Position-controlled joining by plastic deformation on the example of optical sensors

• Applicant: Professor Dr.-Ing. Peter Groche
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 460244297

Multi-axis force and torque measurement is used in many areas from medical applications to industrial applications to aerospace and aeronautics. In the context of the ongoing automation of process chains in Industry 4.0, the range of industrial applications has expanded considerably. For instance, force and torque control is becoming an increasingly important factor in many manufacturing processes. By acquiring process forces and torques, control approaches can be implemented and therefore a precise manufacturing of selected product properties can be achieved. Poor accessibility or failure-prone measuring positions typically prevent unambiguous measurements. In contrast, load-bearing structures and machine elements with integrated sensors enable the measurement of process forces and torques directly at the machine or tools without impairing their mechanical functionality. According to state-of-the-art, these structures are manufactured by integrating strain gage-based or piezoelectric sensors into metallic structures by different methods. In this context, joining by plastic deformation has proven to be an especially suitable process for the production of such sensory structures. Because of the high requirements on the design of the spring element to be integrated and thus of the joining process, sensory structures produced by forming technology have so far been limited to one or two measuring axes of force or torque. Moreover, the manufacturing effort and energy consumption of the associated measuring chain increases almost linearly with increasing the number of measuring axes. By contrast, optical contactless measuring concepts allow an increase of the measuring axes of sensor structures produced by forming technology to be realized without a complex design of the spring element and the joining process. The research team of the applicant developed an optical, camera-based sensor concept for the expansion of the measuring axes of sensory load-bearing structures produced by forming technology, allowing the measurement of up to six degrees of freedom at significantly reduced total costs of the measuring chain compared to conventional force and torque sensors. However, the replacement of spring elements by optoelectronic measuring chains requires an essential step in the joining process of the sensor: The process designs for the force- and form-fit joint of the spring element and the load-bearing structure that have been researched so far are aimed at controlling the pre-stress condition in the spring element. The optical contactless sensor concept, on the other hand, requires high positioning accuracy during assembly and thus a position control during the joining process. The present research project aims at the investigation of a position-controlled joining process, which in particular allows the integration of optical six-axis force and torque sensors into load-bearing tubular structures.

• DFG Programme: Research Grants