DLP Metal Printing

Post, review and discuss any commercial machines. Try to include links, specifications and prices.
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DLP Metal Printing

Postby PacManFan » Tue Apr 15, 2014 10:49 am


Interesting technology, I'm wondering how it all works.

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Re: DLP Metal Printing

Postby AndersonTa » Wed Apr 16, 2014 2:47 pm

I'm curious about this too. Wonder if its as simple as us taking some ceramic powder and mixing with resin.

The thickness/viscosity of the resin would be a concern. I would think if you had it more "watery" than "paste" like, you would get a very porous structure when you fire the print and the resin burns out. That or you would need to play with particle size of whatever material to alleviate that issue.

But I think it's more or less creating a weak bond f whatever material and photocurable resin to create the desired structure, once its done printing, you put it in a kiln and have all the resin burn out all the while bonding whatever material.
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Re: DLP Metal Printing

Postby pizzaslice » Tue Apr 22, 2014 4:39 pm

It's complicated. You have to dissolve a fine ceramic powder in a solvent. To dissolve the alumina you can use a dispersant. A dispersant increases the separation of particles and prevents settling or clumping of the alumina. Then you add in the monomers and the initiators. You can use a speedmixer or 3 roller to blend it all.
So typically, your binder systems involves various components.
If you use a classical bottom up SLA process with a vat and silicone you can not have a very high volume fraction of for example alumina. Typically this will be around 50 % if you still want to be able to re-coat in reasonable times.
After illumination you obtain the green part. You then put it in the oven and melt out, the monomers, solvents, initiators etc. When this is completed you again put it in the oven and sinter the alumina. The part will shrink a lot during this process. If you don't do it correctly you will get cracks and pores.
I have never seen successful parts with a system similar to Envisiontec's perfactory.
One of the first companies to introduce printed ceramics was Lithoz, see for example the following Youtube video http://www.youtube.com/watch?v=jfdcJlfUGxo .
Specs of their process:
Lateral resolution 40 μm (635 dpi)
Building velocity up to 100 slices per hour
Slice thickness 25 – 100 μm
Number of pixels (X, Y) 1920 x 1080
Building envelope (X, Y, Z) 76 mm x 43 mm x 150 mm
Data format .stl (binary)
Light source LED

Probably, their different recoating mechanism allows them to use a higher volume fraction. If a high volume fraction is used, the whole process is simplified substantially. At the moment, alumina parts can only have wall thickness up to 1 cm.
Ceratec, a dutch company, bought a Lithoz machine an re-engineered the printer and slurry. In November 2013 they founded Admatec.


ps.
The article at 3Ders is about the printing of metal.The process is very similar to ceramics. One dude at ECN now does some experiments and so far this resulted in structures up to 100 layers. I guess he uses an admatec or lithoz machine. Layer thickness is around 10 micrometer. At a conference he has shown SEM (scanning electron microscope) images. I don't have them here, but I can guarantee that you can not distinguish individual layers (this is good). You will need a very special oven to sinter the metal.

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Re: DLP Metal Printing

Postby AndersonTa » Tue Apr 22, 2014 5:04 pm

I spoke with some NASA folks about this, this is apparently the same process they are using for printing ceramics for rocket engine parts and the likes. Speaking with the materials person, it really is more or less the addition of ceramic powders to a photocurable (UV resin). Granted all the factors we listed (particle size, specific ratio, etc.) play a large role in getting it just right. BUT yeah, weak structure embedded with ceramic powder and then off to the kiln like any other ceramic work piece.

And yeah, I know they are talking about metal in the 3ders article, but mixing "fireable" (as in a kiln) materials into resin is of interest. And I agree metals would be a whole other beast for the post processing...

Another little tidbit, its SUPER viscous...like 55K cps (ketchup/mustard consistency)...and they are using a top-down (SLA and DLP setups) approach with a wiper to redistribute after each layer.
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Re: DLP Metal Printing

Postby pizzaslice » Wed Apr 23, 2014 9:59 am

Following patent might be of interest:
Stereolithography resin for rapid prototyping of ceramics and metals
US 6117612 A


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