Quote Originally Posted by Slatye View Post
I don't think so. Say you've got 1mm of resin on top of the water. Obviously for the first 1mm of the cube there can't be any water inside it; the water layer starts below the bottom of the cube. For the next layer (ie 1.01mm or so) the water is above the bottom of the cube, but it can't get into the cube because the walls of the cube prevent it. The only thing that can get into the cube is the resin, which goes right up to just over the top of the partly-completed cube. This continues all the way up; the cube sides are always just under the top of the resin layer, and above the top of the water layer. Therefore the water can never get in.

One thing to be careful of here is that you might need quite a lot of resin, even if you're not using the laser to solidify all of it. A 100x100x100mm cube will require a litre of resin even if you only actually use the laser to solidify the sides - the entire interior will be full of resin too. If you wanted a solid cube than that's no big deal - obviously a 1L solid cube is going to require 1L of resin.

What if you wanted it to be hollow with 1mm wall thickness (total volume of the finished cube 0.06L)? If you print it with a hole at the bottom it'll still require a full 1L of resin, because the hole will be covered by the build platform. Once it's finished you can take it off and drain the spare 0.94L of resin from it, but if you don't have at least 1L of resin to begin with then the job will never finish. Same applies to a hole at the top - you can get the spare resin back but you have to load the printer up with 1L of resin first. If, however, you have a hole very low on one side then the water will be able to flow into the cube during the build. Now you can get away with only having 0.06L of resin (or, more realistically, about 0.1L so there's a bit to spare) for the print job.
This is completly correct, Great Thinking everyone!