this post was submitted on 01 Aug 2025
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3DPrinting

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https://www.youtube.com/watch?v=XKrDUnZCmQQ

What if your parts just fit—every single time—no matter what printer, material, or slicer settings you use?

In this video, we break down the proven design principles that eliminate the guesswork from tolerances in 3D printing. You’ll learn how to design press-fits, snap-fits, lids, and interlocking parts that are robust to shrinkage, color variation, and machine quirks. Rounded corners, chamfers, compliant features, and grip fins — we cover it all and show why designing for process is more reliable than tweaking slicer settings.

By the end, you’ll know exactly how to model your parts for perfect, repeatable fit — anywhere, anytime, on any printer.

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[–] j4k3@lemmy.world 5 points 22 hours ago (1 children)

It is an interesting approach to use feather fingers to hold a lid. That one has never occurred to me in design, but I loath thick useless walls like this.

He kinda touches on the way sharp corners are an issue because of the overlap in the extrusion diameter at the direction change. The overlap in circles is ignored in the slicer so there is always some amount of over extrusion in corners without a built in radius matched to the tessellation resolution and step accuracy of the machine.

Personally, I prefer to make a slightly larger clearance for such an interface. Then I use a small round dimple between the parts in the center of the long wall. Any long wall will have some flexible compliance at the center. I use a small 2-4mm diameter dimple that is padded/pocketed 0.5-1.0mm with a similar tolerance to the part. The subtlety of this feature is far less likely to disturb the outer part perimeter wall smoothness. The trick is to design the positive dimple pad with a closer tolerance to one side so that contact pressure is held to prevent looseness.

[–] TheButtonJustSpins 2 points 20 hours ago (1 children)

I'm still trying to get the hang of that sort of fit. I saw it in a video about crush ribs but it didn't work when I tried it. Will keep at it until I figure it out, though.

[–] j4k3@lemmy.world 3 points 20 hours ago

Just do small test prints first. For a table saw feather board in PLA this worked but it is length and material dependant.

Calipers are consistent for the 2.6mm but too dead of a battery to charge the capacitive sensor past around 50mm so the scale shows ~63mm long. I think the optimum angle is around 30° but don't quote me. I just imported an image of another feather board and used it to get basic working dimensions. You only need to know 1 measurement in a flat image in CAD to calibrate the size for use in the background to draw your sketches on top of. With a table saw feather board, you know the slot dimensions. You could easily screenshot the video's sketch of the feather pattern here, import that and make a copy at any scale in FreeCAD. Mango Jelly has YT vids about this if you need them.