SPC Statistical Process Control

SPC by its acronym Statistical Process Control, are control charts, which allow objective criteria to be used to distinguish background variations of important events. Almost all its power is in the ability to monitor the center of the process and its variation. This tool is also considered as the APQP, PPAP, FMEA and MSA part of the Core Tools of the automotive sector and is a requirement of the IATF 16949 technical specification.

Fundamental Concepts of SPC

The management philosophy for total quality is based on the constant improvement of the process, with the purpose of preventing the production of defective products or services. Therefore, a fundamental element in this philosophy is the control of the process. This control is indispensable, because in any process the phenomenon of variability is latent.


The factors that cause this phenomenon are among others:

  • The machinery or tool used, which does not always work in the same way.
  • Raw material, which does not have the same characteristics at all times.
  • The human factor, whose work depends on many external and internal circumstances.

Controlling the process is not about suppressing variability but about reducing it.

SPC in the Automotive Industry

The SPC has a wide application in the automotive industry, focused on the following aspects:

  • Obtain and process data that allow establishing the behavior of the processes for their control.
  • Customer satisfaction as the main business goal.
  • The organization must comply with its commitment to improvement
  • Basic statistical methods can be used to make the improvement effort effective.
  • Prevent rather than correct.
  • Improve the performance of processes.

Basic Points of the SPC Manual

  1. The collection of data and the use of statistical methods to interpret them is not ends in themselves. The intention is to understand the process as a basis of the actions to be taken.
  2. The measurement systems are critical for the proper analysis of the data, and should be well understood before the data collection of the process. When such systems lack statistical control or their variation consumes a substantial portion of the total variation in the process data, inappropriate decisions can be made.
  3. The basic concepts of the study of variation and the use of statistical techniques to improve their performance can be applied to any area. However, the material in the SPC Manual is focused on applications in manufacturing processes.
  4. The application of statistical techniques to the output of the process (parts) should be only the initial step. The process is what generates this output, so you have to focus efforts to know their performance and improve it.
  5. The application of the SPC with examples is illustrated in the manual. It is recommended that participants apply it in real cases of their organization.
  6. The SPC manual is a first step towards the use of statistical methods and does not replace the users’ need to increase their knowledge of statistical methods and their theory. Readers should be encouraged to aspire to a formal statistical education. In those fields in which the coverage of this manual is exceeded, the reader should seek the person with the required knowledge and consult it to learn the appropriate technique.

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