Development of a partial heating system for freeform bending with movable die

Freeform bending with movable die makes it possible to bend complex parts seamlessly without changing the bending tool. Currently, the focus of research and development is on compensating geometrical deviations to manufacture bent parts within the tolerances. However, the current inves-tigations do not take the material properties based on batch fluctuation before and after freeform bending, into account. This insufficient knowledge of mechanical properties leads to deviations in downstream machining processes and results in a time, and cost consuming compensation process. To minimize the influence of batch fluctuation during freeform bending a closed-loop control based on material properties is necessary. This work presents the development of an inductive part heating system, to influence the properties of the tubes during freeform bending and to serve as an additional actuator in a property based closed-loop control for freeform bending. The authors investigate the heat conduction for steel tubes made of P235 at temperatures under 600 °C with various static and dynamic experiments. In addi-tion, real bent tubes with a partial heated side (about 90 degree of the circumference) are analyzed according to differences in the bending radius and angle as well as differences in hardness. The results show that the partial heating has an influence on the bent geometry and on the hardness. The generated effect correlations extend the already existing predictive control structure for prop-erty-controlled freeform bending. The knowledge of this work helps to understand the interactions between mechanical properties and partial inductive heating during freeform bending and extends the degrees of freedom in the bending process.     «

Freeform bending with movable die makes it possible to bend complex parts seamlessly without changing the bending tool. Currently, the focus of research and development is on compensating geometrical deviations to manufacture bent parts within the tolerances. However, the current inves-tigations do not take the material properties based on batch fluctuation before and after freeform bending, into account. This insufficient knowledge of mechanical properties leads to deviations in downstream mach...     »