Self-regulation-effect in laser direct metal manufacturing

To fabricate fine thin-wall parts with smooth surface by open-loop laser direct metal manufacturing (LDMM) system, the uneven formed surface in forming process is analyzed and the effect of off-focused laser and off-focused powder on the shape of single-trace cladding layer, is investigated by single-trace cladding experiments. The results show that off-focused laser exerts a significant effect the thickness of single-trace cladding layer, and off-focused powder affects mainly the height of single-trace cladding layer. It is suggested that self-regulation-effect in the process of LDMM in the condition of negative off-focused powder enables to perfect the uneven shaped surface caused by instability of process parameters. The theoretical model of the influence of off-focused powder on deposition thickness in the condition of coaxial powder feeding is constructed, and regular pattern obtained from the model matches well with experimental results. Several thin-wall parts with smooth formed surface are fabricated in terms of the self-regulation-effect.