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Mechanical Harness Diagram Elements and Models

Summary

Identifies the elements and symbology used in mechanical harness diagrams (nailboard/fixture drawings, routing overlays) and proposes data models to capture geometry, annotations, materials, and hardware. Focus covers dimensions, splicing, shielding, wraps, ties, labels, and correlations between logical and mechanical views.

Use Cases for Filare

  • Generate mechanical overlays for manufacturing (board builds, clamp placement, length checks).
  • Provide field/service diagrams with physical routing, labels, and splice/shield details.
  • Maintain traceability between electrical nets, BOM items, and mechanical placement.

Technical Evaluation

  • Core elements (mechanical view):
  • Board/fixture outline; datum/grid; reference holes.
  • Harness path polylines with segment lengths, bend radii, breakout points.
  • Features: clamps/tie-downs/edge clips, grommets/bulkheads, pass-throughs, strain relief, boots/backshells.
  • Protective coverings: convolute/conduit, tape wraps, braid, heat-shrink sections with start/end positions.
  • Splices/junctions: inline barrel splices, junction blocks/modules; callouts for splice type and orientation.
  • Shielding: shield drain/termination location; backshell tie vs pigtail vs isolated.
  • Labels/markers: flag labels at breakouts, wire/cable IDs, zone references.
  • Dimensions: overall length, segment lengths, clamp spacing, breakout lengths; tolerance notes.
  • Symbols (commonly used):
  • Path: solid polyline with arrows for direction or assembly sequence.
  • Clamps/ties: circles/squares with clamp code; sometimes P-clamp icon; spacing note.
  • Grommet/bulkhead: ring/doorway symbol; callout for hole size and grommet part.
  • Splice: dot for simple inline, or barrel symbol with part number; junction block as rectangle with ports.
  • Shield termination: ground symbol or backshell glyph at connector end; pigtail shown as short branch to ground.
  • Protective coverings: hatched or double-line segments; heat-shrink/tape annotated with start/end distances and part.
  • Labels: flag icon or rectangular tag tied to path; text includes ID and sometimes barcode ref.
  • Dimensions: leader lines with measurement text; chain dimensions along path.
  • Symbol candidates (Unicode-friendly for HTML/SVG legends, with text fallback):
    • Path node: ● (fallback: "o"); path direction arrow: ➝.
    • Clamp/tie: ⊙ or ⨀ (fallback: "CL"); P-clamp shorthand: [C].
    • Grommet/bulkhead: ◉ (fallback: "GR").
    • Splice (inline dot): •; splice barrel: ▭ with text "SP".
  • Junction block: ▭ with ports; fallback text "JB".
  • Shield to ground: ⏚ (ground) or backshell glyph ⌒; pigtail branch: short line ending ⏚.
  • Covering start/end: ▹ / ◃ markers with hatched segment between.
  • Label flag: ⚑ (fallback: "LBL").
  • Dimension: ↔ with text (e.g., ↔ 250 mm).
  • Icon guidance:
  • Prefer self-drawn SVG primitives (circles, rectangles, arcs, hatch patterns) for clamps, splices, junctions, coverings, labels, and dimensions; avoids font licensing and keeps style consistent.
  • Ground/backshell can be drawn with simple shapes mirroring IPC/WHMA/IEC styles (e.g., ⏚-like ground, arc for backshell).
  • Reference styles (for consistency, not embedding): IPC/WHMA-A-620 nailboard symbols (clamp circles, splice dots/barrels, grommet rings, shield ground at connector). Use them as visual inspiration but render your own SVG.
  • Avoid external icon fonts (Font Awesome/Material) for these domain-specific shapes; they add dependencies and don’t match harness drafting conventions.
  • Information captured:
  • Geometry: 2D coordinates in chosen units; orientation of clamps and splice rotation when relevant.
  • Materials: part numbers for clamps, grommets, splices, protective coverings, backshells/boots.
  • Processes: wrap overlap %, tape turns per unit length, heat-shrink recovery note, torque/strain-relief notes.
  • Electrical tie: map mechanical nodes to connector pins/wires/splices for traceability.
  • Environment: notes for temperature/fluids near segments; routing constraints (min bend radius).

Complexity Score (1–5)

3 — Modeling requires coordinated geometry + materials + annotations but fits within an extended mechanical view without changing electrical core.

Maintenance Risk

  • Symbols and drafting practices are stable (IPC/WHMA-A-620, OEM nailboard guides).
  • Risk lies in scope creep if 3D routing or FEA-style checks are attempted; keeping to 2D with optional CAD reference limits churn.
  • Optional materials catalogs (clamps, wraps) may need periodic refresh.

Industry / Business Usage

  • Automotive: nailboard drawings with clamp spacing, convolute/tape sections, splice barrels, shield terminations to backshells, label flags at breakouts.
  • Aerospace/defense: backshell/boot details, grommets at bulkheads, lacing/tie intervals, shield pigtails or 360° terminations, strain-relief callouts.
  • Heavy equipment/industrial: armored/conduit runs, bulkhead glands, vibration-resistant clamps, inline protection devices.

Who Uses It & Why It Works for Them

  • Manufacturing/QA: needs clamp/grommet placements, coverings, and lengths for board setup.
  • Service: uses labels, splice locations, and shielding notes to troubleshoot/repair.
  • Mechanical/electrical integration: checks pass-throughs, bend radii, and shield terminations against packaging/EMI needs.

Feasibility

  • Feasible with an extended mechanical schema and renderer; symbology can be implemented in SVG/DXF without heavy CAD.

Fit with Existing Filare Models

  • Current fit:
  • Connectors/cables/connections already model electrical nets; additional_components can carry clamps/wraps as BOM-only items but lack geometry/placement.
  • metadata/options can store drawing-level info but not geometry.
  • Graphviz/HTML renderers are logical-only, so mechanical elements are currently unrendered.
  • Gaps: No place for 2D geometry (board outline, paths), feature placement (clamps/grommets/splices), covering intervals, or dimensions. No linkage from mechanical items to nets beyond informal notes.
  • Proposed schema additions (compatible path):
  • Add optional top-level mechanical: block with: units, datum/grid, outline, reference holes; paths with point lists and per-segment metadata; features (clamp/tie/grommet/splice/bulkhead/strain-relief) with positions and part refs; coverings with start/end distances and material refs; annotations for labels/dimensions/notes; shield_terminations to locate style/target.
  • Mechanical items reference existing components via IDs (connector, cable, wire, splice id) to correlate mechanical placement to electrical nets/BOM.
  • BOM linkage: features/coverings carry part refs and qty multipliers (length-based or count-based) similar to additional_components.
  • Alternative implementations:
  • Alt A (inline): Single YAML with mechanical block coexisting with existing connectors/cables; renderers detect and produce extra SVG/DXF plus HTML embed. Easiest for authors (one file), optional and ignore-safe.
  • Alt B (sidecar): Allow mechanical: to accept file refs (include) so large mechanical data can live in a sidecar YAML while core nets stay small. Useful when mechanical data is auto-generated.
  • Alt C (hybrid BOM-only): Keep geometry in an external tool; only attach mechanical part refs as additional_components and hyperlink to an external mechanical drawing. Minimal change but loses render integration.
  • Renderer integration:
  • New mechanical renderer writes SVG (and optional DXF) alongside existing outputs; HTML includes a tab/section for mechanical view.
  • Symbols table/legend added to HTML for user clarity; defaults chosen to match Filare style.
  • User impact:
  • Backward compatibility: existing YAMLs unaffected; mechanical is optional.
  • Authoring complexity: adds coordinate entry and feature definitions; mitigated by templates/examples and optional sidecar flow.
  • Output: users gain mechanical SVG/DXF plus legend; may need to learn symbol mapping but aligns with industry nailboard drawings.

Required Work

  • REWORK tasks: Define mechanical entities (path, feature, protective segment, splice, label, dimension) and their relationships to electrical components.
  • FEATURE tasks: Add rendering support for symbols (clamp/grommet/splice/shield termination/covering/labels) with distance annotations; support path-based dimensions and breakout markers.
  • DOCUMENTATION tasks: Provide a legend of symbols and example mechanical YAML; describe units and datum usage.
  • TOOLS tasks: Optional catalogs for clamps/wraps/splices with default symbols; validators for min bend radius and clamp spacing rules.
  • COVERAGE tasks: Regression YAMLs covering paths with coverings, clamps, splices, shields, labels, and dimensions.

Recommendation

ADOPT_LATER — Define the mechanical model first, then implement 2D rendering and validations incrementally.

Models

  • Geometry Model:
  • Units, datum/grid.
  • Board/outline polygon; reference holes.
  • Path polylines with points, segment metadata (length, bend radius, covering refs).
  • Breakouts: path nodes marking where bundles split; mapping to connector/wire groups.
  • Feature Model:
  • Clamps/ties/edge clips: type, position, orientation, part ref, spacing rule.
  • Grommets/bulkheads: position, opening size, part ref, pass-through link to path.
  • Strain relief/boots/backshells: association to connector end; part refs.
  • Splices/junctions: position, splice type, part ref, involved wires/nets; orientation optional.
  • Covering Model:
  • Segments referencing path intervals with material (conduit, braid, tape, heat-shrink), start/end distances, overlap %, color, part ref.
  • Shield termination: end association, style (backshell/pigtail/isolated), hardware ref.
  • Annotation Model:
  • Labels/markers tied to path positions or features; text, ID, optional barcode ref.
  • Dimensions: chain/ordinate along path, clamp spacing, breakout lengths; tolerance.
  • Notes: process notes (tape turns per unit, shrink temp), environment notes.
  • Correlations:
  • Path nodes ↔ connectors/cables/wires to trace mechanical to electrical.
  • Feature/covering parts ↔ BOM items and to-wire counts (e.g., qty multiplier by terminations or segment length).
  • Shield termination ↔ connector/ground point and BOM backshell/ground hardware.

References

  • IPC/WHMA-A-620 (workmanship and harness drawings)
  • OEM nailboard/fixture drafting guides (automotive, aerospace)
  • Common CAD/CAM nailboard outputs (DXF) used in harness shops

Optional Appendix

  • Symbol legend candidates: polyline path; P-clamp icon; grommet ring; splice dot/barrel; shield ground/backshell glyph; hatched covering; tape/heat-shrink start-end ticks; flag label; chain dimensions along path.