Control charts for low-volume manufacturing

In industry, low-volume manufacturing amounts to more than 50% of all manufacturing, so quality control and control charts for low-volume manufacturing are very important. The control chart is a statistical method. It works best for long and continuous runs of the same product over a particular process. In low-volume manufacturing, many different parts are run on the equipment and the quantity of each part is low. This brings difficulties in the application of control charts. In this paper, we introduce three methods to solve this difficulty. These methods allow operators to plot multiple part numbers on the same chart by the use of special transformations that transform data from different part numbers to the same distribution. These three methods are the universal chart method, the relative tolerance method and the fixed sample size method.