this post was submitted on 04 Dec 2024
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Bridging direction should be geometry-dependent (lemmy.ca)
submitted 2 weeks ago by [email protected] to c/3dprinting
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Bear with me for a moment, because I'm not sure how to describe this problem without just describing a part I'm trying to print.

I was designing a part today, and it's basically a box; for various reasons I wanted to print it with all the sides flat on the print bed, but have bridges between the sides and the bottom to act as living hinges so it would be easy to fold into shape after it came off the bed. But when I got it into PrusaSlicer, by default, Prusa slices all bridges in a single uniform direction--which on this print meant that two of the bridges were across the shortest distance, and the other two were parallel to the gap they were supposed to span. Which, y'know, is obviously not a good way to try to bridge the gap.

I was able to manually adjust the bridge direction to fix this, but I'm kinda surprised that the slicer doesn't automatically choose paths for bridging gaps to try to make them as printable as possible. I don't remember having this issue in the past, but I haven't designed with bridges in quite a while--it's possible that I've just never noticed before, or it could be that a previous slicer (I used to use Cura) or previous version of PrusaSlicer did this differently.

Is there a term for this? Are there slicers that do a better job of it? Is there an open feature request about this?

Basically just wondering if anyone has insight into this, or any suggestions for reading on the subject.

Thanks!

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[–] dual_sport_dork 5 points 1 week ago* (last edited 1 week ago) (1 children)

If anyone is stumped by this in the future, in Slic3r/Prusa and its derivatives, set your bridging angle setting to zero, which is what tells the slicer to attempt to automatically calculate the optimal angle for each bridge. If you have some other angle number in that field that value becomes global, and the slicer will create bridges at that angle come hell or high water, whether they would actually work or not.

This comes with the usual caution that this will increase your slicing calculation time, but unless you're running it on a netbook from 2004 or something I don't think this will realistically be an issue for anybody.

[–] [email protected] 3 points 1 week ago

That wasn't the issue for me--my bridging angle was set to zero (the default). The issue was that the anchors for these bridges ran into one another, which made the slicer treat them all as one single unified bridge, and choose one angle for the lines across them all, rather than treating them as separate bridges (which is how I was thinking of them, because they crossed different gaps). I put the text below the images on this link before I understood what had gone wrong, but the images are still useful for illustrating the error: https://imgur.com/a/VjUTVaq