Is This Practice Clogging My Extruder?

[CCRN]

When I go to print, I extrude 20 mm of filament around 4 times just to be sure its running straight down and not a problem. I am using S3D to slice and octoprint to control the printer. I haven't had an issue until I bought a new roll of eSun PLA + in blue and tried printing with it. It stopped extruding mid print and would not pass any more filament. The screw just turned. Took the fans, filament drive, and extruder down and found a chunk of PLA stuck in the extruder pathway. Made sure the filament drive was clean of any sheared filament. Heated the extruder up and used an allen wrench to clear the path. Set the Z Height since I removed the extruder and then was able to print successfully. I put a new brass head on hoping to avoid issues in case it had a small clog.

Tried some different filament and the next print the filament again stopped mid print and would not pass filament. Repeated the above steps and this time the new nozzle was clogged. Torched my new and the previous nozzles to clear and I am no a third new nozzle and it seems like I am printing fine for now.

Wondering what I am doing to cause this!

Thanks,
Jerold

[Jules]

Nine times out of ten, the problem is in an incorrect Filament Drive Screw tension which deforms the filament so that it can't go into the top of the hotend. There is always going to be a wad of leftover cold filament inside the barrel and the nozzle when you take the hotend off of the machine. The stuff that is in there just melts the next time you heat up the nozzle and flows on out.

Try adjusting your filament drive screw tension. (Too tight is just as bad or worse than too loose.)

(If you've got one of the new smaller toothed gears, you have to also be careful to make sure the teeth haven't been clogged with bits of shaved filament.)

viewtopic.php?f=3&t=2694

[CCRN]

Here of some pictures of the front of the filament drive when it stopped extruding.

[CCRN]

The printer is running now and I see that bulge in the filament drive and filament is flowing. I think the tension screw is ok but will double check when the current job is finished in about an hour.

[Jules]

I'm not sure how fast you're printing, but you might need to slow it down. Are you pushing down on the filament when you load it? The orange filament looks like it is bulging out the front, and the blue one it isn't biting into the filament enough. You might have to tighten the tension BY JUST A HAIR. Too much is going to be just as bad, so no more than a quarter of a turn of the screw to tighten.

[CCRN]

RIght now the print speed for what I am working on is the default for S3D and the V4 extruder. It shows 4800 mm/minute. Does it look like the filament drive is pushing filament harder than it should? I did adjust the bite by 1/4 turn and it still is showing the bulge.

It is running a new print now and is adhering well. It would be nice to know why the filament is bulging like that. I can slow down the next print and see how it looks. What speed do people print PLA consistently at anyway?

Thanks,
Jerold

[Jules]

I print PLA at between 3200-3600 mm/min depending on whether I'm in a hurry or not. The machine can handle 4200 mm/min for PLA, but that is on the brisk side. If you're having trouble with stopping in the print, try slowing it down to 3600.

That bulge out the front bothers me - it's not normal. You're either trying to cram the filament in too fast, not giving it time to melt in the barrel, or you might have something out of whack in the filament drive - it's either got a space in there that lets the filament get out of alignment or it's not tight enough to guide it straight down.

Or maybe it's too tight to let the filament go down and it's buckling around the gear, but it's hard to tell from that angle on the photo - the orange filament bulge is blocking the view.

The blue filament looks like it's headed straight down, but isn't getting caught by the gear. It actually looks like two totally different problems.

Before you go changing anything though, check to see what it looks like after this print finishes. The filament should go straight down in a line, without being smashed much by the geared guide. That is supposed to just catch it and guide it straight down, not push it out the front around the edge of the gear.

[CCRN]

My last print finished fine with no stopping.

The filament drive teeth ring is positioned with a set screw. It looks like the ring may be too far back. Other than a few hiccups here or there, I haven't had any issues. Wondering if this ring of teeth was moved back when clogged it with eSun cleaning filament. It was a pretty nasty clog.

I wonder what the distance between the tip of the drive to the start of the ring should be to be in spec.

Thanks
Jerold

[Jules]

Check the integrity of the plastic filament drive if you had a really bad jam in there. (Look for hairline cracks or deformation, and check to see that the filament drive is still sitting completely flat (flush) against the stepper motor.)

That's a more likely issue from a bad jam than the toothed gear getting shifted, and the result is going to be the same. The jam might have deformed the drive just a little bit, or caused a crack to form, or pushed the filament drive out away from surrounding the little circle on the face of the motor.

(Probably wouldn't be a bad idea to print a spare drive to have it on hand if you don't have one already. If you are switching to ABS anyway you can knock one out with fairly high infill (60% or more) and keep it on hand for accidents.)

[sthone]

found a chunk of PLA stuck in the extruder pathway.

I use to get this a lot and it was from backing out the filament. When I use to reverse out the filament it would pull out of the extruder, stretch the filament a bit (because its still melting in the hotend) and then pull out the rest as it continues to retract.

It would kind of look like this coming out of the filament drive.

The way I prevent this from happening now is just to cut the filament I'm running above the filament drive (I use a 90° cut.) and the just hit extrude 100 and feed the next filament in while butting the to ends together. I hardly even retract filament anymore.