Trailer based rail monitoring in overhead hoist transport systems

In 300 mm semiconductor factories, overhead transport (OHT) systems used for safe and fast transportation of wafers. These systems consist of a rail network and OHT vehicles. The components of the rail system are subject to high stress through vehicle motion. Individual fault-related failures in the rail network can cause considerable damage and loss of production. Therefore, it is necessary to reduce the fault probability to a minimum. For this reason, extensive preventive maintenance should be used with such a rail system. In preparation to change to a condition-based maintenance strategy, we developed a measuring platform for rail condition monitoring. This article describes the design of this platform and presents a first example of 3-D measurement data acquisition for spatial alignments checks.