Back تحكم إحصائي بالعملية Arabic Control estadístic de processos Catalan Statistische Prozesslenkung German Statistical process control English Control estadístico de procesos Spanish Statistiline protsessi kontroll Estonian کنترل آماری فرایندها Persian Tilastollinen prosessinohjaus Finnish Maîtrise statistique des procédés French सांख्यिकीय प्रक्रम नियंत्रण Hindi
 | The English used in this article or section may not be easy for everybody to understand. (June 2014) |
Statistical process control (SPC) is the use of statistics to access the stability of a process and the quality of what that process creates. Proper use of SPC can result in faster and better production. SPC is very valuable to companies as a way to make producing their product less expensive and keep their customers happy.
A good example of SPC being used is a bottling plant, a type of factory where bottles are filled with liquid. The system that creates filled bottles is called a process. The weight of the liquid added to a bottle is very important for the bottling plant's cost control and customer satisfaction. If the target is to fill each bottle with 250 grams of liquid, it is still acceptable if some bottles are filled with another amount between 245 and 255 grams. SPC could be used to make sure that the process is being done well and that the weight of each bottle is in that range.
SPC relies on quantitative and graphic analysis of measurements to evaluate observed variation. If the attributes of interest (filled bottle weight in this example) vary within an acceptable range, a process is said to be in control, in statistical control, or stable. When unacceptable variation is noted (i.e., filled bottle weight is discovered to be below 245 grams or above 255 grams), actions are typically taken to determine and correct their cause. In the bottling plant example, suppose, too many bottles are filled with less than 245 grams. Checking the plant equipment reveals that one of ten filler valves is failing to work.
SPC was first used in the 1920s. It is used in manufacturing and in many other kinds of repeated activities.
Much of the power of SPC lies in the ability to examine a process using tools which give weight to objective analysis over subjective opinions and which allow the strength of each source to be determined numerically. Variations in the process, which might affect the quality of the end-product or service can be detected and corrected, thus reducing waste as well as the likelihood that problems will be passed on to the customer. With its emphasis on early detection and prevention of problems, SPC has a distinct advantage over other quality methods, such as inspection, which apply resources to detecting and correcting problems after they have occurred.
In addition to subtracting waste, SPC can lead to increased efficiency and less time required to produce the product or service from end-to-end. This is partially due to a reduced likelihood that the final product will have to be reworked, but it may also result from using SPC data to identify bottlenecks, wait times, and other sources of delays within the process.