RELIABILITY PAPER Acceptance X-bar chart considering the sample distribution of capability indices, Cp and Cpk A practical and economical approach

Autor(es)

Oprime, Pedro Carlos ^[1] ; Lizarelli, Fabiane Leticia ^[2] ; Pimenta, Marcio Lopes ^[3] ; Achcar, Jorge Alberto ^[4]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Carlos, Dept Prod Engn, Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos, Sao Carlos, SP - Brazil

^[3] Univ Fed Uberlandia, Management & Business Coll, Uberlandia, MG - Brazil

^[4] Univ Sao Paulo, Dept Social Med, Ribeirao Preto - Brazil

• Tipo de documento: Artigo Científico
• Fonte: INTERNATIONAL JOURNAL OF QUALITY & RELIABILITY MANAGEMENT; v. 36, n. 6, p. 875-894, 2019.
• Citações Web of Science: 0

Resumo

Purpose The traditional Shewhart control chart, the X-bar and R/S chart, cannot give support to decide when it is not economically feasible to stop the process in order to remove special causes. Therefore, the purpose of this paper is to propose a new control chart design - a modified acceptance control chart, which provides a supportive method for decision making in economic terms, especially when the process has high capability indices. Design/methodology/approach The authors made a modeling expectation average run length (ARL), which incorporates the probability density function of the sampling distribution of C-pk, to compare and analyze the efficiency of the proposed design. Findings This study suggested a new procedure to calculate the control limits (CL) of the X-bar chart, which allows economic decisions about the process to be made. By introducing a permissible average variation and defining three regions for statistical CL in the traditional X-bar control chart, a new design is proposed. Originality/value A framework is presented to help practitioners in the use of the proposed control chart. Two new parameters (C-p and C-pk) in addition to m and n were introduced in the expected ARL equation. The C-pk is a random variable and its probability function is known. Therefore, by using a preliminary sample of a process under control, the authors can test whether the process is capable or not. (AU)

• Processo FAPESP: 17/08861-6 - Gráficos de controle de aceitação considerando a significância prática utilizando-se de índices de capacidade do processo: proposta de um método preditivo e desenvolvimento de um software
• Beneficiário: Pedro Carlos Oprime
• Modalidade de apoio: Auxílio à Pesquisa - Regular