The Form1 and most SLA printers print from the bottom-up. Which we all know sucks for tank maintenance. What are the problems with just doing it from the top-down? I imagine a little loss of detail? Anything else? Maybe air does something to the process?
I expect there are patient issues and also the huge cost of having to fill a vat of resin before you can use the machine. I’ve heard it mentioned that to fill the vat on some commercial SLA printers cost $3k +. I expect changing materials isn’t that easy either.
Envision Tech does this I think there was one other company but I cannot remember the name. The video on the link shows the entire process.
http://www.directindustry.it/prod/envisiontec/stampanti-3d-85667-1476717.html
And these machines are in the $150,000-$250,000 Range
They do have smaller machines as well as machines for bio engineering (Dental/Medical) but I have never had those quoted to me so I have no clue the price.
Do you mean platform up vs. platorm down? If so platfom down for a consumer product is a bit much. Here are a few issues that make it harder to use a platform down printer.
First the entire build area must be full of resin. On a Form1+ that would be multiple litres, just to do your first print. This can be mitigated somewhat by limiting it to the height of the desired print x X dimension x Y dimension but that is still a lot of resin to be handling and swapping out every time you want to change materials.
Next problem is they are extreamly sensitive to being level. While this may not seem like much of a problem for most consumers it is. You could not set it on carpet, any table or desk you put it on must be very stable and on a very stable floor, and not move, even a three point level system can be a pain to level at times.
It’s also harder to maintain, this is mainly due to the volume of resin involved. Swapping resin requires bigger containers. Cleaning the excess resin off between resins is a formidable task. Filtering resin is a much bigger and more time consuming task. In general all resin handling gets scaled up.
I’m guessing there are some more good points but those are a few.
Even the Envision Tech machine is building from the bottom up. It just lowers into the vat instead of rising above it. This is the method used by the very first SLA printers, 30 years ago. They didn’t use a glass screen though but shot directly onto the very top of the resin. The big issue is that resin is trapped inside the piece and doesn’t drain like the Form 1 and others that print going up, not down. The early printers had issue with this and the parts had to be baked in an oven to harden the trapped resin.
A true “top down” print, say the Eiffel Tower, would only have the spindly top to support the build in the tank. that would surely lead to print failure. Otherwise a lot of supports would be needed so what would be gained?
I feel the 3D Printer market is going to go the same way the home computer market and others have gone. Everyone is going to jump in trying to make a killing but after a few years, maybe 10 or 20, there will be a shake out and only a few will remain. Just don’t feel that the general public will want to buy a 3D printer to design their own pieces or use stock drawings for replacement parts. Might be an opening for corner 3D printer shops just like Kinko’s and other quick copy shops are today. Just the view of an old man. 
- Walt
Thanks guys. I was thinking about how this would increase speed and reliability. And it would take less supports because the part would be almost weightless. I was thinking only of the Peachy Printer technique of floating the resin over salt water so you only loaded the resin you needed. But maybe some ingredients would mix during long builds? And yea like you guys said, the volume of liquid to maintain wouldn’t be fun. And trapped resin would create new issues. The Eiffel Tower would be oriented with the base down though so it would be stable. Thanks for all the replies! I was brainstorming and needed to get that out of my head 
Main disadvantages are resin price vs. printable volume and getting the resin to fill out the “layer” and settle between layers. Speed is actually lower for thick resins.
Also, it’s way messier. If you think draining the tank on a Form1 is a chore, just think what draining and cleaning a dozen or few dozen cm vessel is like.
Layer thickness control could also be an issue. When printing with the form 1 you always have two surfaces that the layer is constrained between (the build platform / half finished print and the bottom of the resin) allowing for layers to be consistent. Much more difficult doing it the other way.
3D systems uses a top-down machine. The results speak for themselves. They are the highest quality fine detail resolution parts I have yet seen in 3D printing. The technology is also very proprietary and patented. I believe they even brought a law-suite against Formlabs in the not so distant past, but it was resolved.
I have watched their machines in action first hand, and I can tell you, they work fantastically. They are not for the small fry though. Not only do they cost a bundle, they are not as versatile on a low budget. If you have a lot of money to spend, they are unbeatable.
I am pretty sure that’s what i.materialize.com uses for tech. Their material is a liquid, but their supports are like human hairs and their are so few it has to be floating. And overhangs are no issue. The results are mind blowing, it’s like seeing it on the computer screen. But alas, I have never seen this tech on a consumer level except peachy-printer. And that looks like true junk.
You are probably right on the i.materialize subject. Their printers get down to a 25-50 micron smallest FEATURE size. With all the advantages of a large printing volume (15X15X10 inches), and a laser smooth finishing path. They are used for medical tooling accuracy among other things. I was duly impressed with their powder deposition tech as well (that also prints top-down), but that is another topic. It almost sounds like I am an advocate for them, but alas I am nowhere wealthy enough to be. I just wanted to let you know that your idea not only had merit, it was the industry leading one as well.
I learned a lot, thanks.
I have never heard of a laser smooth finishing path. Is that like two passes at half power and at opposite angles?
No one said top-down isn’t superior, as far as the quality ceiling is concerned. The problem is - it’s impractical.
Expensively so.
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