Indian Institute of Technology, Kanpur
PHOTOCHEMICAL MACHINING (PCM)
ME662 Advanced Machining Processes
Tarun Mankad Y4456
October 05, 2007
ADVANTAGES OF PCM
LIST OF ILLUSTRATIONS
Illustration 1: the current PCM process
Illustration 2: process flow-chart
Illustration 3: etch profile development with time
Illustration 4: existing Regeneration Systems
Illustration 5: problems with different regeneration methods
20 Illustration 6: disposal of waste elements
Illustration 7: idealized PCM process of the future
LIST OF TABLES
Table 1: different etching technologies and products
Table 2: PCM etchants
Table 3: cost drivers
Photo chemical machining is an engineering production technique for the manufacture of burr free and stress free flat metal components by selective chemical etching through a photographically produced mask.
Photochemical machining (PCM) is one of the least well-known non-conventional machining processes. The technique is relatively modern and became established as a manufacturing process about fifty years ago. PCM is also known as photoetching, photochemical milling, photomilling, photofabrication, photochemical etching and (in the USA) chemical blanking. The processing technology has been kept a closely-guarded secret within a small number of industrial companies but despite this, the sales of parts made by PCM at the end of the twentieth century was approximately US$ 6 billion.  The PCM industry plays a valuable worldwide role in the production of metal precision parts and decorative items. Parts produced by PCM are typically thin, flat, and complex. These parts have applications in electronics, mechanical engineering, and the aerospace industry. The increasing popularity of industrial applications, together with greater competition, means that there is a need to understand the costs involved in PCM so that the right technology can be selected for manufacturing.  PCM is generally categorized as a two dimensional manufacturing methodology, but the recent developments ,as well as, the work still being carried out in this direction, further widens the applicability of this process. In order to compete with traditional manufacturing processes, PCM has undergone many process modifications in order to comply with a plethora of legislation and regulations aimed at protecting the environment. These modifications have greatly reduced the environmental impact of the process and the drive to reduce it further continues. The environmental effects can be appreciable in view of the nature of the industry whereby various chemicals are used in the preparation and cleaning of metal surfaces, photographic processing of photo-tooling, coating and selective removal (development) of photo-resists, etching through apertures in the resist stencils and stripping of resist after etching.
Brief history of PCM:
Two developments within the space of forty years in photography laid the foundations for the photoresists we use today. In 1782 John Senebier of Geneva investigated the property of certain resins to become insoluble in turpentine after exposure to sunlight. Inspired by this, Joseph Nicephore Niepce resurrected an ancient Egyptian embalming technique that involved the use of what is now known as Syrian asphalt. This hardens after exposure to several hours of sunlight, into an acid resistant film. However, it took constant experimentation until this development was a success in 1822. The result was a resist that could be photo-polymerized in the exposed areas whereas the unexposed areas could be developed off in a solution of oil of lavender in turpentine. The age of photo etching had arrived. 
John Snellman may have been the first to...
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