Modeling For Transmission And Conversion Of Hollow Circular Laser And Analysis On Coupling Between Laser And Materials In Three-Dimensional Laser Manufacturing

Laser cladding rapid prototyping is a technique which coupling the focused laser beam and the metal materials which enter into the spot simultaneously to Three-Dimensional Prototyping. But now the solid focused laser spot is commonly used in this technology, and the type of material feeding is the lateral material feeding or coaxial material feeding outside the laser. Under this laser spot and material feeding method, the stability of the coupling performance of the laser spot and the cladding material is very poor, which leads to the instability of the prototyping process, the very low metallurgical quality and the nonideal precision and the roughness of the work pieces. This paper uses a new type of hollow circular focusing system and adopted a method of inside-laser coaxial material feeding to clad. Paying heavy stress on the transmission conversion of this hollow circular laser and the coupling between optical and material.Using geometrical optics and ray tracing method, this paper establishes the hollow circular laser beam focusing system conversion model and simulates the energy distribution of the focused spot at different defocusing cross section. According to the research,the conclusiones can be geted as flollowing: when|z| is littler than 0.727mm,the focusing laser is solid spot, but it is hollow circular spot at the other defocusing cross sections. The energy distribution of the hollow circular laser beam is"bimodal-shape", according to which we can deduce that the energy absorbed at the scan direction of the hollow circular laser is"saddle-shape". At the same time we can get the relationship between hollow circular laser beam and duty circle at different defocusing cross section.This paper uses the approach of inside-laser coaxial material feeding cladding with the hollow circular laser to do the scanning direction test, and do the inside-laser coaxial power feeding cladding and inside-laser coaxial wired feeding cladding separately.It is proved that:the inside-laser coaxial material feeding cladding can achieve a real coaxial of the laser material,the optical and material can coupe accurately, eliminating completely the impaction of the scanning direction to the cladding quality. Compared with the"Gaussion-shape"of solid spot, the"Saddle-shape"distribution of the energy absorbed at the scan dirction of the hollow circular laser not only reduces the energy density gradient of the pool, but also provides more energy to the melting road side,and reduces the bad impact on melting road side caused by the shortage of the energy of the edge of the solid laser spot.Through anglicizing the prototyping modeling it is concluded that:the prototyping modeling surface is very smooth and form the metallurgical combination with the bade,the microstructures are very small, even,without impurities, porosity and other defects.