The evaluation of process capability for a machining center

Abstract

The machining center methodology is widely applied to production systems within the fast-developing processing industry. The automated machining center can simultaneously perform certain processes, such as milling, drilling, boring, and reaming, on the same machine at the same time, and manufactures limited quantities of multiple-type products. These products usually have numerically important quality characteristics with high accuracy. However, a machining center is unable to measure process capability on its own. Thus, we reflect the process capability of a machining center by measuring the quality characteristics of its processing products. In this paper, we propose the three integrated process capability indices (PCIs) C ^mc_p , C ^mc_a , and C ^mc_pm to evaluate the integrated process precision, accuracy, and actual capability respectively. Furthermore, we develop a process capability monitoring figure (PCMF), which not only displays the status of the process precision and accuracy by the color management method [1], but it also forecasts the integrated process capability of the next productive time (batch) through the analysis of time series. Using the PCMF, engineers will be assisted with tasks such as monitoring the process quality, deciding the period of the borer’s replacement, and designing the process parameters.