Ender 3 Pro Filament extrusion problems

  • I run quite a few Ender 3 Pro's using the same slicer settings (Simplify3D), and just recently I have noticed a very odd extrusion problem.

    I find that at about the same height on several printers the printer under extrudes by quite a margin. After that, it either continues to under extrude for the rest of the print or it will go back to extruding proper amounts of filament with no problem. This destroys the print and makes it both structurally weak and defective. I am wasting quite a bit of PLA trying to fix this problem so any help would be appreciated.

    Here is what I have done so far:

    • I first made sure that the hobbed gear is clean.

    • I tried extruding the filament with a very hot temp (240C) there were no problems here and the filament extruded fine albeit, it was not on the bed, just extruding into the air to see if the problem was heat.

    • I tried the same thing as above but with a low temp (180) this also proved just fine again extruding in the air.

    • I calibrated my E steps per mm, those are fine and accurate.

    • I tried increasing my flow rate to 118%

    • I tried switching to a different nozzle

    • I tried switching to a different hobbed gear

    • I tried switching the mechanism that pushes the filament up against the hobbed gear

    That's about it. Not sure where to go from here so if anyone out there can think of anything I missed, I would love to hear it!

    EDIT 1:

    As per @fred_dot_u asked, the elapsed time at the layer of failure is roughly four hours in. I have also attached a picture of one example of this kind of failure below. I would also like to mention that this is happening on several of these printers as I have 18 printers running in one room. Our current theory is that the power draw is simply too high and so the printers are not getting the heat they need, however, the thermistors still register a solid 195C on my printers that are currently running.

    side of building with layer underextrusion

    EDIT 2:
    Here is another picture of a different model with the same layer failure problem but at a lower layer height. This model was printed along with 11 other identical models on the same bed, all of which failed at the same height.
    Model with layer failure at a different height

    Hi and welcome to SE.3DP!

    Can you assign a particular elapsed time to the problem you are experiencing? This question is founded on an overheat possibility of your extruder but that is not a certainty, merely one other aspect to check.

    @fred_dot_u I'm not entirely sure what you mean, but I edited my question to answer what I think you are asking. Please feel free to let me know if that is not what you were looking for.

    Is the Z position of the failure consistent? What are your print speed settings? Layer height? It may be that due to acceleration limits and geometry of the sliced layers, you don't achieve the top speed until this layer, and that the top speed you've set is faster than the printer can extrude. Also what are your retraction settings? It could be lost material due to travel without retraction.

    @R.. The Z position failure is not consistently the same height, but is generally pretty close (within a few millimeters between prints and between printers). I have these models printing at 3600mm/min with a layer height of .2mm with a .4mm nozzle. I have my retraction speed at 3400mm/min with a retraction of 8mm, no restart distance, and no vertical lift distance. I have the nozzle coast for 1 mm and wipe for 3mm.

    Have you tried disabling coasting? It fundamentally underextrudes, and the effects will be cumulative and dependent on the particulars of how the slicer orders the lines to be extruded. You should not need coasting unless you've disabled retraction for some reason; it's a hack that's a poor substitute for what linear advance does on printers that support it.

    Also, 3600 mm/min (60mm/s) might be too high a sustained extrusion rate. At your layer height and nozzle size, it comes out to 4.8mm³/s, which might be faster than the printer can keep melting material. This would be consistent with my theory that the problems start when you get to layers that happen to have enough straight linear motion that the printer has time to accelerate up to the full speed before turning a corner.

    @R.. Alright, I will adjust settings in the next print and let you know the results tomorrow. I will adjust down to 2400mm/min and disable coasting. However, even if I do change these settings, they are still working on some of my other printers. Not sure why though.

    Good luck. Let us know how it turns out. If these ideas turn out to be helpful I'll write up an answer explaining why.

    As it concerns similar heights for various printers, have you checked the spool to extruder feeding? Could be that the filament kinks at the same height over and over.

    @0scar I have not checked that, but I will monitor that closely on the next few prints.

    @R.. So the print has worked beautifully! I think the speed was critical in this matter which is unfortunate time wise but a solution nonetheless.

    @DanielBozarth: Great to hear! You might actually be able to decrease the overall print time, while keeping the max speed lowered, by relaxing (increasing) the acceleration/jerk limits. Most of the time printing an object with fine details/sharp corners is spent moving *a lot* slower than the max speed, which is why you weren't hitting a problem with extrusion rate keeping up until you got to layers where it did reach speed.

    @R.. Alright sounds great, I think I will ask another question about good acceleration and Jerk settings but for now, what you said earlier is the answer.

    @DanielBozarth:I already put some in my answer. :-) But indeed it's not complete and advises you to experiment, so a question about the max accel/jerk the Ender 3 can handle, or about how to conduct experiments to determine this for a printer, would be nice.

  • There's a known issue across Creality printers with the PTFE tube (bowden) slipping in the coupler on the hotend side, allowing molten material to push back around/up inside it rather than making it out the nozzle. I haven't experienced any such problem myself, even after applying some fairly serious abuse to that part of my Ender 3, but this video from CHEP claims it was the source of his problems and explains the issue well.

    I believe my Ender 3 came with an extra replacement for this coupler; if yours did, and this seems to be the problem, you can see if the second one they supplied is better. Otherwise it's an easy component to source third-party replacements for.

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Content dated before 7/24/2021 11:53 AM