A New System Uses Sawdust to Print Wooden Objects

Black101 wrote: post #2

It is as strong as the binding agent... Why wouldn't you use 100% glue instead of sprinkling some wood dust in it? Sounds like Ikea furniture.

Fibrous composite materials can be significantly stronger than the source materials themselves. The binding agent forms a matrix which holds fibers together and so can be strong in localized fashion to hold fibers. This strength would usually result in the binding agent becoming brittle as a bulk material.

The overall strength comes from the combination of the two, with increased fracturing/tearing resistance due multiple independent fibers. Tears have a harder time propagating when each fiber needs to be fractured. Materials "fail" by cracks or fractures forming. In homogeneous materials the energy to continue a crack is generally much lower than continuing a tear. Sort of like static vs dynamic friction. Once started a crack will continue with a lot less effort leading to lower material strength. Fibers with a binding agent help prevent this effect.

A fantastic example of this effect is Pykrete which is just sawdust mixed into water before freezing. It becomes stronger than concrete (in tensile strength): https://en.wikipedia.org/wiki/Pykrete

Here's a link to a general material science intro on composites if you're curious: https://in.bgu.ac.il/engn/mater/Documents/LaboratoryBriefing...

Re: A New System Uses Sawdust to Print Wooden Objects

#5

Post by Black101 » Sat, May 08, 2021, 3:01 AM UTC

elcritch wrote: post #4

Black101 wrote: post #2

It is as strong as the binding agent... Why wouldn't you use 100% glue instead of sprinkling some wood dust in it? Sounds like Ikea furniture.

Fibrous composite materials can be significantly stronger than the source materials themselves. The binding agent forms a matrix which holds fibers together and so can be strong in localized fashion to hold fibers. This strength would usually result in the binding agent becoming brittle as a bulk material. The overall strength comes from the combination of the two, with increased fracturing/tearing resistance due mul…

I don't think saw dust is considered fibrous even if a tree is fibrous... I would think that to be considered fibrous, it would have to be longer in one dimension.

Re: A New System Uses Sawdust to Print Wooden Objects

#6

Post by MrYellowP » Sat, May 08, 2021, 7:17 AM UTC

chrispeel wrote: post #3

The company is Desktop Metal https://www.desktopmetal.com/ The technology is Forust: https://www.forust.com/ (why are neither linked in the Gizmodo article?!)

Thank you for doing their job right. To be fair, desktopmetal.com is at least being linked below, but after clicking it I simply felt mislead, consequentially closing it again.

Re: A New System Uses Sawdust to Print Wooden Objects

#7

Post by elcritch » Sat, May 08, 2021, 9:17 AM UTC

Black101 wrote: post #5

elcritch wrote: post #4

Earlier quoted context omitted.

Fibrous composite materials can be significantly stronger than the source materials themselves. The binding agent forms a matrix which holds fibers together and so can be strong in localized fashion to hold fibers. This strength would usually result in the binding agent becoming brittle as a bulk material. The overall strength comes from the combination of the two, with increased fracturing/tearing resistance due mul…

I don't think saw dust is considered fibrous even if a tree is fibrous... I would think that to be considered fibrous, it would have to be longer in one dimension.

Saw dust isn't an ideal fibrous material, but it's still primarily composed of fibers [see 1]. Really they're a bundle of fibers. On a macro scale it makes less sense, but on a micro-scale the fibers are much longer than the micro-cracks that begin to form in materials under strain and which lead to the loss of strength or fracture we normally think about.

1: https://www.sciencedirect.com/science/article/pii/B978012814...