Current practice in three-dimensional (3D) part construction and product assembly within a digital mock-up (DMU) is based on the nominal sizing of geometry. This approach does not reflect real part dimensions when they are manufactured or the assembly conditions as they come together during the final build. The value of virtual assembly planning (VAP) using clash and gap detection is therefore limited to modeling error identification within the computer-aided design (CAD) domain for nominal conditions only. VAP could become a significantly more powerful tool if the 3D representation of components within the DMU were more representative of ‘as manufactured’ dimensions. This paper presents the evolution and validation of an enriched DMU (EDMU) introducing the concept of the hybrid assembly which represents components in sizes which can range between upper and lower dimensional limits in addition to the nominally defined form. The resulting capability has been exploited to enable a designer to perform tolerance analysis in the CAD domain in advance of manufacturing planning, allowing tolerance consideration earlier in the design process as the DMU evolves. This has the potential to reduce the time, effort and computational load associated with the application of statistical tolerance analysis by methods engineers later in the product development cycle when the costs associated with change are higher.

在数字模型（DMU）中进行三维（3D）零件构造和产品组装的当前做法是基于几何的标称尺寸。这种方法不能反映实际零件的尺寸，也不能反映最终零件在组装过程中的组装条件。因此，使用碰撞和缝隙检测的虚拟装配计划（VAP）的价值仅限于在计算机辅助设计（CAD）域内仅针对名义条件对错误识别进行建模。如果DMU中组件的3D表示更能代表“实际制造”尺寸，则VAP可能会成为功能更强大的工具。本文介绍了富集DMU（EDMU）的演变和验证，它引入了混合组件的概念，该组件表示名义上定义的形式之外，其尺寸在上限和下限尺寸之间的组件。已开发出的功能可以使设计人员在制造规划之前在CAD领域中执行公差分析，从而可以在DMU演变过程中的设计过程中尽早考虑公差。当与变更相关的成本较高时，这有可能减少方法工程师在产品开发周期的后期应用统计公差分析进行分析所花费的时间，精力和计算量。已利用所产生的功能使设计人员能够在制造规划之前在CAD领域中执行公差分析，从而在DMU演进时允许在设计过程中更早地考虑公差。当与变更相关的成本较高时，这有可能减少方法工程师在产品开发周期的后期应用统计公差分析进行分析所花费的时间，精力和计算量。已利用所产生的功能使设计人员能够在制造规划之前在CAD领域中执行公差分析，从而在DMU演进时允许在设计过程中更早地考虑公差。当与变更相关的成本较高时，这有可能减少方法工程师在产品开发周期的后期应用统计公差分析进行分析所花费的时间，精力和计算量。