engineeredAF

em m0shouris Verified account @emm0sh · 4d

FDM parts of any material are an inappropriate (and i would argue unsafe) choice for any loaded application where they’re critical (supporting humans, a part of a critical safety mechanism, etc.)

this goes beyond anisotropy (which is a challenge, but solvable). you could in theory use non-linear FEA to model the behavior of the part, but it takes a herculean effort and still doesn’t provide the whole point of FEA in the first place for safety critical parts — the predicted failure mode at a specific loading

this isn’t because these parts are hard to model, instead, it’s because FDM is inherently flawed. there are no guaranteed mechanical properties. vendors will list toy values on their websites, but they do not reflect the “real” values and are misleading. real means as built

every car, plane and multi-story commercial building utilizes an important property of materials that manufacturers have gifted to engineers over the centuries, and that’s reliable mechanical properties

aluminum, steel and most metals have a yield or ultimate value by which engineers design to, enabling us to predict when and how parts will fail. FDM does not, and it isn’t the material’s fault, it’s the process’s fault

when i analyze a part, it produces values by which i can meter against mechanical properties of the material. the main problem with FDM is that it does not. the process itself invalidates the underlying mechanical properties

the produced part does not have bulk material properties of the constituent material due to the geometry of the “lay up” of the filament that produces the part. this means an accurate analysis would not be on the “as modeled part”, it would have to be on the “as manufactured” model of the part, or the “sliced” model of the part

and even if you did this: it would still be for moot because the shear resistance of each layer produced is dependent on the orientation and settings of the print and the environment in which it was printed. the properties can vary wildly between prints

i won’t even get into cold flow which is exacerbated by this lamination issue. i still think FDM is great in the limited cases of onesie-twosie fixtures and tooling

here’s a solution: sheet metal is cheap. use a sheet metal substrate to build up the load bearing structure of your parts. they become safe with proper analysis and can also get rid of the temperature independent cold flow problems that hamstring most FDM parts

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engineeredAF Verified account @EngineeredAf · 4d

Turbocharge your Chevy Cruze for $200

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engineeredAF Verified account @EngineeredAf · Jul 14

i just learned there's a vevor store in houston

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