F4:Flatness Validation
More actions
Summary
F4 validates flatness against the ASME logic in the F4 Application and enforces feature-type, modifier, and pattern rules.
Validation rules
- Flatness is valid only for a planar surface or a planar feature of size.
- Flatness cannot reference datums.
- Flatness cannot be applied to a pattern.
- Always prohibited modifiers: diameter, projected tolerance zone, tangent plane, unequally disposed.
- Planar surface flatness also prohibits LMC and MMC.
- If a linked size dimension exists, F4 compares the FCF tolerance to the size tolerance unless the planar FOS exception applies.
Warnings and errors
F4 behavior
- Invalid feature type
If the FCF is applied to anything other than a planar surface or planar feature of size, F4 flags non-compliance.
F4 behavior
- Pattern not allowed
Flatness applied to a pattern is rejected.
F4 behavior
- Datum references
Any datum reference in a flatness FCF is rejected.
F4 behavior
- Prohibited modifiers
Projected tolerance zone, tangent plane, unequally disposed, and diameter are not allowed on flatness. LMC and MMC are also prohibited on planar surface flatness.
F4 behavior
- Tolerance exceeds size tolerance
When a linked size dimension exists and a comparison is required, F4 flags non-compliance if the flatness tolerance exceeds the size tolerance.
F4 behavior
- Conditional size link
If no size dimension is linked, F4 skips the size tolerance comparison. For planar features of size, F4 also skips the comparison when the planar FOS exception applies.
Examples
- Valid: flatness on a planar surface with no datums.
- Valid: flatness on a planar feature of size with allowed modifiers.
- Invalid: flatness with a datum reference or applied to a pattern.