Study on influential factors for process monitoring and control in laser aided additive manufacturing

In this paper, the process monitoring and control in laser aided additive manufacturing (LAAM) were studied. Some key issues which affect the process monitoring and control were revealed and discussed in detail. The results show that the geometry of the parts affects the melt-pool temperature, especially where the heat dissipation is strongly limited. The power density distribution plays an important role for controlled LAAM process. The laser beam can only be defocused to a certain extent to avoid the insufficient power density due to the excessively enlarged beam size. This can cause defects on the clad surface and in the clad layer. Surface oxidation must be avoided during the process control, because surface oxidation can deteriorate the LAAM process, as indicated by the disturbances of the measured melt pool temperature. With the path-dependant process control, the dimensional accuracy of the deposition can be significantly improved.

► Process control based on IR-temperature can eliminate the heat accumulation and achieve oxidation-free clad surface.
► The laser beam can only be defocused to certain extent to avoid insufficient power density and the clad defects.
► Surface oxidation must be to eliminate the disturbed IR-temperature which can deteriorate the LAAM process control.
► With the path-dependant process control, the dimensional accuracy of the deposition can be significantly improved.