

I'm glad to see you got it sorted out!

g.

PLA also burns out clean, I have cleaned out nozzles that way and we have used it for basically "lost wax" casting in plaster investment, no ash remains.

TIL!

BTW, are you familiar with the adventures of Luke Vaxhacker and Dec Vadic?

g. (former owner of a VAX 8250)