采用激光立体成形制备了层数逐渐增加的块状试样, 分析了零件竖直外侧壁向内倾斜的原因. 基于利用粉末累积高度重构单道熔覆层横截面轮廓的方法, 构建了描述竖直外侧壁轮廓逐层演化的分析模型. 利用该模型重构了不同单道熔覆层宽高比和激光束有效作用范围下的竖直外侧壁轮廓, 并分析了2者的影响. 结果表明, 逐层叠加过程中, 已沉积的熔覆层将影响之后熔覆层的形成; 由于单道熔覆层的横截面为弧形, 其与激光束相交形成的边界熔池将向零件内部收缩, 从而引起边界单道熔覆层向内收缩及竖直外侧壁向内侧倾斜; 随沉积高度增加, 倾斜程度减小并趋于消失. 初始单道熔覆层宽度一定时, 减小激光束有效作用范围有利于外侧壁趋于竖直但却增大其偏离量; 单道熔覆层宽高比对外侧壁的影响几乎可以忽略.

The vertical outside wall is prone to incline inward in laser solid forming, which will deteriorate the dimension precision and processing stability. For solving this problem, samples with different amount of deposited layers were prepared and the variation of boundary single-track clad shape and formation of vertical outside wall inclining inward were investigated. Based on the method of constructing cross-section profile of the single-track clad by height of powders accumulated in molten pool, an analytical model was developed to describe the evolution of vertical outside wall during multilayer superimposition. A series of vertical outside walls under different width/height ratios and critical defocus distance were constructed with this model to investigate their influence. Results indicate that the deposited single-track clad will influence the formation of single-track clad under depositing. Due to the arc-like cross-section profile of single-track clad, the molten pool will shrink inward, which leads the outer edge of boundary single-track clad to shrink inward then the vertical outside wall to incline inward. However, this incline will decrease with the increase of deposited height. For the initial single-track clad with fixed width, decreasing critical defocus distance can decrease the inward incline but increase the offset from the preset dimension. The width/height ratio almost has no effect on outside wall.