4 ms·

A New System Uses Sawdust to Print Wooden Objects

10 points by chwolfe 5y ago

Black101 5y ago
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.
- elcritch 5y ago
  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 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/LaboratoryBriefings/4/Materials%20Science%20and%20Engineering%20introduction%20Chapter%2015%20Composites%207th%20ed.pdf https://in.bgu.ac.il/engn/mater/Documents/LaboratoryBriefing...
  - Black101 5y ago
    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.
    - elcritch 5y ago
      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/B9780128142400000021 https://www.sciencedirect.com/science/article/pii/B978012814...
chrispeel 5y ago
The company is Desktop Metal https://www.desktopmetal.com/ https://www.desktopmetal.com/ The technology is Forust: https://www.forust.com/ https://www.forust.com/ (why are neither linked in the Gizmodo article?!)
- MrYellowP 5y ago
  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.

10 points by chwolfe 5y ago

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.

elcritch 5y ago
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 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/LaboratoryBriefings/4/Materials%20Science%20and%20Engineering%20introduction%20Chapter%2015%20Composites%207th%20ed.pdf https://in.bgu.ac.il/engn/mater/Documents/LaboratoryBriefing...
- Black101 5y ago
  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.
  - elcritch 5y ago
    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/B9780128142400000021 https://www.sciencedirect.com/science/article/pii/B978012814...

chrispeel 5y ago

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

MrYellowP 5y ago
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.