An example is given to demonstrate the proposed method. The combination of the datum features for applying MMC/LMC is investigated, and the combination principles of the representation mechanism for different combinations of the datum features are discussed. In the proposed methodology, the relative position between the design DRF and the measurement DRF is simulated by the series combination of two linkage mechanisms, the measurement DRF is fixed at the mechanism frame, the design DRF is fixed at target linkage, and the kinematic envelope of the design tolerance zone at design DRF corresponds to the ITZ. Feel free to critisize any flaw in my thinking. Same for Cpm Aggregated Cpm for both axisses would be CpmSQRT (Cpm (x)+Cpm ) Just wanted to throw this at you. The Datum Feature Simulators (DFSs) at actual virtual condition are used to construct the measurement datum reference frame (DRF), and the DFSs at the stated MMC/LMC condition are used to construct the design DRF. So calculating a Cpm-X and Cpm-Y (Cpm for each of the axisses), would be: Cpm (x) (USL+'Bonus (x)' Xbar)-'Geometric deviation (x)' Xbar)/ 3 Std.dev. In this paper, a general calculation method of the inspection tolerance zone (ITZ) based on the linkage mechanism model is proposed. However, it is difficult to calculate the shift tolerance when more than one datum feature applies MMC/LMC. When the datum features apply the maximum or least material condition (MMC/LMC), the shift tolerance, because of the departure of the actual mating size of the datum features from their extreme condition, can be added to the stated tolerance of the related feature, thereby improving the acceptance rate of the parts.
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