
Soft Silicone Pneumatics Are 3D-printed in a Tub of Gel - beardicus
https://hackaday.com/2018/11/27/soft-silicone-pneumatics-are-3d-printed-in-a-tub-of-gel/
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CodeCube
I'll admit that I'm not a scholar on the matter, so this may just be ignorance
speaking ... but I wonder why all the soft robotics stuff that I see never
seems to pair the soft/flexing actuators with any rigid components?

I'm thinking of the analog to the human body (or animals) ... we have a
skeleton, organized and connected via ligaments, and then our "actuators"
(muscles) attach to that structure with tendons.

Is there any existing research/samples/demos that mimic this structure?

~~~
vlehto
Elastic materials are often avoided if you need either linear movement or
accurate position control.

Elastic materials are favored if you need shock absorption or no seal system.

Both hydraulics and pneumatics suffer from incredibly shitty thermal
efficiency. Electric engine can be 99% efficient. Any single pair of gears or
a chain drive can be 99% efficient. Typical hydraulic actuator is something
between 70 - 40% efficient. Pneumatics are as bad or worse.

They do use rubber air bellows in paper machinery, but it's being replaced by
rigid hydraulic cylinder actuators. With pneumatics you can have somewhat
accurate force (== pressure), but you never know the accurate position. With
hydraulics it's the other way round. As a result, hydraulic actuators can be
mounted in any position regardless of gravity. So you can use the same
machinery in various positions.

Edit: here is more if you're interested:
[https://www.machinedesign.com/pneumatics/primer-flexible-
act...](https://www.machinedesign.com/pneumatics/primer-flexible-actuators-
and-their-uses)

~~~
Groxx
why would you not know pressure with hydraulics? seems like you could detect
back-pressure at the pump fairly accurately. or is that not a cheap thing for
e.g. the electric motor driving it to support?

(probably-obvious disclaimer: I have zero experience here, so I truly don't
know)

~~~
vlehto
I was cutting corners a bit. Here's more in depth:

You can always read very accurate position with pneumatic actuators. You just
can't keep it very accurately in place in dynamically loaded situation. You
can also read the force of hydraulic system, but you cannot keep it constant
as easily in dynamically loaded situation.

If you want (roughly) certain force and you don't care about precise position,
then you have lot's of advantages from pneumatic system. The whole volume of
the system acts as "hydro-pneumatic accumulator". Which means that the whole
volume of the system is trying to average out the change in force. And you get
that free of charge. And also you don't have to invest any money into
hydraulic fluid. Air is free and available (almost) everywhere.

If you then insist on hydraulic system, you have to put separate hydro-
pneumatic accumulator. But because almost any hydraulic fluid is heavier than
any given pneumatic fluid, you have more mass in any given pipe section. That
means the system will react slower to any(?) pressure increase. You can read
the pressure very accurately, but you cannot smooth it out as fast as pure
pneumatic system would.

There are caveats though, sound can travel very fast in hydraulics. And
turbulence can eat out pressure very quickly. I'm kinda professional in the
business, but still starting out.. :D So take this with pinch of salt.

PS. Hydraulic systems can handle 60 bar safely, while 6 bar pneumatic system
can already explode and be quite dangerous. That's sometimes enough of a
reason to go hydraulic.

~~~
Groxx
Aah, gotcha. yeah, maintaining (near) constant pressure would require a lot
more work / faster reactions because hydraulics are incompressible. That makes
sense. Thanks for the summary!

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Isamu
This is a project coming from the self-assembly lab, which has a number of
interesting things brewing:

[https://selfassemblylab.mit.edu/](https://selfassemblylab.mit.edu/)

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londons_explore
The gel printing method looks very promising for printing other 3d objects.
Current systems require support material or special designs without overhangs.
The gel approach seems better in nearly all respects.

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pontifier
I'm quite impressed by this. The integrity of the parts seems quite good.

I've filed a patent on some 3d printing methods similar to this, but with a
focus on ultra quick printing. Once people understand how fast these things
could actually work, many things will change.

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mpolichette
So, this is the start of westworld?

~~~
DonHopkins
Or Alien!

[https://www.youtube.com/watch?v=rrf0cH4o_g4](https://www.youtube.com/watch?v=rrf0cH4o_g4)

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fallat
I will pay for the first printed seat cushion. I expect such a cushion to be
pretty cheap based on the paper detailing the materials used.

~~~
bsder
You could probably get this from Carbon3D right now:

Caution: Marketing articles
[https://money.cnn.com/2018/07/06/technology/adidas-
speedfact...](https://money.cnn.com/2018/07/06/technology/adidas-
speedfactory/index.html)
[https://www.carbon3d.com/stories/adidas/](https://www.carbon3d.com/stories/adidas/)

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blorenz
This is going to disrupt balloon artistry!

