Stereolithograpy revisited

OK I will be honest I have never worked directly with this
technology. I have used sample parts made from it. AND one jewel of
this is the fact that you can make investment casting patterns which
will yield final castings which appear nearly diecast quality or
better.

I DO work with Nd-YAg and HeNe lasers.

The STL process as I have seen it lowers a part platform into a
resin tank then raises the part just above the resin surface. A
gantry like squeegee removes excess liquid resin (leaving a specific
film thickness) before the laser rasters the current part slice.

Laser power and speed plus film thickness determines how many layers
or slices it takes to build up a given part thickness.

Solid sections are often done as honeycomb to speed up build process
(this is a special function of some proprietary systems)

Since the dip/wipe time are the big speed limiting factors a long
shallow part is grown much faster than a tall narrow one.

I think the Solid/overflow issue is like Ice in a drink - the fact
that ice melts to become a liquid verses resin photoreacted to a
solid - still is the same total mass/volume, or near enough.

The biggest costs will be the optics, laser, powersupply and cooling
system if needed. - The biggest hurdle would be the dedicated
software to operate the machine.

If some were serious about building one I would be interested. I
can't code "C", know enough about electronics not to let the magic
smoke out or light myself up and am a machinist by trade. (Mainly
CNC but also tool and die work.)