Optical tool deflection measurement approach using shadow imaging

In incremental sheet forming, geometrical deviations occur due to deflections of the forming stylus. To compensate the deviations, a non-contact in-process tool deflection measurement is required that is capable of measuring the tool tip position with a measurement uncertainty of 15 μm in a volume of 2.0 m × 1.0 m × 0.2 m. For this purpose, an optical multi-sensor system is designed. Each sensor evaluates lateral shift and magnification of the shadow cast from the LED attached close to the tool tip, to enable measuring the lateral and axial tool tip position component, respectively. The experimental validation shows that the sensing principle is sufficiently robust regarding ambient light. As a result, despite a remaining systematic error after calibration that dominates the uncertainty, the measurement requirements are fulfilled by a single sensor regarding the lateral position component. For the axial position component, a triangulation with two sensors is necessary.