Review of Part 1:
In [DFM Production Feasibility Analysis (Part 1): From Drawing Review to Material Selection], we completed drawing review and material selection. This part continues with the manufacturing-side DFM: processes, tooling, quality systems, and self-assessment checklists.
III. Process Evaluation
Different wire harness structures correspond to different manufacturing processes. The core of DFM is not choosing the "most advanced process," but selecting the process that matches the product structure, materials, and application scenario.
Application Requirements
Recommended Process Solutions
Process Selection Rationale & Advantages
Design Evaluation Focus
General electrical connections requiring stable reliability and suitability for mass production
Terminal Crimping
The most mature wire harness connection method, forming a stable electrical connection through mechanical compression between the terminal and conductor; high production efficiency, controllable cost, easy maintenance and replacement
Terminal-to-wire gauge matching, Crimp Height (CCH) control, conductor fill rate, pull force testing, and cross-section analysis verification
Multi-conductor splicing, large cross-section connections requiring low resistance and high reliability
Ultrasonic Welding
Uses high-frequency vibration to achieve molecular-level bonding of metals, eliminating the need for traditional terminals, reducing connection resistance and saving space; ideal for high-current, high-vibration environments
Conductor material compatibility, welding energy, amplitude, pressure parameters, weld zone dimensions, contact resistance, and mechanical strength verification
High-current, high-load connections requiring long-term stable current-carrying capacity
Resistance Welding / Hot Bar Welding
Uses localized thermal energy to form a permanent connection, reducing contact interfaces and improving current-carrying capacity and long-term reliability
Welding current and time control, heat-affected zone management, temperature rise testing, and cycle life verification
Connections requiring waterproofing, dustproofing, and pull-out protection
Low Pressure Molding
Uses low-pressure hot-melt materials to encapsulate the connection area, enhancing sealing and mechanical strength while protecting internal structures
Material flow characteristics, material compatibility, encapsulation thickness, gate and vent design, and sealing reliability verification
Long-term water exposure, high-humidity, high-ingress-protection-rating requirements
Potting / Coating
Fills internal spaces with sealing materials to create a monolithic protective barrier, improving waterproofing, moisture resistance, and corrosion resistance
Material shrinkage rate, curing stress, thermal expansion matching, and compatibility between potting material and wire harness materials
Space-constrained applications requiring lightweight and miniaturized design
Connection Structure Optimization
Reduces volume and weight through optimized connection methods, materials, and layout, improving installation convenience
Wire gauge optimization, connector selection, routing layout, and assembly space analysis
IV. Molds and Fixtures
Molds and fixtures are often an overlooked aspect in DFM, yet they directly impact production efficiency. Before formal mass production, the following need to be confirmed in advance:
Molds
Fixtures
Whether the crimping mold matches terminal specifications; whether the injection mold structure is suitable for product demolding; whether the mold requires sliders, inserts, or other complex structures; whether mold life meets the expected production volume; and whether subsequent changeover and maintenance costs are acceptable
Crimping positioning fixtures; welding fixtures; injection molding positioning fixtures; assembly fixtures; testing fixtures; mistake-proofing fixtures
Once mold requirements and design have been confirmed, how long does it typically take from mold design to manufacturing completion? This depends on the specific product structure and mold complexity — it is recommended to confirm lead times with mold suppliers during the DFM review phase.
IV. Process Safeguards
For DFM to be effective, a single report is far from sufficient. It must be embedded within a rigorous engineering quality management system and validated through physical verification. We embed the review within the automotive-industry APQP methodology framework, forming a three-tier integration.
4.2 Seamless NPI Integration — Validating Truth in 24–72 Hours
No matter how perfect the paper-based conclusions of a DFM may be, they ultimately must be validated with physical products. Kaweei uses an independent NPI (New Product Introduction) process to quickly take over, completing first-article physical validation within 24–72 hours, transforming design-phase assessments into tangible, testable, and deliverable samples.
V. Tool Kit — Wire Harness DFM Quick Self-Assessment Checklist
Before entering the formal DFM review, you can use the checklist below for a quick self-assessment to screen out some common issues in advance:
Wire & Conductors
Conductor construction: Are you choosing stranded, solid, or flexible conductors? For cable carriers, robotic joints, rotary tables, and similar applications, prioritize evaluating more flex-resistant stranded/flexible conductors. For fixed wiring inside control cabinets, prioritize solid conductors with high conductivity stability and good structural rigidity.
Conductor material: Bare copper / tinned copper (general environments); silver-plated copper (high-temperature environments ≥200°C, high-frequency signal transmission, low loss); nickel-plated copper (extreme high-temperature environments ≥250°C, good stability); copper alloys (cost-sensitive, weight-reduction needs, RF/coaxial cables).
Flexible bending radius standards: Static installation ≥6–10× cable OD (standard cables), high-flex cables ≥4–5× OD; dynamic bending ≥10–15× cable OD (standard flexible cables), high-flex continuous-flex cables ≥7.5–10× OD.
Insulation materials: PVC / XLPE / Teflon (PTFE/FEP/PFA) / TPU / LSZH / silicone — verify compatibility with rated temperature, voltage rating, flammability requirements (e.g., UL94 V-0), and chemical environment.
Temperature rating covers maximum operating temperature: Select appropriate temperature ratings based on harness installation location, distance from heat sources, and ambient temperature. Standard engine compartment areas typically require -40°C to +125°C; areas near heat sources require -40°C to +150°C; extreme high-temperature areas such as exhaust manifolds and turbochargers require ≥200°C high-temperature wire and protective structures.
Cable certifications completeness: UL, flammability rating (UL 1581 VW-1/FT-1), RoHS/REACH, CE, VDE, etc.
Terminals & Connectors
Terminal wire range compatibility: Verify the wire gauge range specified in the terminal datasheet.
Terminal has corresponding crimping tooling: For non-standard terminals, confirm tooling availability and lead time.
Connector position count and polarization points indicated: Pin positions, color-coding for error-proofing, and secondary locking (CPA/TPA) requirements should be clearly noted.
Vibration-resistant terminal selection for high-vibration applications: Choose terminals with retention features (e.g., TPA / secondary locking) and connectors with latching/locking mechanisms; for automotive-grade vibration environments, prioritize terminals/connectors that meet USCAR standards.
High-current circuits need current-carrying margin verification: Ensure terminal temperature rise matches wire gauge current-carrying capacity.
Shield termination method: For high EMC requirements, prioritize 360° circumferential crimp (shield ring / shield clamp); the "trim + heat shrink" (pigtail/drain wire) method is not recommended for high-frequency / high-EMC applications but may be used for low-frequency or non-critical signals.
Mating cycle life verification: For serviceable interfaces, confirm that the mating cycle rating meets the equipment's lifecycle requirements.
Structure & Assembly
Branch positions and length tolerances reasonable: Branch points should avoid bend zones; length tolerances must fall within process capability range (e.g., for a finished length of 10m, tolerance should be at least ±20mm); branch points should have transitional protection structures.
Multi-core harness strain relief: Inner cores should not be "flush" — the center core should be shortest, with outer cores progressively longer to create a stepped length difference. This ensures each core experiences even strain during bending, preventing outer cores from snapping and inner cores from bunching up.
Waterproof seal compression ratio: Seal compression ratio 15%–30% (for rubber seals), verifying both ends — the compression ratio at both the wire end and the housing end must fall within the specification range; Compression Ratio = (Original Seal Cross-Section Diameter − Compressed Height) / Original Cross-Section Diameter × 100%.
Labeling scheme defined: Label positions readable; printing method or label material meets abrasion/solvent/temperature resistance requirements; content includes traceability information; label thickness should not interfere with assembly.
Assembly sequence feasible: All sequential parts have been checked — ensure that parts that must be "threaded before crimping" (waterproof plugs, seals, sleeves, heat-shrink tubing, shield rings, etc.) are not omitted (one of the most frequent low-level errors in reviews); simulate the entire assembly process to confirm every step can be assembled.
Serviceability considered: Connectors can be mated/unmated by hand or with tools; clear assembly/disassembly markings should be provided.
Testing & Supply Chain
Test requirements specified: 100% continuity testing, withstand voltage values, insulation resistance values, pull force requirements, etc.
Critical material lead times: For long-lead-time materials (>8 weeks), initiate alternative evaluation.
EOL risks screened: Confirm no end-of-life warnings for connectors, cables, or other materials.
Environmental compliance confirmed: RoHS / REACH / halogen-free compliance certificates obtained.
VI. Conclusion — The Best Time for DFM Is Before the Drawing Is Finalized
Why doesn't a perfect drawing always yield a perfect wire harness? Because the drawing defines "what it should be," while DFM addresses "how to manufacture it in the real world, and whether it can withstand real-world conditions."
In the field of industrial custom wire harnesses, Kaweei's positioning has never been that of a "contract manufacturer" — we are a Full-Stack Engineering & Adaptability partner, deeply covering five core sectors: industrial automation, automotive, robotics, telecommunications, and waterproofing:
We don't just build to print — we engage at the drawing stage, using DFM to help customers get the design right from the start
We don't just provide wire harness products — we deliver end-to-end engineering capabilities from material solutions, process selection, and tooling design to NPI validation
Our DFM is not a one-time review service — it is a continuous engineering output based on the APQP/PPAP framework, DFMEA/PFMEA methodology, and thousands of mass-production project experiences across dozens of industries
