Situation In the machining area of a manufacturing plant, a number of machine centers are set up to machine a wide variety of parts. These parts are later assembled into finished products. Since there are many more parts than there are machines, each machine must be able to work on several different parts. This situation results in frequent setups and short runs. There is a renewed effort in the company to use statistical process control and process behavior charts with the machine centers. Some of the people who used SPC once before had a bad experience because there were so many charts to keep for all of the different parts. This time everyone is determined to figure out how to use SPC without making it so tedious and time consuming. Available Data Machine KLX4337 is a very versatile machine. It is easy to program and can machine a large number of parts. Every hour during a run, operators select three parts to measure and record critical dimensions. During one 24-hour period, 4 different parts were made on machine KLX4337. These parts are similar, but they have different nominal values for some of the critical dimensions. Data values and nominal values for each of these parts are summarized in the table, “Length A.” The tolerance for length A is ± .10 for the different parts. Questions 1. What is the difference between the process and the product for the KLX4337? 2. How can SPC be used with these data to study the process? 3. Is this process capable of producing parts that fit within ± 0.10 of the nominal value?
Published by QualityMagazine. View All Articles.