F4:Position MSS Validation
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Summary
F4 validates position MSS FCFs against the ASME logic in the F4 Application and enforces feature-type, basic dimension, datum, modifier, and segment rules.
Validation rules
- Position MSS applies only when all segments are position tolerances; mixed symbols use the general MSS validator.
- MSS requires more than one segment; single-segment position uses the standard position validator.
- The toleranced feature must be a planar or cylindrical feature of size.
- Basic dimensions are required to establish true position.
- Pattern application is recorded as a decision for MSS segments.
- Planar features of size require datum references; cylindrical features of size may omit datums.
- Planar features of size prohibit diameter and projected tolerance zone modifiers.
- Tangent plane and unequal modifiers are not allowed for position MSS.
- Cylindrical features of size require the diameter modifier during per-segment position validation.
- Duplicate segments (repeating tolerance symbols or datum sets) are rejected.
- After MSS checks pass, each segment is validated with the standard position validator.
Warnings and errors
F4 behavior
- Invalid feature type
If the position MSS is applied to a non-FOS feature, F4 flags non-compliance.
F4 behavior
- Basic dimensions missing
If basic dimensions do not locate the true position, F4 flags non-compliance.
F4 behavior
- Missing datum for planar FOS
Planar features of size must reference datums in the MSS FCF.
F4 behavior
- Prohibited modifiers
Diameter or projected tolerance zone on planar FOS, or tangent and unequal modifiers, are rejected.
F4 behavior
- Duplicate segments
Repeating the same tolerance symbol or datum set across segments is not allowed.
Examples
- Valid: position MSS on a hole pattern with basic dimensions, datums, and distinct segment datums.
- Invalid: planar MSS without datums or with repeated datum sets.