0.25 print core clearing

[JohnInOttawa 104]

I hope this finds everyone well!

 

I've inherited an AA 0.25 print core, I don't know what material it was printing before I got it, but it seems unable to print with Ultimaker PLA, essentially behaving as though it is clogged. 

 

I've run through cleaning filaments, hot and cold pulls several times.  The filament that I do get is much finer than I am used to seeing on my other .25, so I think something is still in there.

 

Is it possible that some of the high temp filaments aren't cleared by the cleaning filament? 

 

Thanks for your thoughts!

 

John

[Montani 4]

Hi John, 
Sound like there is still some left in there. You could work around the cleaning wizards and play with the temperatures yourself. If you use white or transparent filament to clean, you can observe well if there is still something filament left. Are you sure you have cleaned it all the way?
Good luck!

[JohnInOttawa 104]

Thanks for getting back to me.  I've used two full rods of cleaning filament and the shape of what I am pulling out looks pretty good.  There was a lot of material caked on the outside of the nozzle from the previous owner, so I am in the process of gently removing that now.  I'm not sure how hot it was printed, so will try some high temp filament next. 

 

Thanks again!

John

[JohnInOttawa 104]

I was finally able to get a better look inside the core with a borescope.   I wasn't able to get as far as I would have liked, but there is debris there that is resisting removal with the cleaning filament. 

 

I think what is going on now is that whatever is down there is either wedged or was baked at high temp from before and is not coming out with the cleaning filament, but rather is causing the filament to break first. Due to the small diameter of the nozzle orifice, I'm not going to be able to push the debris through.

 

I will need to try something different.I'm wondering about a copper 'reamer'. that won't damage the steel or brass components, but am not sure if that is going to wreck the teflon liner. 

 

My other option is to risk removal of the nozzle.  Having looked at the video for print core disassembly, I have the tools and a fine enough vice here that I can remove the nozzle without snapping the neck, but there are so many warning about doing this, I'd like to cross check options and techniques first.

 

@gr5, I know you have expertise here.  I'd welcome your input.

 

Thanks in advance!

John

 

Edited January 21, 2021 by JohnInOttawa

[gr5 2,172]

I assume you mean this video?

 

[gr5 2,172]

I've learned that even though the steel is paper thin - it is steel after all.  It can take 0.5Nm of torque without breaking every time which is more than my bare fingers can generate without tools.  So it's tougher than I originally thought.

 

Before you take it apart.  Did you do your own cold pull?

 

Remove the bowden - heat core to 200C, stick PLA down in there until it comes out the tip (or doesn't).  Put the head in the corner (any corner) so the rods through the head don't get permanently bent.  Push pretty hard - like 5kg/10 pounds.

 

At this point strongly consider sticking a needle upwards to push any gunk into the main chamber of the nozzle.  If you are in Ottowa, then know that 3dshop.ca sells a pack of needles, one of which is meant for .25mm nozzles.

 

Then cool to 90C.  While it's cooling down to 120C apply a few pounds downward pressure.  When it reaches 90C pull upwards hard.  If it takes less than 2kg/5 pounds force then start over and cool to 85C.  If it won't come out with 5kg/10 pounds pulling force then heat by 10C and as soon as the temp starts coming up, pull continuously until it pops out.

 

It doesn't matter that it's 0.25mm nozzle.

 

Anyway, once you've tried this a good 10 times, playing with the "cold" temperature and it still doesn't help then yeah try taking it apart.

 

By the way with Nylon the lower temp is not 95C but closer to 120C if I remember right.  I really like Nylon as a cleaning filament.

 

Also sometimes people recommend that if 10 pounds won't pull the PLA out, don't heat but instead twist the filament.  Someone, I forget who (geert?) does cold PLA pulls at room temp!  yes - that's correct.  Whomever it is uses the twist method.

 

[JohnInOttawa 104]

Thank you!  That is indeed the video. 

 

I tried a few different hot and cold pull techniques.  I tried polycarbonate with pretty high heat by the time I was fed up, but I'll go back and try nylon and a twist.

WRT the needle, a question there.  Often when I do a pull successfully, I get two 'prongs' of filament on the very tip, I presume reflecting flow channels in the nozzle.  I have always worried that pushing a needle in the orifice would damage the internal structure.  Maybe a false worry?

 

Thanks again.  I'll try apply these new alternatives before I take things apart.

 

Cheers

John

[tinkergnome 927]

1 hour ago, JohnInOttawa said:

Often when I do a pull successfully, I get two 'prongs' of filament on the very tip, I presume reflecting flow channels in the nozzle.  I have always worried that pushing a needle in the orifice would damage the internal structure.  Maybe a false worry?

 

There's not much to worry about. A cut through an AA-nozzle looks like this:

(as long as we're talking about Ultimaker print cores and not about 3DSolex matchless nozzles?)

 

[JohnInOttawa 104]

Thank you!  Yes, an Ultimaker AA print core.

 

I'll look for a needle.  I think I have some on hand.

[gr5 2,172]

Two prongs is not a good sign.  You get that on the 3dsolex race nozzles that have 2 paths but you should not get that on a .25mm nozzle.  You can be pretty tough with the needle as long as you don't send the needle above the heat block.  Do you have one that can fit in a .25mm nozzle?