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My J-Head may be blocked?

Posted by bmsweb 
My J-Head may be blocked?
January 24, 2012 06:16AM
I've been pretty much printing the last couple of months with out an major issues. However today half way through a print the it looked like the extrude had stopped extruding. At first I noticed it was slipping so I clean up the bolt etc Mind you I've never had it slip since using Auzze's Hobbed bolt which I got a month or so before christmas. In any case it turns out the problem doesn't appear to be the bolt or the pressure etc but rather the nozzle could be partially blocked.

Firstly has this ever happened to anyone and is it a common thing? also how to I clear it out? The hole is supposed to be .35 in dia.

Any thought of wisdom would be much appreciated.

Edited 1 time(s). Last edit at 01/24/2012 06:26AM by bmsweb.
Re: My J-Head may be blocked?
January 24, 2012 07:23AM

You could try heating the nozzle to 220C and quick retracting the extruder in the hope it will clear the hole... You could also try use a thin peice of wire to push up the hole..

Re: My J-Head may be blocked?
January 24, 2012 04:24PM
Thanks Auzze, I tried that but no luck at all. It actually happened half way through a print so I assume something go into the head and blocked it. My printer has been printing 8-10 hours a day for the last few weeks without any issues at all . . man this is frustrating. The worse part is I'm half way through my second custom build reprap and I'm without print capability sad smiley

In any case frustration aside, I've taken it apart this morning and I think if I can heat it up in the oven and then poke something through the head I should be able to clear it out. . . . well fingers crossed. I went through all my small drill and the smallest I have it 0.385 sad smiley So I need to find something small and firm enough to poke through.
Re: My J-Head may be blocked?
January 26, 2012 06:23PM
Any resolution to the problem?
I may be experiencing the exact same thing. (but with my .50 tip)
Pretty much the same scenario you described... right at the end of a print last night, it quit extruding, going "skippy".
Disassembled and cleaned the hobbed bolt.
Reassembled, and no problem to extrude through pronterface.
Restarted the print and things seemed fine, then about 10 minutes in, same thing all over again.

Are you able to extrude at all? Or does your tip seem completely blocked?
I'm going to fully disassemble again tonight, and try one more time. Might have to try poking the tip...
Re: My J-Head may be blocked?
January 26, 2012 07:06PM
I have a feeling my problem may have been a contaminant or something like that blocked the head. The solution is to remove it and clean it up best you can and then poke it clean with something. You will need to heat it up. Having said that you should be able to find something to fit the .5 head. The .35 was a real pain but I managed to clean it up and get it going again. I also plan on buying a spare head just in case I have this problem again. Mind you I've printed 8 rolls of PLA before experiencing this problem. Fingers crossed it keeps going.
Re: My J-Head may be blocked?
January 26, 2012 07:28PM
Glad to hear you worked it out! (and hopefully it *stays* fixed!)

Hoping my problem isn't contaminant, but will see later tonight. I've been printing ABS, not PLA, and not even 2 lbs thus far.
I am suspicious my problem *could* be heat transfer to the filament up the barrel and maybe too much torque on the extruder motor, combined with a switch to a different color filament (same supplier) that seems it could be a little softer than the previous color. I've been running my j-head "naked"... no insulation or fan since day one, with great results... I'm thinking I will try insulating the head and setting up a fan to cool the body.

Also, literally just had a brand new, second j-head delivered this morning... a .35 tip on this one... that I got, not as a back-up, but because I wanted to try some finer resolution printing. I absolutely don't want to try *it* until I figure this problem out.
Re: My J-Head may be blocked?
January 26, 2012 09:35PM
Good Luck with it. Hope you figure out the problem.
Re: My J-Head may be blocked?
January 26, 2012 10:49PM
Just got home... will get to work on it in a bit.
Will post back what I discover / learn; hopefully info others might benefit from.
Re: My J-Head may be blocked?
January 27, 2012 10:52AM
Well... not blocked.

I believe I had / have a combination of small issues which addeed up.
Between my e-stepper being turned up a little too much, and my pinch bearing being a little tooo loose maybe, I was getting filament stripping. I followed Wildseyed's advice here: extruder adjustment, and feel like I got it working well again. For now. Am definitely going to be keeping a close eye on things.

I still want to insulate the j-head and put a fan on it. This tan filament I am printing with just feel softer than the orange I was using. I still think heat might be part of my problem...
Re: My J-Head may be blocked?
January 27, 2012 11:32PM
I've found I need to have tension on ABS a lot higher than I do when printing PLA. I find I always need to crack up tension when changing to ABS. Once the Bobble bolts teeth clog up no amount of adjustments will get the dam thing to work again lol

I've done about 40 hours of printing since clearing the nozzle and all is looking good smiling smiley
Re: My J-Head may be blocked?
January 29, 2012 03:17PM
Glad to hear you got yours cleared up!
Good info to have.
My problem is definitely a combination of things... I didn't get time to work on it Friday, and spent all day yesterday (Saturday) assisting a friend in assembling his brand new MendelMax (got it about 2/3 done).
The odd part of this is that I printed through an entire 1lb spool of orange ABS with no problems at all. That ran out, so I switched tho this tan ABS... didn't change a thing other than the filament, and this problem arose withing a couple of days. I have again disassembled the entire extruder and hotend, and basically starting from scratch. Adjusted e-motor and have tension cranked up on the pinch bearing. So far (only a couple of small test prints), it seems to be behaving. I have *not* insulated the j-head at this point, but that is my next step should the problem return.
Regards... Buzzard
Re: My J-Head may be blocked?
January 30, 2012 05:24PM
I've become somewhat of an expert at cleaning out a jammed JHead, I had to do it about half a dozen times before I figured out how to prevent it. Possible causes include:

- Letting your temperature get too high. Particularly important with PLA, I've had it cause a jam when heated to as low as 240 degrees. Here's what gets left behind in your extruder when you let that happen: [goo.gl]
- Debris being dragged into the extruder by the plastic. Easy to happen in a dusty garage, equally easy to solve with a plastic spooler. (I've also been toying with the idea of designing a filter to clean the plastic as it enters the extruder).
- Using the wrong kind of teflon tape to seal the barrel. Some gas tape isn't rated very high and disintegrates upon heating leaving behind chunks of burnt crap that find their way into your nozzle.
- Containments in the plastic itself. Haven't experienced it myself but I've heard that others have.

The best way to clean out a JHead in my experience is with the heater element switched on. Remove the nozzle and PTFE from the rest of the extruder and clamp the nozzle in a vice, making sure you don't short out anything. Turn it on and allow it to get to around 170 degrees, then gently unscrew the thermal barrier (this is much easier when the nozzle is hot). Using a tiny screwdriver scrape away all the plastic from inside the nozzle and also all the old bits of teflon tape. Then, with the heater still on, work a small piece of wire into the nozzle from the outside to make sure there's a clear path (if you don't have a piece of wire small enough then a thin capacitor or resistor lead will usually be thin enough). When properly cleaned you should be able to shine a light up from the bottom and see it shining through.

Doing this is a huge PITA but sometimes it's your only option. Best thing is to try to avoid getting a jam in the first place.
Re: My J-Head may be blocked?
January 30, 2012 07:14PM

Great info! (And that's a nasty chunk-o-gunk you got out of there!) Thanks!

I believe I got my extruder re-tuned and am now back printing again. My situation seems to be completely related to the tan filament, not a blocked tip. I've had to make some pretty major adjustments to pinch-bearing tension, e-motor torque, and added a fan mounted to blow across the j-head body (actually angled a little bit upward toward the underside of the carriage to avoid over-cooling material as it gets laid down). I am nearly 100% convinced that this tan filament is much softer than the orange I was printing with, and is drawing heat up the barrel, getting soft, and causing the hobbed bolt to chew a chunk out and clog up.

After my adjustments, I completed a print which had previously failed 5 times in a row with a clogged hob.
Will run some more tests tonight. Am hopeful this is solved.
Re: My J-Head may be blocked?
January 31, 2012 02:23AM
Thanks for the info Myndale,

Its seems to be running well again so I'm pretty sure something got in and it could have been Debris being dragged into the extruder by the plastic which I hadn't considered before. I have my printer inside the house so its in a pretty clean environment but having said that anything is possible.

I really like the idea of having something that cleans the plastic before entering the extruder. Mind you it took a hell of a long time for me to experience this problem so fingers crossed I don't have this issue again.
Re: My J-Head may be blocked?
January 29, 2014 09:42AM
Taking the hotend apart as much as you can, putting the whole thing in the oven (minus electronics!) and then poking the softened plastic through with allan keys often does the trick. If there's a tiny piece of debris inside the metal tip of the hot end, again soften whatever's there in the oven. What I've found works best for poking through the .35mm orifice is the end of a guitar string - they go down to .08mm and are strong and rigid enough for the job. Find the string gage that's closest to (but slightly less than) your extrusion diameter, and enjoy your triumphant return to 3D printing. Good luck!
Re: My J-Head may be blocked?
June 27, 2014 02:01PM
My J-Head got jammed and i used part of a steel e-guitar "tiny e"-string to push the thrombus through the heated up hot-end (i used 215 for my pla).
That did the job for me, its worth a try-good deal.

Edited 1 time(s). Last edit at 06/27/2014 02:03PM by cosmob.
Re: My J-Head may be blocked?
July 17, 2014 01:28AM
I found that an Elixir brand Nanoweb Medium electric guitar string -- 3rd string - G - which is 0.18 inches or 0.46 mm in diameter worked well to clear a J-Head. It's essentially a solid steel wire.

Remove the J-head's tensioning screws and withdraw any unmelted filament.

Power up the extruder's heater and allow to any filament that can drip out to do so. This will also soften up whatever is inside the extruder.

After 5 minutes, while still hot, feed the guitar string, which is really a steel wire, up into the head slowly. Slowly draw the string up through the J-head. Filament material, as well as detritus, will attach itself to the guitar string.

Wipe it clean with your fingers, pull the string down through the extrusion opening and then again slowly draw the string up, allowing waste to attach to it. Wipe clean and repeat.

Vary from side to side the motion of the string being drawn up through the J-head so as to pry loose waste materials. After a dozen times or so, the head was clear.

If not badly kinked, save the string for the next time a cleaning is needed.

Hope this helps -

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