or gallery here:
http://imgur.com/a/GcVkK
The poly is mill slotted on the bottom and sides so it's super tight once it's bolted together. 100% Silicone seals it up nicely without the need for messy and toxic weldon glues. The "double waterfall" insert is removable but stays in and is sealed up against the edge of the glass so no bubbles can flow through into the PDMS from the bottom. When used with 200 degree oven, only requires 45 minutes cure time as poly can handle up to 300, and easily the full 200 degrees the PDMS can. So it's fast!
Re coating procedure: Preheat oven to 200, add some blue removable tape as a temporary dam at the edge of glass. Add mixed PDMS and spread to all four corners of glass. Level out for a couple of minutes and pop all bubbles with toothpick or pin, (otherwise they will set up permanently at this fast cure rate). Remove blue masking tape and place VAT into preheated (super level inside) digital toaster oven.I have a glass shelf inside the oven so there is a solid flat surface for the vat to rest on. I also use a tripod laser level to level the glass shelf (that calibrates off of gravity).
Clean up: Poly is alcohol friendly so cleanup is a snap. Spray in a bit of alcohol to loosen up resin, and then soap and water- I like using an alcohol saturated microfiber cloth (same kind for cleaning glasses) to wipe the PDMS clean before next use. Glass window can be cleaned squeaky clean so PDMS sticks well. Inside edges can also be wiped with alcohol prior to re coating so it sticks super well, (almost too well). But is helpful when using certain resins that wanna rip it off the floor: )
Prep for re coating requires a razor blade to scrape here and there, and a bit of removal down in the lower falls- milled section of the bottom plate- so the next batch of PDMS can seal tightly to the floor, but clearing out the holes is not necessary, as the next batch just adheres to what's left inside of them.
No meniscus issues whatsoever! I found out the hard way that dams and inserts level with the PDMS surface can cause those issues, thus the double waterfall design provides a way for the PDMS to flow under the bottom fall where it seals up securely.
PDMS cures flat and even as the first waterfall is identical to the standard vat. When placed in a preheated oven, the PDMS cures fast enough so it only flows over down into the lower waterfall lattice (in the deep end) and not much further beyond that. Only requires 20 to 25 ml to cover that way. I also add a touch more activator to toughen it up a bit. Could get away with as little as 15ML bit would be on the thin side. : ) Resulting PDMS Waterfall is super nice radius, smooth, even and meniscus free. (will update with pics of a coated VAT when I get a chance, : )
So that's what's possible, I say we continue to make this even better and easier, but for me this is the ultimate, as it doesn't get much better than this!
Best, Kirk
: )
