基準

定義

検査または加工で参照する基準要素。

フロントマターの定義を基準にし、段取り・加工・検査で同じ意味として扱います。

公式/ルール

• Lock the primary, secondary, and tertiary datum sequence before offsets or inspection decisions are accepted.
• If the datum changes, re-zero the setup and re-check any dependent dimensions.

代表的な範囲

• Use the same datum scheme from setup sheet to CMM report so result interpretation does not drift.
• If the drawing switches datums, treat it as a new verification condition.

現場シナリオ

• Re-establish the datum after reclamping a part before trusting previous offset values.
• Use the datum hierarchy to decide whether an out-of-position feature comes from setup or toolpath.

よくある問題/トラブルシュート

• If measurement results conflict between operators, verify that the same datum feature and probing sequence were used.
• If offsets are repeatedly corrected in the wrong direction, confirm that the setup zero still matches the intended datum.

関連ツール

• Gdt Reference
• True Position Calculator