2.3 Harness Boards & Layout
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2.3.1 What a harness board should do (in one sentence)
Make the right path, length, loops, and labels so obvious that the loom almost builds itself—and does it the same way tomorrow.
2.3.2 Board types (pick to match the job)
Material notes: smooth, stable surface (laminated MDF or phenolic). Use ESD-safe mats in touch areas. Add heat-tolerant zones (aluminum plate) where sleeves or solder sleeves are applied.
2.3.3 What to print on the overlay (1:1 “map”)
- Centerline path (bold) with direction arrows and radius marks.
- Connector callouts with pin-1 triangles, latch orientation, and backshell type.
- Branch points with boot type/length; gauge blocks for service loops (go/no-go).
- Clamp icons with hardware type and spacing (e.g., cushioned P-clamp Ø12, every 250 mm).
- Label locations (distance from backshell) and QR to the From–To table.
- Color lanes: RED = power, BLK = ground, BLU = comms, GRN = shield bond (same legend as Ch. 19).
Scale sanity: add a 100 mm verification bar; every overlay gets checked with calipers before use.
2.3.4 Pins, pegs & locators (make it hard to be wrong)
- Keyed datum holes (A/B) so the overlay only mounts one way.
- Zero-point connector nests (3D-printed or machined) that set angle/clocking and strain relief before first bend.
- Adjustable loop gauges (sliding stops) with engraved target ± tolerance (e.g., 80 ±10 mm).
- Rounded pins (no burrs), sleeved where jacket rubs; never force sharp 90° turns.
- Shield bond stations: metal ear + 360° clamp nest right at the chassis entry point.
2.3.5 Layout rules that speed hands (and save jackets)
- First clamp before first bend (50–80 mm from backshell).
- Min radius printed along tight arcs (6×OD static / 10×OD dynamic).
- Stagger splices ≥30 mm; never place splices at bends.
- Straight runs long enough to install boots/heat-shrink without scorching nearby wires (add heat box zones).
- Cable crossing minimized; where needed, cross at 90° and label the layering order on the overlay.
2.3.6 Ergonomics (takt lives here)
- Board height/tilt adjustable; work in the elbows-down zone.
- Left–right symmetry if two techs build together; parts bins on both sides.
- Lighting bright and diffuse; no glare on clear heat-shrink.
- Tool shadows: crimp tool with die ID, hot-air nozzle, scissors, lacing—each returns to a labeled spot.
- Waste chutes for wire offcuts and sleeve skeletons; keep the board clean.
20.3.7 One-off vs volume: how to blend without chaos
Start one-off:
- Pegboard, paper overlay, painter’s tape notes. Log loop lengths, clamp positions, and gotchas directly on the print.
Freeze to volume:
- Convert notes into a rev-controlled overlay; replace tape with printed callouts.
- Swap movable pegs for keyed fixtures and loop gauges.
- Create a module lane: pigtails, branch whips, shield straps (19.5) prebuilt and tested queue to the board.
Family boards:
- Same datum holes and clamp rail across variants; use option markers (A/B/C) and Do-Not-Stuff labels to keep a single overlay.
2.3.8 Integrated aids (make the board do the thinking)
- Centerline ruler every 100 mm for quick cut checks.
- Photo boxes: “What good looks like” for each branch/boot.
- Sleeve lengths printed near stations (before-shrink size).
- Pin-test docks (pogo or break-out headers) for subassembly continuity before loom-up.
- Heat-proof nests sized to each solder sleeve; stencil “heat here.”
2.3.9 Revision control & storage (no zombie boards)
- Overlay shows Harness PN–Rev, effectivity, change bar; QR to drawing pack.
- Red tag obsolete boards; store vertical in a rack by family; dust covers on high-use fixtures.
- Pre-flight check card on each board: overlay rev, tools present, gauges set—signed at start of shift.
2.3.10 Capacity planning with boards (simple math)
- Takt target: Available time / Required units.
- Build time per board from last three lots.
- Boards needed = ceil(Build time / Takt).
- If >1, split flow: parallel boards or module kitting to keep the main board busy. Track FPY and minutes waiting for modules.
2.3.11 Pitfalls → smallest reliable fix
2.3.12 Pocket checklists
Designing a board
- 1:1 centerline with min radius and direction arrows
- Connector nests keyed; pin-1 and latch shown
- Loop gauges with target ± tol; clamp icons placed
- Label positions, sleeve lengths, shield bond station
- Overlay rev, PN, QR; 100 mm scale bar
Before first build
- Overlay scale verified; pegs/nests fit; heat zones safe
- Tool shadows stocked; ESD mat where hands live
- Module lane ready (pigtails, branches pre-tested)
Daily use
- Pre-flight card signed; gauges set; correct rev
- Clean board; bins stocked; waste emptied
- First article passes loop gauges and continuity
After run
- Capture kaizen: one change to overlay/fixtures
- Store board vertical; cover on; red-tag any damage