TAZ Pro Filament Error

Recently my TAZ Pro has started chewing off the filament from the gear and generating a filament error. What purpose does the knob on the side of the extruder have? And are there any solutions to this issue? I have changed filament and the same thing keeps happening.

The knob on the side of each extruder adjust the tension on the filament “idler arm”. The filament feeds via a hobbed-gear … but the filament is pressed snugly against that gear with the “idler arm” (an arm with a wheel). The knob adjusts the spring-tension. If too loose, the filament can slip. If too tight, the teeth of the hobbed gear will dig in too hard and this can tear up the filament.

Ideally it should be maybe 1/3rd to perhaps 1/2 of the travel.

But another setting to check is your retractions…

The slicer software (e.g. Cura LulzBot Edition) has a few settings such as:

  • Retraction Distance
  • Maximum Retraction Count
  • Minimum Extrusion Distance Window
  • Minimum Retraction Travel

If you have a job where the slicer generates a lot of retractions without feeding much filament (lots of short segments of filament), then the printer ends up feeding, retracting, feeding, retracting, over and over the same little bit of filament. The sharp teeth in the hobbed gear end up tearing into the side of the filament until it digs a bit of a hole and just spins without the filament moving anymore (and then you have a jam).

So these settings let you tune the slicer behavior to avoid excessive retractions that would result in a jam. Here’s how they work.

  • Retraction Minimum Travel:

Suppose you set this to 2mm… this means that if the printer needs to end one segment of extrusion move LESS than 2mm before beginning another segment, then it wont even bother to retract (but this means you would likely get some stringing). I often set this to a value of about 1mm. This can result in a massive reduction in the number of retractions but you really need to inspect the slicer (switch Cura to ‘Layer View’ after slicing) to see where it does these retractions. Moving without retracting can result in a lot of ‘stringing’ in the print. But I find that often the retractions will happen in areas that wont be visible (infill, support, etc.) and not in the ‘skin’ if the part. So if that’s where the retractions are happening then I don’t care about the stringing.

  • Retraction Distance:

This is how much filament will be retracted when a retraction occurs. For PLA on a direct-drive printer (such as ours) these are usually low values … say around 1mm … maybe as high as 1.5mm but seldom more than 2mm. If you under-retract you can get stringing. If you over-retract you can pull in air-bubbles (that heat and ‘pop’ … causing poor print quality as the gas expands). But using a short retraction amount also means that it wont tear up much filament on each retraction.

  • Maximum Retraction Count:
  • Minimum Extrusion Distance Window:

These two settings work together. Say you set the Minimum Extrusion Distance Window to 3mm and you set the Maximum Retraction Count to 5. This would meant that the slicer will count the number of retractions needed WHILE also monitoring how much filament is advanced. If it needs to retract MORE than 5 times BEFORE it manages to push 3mm of fresh filament through … then it will ignore any additional retractions (beyond the 5) UNTIL it pushes through 3mm of filament. The idea is that it wont chew up the same short bit of filament over and over (resulting in a jam) … but once it advances enough filament to get to a clean piece that hasn’t been torn up by the hobbed gear … it will resume retracting again.

In other words, these two settings let you allow retractions to occur as normal… unless the quantity of retractions in a short distance starts to get ridiculous … and then ignore them until you get back to clean filament where it will resume normal retractions again.

I used values that are reasonable for stuff like PLA… some other filaments need different values. I use PVA support material and that stuff is just stringy. It needs big retraction values and it tears up very easily. When I print with TPU (e.g. NinjaFlex) that stuff is also stringy and doesn’t respond well to retractions (so I do things like set the slicer software to ‘wipe’ along the infill to hide the strings.

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I just purchased 2 new Pro’s, have one setup and am consistently getting extruder 1 filament errors. It appears to be feeding just fine and I can ‘resume’ the project and most of the time it doesn’t have a problem after that but sometimes it’s error after error. Any ideas?

@JRE there is a wheel and encode that monitors filament movement (on the right side of the frame where you feed the filament into the teflon tube).

If, for example, the g-code calls for advancing 5mm of filament, the encoder also expects to see 5mm of filament. If it does not, it assumes the filament is slipping.

I did a filament change … as per usually removing the teflon tube from the print head so I could pull out the old filament and insert the new filament, but after the change I didn’t push the teflon tube back in place … after a few moments of printing it generated a filament jam error (because without that teflon tube in place on both ends you don’t get a 1 for 1 movement of filament (each millimeter of filament pulled through the extruder is matched by the same amount going through the jam sensor).

If your teflon tube is in place … check the encoder to make sure it is clean and rolling as the filament advances.

I seem to recall there is a menu to disable the jam sensor – if you aren’t able to resolve the issue. But I presume you’d rather resolve the issue. I have had a few jams … but they were either legit jams or my fault for not properly connecting the teflon tubes on both ends.

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Thanks for the quick response! I disabled the sensor and now I’m fine, I ran 2 TAZ 6’s for almost 2 years without a sensor and was fine with it so I figure I’ll do the same with my Pro’s. I just need to figure out how to disable extruder #2 with single filament prints, seems like wasted time for extruder #2 to go through a wipe and other things when it doesn’t get used.

@JRE to disable extruder #2 there are two choices that come to mind.

  • You can set the filament type to “No Material” on extruder #2 … but it will still perform the nozzle cleaning (and since the nozzle clean warms the filament to back out a little before doing the wipe, it means you are slowly unloading the filament and after a few of those jobs in a row the filament would push itself out of the hobbed gear.)

  • The other option to create a new printer profile … basically a duplicate TAZ Pro printer… but manually edit the ‘Start’ g-code to disable all the steps that perform the wiping of nozzle #2.

There may be other choices that just don’t come to mind.

I am having similar issues with my Taz Pro print PLA, but the printer is not chewing the end of the filament. Instead it is digging a gouge into the filament about 75mm from the end. I followed your recommendations on Retraction Distance (set at 1mm), Retraction Minimum Travel (1mm) but noticed the Maximum Retraction Count is set at 99 and the Minimum Extrusion Distance Window is 2mm. The Maximum Retraction Count seems really high. Given your explanation of these two settings, if the 2mm of filament does not get fully pushed in, it is constantly retracting as needed until it reaches 99 times. That seems weird to me. You suggest 3mm and 5 times for these settings. Why would Cura default to 99?

I have also played with the location of the tension on the idler arm. I did increase the tension and found even more issues, so I backed off. But one thing I notice is that the filament is not easy to pull through the runout sensor, through the filament tube to the Titan extruder. Is it possible the tension on the runout sensor is too much as well? I never modified that but am wondering if that is too tight, causing too much drag. Oddly enough though, once the part is past about 10-20 layers, the issue goes away. Somehow I think this is a symptom of the underlying issue that I cannot resolve.

Any advice would be greatly appreciated.

Regarding retraction count. Suppose you don’t have issues with retractions, etc. so you don’t really to worry about retraction count. There is no setting to explicitly disable retraction count … so it’s just set to a really high value that will never be reached.

The need to be mindful of retractions depends on the part. When the printer is able to lay down many long printing moves … long enough that it’s always feeding a few millimeters of filament through the extruder before needing to do a retraction, then the hob gear isn’t go to forward and reverse and forward and reverse of the same tiny bit of filament … chewing it up. And on these occasions… it’s nice to put a limit on how many retractions can be performed on the same short bit of filament before you say enough is enough – and that’s what the retraction count does.

There are some techniques that I use to naturally reduce retractions.

Examples:

Infill pattern normally defaults to “lines”. Suppose you’re just printing a large cube and there is a lot of infill. The printer will lay down one “line” of filament and when it reaches the end of the segment, it stops printing so it can move to the beginning of the next “line” (a non-printing move). This means it would normally trigger a retraction.

But suppose instead of “lines” you choose “Zig Zag”. This works exactly like lines … except that at the end of an infill “line” it doesn’t stop printing as it moves to the start of the next infill “line” … basically the non-printing move gets converted into a printing move. The infill design will pretty much look the same since the printing move would be following the wall of the part (a cube in my example). This means it wastes a tiny bit of filament… but it didn’t need a retraction and this helps keep the filament moving through the extruder.

There is a “retraction minimum travel” value. This value is used to decide if Cura is allowed to skip a retraction. Here’s how it works.

Keep in mind that when your printer moves … it could move while printing… or move without printing (a non-printing move … this is what Cura calls “travel”). To the printer, these are really the same thing… a move is a move… the only difference is the speed and… whether or not the extruder was advancing filament while it performed the move.

So if we were to imagine the printer needs to make two different “printing moves” … with a non-printing move (a gap) between them… the “retraction minimum travel” (remember “travel” is a non-printing move) value asks… how far is the travel? If the distance of travel is not greater then the value specified, then Cura will not bother to retract the filament. (Mine is set to 2mm – but if I notice that a part has lots of tiny moves and filament might be getting chewed up … I’lll start increasing this distance and/or reducing the maximum retraction count value.)

But take care not to set a value too high… because not retracting means you can get some oozing (stringing) and this may affect the appearance of your part – it might not look as clean.

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WOW! That is really helpful. So the part I am printing is a “cradle” that is designed to hold a shield to become a face shield. The cradle has 5 attachment points that stick out from the brim, and two separate edges of the brim; lots of retraction and traveling as it fills in the individual attachment points. Based on your description, the printer is likely grinding into the filament constantly during the printing of these attachment points because once these are finished at about the 20th or 25th layer, the grinding stops and the printer runs to conclusion without issue.

That said, I attempted to change the Minimum Extrusion Distance Window to 3mm, but received an orange background in that entry. I always take that as a bad idea from Cura. So I left it at 2mm. I then dropped the Maximum Retraction Count to 5. Once the current print finishes, I will swap in the new gcode on my USB stick and see what happens. I hope this solves the issue.

On another note, I get this same behavior when I print the visors to my own face shield design. But, the error occurs when the printer is laying down the first 3-4 layers of filament and it is a solid flat crescent moon shaped part. The errors seem to occur when it reaches the middle of the crescent, which is the thickest of the brim to the visor. I would think the number of retractions was small, but who knows.