In-process tool pose measurement in incremental sheet forming

Robotic incremental sheet forming is flexible, but involves significant forming path deviations, demanding an in-process tool pose measuring system. To achieve a 50 mu m positional and 0.05 degrees orientational measuring uncertainty, a triangulation system using multiple shadow imaging sensors is proposed. LEDs with different wavelengths are attached to the tool holder and cast a shadow of the sensor's mask though a color filter on the camera chip behind it. The LED position is obtained by processing the shadow images of at least two sensors. Conducted experiments demonstrate that the filters effectively separate the shadows, ensuring cross-sensitivities as low as the random error of measuring a single LED position. The unpredictable scatter in the systematic error dominates the LED position measurement uncertainty. However, a Monte Carlo simulation shows the feasibility of achieving the required uncertainty for tool pose measurement.