How Statistical Process Controls are Applied in Quality Control Management
Statistical Process Controls, also called SPC, are procedures aimed at enabling analysts, inspectors, auditors, and managers to monitor process behaviour. Training in SPC is essential for any inspector, associate, consultant, or manager involved in quality control and quality control management. Training in statistical process control includes aspects regarding the control charting and the various procedures, in addition to the application of these in the enterprise.
What is SPC?
It is a quality control approach that relies on the utilisation of statistical methods for monitoring and controlling processes with the aim of ensuring the processes are efficient and operate effectively. If the process operates at the maximum potential, it ensures optimal conformance of a product, with the lowest level of waste. The statistical process control is relevant to any type of process where it is important that a product meets specific minimum quality standards and where these are measurable.
SPC entails usage of statistical tools such as charts for control and experiment designs, in addition to ongoing improvement. It is applied in the following way:
- The process is established.
- The process is used for production.
The period of analysis must be determined according to change in manpower, equipment (machines), the material or the method, and the parts’ wear rate (parts used in the manufacturing process). SPC is, in essence, a quality control method that holds the benefit of allowing for early identification of problems or potential problems, and their subsequent prevention, as opposed to addressing problems after they have occurred. Inspection is also a quality control method, but it detects problems that have already occurred. In this regard, SPC enables prevention of problems and thus brings about savings, minimisation of risks, and ongoing improvement of quality.
By using the SPC quality control method, it is possible to minimise waste and to reduce the time needed to manufacture a product. Another benefit is that, because of early detection of problems or potential problems and correction of these, the chances of a defective product leaving the line is minimised. In this way, it also reduces the likelihood of requiring the remanufacture of a product. SPC is thus beneficial for reducing waste in the production process. If done correctly, it can reduce or eliminate the need for post-production inspection. However, SPC effectiveness is dependent upon the knowledge, skill and efficiency of the people applying the method. As such, SPC training is essential for the quality control manager, auditor, or inspector to ensure that the person has the necessary skills to effectively apply the quality control method. Before the method of quality control is applied, it must first be determined whether SPC can be applied for the specific process.
Origin of Statistical Process Controls
The quality control method was first introduced by W.A. Shewhart, who was credited for development of the control chart. W.E. Johnson was credited for developing the exchangeability concept, which is similar to statistical control. Shewhart, together with Colonel L.E. Simon, developed the usage of control charts for quality control in ammunition manufacturing at the military Picatinny Arsenal in the 1930s.
Expansion of the Application of SPC
Although mainly applied to manufacturing processes until the late ‘80s, SPCs relevance to software engineering processes was shown by the Software Engineering Institute. However, it is best applied in repetitive processes rather than in systems engineering development where the processes are not repetitive and are skill and knowledge focussed.
Relevance to the Manufacturing Sector
SPC works well in the manufacturing sector because quality in the process means conformance to a minimum specification. The conventional method of quality control in manufacturing is to inspect products for defects after completion, and conformance with specifications. A sample of products can be obtained and assessed to determine how well the items meet the specifications for design. With SPC, on the other hand, statistical tools are used for the observation of the production process performance. It detects any important variations before a non-conforming article is produced. The variations can be at any point in the production chain.
Two types of variations can be distinguished. The first is called the common cause, which is any source of variation that affects the process on a consistent basis and leads to repeatable distribution over a period. The second is called the special cause, which is any assignable source of variation that causes the variation, affecting a specific part of the process output. This type of cause is not predictable and does not give a repeatable outcome.
SPC becomes relevant where major variation sources can be identified and where it is possible to apply resources to change the outcomes, such as removing the sources of variation. Once the sources are removed, the process is stabilised and variations are then within the acceptable variation limit. SPC entails getting a full understanding of the processes involved and what the specification limits are, as well as the elimination of special sources of variation to return the process back to stable status. The third important aspect of the statistical method is to monitor the production process using control charts to identify any important variation changes.
Training in Statistical Process Controls
Managers, supervisors, and professionals involved in the development of the enterprise Quality Management System, internal auditors, and lead auditors will benefit from attending the three-day WWISE Statistical Process Controls Training. It is a Level 2 course in Quality Control and forms part of training for a Certificate in Quality Control. Besides SPC training at this level, we offer the Introduction to Quality Control, Introduction to Statistical Techniques and Problem Solving, and Decision-Making Control courses.
On Level 1 we offer Quality Awareness in Manufacturing, Quality Awareness in Services, and Motivational Customer-Focussed Training on the Importance of Quality where attendees receive certificates for attendance. We also offer the Certificate in Quality Assurance and the Certificate in Quality Management on the more advance levels. Download our training brochure at the training category or call us for more information on Statistical Process Controls training and entry requirements of the course.