Parameter optimized strain analysis of machine components for sensor application

Cutting forces are important parameters to describe the manufacturing process. For an adjustment with regard to optimal cutting parameters and minimal tool wear it is necessary to know the quantity and components of the forces. The direct measuring of cutting forces by means of force sensors demands an intervention in the construction of the tool. Therefore force sensors seldom can be applied on working machine tools. On the other hand the indirect determination of cutting forces by measuring strain of machine components is possible without changing the machine characteristic or its construction in many cases. The sensors may be attached on components in the main flux of force or secondary flux of force. The position of tool and workpiece, different workpiece geometry and setting of tools are varying parameters that have a great influence on the deformation of machine components. In the beginning of the development stage of a sensor system these parameters are not known or hardly to es timate. FEM calculations have been done on two examples, a chuck and a revolver, to analyze the behaviour of strain with different loads and geometry. The results of the FEM calculation are implemented into a linear mathematical model as a basis for the development of a sensor system. In this model Hooke's law of material behaviour is assumed for the use of strain sensors. Installed on a chuck this sensor system rotates with the spindle speed. In addition to the cutting forces the influences of centrifugal force and clamping force have to be taken into account. In this case a signal analysis separates static and periodic parts of the sensor signal. It allows the calculation of the clamping forces regarded as static and the cutting force as periodic parts of the sensor signal.