Research pick: The end of the line for factory rejects - "Eliminating end-of-line rejections – a quality filter mapping approach"

A study in the International Journal of Services and Operations Management introduces a practical approach to quality control that could help reshape manufacturing and reduce the number of end-of-line rejects in production as well as the need to rework components and products. Such additional, and often costly, processes are undertaken in what can be referred to as the hidden factory.

P. Raghuram, Ashwin Srikanth, and P. Rithan Mandesh of the Department of Mechanical Engineering at Amrita School of Engineering in Coimbatore, India, have developed a Quality Filter Mapping (QFM), an approach to manufacturing methodology that addresses one of the big problems facing companies with high production volumes, stringent quality standards all hoping to improve their profit margins and their sustainability credentials.

Conventionally, quality control is a reactive process in manufacturing. Components are made, assemblies undertaken and at any stage where tolerances are not met, a component or assembly will be rejected. At this point, depending on the nature of the product, the reject may be fed to a parallel process to be reworked in some way so that it reaches the necessary standard. This approach is costly and wasteful.

QFM represents a shift towards a proactive quality control strategy, the research suggests. The team uses Pareto analysis in their new approach. The Pareto Principle, also known as the 80/20 rule, is named for Italian economist Vilfredo Pareto, He observed that approximately 80% of effects come from 20% of causes. In the context of quality control, Pareto analysis involves identifying the most significant factors contributing to a problem or outcome. By focusing efforts on addressing these critical factors, organizations can achieve substantial improvements in efficiency and effectiveness.

Through this analysis, major defects can be identified and their root causes traced using cause-and-effect diagrams. The underlying causes can then be mapped along the material flow in the assembly plant. This, the team suggests, seamlessly integrates quality control into the production process itself.

QFM offers significant cost savings by preventing the flow of defective components at an early stage in the manufacturing process rather than identifying them at the end of the line. This reduces the need for extensive end-of-line inspections and reworking in the hidden factory and so can reduce waste and improve efficiency throughout the whole manufacturing process. The team has taken an engine assembly line as a case study to demonstrate the effectiveness of the QFM approach.

QFM also promotes a culture of continual improvement and root cause analysis within organizations, contributing to heightened standards and customer satisfaction. The approach might also help companies address the broader challenges of evolving customer demand and fluctuating order volumes.

Raghuram, P., Srikanth, A. and Mandesh, P.R. (2024) ‘Eliminating end-of-line rejections – a quality filter mapping approach’, Int. J. Services and Operations Management, Vol. 47, No. 1, pp.123–140.