cdsl-cad/backend/agent/skills/cad-engine/references/part-skills/source/planning/flange.planning.md

Flange Planning Skill

When to use

• The request describes a circular flange, coupling flange, pipe flange, gasket-like flange, flanged sleeve, or flanged cylindrical adapter.
• The part has a central axis, central bore, and fastener holes arranged around a pitch circle.
• The flange connects, spaces, seals, or mounts coaxial parts such as shafts, pipes, bearings, covers, or couplings.

Do not use when

• The word flange only means a side tab, flat ear, or rectangular mounting plate extension.
• The hole layout is a rectangular grid, edge row, or arbitrary plate pattern.
• The model is primarily a plain shaft, washer, pulley, bearing assembly, or bracket without a true circular flange body.

Recognition features

• Axisymmetric disc, annular ring, raised hub, sleeve, stepped boss, or cylindrical landing surface.
• Central through bore, pilot bore, counterbore, recess, seal land, or shaft clearance on the main axis.
• Bolt holes are evenly spaced by angle around the same center as the bore.
• Optional recesses, gasket grooves, chamfers, fillets, or counterbores are secondary to the coaxial flange body.

Core invariants

• The outer diameter, bore, hub, sleeve, recesses, and bolt circle share one central construction axis.
• Build the rotational body before cutting the bolt holes.
• Define bolt-circle diameter separately from outer diameter and bore diameter.
• Create one correct bolt hole, then circular-pattern the cut feature over 360 degrees.
• Do not replace the bolt circle with a rectangular hole grid.
• Keep fillets, chamfers, and cosmetic edge breaks late in the sequence.

Parameter roles

• outer_diameter defines the flange envelope.
• thickness defines the disc or flange plate depth.
• bore_diameter defines shaft or pipe clearance.
• hub_diameter, hub_height, and pilot_diameter define raised coaxial features.
• bolt_circle_diameter, bolt_count, bolt_hole_diameter, and start_angle define the fastener pattern.
• counterbore_diameter, counterbore_depth, gasket_groove_width, and gasket_groove_depth define secondary seats.

Construction sequence

1. Establish the central axis and primary reference plane.
2. Create the flange disc and any coaxial hub or sleeve using revolve for stepped profiles, or extrude circles for simple flat discs.
3. Cut the central bore through the flange and hub on the same axis.
4. Add one bolt hole at the pitch radius using the correct fastener hole type.
5. Circular-pattern that cut around the central axis with equal angular spacing.
6. Add recesses, gasket grooves, counterbores, chamfers, and fillets after the bore and bolt pattern are stable.

Common failures

• Off-axis bore relative to hub or outer diameter.
• Manual bolt hole placement that produces unequal angular spacing.
• Confusing a rectangular mounting plate with a flange because both have multiple holes.
• Forgetting the central bore and creating only a circular plate with holes.
• Applying large fillets before the bolt pattern and causing feature failure.

Evidence summary

• Current library evidence: 45 previously reviewed SCAD58 flange-like models.
• Latest run evidence: accepted insights for circular flange bolt holes, circular pattern around a central bore, revolved axisymmetric bodies, and coaxial cylindrical features.
• Frequent operations in the latest run: Revolution, Extrusion, Cut, HoleWzd, CircularPattern, Chamfer, Fillet.
• Source: CAD-SkillX offline review of SCAD58 descriptions, STEP summaries, and SolidWorks feature evidence.

Retrieval metadata

Triggers:

• flange
• circular flange
• pipe flange
• coupling flange
• flanged sleeve

Secondary triggers:

• bolt circle
• pitch circle
• central bore
• raised hub
• gasket groove
• pilot diameter

Operation triggers:

• revolve profile
• extrude circular disc
• cut central bore
• circular pattern
• counterbore bolt holes

Exclusions:

• mounting plate
• rectangular hole grid
• side tab
• plain shaft
• complete bearing