Editing Statistical process control (section)

{{Short description|Method of quality control}}
{{redirect|SQc|other uses|SQC (disambiguation)}}
{{More citations needed section|date=March 2022}}
[[File:Example Control Chart - DSE Si Etch.jpg|alt=plot showing silicon etch rate versus date, over months, with ±5% and mean values shown.|thumb|297x297px|Simple example of a process control chart, tracking the etch (removal) rate of Silicon in an [[Inductively coupled plasma|ICP]] [[Plasma etching|Plasma Etcher]] at a [[microelectronics]] [[Wafer fabrication|waferfab]].<ref>{{Cite web |last1=Dutra |first1=Noah |last2=John |first2=Demis |title=Process Group - Process Control Data - UCSB Nanofab Wiki |url=https://wiki.nanofab.ucsb.edu/wiki/Process_Group_-_Process_Control_Data |access-date=2024-11-08 |website=UCSB NanoFab Wiki}}</ref> Time-series data shows the mean value and ±5% bars. A more sophisticated SPC chart may include "control limit" & "spec limit" % lines to indicate whether/what action should be taken.]]
'''Statistical process control''' ('''SPC''') or '''statistical quality control''' ('''SQC''') is the application of [[statistics|statistical methods]] to monitor and control the quality of a production process. This helps to ensure that the process operates efficiently, producing more specification-conforming products with less waste scrap. SPC can be applied to any process where the "conforming product" (product meeting specifications) output can be measured. Key tools used in SPC include [[run chart]]s, [[control chart]]s, a focus on [[Continuous Improvement Process|continuous improvement]], and [[Design of experiments|the design of experiments]]. An example of a process where SPC is applied is manufacturing lines.

SPC must be practiced in two phases: the first phase is the initial establishment of the process, and the second phase is the regular production use of the process. In the second phase, a decision of the period to be examined must be made, depending upon the change in 5M&E conditions (Man, Machine, Material, Method, Movement, Environment) and wear rate of parts used in the manufacturing process (machine parts, jigs, and fixtures).

An advantage of SPC over other methods of quality control, such as "[[inspection]]," is that it emphasizes early detection and prevention of problems, rather than the correction of problems after they have occurred.

In addition to reducing waste, SPC can lead to a reduction in the time required to produce the product. SPC makes it less likely the finished product will need to be reworked or scrapped.