关键词: 检验公差带, 基准要素, 实体要求, 转移公差, 计算方法

Abstract: When datum features apply the Maximum Material Condition or Least Material Condition (MMC/LMC),shift tolerance can be added to the stated tolerance of related feature,thereby enlarge the Inspection Tolerance Zone (ITZ) and improving the acceptance rate of parts.A general calculation method of ITZ when three datum features apply MMC/LMC was proposed.The combination of three datum features when all apply the MMC/LMC was investigated,and the construction method of Measurement Coordinate System (MCS) and Design Coordinate System (DCS) based on different condition of datum feature combinations was proposed.The Datum Feature Simulators (DFSs) at actual virtual condition were used to construct MCS,and DFSs at the stated MMC/LMC condition were used to construct DCS.In the proposed methodology,the relative position between DCS and MCS was simulated by series combination of linkage mechanisms,and the kinematic envelope of design tolerance zone on the linkage curve corresponded to ITZ.An example was given to demonstrate the effectiveness of the proposed method.

Key words: inspection tolerance zone, datum features, material condition, shift tolerance, calculation method