Forget everything you know about 3D printing – the ‘replicator’ is here • Hacker News Board

Re: Forget everything you know about 3D printing – the ‘replicator’ is here

#51

Post by Someone » Fri, Feb 01, 2019, 9:34 PM UTC

exabrial wrote: post #41

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".

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.

Re: Forget everything you know about 3D printing – the ‘replicator’ is here

#52

Post by Someone » Fri, Feb 01, 2019, 9:51 PM UTC

singularity2001 wrote: post #16

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?

Producing 3D images from 2D slices is easy. The problem is that the 2D images that a CT machine makes aren’t slices, but projections of the 3D volume onto various planes.

For example, if your image is

    .........
    ..x...x..
    .........
    ....x....
    .x.....x.
    ..xxxxx..
    .........

an image taken vertically will count the x-es in each column:

012121210

and one taken from the left or right will count them in each row:

Those 2 projections (probably; I haven’t checked this image) aren’t sufficient to reconstruct the image, but they already add significant constraints. For example, those 5 X-es in the next to last row can’t be in the first or last column (if they were there, the first image would start or end with a non-zero value)

The more projections you add at other than orthogonal angles, the more constrained the solutions become.

Re: Forget everything you know about 3D printing – the ‘replicator’ is here

#53

Post by tdeck » Fri, Feb 01, 2019, 9:57 PM UTC

qaute wrote: post #43

jtraffic wrote: post #34

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-... ) Continuous Liquid Interface Production (CLIP) also uses photopolymerization, but pulls the object from a liq…

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 a…

Another con to resin based approaches that's not always obvious is that some of these resins are pretty nasty and dangerous to touch when wet or pour down the drain. That makes the cleanup process a pain, at least in the context of at-home or small-scale printing. Powders are aslo a big pain but they're too expensive anyway.

Re: Forget everything you know about 3D printing – the ‘replicator’ is here

#54

Post by WhiteMonkey » Fri, Feb 01, 2019, 11:20 PM UTC

black_puppydog wrote: post #21

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…

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.

Re: Forget everything you know about 3D printing – the ‘replicator’ is here

#55

Post by goldenkey » Sat, Feb 02, 2019, 2:15 AM UTC

phkahler wrote: post #37

>> 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…

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!

Re: Forget everything you know about 3D printing – the ‘replicator’ is here

#56

Post by stubish » Sat, Feb 02, 2019, 8:25 AM UTC

mkeeter wrote: post #39

stubish wrote: post #2

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 fidd…

[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...

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?