The good news is that I finally dusted it off and finished the build! There were a few small changes to the design.
The active tilt mechanism with the springs and stepper motor has been replaced with passive tilting. Now the tray is hinged on one side and is allowed to lift on one side as the build platform is lifted. The problem I had with the springs was there was too much play in the vat location. If I tightened it down so it didn't "wiggle" then it wouldn't tilt smoothly. I tested the passive tilt with some resin and it seems to work fine. If I lift the platform 1/8th inch the resin separates from the vat floor and the vat falls back to the level position (isn't gravity great!). For the vat floor I'm using a piece of 3/16" Plexiglas covered with a thin layer of Sylgard 184. I don't know how long the Sylgard will last so I have the frame set up so I can swap out the floor easily. I'll probably go ahead and make several from glass so I can scape off the Sylgard and re-coat as needed.
Since I no longer needed the stepper and axis for the tilt, I used them to add a red filter between the projector and the vat. It's just a piece of transparent red plexi that swings in front of the projector lens. This is useful because before I start the VB script Macro in Mach3 the projector is showing the Mach3 interface. Also, when the script is done it goes beck to a mostly white screen that would expose a lot of resin. I tested the filter and it seems to block all of the wavelengths that my resin is sensitive to. I also used a large piece of the red plexi to make a door for the front so I don't have to worry about ambient room lights.
I'm still tweaking the control macro and need to reposition the home and limit switches but the dry runs look good so far.
I promise it won't take another year for me to post some more. I've already started playing with some resin and should have some results soon.
