90 angle walls artifact



  • I have a small artifact when printing 90 degree corners. The result is globally good however there a bit of extra material that makes the corner larger. I have added a photo to show the result.

    20201211_175528.jpg

    It seems alittle of over extrusion, but E-step calibration it is not a parameter available on the CR-6 setup menu. The extra rouding is also a few tents of mm, compatible with the nozzle size is it unavoidable at that level? Should I change something in the my CURA profile?

    So far I only tried reducing the flow with no apparent effect.

    Thanks for any suggestion.



  • Thanks @shinmai and @gazman1985, the artifact seems to go in the "unavoidable" effects.

    I can clearly do more chamfers. Currently I am using both chamfers and correcting the the dimension, when in example I need make a hole. However as other CNC system do and correct for the size. However, my naive thought was that CURA should have taken the nozzle size into account of the tool you are using to machine your piece.

    If such correction goes into CURA I don't need to make my model dependent on the tool size.



  • It also looks like @shinmai may have a better grasp of this type of issue so that may be a better route to follow first.



  • @guivo its not something I have experienced although it maybe ironing thats enabled or over extrusion I would try disabling any finishing as that will keep the nozzle there longer.



  • This could be a lot of things, but two things come to mind: corner bulging or a z-seam issue.

    Corner bulging:
    This happens because the printer needs to follow the rules of physics, but the slicer can't realistically account for complex kinematics accross the range of different printer set-ups it has to support. The printhead has mass, which requires force to get into motion, but once in motion, also requires force to stop. On most consumer FDM printers, the motion of the printhead is controlled with rubbe timing belts. These have some flex to them, so when making sudden stops or sharp turns, the head will overshoot to some degree, causing sharp corners to bulge out somewhat, for instance. This is the same reason we have ghosting and ringing.

    You can try to reduce this by reducing print speed, obviosuly, but this will slow down your whole print. Another option is tweaking the acceleration of your printer. Teaching Tech's 3D Printer Calibration page has a good tool for generating test G-code to tune these settings in.

    The absolute best way to tackle the issue, however, is to design your parts with this in mind. Chamfers and bevels greatly help mitigate the problem, but obviously this is reasonable only for parts you've designed yourself.

    Z-seam:
    Cura has great options for controlling and hiding the so called Z-seam, or the position where the printhead starts and ends a layer, basically. These are under Shell as "Z Seam Alignment" and "Seam Corner Preference"

    Z Seam Alingment let's you control the position of the seam, if you care a lot about the surface quality of the part, if it's a statue for instance, you can use Z Seam Alignment to place all the seams at the back of the model, for easier sanding and for being hidden most of the time. Fastest print speed is achieved with "Shortest" and if your model needs to look good from all angels "Random" puts the seam in a different place on every layer, spreading out the small imperfections a lot more.

    The last option is "Sharpest Corner" which will have cura place the seam in the sharpest corner it can find in any given layer. If your part is mehcanical, this might be an issue, since the seam always being in the same corner on every layer wil obviosuly change the dimensions of that corner drastically.

    If Seam Corner Preference is set to anything but None, Cura will try to place the seam in a corner, too. With Expose Seam, it will prefer outside corners, Hide Seam prefers inside corners, Smart Hide allows both but favors inside corners.



  • @gazman1985 this actually the top, the artifact runs the whole height of all the sharp corners.

    checking the printer while working, it is like the head stop on the corner a little too much.



  • This looks like the bottom of the print? Slight warping can happen on the first layer. Cura if I remember correctly has a cool setting to adjust for that in Shell called initial layer horizontal expansion. I never remember that name so I search for elephants foot cracks me up that they added that as a search term.


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