Patent ID: 7209846

Claim:
A product quality control method for controlling the quality of a product manufactured through a plurality of manufacturing processes and including means for collecting manufacturing history data and quality inspection means for inspecting a quality of an end product in a production line, the method comprising the steps of: (a) collecting quality inspection information for the end product and manufacturing history data for each manufacturing process performed on the product, and calculating a statistical correlation magnitude between the quality inspection information and the manufacturing history data; (b) generating a correlation network model having edges connecting the quality inspection process and all of the manufacturing processes to each other, wherein a graph coupling strength for each edge is represented by the calculated correlation magnitude; (c) leaving the edges connecting product quality variation and candidates of processes causing the product quality variation in the correlation network model by using said correlation magnitude, and deleting other edges from the correlation network model; (d) calculating mutual correlation magnitudes between the manufacturing history data of two different manufacturing processes in every manufacturing process; (e) adding edges having graph coupling strengths corresponding to the calculated mutual correlation magnitudes to said mutual correlation network model to generate a causal network model; (f) leaving the edges connecting manufacturing processes having inter-process variation propagation in the causal network model in the form of an undirected graph, and deleting other edges from the causal network model, based on the graph coupling strength; (g) converting the undirected graph to a directed graph in the causal network model obtained at the step (f) based on manufacturing sequence information management apparatus which has been previously provided; and (h) extracting a process causing the product quality variation on the end product by tracing the directed graph of the causal network model from information regarding product quality of said end product, and displaying information corresponding to the extracted process on an output device.