Re: 1/2 scale Atlas from Portal 2
So I got a couple good castings from the hemisphere mould, and used a slitting saw on the mill to cut them just under the half way mark. This was a sketchy operation, after I took these pics, I switched to a smaller, thinner slitting saw with a much higher tooth count, which made things much smoother.
Then I cut the eye hole
I put the halves back in the mould vertically and bandaged them together with fiberglass from inside, working through the eye hole and making a complete sphere. Then I got the 16 parts that went around the prime meridian located and tacked in place with super glue, sealed all the seams with frog tape, and then filled with Smooth Cast 325.
After all that, used a slitting saw again to cut just above the halfway point to make an access panel in the back of the body.
I used some rare earth magnets to attach this panel for fast access.
The eye bezel was actually another major mistake, the renderings we had didn't include the white halo around the blue iris of the eye. So we had all our vacuum forms made for the bezel, and then realized we would need new ones to allow for this halo. So we re-vacuum formed the original form, dusted it with talc as a release, and vacuum formed over that again, so we had two layers.
Then the top layer went into the laser cutter, and once we calibrated it correctly we were able to cut the halo out of it. So the lower layer was vacuum formed clear PETG, which we sprayed with a glass frosting spray, and the top layer was painted black and applied, leaving the frosted layer showing through from below in the area of the halo. When backlit, the halo glows white.
The iris was modelled and assigned a translucent blue right in the modelling software, so we could render it with a backlight and tweak the geometry until it looked just like the desired result. So then we had it printed in "supreme clear" which looked like this
and we gave it a few coats of Tamiya clear blue, as well as a few coats of the glass frosting spray