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DURABILITY of 3d printed parts

DURABILITY of 3d printed parts

Postby TRS » Wed Feb 26, 2014 1:34 pm

Hi, i'm new to the forum, i'm interested in 3d printing and i'd like to know if the printed components can take a beating. that is, bear a load such as might be required of an orthotic. I've had some orthotics (inserts for your shoes for us flat footed folks) for 17 years and they look like they'll go another 17. But i have one pair, i'd like to make 20 pairs, but would they standup to the use? Thanks, TRS
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Re: DURABILITY of 3d printed parts

Postby Awesomeness » Wed Feb 26, 2014 4:09 pm

Unfortunately, I don't think they would stand up to that very well. Let me caveat that by saying that the term "3D printing" does encompass several different technologies, some that will do better, and some that will do worse. However, I'll assume that for our purposes you strictly talking about the Fused Deposition Modeling (FDM) version of "3D printing", used by the WhiteAnt model here.

FDM models are maybe 60-80% as strong as a solid, injection molded plastic part of the same material (e.g. ABS). Thin FDM parts are especially vulnerable, which makes your insoles a challenge. Since FDM lays a thin extruded round bead, it only bonds to the neighboring beads at a few small contact points. In my own testing, when you break FDM models, they always break pretty cleanly along some predictable "seam" between layers, typically in an area where the 3D printer went off and printed somewhere else, returning after the the layer had cooled more, and the resulting bond wasn't as good.
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Re: DURABILITY of 3d printed parts

Postby TRS » Thu Feb 27, 2014 11:59 am

Thanks Awesomeness. I've heard there are more "industrial" applications of 3d printing and these folks must have addressed this problem, any idea of how? Do you think the whiteAnt printer could be adapted to this purpose?
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Re: DURABILITY of 3d printed parts

Postby Awesomeness » Thu Feb 27, 2014 2:09 pm

There are some 3D printers that exist that produce quality enough for actual production use (e.g. making something that you could sell as a finished product). For example, the Fortus line of machines start at a couple $100,000. They have TONS of improvements over these little DIY machines... heated build enclosures, multiple nozzles, precision heat control on the nozzles, specially formulated support and build materials, finer controls, etc.

In the end, what you're trying to make with a 3D printer needs to make sense, financially. For example, the shoe inserts you are trying to make would probably cost $1 each to injection mold, and you could mold one every few seconds, but it requires molds to be machined that cost $20,000+ each. So as long as you want to make several hundred, or many thousands, you get to spread out that investment in molds. But if, in your case, you just want "5 extra pair", there is no way to recoup $50,000 in setup fees for injection molding, so you look to a different technology. 3D printing is always slower, and costs a lot more per item, maybe taking an hour or two to make a single insole, and consuming several dollars of filament. However, your total cost for 5 pair becomes $100, instead of $50,000.

The different 3D printing technology, similarly, have their own pro's and con's. The UV cured inkjet based machines, such as the Objet line, produce weaker models, but the resolution is generally higher, and they can print with flexible materials and coat the model in a smooth coating. Powder based 3D printers can produce weak models, but can also print colored ink into the powder as they build, so that you get a full color model. Selective Laser Sintering (SLS) can produce metal objects, that could not possible be physically machined, but at tremendous cost. It's all just tradeoffs, nothing is simply "better".

Finally, if you know you are going to manufacture a part with 3D printing, an engineer will intentionally design the part to maximize the capabilities of 3D printing, and minimize weaknesses. So unlike simply trying to 3D print your shoe insoles, the engineer will have researched/tested things to know what the thinnest FDM model he can allow that still meets the mechanical properties he desires, then will have intentionally designed the part to never have any thinner areas than that.

You could equate this all to cars. You can use a Lamborghini street car as a race car. What improvements did Lamborghini make to a regular production street car to make it able to also be used as a race car? And ultimately, it's still not going to be a better racer than a purpose-built actual race car. But if your particular need to to race 1 day per year, and drive it daily the other 364 days, then it might make sense for you to buy one Lamborghini instead of one Honda Civic and a second purpose-built race car. 3D printing still has lots of advantages and disadvantages, and it only makes sense to use it for "production" in certain situations. The vast majority of 3D printers owned for professional use are just used to print models that test "fit, form, and function" in a rough but close way, before spending thousands (or tens or hundreds of thousands) of dollars to make the real item.
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