A specific type of metal etching, photochemical machining—also known as photo etching—is the ideal way to economically produce complex parts with fine detail. Fundamentally, photo etching is similar to other types of metal etching. A coating is applied to a sheet metal surface, and acid is used to dissolve away exposed areas.
Unlike other etching methods, however, photo etching involves the use of hardened photographic film. The film shows the negative image of the part to be created, and two identical sheets are applied to the front and back of the sheet metal. That assembly is then laminated with a UV-sensitive photoresist, which hardens only around the clear areas of the film. The outlines of the parts are left unprotected by the resist, and when the assembly is bathed in an acidic solution, that outlining material is washed away, leaving only the parts of interest.