This control handle was a very elaborate design. The customer wanted a total of 17 contacts operable for various functions. One rocker switch set was to be double acting with an initial momentary position for jogging, and a second requiring a deeper motion that would be electronically maintained.
Strong tactile response of the switch actuators was desired. Unlighted prototypes used dome switches, the final design was to use a rubber keypad that would provide a tactile response while still passing light to the graphics. A supply of field prototypes were needed for testing the various ideas. The shape was dictated by touch models which were scanned and the resulting cloud of points used for 3D CAD modeling. The ergonomic shape was the result of careful study and could not be modified. The switches were arrayed on the handle to map well to the actual functions of the machine. A left/right motion on a switch would correspond to a left/right motion of the equipment. The handle had to have an adjustable position - for which a ball joint and elastomeric clamp were designed. The outer surface, except where the switches mounted, was to be a soft touch material molded over all. Santoprene was selected as the soft touch material. An indicator lamp was required. The operator facing switches had to be lit from behind with white light so that colored graphics would be illuminated. A number of unique ideas were tried out including molded and plated 3D circuitry with a clear second shot of clear poly-sulphone to pass the lamp light. At this time in the 1990's only incandescent lamps could make white light. This turned out to be a bad idea because the handle would get hot. Making cast prototypes was very tricky. I had two castings made of the touch model from sIlicon rubber molds. One casting provided a positive for making a mold of the outer elastomeric coating. I carved away the outer 1/8" of the second casting and hollowed an inner volume for switches, lamps and ball joint, to form the positive model for casting a mold of the inner part. After casting the inner part, it was then inserted in to the mold for the outer part and the elastomeric cover formed. There was a third casting mold use to make switch face also made from the first casting. |