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HomeTips & GuidesCable design: Top 5 things to consider

Cable design: Top 5 things to consider

About Cable design, Cable assemblies are an integral part of every industry, and innumerable options cater to each one. Despite the numerous options, finding one that can serve all your needs is challenging. 

So, if you want a cable that meets all your needs, the best thing is to get a custom cable. However, you must consider a few factors that help you get the perfect cable before you design.

Use environment

One essential factor to consider is the cable’s use environment. In a rugged environment, a cable with good abrasion resistance lasts longer. Similarly, high-quality cable jackets can help cables exposed to chemicals.

Don’t ignore resistance, suitability, chemical exposure, moisture, and abrasion resistance when designing a custom cable. Knowing the use environment helps you pick:

Material of the conductor:

Most cable assemblies use copper as their conductor; however, numerous copper alloys are also available, each with unique advantages. These copper alloys offer better tensile strength, temperature resistance, or flex durability than pure copper.

At the same time, some alloys have reduced electrical conductivity. Overall, copper alloys are better for applications requiring 28 AWG or smaller conductors.

Strength members:

Every cable has a component that offers it tensile strength and removes stresses. Commonly known as a strength member, this component must be installed toward the cable’s center to relieve stress. The strength member comprises aramid fiber, a strong material for enhancing cable strength.

It can be found in different configurations. Before picking the strength member of the cable, you need to verify the pull strength of the connector.

Filler and tapes:

In a multi-conductor cable, fillers help to fill gaps in the cable to enhance its rounded nature. They also prevent the entry of fluids into the cable, facilitate cable overmolding, and improve its flex life and durability. Cotton strings, foam, and yarn are commonly used as fillers.

Apart from fillers, manufacturers also use wraps and tapes to minimize crosstalk between different cable components. Also known as separators, tapes and wraps comprise of following materials:

  • PTFE tape: used between shield and cable jacket, PTFE tape offers uniformity, abrasion resistance, and reduced signal loss in high-speed data transmitting cables.
  • Paper tape: also used between the cable jacket and shielding, this inexpensive tape allows easy removal of the cable jacket.
  • Kapton tape: with excellent electrical properties, this mechanically tough and abrasion-resistant tape can operate in high-temperature conditions (-200 degrees Celsius to +200 degrees Celsius).
  • Mylar tape: due to high durability and superb tensile strength, mylar tape is common in cable insulation.

Plating options

Conductor plating is essential to prevent oxidation. Tin, nickel, and silver plating are commonly available. Silver and tin plating effectively prevent oxidation and corrosion and improve solderability. On the contrary, silver and nickel plating offers better protection for high-temperature conditions.

Sealing:

Once you have the right cable and the connectors, you must protect the junctions from liquid ingress. You can opt for either heat-shrink tubing or overmolding.

Heat-shrink tubing offers moderate protection from moisture ingress, while overmolding is a better solution. You also need special sealing processes for sealing a connector’s mating surface. The sealing products should also be reliable and of high quality.

Shielding types:

Shielding refers to the outer conductive barrier surrounding the cable insulation. It protects the signal from noise disturbances from nearby electronics and prevents electromagnetic interference. A cable can have three types of shielding: foil, spiral, and braid.

The effectiveness of the shield depends on its capacity to prevent EMI. Combining braided and foil shields offers the best protection in every sense.

Termination methods:

Soldering and crimping are the two most common contact termination methods. If using only stranded conductors, go for crimping, as it is very reliable. However, you may need special tools, and the conductors may be limited in size.

On the contrary, you can opt for soldering for solid and stranded conductors. This technique does not require special tools and can solder a wide range of conductors, but requires high precision.

Connector types:

The connectors you pick should be compatible with the cable. While picking the connectors, considering the cable assembly environment is essential.

Further, several connector features need to be considered, such as EMI and RFI shielding, durability, weight, electrical requirements, bend reliefs, number of mating cycles, pull-out strength, etc. Your cable manufacturer is the best person to take your opinion from.

Shield-to-connector termination:

You can get an overall shielding effect in the cable assembly only when the shield effectively terminates at the connector ends; the basic rule says the largest opening of the cable determines the overall shielding effectiveness.

The smaller the opening, the better the shielding. Ensure that there is 360-degree shield coverage across the full cable length.

Military Series composite AMP connector

Military Series composite AMP connector

Electrical requirements:

Different electrical requirements play a significant role in designing a functional custom cable. When discussing electrical properties, we refer to voltage, capacitance, and impedance. Knowing these electrical requirements helps you pick:

Size of the cable:

To determine the right conductor size, you must know the cable’s electrical requirements. The amount of power load and at what temperature the cable will perform are important to defining the conductor ampacity and the correction factor.

Insulation materials:

Mainly, there are two types of insulation: thermoplastics and rubber.

Rubber insulation is effective for applications performing in up to 600 volts. Although having limited resistance towards hydrocarbon fuels and oils, rubber offers high flexibility, water resistance and great tear strength.

Silicone insulation is suitable for a wide temperature range of applications, from -60 to 180 degrees Celsius.

Further, you can also opt for inexpensive PVC insulation available in different formulations. However, PVC is not suitable for high-data and high-temperature applications.

For better weathering properties, neoprene is a good option. It also offers oil flame and ozone resistance.

Lastly, fluorocarbons are good options for high-temperature applications due to their low dielectric constant, but they are expensive.

Cable Flexibility:

Some applications require frequent cable movement with millions of flex cycles, while others may remain fixed once installed. However, in the latter case, the installation may require the cable’s flexibility.

Whatever the case, the cable’s flexibility is very important for the cable application. While considering cable flexibility, you must look for the material and the stranding of the conductor. 

Copper alloys with high tensile strength and conductors with fine stranding offer longer flex life.

Strand construction:

The cable can comprise solid conductors with single strands or have stranded conductors. A stranded conductor has many fine wires twisted together.

When combined, the total cross-sectional area of such stranded conductors equals the total area of all the strands. Stranded conductors are helpful in applications requiring flexibility.

However, flexibility in stranded conductors also differs and depends on the stranded construction.

Individual strands in a stranded conductor can be arranged in four different manners:

Bunched lay:

In this, numerous strands are twisted together randomly with all wire strands in the same directions and length. The outer surface of such a conductor is rough. With bunched lay arrangements, you can get the optimum flexibility required, and thus, these conductors are very common.

Unilay:

 There is a central wire in this type of conductor, and many layers of helically placed wires cover it to form a geometric pattern. However, all the layers have the same lay length and direction.

Compared to bunched lay, inlay strands have a larger diameter. This conductor also offers good flexibility, and thus, it is also a commonly available conductor.

Concentric layer:

In this conductor, wire strands have similar arrangements as inlay, but the consecutive layers reverse their lay direction, thus increasing lay length.

After solid conductors, these are the most rounded conductors suitable for electrical purposes, but they are not very common.

Rope lay:

In this conductor, single strands combine into bunched or concentric arrangements; the rope lay arrangements enhance conductor flexibility by using very fine strands and maintaining a tighter diameter. But these conductors are expensive as multiple twisting adds to their costs.

Further, multiple twists also increase the diameter and reduce the copper density. Normally, multi-conductor cables do not use rope lay conductors. Instead, they are often available as solid conductors.

Strain relief requirements:

Secure the junction between a cable and the connector to avoid cable breakage. Although heat-shrink tubing and overmolding offer some strain relief, overmolding alone is insufficient. 

Generally, two connector components offer strain relief: collet and cable clamp, where collet is a more effective option. Further, if you want bend relief to reduce the cable bend strain, consider pre-molded bend relief or what-shrink.

Lastly, another option for bend relief is custom overmold cable. It also gives a very fine finish to the cable assembly.

Cable standards:

Cable customers must ensure that their cable meets standards from accredited firms such as UL, CSA, and CE.

To ensure that your cable meets some or all of these standards, you must be careful in every aspect of cable design. Any leading custom cable manufacturer can help you deliver cables that meet these standards.

Conclusion:

When a designer designs a custom cable, he can adjust AWG size, tolerances, conductor counts, insulation, shielding, print legends and color codes of the cable. Additionally, they can work on the overall diameter of the cable to make it compatible with grommets, grips and connectors.

If you are looking for a custom cable manufacturer, Cloom is here to help you. We deal in various cable assemblies and wiring harnesses required in industrial, automobile, agricultural, military, and other applications.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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