cdsl-cad/backend/agent/skills/cad-engine/references/part-skills/source/functional/symmetric-feature-layout.functional.md

Symmetric Feature Layout Functional Skill

When to use

• A part has holes, cutouts, bosses, tabs, ribs, or slots arranged symmetrically about a centerline, midplane, or axis.
• The prompt mentions symmetric holes, mirrored features, balanced mounting, centered layout, equal offsets, or left/right duplicates.

Do not use when

• Features are intentionally asymmetric for clearance, indexing, handedness, or mating orientation.
• The only symmetry is the natural circular symmetry of a plain shaft or washer with no repeated secondary features.
• The model requires unique hand-placed features with different sizes.

Recognition features

• Hole pairs, mirrored slots, duplicated bosses, matching tabs, or opposite-side cutouts.
• SolidWorks features such as MirrorPattern or sketches with construction centerlines.
• Descriptions mention symmetry, balanced fastening, alignment, centered holes, or mirrored geometry.

Core invariants

• Define the symmetry plane, centerline, or axis before placing the seed feature.
• Model one side or one quadrant carefully, then mirror/pattern it.
• Keep symmetric features tied to the same dimensions so edits preserve balance.
• Do not mirror features that are explicitly handed or direction-specific.
• Combine with hole-type rules when mirrored features are fastener holes.

Parameter roles

• symmetry_plane or centerline defines the mirror reference.
• seed_feature defines the original hole, slot, boss, or cutout.
• offset_from_center, edge_margin, and pitch define placement.
• mirror_count, pattern_count, and quadrant_count define repetition intent.

Construction sequence

1. Identify the natural datum: plate centerline, bracket midplane, flange axis, or body midplane.
2. Create construction geometry for the symmetry reference.
3. Build the seed feature on one side with full dimensions.
4. Mirror or pattern the completed feature across the reference.
5. Verify that all mirrored features remain inside material and keep correct hole type/depth.
6. Apply common edge treatments after mirrored features are complete.

Common failures

• Manually placing mirrored holes and getting unequal offsets.
• Mirroring asymmetric features such as countersinks that should face a specific side.
• Losing thread/counterbore data during mirror or pattern.
• Creating a visually symmetric model with unconstrained feature positions.

Evidence summary

• Latest run evidence: 228 accepted functional insights contained symmetry, mirror, centerline, or pattern alignment signals.
• Strong repeated names include use_mirror_pattern_for_symmetry, position_holes_symmetrically, symmetrical_hole_placement, and use_mirror_for_symmetry.
• Frequent operations in the latest run: MirrorPattern, LinearPattern, HoleWzd, Cut, construction lines, Chamfer.
• Source model examples: 000124, 002620, 008006, 012598, 029447, 032081, 059866, 097101, 125932, 134012, 145543, 154893, 166339, 173306, 202020.
• Source: CAD-SkillX offline review of SCAD58 descriptions, STEP summaries, and SolidWorks feature evidence.

Retrieval metadata

Triggers:

• symmetric holes
• mirror pattern
• symmetry
• mirrored features
• centerline layout

Secondary triggers:

• balanced mounting
• equal offsets
• left right holes
• construction line
• midplane

Operation triggers:

• create construction centerline
• mirror feature
• pattern symmetric holes
• use equal constraints

Exclusions:

• asymmetric clearance
• handed part
• unique holes
• plain cylinder only