When looking to spec in a cable that will work for your application, the cable's degree of flexibility is an important and often overlooked, factor to consider. Some cables are physically flexible, which can ease routing concerns during installation, but other cables are actually designed to be installed in flexing applications with different types of motion.
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Without considering the type of flexibility you need from your cable, you could choose the wrong cable and that will then have a reduced life cycle. Making the right choice the first time will save you the headache of your system going down and trying to identify the right cable in a hurry. If you have any questions about flexible cable, please contact us at the button below to get in touch with one of our wire and cable professionals.
The type of insulation material used, whether or not there is a shield, wrap, or fillers, and the conductor's stranding are factors in this equation. With this, it is also important to note the number of flex cycles that the cable can withstand, the cable's weight, the type of flexing motion that the cable is capable of performing, and the cable's bend radius. While the cable's bend radius tells you how tightly the cable can bend without damage, it does not tell you that the cable can be used without damage in a motion application where there is constant movement at that bent angle.
There is no official, acknowledged scale or terminology to define different types of cable flexibility, but below we detail the most standard cable flex types and the applications where each is the best option.
Though terminology and testing standards are not uniform across all manufacturers, knowing which type of motion stress your cable will be under is important in order to choose a cable with the correct level of bendability and flex life. It could save you a lot of time, money, and headache in the future.
For more detailed information on LAPP cable ratings and flex life, refer to the datasheet of the specific product you're interested in and reference the technical information section linked below.
LAPP Cable Motion Types & Levels
For questions about what type of flex cable you may need, feel free to reach out to a Lapp Tannehill customer service representative at 800.633. or chat with us online.
Cable types include terms like 'flex,' 'flexibility,' and 'flex life'. What factors affect or influence flex? What are the best material options to make a cable solution more flexible or maintain a longer flex life?
Understanding the flex requirements of an application is crucial before selecting the wire and cable material and components. Knowing how many cable systems are required to tolerate movement ' whether small movements during initial installation or daily repetitive movements.
Within the world of 'flex,' flexibility and flex life may sound equivalent, but there are key differences. In fact, some high flex cables can have short flex lives, and other wires and cables with high flex life may not be particularly flexible. Let's take a look.
Simply put, flexibility is a measure of how much movement a cable can tolerate at a given time. Flexibility types include: torsional, rolling, bending, and variable. When a cable is bent, twisted, or pulled into positions beyond its original state, its flexibility is tested.
Flexible cable can bend significantly and stay bent for a large amount of time without being damaged.
If your cable needs to bend or curve around infrastructure, you may need high flex cable, or cable with strong flexibility.
Flexible cable is also referred to as 'supple'. Flexible cables are soft, supple, and easy to manipulate or bend back and forth. Think of a surgeon using an electrosurgical tool. With this application, the surgeon needs supple, flexible cable to easily manipulate the tool. Cable kinking, back twisting or pulling on the surgeon's hand would result in fatigue and less surgical precision.
Flex life deals with how often a cable moves without becoming damaged. Many cables can bend for limited use, such as during installation. High flex life cable bends repeatedly and routinely without disrupting the cable's intended use. Examples include power supply cables, data transfer cables, and robotic application cables.
Ultimately, if your cable needs to move well, it must be flexible. If your cable needs to move often, it must have a high flex life. In many applications, such as industrial machinery or factory automation, both flexibility and high flex life are required.
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Repetitive flexing can cause serious damage to wire and cable systems. Internal conductors may break, outer jackets can erode or tear, and friction can cause overheating. Not only does this decrease the lifespan of the cable, it can cause system downtime or damage.
System downtime or damage can be avoided by selecting the right cable materials and components for optimal flex characteristics. Material choices in a variety of components can help increase flexibility or extend flex life for your end application. These include stranding, conductor insulation, braid, strength members, jacketing and more.
For a high flex cable, choose a high strand count. Typically, the more strands, the more flexible and the longer the lifespan of the cable.
For movement and motion, a rope lay stranding construction is the most flexible configuration. It is also the most expensive. These are the trade-offs to consider when choosing materials. With the rope lay configuration, there are a number of individual bundles of stranding twisted into groups that make up one larger, solid configuration.
When aiming to achieve a high flex life, concentric stranding is a better choice. In a concentric strand, there is a solid conductor running down the center that is surrounded by layers of rotating strands. Each layer is comprised of strands running the same direction, but the direction alternates for each layer.
When selecting insulation and jacketing materials, choose materials with a high dielectric strength. A higher dielectric strength means a thinner wall can be extruded for less material in the way, making it more flexible.
Choose a 'soft' material with a 'shore a' durometer of 80 or lower. The softer the cable, the easier it will be to bend and flex. A thinner wall and softer material will increase the cable's suppleness.
Strength Members include steel, aramid fiber, or a stiff fiberglass rod that extends the center of the cable.
Strength members offer many benefits to the cable:
Aramid fiber, such as Kevlar® is a strong material ideal for extreme pulling strength while maintaining flexibility and flex life. Aramid fiber can be stranded in a variety of configurations to achieve differing levels of strength. For example, a bundle of four strands provides 450-600 Newtons of pull strength. While it is not rigid, it does offer high compressive strength without adding significant weight.
If aramid fiber is used in a cable solution, special attention must be given to the cable's termination, as incorrect termination can lead to weak points in the fiber. We have even seen cases where a customer comes to us with a competitor's cable assembly that is failing in the field because the strength member was never terminated, so it was not being put to use.
Separators serve as barriers between the cable's core components and the outer jacket material so that they do not bond together. Flex facilitating tapes such as PTFE or spun nylon will help increase both flexibility and flex life. These tapes can be wrapped in-line with jacketing and will help the cable flex without compromising the structure of the cable. It will also protect the cable from repeated flexing in a demanding, high flex life application.
Shielding provides protection by increasing both structural integrity and signal integrity. Selecting the right shielding materials and configurations can add strength, flexibility, and noise suppression. The primary types of shields include a foil shield, a box weave or basket weave braid shield, and a spiral shield. Foil provides a layer of shielding without adding a lot of weight or cost, but when high flex life is required, it may not be the best material. A spiral shield provides more flexibility, but may have a shorter life span in high flex environments. A box weave braid, while stiffer, will stay together throughout the flex life of the application due to its interlocking nature.
There are many options when it comes to terminating your cable to a connector especially when flex is a critical factor. An over-molded strain relief is going to give your assembly a much longer flex life than a boot. The over-mold will offer added protection from flexing near the connector or pulling that might occur from flex demands further down the cable. Additionally, a service loop inside the connector will offer a buffer, so that any pull on the cable will not immediately pull the conductors out of the pins.
Hopefully this article has you thinking about the requirements of your cable and different material options that may improve its performance. As you have probably gathered, flex, flexibility, and suppleness can be interpreted differently, so it is important to understand the needs of the end application to ensure a properly designed cable and assembly solution.
Additionally, if your current cable is underperforming, it is important to understand what is failing and where, so a cable designer can select the right materials to rectify the situation.