Filament grinding

A forum dedicated to the stock LulzBot TAZ 3D Printer
JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Filament grinding

Post by JRAlvarez » Sun Jul 22, 2018 3:21 pm

I've had my Taz 6 for over a year and it's been great. But lately anything I print that takes more then an hour or two fails due to the filiment getting ground away as it's turned. I'd done a fair bit of searching and see this problem happen for mutliple reasons, but I can't seem to nail down my problem.

I have tried mutliple different rolls and types of PLA.

I've done several cold pulls and disassembled the hot end to check for clogs. No clog found.

I have tried printing with the tensioner at various levels of tightness. I also checked to make sure that the bearing spins freely.

I had been experimenting with retraction settings, so I turned them way down. Still unsure of what settings changes I may have made incorrectly, I downloaded and started over with Cura lulzbot edition 3.2.21. Same problem. I next turned retraction off completely. Same problem.

Kind of at my wits end here. Any other suggestions?

Galadriel
Aleph Objects | LulzBot
Posts: 201
Joined: Mon Sep 25, 2017 10:23 am

Re: Filament grinding

Post by Galadriel » Mon Jul 23, 2018 6:24 am

Filament grind is commonly seen if the overall print temperature is higher than necessary, especially with PLA because it likes a fair amount of cooling. It's generally referred to as heat creep and basically what is happening is that the filament is heating up and softening along the length of the heat break until it reaches the hobbed bolt that pushes the filament through the toolhead. Then the hobbed bolt will just eat a chunk out of the side of the filament until there is nothing for it to grab and push. There are a few things that could be causing this if it is indeed heat creep. The first thing to check will be that the fan on the front of your toolhead that cools the heatsink is running, to do this just turn the printer off and back on keeping an eye on the fan to make sure it powers on with the machine. If that fan is turning on as expected you could try adding a small desk fan or possibly turning down your print temperature slightly. What brands of PLA have you tried? What settings were you using to print? Could you post a few photos of the filament removed from the toolhead after a failure, as well as some of the failed prints? There are some visual hints to the various causes for filament grind and getting a look at what things are coming out like should help narrow down what's happening here.

JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Re: Filament grinding

Post by JRAlvarez » Mon Jul 23, 2018 10:47 pm

The fan does power on when I turn the machine on.

Doing a test now with the temperture turned down to 195. I use alot of Inland and Polymaker. See pictures below.

After starting over with the latest version of Cura and it's base settings I tried a Rocktopus
Rocktapus.jpg

JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Re: Filament grinding

Post by JRAlvarez » Mon Jul 23, 2018 11:48 pm

Then I tried a smallish item that would take 4-5 hours to print.
TM.jpg
Success on both! Not perfect but not failures.

JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Re: Filament grinding

Post by JRAlvarez » Mon Jul 23, 2018 11:48 pm

So then I tried a very large item, something that would take 8 hours plus.
Fails.jpg
Tried it twice as you can see. These failed about 1-2 hours in.

JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Re: Filament grinding

Post by JRAlvarez » Mon Jul 23, 2018 11:49 pm

Filament.jpg
The purple pictured here is the polymaker, The gray is Inland. I have many other failed examples, but they basically look the same and came from many different rolls, as this problem seem to slowly ...creep...up on me, and didn't happen all the time, at first.

Also of note, In december I got a Printed Soild enclosure. I didn't think it was part of the problem as I was printing fine for months. Just FYI.

I'm doing a test now, medium size item, 195 degrees, no enclosure.

JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Re: Filament grinding

Post by JRAlvarez » Tue Jul 24, 2018 12:01 am

Latest test just failed. About an hour or two in. Left the enclosure off, printing at 195 degrees, and while I didn't have a small fan to point at the printer, the room does have a ceiling fan going. I'll see about bringing a small fan from work tomorrow.

Also, I opened up a brand new box of Inland brand PLA. To insure moisture isn't part of the issue. But I do live in California, so humidity isn't often a thing here.

Galadriel
Aleph Objects | LulzBot
Posts: 201
Joined: Mon Sep 25, 2017 10:23 am

Re: Filament grinding

Post by Galadriel » Tue Jul 24, 2018 7:31 am

Are you using the stock settings aside from temperature or have you made other adjustments in addition to the experimenting with retractions you initially mentioned? Also since your other models all came out well I have to ask, have you tried a variety of larger models or have you just been experimenting with this particular model?

JRAlvarez
Posts: 22
Joined: Fri Sep 08, 2017 8:14 pm

Re: Filament grinding

Post by JRAlvarez » Tue Jul 24, 2018 7:44 pm

Galadriel wrote:
Tue Jul 24, 2018 7:31 am
Are you using the stock settings aside from temperature or have you made other adjustments in addition to the experimenting with retractions you initially mentioned? Also since your other models all came out well I have to ask, have you tried a variety of larger models or have you just been experimenting with this particular model?
That was why I downloaded the newest version of Cura lulzbot edition. I wondered if I had changed something and wanted to start fresh, to ensure that I did that I deleted everything and installed fresh. It was from that install and those stock settings I printed the items pictured above.

I've been experimenting with lots of different models. The same situation seems to persist, anything that takes 2 hours or more tends to fail like the above examples.

mwester
Posts: 46
Joined: Sun Nov 26, 2017 8:02 pm

Re: Filament grinding

Post by mwester » Tue Jul 24, 2018 7:49 pm

Is there anything in the environment that may contribute to higher-than-expected temperatures around the extruder? What is the ambient temperature in the room by the printer?

Things to consider:
- Is the printer in direct sunlight?
- under or near a warm-air vent?
- In an enclosure, a closet, or a very small room with little or no air circulation?

Preventing heat creep depends on that little fan blowing cool air on the extruder heat-sink, and if the air that it is blowing is warm enough, the printer may be working as designed but still be unable to keep the temperature of the extruder and filament low enough to prevent heat creep.

Edited to add: Consider this thought experiment -- PLA has a glass transition temperature (the point where it softens) of about 140 degrees F (60 C). The goal is to keep the top of the heat sink below that temperature. If the ambient air temperature is 100 degrees F (in an enclosure, or closet, perhaps), then the differential between the air and the maximum temp is a paltry 40 degrees F. But, if the air temp is held at about room temperature (70 degrees F), that differential jumps up to 70 degrees -- a considerable difference when cooling.

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