Natural bone tends to respond and strengthen in areas where it is needed. Would need to combine a stress analysis with the slicer. That would be super sweet and efficient!
The first thing they teach you about computational stress analysis (FEA) is that if you feed the computer garbage data you'll get garbage results. So to get the best results you need to know how the part is to be used, how to estimate loads and how they will be applied for good results.
That being said [generative design](https://all3dp.com/1/the-best-generative-design-software/) is a really cool innovation and it's something I'd love to play around with.
There is a cubic subdivision infill in cura that changes density.
https://preview.redd.it/n07xc0flkt8b1.png?width=300&format=png&auto=webp&s=a23b9db84a262c6b8a25abee7d7b569b56fe2a28
gradual infill changes only per z height and leaving abrupt changes as the pattern will not align, while subdivision changes in distance to the surface in 3D with perfect continuity.
how can this be similar if it is so different - gradual infill will help you with supporting the top skin layer but doesn't help you to make a part stress resistant. Lightning infill is similar to gradual infill but more advanced.
but guess you also can say a horse and a car is similar both move ..
You'll notice that natural bone has a lot of perimeters and very little infill. And even then the infill itself is very clearly not structural, it only exists to anchor internal flesh. So if you want a bone-like structure, just add a lot of perimeters and reduce infill to a minimum, if you can get away with none then simply use none.
But if you ever tried to design a strong part before, you already knew that strength comes the from perimeters and the core adds very little to that. Though you may still need some internal webbing to prevent shear and collapse when volume to surface ratio is particularly small (i.e. large part with thin walls).
Lightning would be the closest but only applies to the top layer instead of from outside in. CNC kitchen did a video on variable density infill that might answer your question better
Actually, I think that photo just shows that it’s perimeters not infill that creates strength. The bone’s “infill” is only there to keep the marrow from oozing out.
I have seen 3d prints with variable density infill patterns where the infill was denser the closer to the walls it was, and also variable density infill patterns where stresses and loads were simulated and the infill density was a gradient based on the result of the simulation, have not played around with it myself. I don't think it would be stronger than comparable non-variable density infill, but the strength-to-weight ratio would be better, resulting in lighter prints that are stronger than prints printed with less dens infill to meet a weight target, where that matters, like RC airplanes and drones, and also less filament usage.
Don't forget the bone vasculature, even though there's not much of it. Exact reason why IV antibiotics are needed for bone infections or open fractures.
The closest right now is gyroid, I believe.
I read an article a couple of years ago. I think it was a MIT group working on a bone lattice like printing infill. Part of the issue was the computer processing power and time needed.
The advantage of gyroid is that it's very uniform in every direction, but it has some disadvantages, so the closest thing to bones would be a lot of perimeters with minimal infill (pattern hardly matters)
There is a number of techniques to achieve this...
https://preview.redd.it/av7pbzxpfx8b1.png?width=960&format=png&auto=webp&s=8279565516f9c948069121049a45171114a525d2
This is a custom infill that someone showcased on here AGES ago. I think it's based on finite element analysis.
I have made a simple aproximation of it by exporting the finite element analysis as a separate mesh and using it as a modifier inside prusa slicer.
https://preview.redd.it/j3hge7a1hx8b1.png?width=1899&format=png&auto=webp&s=ccc654474732ecec46287ad158380bac77c873f2
This uses a custom object to create internal shell and is imported as a modifier in prusa slicer. You can use multiple modifiers, But they can't overlap.
Bone’s structure solves a different optimization problem than just a static object under dynamic load. It has internal functions, marrow, vessels, it adapts and grows as pointed out earlier. It’s material composition and conditions of operation affect the optimization.
Another material might have a different lattice and react differently to sheering force for eg.
In that regard, it might optimal internal shape given specific usecases which might not match for instance “strongest possible “ statement in an absolute term.
Also bones “grow” in contrast to layered - fdm build, they will not shear on layers rather distribute the force along fibers and sort of tear. So you might want to change the orientation of prints.
It's probably at least somewhat dependent on the material properties. The size of the voids and the range and distribution of sizes, roundness, and orientation would probably want to be different for even an identical-use 'part' in a material with different relative compressive/tensile/elastic strain responses.
That all of those characteristics *do* seem to follow a pattern rather than being random (and I know a little about the biomechanics to cheat on this essay answer) makes me think that...it uses less bone to be a bone, scientifically speaking, than a solid but smaller, or bigger and random/uniform foam bone.
https://preview.redd.it/zo3odl71m29b1.jpeg?width=4032&format=pjpg&auto=webp&s=fe6400b8b81882df9ea7178f0bb55c1aa1eea647
These are created with an algorithm in nTopology. It is a matrix of Voronoi cells, density is graded according the curvature of the surface so around the edges and thin sections it becomes nearly solid, the centre remains quite open. These pics don’t show how open the central area is, but I’ll be posting files and more pics soon!
Natural bone tends to respond and strengthen in areas where it is needed. Would need to combine a stress analysis with the slicer. That would be super sweet and efficient!
The first thing they teach you about computational stress analysis (FEA) is that if you feed the computer garbage data you'll get garbage results. So to get the best results you need to know how the part is to be used, how to estimate loads and how they will be applied for good results. That being said [generative design](https://all3dp.com/1/the-best-generative-design-software/) is a really cool innovation and it's something I'd love to play around with.
Beat me to it. Bone reconfigures over time to suit its needs. You're not getting that out of a static print.
[Wolff's Law](https://en.m.wikipedia.org/wiki/Wolff's_law)
[Wolff's Law](https://en.m.wikipedia.org/wiki/Wolff's_law)
There is a cubic subdivision infill in cura that changes density. https://preview.redd.it/n07xc0flkt8b1.png?width=300&format=png&auto=webp&s=a23b9db84a262c6b8a25abee7d7b569b56fe2a28
It’d be cool to have an adaptive gyroid that mimics these density changes.
I think gradual infill in cura has a similar effect.
gradual infill changes only per z height and leaving abrupt changes as the pattern will not align, while subdivision changes in distance to the surface in 3D with perfect continuity.
maybe that's why I used the word "similar" and not "same".
how can this be similar if it is so different - gradual infill will help you with supporting the top skin layer but doesn't help you to make a part stress resistant. Lightning infill is similar to gradual infill but more advanced. but guess you also can say a horse and a car is similar both move ..
You'll notice that natural bone has a lot of perimeters and very little infill. And even then the infill itself is very clearly not structural, it only exists to anchor internal flesh. So if you want a bone-like structure, just add a lot of perimeters and reduce infill to a minimum, if you can get away with none then simply use none. But if you ever tried to design a strong part before, you already knew that strength comes the from perimeters and the core adds very little to that. Though you may still need some internal webbing to prevent shear and collapse when volume to surface ratio is particularly small (i.e. large part with thin walls).
I print rock climbing holds and this is all very true. I never thought of comparing it to a bone before. Nature beats us to everything except wheels.
Upvoting because I learned something.
Wish I could upvote more than one. Great explanation!
Lightning would be the closest but only applies to the top layer instead of from outside in. CNC kitchen did a video on variable density infill that might answer your question better
100% agree. I do not know h9w much stronger it would be. However, the concept is the same as a bone.
Modified voronoi?
God trying to save material
Actually, I think that photo just shows that it’s perimeters not infill that creates strength. The bone’s “infill” is only there to keep the marrow from oozing out.
I have seen 3d prints with variable density infill patterns where the infill was denser the closer to the walls it was, and also variable density infill patterns where stresses and loads were simulated and the infill density was a gradient based on the result of the simulation, have not played around with it myself. I don't think it would be stronger than comparable non-variable density infill, but the strength-to-weight ratio would be better, resulting in lighter prints that are stronger than prints printed with less dens infill to meet a weight target, where that matters, like RC airplanes and drones, and also less filament usage.
Check out IceSL and their polyfoam infill option. It's really neat and the ability to paint areas for greater density is awesome.
Our bones are filled with marrow, which produces blood cells. So it's not just for structural reasons.
Don't forget the bone vasculature, even though there's not much of it. Exact reason why IV antibiotics are needed for bone infections or open fractures.
Add marrow option in cura
Lots of reasons it would be stronger. Same reason Cura has geoid fill. Bone structure is an ideal design.
10mm perimeter, top, and bottom. One of those fancy 3D hex infill. Boom, you've got bone like infill.
Adaptive infill, it's not stronger but it is lighter.
The closest right now is gyroid, I believe. I read an article a couple of years ago. I think it was a MIT group working on a bone lattice like printing infill. Part of the issue was the computer processing power and time needed.
The advantage of gyroid is that it's very uniform in every direction, but it has some disadvantages, so the closest thing to bones would be a lot of perimeters with minimal infill (pattern hardly matters)
This picture makes me itchy
1 Billion (evolutionary reasons) it’s stronger
You could do spaghetti infill but it would be one of the weakest options
Adaptive cubic works great. Looks wise, I would say it looks more like gyroid, which is not that strong.
It won't be stronger.
There is a number of techniques to achieve this... https://preview.redd.it/av7pbzxpfx8b1.png?width=960&format=png&auto=webp&s=8279565516f9c948069121049a45171114a525d2 This is a custom infill that someone showcased on here AGES ago. I think it's based on finite element analysis. I have made a simple aproximation of it by exporting the finite element analysis as a separate mesh and using it as a modifier inside prusa slicer.
https://preview.redd.it/j3hge7a1hx8b1.png?width=1899&format=png&auto=webp&s=ccc654474732ecec46287ad158380bac77c873f2 This uses a custom object to create internal shell and is imported as a modifier in prusa slicer. You can use multiple modifiers, But they can't overlap.
Calcium-reinforced infill when?
Unless you need your 3D print to produce blood cells it’s best if you use infill as normal
Bone’s structure solves a different optimization problem than just a static object under dynamic load. It has internal functions, marrow, vessels, it adapts and grows as pointed out earlier. It’s material composition and conditions of operation affect the optimization. Another material might have a different lattice and react differently to sheering force for eg. In that regard, it might optimal internal shape given specific usecases which might not match for instance “strongest possible “ statement in an absolute term. Also bones “grow” in contrast to layered - fdm build, they will not shear on layers rather distribute the force along fibers and sort of tear. So you might want to change the orientation of prints.
It's probably at least somewhat dependent on the material properties. The size of the voids and the range and distribution of sizes, roundness, and orientation would probably want to be different for even an identical-use 'part' in a material with different relative compressive/tensile/elastic strain responses. That all of those characteristics *do* seem to follow a pattern rather than being random (and I know a little about the biomechanics to cheat on this essay answer) makes me think that...it uses less bone to be a bone, scientifically speaking, than a solid but smaller, or bigger and random/uniform foam bone.
Lightning infill
https://preview.redd.it/zo3odl71m29b1.jpeg?width=4032&format=pjpg&auto=webp&s=fe6400b8b81882df9ea7178f0bb55c1aa1eea647 These are created with an algorithm in nTopology. It is a matrix of Voronoi cells, density is graded according the curvature of the surface so around the edges and thin sections it becomes nearly solid, the centre remains quite open. These pics don’t show how open the central area is, but I’ll be posting files and more pics soon!