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Photographic chemical etching, also known as photochemical machining (PCM), photochemical milling, or photo etching or chemical etching is a precise manufacturing process used to create intricate metal components with high accuracy and intricate designs. It involves using a combination of light, chemicals, and a photoresist to selectively remove material from a metal sheet or plate.

The process begins with the preparation of a metal sheet, usually made of materials like stainless steel, brass, copper, or aluminum. The sheet is thoroughly cleaned to remove any contaminants that may interfere with the etching process. Then, a photosensitive material called a photoresist is applied to the sheet metal surface. The photoresist-coated metal sheet is exposed to a high-resolution photographic image, typically through a contact printing method or by using a phototool, which contains the desired pattern or design.

The phototool acts as a mask, allowing light to pass through specific areas and blocking it from other regions of the photoresist. After exposure, the metal sheet undergoes a chemical development process, which removes either the exposed or unexposed areas of the photoresist, depending on the type of photoresist used. This leaves a precise pattern of photoresist on the metal surface, corresponding to the desired component design. Next, the metal sheet is immersed in an etchant solution that selectively dissolves the exposed metal areas not protected by the remaining photoresist. The etchant removes material vertically and laterally, resulting in highly accurate and detailed features.

The etching process can be controlled to achieve specific tolerances and depths. Once the desired level of etching is achieved, the remaining photoresist is stripped off the metal sheet using appropriate solvents. The metal component is then thoroughly cleaned, inspected, and post-processed as necessary, which may include additional machining, plating, or other finishing operations. Photochemical etching offers several advantages over traditional machining methods, such as its ability to produce intricate and complex designs with high precision, rapid prototyping capabilities, cost-effectiveness for small production runs, and compatibility with a wide range of metals and alloys. It finds applications in various industries, including electronics, aerospace, automotive, medical devices, and more.