Filament Not Getting Pushed Through Extruder & Nozzle

[jumi1174]

UPDATE: I think it may be a hotend temperature issue now. See post #4.

I know this seems like a common and easy issue to address, I thought so too, but I'm all out of ideas and need help from the community.

All of a sudden, my filament stopped being pushed through the extruder-nozzle assembly. The hobbed bolt began "carving" out a chunk of the filament line:


Seemed like a simple fix, either:
a) the idler springs were too tight
b) the hobbed bolt teeth were gunked up with filament flakes
c) the hot end / nozzle was jammed

I quickly eliminated (c) since I was able to manually push filament through the nozzle without issues; still, I removed the filament from the extruder and was able to run a thin guitar string through the nozzle opening all the way up through the extruder opening to ensure no major blockage was present. I then cleaned some flakes off the hobbed bolt and put it all back together with looser idler spring compression. The filament still got chewed up. I repeated the process until the idler bolts were so loose that the springs had no compression. Filament still got chewed up.

I cleaned the hobbed bolt again and figured that something must then be wrong with the hot end. I'm using a 3mm Hexagon. So I took the hot end completely off, put the filament just through the extruder, and was able to extrude and retract filament for long stretches (~0.5m) through the extruder using both the LCD and Pronterface with "normal" idler spring compression (not overly tight or overly loose); the hobbed bolt didn't chew up the filament at all other than the regular teeth marks.

So I figured I had some kind of blockage in the hot end that wasn't allowing the filament to melt and extrude properly. I had previously experimented with bambooFill and copperFill on that hot end, maybe something from those messed up my hot end.

I ordered a completely new 3mm Hexagon hot end, installed it, and got it set up. I brought it up to 250 C, let it sit for a bit, and manually pushed out filament; it all worked fine. I put the filament back on the hobbed bolt with normal idler spring compression: got chewed filament and no extrusion again...

I'm all out of ideas. I feel like I've tried every avenue of troubleshooting this issue, and I don't know what else to try. Other ideas I've seen mentioned haven't panned out:
- the gears on the extruder aren't slipping and aren't significantly worn
- there's plenty clearance between the hobbed bolt and x-carriage, so there's no friction or rubbing
- my filament spool has plenty slack

The only possible thing that is different from before the issue is that the filament I'm using now (White ABS from ToyBuilder Labs) is measuring ~2.9mm in diameter whereas my previous filament (Blue ABS from MakerFarm) was ~3.0mm. But I don't think that is the case because this issues sprang up all of a sudden; I was previously able to get completed and nice prints with the ToyBuilder filament before these issues occurred.

Any possible ideas? I'm not sure what else to try.

Thanks in advance!

[voodoo28]

Have you tried another filament after the jamming started? There is a good possibility that the filament is oval in certain spots.

[jumi1174]

Have you tried another filament after the jamming started? There is a good possibility that the filament is oval in certain spots.

That's the one thing I haven't tried since I don't have another spool of filament right now. I may have some old scraps though, so I'll definitely try that as soon as I can. Even so, when I measured the filament diameter with my digital calipers, they seem fairly round, so the eccentricity didn't jump out to me as being a big issue.

[jumi1174]

UPDATE: I think it may be a hotend temperature issue now...

I was able to get a hold of some old Makerfarm PLA scraps I didn't use. I heat the hotend up to 265 C, and I couldn't push the filament through at all. I pulled the filament out and ran a guitar string through the hotend to ensure there were no blockages; the string went through fine, no blockages.

So how can I verify my hotend is heating up to the temperature being reported?

[voodoo28]

you can do PID Auto Tune..


also make sure your heater cartridge is not loose and is centered as well as the thermistor.

[jasay]

Didn't see anywhere a mention of the hotend fan. Do you have cooling air running over the hexagon heat sink fins? If not, it will very likely jam when the heat travels up past the heat break. With cooling I can actually touch the heat sink fins for as long as I want even when the hotend is at 235ºC.