Error chain analysis—an effective method for tighter manufacturing process control

One of aims of manufacturing quality control is to ensure that products are made free from defects according to specifications without unnecessarily increasing time and cost of production. Over-control of a process can be as detrimental to a manufacturer as under-control. It is common in industry that operators use their personal know how and intuition to decide where to implement process verification, and where to tighten it when processes are not meeting specifications. This is partially because there is little scientific guidance that can assist operators in making a decision on levels of quality control of a process at varying stages. To remedy this, a new method for manufacturing quality control, namely Error Chain Analysis (ECA), is introduced and its application is illustrated in this article. ECA is capable of statistically analysing the quality of a multi-stage manufacturing process based on existing control measures, and it enables to indicate where added or tighter control may need to be effectively implemented. For testing its applicability, ECA was built into a user-friendly tool that was subsequently used to analyse data gathered from a large manufacturing company in the UK.