Taz Workhorse - Filament Grinding

Hi - I just bought a bunch of FilamentOne Premium PLA Pro Select after it was highly recommended on Reddit, and they were offering a discount for the 2.85mm. I’ve been trying to print for about 16 hours/day the last two days with the new filament. It keeps stopping randomly after about 30 minutes to an hour with the filament jammed (feeder ground a hole in it). I tried lowering the retraction settings and lowering the print heat. I checked and the fan on my workhorse is still spinning for the hot end heat sink, so I don’t think that’s the issue. I don’t have a good way to measure the temperature for temperature creep on the cold side of the hot end, it is possible that is contributing. This is a second hand printer that I already had to tear apart the head on once to fix an issue with the nozzle and heat block.

The filament recommends 195c to 215c, I’ve been using 240 with the eSun I was using previously without any issues like this. I see people that made 80mm and 120mm fan shrouds to make them replace the 40mm. Do I need to do something like that?

The first thing I would do is print a temperature tower. If the recommended temp range is 195-215 and you are using 240, then I think you need to verify that 240 is the best temperature. A lower temperature will reduce the likelihood of heat creep causing the issue.

PLA loves cooling so I have some extra fans blowing across the bed of my TAZ 6. I started with a small desk fan so no modifications to the printer were required. I now have fans mounted on the frame controlled by the Raspberry Pi running OctoPrint. I kept forgetting to turn the fan off for the first layer and/or on for the rest of the print so I have the RPi do that for me.

Which tool head do you have on the printer? Check the pictures at https://lulzbot.com/store/lulzbot-taz-3d-printer-workhorse-boxed-for-retail-na-kt-pr0051na?ref=KT-PR0051NA. Make sure the cold side fan is blowing into the heat sink.

If getting the temperature corrected doesn’t fix the issue and you want to try replacing the cold side fan, it should be a 40x40x10mm 5v fan. Noctua makes this fan which would be the simplest replacement and it should have more air flow than the stock fan. Noctua fans are sold in many places so just search for the part number.

I can’t imagine a scenario where 240c was the proper temperature for PLA, even with a hardened steel nozzle, I’ve never had to go above 215c. Any copper nozzles have been best around 205-210 for me.

Also, check the idler tension. PLA is very unforgiving with regards to pressure, and different formulations from manufacturers are going to go from having clean teeth marks from the gears to making dust in a turn of the tension knob.

Sorry, I realized my sentence was not clear about temps. I’ve tried as low as 195 the min recommended for this filament. I get better bed adhesion with higher printing temps. I have slowly been working the Z offset closer to the bed too, I’m using -1.24 right now and it’s not giving me a perfect first layer. I will try a temperature tower, but I don’t think it will finish printing.

I have the tension as low as it can go and there are still marks on the PLA. I am wondering if I should take the head apart again and see if something is loose or maybe out of alignment.

Try adjusting the z offset as it prints. In the 6 and mini, you can just hold the knob in for about 1/2 second during print and it’ll go straight to z-probe offset tuning. Just get eye-level with the bed and tweak it as it prints the skirt. You want the height of the bead to be just slightly below the nozzle. Mine is usually -1.32 for most materials, but your machine may be slightly less sensitive on the probe and need less offset.

There should be marks in the PLA, but if you’re making dust, it’s too much. Generally just start with the little silver indicator in the middle of the window, and work from there. Any buildup from a little bit of slippage is going to make slippage worse, so check those teeth before every print.

There’s an indicator for the tension? I usually just run it all the way loosened, I’ll look for that when I get home. I have an enclosure I’m using too. The last print fail made it through 3 layers on the octopus before stoping from grinding a hole in the filament this morning. I’m wondering if something is out of alignment. I’m also going to try oiling the filament with a filter to see if that helps. This filament seems softer than the eSun by a bit.

There’s a small window where you can see the spring, and the nut which the tensioning bolt runs through. When you turn the bolt clockwise, the nut moves toward you, allowing the spring to relax, decreasing the tension. When you turn the bolt counter-clockwise, the nut moves away from you, compressing the spring, and increasing tension on the idler.
tensioning aerostruder

Ah, yes, mine is turned all the way clockwise to the stop. I did try taking the front off my enclosure for a print as well. I will take the head apart tonight and see if I can find an alignment problem or something else wrong.

Alignment generally isn’t a problem with these, but too loose will slip easily, causing a little stripping, just as too tight will mash filament and cause stripping as well. Smashing filament takes a lot of the force from your motor, leaving less available to push/pull filament. Once you find the good middle ground, it doesn’t hurt to record the # of twists to full loose.

I really wish there was a M285 toolhead available, because dual gears just works soooo much better.

Oh, so you are thinking it could be too loose as well?

Yes, either too loose or too tight both lead to grinding.

Similar to how too hot can cause heat to creep up, causing filament to soften and bulge in the cold end, which causes plugging, which causes grinding. And too cold increases the pressure needed to push incompletely melted plastic through the nozzle, causes a bulge in the cold end, which causes grinding.

I’m trying printing again with it tighter than I’ve ever had it on the adjustment. I don’t put any additional tension when using the eSun. It seems to be printing okay, but I’m not going to hold my breath.

This successfully completed the print. The print peeled up from the bed on one of the arms of the octopus. I upped the temperature by 10c to 215c, the max they recommend on the filament. It made it through about 4 layers and then chewed a hole in the filament in the print failed. I think this is more than one problem, possibly heat on the cold end, and possibly tension issues. I think I’m going to try one of those Noctua 20m fans that someone linked in another thread. Bed adhesion seems to still be an issue. I lowered the z offset to -1.3 but I’m still getting some space between the extrusions? on the first layer.

I just looked back at your first post, and you say you had to tear apart the head to fix an issue with the nozzle and heat block. When you tore it apart, was it cold or hot? and when you put it back together, did you do it at full temp? I can imagine that there’s a slight gap between the heatbreak tube and the nozzle thread: (shamefully re-using somebody else’s illustration here)

If it makes it to layer 4, it shouldn’t be anything with z offset that is causing stripping of the filament. Are you using Cura or another slicer? Can link us to the file you’re trying to print?

Can you post a picture of the bottom of the print? There should be visible lines between the extrusions, but not space between them.

Hi, here’s a picture of the bottom of the two prints I tried last night. Note the extreme stringiness on the first one on the left that finished was due to me lowering retraction settings in Cura, which have been reverted to default. I’ve tried multiple different settings of tension on the feeder, the only thing I haven’t tried is tightening it even further from where it is. I tried stepping it up slowly and retrying prints. The second print on the picture is the one that failed after adding 10c to the print temperature.

In regards to the bed adhesion issue, the bed has been cleaned with dish soap and rubbing alcohol, but is a brand new layer of PEI I put on the bed within the last month. The PEI was missing entirely on this printer when I bought it. This PEI sheet is substantially different in feel to what is on the Octograb that came with the printer which I was using taped to my glass bed for a while (this was crushing the filament flat during printing on the bottom but adherence to the bed was OUTSTANDING).

Edit: this is the default octopus model from the Lulzbot team. I am using the latest Cura Lulzbot 3.6.36.

Thank you for the diagram. When I assembled it, it was hot, over 200c. I have printed multiple entire reels (1kg) of eSun PLA without this issue (grinding) since I re-assembled the hot end. The only thing that I am aware of that is not perfect is the hot end heater is about 5 degrees from perfectly aligned in the pictures. I can try heating it up and try to confirm everything is tight still, but nothing has moved, and there is no leaking filament (I was having this problem before).

Since you said that you took your tool head apart, it is possible that you installed the heat sink fan backwards. If the heat sink fan is installed backwards (you will be able to see a sticker), than it will not cool the heat sink enough and cause heat creep.

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The fan is pulling air from the outside and pushing across the heatsink. The fan is oriented like this:

Edit: I’ve tried further adjustments to the filament tension. All octopus prints tonight have failed before finishing the legs entirely.

Edit2: I just disassembled the print head. The drive motor for the feeder is extremely hot, I’m guessing 140F or so, and that was after it was not feeding for about 2 or 3 minutes. That seems hot to me but not sure, could the heat problem be coming from the drive motor into the spline that drives the filament?

I just disassembled the print head again, here are pictures:

Z offset is too high on both of those rocktopi.

Just re-looked at the pictures, and those thermistor wires look sketchy. It wouldn’t hurt to replace - 100k Semitec NTC Thermistor | Thermistor for 3D printer | LulzBot.

Another thing to check is the filament path before the toolhead. If you’re running through tubing and there’s a tight radius, the filament may be rubbing enough to be a problem.

If it was 140F when printing, I wouldn’t be concerned, but after a few minutes, it shouldn’t be that hot. Nema 17 motors are quite cheap and easily replaced, so if you have a spare, throw it on and see what happens. If you don’t have a spare, the LDO motors from lulzbot.com are fairly well-priced and are plug-n-play - Half Height NEMA 17 Stepper Motor, LDO | LulzBot. Before buying a new one though, run the print without any filament and see if your motor is getting just as hot.

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Just to be clear, by too high, do to mean it is too far above the bed as in the number is not negative enough? I believe these were both printed at -1.3.

I do have a filament tube between the guide point outside the enclosure above the reel and the print head. I was debating trying to pre-lube that to see if it helps, or removing it. The printer didn’t have one when I got it, maybe that’s why.

I moved the filament to the top of my TAZ 6 and don’t use a tube.

The enclosure has a long slot in the piece between the top frame rails so the filament has a pretty much straight shot into the top of the tool head.

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