Managing drifting processes

There are situations where process averages have been found to drift in manufacturing processes. The process average either increases or decreases continuously over time. Often there is no option, but allow this drift. However, the process has to be reset frequently to trade-off between oversize / overworked and undersize / under-worked items. The paper recommends an optimisation technique which trades-off between oversize and undersize contributions and set up cost. It also recommends a procedure for estimating the process average, process capability and control charts for drifting processes.