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Sometimes fewer walls are better (sh.itjust.works)

submitted 9 months ago by p1mrx to c/[email protected]

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I think I found a counterexample to the common wisdom that more walls always create a stronger part.

The pictured S shape is 1.5mm thick, so printing with 2 walls leaves no room for infill. My testing wasn't very rigorous, but it seems that the hybrid structure of walls + rectilinear infill is 10-20% more rigid than walls alone. The infill adds strength by cris-crossing between adjacent layers.

I think it's fine to include a concentric top/bottom layer, but multiple identical layers weaken the part. I also tried 0 walls (infill only) and that was garbage.

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[–] [email protected] 19 points 9 months ago (7 children)

All you've done here is create more walls using a single piece. If you want durability, your design will win as it allows for flex. If you want rigidity, it will be less rigid and take longer to make due to its complexity.

The loss in rigidity is due to creating weak points as the line turns. The gain in flexibility is exactly the same weakness but now a positive. It will take greater force from weight, butt less impact force.

If you're after rigidity, either cram the space with as few complexities as possible, or fill space with triangles.

[–] p1mrx 3 points 9 months ago (6 children)

It's not really clear what you're saying, because they're both "my design". Could you specify 1 wall vs. 2 wall?

[–] [email protected] 2 points 9 months ago (4 children)

The 1 walled hook has the infill resisting and pulling back as you try to straighten the hook. When it fails, some of the connections between infill and walls break, causing the hook to lose it's form or original rigidity permanently. In the case of 2 walled hook, this damage should be less severe, making it more durable.

[–] p1mrx 4 points 9 months ago* (last edited 9 months ago)

Okay, but if my 2-wall hook bends into a straight line, then I don't really care about the durability of that no-longer-hook-shaped object.

Edit: I agree that 2-wall could make sense, if your goal is to reuse the hook (with a more appropriate load) after the heavy load falls off. That's analogous to protecting a wire with a circuit breaker.

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