真位置

定义

控制特征相对基准定位误差的几何公差。

以前置元数据中的定义作为统一语义，并在装夹、加工与检验环节保持一致。

公式/规则

• 二维孔位常用计算可写为 TP = 2 × sqrt((ΔX)^2 + (ΔY)^2)，单位与图纸一致。
• 位置度必须在当前基准体系下判定，而不是按自由坐标直接比较。

典型范围

• Review the tolerance as a diametrical zone and confirm whether MMC/LMC modifiers change the effective limit.
• Check X/Y drift together; a single-axis result can look acceptable while combined position does not.

现场场景

• Use true position to review hole patterns before committing rework on a precision plate.
• Compare measured center drift with the active datum before moving offsets on a multi-feature part.

常见错误/排障

• If holes fail true position unexpectedly, verify both datum lock and hole-center measurement method before reworking parts.
• If correction makes one feature better but another worse, check whether the active datum or pattern origin is wrong.

相关工具

• True Position Calculator
• Gdt Reference