Exploration of surface roughness measurement solutions for additive manufactured components built by multi-axis tool paths

A thin-wall sphere dome set is manufactured without supports being required using a direct energy deposition additive manufacturing process. A multi-axis tool path combined with a partitioning strategy is utilized. Two partitioning strategies and a rotary toolpath build strategy are applied. The partitioned samples have a 45 mm diameter, and the rotary toolpath sample has a 60 mm diameter. The wall thickness is 2 mm for all case studies. The partitioning strategy provides an opportunity to fabricate geometries without the need for support structures, but it introduces physical properties variations. Large surface irregularities are noticed at the transition points between partitions, which escalates the roughness values drastically in these regions. The surface roughness variations within a build section and across partitions are explored in this paper. Process planning, data collection, and experimental/numerical procedures are developed and implemented to investigate the surface roughness variations (Ra measurement). Two solutions are developed: (i) a destructive testing approach (sections embedded into epoxy) and (ii) a contactless approach. The destructive testing solution uses the magnified pictures of the exposed surface edges of mount samples as input data. The other solution uses a 3D point cloud of the surface. The mount solution results show better accuracy, but the data collection process is time consuming and labour intensive. The destructive test method can detect small textures, while the contactless method is more appropriate for large-scale bead products. This research shows measuring surface roughness is challenging and further development is needed to be developed to be able to effectively measure Ra for AM built components.

采用直接能量沉积增材制造工艺制造薄壁球顶组件，无需支撑。利用了多轴刀具路径以及分区策略。应用了两种分区策略和一种旋转刀具路径构建策略。分区样本直径为45毫米，旋转刀具路径样本直径为60毫米。所有案例研究的壁厚均为2毫米。分区策略为制造无需支撑结构的几何形状提供了机会，但它会导致物理性能变化。在分区之间的过渡点处发现有较大的表面不规则性，这些区域的粗糙度值急剧上升。本文探讨了构建截面内以及跨分区的表面粗糙度变化。制定并实施了工艺规划、数据收集以及实验/数值程序，以研究表面粗糙度变化（Ra测量）。开发了两种解决方案：（i）一种破坏性测试方法（将切片嵌入环氧树脂中）和（ii）一种非接触式方法。破坏性测试解决方案将安装样本暴露表面边缘的放大图片用作输入数据。另一种解决方案使用表面的三维点云。安装解决方案的结果显示出更高的准确性，但数据收集过程耗时且劳动强度大。破坏性测试方法可以检测到微小的纹理，而非接触式方法更适用于大规模的熔珠产品。这项研究表明，测量表面粗糙度具有挑战性，需要进一步开发，以便能够有效地测量增材制造构建部件的Ra值。