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How to Strengthen Your 3D Printed Parts

So, you want to 3D print a vertical rod, but you don't want it to split in half. We're going to talk about how to prevent that, not through slicer settings, but through actual design. Now, this is a really common problem; people don't want their 3D printed parts to just break in half whenever you push along them. But how do you make them tougher? 3D printed parts break along the layer lines? No, they don't. 3D printed parts admittedly are weaker for the material because of the printed layer lines, but that just means you design around them.

If you're going to make an airplane out of wood, you're going to design a little bit differently than if you make it out of aluminum or cloth; there are different rules.

With 3D printing, if you want to make a part a little bit stronger, what a lot of people do is they go into the slicer settings and they make the walls thicker. That's actually correct for a cantilevered beam; thicker walls are actually good because they put the material out where the actual compression and flexure is inside of the beam as it bends. The top spreads and the bottom compresses, so having thicker walls puts more material up there where it matters. But the issue is now you're dependent on slicer settings. If you upload that file to a manufacturer to have produced, you're now transferring files and then they don't translate to the machine and everything just goes wrong. So what you want to do is you want to actually design your 3D model so that it has wall thickness where you need it. You can actually embed a pattern, basically a bunch of holes around the outer part of the part. For the example below, with that rod, I just put a bunch of circles around the outer edge and cut holes through it.

What I have now just done is thicken the walls of the entire part because now there is more material around the outer edges, because you're filling in the walls rather than simply having infill go out to the outer skin and then coming back. This is a way more reliable way to produce more material. Now, even though you can just design holes and put them around the outer edge, there's a few different ways that you want to go about it.

All of these induce the slicer to create more material out in the outer edges. But the trick with all of these is that they're exceptionally thin. Each one of these features is basically 0.2 mm wide, and the reason for this is that it's large enough for most slicers to identify it, but small enough to where when they print along it, the walls basically fuse together. Because the last thing you want are the walls to be spread out, because if you do a ripple around the outer side and it prints spread apart as two separate walls, then all you did was create a sleeve around a center core, which actually makes it weaker. So, you make these features very, very small so that they just make more material go there, but they don't actually split the part across or create any sort of stress concentrations.

Of the ones that we used, the ribs were actually the best. When we ran our test with a simple cylinder that just had a simple infill and a simple 1 mm wall, it was almost a third as strong as the ribbed design that we did. If you uploaded it to our API, the ribbed version would use more material and be a little bit more expensive, but it would be so much stronger and you would not be reliant on the slicer settings that create that more strength. You wouldn't have to say, "Oh, I need the wall thickness to be 4 mm or something like that." You simply design in very thin features that are 4 mm thick and they induce that wall.

Now, if you get fancier with this geometry, what you're doing is you're now creating a 3D printed rod inside of a 3D printed part. So, you are able to build up strength across the part without having to add additional features or worry about the homogeneity of it. Now, of course, the easiest answer to all of this is just do a solid infill part, but barring that, when you want light weighting but controlled strength in particular areas, what you can do is you can introduce these microstructures which then cause the slicer to put more material where you want it inside of a part so that when you want to print a part, it doesn't break anymore.

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