We frequently entertain questions about MSA and specifically, gage R&R. Below are two questions we recently received:
Question #1: “What are the requirements for the parts chosen in a study? Do the parts have to have the same specification?”
Answer: The parts selected should be representative of the process variation that is producing them. This implies that selecting 10 consecutive pieces (parts) is not as good as using 10 parts obtained throughout the day or week. Part of what you are trying to do with an R&R study is determine whether your measurement system is capable of distinguishing parts made on the same process to the same specification. In summary, you want to select the parts in a way that represents the minimum sized part, the maximum sized part and those in between. If the selected parts have different specifications, they are different by design, not by random variation.
Question #2: “Results can be calculated in several ways: using study parameters, specifications and others. Which is most acceptable for gage R&R?”
Answer: The industry trend is to use study/process parameters, however, how you calculate the results of a gage R&R study depends on the purpose for doing the study. Before the study begins, you should decide what the primary purpose for conducting the study is. If you are trying to control your process, you need to be able to detect changes in the process. To do this, you should use study parameters or process parameters. If your focus is being able to compare a part to specifications, then you should use the specification method. Using the specification method suggests that you are trying to prove that your measurement system can distinguish between good and bad parts.
If you have any other questions or concerns about MSA or gage R&R, please contact us at firstname.lastname@example.org or by phone at 800-777-5060 or just post them below.