曲面塑料模具激光熔覆再制造快速加工路径生成方法

对于曲面塑料模具,在其表面快速生成激光熔覆加工路径非常困难。针对这种情况,直接以零件的逆向点云模型为研究对象,通过平面与点云求交得到以密集离散点表示的近似激光扫描路径,避免了反求建模的过程。以离焦量变化极限为约束条件,在路径上搜索插补点。提出利用插补点的最近点来计算插补点曲面法向矢量作为激光束姿态的近似快速算法。应用镍基自熔性合金粉对P20材质的模具零件曲面表面进行了试验。金相分析表明所形成熔覆层组织均匀、致密,缺陷稀少;熔覆层与基体之间形成冶金结合。熔覆层中部组织出现了垂直于界面生长的柱状树枝晶,而在顶部许多的柱状树枝晶发育成等轴树枝晶。熔覆层的平均显微硬度达到330~350 HV0.2。路径中段的熔覆层厚度比起始点增加了10%。

Rapid Processing Path Generation Method for Curved Surface Plastic Mold Remanufacturing by Laser Cladding

It is difficult to generate a rapid laser cladding processing path on surfaces for plastic mold. Regarding the reverse point cloud model of parts as the research subject, the approximate processing path was developed by calculating the intersection of the plane and point cloud. This method avoids a complex reverse process. The processing points on the path were searched based on the defocus distance limit criteria. Using the nearest point to the processing point, a fast algorithm was presented to calculate normal vector of the processing points on the curved surface. Mold parts made of P20 material with a curved surface were tested using Ni base alloy powder. Metallographic analysis show that the laser cladding layer has dense microstructure, and metallurgically bonds to the substrate. In the middle of the cladding layer, columnar dendrites grow perpendicular to the interface, but many columnar dendrites at the top develop into equiaxed dendrites. The microhardness of the cladding zone is 330-350 HV_0.2. The cladding layer thickness in the middle of the path is 10% higher than that of the starting point.