该方法使特征定位基准在特征造型过程中保持不变，且不随特征定位约束参数的改变而变化，能很好地满足参数化变动设计与拓扑结构变异的要求。

This method keeps the location base of form feature invariance during the feature modeling and editing, and it is suitable for feature parametric variational design and topological variation.

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通过对非设计基准定位的工件批量性加工实例的分析，探求其工序尺寸及其偏差的简捷计算法。

Through analyzing the example of a batch of production located by non-design reference, the paper seeks a kind of simple and convenient arithmetic for the size and deviation of working procedure.

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精基准选择：要符合基准重合原则，尽可能选设计基准或装配基准作为定位基准。

Fine datum choice: Must conform to the datum superposition principle, chooses the design datum or the assembly datum as far as possible takes the localization datum.

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