激光选区熔化成型可控超轻结构化零件的孔隙生成效果

本文主要研究了孔隙率等参数可控的自动超轻结构化金属零件的增材制造。以方块零件及一个具有复杂外形的零件为研究对象,分析了面向激光选区熔化工艺的可控超轻结构化零件的孔隙生成效果,重点探讨了成型工艺对超轻结构化零件孔隙率的影响。结果显示:通过计算机数值计算,可将方块CAD模型快速自动转化为可控超轻结构化模型,计算孔隙率误差可控制在±2%以内;激光深穿透现象会导致带悬垂面内壁的壁厚增加,所引起的孔隙率误差值为负值,且计算孔隙率越大,负值倾向越严重;而成型工艺性不致密导致的孔隙率误差为正值,且在相同工艺条件下,计算孔隙率越大,该误差值越小。故为使总孔隙率误差能较好地反映超轻结构网格孔隙的控制精度,应提高成型时实体部分的致密性。按45%设定孔隙率成功地将具有复杂结构的零件转化为计算孔隙率为44.62%的超轻结构化模型,采用高致密性激光选区熔化工艺成型后,实测孔隙率为42.94%,无悬垂面的内壁壁厚误差≤0.06mm,达到了较好的超轻结构控制效果。

Pore forming results of controllable ultra-light structured parts by selective laser melting

In this paper, the addictive manufacturing of automatic ultra-light structural metal parts with controllable parameters, such as porosity, was researched. Through block shaped parts and a part with complicated structure, the pore forming results of controllable ultra-light structural parts manufactured by selective laser melting was analyzed. Influences of forming technology on porosity of ultra-light structural parts were mainly discussed. The result is showed: through numerical calculation of computer, block shaped CAD model can be rapidly and automatically transformed into a controllable ultra-light structural model. Moreover, the calculation porosity error is controlled within ±2%. The experiment also shows that laser deep penetration phenomena may lead to the increase of inner wall thickness for the dangling surface, causing the negative value for the porosity error. Furthermore, the larger the calculation porosity is, the worse the negative value is. On the other hand, non-compactness of forming process may induce positive porosity error. Under the same technological condition, the larger the calculation porosity is, the smaller the error value of porosity is. In order to make the total error value of porosity can better reflect the control accuracy of the ultra-light structured pore, the density of material part of the object should be improved at the time of forming. Parts with complex structure have been successfully transformed into ultra-light structured model with 44.62% of calculation porosity according to 45% set porosity. Hgh-density selective laser melting technology is used in this paper with 42.94% of the actual measurement porosity and ≤0.06 mm of inner wall thickness error for the surface without dangling surface, which realizes a better ultra-light structured control effect.