Extrusion problems - bad PEEK part?

[gadgetfreak 7]

I have some strange extrusion problems since about two weeks.

Prints (same gcode) that previously have worked well suddenly give inconsistent extrusion and "easy" overhangs that usually prints well print as if it was an overhang with a too shallow angle with curls as a result.

I have tried different temperatures to no avail.

Manual extrusion feel a bit "slow" as if there some kind of plug somewhere, even at hotter temperatures.

But I have a vague memory of that my hot end started to smell a bit funny at one time and that some smoke fumes was coming out , perhaps around the same time as when the models started to come out worse (but I didn't notice initially). I think the temperature might have risen to about 250-260 degrees so I shut it off but didn't think too much of it then.

Today I started disassembling my hot end (it's been over 6 months since I needed to do it last time). I only did a little cleanup in the lower and upper part, assembled again but with same bad results.

Now I have disassemled so that the PEEK and attached brass tube is detached as can be seen in this picture:

 

Is this black gunk between the PEEK and brass an indication that the PEEK has melted partially?

I cannot unscrew the brass pipe from the PEEK easily and perhaps I would need to heat it up first (oven 200 degrees maybe?) but for now I've left it in my lab.

 

I have a friend who has spare hotend parts, perhaps I should just try to replace the PEEK/brass pipe or what do you guys think?

Thanks,

Daniel

 

[nick-foley 5]

Is this black gunk between the PEEK and brass an indication that the PEEK has melted partially?

 

I think it is just overcooked PLA ooze, but I'm not 100% sure. Something similar was happening to my ultimaker (and to get consistent prints, I had to keep raising the extrusion rate with each print, eventually reaching the point of stalled/ground filament).

...I then broke the brass tube trying to remove it from the PEEK. Even hot, it can be very challenging to remove because there is not a strong place to grab without crushing the tube. They should really make the round flange of the brass tube have two flats, so that you can grab it with a wrench without having to transfer force through the thermal break. (Actually, forget that - they should just redesign the entire hot end with less parts and fewer points of failure.)

I ended up fixing my machine with a Makergear tube and nozzle. Prints seem to be good so far but I don't think I've solved the problem entirely yet. If I were to do it again, the first thing I would do is try a new nozzle without messing with the rest of the setup. I don't know if it was the cause of the problem, but it's a simple, easy test that allows you to eliminate one variable from the equation for the rest of your troubleshooting.

 

[gr5 2,167]

I agree that the black gunk is probably PLA that leaked long ago and slowly over many prints baked itself black. It is helping you by sealing any leaks. But there could be more black gunk inside which would be bad. Personally I would put the whole thing in an oven at 200C and then take a hot wire and clean it all out.

 

[gadgetfreak 7]

Thanks guys. I have new hotend parts, but no time to try them on yet. And I get my big Delta Tower printer tomorrow or Tuesday so I hope that I will take the time needed to fix my Ultimaker so I can print in parallel