hot End getting plugged using abs regardless of manufacturer

[Agisis]

hello,
I posted earlier about my PID settings being reset on the EEPROM somehow, but resetting those and doing another attempt has not improved the situation. Basically, my hot end gets "plugged" with a cool part of ABS near where the filament goes into it. the lower half of the plug is molten, but the top part is cool. I have spent a lot of time ( hours and hours ) to little avail. I find what happens is that during retraction, it cannot pull the filament "Up" and out of the channel during retraction so the extruder just shreds the filament. this used to not happen in my hot end until a few weeks ago. No problems with PLA, just ABS.I have tried running it at 228, 230, 238 deg and nothing seems to help. It is as though the peek fan is doing too good a job and is cooling it off in the middle so much that it just turns into a hard rock.

Anyone else have this happen and did you find a solution?

[techstorage]

I had the Peek fan cool the hotend while printing, so I now wrap F4 tape on the hotend. You could use kapton tape also.

[teoman]

I am having a similar problem at the moment, sometimes the extrusion stops or it almost stops...

My hotend block is covered with some of the RTV that I bought for the kit. That did stabilise the temperature but did not solve the problem.

[Agisis]

I took all the tape off and have re-RTV'd it. One of the resisters had about 1/5th of an inch exposed so the heat may ahve been escapaing. A lot of the kapton tape had also come off so I'll reapply that tomorrow and see if it helps. It's like starting at the bottom tip, it is hot, hotter up higher, hotter up higher than that, and then suddenly cold and that is where the plug forms. The top screw where the filament goes in isn't even warm at this point.

[teoman]

The peek and upper parts should be as cool as possible as per the design.

[IMBoring25]

What retraction speed and distance are you using for your ABS profile? Except when the PEEK section of my SeeMe hot end was messed up and a couple of instances of fluctuating temperature, all my experience with jamming hot ends has been traceable to excessive retraction or excessive retraction speed.

[teoman]

4mm @40mm/s

[Agisis]

outside Perimiters at 40, infill 50
length on move is set to 5
filament/filament/Speed is at default which is 110mm/s

Oddly enough when i first built this, I was able to run it at up to 90mm/s speeds with 150mm/s filament speed, length on move set to 10mm! Now I can barely get the first layer of ABS down with some of the same settings. I almost wonder if somehow the inside of the hot end has become compromised somehow.

I'd like to add that this is happening even when I just sit and extrude 10mm using the extrude button. It flows out great until eventually it plugs up. Feeling stuck now.

[bot]

I'd just go ahead and buy a new hot end. e3d makes some nice ones.

[teoman]

I removed the nozzle and the heated everything up. There was some resistance. I think that the ptfe tubing inside might have swollen a little bit.

I am searching how to replace that now.

[teoman]

The effect i am observing is this:
I bring the nozzle up to temp (236 degs) and i use the extruder wheel to push some filament down. A quarter if a turn is like butter. Then it starts to resist. I can still push it but much much slower, if i wait a few seconds I get the buttery effect again.

When i removed the nozzle and the bowden tube, and was pushing a filament i could also feel some resistance from the ptfe tube inside the hotend. When everything was removed it was not that bad but still i thought it was high. There definitely was some kind of extrusion going on. I.e the filament was rubbing on the ptfe tube and melting and then being able to pass by.

[Agisis]

I may have found that I have compromised me PTFE tube. I pulled a plug out of it this morning (straight up at a lower tempterature) and the top of the plug is at 4.05mm, but the lower half of the plug is at 3.96mm. So, it is creating a wedge shape. That does not seem correct to me since I would assume that the tube is supposed to be the same diameter the entire length. That would cause it to overflow upwards and then form a plug. I'm going to take the whole hot end apart

[teoman]

you pulling the plug out can distort its shape



carefull for the peek section, some have managed to break it while trying to disassemble their hot end.

I asked on another thread, and you can remove the nozzle and you can see the ptfe tube inside. It can be pulled out with a pair of needlenose pliers, i think it should be ok to insert a fresh piece of ptfe tube in the same way.


Ill will try to give it a go, but I do not live in the USA so i am extra cautious, if i brake anything that is 20-30 days of down time for me.

[Agisis]

OK, so I think I may have fixed the glitch. I was reflecting on a comment you made earlier about it needing to be cooler up higher. I noticed that I had put a lot of kapton tape right below the PEEK section (right up to the first part of it) and it was like 6 layers thick. I think that was insulating it too much from the PEEK fan, so the temperature was too high up there. Over time, I think I damage the insides there removing the plugs, so the goal was to keep it from being melted that high up. I removed 1/2" of kapton tape, fixed any slack in my bowden tube, and then noticed something else.....My extruder just didn't seem to be able to dig into the filament. I cleaned the gears to no avail so I wonder if this filament in particular is just really tough. I clipped off some popscicle sticks and put them under the spring to put a lot more pressure on the filament and that seemed to really help a lot. Before, it wouldn't even catch despite be pressed right up against the gear. Maybe my gear is worn out? Does that happen?

[teoman]

I have some gray abs that also does not have any traction atall.

Try removing the nozzle and pushing the filament manually.

[Agisis]

false alarm. not fixed. I tried 3 different types of ABS, all same result. the moment retraction starts, it plugs up. I can only think there has been a integrity failure in the hot end at this point since nothing else changed that I am aware of.

[IMBoring25]

I won't say this will fix it...I won't say this won't make it worse...But when I had the symptom of resistance to pushing the filament through even with the nozzle off, I ran a 2mm drill bit up the PEEK section, taking several bites at it and always turning the drill forwards, then flushed potential swarf by running filament through it in both directions. After putting the nozzle back on and reassembling things, I have not had a recurrence.

[teoman]

That is very doable, as the next stage is replacing that part. (Ptfe hose)

Technically you ran a drill through the ptfe hose inside the peek section.

Did you run the drill bit manually or with a drill?

[geneb]

Just replace the PTFE liner in the hot end.

g.

[IMBoring25]

I used a drill but suppose you wouldn't have to.

[teoman]

You can remove the nozzle and yank out the ptfe, can it be pushed back inthe same way?

[Agisis]

Guess I'l find out. I found out last night that my wife bought me the Prometheus hotend for Christmas, but felt so bad for me struggling that I got my main Christmas present a few weeks early. I had to order the proper mount and supports from TrickLaser, but at a minimum I'll have a new hotend. While I am waiting for those parts to arrive, I'll see if I can take the PTFE out. I don't know if I have any extra laying around though to replace it. One way or another, I'll find out.

[teoman]

Cut a pieceof the bowden tube.

It is extra long as supplied.

I had asked guanu during purchase where i could get that material and he confirmed that it was the actual bowden tube.

[teoman]

45.1 mm is what it should be (dont take my word onit, there is a recent thread with exact value, ill post it ince i am not on mobile)

[Agisis]

Will to. I believe I kept the extra when I first built it. Thanks so much. Let's see how this goes. I'll still upgrade to the Prometheus my wife got me, but I want to find out if this will still fix it.