2. Stainless Steel Case-backs
The distribution of the electronics around the wrist relies entirely on the integrity of the stainless steel case backs, both mechanically and electrically. This put the component on the critical path and required a fully functional prototype to be produced very rapidly for testing before proving the concept.
I studied at the Royal College of Art, I had made rudimentary
experiments with makeshift tooling for metal forming, including using
rubber under pressure to make organic forms in sheet metal. This
experimentation had continued during my time with PDD and I was
therefore able to imagine sheet metal forming by using simple tools
machined from acrylic blocks.
These plastic tools were used to prototype press formed brass components. These were then complete by hand folding, filing and drilling. Assembled was achieved using a reflow soldering process with miniature brass piano hinges in a jig to ensure accurate alignment during the application of heat, solder flow and cooling down, quite a tricky process to control and it had to be right first time! This one off prototype allowed us to test the watch mechanically and electrically. The tests proved that the design and the assembly worked fine and gave us 100% confidence before spending £ 38,000 on production tooling.
This was another example of rapid prototyping wit analogue processes. The acrylic tools were quick and easy to machine and worked very well. The hand shaping and forming was also quick and although the gas reflow soldering took a lot of setting up it too was accomplished rapidly. The whole process took only about 3-4 days, in between other tasks.
The manufacturing of this component assembly was contracted to Keyswitch-Varley in South East London and consisted of 3 pressed case-backs and two precision turned hinge pins (Made in Switzerland on auto lathes). The reputation of Keyswitch Varley for precision press work was second to none, based on their long standing manufacturing of the internal metal parts in radio tubes.
The multiple progression tooling at Keyswitch-Varley was running at 600 hits per minute and it was a great feeling to stand next to the press and seeing my components dropping into a box at this speed! I remember thinking that the design and dimensions had better be right! I need not have worried everything was fine, no adjustments were necessary.