CRT Bulb Assembly Line
To the left is a completed CRT "Bulb" assembly. It consisted of a glass face-plate, with reticule, a ceramic funnel and a neck ring, (shown at the top of the picture). The entire assembly was fused together with glass "frit" through a high temperature oven, (about 450 Deg C). When these bulbs were assembled they were capable of maintaining a high vacuum, (about 8 Torr) over the life of the CRT.
The first step in the assembly process was to unpack the individual components. Because the operation was in a clean room environment, custom clean room compatible conveyor systems, including an elevator, and racks were implemented in the level below.
Special SS racks, which traveled between the staging area and the Clean Room assembly area were designed for easy cleaning .
The first step was to silk screen a reticule that would eventually be on the inside of the CRT. Having the reticule on the inside of the face-plate eliminated parallax for the end user.
The glass frit was applied, and would later attach the faceplate, funnels and neck glass together. The assembly was placed into a high temperature rack, (shown to the right) to maintain alignment through the high temperature fritting process.
Material handling was a major requirement of this production line. The fixtures were automatically loaded into and out of the fritting oven.
A major challenge was to establish and maintain the temperature profile of the glass/ceramic parts through heating processes.
For Glass-Ceramic assemblies the maximum allowable temperature rise was 5 degrees C per minute. Previous Oven Systems required extensive amounts of time to stabilize their profiles before products could be processed. The result of these extremely long warm up times was that it was not uncommon to keep the ovens at temperature, 24-7.
The challenge of minimizing the temperature stabilization time was presented to oven suppliers, which produced very stable profiles by increasing the number of controlled temperature zones. The typical oven for these processes usually only had 2 or 3 control zones. This oven incorporated 7 temperature control zones. Stable temperature profiles could be established in less than 30 minutes.
The cost of this production line was slightly less than $1M (in the early 1980's) and reliably produced 90 bulbs per hour with extremely high yields and greatly reduced labor.