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Zigzag pattern presenting weird behavior when reaching a circular wall.


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Posted · Zigzag pattern presenting weird behavior when reaching a circular wall.

Hello,

 

Would anyone be able to explain to me what is happening in the GIF attached, when the extruder reaches the edge of the circular wall?

The zigzag pattern is interrupted when it reaches the the wall, but instead of following the curvature of the wall and print it as one continuous line, it seems to break it into a lot of very tiny segments and prints it alternating between the left and the right of the segment. Only when the segment is long enough that its edges are not in contact with the already printed lines anymore, it resumes the zigzag pattern.

 

This behavior repeats on each layer and considerably increases the time of the print (even more with retractions activated since it retracts after each tiny segment).

 

What parameter can I change to prevent this segmentation of the pattern when it reaches the circular wall?

 

I am using Cura 4.11.0.

 

Thank you for your help!

 

Pablo

ezgif.com-gif-maker.gif

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    Posted · Zigzag pattern presenting weird behavior when reaching a circular wall.

    It is a function of the ZigZag pattern.  Changing to "Lines" will eliminate the shuffle movement.

     

    The end extrusions of ZigZag will maintain a tangency to the hole feature.  There are no circles in FDM and so you have a number of short line segments (the number of which is likely dependent on your "Maximum Resolution" setting) and those short line segments approximate a circle.  In addition, those short line segments pass back over the last long extrusion before the inner walls of the hole.  The setting "Compensate Wall Overlaps" might be involved.  I don't have 4.11 installed but in 4.12 the "Monotonic Top/Bottom" setting would be involved as well as Cura tries to keep everything moving in the same direction.

     

    At any rate, the nozzle is going back and forth putting in those short line segments.

    The alternating magenta and white colors are the segments of the tangent end extrusion.  In this particular slice the length of each segment is about 1.06mm.  If your travel settings are set for retractions at 1.00mm of travel then there will/might/possibly be retractions between line segments when the nozzle changes directions. 

    ZigZag.thumb.png.004c9ccd9fcc953d1b85277991f9c7e0.png

     

    It appears that you have "Extra Skin Wall Count" set to 0.  The effect of that will be that the end of the zigzags along the straight edges of the area will be over voids in the infill and will sag into the voids because they aren't supported and there is no "Extra Skin Wall" to bond to.  Eventually that would fix itself as some support is gained when the sagging previous layers firm up and provide some support for the latter layers.  At a micro-level that could effect the strength of the feature that will be built above that flat area.

     

    That's what it looks like to me.

    I've been known to be wrong.

     

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    Posted · Zigzag pattern presenting weird behavior when reaching a circular wall.

    That sounds about right!

    I'll give it a try when back home. Thank you for the very well explained answer.

     

    And also thank you for the extra tip about the extra skin wall. I don't know when or why I set that one to 0, but I was definitely looking into getting these walls back. It did give some troubles on a few prints indeed.

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