Strain gauge based sensing hydraulic fixtures

Clamping errors in workpiece positioning decrease the outcome of machine tools. To avoid rejects, which occur due to failures in the clamping, a sensory clamping system is being investigated at the Institute of Production Engineering and Machine Tools (IFW). The aim is to provide hydraulic clamping elements with sensory capabilities to enable condition and process monitoring of the clamping system inside the harsh environment of a machine tool.Firstly, this paper gives a general survey of the targeted application and the concept to achieve a sensory clamping system for the industrial use in series production. Then it focuses on the integration of strain gauges into the exemplary chosen hydraulic swing clamp. Hereby, it shows the qualification of strain gauges for the estimation of different objectives, like hydraulic pressure, piston position, and external loads. Therefore, methods for the identification of suitable positions for the strain gauge integration into the clamping element are being discussed on the basis of experimental results and simulations. Furthermore, a method to achieve higher sensor sensitivity by 71% to the detriment of the compliance by 1.3% is presented.