Optical probing for CNC machining of large parts made from fiber-reinforced polymer composite materials

In machining of large fiber-reinforced polymer (FRP) composite parts, the part must be precisely located before machining. The exact location and shape are usually determined by the probing systems employing a touch probe integrated with a CNC machine. When measuring a large number of points, touch probing consumes a significant amount of time and adversely affects the utilization of the CNC machine in serial production. In order to increase the probing speed and acquire additional details, a new optical probing operating on the laser triangulation measuring principle is developed. The paper describes the measuring principle, system integration, neural network as the measuring system transfer function, and the calibration process. When measuring polyester or epoxy resin-based materials, the laser light penetrates into the part and reflects back inside of the part. This interference is successfully neutralized by the calibration body made from the same FRP material as the measured part. Verification of the calibration body and the machine coordinate system alignment is demonstrated by comparison of corrections determined with the optical and touch probing.