Combining Capability Indices and Control Charts in the Process and Analytical Method Control Strategy

  1. Llabrés, Matías 1
  2. Oliva, Alexis 1
  1. 1 Universidad de La Laguna

    Universidad de La Laguna

    San Cristobal de La Laguna, España

    GRID grid.10041.34

Quality Control in Intelligent Manufacturing [Working Title]

Year of publication: 2020

Type: Book chapter

Export: RIS
DOI: 10.5772/intechopen.91354 GOOGLE SCHOLAR lock_openOpen access editor


Different control charts in combination with the process capability indices,Cp, Cpm and Cpk, as part of the control strategy, were evaluated, since both arekey elements in determining whether the method or process is reliable for itspurpose. All these aspects were analyzed using real data from unitary processesand analytical methods. The traditional x-chart and moving range chartconfirmed both analytical method and process are in control and stable andtherefore, the process capability indices can be computed. We applied differentcriteria to establish the specification limits (i.e., analyst/customer requirements)for fixed method or process performance (i.e., process or method requirements).The unitary process does not satisfy the minimum capability requirements forCp and Cpk indices when the specification limit and control limits are equal inbreath. Therefore, the process needs to be revised; especially, a greater control inthe process variation is necessary. For the analytical method, the Cpm and Cpkindices were computed. The obtained results were similar in both cases. Forexample, if the specification limits are set at 3% of the target value, the methodis considered “satisfactory” (1.22<Cpm<1.50) and no further stringent precisioncontrol is required.