Over-extrusion on corners



  • Im using the duet3d wifi with reprap marlin gcode flavor in cura and im getting over-extrusion on my corners/curves any help would be greatly appreciated.



  • think it might be an issue with duet using relative extrusion where as cura is giving absolute



  • You can set cura to use relative extrusion. It's a hidden setting by default, but it's in there if you search.

    However, over extrusion on corners is probably more related to speed. Likely jerk.

    Are you using custom jerk and acceleration settings in Cura?
    What are your speed settings in config.g?



  • Added M82 (set to absolute) to the start code for cura and it has fixed it.



  • @phaedrux
    i am using a cnc router as a large 3dprinter and i have 2 steppers in the x axis and so im using the other extruder driver to run the other x stepper. Still need to play around with the acceleration as the table jerks around alot on short passes.

    M566 X0 Y0 Z12 E120:0 ; Set maximum instantaneous speed changes (mm/min)
    M203 X30000 Y30000 Z960 E1200:30000 ; Set maximum speeds (mm/min)
    M201 X100 Y100 Z100 E100:100 ; Set accelerations (mm/s^2)

    Got it printing for the first time today so now i just need to make fine calibrations.

    1_1524208124823_20180419_123724.jpg 0_1524208124821_20180420_162611.jpg



  • Is that right that your X and Y jerk speeds are 0? That would lead to a complete stop and pause to change directions I think. That would be the cause of the over extrusion on corners.

    Try a low value like 1 or 0.5 and see if that helps.

    Also try increasing your extruder jerk and accelerations, say 600 jerk and 10000 accel.

    That's a cool printer by the way. Definitely large format! How much Z height can you get on that?



  • it has 150mm clearance.
    the latest version of creo gives the ability to change to relative values for the extruder.

    iv now run into different problems. found the extruder was getting much hotter than the target temperature. so i attempted to re-calibrate the thermistor with no luck. when turning on the heater to 180 it would shoot way past 180 and error out. Have ordered some better quality temp sensors and hopefully this will solve my celebration problem.



  • Have you run a PID tuning cycle on the heater yet?

    https://duet3d.dozuki.com/Wiki/Tuning_the_heater_temperature_control



  • thanks thats fixed that problem did the auto tuning



  • Have the corners improved?



  • Big improimprovement origanaly it was sewing out now there a little bit of overshoot?



  • 0_1524697455284_20180424_152716.jpg



  • It looks like it's over extruding. You can test by reducing your extruder 100% in the DWC during a print.

    What is your extruder configuration?

    It might help to go through a tuning guide, such as...

    http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide

    That will get your hardware parameters into accurate software settings.



  • So back to this problem i have sorted out the extrusion rate so that its not over-extruding on long lines. But when it comes to doing ziz-zag infill or where the machine slows for corners i get over-extrusion as seen in previews post. I believe this is where the extruder rate is not slowing to match the speed of the print head as it Accelerates/decelerates at the end of straight travel. This is particularly bad for short zig-zag infill as the head never gets to full speed but the excess is still noticeable at the start and end of longer travels. So does the firm where compensate for this? Can the extruder velocity be proportional to the head instanious velocity or does it assume a very high rate of acceleration which makes this unnecessary in most physical designs and is only a problem in our build because we are starting with a very heavy cnc router. Hoping to hear that the compensation is built in and we just haven't enabled it or tuned it.



  • 0_1527647962740_20180530_122633 (1).jpg 0_1527647971357_20180530_121144.jpg



  • 0_1527648216363_20180530_121130.jpg 0_1527648221286_20180530_121148.jpg



  • I think you can compensate for this over extrusion somewhat with pressure advance.

    https://duet3d.dozuki.com/Wiki/Pressure_advance

    There is the relevant documentation.

    Basically it will try to take into account the elasticity of the molten filament and adjust the extrusion feed rate dynamically. It may take some tuning but I think this is exactly what you want.



  • Will give it a go as I respect your knowledge, though we had assumed this was not a major contributor to the problem because we are not using a bowden cable, and the e-3d head we are using has a relatively short distance between the drive wheel and the hot end. Will let you know what we discover.



  • For a direct drive extruder like the Titan Aero like I see in your picture can still benefit from pressure advance. A value of 0.05 works well for me with PLA.

    Your prints are starting to look pretty good.


 

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