
Forget everything you know about 3D printing – the ‘replicator’ is here - chriskanan
https://www.nature.com/articles/d41586-018-07798-9
======
jtraffic
There are subtle differences between 3D printing types that seem at first to
be the same.

Stereolithography is horizontal, one layer at a time, and uses
photopolymerization (that's Formlabs). (Also Digital Light Processing is close
but distinct: [https://formlabs.com/blog/3d-printing-technology-
comparison-...](https://formlabs.com/blog/3d-printing-technology-comparison-
sla-dlp/))

Continuous Liquid Interface Production (CLIP) also uses photopolymerization,
but pulls the object from a liquid bath and uses a buffer zone. Still
horizontal slices. The upshot is it's much faster. (Carbon 3D is the company
behind this.)

The method in the article uses photopolymerization to solidify the object as a
set of slices, but the slices are not horizontal.

The big drawback to photopolymerization is it only works on certain resins
which can often have undesirable mechanical properties (high elasticity or
brittlness, for e.g.) Potentially this method could be a way forward in that
respect, because you might be able to put structural materials in the resin
solution and end up with a composite. It seems easier to do this way than with
CLIP or SLA/DLP, but I'm purely speculating.

~~~
qaute
Other well-known 3D printer technologies include:

\- Fused deposition modeling (FDM): the typical plastic filament-extruding
hobbyist printer. Low resolution, but fast and creates very strong parts in
one of wide varieties of well-known engineering materials. Tricks (e.g., two
extruders) can give limited multiple colors or materials.

\- Selective laser sintering (SLS): a laser melts a pattern into one layer of
powder at a time. Can make even stronger parts than FDM by using nylon,
titanium, etc. Very common in industry, but usually too expensive for
hobbyists. These are the printers used to make rocket engines.

\- Stereolithography (SLA) as explained above works like SLS but cures liquid
resin with light instead of melting powder. Has many subvarieties. Advantage
is scary high resolution (certain engineering choices give 160 nm (!) feature
size [1]), but at the cost of relatively limited material choices because
materials need to be liquid UV curable (though Form 2 has a good library now
[2]) and definitely no multi-material or color parts. I'd consider this new 3D
rotation printer a variety of SLA. [Edit: for clarity, I lumped CLIP and DLP
here with SLA]

\- Inkjet-based printers: these are the _really_ cool ones. Objet makes a
printer [3][4] that uses inkjet heads to deposit multiple colors and materials
in the same part layer-by-layer (kind of combining FDM and SLA). Upside is
multiple colors and materials and resolution (e.g., Lego uses these for
prototyping), downside is ridiculous price and low speed. Other printers like
HP's and Z Corp's combine inkjet heads with SLS powder instead.

There are also a few weirder ones, e.g., paper layering, but I don't think
they're widely used.

[1] [https://www.nanoscribe.de/en/products/photonic-
professional-...](https://www.nanoscribe.de/en/products/photonic-professional-
gt2/) [2] [https://formlabs.com/materials/](https://formlabs.com/materials/)
[3]
[https://www.youtube.com/watch?v=M1sOdZqwn5Y](https://www.youtube.com/watch?v=M1sOdZqwn5Y)
[4] [https://www.stratasys.com/polyjet-
systems](https://www.stratasys.com/polyjet-systems)

~~~
supermatt
One I came across today is SPD (Selective Powder Deposition). Powder is
deposited for later curing, such as in a kiln e.g.
[http://www.iro3d.com/](http://www.iro3d.com/)

------
black_puppydog
If I understand this correctly, there's nothing to stop them from...

* rotating the projector instead of the tube to reduce distortion from resin movement (like in a CT scanner)

* speeding this up, using higher energies to compensate

* using multiple projectors at e.g. 90degree angles, to reduce time (and thus probably distortions through movement in the resin)

* using other wavelengths with e.g. more energy, or just better absorption properties for the resin

or are there any obvious problems with that?

~~~
WhiteMonkey
The other benefit with having multiple projectors/lasers at different angles
are that you can use different wavelengths: one that causes polymerisation,
one that inhibits it.

------
jfoutz
steriolithography[1] is neat, and i think older than deposition style
printers.

This is kinda wacky. Rather than a conceptually simple layer by layer
approach, this has this funky convolution. they're getting it for free with
the simple rotation. You can kinda see how bulbous that airplane model is,
because some finer details get 'overexposed'. i bet, if they could rotate 10x
around 1 axis and 1x around another axis, that tumble would sharpen up some of
those edges, since you wouldn't be baking the same adjacent space so much.

Think about a 6 sided pencil. if you just rotate around the main axis, it's
probably going to look pretty round without the crisp hexagon sides. but if
you can also rotate around a minor axis, you could also project just the
hexagon shape for a while and still preserve the cone of the tip of the pencil
since most of the solidification came from the sides.

There's an opportunity for deep optimization there. Seems tricky. but pretty
cool.

it's almost like pca. what projection (or series of projections) maximize
hitting the target, and minimize the overbaking, all while taking into account
the characteristics of the resin. maybe you can let it cool for a bit, and
have more freedom to expose without hardening.

also, not a replicator. this is just one _fabulously special_ super material
you mess with, not metal and plastic and cloth and fur and chitin and
whatever.

[1]
[https://en.wikipedia.org/wiki/Stereolithography](https://en.wikipedia.org/wiki/Stereolithography)

~~~
Franciscouzo
I don't think it would be possible to rotate around another axis, the printed
object would start tumbling around the resin. If they rotated the projector
instead of the resin it would be possible.

~~~
eveningcoffee
Correct.

Their problem is that the projector they are using is projecting a 2D plane.

It would be a different story if it was a circular projector (think of a LED
strip).

It has to be then rotated only along a single axis.

Turning the projector circle physically can possibly add additional precision.

Magnetic fields can be used to keep the container sphere in place.

I am now going to take the screenshot of this conversation and send it to my
self in a registered mail.

------
AstralStorm
Uh, that's a standard resin printer. Except horizontal plus rotation instead
of vertical. Trades angular resolution for vertical.

Yes, they can be fast.

They should fix their headlines.

~~~
Leynos
Could multiple projectors (at e.g., 120 or 90 degree angles) be used to speed
the process further?

~~~
jfoutz
furthermore, multiple projectors could increase resolution.

if there's an energy threshold to overcome to cause hardening, and if you can
arrange for 2 sources to just barely exceed that threshold, then you could
have very crisp prints.

chemistry is statistical though. you can exceed the threshold, but nothing
happens because you get unlucky with some fraction of the light. You don't
exceed the threshold, but you catch a bad reflection and harden stuff you
don't want. and there's probably not a crisp threshold for hardening. it's
more likely just time under light.

But i think you're right. two projectors at half power (let's pretend it's
linear), with the projections 90 degrees out of phase, i think the print
quality would go way way up.

------
ricardobeat
These resin printers have been around for a decade. Multiple kickstarters,
several commercial models on sale right now.

To classify as a ‘replicator’ it needs to be able to mix different materials
(metal, plastic) seamlessly in one print as to be able to replicate itself.
Not there yet...

~~~
manjana
My thoughts. I remember Autodesk made a resin print of the Eiffel Tower and
some other object with plastic polymers catalyzed by light about 4 years ago,
there is a video on Youtube of it somewhere.

~~~
regularfry
This is much faster.

------
phkahler
>> The device, described on 31 January in Science1, works like a computed
tomography (CT) scan in reverse, explains Hayden Taylor, an electrical
engineer at the University of California, Berkeley.

I have been wondering if something like that was possible. I've also wondered
if something more akin to holography could be used to create a 3D interference
pattern in a liquid to create an object. Both seem like they'd be interesting
and have limitations.

From the comments here I think some folks don't realize the mathematical
details involved in this - they are not projecting a "picture" of the object
from each angle going around. Yes, it's an image, but not it's not what you'd
expect. It's more akin to an x-ray of the object, and probably with some extra
processing beyond that.

EDIT: Looks like I'm wrong. It says the create an image of what the object
would look like from each angle. I believe that means their quality is lower
than it could be had they actually used more sophisticated methods to create
the images.

~~~
goldenkey
Holography actually sounds pretty promising but the issue is that most
holography systems are phased (they trace the hologram with a single laser.)
If a holography with hjgh energy could heat up the inside shape of a liquid in
a beaker, it could turn it into a solid. The issue would be thermal diffusion
but if a dense enough liquid were used, it could work!

------
SideburnsOfDoom
So it can make you "tea, earl grey, hot" or anything else ... but made only
out of unbcoloured acrylic resin.

~~~
sgt
Take a break and enjoy some scolding hot resin.

------
andrewstellman
> _The team realized that the process could be reversed: given a computer
> model of a 3D object, the researchers calculated what it would look like
> from many different angles, and then fed the resulting 2D images into a
> ordinary slide projector._

I'm pretty sure the researchers were using a normal computer projector and not
a slide projector. But in my imagination, they printed a bunch of slides, fed
them into a carousel projector, and pointed them at an old Smuckers jelly jar
full of resin.

------
stubish
While you end up with an acrylic model, this should be suitable for lost-wax
style casting. Being able to create an unpixilated identical or scaled copy of
a model will be fantastic for fine art sculpture (or destroy the industry, if
copies become too easy to make). Just take your acrylic model, attach casting
channels, cover in ceramic, dry, pour in your bronze, cool, crack, trim,
patina, ship. Avoid all of the fiddly mold making and wax finishing
completely.

~~~
mkeeter
[disclaimer: I work at Formlabs, a 3D printing company]

This is already happening for jewelry, digital dentistry, and medical
applications – you can buy specialized materials for investment casting.

For example, here's our blog post on casting jewelry from resin prints:
[https://formlabs.com/blog/introducing-castable-wax-resin-
jew...](https://formlabs.com/blog/introducing-castable-wax-resin-
jewelry-3d-printing/)

~~~
stubish
Looking forward to scaling things up beyond teeth, earphones and jewelry. All
very promising though, and if the pixilization is solved that is excellent
(one of the foundrys here invested in additive printing systems about a year
ago, which then need the artist or laborers to resurface with wax before
casting). I imagine cost will certainly be a factor for larger systems (say
pieces 20-60cm height), both machinery and resins, because the profit margins
are very tight until you hit the big time. Is the waste castable wax resin
reusable?

------
pontifier
This is very similar to a patent I have filed on extremely fast 3D printing.

I have mentioned this method of 3D printing here previously. Transmitting data
to a volume at high speed can be done in many different ways, at any scale,
and with a variety of materials.

I hope to someday demonstrate the printing of a 2 story concrete house in an
hour using my technique.

~~~
DrAwdeOccarim
Has the application published? Would you mind putting the link here? I'd like
to read it.

~~~
pontifier
I'm not sure the application has been published by the patent office yet, but
I'll see what I can do.

Edit: Here's a link to the application on google patents.
[https://patents.google.com/patent/US20180257307A1/](https://patents.google.com/patent/US20180257307A1/)

------
wdutch
This is new to me and looks really cool despite the sensational style of
journalism. I imagine in the near future we will have a variety of widely
available methods for making physical objects from digital models, each with
advantages and disadvantages for different usecases.

------
gene-h
Something similar was proposed back when 3d printing as we know it today was
getting started in the 1980s. Two lasers were shined through a photocurable
resin so that the resin would cure at the interesection[0](see figure 9). In
practice it never worked and the resin cured before intersecting leading to
nasty blobs rather than parts. It seems that now that we understand the
kinetics of photocuring better and that we have massive amounts of computer
that we're able to use these approaches. Processes that cure resin have a lot
of potential because resolution can potentially be on the order of that of the
wavelength of light.
[0][https://pdfs.semanticscholar.org/4716/c69f0b90a158589e54248a...](https://pdfs.semanticscholar.org/4716/c69f0b90a158589e54248a524a57ad78f4a3.pdf)

------
_Microft
The speed is amazing but the amount of waste seems rather large as they most
likely can't (re)use resin that has already absorbed (an unknown amount of)
light before.

~~~
regularfry
It doesn't work like that. It's like a match: put enough energy in, and it
transitions to a new state. Put less than the activation energy in, and it
doesn't. The energy you've put in will be lost as heat, but the resin is
unchanged until it changes completely.

~~~
_Microft
There's a minimum amount of energy required for the process to happen. Below
that, it can not. Above it, things _can_ happen but how often depends on the
intensity of the light. Increasing intensity will make it happen a lot more
often. Some parts will receive far more light then others, making the
polymerization progress far enough to actually build a solid object while the
rest of the volume is illuminated little enough for the resin to basically
stay liquid. (Remember that you need to shine into the container, therefore
illuminating liquid that you do not actually want to polymerize but need to
shine through to reach the material that should. A sort of collateral-damage
if you like). The remaining liquid material is removed but will still contain
partially polymerized material that's not grown large enough to actually
behave like a solid.

------
exabrial
Sorry am I missing something? 15 years ago we had one of these in our
engineering lab. 3d Printing wasn't a rage term yet, it was called "rapid
prototyping resin machine".

~~~
Someone
Just as a computer tomography image is just a stack of 2D images, but can be
taken a lot faster because the tomography machine and its software (sort-of)
take all those images in parallel, this machine is just like a 3D printer that
hardens the resin one layer at a time, but a lot faster because it prints all
the layers at the same time.

Continuously illuminating the entire volume means you also illuminate parts
that should stay liquid, but you prevent over-illuminating those parts by
illum8nating from a lot of different directions, just as a CT image can see
transparent parts of a volume that are hidden by more opaque parts in some
views.

Another advantage I see is that this doesn’t need a start-stop motion that
lifts the object being constructed by a layer at a time or that raises the
surface of the liquid by the thickness of one layer, something that, AFAIK (I
don’t followed developments closely, so I may not know much) the traditional
printers need because they only can print at the air/liquid surface. Smooth
continuous motion is easier to build and faster.

------
sonusario
There is a more volumetric 3d printing method which prints all at once, no
rotation required: [https://www.llnl.gov/news/volumetric-3d-printing-builds-
need...](https://www.llnl.gov/news/volumetric-3d-printing-builds-need-speed)

------
yarovoy
This looks like it's wasting a lot of material comparing to DLP printers.

~~~
verroq
Maybe they can 3d print a custom container first

~~~
theyinwhy
Setup and fine tuning of such devices can take months so I highly doubt that.

------
singularity2001
I don't fully understand the process of creating 3D video from 2D slices. Is
that some sort of holographic procedure?

Presumably such a video could also easily be computed from CAD models, right?

~~~
yorwba
Reconstructing 3D models from 2D projections is a popular exercise in applied
linear algebra courses (actually, 2D images from 1D projections are more
common, because it's easier to visualize). The procedure is pretty easy to
code up once you've understood the mathematics. Essentially you build a system
of linear equations describing the influence of material density on the
measured intensity, then solve it for density given intensity.
[https://scikit-
learn.org/stable/auto_examples/applications/p...](https://scikit-
learn.org/stable/auto_examples/applications/plot_tomography_l1_reconstruction.html)

Generating projections from a model is much easier, because you only need to
write the rendering pass and don't have to invert it.

------
thecatspaw
This looks an awfull lot like 3d printing to me

~~~
ddeokbokki
In the sense that from a 2D representation a 3D object is created, yes, but
that's it.

------
lawlessone
Could this be used to rapidly store data as a 3d matrix?

------
agumonkey
inverse ct scan ?

fancy.

real fancy.

