Rotary draw bending (RDB) process is a profile bending process mostly used in industrial practices for bending metal tubes. Presently, RDB process is conducted by using geometry specific bending tools. The fundamental tools used in RDB process are pressure-die, bend-die, clamp-dies, wiper-die, collet and mandrel. These tools have simplified geometries with a semi-circular tool surface which corresponds to only one specific tube diameter. This makes RDB process inflexible because different tube diameters cannot be used with a specific set of bending tools. In addition to process-flexibility, the modern production regime of present era needs bending tools to be cost effective and light weight. This doctoral thesis is aimed to utilize modern manufacturing techniques, i.e., 3D printing processes and digital twin of RDB process, to develop the geometric design of bending tools which should be cost effective, light weight and provides process-flexibility to RDB process. A digital twin of the RDB process is developed and the accuracy of the digital twin is verified by comparing the FE-simulation results with practically conducted experiments. The design factors which critically influence the tool design are identified through digital twin prototyping. The digital twin prototyping method encompasses systematic development and testing of 3D printed polymeric tools in RDB process. Topology optimization of a conventional tool geometry is conducted in order to identify minimum material required within the tool. The results obtained from digital twin prototyping and topology optimization envisioned the development of a hybrid tool. A hybrid tool consists of two different materials i.e., polymers and metals. The materials of a hybrid tool are selected from Ashby material charts on the basis of requirements resulting from process parameterization and topology optimization. A model of the hybrid tool is developed according to material properties of selected materials and identified tool design factors. The model is imported in digital twin of RDB process and tool performance is investigated by conducting process simulations with different tube diameters. After obtaining process feasibility through digital twin, the hybrid tool consisting of polymer - PLA and metal - stainless steel is practically 3D printed and experimentally tested in an actual RDB process. The experimental results demonstrates that a 3D printed hybrid tool is capable of conducting bending operations with different tube diameters while enabling significant material saving within the tool. A comparison is made between the novel 3D printed hybrid tools and conventional steel tools. A design formula is presented that determines the efficiency of bending tools through Tool Efficiency index (TEi). For practical applications, the geometry of 3D printed hybrid tools is standardized through aspect ratio and corresponding upscale size factors.
Muhammad Ali Kaleem (Thu,) studied this question.