Chemical milling, also known as chemical etching, is the process of using chemicals on materials to etch, cut, or engrave specific designs or patterns.
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Applications of Chemical Milling
Almost every type of metal can be processed with this technique, including steel, titanium, brass, nickel, and copper. Etched metals are usually thin mediums such as sheet metals or foils, although thicker metals such as coins and plaques can be etched as well. Chemical milling is commonly used to create parts such as stencils, plaques, printed plates, circuit boards, and foil-stamping dies. It is considered a specialized process.
Process of Chemical Milling
Certain acids or chemicals react with metals to dissolve them, and thus lines and holes can be created in a piece of metal using the application of these specific acids or chemicals. In the process of chemical milling, the metal sheet to be etched is cleansed thoroughly before the masking layer is applied. Masking is often made up of tapes or paints, elastomers, plastics, or by a photoresist in photo etching, and it is applied to the areas of the metal sheet that are not to come into contact with the etching acid. If tape is used, a pattern can be cut into the masking layers using a scribe and peel method. The metal part or sheet is then exposed to the chemical or reagent in order for corrosion to occur. When the reagent is applied, many factors are considered to determine how long to leave it for including temperature, agitation, acid concentration, and the desired depth of the cut or etch. After the desired result is achieved, the chemical is stripped off the part and it is polished.
Benefits of Chemical Milling
Chemical milling is a specialized process that can save manufacturers time and money if implemented by qualified personnel. The process involves hardly any mechanical work, but it is necessary to understand the different chemical concentrations in relation to their reaction with certain metals. It has become increasingly popular as chemical technology has improved. Compared to mechanical milling which requires costly machinery and maintenance, as well as individual milling, chemical milling is a faster and more economical method of metal engraving. Larger OEMs and industrial machinists are turning to chemical and photo milling as it is also a viable alternative to stamping and laser or water-jet cutting for precision parts. Tooling is relatively cheap and the process can result in finished components in a matter of hours although many hobbyists, artists, and small manufacturers still prefer hand engraving over chemical or mechanical for a personal and more organic finish to their metal etchings and engravings.