Movement is stuttering. Appears to slow printing down



  • I'm having an issue where Cura say's my print should only take 25 minutes, yet it's actually taking 47.

    I can only narrow it down to my movement stuttering so much. In this video below, you can see that when printing one circle, the print head flys round, but then on the next it stutters like crazy. Cura shows this as just a nice clean circle, no infil, so i dont see why it needs so much stop-start.

    https://streamable.com/isxgf

    From what I can see, my jerk/accell settings are set higher on my duet config than my cura settings so shouldn't me limiting it.

    I've attached my gcode file0_1541098291369_CFDMP_80.gcode (which has all the cura settings at the top. I cut out a bunch of the middle to keep the file size under the 4mb limit) and my duet config0_1541098165812_config.g

    If someone has any idea I would be very greatful!

    Many thanks in advance



  • Your extruder jerk is quite low at 120mm/min

    Do you have cura set to reduce line width or flow rate for thin perimeters? I've seen it behave oddly when that's enabled. It seems to pulse the extruder in order to get a lower average flow.



  • I'm sure I left the extruder jerk at default? what would be a better value for testing? That may very well be my issue

    Thanks



  • Try 1200mm/min



  • nope 😞 Doesn't seem to have made any difference. Shall i try it higher maybe?



  • I'd try slicing with a different slicer and testing again. Maybe even just a small cross section of the part to see if you can duplicate the stutter.



  • I'll try that tomorrow when I get in from work. Thanks for your help!



  • The inner walls appear to contain a real mixture of line segment lengths, some are really small. I see you are using pressure advance. I think maybe that combination has been reported to cause problems before now (not certain, just a vague recollection). So you could try disabling the pressure advance.

    However, the fact that the outer walls don't seem to have such variation in line segment length makes me think that Cura has screwed up somewhere so I shall investigate that.



  • @phaedrux I'm very interested in this. I have a Zesty Nimble and the documentation says:

    "RepRap Firmware: 0.6mm / sec
    M566 should have E value set to E40 (as it is set per minute)"

    and they also suggest not fiddling with this too much.

    With a 0.6 volcano nozzle I'm mindful that the standard advice doesn't apply.

    I am still experimenting and its seems M566 E 100 - 300 is the likely range for print quality and apparent speed although speed on infill seems low which is why I tried values higher than M566 E40. DC42's formula in a pressure advance discussion, for PA 0.10 secs (which is about right for my printer) gave me M566 E2000 with M201 E340 so I thought there is something wrong somewhere. E2000 wasn't good in print quality !!



  • Hello @Asdasd1234 , could you please save the Cura project for that print and attach to this thread? I would like to try slicing it myself to see if I can recreate those short line segments. Thanks.



  • Hi, it should be attached now. I've tried with and without the thin walls being on and it makes zero difference to the print time or the stuttering
    https://drive.google.com/file/d/1Od4A0c_NOH5hUTV8xDeujaesBHcyCbso/view?usp=sharing

    thanks



  • @burtoogle said in Movement is stuttering. Appears to slow printing down:

    The inner walls appear to contain a real mixture of line segment lengths, some are really small. I see you are using pressure advance. I think maybe that combination has been reported to cause problems before now (not certain, just a vague recollection). So you could try disabling the pressure advance.

    However, the fact that the outer walls don't seem to have such variation in line segment length makes me think that Cura has screwed up somewhere so I shall investigate that.

    Turning off pressure advanced sped it up a massive amount!... But I would like to have pressure advance running 😞 Is this a known bug/incompatibility or is there a workaround?

    Many thanks for your help so far though!



  • @asdasd1234 said in Movement is stuttering. Appears to slow printing down:

    @burtoogle said in Movement is stuttering. Appears to slow printing down:

    The inner walls appear to contain a real mixture of line segment lengths, some are really small. I see you are using pressure advance. I think maybe that combination has been reported to cause problems before now (not certain, just a vague recollection). So you could try disabling the pressure advance.

    However, the fact that the outer walls don't seem to have such variation in line segment length makes me think that Cura has screwed up somewhere so I shall investigate that.

    Turning off pressure advanced sped it up a massive amount!... But I would like to have pressure advance running 😞 Is this a known bug/incompatibility or is there a workaround?

    Many thanks for your help so far though!

    It sounds like your extruder instantaneous speed setting (jerk) is too low. That will cause problems with pressure advance.

    Edit. Just looked at your config and see that you have it set to 120 mm/min which is really slow. That will slow everything down and is likely the cause of all your problems. I don't know what extruder you are running but I use 3600 with my Bondtechs and former Titans.



  • I changed it to 1200 following some advice above but it made no difference. I will try 3600 now though, and higher if needed to see if it starts working before other issues arive from it being too high. Thanks



  • @deckingman Just try to get my mind around this - I am still getting familiar with useful reasonable ranges for various settings.

    At Jerk E3600 you are effectively disabling extruder acceleration for most extruder movement (< 60mm/sec), and effectively replacing all acceleration for the acceleration embedded in the Jerk movement. And for reference, Zesty Nimble (which I use) advise E40 for Jerk - 2 orders of magnitude apart. The Nimble cable response to Jerk is presumably the issue which doesn't apply elsewhere. I am in the middle of testing.



  • @garis Doesn't quite work like that because the extruder speed has to follow the axis speed, during acceleration as well as at steady speed. Having said that, you can't use the extruder jerk setting I suggested with a Nimble.



  • @garis Check with Zesty that the "40" for extruder "jerk" is mm/sec and not mm/min. If it's mm/min then that equate to 2,400 mm/sec. I don't have any hands on experience of the Nimble but my understanding is that it uses very high gearing which means that the steps per mm will be high.

    .........Although, now I've looked again at you config and see that they are set to 420 which is about right for something like a Bondtech or Titan, so maybe I was wrong about the Nimble having high gearing and thus high steps per mm requirement.



  • Hello @Asdasd1234 , I think I know what's happening but don't yet have a fix. In the meantime, could you please print the attached gcode and report whether the slowdown/stuttering is any different to before. You need not print the whole object if there's no improvement. Thanks.

    0_1541238280413_CFFFP_CFDMP_80.gcode



  • It definitely printed faster than the original file I uploaded. But it still stutters and causes a worse surface finish than just turning off Pressure Advance.

    I've attached a picture of the 3 side by side (Set e-Jerk to 40000 on all to make sure its not that limiting it):

    • On the left, My original file. Pressure advance is on, Cura estimates 24 minutes print time. Actual print time, 48 Mins
      Lots of stuttering, horrible surface finish.

    • In the middle. I had the same settings but just turned off Pressure Advance. This gave a real nice surface finish, but I lose all benefits Pressure advance so the layer changes look horrible due to the oozing. Zero stuttering though. Cura estimates 24 minutes print time. Actual print time, 31 (still far form the 24 that cura thinks and I cant work out why 😞 )

    • On the Right. Your Gcode file you supplied this morning. Pressure advance is back on. It prints faster than the one on the left with an actual print time of 35 mins , but still suffers from stuttering and has worse surface finish due to that than the middle one which prints faster.

    Also, I'm happy to print out as many test prints as I need, as none will be wasted. I'm trying to get the fast printing sorted so I can pump out 50 odd of them for a relative 🙂

    Many thanks so far guys!



  • Had to put this pic in this post because the last one keeps flagging it as spam 😞 https://i.imgur.com/nHRrIsG.jpg


 

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