Has anyone experience in printing parts for load bearing designs with aluminum or steel comparable strength?
I can imagine one can use e.gg.ABS, PLA or nylon filled with CF or Kevlar, but how does one get around the problem of fiber bias, in other words the part is only exhibiting the strength wanted in the sections of the design were the fibers are aligned?
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@jakkse @3DinShelby you to have experience in printing with stainless steel - are you able to help @BumbleBee? Cheers
We have quite some experience with this matter because of our work on The Bike Project - 3D printing a fully functional bicycle with an Ultimaker.
The two materials we have examined are ABS and PLA. For the Ultimaker, PLA results in stronger parts than ABS. This is because PLA is more suited for printing (lower melting temp), which means the bonds between layers are stronger. However, if you have a printer that is really good with ABS this might be different.
With FDM printers the parts you make will always be weakest against the direction of your layers. This is mainly true for parts that do not have 100% infill. From the numbers I’ve seen the difference is about 3-5 times weaker against the direction vs with the direction.
The way to solve this is either to design your parts so they are only bearing loads in the right direction, by reinforcing parts by adding an additional print with a 90 degree angle in it’s filament direction or by combining clever design with the right slicing settings.
What we tend to do for the bicycle is create webbing inside parts - instead of infill, and add pretty thick ribs on the outside. This allows us to print with 100% infill mostly eliminating the directional issue (by having alternating layers put down at 90 degrees to each other) whilst using as little material as possible. This has created surprisingly strong parts with PLA.
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Stef/Paul thanks for the useful info. Indeed i would expect PLA to give better knitline strenght because of the lower MP than ABS. Also rubber modified materials like ABS tend to give lower knitline strengths than none modified. I would however be suspicious wrt PLA’s durability. I have some experience with PLA in other applications and the sensitivity for moisture/moist air, depending also on the catalyst residues etc, will make it age pretty quick as compared to non-condensation polymers like HIPS, ABS, PE.
But thanks again for your useful comments!
Durability is indeed an issue we haven’t been able to test on yet! there’s a high probability that we will need to use some postprocessing to make the parts watertight, in my experience PLA prints tend to take in quite some water - which will probably cause them to wear/degrade faster.
We have done a small test on creep in a printed PLA part under a constant load for a month - this test suggested there is very little creep in such parts, which is pretty neat! On our to-do list is to test the long-term strength of something like a printed bolt. I expect the creep in that to be more significant.
Do you have any experience with materials other than PLA/ABS? Am quite interested in learning what they are!
^P
I have no experience with 3D printing, but I have with molded/extruded PC (nonfilled/glass filled, impact modified) PC/PBT, PPO/PS.
I made some insertbearing designs for my prototype windturbine in PLA and the word without a problem for over a year now
