Deflection compensation on a force sensing mobile machine tool

Within this paper, a model based deflection compensation for a mobile machine tool prototype is presented. The model compensates the deflection of the tool center point (TCP) based on strain gauge measurements at the machines foot modules. The measured strains at each foot are used to calculate pose dependent gravitational forces as well as disturbance forces. These forces are then passed to the model. Hence, the model reconstructs the deflection of the TCP based on the measured forces at the foot modules

Thermally Induced Clamping Force Deviations in a Sensory Chuck for Thin-Walled Workpieces

Deviations between nominal and actual tolerances are a challenging problem during turning processes of thin-walled workpieces. One main cause of these deviations is the clamping force applied by the turning chuck to hold the workpiece. Due to the low stiffness of thin-walled workpieces, large workpiece deformations can occur even when clamping forces are low. For this reason, the clamping force needs to be precisely adjusted. A possible approach are chucks with integrated actuators. As a result of the more direct power transmission, these chucks have a potentially higher clamping force accuracy compared to conventional external actuation. However, integrated actuators are additional heart sources resulting in thermal loads and thermally induced deformations of the chuck components. Due to the resulting mechanical distortion of the chuck system, the precise adjustment of clamping forces is not possible. Thus, this paper evaluates the thermally induced clamping force deviations on a novel turning chuck with four integrated electric drives. A test bench is used to analyse both a single drive and the combination of all four drives regarding the temperature effect on the clamping force adjustability. A clamping force deviation of up to 26% is observed. Based on the measured chuck temperature, a compensation method is introduced leading to a clamping force accuracy of 96.9%