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Large diameter, clear coated Sava Cable

What is Coated Mechanical Cable?

Wednesday, February 22, 2023

The material applied to coated mechanical cable is a molten, extruded chemical that coats bare cable entirely, protecting the solid wire from making direct contact with the environment with which it is deployed. This extruded material is designed to provide a barrier of protection against mating components, or maybe worse, harsh conditions that could shorten the lifespan and integrity of the mechanical cable.


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There are many variables to analyze when determining, not only if coated cable is a fit, but as importantly, the kind of coating to apply to the cable, along with coating diameter, cable length, mating component compatibility – and even coating color.

Selecting the wrong pulley groove, or perhaps too thick a coating diameter, for instance, and one will increase the likelihood of a shortened cable life, system life, or other unwanted failures in the field. Applying fittings to coated cable incorrectly may shorten the lifespan of the cable assembly as well. And, as mentioned, even the color of the coating applied to the cable assists in perfecting the coated mechanical cable assembly for your system.

Uncut clear extruded mechanical cableUncut clear extruded mechanical cable
Uncut clear extruded mechanical cable

Key Characteristics of Coated Mechanical Cable

While there are many benefits to using coated cable, there are four key characteristics of coated mechanical cable that easily demonstrate its benefits in the field.

Resistance to Fatigue

For one, due to the protective properties of the coating that insulates the cable’s wires, coated cable is less susceptible to fatigue over time than bare cable. This feature alone gives coated cable a lifecycle advantage because bare cable has direct exposure to environmental variables. Variables such as particulates in the air, and on surfaces, as well as harsh weather, degrade the strength and performance of bare cable more easily. As a matter of fact, it is not unusual to see coated mechanical cable achieve significantly more cycles than its bare cable counterpart because the coating affords the wire rope a more protracted lifespan.

Coated Cable Lubricant

Aiding in coated mechanical cable’s quotient of impermeability to fatigue is the lubricant added to the bare cable during the coating process. This lubricant creates a barrier, similar to the one achieved when placing work gloves on one’s hands in a dangerous environment. Like the gloves, the extruded (coated) mechanical cable protects the wire rope itself from surrounding harmful conditions. Additionally, the lubricated layer separating the coating from the solid wires allows the extruded material to flex with reduced risk of cracking or splitting of the coating because the lubricant reduces friction between the wires themselves when a system is experiencing force, load, or motion.

Coated Cable Diameter

As much a benefit as it is a cautionary note, the thickness of the extruded material in your coated mechanical cable plays an integral role in the fitment of your cables within your system.

Too much extruded material and your coated cable will not fit within the tight spaces allotted in most motion control systems. Too little extruded material applied to your coated mechanical cable and the wires comprising the cable risk exposure to hostile environmental conditions.

Carl Stahl Sava Industries typically manufactures coated cable as small as .004”, and as large as .11”. In applications requiring more unique coating diameters, it is best to consult your cable manufacturer’s engineering team.

Stripping Coated Cable for Better Holding Strength

Contributing to the resiliency of coated cable is the way with which fittings are applied to the cable.

To achieve the full-rated breaking strength of a coated mechanical cable assembly, fittings need to make direct, metal to metal, contact with the cable itself. If the coating of the cable assembly is not stripped, the cable could achieve as little as 50% of the full-rated holding strength of the cable.

However, not every coated cable application requires that the cable achieve its full-rated breaking strength. For example, a miniature coated cable assembly, that only needs to support 1 lbs., but has a breaking strength of 5 lbs., will perform optimally even with fittings applied directly to the coating.

Be aware, however, that stripping extruded cable is not as easy as it sounds.

There are many ways to extrude cable and the method used to coat the mechanical cable informs the ease with which the cable is stripped of its extruded material.

Black coated cable with stop sleeve on the endBlack coated cable with stop sleeve on the end
It's important to ensure fittings are applied directly to the cable to achieve full breaking strength

Although there are others, Sava performs two different extrusion processes: pressure down extrusion and vacuum extrusion.

Pressure down extrusion is the process of impregnating the cable, inclusive of even the microscopic spaces within the cable’s helical strands. Pressure down extrusion makes stripping the coating from the cable a complex and sophisticated task, inasmuch as the coating literally exists nearly everywhere, and not just merely on the exterior of the cable. Stripping a coated cable that was extruded using the pressure down method cannot be achieved with simple hand tools because human hands cannot replicate the surgical accuracy and torque applied by an industrial stripping machine.

Vacuum extrusion, by comparison, is a process that makes the cable’s coating far easier to strip by hand. Vacuum extrusion is the process of applying extruded material directly to the cable, without the presence of pressure, making the coating exist only over top of the cable like a jacket wrapping around the wire rope. Note however that the vacuum extrusion method of coating mechanical cable applies extruded material no further than the surface of the cable.

Therefore, using vacuum extrusion, the cable’s coating material is easily stripped from the wire rope because the coating did not fully permeate the wires like they would have been in pressure down extrusion.

Coated Cable Materials

Once the design engineer has determined the appropriate extrusion method for the application, it’s time to consider the coating material itself.

With any cable coating material, there are trade-offs. Adding flexibility, for instance, may come at the cost of durability over time. Reducing heat tolerance may make the coated cable ideal for temperate conditions, but the trade-off would be that excessive heat may damage a less heat-friendly coating.

Blue, nylon coated cable for MedTech applicationsBlue, nylon coated cable for MedTech applications

Nylon Coated Cable

Each having its plusses and minuses, there are several distinct properties that make nylon a desirable choice for coated mechanical cable applications.

To start, nylon coated mechanical cable is a popular choice when considering the life span of the cable due to its resistance to abrasion. Given coated cable is likely to perform a system-critical actuation, like moving over a pulley system for example, nylon coating is ideal because, as the coated cable traverses a system, it will exhibit a tremendous tolerance to abrasive forces.

In the MedTech space, nylon coated mechanical cable is also extremely popular, as these cables commonly perform pitch and yaw functionality. Thus, mating components and other system parts that lend to the coated cable in motion are helped by nylon’s ability to shoulder a long life smoothly moving across and within other mechanisms.

Further demonstrating the advantages of nylon coated cable is that it can increase the life of the cable by between 300% and 1,000%, over bare cable alternatives. This dramatic improvement to the coated cable’s lifespan is attributed to the fact that the nylon coating binds itself to the wire rope, thus creating a seal that traps the cable’s lubricant beneath the nylon. The combination of the nylon’s ability to resist destructive abrasive forces, as well as produce an insoluble seal around the lubricated cable, makes nylon coated cable the standard in MedTech coated mechanical cable applications.

Although nylon coated cable is one of the most popular extruded mechanical cable choices, among its disadvantages are both its lack of heat durability and its eventual hygroscopic vulnerabilities. While there are many nylons available on the market, those coating mechanical cable are commonly extruded using nylon 11. Under most circumstances, nylon 11 begins to experience deformation from its manufactured shape once temperatures reach 180° Fahrenheit. Lastly, nylon coated cable will ultimately absorb moisture in the air around it, which may lead to oxidation and perhaps failure later.  

FEP Coated Cable

Cable coated with Fluorinated Ethylene Propylene, better known as FEP coated cable, is an excellent alternative to nylon for several reasons.

Like nylon coated cable, FEP coated cable protects wire rope from abrasion and environmental and chemical contaminants, while shielding the cable from shock and pressure. But FEP coated cable possesses an exceptional tolerance to extreme temperatures – far more than does nylon coated cable. As a matter of fact, the rated melting point of FEP is between 487° and 540° Fahrenheit, making it able to tolerate roughly twice the heat of nylon coated cables.

Additionally, FEP, which is a type of Teflon, is smoother than other extruded material due to its low coefficient of friction. Teflon, being known for its tactual slickness, allows FEP coated cable to glide more easily into mating parts and systems.

Also benefiting from the natural properties of Teflon, FEP extruded cable is relatively easy to strip, making applying fittings to the wire rope a less daunting operation.

Exposing coated wire rope to moisture may cause oxidation or some other cable-damaging contamination, which may cause premature failure to the cable. Considering environments consisting of moisture, vapor or other airborne particulates, FEP coated cable is chemically inert and therefore, less likely to absorb the chemical elements in its orbit.

Think about a spacecraft or aircraft. FEP coated cable is popular in such applications because of its inherent heat and moisture absolvent properties. For example, in a zero-gravity environment, particulates never land – as the lack of gravity tosses everything about. FEP coated cable will not absorb, nor attract floating contaminants, making FEP ideal for space exploration. Similarly, in aircraft, landing gear is exposed to broad temperature shifts, making FEP coated cable well-suited to protect this mission-critical cable assembly from failure during any phase of flight.

Vinyl Coated Cable

Polyvinyl Chloride, which is better known as PVC or vinyl, is one of the most popular outdoor choices for coated cable. Among the reasons it is so well-suited to outdoor applications is its tolerance to excessive heat over time. Vinyl coated cable melts between 212° and 500° Fahrenheit, depending upon other applications and environmental considerations. Nylon, another popular cable coating material by comparison, possesses a melting point of approximately 180° Fahrenheit. And while 180° is typically adequate to support outdoor coated cable applications, design engineers expect coated cable to last an exceedingly long time.

Another benefit to vinyl coated cable is its inherent UV defenses. Ultraviolet rays cause severe damage to virtually any object under the sun. Coated cable is no exception. The natural UV resistance that vinyl possess makes it an ideal coating material for mechanical cable applications being deployed outdoors. And while additives can be mixed with nylon and other coating materials, that would improve its tolerance of harsh UV rays, vinyl, off the shelf, shoulders UV protection as good as any extruded cable material will.

Assorted nylon, vinyl, and FEP coated mechanical cableAssorted nylon, vinyl, and FEP coated mechanical cable
Assorted nylon, vinyl, and FEP coated mechanical cable

Importance of Coated Cable Color

No matter the extrusion material used to produce coated mechanical cable, the coating itself affords the wire rope a layer of durability and protection against environmental factors, as well as any harmful consequences created when bare cable makes contact with other metal surfaces. But color, interestingly enough, also lends to the protective benefits of coated cable too. For example, if your coated cable application is serving a safety need, such as is commonly the case in emergency pull cord applications, coating color becomes an important consideration as well. After all, colors like yellow, red, and orange are globally synonymous with cautionary messaging, which means coating material, coating diameter, and even coating color coalesce to inform the overall benefits of the coated cable within a system.

Get Coated Cable Right the First Time

Coated mechanical cable serves a wide range of MedTech, industrial and aerospace applications. Wire rope can be coated in a diverse array of materials, including nylon, FEP, vinyl and more. To ensure the coated mechanical cable used in your system exceeds both the application and environmental requirements, contact Sava’s engineering team now and get the advice you need from coated cable makers with over 50 years of experience.


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February 22, 2023