Build Your Own SLA/SLS

I'm really considering building a DLP printer instead of buying one. I've built some 3-axis CNC machines in the past so, I think these 3d printers won't be as (mechanically) complex as the CNC machines so am not afraid to go that route.

First question. What's the positive and negatives of a top-bottom and a bottom-up setup? I know top-bottom would require more resin and a deeper vat container, but most I've seen are small print areas.

Second: what's the limitations of the print area? Projector resolution seems to change the print size. Curious why couldn't we just set the projector further away; does it reduce the light required to cure the resin? I'm aiming to have a 7" x 7" print area but seems like most are in the 5"x3" size?

For those that built their printers, what's the time you've spent to get it up and running? A couple weeks, a couple months? I know it will vary pending on how long you spend on it, skill levels, etc.

Resolution will be inversely proportional to size. The highest resolution commonly available projector is 1920 x 1080 pixels.

Your size and resolution will depend on how you distribute those pixels over space.

So if you want 100 micron (0.1mm) XY resolution, you project to 192 mm x 108 mm. For 50 micron resolution, you'd project to 96mm x 54mm, etc...

You can probably achieve the size you want going up to 150 micron resolution, although your maximum printable area will always by 16:9, in proportion to the aspect ratio of the projector.

Light intensity on a given point will go down as area goes up, so your exposure times will get longer as you project bigger.

Thanks for the info on resolution, definitely helps explain the basics.