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Cracking at snap-fit hook base in SLS PA12

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Hello everyone, I’m using SLS 3D printing (PA12, 0.12 mm layer height) to create a snap-fit enclosure for a handheld sensor device. The enclosure has three internal hooks that flex about 1.5 mm during assembly and are supposed to hold a PCB securely without any fasteners. I’m seeing occasional cracking at the hook base after just 2–3 assemblies. Wall thickness around that area is 1.8 mm.

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      Hello everyone, I’m using SLS 3D printing (PA12, 0.12 mm layer height) to create a snap-fit enclosure for a handheld sensor device. The enclosure has three internal hooks that flex about 1.5 mm during assembly and are supposed to hold a PCB securely without any fasteners. I’m seeing occasional cracking at the hook base after just 2–3 assemblies. Wall thickness around that area is 1.8 mm.

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      It sounds like pretty typical over-stressing at the base of the snap feature. Even though PA12 is flexible, with 1.8 mm wall thickness and a 1.5 mm deflection, you’re probably exceeding the elastic limit locally—especially at that sharp corner where stress concentrates. Despite good toughness, the particle welded microstructure isn’t forgiving for sharp flex points in the way molded parts would be. A few cycles of flexing plus small layer inconsistencies can easily initiate a crack.

      You might want to increase the wall thickness around the base to 2.5 mm or more if you can afford the space. Also, think about adding a small radius fillet where the hook meets the wall—like at least 0.5 mm. It’ll spread out the stress a lot better.

      You could tweak the hook geometry to work better, but this is actually a solved problem— a thinner, longer arm that flexes more uniformly would survive better, but existing solutions look different.

      Take a look at standard PCB mount hook types, they offer a more forgiving approach. It takes the stress away from the base and spreads it out.

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        Andronikos

        Ok – yes, I’ve looked at that style of PCB mounts now. I’ve given it a go. This is my interpretation.

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Cracking at snap-fit hook base in SLS PA12
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