Nozzle Jams on Long Print

[pyronaught]

I've never had nozzle jams until just this week while trying to do a big print that takes about 30 hours to complete. With ABS at 260 I got about 24 hours into it before the jam. With PETG at 265 I got about 16 hours into it before the jam. Another PETG attempt jammed mere minutes into the print. All three were using the V4 nozzle and both had PETG running through them from previous print jobs. I think Jimc said somewhere that PETG leaves a coating in the nozzle that builds up over time, could that be the issue? At this point three of my five machines are down due to clogged nozzles.

[insta]

I'd blowtorch the nozzles and replace the PTFE liners at this point. Both are ridiculously cheap.

[Jules]

PETG leaves a coating in the nozzle that builds up over time, could that be the issue?

The one that is most problematic is PLA. PLA is a very low temperature melt, but at higher temps, (like the ones that you use printing ABS or PETG), the PLA will carbonize and bake into the nozzle, and eventually it will reduce the diameter of the hole if you get enough of it baked on. (It's sugar. Think of your mom's baking pans when you burn oil or sugar onto it - you can't dislodge that blackened coating with a hammer and chisel. )

PETG strips more often than it jams. It's flexible, and you have to have the filament drive screw tension set just right, check for stripping first any time the machine "jams".

And always test and reset the Filament Drive Screw Tension any time you change the type of filament.

Actually, if you haven't been using cleaning filament all along, you might need to blast those nozzles clean with a torch and start fresh. (Or pick up a few spares - the nozzles are cheap enough to keep half a dozen on hand to use while you clean out the current clogged ones.)

The problem really isn't in the V4 nozzles - I've gone months at a time, with dozens of filament switches, and haven't clogged any of them yet. (Got close a couple of times.) But I'm fanatic about using the cleaning filament and making sure that the tension is correct. Or you can just torch 'em. It's quicker.

[pyronaught]

I was thinking filament tension screw loosening too-- that's the only factor that I can see being related to the length of the print time. I've printed tons of ABS and never had a nozzle jam on me, but never printed a part that takes 30 hours to do. PETG I've only recently started using so I don't know what to expect with that stuff yet. This part has a lot of tapered edges, so there is a lot of short and fast back and forth movements that shake the printer and could loosen the extruder tension screw, and it was pretty loose at the time the feed stopped. There just is not enough back pressure from that plastic arm to do the same job a lock nut or lock washer does. I'm going to try and sub out the nut with a nylon lock nut to keep it from loosening like this.

[Jules]

I was thinking filament tension screw loosening too-- that's the only factor that I can see being related to the length of the print time. I've printed tons of ABS and never had a nozzle jam on me, but never printed a part that takes 30 hours to do. PETG I've only recently started using so I don't know what to expect with that stuff yet. This part has a lot of tapered edges, so there is a lot of short and fast back and forth movements that shake the printer and could loosen the extruder tension screw, and it was pretty loose at the time the feed stopped. There just is not enough back pressure from that plastic arm to do the same job a lock nut or lock washer does. I'm going to try and sub out the nut with a nylon lock nut to keep it from loosening like this.

Sounds possible, those things can sure shake, rattle and roll on tight infill. Do you have some of insta's Nema17 dampers on the machines?

[jimc]

That coating and layering buildup you get when switching filaments really applies to the v3b hot end. The newer hot ends are all ptfe. I know when i switched from v3b to the e3dv6 those issues went away

[ednisley]

filament tension screw loosening

I think filament diameter variation probably matters more, because the stock filament drive depends on that plastic arm holding the idler bearing to act as a spring, which it really isn't. When you're running tens of hours of filament through the drive, it's bound to have a narrow section in there somewhere.

I think diameter variation interacts poorly with the newer fine-pitch drive gear, because it bites into the filament much less than the older coarse-tooth gear:
https://softsolder.com/2016/04/14/maker ... 1-1-0-rc5/



Conjuring a longer screw with a stiff compression spring might be a worthwhile experiment; you'd want to tune the spring for similar indentations as with your favorite "tighten the screw" setting.

A while back, we kicked around a drive design with a spring and maybe a metal arm for the idler bearing, but (alas) nothing came of that. I'm

[jimc]

Actually if i print my filament drive at 80-90% infill, i dont even need the screw at all. There is enough stiffness in the plastic itself to grip the filament perfectly. With no filament in th drive i turn the screw eith my fingers so it just touches the arm and thats it

[pyronaught]

Anyone ever try Maker Geeks filament floss for cleaning nozzles?

http://www.makergeeks.com/exflsehounmu. ... 1466431686

[pyronaught]

I'd blowtorch the nozzles and replace the PTFE liners at this point. Both are ridiculously cheap.

Is the PTFE a generic part or is that one of the unlisted items you have to call Makergear over the phone to buy?