Understanding Wiring Harness Components: Comprehensive Guide by WellPCB

Introduction to Wiring Harnesses

What is a Wiring Harness?

Wiring harnesses (AKA cable harnesses or wire assemblies) are an arrangement of bundled wires, cables, and connectors. Their primary purpose is to neatly package, sort, and secure the cables that transmit electrical and digital signals to systems and devices.

Wire harnesses typically consist of the following components:

• Wires and Cables
• Connectors 
• Terminals
• Cable Management Components
• Protective Sheathing

Wire harnesses have found extensive usage in motor vehicles. For instance, they connect the vehicle’s Engine Control Unit (ECU) to its many sensors and actuators. This allows for precise control of the engine’s performance.

As electric vehicles (EVs) become more common, the world is likely to see more intricate cable networks in motor vehicles that rely on wire harnesses.   

Importance of Wiring Harnesses in Modern Applications

Improved Efficiency 

Bundling multiple wires and cables into a unified construction leads to easier installation. Hence, the use of wire harnesses can substantially reduce the time it takes to set systems up. 

Enhanced Reliability

Wiring harnesses can positively impact the reliability of devices and systems by: 

• Reducing the risk of errors during the installation and connection processes. By curtailing clutter and making the wires more compact, cables become easier to manage and route within a system. 

• Make issues easier to identify and troubleshoot. This minimizes downtime as technicians can repair or replace affected wires faster.   
• Provide additional protection against moisture, high temperatures, and mechanical erosion to the cables and wires they house.    

Wiring Harnesses in Action

Several industries benefit from using wiring harnesses. For instance: 

• Because wiring harnesses allow for faster repairs and replacements, they’re ideal for time-critical use cases like hospital equipment. 
• Wiring harnesses provide cables with additional protection and support which extends their lifespans. This is important in the transportation industry where the operating environments are often filled with constant mechanical stress.    
• The compactness of wire harnesses allows them to fit within the confines of modern devices and systems. This facilitates more space-efficient hardware and systems.

Key Components of a Wiring Harness

The wiring harness design elements are determined by their application. However, there are basic components that all wire harnesses share. 

Electric Wires and Cables

These are essentially the (electrically) functional components of the cable assembly. They consist of wires (conductive elements), insulation, and optional shielding. 

Copper or aluminum typically comprises the wires while PVC, Teflon, or polyurethane comprises the insulation. Shielding in wiring harnesses and cables provides protection from electromagnetic (EMI) and/or radio frequency interference (RFI). 

Connectors and Terminals

Connectors join electrical circuits together. Depending on the type, they can connect cables, other harnesses, or systems. There are two main types of connectors:

• Male/Female Connectors: Facilitates the joining and connection (and disconnection) between different parts of the wire harness and system.
• Pins and Sockets: Small, conductive pieces that enable electrical contact between connectors.

Terminals can be supplementary or serve as alternatives to connectors. They’re endpoints that connect wires to components or devices. They come as either crimps or solder at the ends of wires.

Cable Management

Cable management components allow manufacturers to sort and bundle wires. This includes:

• Cable Ties: Plastic pieces (commonly) that bundle and secure cables together.
• Fixings: Clips and mounts that secure and anchor cables in place, preventing tangling and providing stress relief.     
• Heat Shrink Tubing: Typically made of Polyolefin, PVC, Fluorinated ethylene (FEP), Elastomeric or Silicone. When heated, these tubes shrink to fit tightly over cables, providing them with insulation and protection.   
• Conduits: Protective tube encasements for wires. They offer added protection against environmental and mechanical hazards.
• Trays and Raceways: Assist in routing large stacks of cables.
• Grommets and Bushings: Provide stress relief to cables passing through holes and openings.
• Tapes and Sleeves: Flexible materials like PVC or nylon that protect the wires from abrasion and environmental exposure. 
• Labels and Markers: Used to identify different wiring harness components or circuits for easier installation, troubleshooting, and maintenance.

For effective cable routing and management, you must first extensively plan your layout. Separate power cables from data cables to avoid interference. It’s best to map the cable routes and identify the shortest and most efficient pathways.

Avoid sharp bends and kinks as they may lower the signal integrity and lead to damage. Even the distribution of cables will allow you to avoid intense stress on single points. 

Be careful not to overload conduits and cable trays. Each cable should have ample space to prevent wear and overheating. 

Protective Sheathing

Protective sheathing (AKA cable sheathing or cable jacket) allows the wire harness to guard cables from environmental factors, abrasions, vibrations, and impacts. It also provides added electrical insulation and makes cables easier to bundle.   

Common materials for protective sheathing include: 

• Polyvinyl Chloride (PVC): A flexible and durable material best suited for general-purpose wire harnesses. 

• Polyethylene (PE): Showcases excellent resistance to moisture and weather, making it ideal in wire harnesses for external installations.
• Low Smoke Zero Halogen: When exposed to fire, this material barely emits any smoke or gases, which makes it ideal for installations in large complex office buildings.
• Polytetrafluoroethylene (PTFE): Because of its resistance to high temperatures and chemical stability, it’s suitable for challenging conditions.
• Rubber: Best for use cases that require great flexibility and durability.     

How Components Affect Wiring Harness Performance

The individual wiring harness components work together to create a reliable and efficient structure. How well each component functions is dependent on the following factors. 

Material Selection

The materials you use will impact the durability and overall performance of your wire harness. When selecting materials, it’s important to do so on a case-by-case basis where you consider the following: 

• Environmental and Mechanical Stressors: High-stress environments require more dense and durable materials like metal clips in place of plastic ones.
  
• Cost: Metal-based electrical harness components tend to cost more than their plastic counterparts. The cost of materials will affect the overall cost of your cable assembly. 

• Conductivity: Using high-purity copper for the conductors can offer the best electrical performance, however aluminum is lighter.
  
• Insulation Materials and Protective Sheathing: The materials you select for insulation also have a role to play in the electrical performance of the wiring harnesses. For instance, using Teflon for cable insulation combined with silicone and polyethylene for sheathing can yield the best protection against EMI and RFI. 
  
• Flexibility: Wiring harnesses you plan to fit into tight spaces should have high bend radiuses. Rubber and silicone exhibit excellent flexibility and should be considered in these instances.     

• Temperature Resistance: Wiring harness components used in high-temperature environments must be composed of heat-resistant materials. For example, Silicone and PTFE (Teflon) are both examples of materials that offer excellent temperature resistance. 

MRI machines are an example of medical equipment that require reliable wiring harnesses. They must produce accurate imaging while being safe for patients. Consequently, an MRI machine’s wiring harness must be able to tolerate high temperatures, EMI, and mechanical stress.

Component Integration

The component material types significantly impact the integration of wiring harnesses. Fundamentally, the wiring harness’s materials must be compatible with those of the cables (wires). 

Copper tends to be the best choice for wires because it is highly conductive and also offers excellent compatibility with many insulation and sheathing materials. For example, PVC and polyethylene are resistant to a wide range of chemicals.

Quality Assurance

Quality Assurance (QA) enables manufacturers to ensure the reliability and performance of cable assemblies. By pre-assembling and testing, ensures that each wiring harness part functions as it should and meets quality standards before it is integrated. 

For instance, WellPCB’s QA processes include: 

• Design Verification: Our staff verifies the wiring harness against established specifications and requirements.
• Material Inspection: We systematically inspect and test the materials before moving on to the next stage.    
• Manufacturing Process Control: A supervisor surveys and monitors the manufacturing and assembly process to ensure that all procedures adhere to industry and client standards. 
• Testing and Validation: We rigorously assess the wire harness for any defects. This includes electrical testing, mechanical testing, and environmental testing.  
• Documentation and Traceability: To ensure traceability, we keep highly detailed documentation and records of the materials, processes, and tests conducted.

In addition to the above processes, WellPCB adheres to the following standards and certificates:

• IPC/WHMA-A-620
• Underwriters Laboratories (UL)
• ISO 9001
• Restriction of Hazardous Substances (RoHS)

Latest Advancements in Wiring Harness Components

The industry has seen a wide range of exciting trends and advancements in wiring harness component design. 

Technological Innovations

Polymers and composites such as Poly-ether-ketone-ketone (PEKK) can withstand extreme temperatures. High-resistant materials such as these reduce the risk of melting and fire. This makes them ideal for wire harnesses that will be used in aerospace, the automotive industry, and industrial environments.  

The Internet of Things (IoT) will also reshape how we manufacture wiring harnesses. Smart materials and components can monitor and report the health of the harness. Self-healing polymers and conductive inks have the potential to increase the durability and lifespan of wire harnesses.   

Industry Trends

The use of lightweight materials and miniaturization will allow us to develop more space-efficient and lighter cable assemblies. 3D printing is reshaping the manufacturing industry as a whole. Additive manufacturing will allow manufacturers to produce wiring harnesses with more intricate designs. It will also potentially reduce waste and decrease costs.

There’s also been an industry-wide drive to produce more environmentally friendly and sustainable wire harnesses. By leveraging biodegradable insulation materials and recycled metals, we can reduce the environmental impact of wire harnesses.  

Selecting the Right Components for Your Application

Now that you’re informed on the basics, how do you choose the right components for your application? 

Assessing Industry Requirements

As we previously mentioned, different industries and applications have unique requirements. For instance, the automotive industry requires wiring harnesses with exceptional durability, high vibration resistance, and the ability to withstand high temperatures. 

This is because these wire harnesses will connect electrical components of vehicles such as lights, sensors, and control units. As such, the fabrication of these wiring harnesses must adhere to the ISO 9001 and IATF 16949 standards.  

On the other hand, the aerospace industry requires wiring harnesses with lightweight materials that are still reliable and resistant to extreme temperatures and EMI. These wire harnesses need to be able to power avionics, communication systems, and control systems in aircraft. They need to meet the AS9100’s strict standards.

Best Practices for Integration

Strategies such as modular design can make integration more seamless and efficient. Modular design involves creating smaller harness sections that can function independently. This technique simplifies the assembly process and makes wire harnesses easier to maintain. Moreover, it allows for easier upgrades, repairs, and replacements.

You can increase the compatibility of your wire harness by sticking to standardized parts. Using custom wiring harness parts makes it harder to source replacements for damaged components and complicates inventory management. You can address these issues and ensure consistent quality by using standardized components. 

Another way to ensure cohesion and make integration easier is by using color coding and labeling. This makes it easier to identify and organize components. If you perform them correctly, color-coding and labeling can decrease the potential for errors, speed up installation, and ease repair and maintenance.

WellPCB’s Expertise in Wiring Harness Components

WellPCB is a name you can trust in sourcing and manufacturing wiring harness components. We offer a comprehensive selection of services and capabilities. 

Proprietary Technologies

WellPCB utilizes the latest technology to bring your designs into reality. We use the latest automated wire-cutting and stripping machinery to precisely shorten your wires to specification.      

These are not the only wire processing tasks our machines can handle. They can also crimp, solder, and add termination to the wires. This ensures high accuracy and consistency and reduces manufacturing errors. We also bend and form, tie and label, splice, and produce sleeving and tubing for insulation. 

WellPCB performs comprehensive testing at multiple points of the manufacturing cycle. Our partnerships with Amphenol, JST, Molex, and Tyco Connectivity give us access to a reliable supply chain for raw materials. 

Customization Capabilities

WellPCB specializes in custom wiring harnesses. We cater to various industries such as medical, automotive, telecommunications, and consumer electronics. Our highly experienced team handles the entire process from design to sourcing, and performing the final assembly process.   

Quality and Compatibility Assurance

Compatibility and quality assurance are important to us. That’s why we implement such stringent testing and inspection protocols.     

Rigorous Testing Procedures

When you partner with WellPCB, your wiring harnesses will undergo stringent visual inspection. During this inspection, we systematically examine their design and structure, looking for flaws or damage to the integrity of the wires, connectors, and sheathing.   

In addition to the tests and inspections, we also perform dimensional measurement, continuity, high potential, and failure probs. 

Compliance with Industry Standards

WellPCB holds and adheres to the following standards and certificates:

• IPC/WHMA-A-620
• Underwriters Laboratories (UL)
• ISO 9001
• Restriction of Hazardous Substances (RoHS)

Conclusion

The above article essentially proves that wire harnesses are greater than the sum of their parts. However, you must choose components that will best meet the demands of an application as well as work well with the other components of the wire harness. This is the best way to ensure that your wiring harnesses perform optimally and are durable. Another way is to select a reputable and reliable manufacturer. WellPCB is this manufacturer. Contact us today to learn how we can help you build high-performing wiring harnesses.

Frequently Asked Questions (FAQ)

What are the main components of a wiring harness?

The main components of the wiring harness are the cables, connectors, protective sheathing, and cable management parts. 

How do connectors and terminals function in a wiring harness?

Connectors and terminals bridge different sections of the wiring harness and also connect the wiring harnesses to other devices and systems. 

What materials are used for insulation in wiring harnesses?

The most commonly used insulation materials include PVC, Teflon, Silicone, Polyethylene (PE), rubber, and LSZH (Low Smoke Zero Halogen). 

Why is shielding important in wiring harness components?

Shielding in wire harnesses ensures that signals within the wiring harness remain unimpeded from any outside interference, ensuring reliable data transmissions. 

How does WellPCB ensure the quality of wiring harness components?

WellPCB ensures quality through rigorous testing, inspections, and strict adherence to industry standards and guidelines.