Statistical Process Control: the key to zero-defect manufacturing

Variability in industrial processes is behind many of the quality problems experienced by manufacturing companies. If not properly monitored, this phenomenon increases the probability of manufacturing defective units and, as a consequence, raises production costs. In this article, we explain how Mapex can help you implement Statistical Process Control (SPC), a set of techniques that are very useful for detecting and eliminating this type of deviation.

What is Statistical Process Control (SPC)?

Statistical Process Control (SPC) is the application of statistical tools to monitor the variation of a process or production method, detect deviations and anticipate possible quality problems. 

It is a proactive and preventive quality control strategy through which companies can guarantee the stability of their industrial processes and meet their customers’ specifications without having to inspect 100% of production.

Companies that implement the SPC take random samples of their production processes, which are then used to prepare control charts with an average value or central line, an upper and a lower control limit, calculated according to the set of samples obtained.

Thanks to this type of graphs, companies can quickly and visually see whether process variability is to be expected and caused by common causes (natural and constant over time) or whether, on the contrary, values have moved away from the average due to assignable causes (random and unpredictable) and corrective actions need to be implemented as soon as possible.

What tools does Mapex incorporate for Statistical Process Control?

Mapex incorporates different tools for the statistical control of automatic or mechanical processes. Our MES system can generate control charts to analyze both numerical quality control results collected through the MapexQM module and process variables obtained through the IIoT Platform.

Quality results can be taken with one or several samples. Depending on the number of samples, Mapex uses a specific type of control chart: I-MR for single samples; XBAR-R for sample subgroups of between 2 and 8 values, and XBAR-S for sample subgroups of more than 8 values. 

In all three cases, control limits are set, which determine whether the process remains stable or not. A series of conditions or alarms can also be applied to detect unnatural process deviations in real time or later.

Mapex’s SPC tools are very useful in office environments, as they show the value of the Pp and Ppk indices, focused on measuring the performance of the production process over the long term and on the basis of several manufacturing orders.

Operators can also access the Mapex SPC analysis graphs from their in-plant screens. In this case, the platform will show them the values of the capacity indexes Cp and Cpk, calculated from the results recorded for the production order in progress.

What are the benefits of applying Statistical Process Control?

Thanks to this statistical analysis tool, the Mapex platform takes a proactive role and is able to alert operators and factory managers when processes deviate from their natural variability.

Below, we highlight some of the benefits obtained with the implementation of SPC in industrial companies:

  • Improved productivity by making process behavior predictable.
  • Improved quality by being able to react before defects appear in production.
  • Compliance with specifications and increased ability to achieve higher quality standards.
  • Minimization of production costs by reducing rework and waste.
  • Increased operational efficiency.
  • Increased optimization of resources.
  • Improved analysis capacity within the company.
  • Boosting the deployment of the Six Sigma continuous improvement methodology.
  • Increase in the level of customer satisfaction and reduction of complaints.

If you are already applying Statistical Process Control in your company and want more information about the tools that MapexQM incorporates to enhance it, please contact our sales team and request a demonstration.

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