Optimization of trimming process in cold forging of steel bolts by Taguchi method

In this study, die-service life analysis of hexagonal trimming dies with different edge radius and cutting width was performed. The trimming dies were prepared by grinding the front face of the die due to desired cutting width and edge radius. Prepared dies were used in cold forging of steel M6x25 hexagonal bolts and service life of each die were determined in terms of number of bolts that they can produce until they experience fracture. Numerical models of trimming operation with varying cutting width were also prepared in finite element software simufact.forming to conduct stress analysis. Production trials and finite element analysis showed that service life of trimming die was significantly affected by cutting width. It was seen that die-service life increases linearly with increasing cutting width within an optimum range of 0.8 and 1.2 mm. Similarly, the die-service life improved with increasing edge radius values. Moreover, the trimming operation carried out by using hexagonal trimming die was optimized with Taguchi method by defining 5 design parameters and 3 levels for each parameter. Minimizing the peak trimming load and maximizing the peak damage value were determined as the objective functions to find the most effective design parameters. According to the Taguchi results, the cutting width and stopping distance were seen to have significant impact on peak trimming load while the edge radius was determined to be effective on the peak damage value.