Is this a firmware or slicing issue (pressure advance?)



  • Hi Everyone,

    I have a tevo LM and a micromake D1 both running on duet wifi boards. I have them tuned pretty well with PLA but on both printers, I get this very obvious seam on prints and it is really ruining the accuracy as i get this "bump" at the point the layer starts and stops.
    I have tried every setting in cura I can think off (Coasting, wipe, retraction,speeds) and they make no difference to the seam.
    Started to make me think it could be something to tweak in the firmware.
    Could this be caused or solved with pressure advance? I have not configured this yet in any way.

    I find it odd that i get this on 2 printers that are pretty different apart from the control board.

    Thanks for the suggestions

    1_1552946370070_2019-02-01 15.35.33.jpg 0_1552946370069_2019-02-01 15.36.09.jpg



  • Pressure advance may help, but without seeing your configuration and slicer settings it's hard to say more.



  • Please save the Cura project (File -> Save), zip up (or rename) the resulting .3mf file and attach to this thread.



  • Cannot upload the zip file but here is a ling to a zip containing the 2 cura profiles and the config.g from each printer
    Profiles

    I should add that both machines use a bowden setup.



  • Thanks for the files. Is it possible to supply the model also?



  • This is the model

    although the issue is not specific to this model and is easy to replicate on almost all models. It is worse on round models where the seam cannot be pushed to the corner.


  • administrators

    It's hard to eliminate seams completely, but when they bulge like that, pressure advance usually helps.



  • I've done a few tests setting up pressure advance. Using 0.1,0.2,0.5 and 1 as options.
    Printing a simple cylinder, just 2 walls. No infill on top / bottom.

    I have the expected very noticeable seam but all 4 prints look identical

    Running the M572 shows that it has been set.
    Running 1.2 firmware

    0_1553095718917_2019-03-20 15.27.39.jpg



  • @buzzby That's fairly conclusive that pressure advance on it's own won't cure your problem. Having said that, there are all sorts of interactions between speed, acceleration, instantaneous speed change (jerk), retraction, temperature and pressure advance. Especially extruder jerk and acceleration. That's why it's always best to get everything else dialled in as well as possible, and only then try pressure advance.


  • administrators

    @buzzby said in Is this a firmware or slicing issue (pressure advance?):

    I've done a few tests setting up pressure advance. Using 0.1,0.2,0.5 and 1 as options.
    Printing a simple cylinder, just 2 walls. No infill on top / bottom.
    I have the expected very noticeable seam but all 4 prints look identical

    Odd, I would have expected some difference. At the higher pressure advance settings, can you see the extruder gears moving backwards just before the end of each perimeter?



  • @dc42
    I can certainly hear the difference in the extruder as it back off and on.

    Do the jerk settings I have currently look ok or should they be changed?
    Not sure which command that is.


  • administrators

    M566 X1200 Y1200 Z1200 E3000 ; Set maximum instantaneous speed changes (mm/min)
    M203 X39960 Y39960 Z39960 E3000 ; Set maximum speeds (mm/min)
    M201 X1000 Y1000 Z1000 E1500 ; Set accelerations (mm/s^2)

    M566 is the jerk setting. Those are OK if the extruder is not skipping steps. If it is, reduce the E value.



  • Increasing extrusion width in your slicer can help with it - I ran my 0,4mm nozzle at 0,6mm extrusion width for an pretty good result - also another type of nozzle can also make a difference.

    Have you seen if it is in the start of the line or the end of the line, that the blob orccurs?.



  • @martin1454 Looking at the print it looks like the start and end of the line have the extra "blob"

    I tried a different slicer (slic3r) and got pretty much the same result (no pressure advance though) Cura definitely does a little swipe from the outer layer in but changing the wipe setting to 0 doesn't make any difference



  • @buzzby

    Try playing around with negative restart distance (0.05-0.2mm) and see if that helps.

    Otherwise, as said earlier, try in slic3r (PE?) and change "default extrusion width" to something like 0.5 or 0.6 and see if helps - It did for me.


 

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