Page 21 - PCMI Journal July 2018

David Allen | Emeritus Professor | Cranfield University | UK Photochemical Machining: Where has it come from, and where is it going?
Electrolytic etching, probably using a solution of common salt as an electrolyte, was used as a production etching process over 60 years ago. Salfret (formerly of London, UK) was one of the first job-shops in the world to make commercial metal parts by etching.
Surprisingly, this company made parts by electrolytic etching rather than spray or immersion etching. Figure 5 shows an historical item from my collection of PCM artefacts.
The 8-page brochure is back-stamped ‘Received 14 December 1957’ and attached samples included part of a 0.15mm thick stainless steel microfilter containing rows of 0.3mm diameter holes.
Figure 4. Siviter Smith personnel in the early 1960s. (Photograph courtesy of Precision Micro) Years of rapid expansion
PCM grew strongly from its bases in USA and Europe and many other extant PCM companies have a long history. For example:
• Veco, located in The Netherlands, acquired the UK company Tecan Components Ltd. in 2009. Tecan had previously incorporated Checkmate Devices Ltd., a UK company that pioneered PCM in the 1950s.
• Tech-Etch, USA, began as a small engraving company in 1964
Issue 131 July 2018 PCMI Journal 20