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Bend radius 3xd

Minimum bend radius and cable bend radius -

Fundamentals, calculation and practice

White paper: 10 tips for selecting the right cable suitable for application requirements.

What is the bend radius?

The bend radius describes the radius in which a cable can be bent without damage. The key factor is the so-called neutral axis, meaning that the cable is positioned centrally within the chain.

Basic rule:
The smaller the bend radius, the higher the material quality must be and the individual cores must have an appropriate stranding design.

A simple example:
As in the human body, the stronger the bend, the greater the load. Exceeding the maximum permissible bending capability may result in damage.

Why is the right bend radius so important?

Incorrect selection of bend radii can have significant consequences:

  • Cable breakage or stranded wire breakage
  • Reduced conductivity
  • Mechanical damage such as cable & stranded wire breakage, corkscrewing
  • Reduced service life
  • Production downtime and costs
Check the minimum bend radius of the suitable cable directly in the online shopDownload a white paper with 10 tips to help you choose

Types of bend radii for cables

In practice, there are different applications:

1. Fixed bend radius

  • One-off bend during installation
  • Cable remains static
  • Usually defined by standards (e.g. DIN)

2. Flexible bend radius

  • Occasional movement
  • No sustained cyclic load
  • Also specified by standards

3. Energy chain radius

  • Continuous movement in machines
  • High number of cycles
  • Highest demands on materials and structure

Bend radius for energy chains (dynamic bend radius)

In energy chains, the ideal bend radius depends on the cable with the largest outer diameter.

Important rules:

  • The energy chain bend radius should always be ≥ the minimum bend radius of the cable
  • Larger bend radii significantly extend the service life
  • Cables must be laid in such a way that no kinks occur

What is the minimum bend radius?

The minimum bend radius is the permissible smallest bend radius, below which a cable must not be bent.

It is crucial for:
  • The service life of the cable
  • The operational reliability
  • The prevention of material damage
Manufacturers define this value based on:
  • Material
  • Structure of the cable
  • Conditions of use
  • Standards (e.g. ICEA, IEEE, DIN)
Effect of temperature on the minimum bend radius

The ambient conditions play a central role:

At low temperatures:

  • Material becomes stiff
  • Increased risk of breakage

At high temperatures:

  • Material softens
  • Increased abrasion and wear
Important:

Bending below the minimum bend radius often leads to premature failure.

Image with three light bulbs symbolising that a simple option has been found to calculate the bend radius using a rule of thumb

Calculating bend radius

A frequently used simple rule is:

Minimum bend radius = 10 × cable diameter

Example:
A cable with a diameter of 10mm → Minimum bend radius = 100mm

Note:
This value can vary depending on application, material and standard.

Best practices for selecting the correct bend radius

  • Never fall below the manufacturer's specifications

  • Choose the largest possible radius

  • Take into account the application (static vs. dynamic)

  • Take temperature conditions into account

  • Use special cables for tight radii

  • Guide cables neatly and provide proper strain relief

Special requirements for small bend radii

With very tight bend radii (e.g. < 5x diameter), conventional copper cables reach their physical limits.

Where are cables with a tight bend radius used?

The areas of application for cables with tight bend radii are diverse. They are particularly needed in applications where flexible and dynamic movements must be carried out in the smallest possible installation space. For example, they are used in the semiconductor and assembly industry, mechanical engineering, and the automotive sector. New application possibilities arise in automatic doors for vehicles and trains as well as in automatic self-service food vending machines and the packaging industry.

Cables with small bend radii
Dynamic applications with tight bend radii quickly cause the copper cores of conventional cables to meet their mechanical stress limits. Especially in areas of application that only have a small installation space but require a high number of strokes, special igus cables offer increased operational safety.

In addition to cables with conventional copper strands with a very short pitch length, igus also offers alloy conductors that can achieve bend radii of up to 3xd. In addition, cable jacket materials with exceptionally high abrasion resistance and flexural durability are used. With its many years of experience in its own test laboratory, igus can guarantee a long service life and planning reliability for chainflex cables with the smallest bend radii in energy chains.

Cable in motion
Cable test graph
Bend radius for cables in the energy chain
Bend radius for cables in the energy chain

Bend radius for cables under 3xd. For users of very small energy chains with mostly very narrow bend radii, the demand for a suitable cable for very high stroke numbers has come up frequently in the past. At bend radii of less than 5xd, copper quickly reaches its physical limits, which necessitated the search for suitable substitute conductor materials or for fundamentally different conductor superstructures. Alloys are used here. They have excellent mechanical specifications but reduced conductivity compared to copper. The conductor diameter of the alloyed conductor is a little larger.

Frequently asked questions about "bend radius"

Only up to the specified minimum bend radius. Exceeding this value can lead to damage.

This leads to material fatigue, cable breakage, or malfunctions.

Yes, among others, IEEE, ICEA and DIN specify guide values.

The maximum possible radius within the structural constraints.

Yes, extreme temperatures affect the flexibility and thus the permissible radius.

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I look forward to answering your questions

Nils Jäger
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