A forging method for reducing process steps in the forming of automotive fasteners

The automotive component manufacturing sector is experiencing fierce competitions. To enable improvements in production efficiency, the authors introduced single step injection forging as an alternative to conventional multisteps forging processes for manufacturing automobile fasteners, being enabled by a dedicated tool-design to achieve combined material-flows and hence, a complex component-form. To assist in this, a feasibility study was conducted, including comparisons of conventional multisteps forging with injection forging, through FE simulations, experimental validation of the injection forging process, as well as detailed examinations of the quality of the parts formed. The simulations were focused mainly on the forming of a wheel bolt. Axi-symmetric models were developed to analyse forging force and energy requirements, resulting forming-errors and tool stresses for each process. Injection forging tests were carried out in a factory environment with the aim of verifying the FE results and of confirming process and tool-design feasibility. Based on the results from these studies, the feasibility of replacing multisteps forging with injection forging was confirmed. It was established that injection forging may demand higher a forming force in its single step but it would consume less energy. Also, there is less chance of developing flow faults during injection forging, which is critical for the forming of the automotive fasteners. Nevertheless, due to the complex material-flow in injection forging and large die-deflections, a dedicated tool-design for compensating for forming-errors and for enhancing tool-life has to be enabled for the forging production applications.