The tops and bottoms of the Ceramic "Funnel", (the white section in the middle of the completed assembly, without the glass) were ground flat and to length with Diamond Wheels. The process was 100% manual and was fairly expensive.
A Numerical Control System was developed and implemented. The system used an acoustic sensor to detect the original contact between the diamond wheel and the part. Once contact was made, the speed and total amount removed were controlled numerically.
This project was completed in 1980, before computers and off the shelf controllers were widely available. The control system consisted of a series of custom circuit boards incorporating TTL IC's.
Because of the level of electrical noise, an important element of this project was the development of a Quadrature Encoder electrical noise filter.