1.2 Drawings, BOM & Wire Tables
In cable harness manufacturing, documentation is as critical as the design itself. A harness only performs as intended if every detail—wire size, connector orientation, strip length, and label placement—is communicated without ambiguity. Drawings, bills of materials, and wire tables serve as the common language between engineering, production, and quality teams, ensuring that builds are consistent, testable, and free from interpretation errors. When all documents align, the result is a harness that can be built right the first time, even by someone new to the product.
1.2.1 What a “good harness doc set” looks like
- One glance, one truth. Drawing + BOM + wire table agree. No “see note on page X” surprises.
Buildable without tribal knowledge. Crimp tools, strip lengths, and cavity IDs are explicit. - Checkable. A tester can verify pin-to-pin from the From–To table without guessing colors.
- Releasable. Proper title block, revision, effectivity, and change bars.
Minimum packet: Assembly drawing + BOM + Wire (or Core) Table + From–To/Pin map + Notes & tolerances.
1.2.2 Assembly drawing (the map)
Content (must-have):
- Overall harness view with callouts (balloons) keyed to BOM items.
- Connector detail boxes (J1, J2, P1…) showing keying, clocking, pin numbering, shield/360° bond and backshell style.
- Breakouts for splices, boots, labels, and heat-shrink with dimensions from datum (e.g., “Label L1: 45 ±5 mm from J1 backshell”).
- Route length and measure line (measure along centerline, not straight-line).
- Title block: harness PN/description, rev, sheet, units, scale, page zones, approvals, effectivity/variants.
- Notes: default tolerances, inspection/test, crimp acceptance, marking conventions (19.2.6).
Conventions:
- Use J for jacks/receptacles on the product side, P for plugs/cable-side (or your house style—just be consistent).
- Show pin-1 triangle and shell ground symbol where applicable.
- If using multicore cable, draw the outer cable and call the core ID schedule in the wire table.
1.2.3 BOM (everything you touch, by PN)
Include every purchased or consumed item per harness: connectors, contacts, seals, backshells, boots, heat-shrink, splices, lacing tape, braid/sleeve, clamps/grommets, labels, ferrules, markers, cable ties, adhesive, and multicore cable or discrete wire.
BOM columns (suggested):
Tips:
- Contacts are separate line items (socket vs pin).
- Backshells/seals called out by thread/angle and material (EMI 360° vs plain).
- Variant column: mark “A only,” “B only,” or “A/B.”
1.2.4 Wire (or Core) Table — the build recipe
This is where ambiguity dies. One row per wire (for discrete) or per core (for multicore).
Notes:
- Wire ID appears on labels/tags and in the From–To table.
- Std Class = strand flexibility (e.g., IEC 60228 Class 5/6).
- Cut length measured bare end to bare end (before terminals).
- Strip lengths per end; include tin/no-tin note if needed.
- Term PNs are the contact or ferrule part numbers, not just the connector body.
- For multicore, put Core 1…n (color/number) and the same end/cavity mapping.
1.2.5 From–To / Pin Map — what test uses
Make a table a tester tech can wire up from, without colors.
Add test limits here or in notes (continuity Ω max, hipot level, insulation resistance, if applicable).
1.2.6 Standards, codes & naming (be consistent)
Color abbreviations (house set): BK (Black), RD (Red), WH (White), BU (Blue), GN (Green), YE (Yellow), GY (Gray), BN (Brown), VT (Violet), OG (Orange).
Connector callouts: J1/P1 plus Cavity numbers exactly as the manufacturer numbers them.
Wire IDs: W01…Wnn or functional (e.g., “V_MOTOR”). Pick one scheme.
Dimensions: mm as default (state units in title block).
Default tolerances (example—adjust to policy):
- Cut length: ± 5 mm ≤ 500 mm; ± 1% beyond.
- Strip length: ± 0.5 mm.
- Label position: ± 5 mm from datum.
- Overall harness length: ± 10 mm measured along centerline.
Marking: label content = Harness PN–Rev, WO/Date, optional SN (if unit-level traceability). Orientation arrow shown on drawing.
1.2.7 Notes that save builds (put on the drawing)
- Crimp acceptance: “Crimps per Mfr Spec; pull test per table ___.”
- Shield term: “Provide 360° termination at J1 using backshell PN ___; heat-shrink boot PN ___.”
- Heat-shrink cuts: lengths/tubing sizes before recover; color (usually BLK).
- Lacing/Tie: “Lace with waxed polyester every 150 mm; no ties over labels.”
- Bend radius: “No bends tighter than 6× OD unless otherwise noted.”
- Cleanliness: “No flux or adhesive residue; wipe with IPA where applicable.”
- Inspection/test: continuity, hipot (if required), label legibility, orientation check.
1.2.8 Variants & options (keep one drawing if you can)
Use build tables or option flags:
- Option columns (A/B/C) in the BOM and wire table with ✔ marks.
- Do-not-stuff clearly stated (e.g., “Variant B: omit W05, cap J2 Cav 7”).
- Show unique labels or color changes per variant if required by customer spec.
1.2.9 Revision control & effectivity
- Rev letters in title block; change bars on affected zones; concise ECN note on the sheet.
- Effectivity: “Applies from WO ##### onward” or serial range.
- Superseded drawings watermarked OBSOLETE in the vault; floor copies purged.
1.2.10 Common traps → smallest reliable fix
1.2.11 Pocket checklists
- Assembly view with balloons; connector details with pin numbering
- BOM complete (bodies, contacts, backshells, boots, splices, labels)
- Wire/Core table filled (IDs, colors, gauge, cut/strip, ends, tools)
- From–To/Pin map matches table; test limits noted
- Notes/tolerances posted; units and measurement method clear
Review
- Peer build review: print the From–To and walk a sample connector
- Sample pull/strip/crimp done once to validate strip lengths/tools
- Variant flags checked; labels previewed
Release
- Rev + change bar; effectivity set; PDFs sealed
- MES/buy lists updated from the same data (no retyping)
- Obsolete sheets removed from floor; traveler updated