By Eileen Harvey
In modern industries, cables are the silent workhorses powering automation, robotics and smart factories. While they may seem like simple components, the way cables are installed and used directly impacts system reliability and downtime. Two of the most critical factors for cable performance in continuous-motion applications are bending radius and flex-life.
Ignoring these parameters can lead to premature cable wear, signal loss and costly machine downtime. On the other hand, selecting cables with the right construction and installing them properly can extend their lifespan by years, saving significant operational costs.
Understanding Bending Radius
The bending radius of a cable is the minimum radius it can bend without being damaged. If a cable is bent too tightly, the internal conductors, insulation or shielding can break down, leading to signal degradation or total failure.
Factors Influencing Bending Radius
There are three main factors. The first is cable construction, whether you use flexible stranding or solid conductors. Second is jacket material, as PVC, PUR and TPE jackets have different flexibility. The third factor is application type—fixed installation vs. continuous motion.
Standard guidelines are, typically, six to eight times the cable diameter for fixed installation and 10 to 12 times the cable diameter for dynamic applications (drag chains/robots). For example, a PROFINET cable with an 8mm outer diameter should maintain a bending radius of at least 80mm in a drag chain application.
What is Flex-Life?
Flex-life refers to the number of bending cycles a cable can withstand before failing. In continuous motion systems, such as robots and conveyors, cables often undergo millions of bending cycles. Flex life is tested using flex testing machines to simulate bending underload. Also, torsional testing checks cables that rotate or twist.
Materials That Improve Flex-Life
Fine-stranded conductors are more flexible and less prone to breakage. PUR jackets are excellent for high-motion and have oil and chemical resistance. TPE jackets withstand extreme temperatures while remaining flexible.
For applications like robotic arms, where cables twist and bend constantly, choosing a cable with proven flex-life performance is essential.
Relationship Between Bending Radius and Flex-Life
Bending radius and flex-life are directly related. The tighter the bend, the greater the stress on the conductors and insulation, which shortens flex-life.
Imagine bending a paperclip back and forth: the tighter the bend, the faster it breaks. Cables behave the same way. Maintaining proper bending radius allows cables to survive millions of cycles without damage.
An example is robotic cables, which are designed for torsional stress with flex-life of up to 20 million cycles. Another example is drag chain cables, designed for repetitive flexing with cycles exceeding 10 million when properly installed.
Best Practices for Proper Bending Radius
Following proper installation practices significantly extends cable lifespan:
- Follow Manufacturer Guidelines – Always check datasheets for minimum bend radius.
- Use Drag Chains – Support cables in continuous motion systems.
- Avoid Kinks – A single kink can permanently weaken a cable.
- Neutral Axis Placement – Install cables so they move evenly inside a track, not stretched on one side.
- Allow Slack – Avoid tension; cables should move freely.
Enhancing Flex-Life in Continuous-Motion Applications
Choosing the right materials and techniques makes all the difference. Key enhancements are jacket materials, shielding techniques and proper installation.
Jacket materials include PVC, which is best for cost-sensitive, fixed applications; PUR, ideal for oil, abrasion and flex-heavy environments; and TPE, which handles extreme flexibility and wide temperature ranges. Shielding techniques are braided and foil shields to prevent EMI without reducing flexibility. For proper installation, ensure cables are not compressed or forced in cable carriers.
Common Mistakes to Avoid
Exceeding the recommended bend radius can lead to conductor breakage and eventual cable failure. Using rigid cables in dynamic applications often causes premature wear and damage due to repeated movement. Improper cable routing that results in twisting or tangling will shorten the cable’s flex-life and reduce performance. Ignoring the need for EMI shielding can compromise signal integrity, especially in high-motion industrial environments. Overstuffing cable tracks limits flexibility and accelerates wear, leading to reduced system reliability over time.
Real-World Applications
In robotics, cables must endure continuous torsional and flexing cycles without performance loss. Packaging machinery operates with high-speed repetitive motion that demands durable and flexible cables. CNC machines present harsh conditions involving oil, vibration and heat that require rugged designs. Within Industry 4.0 and smart factory systems, reliable data transfer using PROFINET or other Industrial Ethernet solutions is essential to maintain seamless automation.
Practical Tips
Selecting PUR-jacketed PROFINET cables is ideal for environments that are highly flexible, oily or abrasive. Data and power cables should be separated to minimize EMI interference. Always verify the minimum bending radius before installing cables in drag chains to prevent mechanical strain. Regular inspection of cables helps identify early signs of wear and prevents costly downtime.
Recommendations
For robotic systems, TPE or PUR jackets provide the best flex-life and durability. Packaging machinery performs most effectively when equipped with drag chain-rated cables designed for repetitive motion. For general automation applications, L-com PROFINET cables deliver reliable performance and long service life.
Facts Section
- A cable bent below its recommended radius can fail 70% faster.
- PUR cables can last up to 5× longer than PVC in continuous flex.
- A proper bend radius can extend cable lifespan by up to 40%.
- Robots in automotive factories use cables rated for >20 million flex cycles.
The success of continuous-motion applications depends heavily on respecting two cable parameters: bending radius and flex-life. Selecting the right jacket materials, following installation best practices and avoiding common mistakes can dramatically increase cable lifespan and reliability.
By investing in quality cables and proper installation, industries can prevent costly downtime and maintain smooth operations in the era of Industry 4.0.
Explore the full range of TKD Kabel through L-com. We’ll fill your orders fast, with same-day shipping on all qualified, in stock, online orders received Monday through Friday before 5 p.m. EST. For TKD-related inquiries, connect with our U.S-based TKD expert Eileen Harvey at eharvey@infiniteelectronics.com.
