Open Access Open Access  Restricted Access Subscription Access

Process Capability Assessment with Trended Processes: A Case Study

Yerriswamy Wooluru, D. R. Swamy, P. Nagesh

Abstract


Process capability indices play an important role in process control as they assist in deciding the suitability of a manufacturing process to meet the desired quality requirements. In order to achieve high quality with optimum cost, shifting from product control to process control is essential in manufacturing organizations. Process capability study is a prerequisite before moving in to full scale production. The successful application of traditional process capability indices requires the process to be stable and normally distributed, but it is not the case for trended processes. Interpretation of process capability for trended process is a critical issue. In this paper, the traditional process capability indices were tested for the trended process. Two different sources of process variation, one from the process trend, the other from random variation of individual observation were estimated and used to develop new process capability indices for trended process. The new indices that were developed for trended process showed that the capability of trended processes could be improved through periodic replacement of the tools to the maximum achievable value (1.33). This paper presents the step by step procedure to determine the tool adjustment frequency to meet the pre specified requirements on the capability index when the quality characteristic of interest is represented by a linear trend. A case study was conducted to evaluate the performance of the traditional and proposed indices for trended process. Results of the process capability indices for trended process were found satisfactory.

Keywords


Process capability, Trended process, process capability indices, process variation, Univariate process capability.

Full Text:

PDF


Disclaimer/Regarding indexing issue:

We have provided the online access of all issues and papers to the indexing agencies (as given on journal web site). It’s depend on indexing agencies when, how and what manner they can index or not. Hence, we like to inform that on the basis of earlier indexing, we can’t predict the today or future indexing policy of third party (i.e. indexing agencies) as they have right to discontinue any journal at any time without prior information to the journal. So, please neither sends any question nor expects any answer from us on the behalf of third party i.e. indexing agencies.Hence, we will not issue any certificate or letter for indexing issue. Our role is just to provide the online access to them. So we do properly this and one can visit indexing agencies website to get the authentic information. Also: DOI is paid service which provided by a third party. We never mentioned that we go for this for our any journal. However, journal have no objection if author go directly for this paid DOI service.