B9Creator

"And now for something completely different..."
[www.kickstarter.com]

Wow, Michael, that looks Awesome! - Very good job on the design, that's had some serious thought and attention to detail.
Well done and enjoy the ride!

I can't think of a good python reference... so I'll just Say 'Ni'

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[richrap.blogspot.com]

Nice machine. When will you be releasing the files?

Also is there any difference between your machine and juniors on Indiegogo?

- Thanks!

- All CAD, Gerber and Source Files will be posted on b9creator.com once all backer commitments have been fulfilled.
I'm sure there are a lot of differences but I don't know the other design well enough to list them.

MikeJ

Hi

What's the estimated time to fill all orders and hence when we may see the files?

Nice design. Is the main innovation the resin? And why mount the projector underneath as opposed to above?

I've posted "August" as the delivery date for kits. So I'd estimate the end of August at the latest. If I find I have time to organize everything and get it posted sooner I will do that, but my first priority will be delivering the promised rewards.
Mike

Care to answer the second part as I am quite interested.

Sorry, completely missed that.
Photo-initiated polymer resins that react in the visible light spectrum aren't really new and there are open source formula's online: [3dprinter.wikidot.com]
Mounting the projector above would require a deep vat of resin, putting it underneath reduces the amount of reserve material needed.
The idea of using light radiation to solidify a liquid resin dates back to a patent by Charles Hull that is expired. The real trick to this process is how to separate the cured part from the projection glass. There are live patents that cover several methods, we've developed a method that does not infringe on those. Basically we coat the projection plane with a layer of PDMS which happens to be permeable to oxygen. The oxygen is an inhibitor and prevents a microscopic layer of resin from curing. That layer acts as a lubricant allowing us to slide the PDMS out from under the part to a deeper area of the vat. Once the part is over the "deep end" there is no longer a vacuum force holding the part to the projection plane and it can be easily raised for the next layer.
Hope that made sense?
MikeJ

So that's the reason for the moving vat?

But I guess projector from the top woud make it a simpler machine and enable large models as isn't gravity a limiting factor?

Edited 1 time(s). Last edit at 05/18/2012 02:20PM by gerards1111.

Right, we move the vat to release the object from the projection plane.
Top down would require a film and wiper to ensure a consistent layer between the last cured layer and the projection image.
Gravity hasn't been an issue for these objects, they are strongly attached to the aluminum build base.

Oh so the layer is partially stuck to the vat at the base and the previous layer?

I ask due to seeing the university experiment where the objects are made in a beaker with the focus at the top. Don't recall a wiper being used.

Yes, the resin cures like a glue.
I've seen those experiments and they demonstrate the basics of the process very well. But in practice, especially on a larger object, you must submerge the object deep enough so that the resin flows over it and then raise it to the next cure position (and the resin on top must flow off). Most "good" resin fluids are more viscous than those in the experiment and it would take a long time for the resin to flow off to a consistent .1mm or thinner layer (on top of the last cure layer). So to speed things up to an acceptable pace, the film/roller technique is used to squeeze out the excess and create a consistent thin layer to cure.

So you make the layer height by the distance between the base and top of previous layer?

For both our method and the top down method the layer thickness is determined as the distance between the last cured layer and the projection plane (surface for top down, vat bottom for bottom up). BUT, some areas (overhangs, etc.) won't have cured previously cured layers to "stop" the light from going too far. Both methods control that with pigments which absorb the correct frequencies and limit the cure depth. Exposure time is also a factor.
Mike

If I understand correctly your machine sets the layer by having the model the layer height from the base of the vat whereas the top down method needs to dip the model then wipe.

It was the Illinois video I watched. The quality does look great although the models are tiny.

I've seen that Illinois video, pretty inspiring stuff!
[www.nano-cemms.illinois.edu]

It is.

I must say though I am impressed with your metal folded design. Any reason for not boxing it in?

On the bottom? I like having the projector accessible and cooling is not an issue.
If someone was using it outside, in bright sunlight, sitting on a mirror ;-) there might be a problem with light pollution, but haven't seen any with normal indoor lighting.

Thank you for your frank and clear answers.