I have made two attempts to laminate with silicone and both have failed. The first was a technique issue - I don't have a press so I'm using multiple woodworking clamps. I had two issue with my first attempt - I poured the entire amount of adhesive in the center of the plate, but it never worked its way to the outer corners - I was hoping this would avoid bubbles and gaps. The other issue was that the PEI kept sliding around on the adhesive and was way off center on the plate. I worked with it until the silicone started to cure and aborted.
A couple weeks later I tried again. This time I spread the silicone plus spacer beads (I'm using a 1/4 tsp of the beads mixes in with the adhesive) with a credit card so I had a thin layer over the whole plate. I also printed up some guide blocks to keep all the plates centered using bar clamps across the length/width. So two bar clamps across the width, two clamps across the length, and a total of 6 clamps on the thickness including two hefty 6" C clamps. I'll try to remember to get a photo of the arrangement next time, it's such a mess of clamps it might be hard to see what's going on.
I let this cure clamped for 24 hours. I then released the clamps and set the plate sandwich on the printer bed with a heavy plate on top - heated it up to 50C and let it sit for another 24 hours. The PEI peeled off like release paper on a sticker. It didn't bond at all. I had tested a small drop of the silicone on PEI and seemed like I got a great bond. The silicone also didn't bond in the center of the aluminum. It must have been a curing issue (which I though might happen) because the silicone outgasses a lot while curing. The silicone around the edges of the plate did stick to the aluminum.
So now the search is on for a low-viscosity, budget priced epoxy. I haven't bought anything yet. The epoxy will make for a more challenging clamp job as I think I'll have to bag the print bed before clamping or my entire arrangement will become one as the glue oozes out from the print bed.
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