pla constantly jamming in hotend

Hi folks,
just got my first roll of pla to play with.
I've gotten one 20mm hollow cube calibration print out of it and now
it is constantly jamming right down in the hotend.

I've run it at 200-210. My hotend is a custom job with a stainless throat,
30mm fan on the heatsink. This is my normal abs hotend with a fresh
0.3mm nozzle on it. It was extruding at <15mm/s

If I manually force the filament, sometimes that works and I see steam.
Othertimes I have to retract, then pull the filament out, trim it and then
manually force it through again.

I'm pretty sure this is simply a newbie mistake but would rather not have
to go through half a roll like I did learning with the abs.

Would switching to a hotend with full ptfe lining work better?
Suggestions?


Andrew

PLA and steel are a bad combination, they stick very goog to one another.
Also make sure that no heat creep happens. Use a small (<2mm) retract and good cooling of the hotend.
In general PTFE inliner hotends are preferable for PLA

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[www.bonkers.de]
[merlin-hotend.de]
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Steam? PLA is hygroscopic... it absorbs water from the air. That water then turns to steam inside the nozzle, causing problems. Perhaps you need to dry your PLA before printing?

Do you have the dimensions for your custom hot end? I would like to compare it to lets say, and E3D v6, just so we know what kind of structure it has.
Also, try raising the hot end temperature and make sure that the thermistor is reporting the correct temperature to the control board. Even so, you may have to print at a higher temp due to thermal differences in where the thermistor reads the temperature, and where the plastic needs to melt (where it matters).

Edited 1 time(s). Last edit at 03/07/2016 10:34AM by Montiey.

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Master Tinkerer

I'm running at 180c. Using a stainless throat and nozzle on my Prometheus V2 and have never jammed. It does use a PTFE tube.

Well,
I've done ths tenp raise and didn't solve it.

Switched over to my all ptfe hotend and oiled up some
filament and the problem has completely vanished.
Well except when the nozzle was jamming due to extruding
too fast. Forgot that happens,

I just hope i wont have to keep oiling the filament.

FWIW, I don't need to oil my PLA filament going into a PTFE-lined "E3DV6" clone.

I wondered about that oil too. Might be the problem.

1. Teflon does not like all oils, a lot will make the teflon to expand or soften over time.
2. For PLA there should be no transport or jamming issues at all.

PLA is very slippery on most materials, including metals.
I my years of printing I only found two causes for transport problems with PLA that are not related to bad hardware.
The first is filament damage or deformation due to too much pressure on the extruder springs.
The second is the roll diameter - PLA should be sold on much bigger rolls and not these tiny diameters.
As it is very stiff and especially towards the end of a roll PLA tends to curl up with great force.
This means wherever there is gap, corner or anything else to get stuck it will get stuck sooner or later - this is what I call bad hardware.

I think I made similar suggestions before but let's do it again
First you should check if the jamming is filament or hardware related.
1. Remove the hotend.
2. With the electronics off, turn the extruder wheel by hand and check the filament when it comes out.
Cut a piece off and compare to a fresh piece of filament.
Use calipers to check the roundness and you eyes to check for chew marks.
In a perfect world the filament will still be totally round and show very soft marks from the hobbed bolt.
If there are steps cut into it so it looks like a saw blade you have far too much pressure or a bolt that is too sharp and cuts into the filament - both is bad.
3. Adjust the extruder pressure so the PLA comes out unharmed.
4. Hold the filament firmly with your fingers and try to pull it back by turning the extruder wheel - it should be pulled out of your fingers but not slip in the extruder!
If you can only pull it back with so much force on the extruder so that the filament gets damaged then change your setup or at least the hobbed bolt.
5. Use PLA with some bad transport marks and best from the end of a roll to check how it moves through the hotend - for this you need a clean hotend with the nozzle removed.
6. Push the PLA through the hotend and check if you feel resistance.
The normal friction can be ignored, what I mean is to check if the filament will get stuck badly, you have to twist and turn it so you get the chewmarks into contact with all parts of the hotend.
If you feel it getting stuck bad twist it a few few degrees - if it frees and moves better you have a sharp edge or gap somewhere in the hotend.
If a badly curled PLA piece won't move through properly or only with great force but a piece from the start of a roll moves fine you need to straighten your filament - check the last part of this reply.
7. In case you found problems getting the filament through the hotend use some fine sandpaper on all metal hotends to smooth out the surface and remove sharp edges.
A few round on a bike spoke work great in a cordless drill
If you have to use a liner in a metal hotend consider getting a hotend in the right diameter without a liner!
Teflon liners are available in different qualities, some are quite soft while others can really hard, hard is best.
Also the diameter must be a perfect match for your filament and hotend, avoid liners if there nothing left anyway - a liner to get from 3mm down to 1.75 has just 0.625mm walls, IMHO too fragile.
8. Teflon liners need to be secured!
If your liner can move up and down it will form a cone in a short time, this cone will cause the filament to get stuck, especially if you use a lot of retraction moves.
Bad hotends for 1.75mm filament have been designed to be used with a liner as the actual diameter is 3mm - a 1.75mm drill is more expensive than a 3mm one
To avoid buying a new hotend you can try to drill out the coldend to 4mm - this will allow you to use a liner with much thicker walls and will prevent problems.

How to improve the PLA transport...
I no longer use PLA as my standard material as I prefer Nylon but back in the days I found a little cheat that helped me lot, especially once a roll came to the end.
Back in the day I used a bucket to roll up the last 25 or 30m of a roll.
Had a 75W reptile heat lamp installed in a small wooden box that was lined with aluminium foil.
With the help of a few slots I could vary the distance from the filament to the lamp.
While winding the filament onto the bucket it got straithened out from the heat of the lamp so the bad twist was gone.
Sure it looked a bit weird just hanging on a much smaller roll but the extruder was no longer struggling to get the job done.
Was always thinking of making a teflon lined heating rod with temp control to be mounted directly on the roll holder but then abandoned PLA LOL
But if there is interest I might build a prototype and post the instructions on how to include this into the firmware control so it can be adjusted while printing.

Cool,
Thanks folks

Quote
Downunder35m
1. Teflon does not like all oils, a lot will make the teflon to expand or soften over time.
2. For PLA there should be no transport or jamming issues at all.

PLA is very slippery on most materials, including metals.
I my years of printing I only found two causes for transport problems with PLA that are not related to bad hardware.
The first is filament damage or deformation due to too much pressure on the extruder springs.
The second is the roll diameter - PLA should be sold on much bigger rolls and not these tiny diameters.
As it is very stiff and especially towards the end of a roll PLA tends to curl up with great force.
This means wherever there is gap, corner or anything else to get stuck it will get stuck sooner or later - this is what I call bad hardware.

I think I made similar suggestions before but let's do it again
First you should check if the jamming is filament or hardware related.
1. Remove the hotend.
2. With the electronics off, turn the extruder wheel by hand and check the filament when it comes out.
Cut a piece off and compare to a fresh piece of filament.
Use calipers to check the roundness and you eyes to check for chew marks.
In a perfect world the filament will still be totally round and show very soft marks from the hobbed bolt.
If there are steps cut into it so it looks like a saw blade you have far too much pressure or a bolt that is too sharp and cuts into the filament - both is bad.
3. Adjust the extruder pressure so the PLA comes out unharmed.
4. Hold the filament firmly with your fingers and try to pull it back by turning the extruder wheel - it should be pulled out of your fingers but not slip in the extruder!
If you can only pull it back with so much force on the extruder so that the filament gets damaged then change your setup or at least the hobbed bolt.
5. Use PLA with some bad transport marks and best from the end of a roll to check how it moves through the hotend - for this you need a clean hotend with the nozzle removed.
6. Push the PLA through the hotend and check if you feel resistance.
The normal friction can be ignored, what I mean is to check if the filament will get stuck badly, you have to twist and turn it so you get the chewmarks into contact with all parts of the hotend.
If you feel it getting stuck bad twist it a few few degrees - if it frees and moves better you have a sharp edge or gap somewhere in the hotend.
If a badly curled PLA piece won't move through properly or only with great force but a piece from the start of a roll moves fine you need to straighten your filament - check the last part of this reply.
7. In case you found problems getting the filament through the hotend use some fine sandpaper on all metal hotends to smooth out the surface and remove sharp edges.
A few round on a bike spoke work great in a cordless drill
If you have to use a liner in a metal hotend consider getting a hotend in the right diameter without a liner!
Teflon liners are available in different qualities, some are quite soft while others can really hard, hard is best.
Also the diameter must be a perfect match for your filament and hotend, avoid liners if there nothing left anyway - a liner to get from 3mm down to 1.75 has just 0.625mm walls, IMHO too fragile.
8. Teflon liners need to be secured!
If your liner can move up and down it will form a cone in a short time, this cone will cause the filament to get stuck, especially if you use a lot of retraction moves.
Bad hotends for 1.75mm filament have been designed to be used with a liner as the actual diameter is 3mm - a 1.75mm drill is more expensive than a 3mm one
To avoid buying a new hotend you can try to drill out the coldend to 4mm - this will allow you to use a liner with much thicker walls and will prevent problems.

How to improve the PLA transport...
I no longer use PLA as my standard material as I prefer Nylon but back in the days I found a little cheat that helped me lot, especially once a roll came to the end.
Back in the day I used a bucket to roll up the last 25 or 30m of a roll.
Had a 75W reptile heat lamp installed in a small wooden box that was lined with aluminium foil.
With the help of a few slots I could vary the distance from the filament to the lamp.
While winding the filament onto the bucket it got straithened out from the heat of the lamp so the bad twist was gone.
Sure it looked a bit weird just hanging on a much smaller roll but the extruder was no longer struggling to get the job done.
Was always thinking of making a teflon lined heating rod with temp control to be mounted directly on the roll holder but then abandoned PLA LOL
But if there is interest I might build a prototype and post the instructions on how to include this into the firmware control so it can be adjusted while printing.

I have a similar problem, could you give me you opinion? Read my post: [forums.reprap.org]

Strange.
I'm getting the impression is that pla is fussier then abs.


Thanks everyone

Yes it is. ABS' weakness is the warping, but it's a lot easier to extrude.

Thanks to everyone helped with this.

Hi. I had a similar problem, read this (I found the solution today!), it might help you:

[forums.reprap.org]

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