Explanation of Wire Harness Production Process

I. Wire Cutting: Precise Length Determination, the Perfect Start

Wire cutting is the first step in wire harness production, and its accuracy directly affects the quality of all subsequent processes.

1.1 Preparation

• Equipment inspection: Confirm that the automatic wire cutting machine operates normally, with no abnormal noise or vibration

• Blade inspection: Ensure cutting blades are sharp with no nicks, and the blade edge is flat and undamaged

• Workbench cleaning: Remove debris, ensuring no leftover wire scraps or oil stains from previous production

• ESD protection: For sensitive wires, confirm that electrostatic discharge protection measures are in place

1.2 Setup and Cutting Operation

• Drawing confirmation: Carefully review engineering drawings or work instructions to confirm wire specifications (type, AWG, color, insulation material)

• Equipment setup: Set cutting length, stripping length (if required), wire feeding speed, and other parameters according to wire specifications

• First article inspection: Test cut 3-5 pieces, measure dimensions with calipers or steel rulers, confirm within tolerance range

• Mass production: Beginbatch cutting only after first article passes inspection

1.3 Key Technical Requirements

1.4 Common Cutting Defects and Prevention

Defect Type	Cause	Prevention Measures
Length Out of Tolerance	Slipping feed wheel, incorrect parameter settings	Clean feed wheels regularly, mandatory first article inspection
Angled Cut	Worn blades, improper installation	Replace blades regularly, check blade installation
Insulation Scratch	Burrs in feed channel, excessive tension	Clean feed channel, adjust tension

II. Grommet Installation: Fundamental Protection, Attention to Detail

Grommets protect wire harness branch points or terminal roots, preventing mechanical damage and stress concentration.

2.1 Operation Steps

• Confirm grommet specification: Select the correct grommet type according to drawing requirements

• Insertion direction: Insert the end of the wire that will receive a terminal through the grommet, ensuring the small end (or specified direction) faces downward as shown in the drawing

• Pre-positioning: Temporarily position the grommet on the wire at an appropriate location; final position will be adjusted after terminal crimping

2.2 Quality Control Points

• Correct grommet specification, no cracks or deformation

• Correct insertion direction, no reverse installation

• Grommet remains in position without shifting or falling off during subsequent processes

III. Wire Stripping: Precise Removal, Undamaged Conductors

Wire stripping removes the insulation from the wire end, exposing the metal conductor for terminal crimping.

3.1 Preparation

• Inspect stripper condition: Confirm equipment operates normally, blades are sharp and undamaged

• Clean workbench: Ensure no debris to avoid contaminating wire conductors

3.2 Setup and Operation

• Parameter setting: Set stripping length and blade depth according to wire specifications (diameter, insulation thickness)

• First article test: Test strip 3-5 pieces, check stripping length and conductor condition

• Mass production: Begin batch production only after first article passes inspection

3.3 Stripping Length Reference
Stripping length is generally determined by the terminal crimp barrel length, with common calculation formulas:

• Conductor cross-section ≤ 1mm²: Stripping length = Crimp barrel length + 1mm

• Conductor cross-section 1-10mm²: Stripping length = Crimp barrel length + 2mm

• Conductor cross-section ≥ 10mm²: Stripping length = Crimp barrel length + 2-3mm

3.4 Key Technical Requirements

3.5 Common Stripping Defects and Solutions

Defect Type	Cause	Corrective Action
Broken Strands	Blade cutting too deep	Adjust blade depth, retest
Residual Insulation	Blade cutting too shallow	Adjust blade depth, retest
Stripping Length Out of Tolerance	Improper positioning	Reset parameters, verify with first article
Oxidized/Discolored Conductors	Contaminated blades, improper wire storage	Replace blades, check material storage

IV. Terminal Crimping: Core Process, Quality Lifeline

Terminal crimping is the critical process that forms a permanent connection between the wire and terminal through mechanical pressure, directly determining the wire harness electrical performance and mechanical strength.

4.1 Preparation

• Equipment inspection: Confirm crimping machine operates normally, air pressure stable (for pneumatic equipment)

• Die inspection: Confirm crimping dies match the terminal type, with no wear or damage

• Workbench cleaning: Remove debris, prepare collection containers

4.2 Setup Operation

• Professional technicians install and adjust dies, set crimp height or crimp force parameters

• Test crimp 3-5 pieces for first article inspection:

• Visual inspection of crimp appearance

• Measure crimp height (using micrometer)

• Perform pull force test (if required)

• Mass production begins only after first article passes inspection

4.3 Terminal Fundamentals

4.4 Key Technical Requirements

Control Item	Standard Requirement	Inspection Method
Crimp Height	Within terminal specification tolerance (typically ±0.05-0.1mm)	Measure with micrometer
Crimp Appearance	No over-crimping, under-crimping, wire strands fly off, terminal deformation, crimp cracks	Visual inspection, 20x magnifying glass
Bell Mouth	Appropriate bell mouth at crimp barrel entrance and exit	Visual inspection
Conductor Position	Conductors fully inside crimp barrel, visible at front end	Visual inspection
Insulation Position	Insulation located in insulation crimp area, properly compressed but not pierced	Visual inspection
Pull Force	Meets industry standards (e.g., LV214, USCAR) or customer requirements	Pull tester measurement

4.5 Crimp Defect Reference

4.6 Safety Precautions

• Never place hands in the die area during operation technician

• For two-hand operated equipment, both buttons must be pressed simultaneously

• Do not clean scrap or adjust dies while equipment is running

• Stop immediately if abnormality is detected and report to

V. Connector Assembly: Precise Positioning, Reliable Locking

Insert the crimped terminals into the corresponding connector housings according to drawing requirements.

5.1 Operation Steps

• Confirm connector housing type: Select the correct connector housing according to drawing

• Check terminal locking mechanism: Confirm terminal barbs are intact

• Insert wire: Align the crimped terminal with the corresponding cavity in the housing, push in with even force

• Verify locking: Listen for a "click" or feel the lock, gently pull the wire to confirm it does not pull out

5.2 Key Technical Requirements

VI. Electrical Testing: Functional Verification, Quality Assurance

Electrical testing is the final defense ensuring wire harness functionality and the most critical part of wire harness testing.

6.1 Test Purpose

• Verify circuit continuity: Confirm every line conducts correctly

• Detect shorts: Confirm no unintended conduction between adjacent circuits

• Verify insulation performance: Test insulation resistance and dielectric strength

6.2 Test Equipment

6.3 Test Steps

1. Fixture connection: Properly connect the special use test fixture to the tester, secure to workbench with fixture clamp

2. Equipment self-check: Test with a known defective sample to confirm tester and fixture working properly

3. Product testing: Insert the test harness connectors into corresponding fixture sockets

4. Result judgment:   
   

• Observe tester indicator lights (typically green light indicates pass, red light or buzzer indicates fail)

• Or read test results displayed on tester screen

   5.Remove product: After testing, pull connector out parallel (do not pull at an angle)

6.4 Test Standards

Test Item	Acceptance Criteria	Notes
Continuity Test	All Line conduction resistance less than set value (typically <1-5Ω)	Adjust based on length and wire gauge
Short Test	Resistance between adjacent circuits greater than set value (typically >10-100MΩ)	Ensure no shorts
Insulation Resistance	Resistance between wire-wire, wire-shield >100MΩ (500V DC)	Per customer requirements
Hi-Pot Test	Leakage current <5mA at specified voltage (e.g., 500-1500V AC/DC)	Per safety standards

6.5 Precautions

• After testing, self-check housing for scratches, terminals for skewing

• If continuation electrical test failures occur, stop immediately and report to supervisor or QC

• Strictly separate good and defective products, label clearly, place defective products in designated red area

• Test probes are wear parts; replace every 3,000 insertions or as needed based on actual condition

• Record and archive test data for quality traceability

VII. Harness Assembly: Integration into Finished Product, Neat and Organized

Bundle the tested branch harnesses together using tape or sleeving according to drawing requirements to form the final finished product.

7.1 Preparation

• Install location pins on assembly fixture according to engineering drawing

• Confirm location pin position dimensions are within drawing tolerance

7.2 Operation Steps

1. Secure harness: Place the tested branch harnesses on the fixture according to drawing requirements, hanging connectors on corresponding location pins

2. Position check: Confirm all branch positions are correct, no misalignment

3. Tape wrapping:

• Start wrapping from the star position indicated on the fixture

• Tape should overlap by at least 1/2 width

• Maintain even tension, no wrinkling, no looseness

• Stop at the end position indicated on the fixture

4. Sleeve installation: If corrugated tubing, braided sleeving, etc., are required, install according to drawing instructions

7.3 Key Technical Requirements

VIII. Dimensional Inspection: Comprehensive Verification, Ensuring Compliance

Perform comprehensive dimensional measurement on the assembled finished harness to confirm compliance with drawing requirements.

8.1 Operation Steps

1. Fixture preparation: Install location pins on inspection fixture according to engineering drawing, mark all dimensions and tolerance ranges on the fixture

2. Position harness: Place the assembled harness connectors on the corresponding location pins

3. Straighten and measure: Gently straighten the harness, measure all dimensions with steel ruler or tape measure

4. Result judgment: Pass if all dimensions are within tolerance; fail otherwise

8.2 Inspection Items

IX. Visual Inspection: Final Check, Perfect Delivery

Visual inspection is the final checkpoint before products leave the factory, ensuring no appearance defects on the wire harness.

9.1 Inspection Standards

9.2 Conductor Damage Standard
Damage to conductors at the stripping point (e.g., broken or cut strands) shall not exceed 8% of the total conductor cross-sectional area. For example, for 7-strand wire, a maximum of 1 strand slight damage is permit.

9.3 Lighting Requirements
Visual inspection should be performed under adequate lighting conditions. Use magnifying glasses or microscopes for critical areas when necessary.

X. Packaging and Warehousing: Proper Protection, Clear Identification

Finished product packaging is the final key protecting products from damage during transport and storage.

10.1 Packaging Methods

10.2 Packaging Requirements

• Accurate quantity: Confirm quantity per package, eliminate shortages or overages

• No mixing: Do not mix different models or batches in the same package

• Clear labeling: Outer carton label must indicate product model, quantity, production date, inspector code, etc.

• Adequate protection: Vulnerable parts like connectors need additional protection

10.3 Warehousing Management

• Finished products stored in designated areas with clear identification

• Inventory managed using FIFO (First In, First Out) principle

• Regularly inspect inventory product condition

Conclusion: Rigorous Processes Forge Reliable Connections

The ten major process steps above form a complete closed loop for custom wire harness production. From the first cut to the final seal, every detail reflects our persistent pursuit of quality.

As a professional wire harness manufacturer, we deeply understand: reliable connections come from rigorous processes. Behind every wire harness is strict adherence to standards, acme attention to detail, and continuous quality improvement.

Choose KeHan Electronics – Choose a Trustworthy Wire Harness Manufacturing Partner. We don't just produce wire harnesses; we deliver reliability and confidence. For more process details or to customize yourexclusive wire harness solution, feel free to contact us.