Custom Cable Design Guide | Cable System Best Practices

 

 

Proper cable design is essential across industries like telecommunications and power distribution, ensuring the reliability, efficiency, and safety of electrical systems. A well-designed cable minimizes risks such as signal interference, power loss, and mechanical failure—critical factors in maintaining optimal performance and extending system longevity. Now, let’s explore how to create an effective cable, starting with its core components.

 

Key Components for Cable Configuration

Normally, a cable may include the conductor, insulation, shielding, wraps, fillers, strength members,  breather tube, and jacket.

 

Conductors

Conductors are the core of a cable, carrying electrical currents and significantly affecting the cable's overall performance. The conductor can be made as solid or stranded. Solid conductors offer better signal transmission over long distances with minimal loss, making them suitable for fixed installations. Stranded conductors are made of several thin strands twisted together, providing flexibility and resistance to fatigue, which is ideal for applications requiring movement or bending.

 

Also, the arrangement of strands within a stranded conductor affects the overall cable flexibility and strength. Different stranding techniques, such as concentric, bunched, or rope lay, can be employed to achieve the desired mechanical properties. The choice of material and design is vital, influencing conductivity, flexibility, and durability. Here are some common materials used:

• Copper is the most commonly used conductor material due to its superior electrical conductivity, thermal properties, and corrosion resistance. It is highly ductile and malleable, which makes it suitable for a wide range of applications, from household wiring to high-performance power transmission. Tinned copper enhances protection against oxidation, especially useful in outdoor or moisture-prone environments.
• Aluminum is another popular conductor material, especially valued for its lightweight and cost-effectiveness. While it doesn't conduct electricity as well as copper, it is widely used in long-distance power transmission due to its lower cost and lighter weight, which reduces structural load. However, aluminum is more prone to corrosion and has a lower flex life.
• Steel is often used in applications that need high mechanical strength. While it is not as conductive as copper or aluminum, it can be combined with copper (e.g., copper-clad steel) to improve its conductivity. Steel is frequently employed in cables that need to endure mechanical stress, such as coaxial cables and grounding systems.
• High-strength metal alloys, such as tin-copper, iron-copper, silver-copper cadmium copper, chromium copper, and others, are used in applications where both strength and flexibility are important. These alloys offer high tensile strength and extended flex life, making them ideal for industrial and specialized electrical applications that experience mechanical stress alongside electrical demands.
• Tinsel wire, made by wrapping flat metal foil around a textile core, offers high flexibility and durability, ideal for applications requiring frequent bending, like telephone cords and headphones. Though it has lower conductivity, tinsel is perfect for low-current, high-flex applications where traditional conductors would wear out due to repeated movement.

 

Insulation

Cable insulation plays a vital role in both protecting and ensuring the efficiency of electrical and communication systems. It serves as a non-conductive barrier that keeps the electrical current flowing through the conductors and prevents unintended contact between them, reducing the risk of short circuits. Insulation also enhances signal quality by minimizing interference such as electromagnetic noise and crosstalk between adjacent cables. Moreover, it acts as a protective shield against environmental factors like moisture, chemicals, heat, and physical damage, which can all degrade cable performance.

 

When designing cable insulation, key considerations include the environment in which the cable will be used, the required flexibility, temperature range, and resistance to factors such as moisture and chemicals. Choosing the right material ensures the cable's durability, safety, and signal integrity in the intended application. Let’s look at some of the common materials used:

• PVC: Polyvinyl Chloride is widely used for its cost-effectiveness, flexibility, and resistance to moisture and chemicals. Its flame-retardant properties make it suitable for general-purpose wiring, though it can lose flexibility in colder conditions.
• PE/Foam PE/XLPE: Polyethylene, especially in its cross-linked (XLPE) form, offers high moisture resistance and dielectric properties, making it ideal for outdoor or high-frequency applications. Foam PE enhances flexibility, while XLPE provides heat and abrasion resistance.
• PP: Polypropylene is valued for durability, chemical resistance, and higher temperature tolerance than standard PE, commonly used in data and telecom applications.
• Fluoropolymers (PTFE, FEP, PFA, THV, PVDF, ETFE): Known for heat and chemical resistance, these materials are often used in aerospace and harsh industrial settings, offering excellent dielectric properties. For some harsh environments or military applications, cross-linked fluoropolymers would be considered.  
• Silicone: Highly flexible and resistant to heat, silicone is ideal for high-temperature industrial and medical environments.
• TPE: Thermoplastic Elastomer is flexible and durable, especially suitable for cables requiring frequent movement. The TPE family includes types like TPO, TPV, TPES, and TPE-E, each offering unique flexibility and resilience.
• Nylon: A tough and resilient material, often used as a secondary insulation layer to add strength and abrasion resistance.
• TPU (PUR): Known for its exceptional flexibility, and resistance to oil, and abrasion, making it ideal for industrial applications and retractile cords.

 

Shielding

Cable shielding is a crucial technique used to protect wires and cables from electromagnetic interference (EMI) and radio frequency interference (RFI), ensuring the integrity of signal transmission. Shielding acts like a barrier that both blocks external noise from entering the cable and prevents internal signals from radiating out, which is important for avoiding disruptions in nearby devices. This protection is especially important in environments where sensitive electronic equipment operates, such as telecommunications or audio systems.

There are 3 common types of shielding:

 

• Braid Shielding: Composed of woven strands of copper or aluminum, braid shielding offers robust structural integrity and moderate protection against EMI, especially in environments with low-frequency noise. Due to its flexibility and higher flex life, it is suitable for cables requiring frequent movement. Braid shielding also reduces crosstalk but can be slower to manufacture and harder to terminate with higher costs.
• Foil Shielding: Made from a thin layer of aluminum or copper bonded to a polyester film, foil shielding offers 100% coverage, making it highly effective against high-frequency EMI and crosstalk. It's lightweight, cost-effective, and easy to apply. However, foil shielding is less flexible, making it ideal for stationary applications with limited movement, where long-term durability is not compromised by flexing.
• Spiral Shielding: Often found in audio cables, this type involves wrapping wire in a spiral pattern around the conductors. While it provides less EMI protection compared to braid or foil, it offers superior flexibility, making it ideal for applications like audio cables where frequent flexing is necessary, even though its overall flex life may be shorter than that of a braid.

 

When designing a shielded cable, factors like the frequency of the signals, the amount of mechanical flexibility required, and the level of EMI protection needed are all important to consider. For optimal shielding performance, combining different types, such as a braid and foil, can provide both structural integrity and comprehensive protection from interference.

 

Wraps

Wraps, also known as tapes, enhance noise suppression between components inside components, reduce crosstalk, and facilitate the assembly process. These wraps are applied around conductors, fillers, or the entire cable core to maintain structure and provide an additional layer of protection.

 

Common materials include PTFE (polytetrafluoroethylene) tape, which is highly valued for its flexibility and durability in extreme temperatures. It’s commonly used in high-speed data cables because it minimizes signal loss and offers excellent abrasion resistance. Polyimide, AL/MY or Mylar (polyester) tape, on the other hand, is known for its tensile strength and resistance to high temperatures, making it a top choice for industrial environments where cables face harsh conditions.

Polyimide tape, for example, is widely used due to its mechanical toughness and excellent resistance to high temperatures, moisture, and abrasion. This makes it ideal for demanding environments, like high-temperature or high-performance applications.

 

In addition, paper tape is a cost-effective option, primarily used as a separator between the cable jacket and shield. While it provides basic insulation and makes jacket removal easier, it lacks durability when exposed to heat or constant flexing. 

 

Fillers

Fillers are used in cables to maintain structural integrity, improve durability, and reduce friction between conductors. They fill gaps within the cable to add tensile strength and protect against external elements. When choosing fillers, their impact on the cable's mechanical strength, flexibility, and environmental resistance should be carefully evaluated.

Foam is another common filler material, known for its lightweight nature and flexibility. It is typically used to fill small gaps between conductors, helping maintain the cable's shape without adding unnecessary weight.

Lastly, plastic fillers like polyethylene are commonly used in long cables, where they help reduce electrical interference while providing structural support. Polyethylene fillers are also valued for their moldability and lightweight, making them ideal for cables requiring both flexibility and strength.

Strength Members

A strength member is an essential part of a cable's configuration, designed to add mechanical support and protect the cable from stress during installation and use. Its main function is to prevent the cable from being damaged under pulling, twisting, or bending forces, which is especially important in tough environments where cables are constantly exposed to strain.

 

There are different types of strength members available depending on the application's requirements. Aramid fibers are popular for their high tensile strength and lightweight, making them ideal for applications requiring flexibility and high pull strength. Steel strength members provide both tensile and compressive strength, often used in heavy-duty settings where durability is a must. Fiberglass rods, on the other hand, offer rigidity and excellent compressive strength, but they can become brittle in extreme temperatures.

 

When selecting the right strength member for a cable, consider factors like the required pull strength, the cable’s flexibility needs, and whether the strength member must be terminated to a connector. Environmental conditions, such as temperature and moisture exposure, also play a key role in determining the most suitable material. Aramid fibers are lightweight and flexible, while steel or fiberglass are preferred for applications needing greater strength and rigidity.

Breather Tube

A breather tube in cable design is essential for managing pressure and moisture, ensuring the cable’s durability, especially in fluctuating environments. By allowing the cable to "breathe," the tube adjusts to temperature and humidity changes, preventing harmful condensation that can cause electrical failures or corrosion. It also aids in pressure equalization, crucial in high-altitude or submerged environments, by balancing internal and external pressure, thus protecting the cable from damage.

 

When selecting breather tubes for cables, a designer must consider several important factors. First, the purpose of the tube is crucial, as it defines the material selection. If the tube is meant for supplying or suctioning fluids (like water or chemicals), or gases (such as oxygen or air), the type of substance will influence the material. It could also be designed as a vent to release heat or pressure.

 

Second, the required cable features play a role in determining the tube’s flexibility and rigidity. The tube must be sturdy enough to avoid kinking but flexible enough to maintain the cable's durability and flexibility over time, especially in applications requiring a specific bend radius or high flex life. Additional factors like over-molding or connector types also affect the material choice.

Lastly, the environmental conditions the cable will be exposed to are key. For example, if the cable is used in wet, chemically active, or extreme temperature environments, the materials must be selected to ensure performance and durability under those conditions.

 

Jacket

Jackets serve as the outermost layer, offering essential protection against environmental factors, mechanical damage, and chemical exposure. Its main role is to safeguard the internal components.

 

The jacket shields the cable from moisture, UV rays, chemicals, and extreme temperatures, making it especially important in harsh environments like industrial sites or outdoor installations. It also provides mechanical protection from physical damage caused by abrasion, impact, or bending, and must resist chemical exposure in environments where oils, solvents, or acids are present.

 

Some of the common materials used to make jackets include:

 

• PVC: A popular, affordable choice resistant to oils, chemicals, and abrasion, with flame-retardant properties. It’s widely used for electrical wiring.
• TPE: Offering flexibility and durability, TPE jackets can resist a variety of environmental factors. The TPE family includes TPO, TPV, TPES, and TPE-E for tailored performance.
• Silicone: Highly resistant to temperature extremes, silicone jackets are used in industrial and medical applications.
• Fluoropolymers: Extremely resistant to chemicals and high temperatures, often used in rugged environments.
• EPDM: Known for its weather and ozone resistance, this rubber-based jacket material is ideal for outdoor and harsh environments.
• TPU (PUR): Provides excellent flexibility, oil resistance, and durability, suitable for cables requiring repeated movement.

 

How to Design a Cable: What Else to Consider

Designing a cable involves more than just choosing the right components; it requires a detailed understanding of how each element interacts with the environment, electrical requirements, and mechanical stresses. Let’s dive deeper!

 

Application Requirements

Understanding the environment where the cable will be used is crucial. Factors like temperature extremes, humidity, chemical exposure, and physical stress such as bending and vibration significantly impact the cable design.

For example, in a medical environment, the cable might need to be sterilizable and biocompatible. In outdoor applications, UV resistance and moisture protection are important. Identifying these requirements upfront helps in selecting appropriate materials and configuration methods to ensure the cable's performance and longevity.

 

Termination

Termination is a critical aspect of cable design, as it ensures secure connections and affects the overall durability of the cable assembly. There are 3 primary termination methods:

 

• Crimping: Provides reliable connections with stranded conductors using automated machinery and special tooling. It’s efficient for mass production but requires precise tooling for consistency.
• Soldering: Suitable for both solid and stranded conductors, offering a wider range of sizes. It requires skill to ensure strong, reliable joints, making it ideal for custom or small-scale applications.
• Molding: Involves creating a protective layer around the cable termination, often using plastic or rubber materials. This method offers enhanced strain relief and environmental protection, making it suitable for applications requiring robust durability and flexibility. Overmolding can also add waterproofing and mechanical reinforcement to the cable ends.

 

Voltage Regulation

Voltage regulation refers to the cable's ability to maintain a stable voltage level between the source and the load, despite variations in current flow. Poor voltage regulation can result in excessive voltage drops, leading to equipment malfunction or damage, especially in long cable runs. The National Electrical Code (NEC) recommends a maximum voltage drop of 5% for efficient electrical systems.

 

Proper cable selection involves choosing the right conductor size and insulation to minimize voltage drops. This is particularly important for low-voltage systems where long cable lengths or heavy loads are involved. Additionally, cables must be designed with the appropriate short-circuit rating to withstand potential faults without sustaining damage until protective devices like circuit breakers engage.

 

Holding Standards Agency Listings

When designing cables, it's crucial to consider international standards to ensure safety and performance. ISO standards like ISO 9001 (quality management) and ISO 13485 (medical devices standards) are globally recognized.

In North America, UL (Underwriters Laboratories) and CSA (Canadian Standards Association) govern safety, flame resistance, insulation, and voltage ratings. UL standards like UL 1581/UL 758 cover flexible cords and electrical wiring, while CSA sets similar benchmarks for Canada. Adhering to these standards ensures compliance, safety, and product reliability across various applications.

 

Common Mistakes to Avoid When Designing a Cable

Designing a cable might seem straightforward, but small missteps in the process can lead to costly errors, compromised performance, and product failures in the field. Let’s see some of the most common mistakes when designing a cable.

 

Over-Specifying Specifications

Specifying cables with overly precise tolerances or unnecessary components can increase manufacturing complexity and cost. When tolerances are too tight, it can slow down production, increase labor costs, and make the design more difficult to assemble. It's essential to balance precision with practicality, ensuring the design meets the requirements without being overly complex or expensive. 

 

Vague Design Descriptions

On the contrary, providing vague or imprecise design specifications can also lead to unwanted results, like misinterpretation and errors during the manufacturing process. Clear, detailed descriptions, including specifics like voltage, temperature, flexibility, and gauge, are necessary to ensure that the final product meets the desired performance and quality standards.

 

Assembly Difficulty

Designs that are difficult to assemble can lead to delays, increased labor costs, and a higher risk of errors during production. For example, selecting wire and terminal pairings without considering insulation size can result in incompatibilities, even if they appear compatible on paper. Ensuring that components fit together properly and can be assembled efficiently is crucial for a successful cable design.

 

Disregarding Connector Compatibility

Choosing connectors that do not align with the cable's design or application can lead to connectivity problems and signal degradation. Connectors must match the cable's physical dimensions and electrical specifications while considering environmental resistance. Mating cycles, ease of connection, and mechanical robustness are important factors to consider when selecting connectors.

 

Contact Winfox for Expert Custom Cable Design Solutions Now!

Cable design plays a pivotal role in ensuring the reliability, safety, and efficiency of electrical systems. It involves careful consideration of various components like conductors, insulation, shielding, and jackets, each contributing to the cable's overall performance and longevity. Proper design helps mitigate issues such as electromagnetic interference, mechanical stress, and environmental hazards, thereby extending the operational life of the system.

 

For custom cable solutions that truly fit your needs, Winfox is your go-to partner. With decades of experience and a robust portfolio of patents, we offer a wide range of high-quality custom cable assemblies, including medical cables, automation cables, flat ribbon cables, coil cords, and other types of cables. Our expert team excels in tackling complex challenges to ensure your cable system delivers optimal performance and durability. Discover how Winfox can bring your custom cable design projects to life with precision and expertise. Contact us today for exceptional service and innovative solutions.