HoloPort - design and integration of a digital holographic 3-D sensor in machine tools

Manufacturing of high-precision components requires accuracies that even the most modern processing machines are often unable to deliver reliably. Slightly worn tools, incorrectly calibrated sensors or even different trajectories can lead to results that do not comply with the desired specifications. However, quality control is still mainly performed on randomized samples outside the machine tool in special measuring rooms. Therefore, closed-loop quality control becomes a cumbersome iterative process. With HoloPort, we present a digital holographic sensor system that is capable of measuring the complete topography of machined components with sub-micrometer precision directly inside a tooling machine. To our knowledge, HoloPort is the first wireless interferometric sensor inside a machine tool worldwide. As it is fully integrated, it features not only a multiwavelength interferometer but also a miniaturized graphics processing unit (GPU). This allows for full data evaluation directly in the sensor. A single measurement is taken and processed within 3 s during wireless operation. HoloPort is easy to integrate into a variety of machine tools. This contribution includes detailed information about the sensor architecture. Experimental results on milled parts demonstrate the performance of the system and illustrate possible inline applications as well as future perspectives for the sensor.