Description
Monitoring machining processes can help to increase the quality of machined workpieces. However, not all relevant information (e.g. process forces) can be sufficiently obtained by observing the drive signals. Various sensory devices have been developed during the last years to overcome this deficit. Such sensory devices include spindle slides, clamping systems, and tool holders. These devices are usually exclusively designed for individual machines or processes. Thus, these systems can rarely be adapted for other use cases affecting their scope of application. Other sensor concepts reduce the stiffness of the machine tool and therefore the machining accuracy. As a standardized component in machine tools, linear guides offer the potential to measure forces without reducing the stiffness of the machine tool. Thus, this paper presents a novel approach for force measurement with sensory linear rolling guides. Compared to previous approaches, the number of sensors is reduced, decreasing manufacturing effort. Considering the high stiffness of the guide carriage and the resulting low strains, foil-based modified metal strain gauges with a gauge factor k ≈ 10 are used to measure forces perpendicular to the guide rail. Based on an FE-simulation, adequate sensor positions are selected. A prototype of the sensory guide carriage is evaluated on a tensile test stand to determine the minimal measurable force based on the signal-tonoise ratio and the signal drift. The signals of the strain gauges allow a force resolution of 0.11 % of the load rating of the guide carriage. This is achieved by using a Kalman filter based state estimation model to compensate for the noise.
