How to design a print with better tolerances – Slant 3D (12:34)

Submitted ⁨⁨3⁩ ⁨weeks⁩ ago⁩ by ⁨j4k3@lemmy.world⁩ to ⁨3dprinting@lemmy.world⁩

https://lemmy.world/pictrs/image/9453728a-3943-4e89-9dd0-e68cff662b8e.jpeg

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 ⁨3⁩ ⁨weeks⁩ ago
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.

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- Blue_Morpho@lemmy.world ⁨1⁩ ⁨week⁩ ago
  Could you show a pic about what you are describing?
  
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  - j4k3@lemmy.world ⁨1⁩ ⁨week⁩ ago
    Sure.
    
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- TheButtonJustSpins@infosec.pub ⁨3⁩ ⁨weeks⁩ ago
  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.
  
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  - j4k3@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
    Just do small test prints first. For a table saw feather board in PLA this worked but it is length and material dependant.
    
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    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.
    
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  - MysteriousSophon21@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
    Try starting with a 0.2-0.3mm interference for crush ribs and print a small test piece first - I’ve found the key is getting the right wall thickness so they flex just enogh without breaking.
    
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zipsglacier@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
The part at the end about the fins is good, but too quick. He says put a gap under the fins, and that makes sense, but then how do they print? Are they small enough that they can basically just break away? I’ve heard ironing is the key to stacked, separable prints (like miltiboard grids). I’d that (a) necessary, (b) unnecessary but helpful, or © irrelevant for these fins?

P.s. while I was internet searching to try to understand this, I found a cute video of his from 3 years ago where he is explaining the same concept, but with less polish and less good vtuber equipment. Still neat, and neat to see how he has and hasn’t changed over time.

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- j4k3@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
  If I was doing this design, I would build the fins from lower and taper pocket the bottom edge with a 45° pocket that enables them to print unsupported. It is possible to just leave a gap, or make a single wall riser near the tip to anchor the bridge but this will need printer and materials tuning with inconsistent results in my opinion. I think he was mostly showing off the abstract application of an unexpected idea people are likely to watch.
  
  Ironing is as much about hardness as it is about smoothness. The extended heating will make the lower surface harder and might be workable on your home machine. Your flow rate in slicer settings will be critical for ironing because any bulldozing of material left behind will wreck you. Plus all that extra heat in a solid stack of layers is going to strongly promote warping.
  
  If you’re really tight on clearance for something like this, I have used typical glue stick. You just add a print pause and either some tape or very carefully apply glue stick just to the overhang clearance with a 2 print layer height gap. The glue may take a day of soaking in water or alcohol to completely soften and dissolve, but that is basically poor-person dissolvable print supports. That trick is really only worth doing for stuff like mechanical prints you want to embed in an assembly with tight clearance. It is a pain in the ass and certainly not a transferable design for a farm or file sharing.
  
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  - zipsglacier@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
    Thanks! I wondered about the glue stick trick, but I think you’re right that a taper would be better. I have to wonder why he didn’t say that, but maybe he was tight on time or some other thing.
    
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BeardedGingerWonder@feddit.uk ⁨3⁩ ⁨weeks⁩ ago
A crud catcher, just what every box needs.

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