Abstract
In robot-based incremental sheet forming, the forming robot is displaced due to the forming forces and the comparable low stiffness. As the forming forces can not be predicted precisely, the stiffness needs to be compensated based on the measurement of a force torque sensor. While previous approaches used precalculated lookup tables, this publication presents a multi body system robot model that can calculate the displacement of the tool center point in real-time. In incremental sheet forming, the supporting robot is typically force controlled to bring superimposed stress into the forming zone. Unfortunately, this could lead to oscillations in the stiffness compensation. The presented force control approach takes the stiffness compensation into account to ensure a smooth movement of the forming robot. In a series of 30 forming experiments the effectiveness of the developed stiffness compensation and force control is validated.
Highlights
1.1 double sided incremental forming (DSIF) parametersSheet metal parts are omnipresent in mechanical engineering
The forming forces in incremental sheet forming (ISF) lead to a displacement of the used heavy load industrial robots due to their comparably low stiffness that could be demonstrated in an experimental series
To compensate for the stiffness, a multi body system robot model has been developed which can calculate the angular displacement of the individual joints and the displacement of the tool center points (TCP)
Summary
Sheet metal parts are omnipresent in mechanical engineering. While high batch sizes can be effectively produced with processes like deep drawing, the production of low batch sizes and prototypes suffers from high costs and delivery times for tools. Double sided incremental forming (DSIF) has been developed which exhibits the advantages of TPIF without the need for a die by integrating a second tool into the forming process [4, 5]. This supporting tool mirrors the forming tool on the opposite side of the sheet, locally building a die (see Fig. 1). The combination of support force and support angle induces superimposed stress into the forming zone [8, 9] This leads to a purposeful increase of forming accuracy and formable wall angle [10, 11]
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