Robotic and manual hot die forging of connecting rods – Efficiency, forging quality and automation potential

Abstract

This study addresses the evaluation of efficiency and the feasibility of automating the hot forging process of connecting rods through a comparative analysis of manual and robotic variants. Despite significant technological advancements and developments in industry, the implementation of robotics in hot forging processes continues to face substantial challenges due to extreme working conditions. To verify the automation potential, a case study was conducted in which both process variants were performed on the same forging station — a 16 kJ drop hammer equipped with the same 150 kW induction heater. In the robotic setup, two FANUC robots were employed. Experiments were carried out under identical process conditions and involved the production of connecting rod forgings dedicated to precision internal combustion engines, forged in a three-step sequence from 16MnCr5 steel. Approximately 20,000 forgings were produced in each variant during the hot die forging process on the hammer. The conducted investigations included numerical modelling, process performance measurements, dimensional and shape analysis of the forgings, as well as microstructural studies. The research identified that a critical challenge lies in the development of optimal die cavity geometries that accommodate robotic grippers and the synchronization of the entire process for automation purposes. The results showed that, although the cycle time was longer in the robotic process (16 s versus 12 s in the manual process), it exhibited greater stability and repeatability, higher forging quality, and a more uniform microstructure. Operational testing confirmed that the robotic forging process provides more stable and repeatable working conditions compared to the manual process. Additionally, a 25 % increase in tool service life was observed, translating into tangible economic benefits. Introduced changes also shifts the role of operators to process supervisors, thereby reducing their physical workload. Based on the comprehensive results, it can be concluded that despite the challenges, the robotization of the hot die forging process is feasible and advantageous; however, it requires support through FE simulations and a tailored approach for each specific forging process.