In the manufacturing world there are many different types of data collection. Some types involve production counts or machine up time, but this discussion is centered on data collection for establishing and monitoring product quality. Collecting data related to quality typically involves dimensional measurements or other product properties such as form, hardness, strength or surface finish. Quality data is collected and reported to establish capability such as first article inspections and, in some cases, to create archive records of measurements or tests made at the time of manufacture. Additionally, and most frequently, quality data is collected to maintain process stability with improved capability over time using statistical process control (SPC).
SPC involves the sampling of critical characteristics on a regular basis and plotting the variations on X-Bar & R charts providing advanced warnings that components may deviate from specification. Control limits and trend warnings on these control charts can be very useful if observed diligently by the user. Originally, in the paper and pencil era, these warnings required careful attention by the person plotting the points but today, with the use of software to plot control charts and monitor for warnings, the person performing the checks can easily be notified and act.