Process control is in its basic form the art of guiding the process to achieve the desired result. Process control is not always about perfection, the key is to understand both what is good enough, which steps and parameters are most important or even critical for the result. This understanding of the process is also important when there is a need to change the process, to produce a new product, add an extra production line or because a raw material or process chemical cannot be sourced anymore. In many organisations, this crucial information may never have been documented because it was seen as obvious when the factory was built or the knowledge has grown gradually and been maintained as skill and experience with long-term staff.
Process control can be many things, in its simplest form it can be that you attempt to repeat the steps in exactly the same way every time, followed by a reactive evaluation of product quality, i.e. does the product work, does the shaft dimensions match the specification, is the viscosity of the oil correct etc. However at the point of a finished product, failure to meet specifications can be costly if a whole production run has to be scrapped, for example.
Proactive process control starts by understanding how each step and controllable parameters in the process affects the following steps, and by consequence the quality of the final product. What characterises a normal variation in the process and what constitutes an anomaly or abnormal deviation. The purpose being to guide the process towards a more robust and efficient process and in some cases either detect deviations early before a whole production run is ruined or optimally be able to correct the deviation in subsequent process steps. It also allows for more controlled scaling of processes to increase production, add production lines or building more factories