抄録
Laser Based Additive Manufacturing (LBAM, laser metal powder deposition) is a promising manufacturing technology that can be widely applied to part reparation, surface modification, and Solid Freeform Fabrication (SFF). The thermal behavior of the molten pool is one of the key factors that influences the laser deposition performances such as geometrical accuracy and material properties. In this paper, the infrared image sensing of the molten pool is studied for the closed-loop control of the LBAM process. A high frame-rate (up to 800frame/s) camera with a near infrared (NIR) filter is installed coaxially at the top of the laser-nozzle setup. The camera setup provides a full view of the NIR image of the molten pool and its omnidirectional to the scanning directions. The high frame-rate camera with the NIR filter is calibrated by a black body. The edge of the molten pool in the NIR image is verified by the normal image acquired by an additional high shutter-speed camera installed beside the laser head. The calibrated NIR camera can measure the temperature and geometrical features of the molten poll accurately, and provide a quantitative prediction of the cooling rate. The laser output power is controlled according to the size of the molten pool. The experimental results show that the closed-loop control achieves a great performance improvement for the laser deposition process.
