Is anyone aware of any strength testing that's been done for 3d printed pieces?

3D Printing
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1

Is anyone aware of any strength testing that’s been done for 3d printed pieces? I am curious how they would compare to a standard injection molded piece. I don’t have a printer, but if someone was willing to send me ASTM dogbones, I could test them and show the strength results on here.

Any guesses on strength drop? I’d guess around 40% as an off the cuff estimate.

2

I imagine the numbers would be all over the place, depending on each machine setup. It would be interesting to see, tho. Do you have specs for the dimensions of the dogbones?

3

I can lookup the exact specs tomorrow, and I will post them.

4

Following part design, mechanical properties can be as performing as for injection moulded components (less than 5% difference). The only article I can think of is old. Sorry about that.

Anisotropic Material Properties of Fused Deposition Modeling (FDM) ABS. Ahn, Sung-Hoon, et al. Rapid Prototyping Journal 8, issue no. 4 (2002) - 248-257

5

Thanks Matteo, looks like it’s already been done. Very interesting read.

http://mech.utah.edu/iss/files/2012/10/Ahn-Anisotropic_material-2002.pdf

6

If you have the time, check out http://www.formlabs.com forum and website. There is some data about material properties on the website and mentioned in the forums too. The Form1 printer is an SLA machine, so it uses photopolymer resin. After a part is formed, it can be sun hardened, which changes its properties significantly.

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Unsourced rule of thumb I read is that a PLA printed part has ~30% of the strength of a similar injection molded part.

I think is a great area for student research projects.

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It also depends very much on the material. 3D Printed Nylon seems to be no less strong than injection molded nylon. It bonds so well as a molecular level that you don’t get tearing along layer lines.

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@Brett_Giesler we’ve tested dogbones in my university, printed on a crappy Sells Mendel in ABS (Orbitech). As long as they are only loaded parallel to the layers, they behaved almost exactly like molded parts.
We did not test strength perpendicular to the layers, but I’d expect that to be at about 30% of a molded part.
I should have the exact results around somewhere, if you want I’ll try to dig 'em up and post them.

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@John_Ridley Reduced contact area does produce weaker parts, though tensile strength can sometimes be carefully managed for FDM components to overcome strength loss: depending on material choice ( @ThantiK ), layer height, deposition width and some other factors, higher levels of cristallinity tent to form due to molecular line up during extrusion and slow cooling times. Also, drawn filaments show stiffer and stronger behaviour for tensile stress parallel to layers deposition plane, while compressed, short parts may be more subject to buckling phenomena than usual.

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I have printed little stubby screwdrivers and bottle openers and they seem as strong to my fingers as any injection molded parts. They may be slightly weaker if tested by a machine to the breaking point, but for just hand operated parts it feels good to me.