Why Choose Photochemical Machining?

 Why Choose Photochemical Machining?

If you are looking for precision, accuracy and repeatability in thin metal parts, photochemical machiningis the process you should be looking at. This photographic and chemical process can provide extraordinarily complex parts, to extremely tight tolerances, over and over again. Tooling costs are low, helping to keep prototyping costs down, as well as reducing the cost of design changes in the middle of a production run. Simplified tooling also reduces prototyping time, as there is little time lost to creating new tooling.

The tooling for this process is the “photo” part of its name. It consists of a negative image of the desired part, printed onto stabilized mylar film. The pattern for this is created in CAD software, working directly from the engineer’s design and ensuing perfect accuracy of the photo-tool. Changes require a new photo-tool being printed, a simple process that requires a trip back to the photo-plotter. Typically, two photo-tools are created, for the two sides of the part. They are either optically or pin registered to each other for accuracy. These can be as detailed or complicated as necessary, as added complexity does not affect the process in any way or add to manufacturing costs.

Using a photo process helps ensure part accuracy and consistency, as the UV light passing through the photo-tool does not affect it in any way. There is no wear on the tooling and therefore no need to replace or refurbish the tool after so many parts are made. The light passing through the photo-tool exposes a photosensitive film, attached to the metal to be machined. Once developed, the parts to be etched away are exposed, while the parts to be saved are covered by the film.

The process combines photography with chemical etching, giving us the “chemical” part of its name. This produces parts which are stable, where the intrinsic characteristics of the base material have not been changed and which have no burrs, eliminating the need for deburring operations. Because the machining of the part is accomplished by chemical etching, it works for any kind of metal, including metals which are normally difficult to machine. Etching chemicals are normally sprayed onto both sides of the metal, from multiple spray nozzles, to ensure uniformity. Once the machining is completed, the mask is washed off and the parts sent to final trimming.

Photochemical machining has been used successfully in numerous industries which need precision thin metal parts. It is a normal process in the medical, aerospace and electronics industries. Many types of consumer electronics are made with parts produced by photochemical machining.

Geraldine Robinson

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