Chemical Machining
Chemical machining can be used to etch steel, titanium, brass, nickel, copper and nearly every other kind of metal. Materials to be etched are generally thin sheets, although thicker plates may also be used in some instances. Electronics, aerospace, medical, automotive as well as publishing industries all commonly utilize this process in the production of metal parts. Specific examples of chemically machined products include stencils, plaques, printing plates, printed circuit boards, stamping dies, signs, jewelry, brake rotors and fuel cell plates. The popularity of chemical etching can be attributed to advances in chemical technology as well as the many benefits of this manufacturing process over more machine laden methods. The proper use of chemicals, for example, can easily work through even the most difficult of materials without the excessive thermal and mechanical stresses often resulting from tool usage. Options such as CAD and CAM support, design assistance and rapid prototyping extend the capabilities of this technique. Electrochemical and photochemical etching are specific types of chemical manufacturing that combine chemical usage with other processes for added precision and ease.
Although chemical machining differs based on the intended product, there are six main steps to any manufacturing process. First, the metal sheet to be etched is stripped of all oils and chemicals that frequently accumulate during forging and fabrication. Alkaline cleansers strip the unwanted organic materials while an acid cleaner removes chemical residue. Cleansing solutions must be efficient yet gentle enough not to scratch the polished metal surface. After sufficient cleaning, a masking is applied to the entire surface. Often tapes or paints, elastomers (rubber) or plastics, the masking is used to create the pattern for the shape that is to be cut into the metal. Excess masking is removed from the areas to be etched and the chemical, or "reagent", is applied. The composition of this reagent depends on the specific type of metal in use. Stainless steel etching and copper etching, for example, typically use iron chloride or nitric acid while aluminum etching uses sodium hydroxide. The specific chemical used, as well as environmental factors, determine how fast an etch or cut will be made and the degree of side-cut. Environmental factors to consider include temperature and agitation. After the acid has achieved its desired etch, both the reagent and the remaining masking are stripped. The metal is polished, any irregularities in the cut are burnished, and the machining is finished.
