
Amid heavy competition, Relativity Space secures $140M in funding - rbanffy
https://arstechnica.com/science/2019/10/amidst-heavy-competition-relatively-space-secures-140-million-in-funding/
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tzfld
Wondering if a complex machine like an orbital rocket could be 3D printed as a
whole and not just the components separately...

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varjag
Sintering (the most popular industrial 3D printing process) typically involves
a substantial manual/machining component after the print. Also any precision
elements or bearings rule out 3D printing. So, no.

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AllegedAlec
Not only that, but sintering is also (generally) a lot less sturdy than a
completely machined part.

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whenchamenia
The new sintering processes and alloys have gotten amazingly close for most
purposes to be indistinguishable in application. Like any additive process, it
still often requires machine work where precision is important.

Tht said... I am sad to see that lately, casting being overlooked often when
it is still the best choice in many projects just because '3d printed' sounds
better in the marketing. I have in front of me a 1960s magnesium alloy casting
from the early 60s and the quality would make most sinterig operaters beyond
jealous. Not to mention the material properties.

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varjag
Yes, diecast components can be very precise. At the same time diescast process
is cheap enough that 3D printing has no edge there.

Where 3d printing really helps is replacing wax or investment casting
necessary for high melting point materials. You end up having quicker
turnaround, better part quality and sometimes even lower price.

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Robotbeat
This is probably the most expensive way to make a rocket body I can think of.

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mrfredward
Furthermore, it will give inferior material properties and potentially have
more quality/repeatability issues.

They must believe that more complex designs can more than make up for the
disadvantages of 3d printing. That is hard to fathom for a thin walled
pressure vessel like a rocket body, but I'm sure they know things that I
don't.

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rbanffy
The main advantage of additive is automation. You can 3D print a lunar habitat
with a Fresnel lens, a remotely operated robot, and sunlight well before
humans install and inflate an internal pressure vessel. If you could do that
with metals on the moon or, better, on an asteroid, you'd have a lot of parts
that'd need minimal human intervention before being used.

Even if not as practical, or high quality, or light, it means huge savings.

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Robotbeat
That's the "freshman's dream" of additive manufacturing. In reality, additive
manufacturing is often _more_ labor intensive than conventional manufacturing,
particularly if you're building multiple items or are using the process where
it doesn't make sense.

The "minimal human intervention" thing is just not true.

It's nice to not have to make tooling. But post-processing is super labor-
intensive. Often post-machining is also needed. And certification of additive
parts for aerospace is a _nightmare_.

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rbanffy
These are all limitations of the process itself, but we can design around
them. If the printed material is not rigid enough, we make it thicker or add
support structures. If the surface is not as smooth as we need, we can machine
it or use a thicker gasket. A lot of our tech and tooling is built around
subtractive processes and their characteristics, but that's not a hard
boundary of the design and process space.

