A roadmap for improving the manifacture of automotive heat exchangers through value stream mapping

Abstract

Lean manufacturing is an optimum approach for the reduction and elimination of waste within an organization. The case study company is based in South Africa and produces heat exchangers through main processes or fractals, which include pre-assembly, core building, brazing and final assembly. A walk through the plant showed that there was a large amount of inventory awaiting final assembly and that the brazing furnace often waited for material from core building. This was an indication that there could be an imbalance between the three fractals in terms of cycle time. Thus, the aim of this study was to improve the manufacturing processes for heat exchangers at the automotive manufacturing company through the deployment of value stream mapping, subsequent line balancing and developing a roadmap for reduction of waste. The case study research strategy was adopted for the study since it provided an in-depth view of phenomena. The first objective was to outline the production flow for the manufacture of automotive heat exchanger parts. The method used was a walk through the plant and observations were made to gain an understanding of the production steps from logistics production planning to shipping of the finished goods, and subsequently to a mapping-out of the production process flow was undertaken. The results showed that there was a large amount of inventory awaiting final assembly and that the brazing furnace often waited for material from core building. It was concluded that there was need to conduct a detailed process analysis to identify sources of waste.

The second objective was to conduct value stream mapping for assessing the value- and non-value-adding activities in the manufacture of automotive heat exchangers components. A value stream map was developed through walking to Gemba and mapping out the production process, collecting data and pinpointing waste activities or areas to be improved. The kaizen flashes from the value stream map also revealed that operators were not fully utilizing the capacity of the bottleneck workstations. It was concluded that two instead of one planning points, and inefficiency at assembly were root causes of the high work-in-process level.

The third objective was to conduct a line balancing analysis for the three production fractals. The method used was a Pareto analysis for evaluating the products, analysing the product mix and line balancing analysis of the production line. The results revealed that the furnace was run on two shifts while the subsequent assembly and preceding core building were running on three shifts causing a work-in-process build-up, thereby resulting in line imbalance. It was concluded that it was imperative to change the scheduling approach, and adopt one that prioritised and spread the cores that had relatively short cycle times, and also reduce downtime, change-over time as well as additional time for scrap and defects, and a future-state balance chart revealed that the fractals imbalance had been reduced.

The fourth objective was to develop a roadmap for reduction of waste in the manufacture of car heat exchangers components. The method used was to develop proposals and assess the feasibility and cost implications of implementing each option.

Recommendations were made for continuous process improvement and a roadmap for reduction of waste was proposed. In order to improve the output of assembly, training for the operators was recommended since it would also enable the removal of the second planning point at assembly. Further research could also be conducted to develop an optimal scheduling algorithm for allocation of products to work centres to ensure high utilization of work centres and reduce work-in-process inventory.