Application of root cause analysis in improvement of product quality and productivity

Abstract

Root-cause identification for quality and productivity related problems are key issues for manufacturing processes. It has been a very challenging engineering problem particularly in a multistage manufacturing, where maximum number of processes and activities are performed. However, it may also be implemented with ease in each and every individual set up and activities in any manufacturing process. In this paper, root-cause identification methodology has been adopted to eliminate the dimensional defects in cutting operation in CNC oxy flame cutting machine and a rejection has been reduced from 11.87% to 1.92% on an average. A detailed experimental study has illustrated the effectiveness of the proposed methodology.Keywords: root cause analysis, cause and effect diagram, interrelationship diagram and current reality tree that leads to the discovery of faults or root cause. An RCA investigation traces the cause and effect trail from the end failure back to the root cause. It is much like a detective solving a crime.To meet up the high changing market demands along with high quality at comparable prices, one shall have to identify quickly the root causes of quality related problems by reviewing an event, with the goals of determining what has happened, why it has happened and what can be done to reduce the likelihood of recurrence. Objective and outline of the studyThere are varieties of problems related to product quality and productivity in industries due to varying degrees of abnormality and inefficiency which ultimately causes rejection. Root-cause identification for quality-related problems is a key and necessary step in the operations of manufacturing processes, especially in highthroughput automated processes. This is predominantly true for the multistage manufacturing processes, which is defined as a process that produces the products under multiple setups. The quality information flow of the product in a multistage manufacturing system and the interaction between the process faults and the product quality characteristics are very complicated. In multistage process, the identification of process root cause is also not simple. It has been observed that the implementation of Root Cause Analysis in a particular single individual setup has simplified the problem.A case study was done for an industry which was in doldrums condition. The abrupt shutdowns and breakdowns (5.19% of annual sales), frequent customer complaints (367pa), line balancing delay (27%), material scarcity or unavailability of matching material (58 days pa), rejection (3.03% of sales) and various other key success factors were not up to the mark. Therefore, the Root Cause Analysis was undertaken to improve the plant situation. But, the study was confined to the CNC Oxy Flame Cutting Machine. In this paper, the identification of the problem has been simplified taking into consideration a particular stage of manufacturing. It has been observed that RCA can also be implemented in each and every individual set up of manufacturing to improve product...

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