CNC Machining a wearable machine

Zenith is an original, custom-machined watch case designed around a Swiss-made, self-winding mechanical movement. The goal was to create an elegant watch that was as much a piece of jewelry as it was a timepiece. The project included in equal measure open-ended, creative design problems and technical constraints of fixturing, machining and assembly.

The design concept was developed around the incredible beauty visible in the self-winding mechanism. The inherent technical aesthetic of the 700 year-old craft of watchmaking are so clearly visible that the choice to display the mechanism was an easy one. The metaphors of making and time keeping are visible in the final design, where the brass ring and aluminum pin resemble the sun and the moon, while the 12 sides of the case resemble a wrench. Yet, these elements also serve a practical purpose. The facets of the case mark the hours, while the pin at high noon was used as a crucial fixturing reference point for 3+2 axis machining on a custom fixture and for registering the movement within the watch case.

From a technical perspective, there were some significant challenges to consider. The first was to design a case that would tightly hold the movement without inhibiting the movement of the watch hands or winding rotor. This was accomplished with a small aluminum ring with a series of flanges to accommodate key points. Other challenges included designing threads for the thin walls of the watch housing, creating a key to allow the caseback to be screwed in and out, and optimizing the thickness of the brass ring for clearance of the watch hands.

Finally, there were several critical factors to consider in the process of CNC machining the various parts. The main concerns were around the order of operations machining and workholding for several part-flips, a press-fit, and 3+2 axis rotations during milling. The solution involved creating a custom fixture that allowed for finishing of the hands from the top and bottom, and to mill the hole for the winding rotor at 4 o’clock.