
Powder metallurgy - glassworm
https://en.wikipedia.org/wiki/Powder_metallurgy
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milkey_mouse
A related method not mentioned in this article (or, in fact, many places at
all) is iro3d[1]'s "selective powder deposition": a 3D printer effectively
creates a mold out of sand, with empty spaces filled with a metal powder.
After the "print", done in a crucible, is finished, an ingot of metal with a
lower melting point is set on top & the whole thing baked in a kiln. The metal
from top fills the space between the granules of powder and solidifies with
nearly no shrinkage (as the object is mostly made of the powder, which never
melts).

[1] [http://iro3d.com/](http://iro3d.com/)

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falcolas
3d printing is mentioned, under the additive processes.

It’s most likely not emphasized since the resulting product may have the size
tolerances, but not the strength of the powdered metal. It’s still quite
strong, but the strength is based off the “filler” material (similar to brazed
parts), not the powdered metals (which acts more like rebar inside concrete).

I imagine this lack of strength (or lack of integration) of the original
powdered material is what holds it (and other similar additive processes) back
from being a well recognized PM process.

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mikejharrison
Over the years I’ve seen a couple of fascinating applications with powdered
additive manufacturing. Living metal - powdered metal parts with bacteria ‘in
the gaps’. Activated with heat their byproduct was lubricant. Great for
bearing faces in mechanical equipment doing long distances in space.

The other was calcium powdered 3D printed parts that had a chemical forced
through their porous mass, changing its chemical composition.

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hwillis
The specialist applications of powder metallurgy are awesome, not to mention
the fact that lots of refractory metals can _only_ be used with sintered
powder (eg tungsten). It should also be pointed out that powder metallurgy
parts have long been an important part of engineering (mostly sintered bronze
bushings impregnated with grease), and have recently become hugely common as
powder gears.

Manufacturing standard spur gears in particular has benefited HUGELY from
powder metallurgy. You can use it to make exceptionally accurate and cheap
extrudable shapes, and gears have traditionally been hugely expensive and
wasteful because you have to cut out the teeth, harden, and final-cut. Powder
metallurgy has created an important middle ground- exceptionally cheap medium-
quality gears. Now instead of unhardened gears you will always get powder
gears, which are better. In places where final-ground gears were overkill,
powder gears have come in at acceptable quality and greatly reduced prices.
Powder metallurgy is awesome!

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yetihehe
> Now instead of unhardened gears you will always get powder gears, which are
> better.

Nope, now instead of unhardened gears you get powder gears which are even
worse (but much cheaper than those good powder gears), but minimally better
than plastic. My father is power tools' serviceman and since sintered gears
became more common, there are MUCH more broken transmissions (but yeah, they
are a little cheaper).

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fredley
Turns out I already knew roughly how this process works from playing Factorio
with Bob's/Angel's mods. It's relatively 'realistic', requiring crushing ores
and sorting to get different breakdowns of products (And byproducts), further
processing those products to get powders, recombining, sintering and pressing
into pellets.

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artpop
Or in a slightly more exciting format:
[https://www.youtube.com/watch?v=g7H0YFFV_oE](https://www.youtube.com/watch?v=g7H0YFFV_oE)

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glassworm
[https://en.wikipedia.org/wiki/Selective_laser_sintering](https://en.wikipedia.org/wiki/Selective_laser_sintering)

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iamgopal
The single limiting factor against high production and good dimension
advantage is Raw material production.

