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2.1 Cutting, Stripping & Crimping

Tooling choices, strip quality, and crimp height/pull-force acceptance.

Cutting, stripping, and crimping set the tone for the entire harness build—if these steps are consistent, the rest of assembly flows smoothly. The goal is identical lengths, clean strips with no damaged strands, and crimps that meet both height and pull-force specs every time. Tool choice matters: rotary or thermal strippers for fine or high-temp wire, manufacturer-specified dies and applicators for crimps, and calibrated ratchet tools for low-volume or repair. Visual standards—like correct bellmouth, conductor brush, and insulation support—make inspection quick and reliable. With clear tolerances, first-article checks, and small in-process verifications, crimps become a non-issue in quality reports, and connectors seat with a confident click on every build.

2.1.1 The aim (in one line)

Every lead comes off the bench the same length, the same strip, the same crimp—so connectors seat with a click and never come back.



2.1.2 Tooling overview (pick the right hammer)

Cut/Strip

  • Automatic cut/stripers (bench or inline): fastest, programmable lengths/strips; great for batches.
  • Bench strippers (mechanical/rotary): versatile; rotary is kinder to fine strand.
  • Thermal strippers: for PTFE/FEP and brittle jackets—no nicking, slower cycle.
  • Coax prep tools: multi-step dies that expose braid/dielectric/center length in one squeeze.

Crimp

  • Press + applicator (open-barrel “B-crimp” with insulation support): production standard, controlled crimp height.
  • Hand ratchet crimpers (with locators): for low-mix/repair; must be the manufacturer’s tool/die.
  • Hex/square crimpers: ferrules, closed-barrel terminals, and shields.
  • Coax crimp sets: separate nests for ferrule, shield, center pin—follow the family’s spec.

Golden rules

  • Use the terminal maker’s applicator/die whenever possible.
  • Ratchet tools only; no pliers.
  • Tie tools to cal/verification in your gage program (18.2).

2.1.3 Cutting: length that actually fits

  • Measure along centerline, bare-end to bare-end (state in drawing, 19.2).
  • Post tolerances: e.g., ±5 mm ≤500 mm; then ±1% beyond.
  • Keep blades sharp; dull blades crush insulation → strip problems later.
  • Batch discipline: lot tag each bundle with wire ID, length, strip plan, and WO.

Quick check: pull 5 random pieces onto a go/no-go stick for that length; record if any miss.



2.1.4 Stripping: clean copper, no casualties

  • Strip length per wire table; typical crimp ends want no tinning (stranded wire + crimp likes bare copper).
  • Do not nick strands. Rotary or thermal for fine strand/teflon; mechanical for PVC/XLPE if sharp and set right.
  • Leave a tiny conductor brush (0.2–0.5 mm) beyond the conductor crimp after crimping.
  • Keep insulation debris out of contacts; bench vacuum helps.
  • For twisted pairs: maintain twist up to the terminal unless the spec says otherwise.

Strip defects & causes

  • Nicked/missing strands → jaws set too tight / dull blades → re-set or change blades.
  • Short/long strip → wrong program / measuring from wrong datum → fix strip stop and re-train.
  • Flagging insulation → dull blades / pull-off speed too high → service tool and slow pull.

2.1.5 Crimp setup (make the die do the thinking)

  • Set wire range exactly (e.g., 20–22 AWG); don’t “make” 18 AWG fit.
  • Adjust crimp height to the terminal spec; lock jam nuts/knobs.
  • Set insulation support wings so they capture insulation, not copper.
  • Use the locator so seam sits where the maker intends (no rotated barrels).
  • First-article routine: 10 samples → measure crimp height, pull force, and visuals. Keep them as goldens for the lot.


2.1.6 What “good” looks like (visual cues you can teach in a minute)

  • Conductor crimp: tight barrel, symmetrical “B”, strands fully captured, small front bellmouth, light rear bellmouth.
  • Conductor brush: 0.2–0.5 mm of copper just visible.
  • Insulation support: wings wrap insulation (no piercing into copper), seated flush to barrel.
  • No flares/flags: no stray strands, no split seam.
  • Terminal position: locator marks correct; cavity latch/TPA engages freely.

Post a postcard-sized photo sheet: GOOD / MARGINAL / REJECT.


2.1.7 Acceptance: crimp height & pull-force

Crimp height (CH)

  • Measure with a flat-anvil micrometer across the center of the conductor crimp, perpendicular to the seam.
  • Compare to terminal manufacturer’s spec (preferred). If absent, set your own NOM from first-article and guard-band ±0.03–0.05 mm (light wires tighter, heavy looser).
  • Record CH mean/Cpk by lot if you run volume; adjust press if drift shows.

Pull-force (destructive test)

  • Use the maker’s minimums when available. If not, a starter plant baseline (replace once you have vendor data):

AWG

Min pull (N)

28–30

10–15

26

20

24

30

22

40

20

60

18

80

16

100

Method: pull inline at ~25–50 mm/min until failure. Accept when copper strands fail before the crimp barrel slips (for open-barrel types) and the peak ≥ minimum. Log result.

Note: These are starting points. Always supersede with contact-specific pull values from the manufacturer’s data sheet.


2.1.8 Special cases (so you don’t learn the hard way)

  • Ferrules (square/hex): size ferrule to conductor cross-section, not AWG label; no tinning under ferrules; use square for spring terminals, hex for power lugs.
  • Coax: three crimps—center pin, braid/ferrule, optional strain boot; lengths are critical (use the family’s strip template).
  • High-flex wire (Class 6): rotary or thermal strip; ensure insulation support is gentle (no cutting the jacket).
  • Tin-plated wire: okay; don’t add solder to improve pull—solder wicks and embrittles.


2.1.9 Process control (lightweight but real)

  • Lot start: 10-piece first article (CH + pull + visuals).
  • Hourly (or every reel change): 3-piece CH check + 1 visual.
  • Per 1000 crimps (or at changeover): 3 pulls.
  • Track CH on an I–MR chart (15.5); react to rules, not wiggles.
  • Tie tooling to PM & calibration: die wear and ratchet timing drift show up as CH/pull slips (18.1/18.2).


2.1.10 Common defects → quickest reliable fix

Defect

Why it happens

First fix

Undercrimp (low pull, fat CH)

Height too high / wrong wire size

Lower CH per spec; confirm wire range

Overcrimp (cut strands, barrel cracks)

Height too low

Raise CH; scrap die if seam damage

Strands outside barrel

Short strip / poor insertion

Increase strip length; teach locator use

Insulation in conductor crimp

Over-strip / wire pushed in too far

Reduce strip; set wire stop / locator

No insulation support

Wings mis-set / jacket too small

Re-form wings; ensure correct wire OD range

Nicked strands

Aggressive/mech strip on fine wire

Switch to rotary/thermal; replace blades

Terminal won’t latch/TPA fails

Deformed contact / wrong cavity

Check locator; verify cavity numbering; change a bent contact



2.1.11 Pocket checklists

Before you start

  • Wire ID, length, strip dims from wire table
  • Correct terminal PN and tool/die (with locator)
  • Strip method chosen (rotary/thermal for fine/PTFE)
    Press set to initial CH; insulation support formed

First article (10 pcs)

  • CH within spec (record mean/range)
  • Pull ≥ min; failure in copper, not slip
  • Visuals: bellmouth/brush/insulation support OK
  • Keep samples as goldens; release lot

During run

  • Hourly CH check (3 pcs); trend quiet
  • Swap blades/dies if nicking or CH drift
  • Housekeeping: no copper whiskers in nests

Close/trace

  • Record terminal lot, wire lot, tool/die ID, CH/pull results
  • Tag any rework; isolate suspect batches



Bottom line: cut to a clear datum, strip without harming copper, and crimp with the right die at the right height. Prove it with a quick first article and small, steady checks. When CH sits in a tight band and pulls break wire—not barrels—your crimps disappear from the defect log, and your harnesses click together the same way every time.


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