Establishment and application of a process dimension tree
提出用带下标英文字母表示加工表面、有向线段表示工序尺寸的方法，建立工序尺寸树和完整尺寸模型，直观反映尺寸关系，简化工艺路线优化，并揭示毛坯尺寸基准对粗加工余量和尺寸精度的影响。
Process planning, dimensions and tolerance greatly influence the quality and cost of a part in machining processes. In this paper, English letters with subscripts are used denote each surface of a part in machining processes, and directed line segments are used to represent process dimensions. A process dimension tree and a complete dimension model are also established. The process dimension tree expresses the machining sequences of each surface and the process datum of each process dimension. The tree also intuitively and completely reflects the relations of all dimensions. The established process dimension tree simplifies the change or optimisation of process route and indicates the influence of the dimensioning datum of a blank on rough machining allowances and dimensional accuracy. This simple and efficient approach may be used to establish dimension models, improve process route and optimise blank dimensioning.