EVALUATION OF PROCESS CAPABILITY OF ASSEMBLY PRODUCTION LINE USING STATISTICAL PROCESS CONTROL TECHNIQUES
Keywords:SPC, control charts, process capability, assembly production Line
This paper deals with application and use of statistical techniques to evaluate the process capability of assembly production lines. The process capability is a numerical measure of process parts variation in terms of capability indices. To understand the concept of process capability a case study is carried out for parallel assembly production line of two process parts. Quality charactertics of these two parts are the gap variation that causes the fitment (loose fit or interference fit) problem in parts during assembly. This fitment problem is analyzed with cause and effect diagram and a necessary corrective measure are recommended to remove the root cause. Control charts technique has been used to monitoring the gap variation during assembly of process parts and dimensions of individual process parts are also monitored. Process capability and defective rate for individual process parts as well as for assembled parts are determined. The results show that parts of process one is under control having capability value 1.33 with defective rate 0.006% but another process parts are out of control that producing defective parts with capability value 0.85 with defective rate 1.08. The overall process capability for assembly production line are 0.92 with defective rate 0.52. Therefore from the results analysis, it is concluded that rejected parts from process one can be assembled with rejected part of another process and creates one accepted assembled one.
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