High speed impact cutting in tubular applications
Lightweight design is gaining more and more importance in several applications. Due to the requirement of reducing fuel consumption and related CO2 emissions, this concept plays an increasing role. Besides the application of lightweight-related materials in car bodies and suspension parts, the part designs themselves also become more and more related to weight saving. It was shown in several projects that the application of closed profiles in car body structures is an effective way to reduce the weight using comparable or increased stiffness. Based on this trend, hydroforming has also become a focus for car manufacturers again. One example is the car body of the current Ford Fusion, which contains roof frames and B-pillars manufactured by hydroforming. In addition to the forming technology, the trimming of these profile-based components is a key issue regarding process reliability, part quality, cycle time, and finally, the cost per part. Beside the known technology of piercing inside the hydroforming die, laser trimming, and rarely drilling, are state of the art in industrial production processes. Piercing inside the hydroforming die also provides the known advantage of referencing and final shaping in one step and one die. The related tooling certainly is complex and the effort for process adjustment is high. The great advantage of laser trimming lies in the flexibility; its disadvantages comprise high cycle times and limited accuracy. The application range of mechanical shear cutting is limited by the requirement of a mandrel inside the profile. High Speed Impact Cutting (HSIC) provides numerous advantages due to adiabatic effects inside the shear zone such as clean material separation, right angular cutting edges and less burr. For the application in tubes and profiles the high process velocity provides an additional effect for reducing the deformation due to mass inertia. This article describes the technological advantages and limits of HSIC and its application in tubes and profiles, the relevant tool technology and experimental facilities. One research focus comprised showing that a mandrel could be completely avoided during piercing operations in tubes and closed profiles.