I'm a physicist in R&D, so most of my fabrication is for one-time or very small run prototyping. But I work adjacent to a real engineering department and am a t

I'm a physicist in R&D, so most of my fabrication is for one-time or very small run prototyping. But I work adjacent to a real engineering department and am a technical resource for them. I also have a side business making a little electronic gadget for a certain hobby. A lesson I've learned is: Never assume you know the cheapest / best way of making something. I've especially learned this from designers working in China, who have surprised me many times because they know their local industry way better than I do. Some techniques to keep in the back of your mind are punched and folded sheet metal, cast / molded aluminum, and vacuum forming. "Soft" mold tooling is cheaper than hard tooling. Vacuum forming is done with wooden molds. There are now some aluminum alloys that can be used for injection molding with short lifetime, but cheaper to machine than hard steel. Injection molding has a steep learning curve because of the cost of tooling plus issues such as mold flow, ejection, and shrinkage during cooling. You don't always get it right on the first try. Look for raw materials and parts that are close to the net shape that you want, and only need finishing or modification. For instance, "plate with holes" can be done with plates cut to size by a raw material supplier and drilled using a plywood jig with carbide drill guides. Try to attend the International Machine Tool Show when the pandemic cools down a bit. Just for inspiration. Bring good shoes.