3D printer isn't going to do it for you. There's now way a 3D printer will make 1
sign in the time you can make dozens with Photopolymer.
There was some really interesting stuff out there using vacuum forming I looked into about 6 months ago. I think it was an article in a
sign magazine about it and it lead me down the path. They talked about it replacing Photopolymer. I didn't bookmark any of the sites, but I do know that's how it was being done and the stuff looked awesome.