A New Method for Incremental Sheet Metal Bending Based on Minimum Energy Principle

Sheet Metal Bending is a common process used in many heavy industry sectors such as shipbuilding. The traditional method is the so-called line heating, which is not only labor intensive but also inefficient and error-prone. This paper presents a new incremental bending method based on minimum energy principle. In this method, the steel blank is supported by an array of hydraulic cylinders with rotary head. This ensures the blank being properly lifted regardless of its shape and size. First, the incremental punching trajectory is generated based on the minimum energy principle. Assuming that the blank can be approximated by a number of strips and each strip is supported at its end. Then the strip can be described by a simply supported beam. According to the minimum energy principle, the punch location will be at where the error between the current shape and desired shape is maximum. Upon obtaining the punch location, the bending of the strip is also computed completing one incremental step. The new method is tested in a custom build incremental bending machine. Based on the experiment results, the method is successfully used in sheet metal bending. Comparing to the existing methods, the new method has a number of advantages, including simple, fast and highly energy efficient.