Every wire harness — from a two-lead jumper to a kilometer-scale vehicle loom — moves through a production flow whose steps determine its quality. Buyers who understand the flow know what they're paying for, where failures originate, and what questions to ask suppliers. This guide walks the flow, step by step.
Step 1: Wire Cutting and Stripping
Automatic cut-strip machines feed from wire spools, cutting to length (programmed per the wire list) and stripping insulation at both ends. The quality points: cut length tolerance (harness geometry depends on it), strip length precision, and — the critical one — no nicked conductors (blade depth set per wire gauge; a nicked strand becomes the fatigue fracture site). Modern machines verify strip quality optically; the step looks trivial and isn't.
Step 2: Terminal Crimping
Stripped wires get terminals crimped — the process that determines most harness reliability. Quality practice: calibrated applicators (crimp height set per terminal-wire combination, verified by cross-section analysis), crimp force monitoring (every crimp's force curve recorded; out-of-window crimps rejected automatically — our crimp quality guide covers why the curve is the evidence), and pull-test sampling (mechanical verification). This step's discipline is the single best predictor of supplier quality — ask to see the monitoring data.
Step 3: Sub-Assembly and Connector Insertion
Crimped wires assemble into sub-groups, and contacts insert into connector housings (with audible/verified lock engagement), seals where the class requires, and secondary locks where the connector provides them. Quality points: correct cavity per the pin map (the drawing's moment of truth), full seating (partial insertion is the classic hidden defect — verified visually or by fixture), and seal placement on waterproof classes.
Step 4: Harness Forming on the Board
Sub-assemblies lay onto a forming board — a full-scale layout of the harness's geometry with pegs and branches — where the routing takes its final shape: branches positioned, lengths confirmed, clips and grommets added, protection applied progressively. The board is the geometry's enforcement: batch consistency comes from the board, and fitment in the customer's equipment is decided here.
Step 5: Taping, Sleeving and Protection
The formed bundle gets its protection: taping (spot or full per spec), convolute or conduit where abrasion demands, heat shrink at joints (fully shrunk — our tubing guide covers the practice), braiding where the spec calls it. This step is labor-intensive and spec-critical: protection placement is exactly what survives the application environment.
Step 6: Electrical Testing
100% electrical test on every harness: continuity and wiring against the pin map (automated testers execute in seconds), hipot where the class requires (power and HV circuits), insulation resistance for HV, shield continuity where specified. Results recorded per serial where traceability requires. The 100% principle admits no sampling: a harness that wasn't tested isn't a finished harness.
Step 7: Inspection and Packing
Final visual inspection (workmanship, labels, completeness against the kit list), documentation attached where the program requires (test records, certificates), and packing that protects the geometry (coiled, boxed or formed per the harness's tolerance for storage stress). Packing sounds trivial; a harness shipped kinked arrives kinked.
The Flow's System Property
Each step's quality is visible in the final product: nicked wires from Step 1 fracture in the field, marginal crimps from Step 2 heat in service, partial seating from Step 3 fails at power-on. The flow is a chain — and supplier evaluation is asking which links have monitoring, and whether the data exists. Our manufacturing capabilities guide shows our flow's instrumentation.
Kaweei's Production Flow
Kaweei runs this flow with automation and monitoring at every measurable point — auto cut-strip-crimp with force monitoring, board forming, 100% networked test, documented packing — from our Dongguan facility. Contact our engineering team to see the flow applied to your drawing; our DFM guide covers how designs enter it cleanly.