F4:Parallelism Validation

Author: Admin

Summary

F4 validates parallelism against the ASME logic in the F4 Application and enforces datum, feature-type, modifier, and pattern rules.

A primary datum reference is required.
Parallelism is valid only for a planar surface, a planar feature of size, or a cylindrical feature of size.
Parallelism cannot be applied to a pattern.
Unequally disposed is not allowed.
Planar surface: diameter, LMC, MMC, and projected tolerance zone are not allowed.
Planar FOS: diameter, projected tolerance zone, and tangent plane are not allowed.
Cylindrical FOS: diameter is required; tangent plane is not allowed.
If a linked size dimension exists, F4 compares the FCF tolerance to the size tolerance.
If no size dimension is linked, F4 skips the size tolerance comparison.

F4 behavior

Missing datum

Parallelism requires a primary datum reference; missing datums are rejected.

F4 behavior

Invalid feature type

If the FCF is applied to anything other than a planar surface, planar FOS, or cylindrical FOS, F4 flags non-compliance.

F4 behavior

Pattern not allowed

Parallelism applied to a pattern is rejected.

F4 behavior

Not parallel to datum

If the toleranced feature is not parallel to the primary datum, F4 flags non-compliance.

F4 behavior

Same feature as datum

If the toleranced feature is the same feature as the primary datum, F4 flags non-compliance.

F4 behavior

Missing diameter

Cylindrical feature of size parallelism must include the diameter modifier.

F4 behavior

Prohibited modifiers

Use the modifier rules for planar surfaces, planar FOS, and cylindrical FOS; prohibited modifiers are rejected.

Valid: planar surface parallel to datum A.
Valid: cylindrical feature of size parallel to datum A with the diameter modifier.
Invalid: missing datum reference or pattern application.