Capability / Cable, harness and electro-mechanical
A harness is the part of a build that is most often tested by hand and least often documented, which is why cable faults show up as intermittent field returns rather than as line failures. We build to a released wire list, prove every crimp with a pull test, and verify continuity against the drawing before the assembly leaves the bench.
How a harness is built
Each harness gets a routing board with the breakouts, bend radii and tie positions pinned out at full scale, built from the released drawing rather than from a sample. Wire is cut and stripped to the lengths on the wire list with a tolerance of plus or minus 2 mm on a breakout and plus or minus 5 mm on a run, and the strip length is held between 3.0 and 6.0 mm so the insulation sits inside the crimp barrel without entering the contact area. Every wire end carries its circuit identity until the label is fitted.
A crimp is accepted on three observations: the conductor is visible in the wire barrel with no severed strands, the insulation support grips the insulation without cutting it, and the bell-mouth is present at the brush or ribbon end. Where the class requires it we measure crimp height with a micrometer against the contact manufacturer's specification and pull three samples to the IPC/WHMA-A-620F tensile minimum for that gauge. The applicator is set once per job and the setting is recorded, so a re-run of the same part number crimps to the same height.
Harnesses that become part of a box build are dressed into the enclosure on the same routing discipline, with sleeving and grommets at every panel pass-through and a service loop left where a connector has to move. Fasteners are torqued into a logged band of 0.4 to 4.0 newton-metres, strain relief is verified by hand before the cover goes on, and the finished unit runs a system-level functional test so a mis-pinned connector is caught in the cell rather than at the customer site.
Capability table
Twelve rows covering the wire range we build, the termination methods available, the tensile minimum applied to each gauge band and the workmanship class that governs the call.
| Item | Capability | Acceptance criteria | Standard and class |
|---|---|---|---|
| Discrete wire range | AWG 30 to AWG 8 in PVC, PTFE and silicone insulation | Strip length 3.0-6.0 mm, no nicked or severed strands, no insulation pull-back into the barrel | IPC/WHMA-A-620F Class 2 |
| Fine gauge and micro-coax | AWG 32-28 wire and 0.8-2.0 mm coaxial cable | Clean strip, shield braid dressed without strand loss, dielectric undamaged | IPC/WHMA-A-620F Class 3 |
| Open-barrel hand crimp | AWG 26-14 for low volume, repair and field kits | Conductor visible in the barrel, insulation support closed, bell-mouth present, tool calibration logged | IPC/WHMA-A-620F Class 2 |
| Bench-press applicator crimp | AWG 28-10 at production volume, with a cut-and-strip machine feeding the press | Crimp height measured per setup, then verified every shift against the contact specification | IPC/WHMA-A-620F Class 2 and Class 3 |
| Four-indent crimp | AWG 26-12 on military and aerospace contacts | Indent depth and position per the contact manufacturer, no deformation of the contact body | IPC/WHMA-A-620F Class 3 |
| Pull test, AWG 28-26 | Minimum hold before separation | 15-22 N applied axially at 25 mm per minute | IPC/WHMA-A-620F tensile table |
| Pull test, AWG 24-22 | Minimum hold before separation | 22-40 N applied axially at 25 mm per minute | IPC/WHMA-A-620F tensile table |
| Pull test, AWG 20-18 | Minimum hold before separation | 55-90 N applied axially at 25 mm per minute | IPC/WHMA-A-620F tensile table |
| Pull test, AWG 16-14 | Minimum hold before separation | 130-220 N applied axially at 25 mm per minute | IPC/WHMA-A-620F tensile table |
| Pull test, AWG 12-10 | Minimum hold before separation | 260-400 N applied axially at 25 mm per minute | IPC/WHMA-A-620F tensile table |
| Solder termination | AWG 30-16 on cup, hook and turret terminals, plus splice joints | 75% minimum circumferential wicking on the barrel, no insulation damage, no cold joint | J-STD-001 Class 2 and Class 3 |
| IDC and ribbon cable | 0.635 mm pitch ribbon and 1.27 mm insulation displacement connectors | Full insertion with the strain-relief cover latched, no displaced conductor and no partially pierced strand | IPC/WHMA-A-620F Class 2 |
Harness services
Six scopes cover the work we are asked for. Each one is quoted with its own verification step, so a harness never ships on a visual check alone.
SVC-01 / Design support
The drawing is checked for missing branch lengths, connector position numbering, circuit identity on every wire end and a bend radius the cable can actually take. Where the drawing is silent, we say which dimensions are missing instead of filling them in from a similar job.
SVC-02 / Preparation
Automated cut-and-strip for AWG 30 to AWG 12 with the strip length held between 3.0 and 6.0 mm, and hand stripping with a calibrated tool for the heavier gauges. Tinning is applied only where the termination calls for it, because a tinned conductor under a crimp barrel changes the cold-flow behaviour of the joint.
SVC-03 / Termination
Open-barrel, closed-barrel and four-indent crimps on hand tools and bench presses, with crimp height measured against the contact manufacturer's specification. Three samples are pulled at every setup and then every 500 crimps, and the pull values are recorded against the harness serial.
SVC-04 / Ribbon and coax
Mass-terminated ribbon on 0.635 mm and 1.27 mm pitch with the strain-relief cover latched, plus micro-coax down to 0.8 mm with the shield dressed and the dielectric left undamaged. Coaxial assemblies are checked for continuity on the centre conductor and for isolation between the centre and the shield.
SVC-05 / Protection
Heat-shrink breakouts, braided sleeving, grommets at every panel pass-through and low-pressure overmoulding where the application needs a sealed transition. Strain relief is verified by hand at the moulded end and at the connector, and a service loop is left wherever a connector has to move during assembly.
SVC-06 / Verification
Every harness runs continuity against the wire list on an automated tester, which catches a crossed pair or an open branch that a visual check cannot see. Hipot is applied where the specification calls for it, pull-test values are logged, and the record set travels with the harness serial rather than staying in the cell.
Macro record
A cross-section is the only way to see whether the strands are compacted inside the barrel or sitting loose beside each other, and it is the check we run when a pull test passes but the joint still worries us.
Buyer questions
The minimum tensile value follows the gauge: roughly 15 to 22 newtons for AWG 28 to 26, 22 to 40 newtons for AWG 24 to 22, 55 to 90 newtons for AWG 20 to 18, 130 to 220 newtons for AWG 16 to 14, and 260 to 400 newtons for AWG 12 to 10, taken from the IPC/WHMA-A-620F tensile tables for the contact type in use. We pull three samples at every crimp setup and then every 500 crimps against that minimum, and the pull values are recorded against the harness serial rather than summarised per shift.
Yes. A harness is built from a released drawing that carries the wire list, the gauge and colour for each circuit, the cut lengths with their tolerances, the connector position numbers, the branch lengths and the label scheme. The first article is submitted with a pull-test record, a continuity result against the wire list, a dimensional check on the branch lengths and photographs of the finished assembly. Where the drawing is incomplete we say which dimensions are missing rather than filling them in from a previous job.
That is the normal case on an electro-mechanical programme, and it is where most harness defects are found early. The harness is built and tested on its own, then dressed into the enclosure on the routing board or into the assembly fixture, with the bend radii and the tie positions checked against the drawing. Fasteners are torqued into the logged band of 0.4 to 4.0 newton-metres, and the finished assembly goes through a system-level functional test and a hipot where the specification calls for one.
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