Comparison of 5-Axis and 3-Axis Finish Machining of Hydroforming Die Inserts

The recent growth in hydroforming technology has sparked interest in alternative methods to the current conventional die manufacturing techniques. Hydroforming dies typically have shallow forming channels and open, low curvature surfaces, making them ideally suited for 5-axis machining. To fully appreciate the benefits and to properly demonstrate the capabilities of 5-axis machining for hydroforming dies, a comparison of 5-axis and 3-axis finish machining was done. Two hydroforming die insert sets were machined on a 5-axis machine with a tilt/rotary table. The tool paths for 5-axis machining were generated using custom software based on a modified form of a tool positioning strategy called the principal axis method. The quality of generated 3-axis toolpaths was verified against the machining times of a third set of die inserts, similar to those machined in 5-axis, by an independent industrial mould and die manufacturer using a 3-axis high-speed machine. A comparison of the generated 3-axis paths versus the 5-axis paths for one of the die inserts was made using total finish machining tool path lengths to eliminate differences in machines. The results show that the generated 3-axis tool paths are longer than the 5-axis paths by at least 247%. The paper discusses the different tool-path generation methods along with the geometry of cusp formation and the effect of tool selection. Methods to improve the 3-axis results are also presented.