|On the Lincoln Navigator, the running boards extend outwards when the car is stationary and stored inboard for traveling. The boards are moved by a rack and pinion gear inside a housing mounted immediately behind the front wheels. The gear assembly housing cover is fitted to the end of the gear motor housing. The rotary movement of the actuator is governed by sensors. These sensors mount in thru-holes and require a precise geometric placement. The challenge for Protoplast was the high tolerance demanded in the final specifications, plus or minus .002″ on the major diameter and the inside mounting boss and the geometric location of the sensor holes in relation to the datum was critical. To meet this challenge Protoplast manufactured an asymmetrical die so that the different thicknesses of the cover on both sides would shrink to the correct finished dimension on cooling. The inside view in the picture cell shows the precise nature of the finished part: major diameter, the boss diameter and the precise geometric location of the sensor holes.