On-line process control of the number of non-conformities in the inspected item

• Autor(a) principal: Vasconcelos, Renata Mendonça Rodrigues
• Data de Publicação: 2012
• Outros Autores: Medeiros, Pledson Guedes de, Ho, Linda Lee
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/jspui/handle/123456789/26058; http://dx.doi.org/10.4322/bjopm.2013.005
• topic: On-line process control; Rate of non-conformities; Markov chain; Economic model; Poisson distribution

Generally, production systems as automatic welding process, production of ceramic products, making clothes use automatic control and to evaluate the quality of their production processes, they employ on-line process control. The control system consists of a periodic inspection of one item after every m produced items. The number of non-conformities is monitored in the inspected item and if it exceeds the control limit, then it is decided that the process is out-of-control and the process is stopped for adjustment, otherwise the production continues. The process starts leading the system to operate out of control. The process remains in these conditions until the change is detected and the process adjusted. After adjustment, the process returns to operate in-control. The aim of this paper is to present an economic approach to monitor the rate of non-conformities in a production by on-line process control. To design such type of process, an average cost per item produced is achieved through the properties of an ergodic Markov chain and the two required parameters: the inspection interval and the upper control limit are obtained by minimizing the average cost per produced item. A numerical example illustrates the proposal. cost per item: the probability of a shift in the parameter of Poisson distribution; cost to send limit and the cost of adjustment.