A system calibration method for an embedded fringe projection system in a commercial electron beam powder bed fusion additive manufacturing machine (EBAM)

Additive manufacturing (AM) processing technique can rapidly and efficiently fabricate three-dimensional (3D) parts of complex shapes and intricate structures that is not achievable using traditional methods, especially for metal AM by fusing metal powder in a layer-by-layer fashion. In these powder fusion machines, an in-situ inspection system to monitor the printed surface and preprint powder bed as the build cycle proceeds is important. Fringe projection profilometry is well-known for its ability to provide fast, high-precision, and full-field 3D measurement of objects in a non-contact manner. The implementation of a fringe projection system requires that the system is pre-calibrated to obtain high measurement precision and repeatability. This paper presents two calibration methods for an AM-based in-situ fringe projection system using a polynomial calibration. A circle ring board and a blank board are used during the system calibration. In addition to obtain good depth calibration results, more accurate transverse calibration results can be obtained. The proposed calibration methods to reduce the texture effect in the process of calibration is outlined. Experimental results show that the proposed methods can improve measurement precision and repeatability. The proposed in-situ/in-process inspection system has been implemented within a commercial electron beam powder bed fusion additive manufacturing machine (EBAM), to demonstrate the capability for effective feedback during the manufacturing process.