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igus® inc.

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RI 02914

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Unsupported, short travel applications

Definition: Unsupported

If the upper run of the energy chain operates without touching the lower run over the entire travel, it is called an unsupported application.

Definition: Unsupported Length

The distance between the cable carrier's moving end and the beginning of its radius' curve is called the Unsupported Length. It is always dependent upon the type of cable carrier and the fill weight.

Unsupported cable carrier Example for unsupported straight FLG

The "FLG" type of installation always generates the longest service life and can be operated with the maximum values for speed and acceleration.

Cable carrier unsupported length FLG unsupported straight length
Unsupported cable carrier sag FLB unsupported length with sag

Unsupported applications

The "unsupported" application is the most common. igus® energy chains are very well suited for high dynamics and long service life. The maximum unsupported length is dependent upon the fill weight and the type of cable carrier. As a result, we differentiate among three types of unsupported length:

A) Unsupported with straight upper run (FLG )

The "FLG" energy chain applies when the upper run either has camber, is straight, or has a maximum of 0.39-1.97 inches (10-50 mm) sag, depending on the size of the cable carrier. The "FLG" type of installation is always preferred. The energy chain runs quietly and is not exposed to any additional vibration.

B) Unsupported with permitted sag (FLB)

The "FLB" energy chain applies when the sag amounts to more than 0.39-1.97 inches (10-50 mm), depending on the cable carrier size, and less than a defined maximum sag. This maximum sag is dependent on the type of cable carrier. The "FLB" application is technically permissible in many cases. It becomes problematic if the acceleration and the travel frequency are high.

C) "Critical sag"

If the sag is greater than permissible for "FLB", then we refer to it as "critical sag." An installation with critical sag must be avoided or reserved for extreme circumstances. An energy chain should never be installed with critical sag. There are applications which, after a very long period of use, reach the stage of "critical sag." The cable carrier should be replaced at that time. Please contact us if your application reaches critical sag.

Three types of unsupported length

Unsupported cable carrier with sag Example of unsupported with FLB sag

Unsupported Length

For every igus® cable carrier, the"FLG" and "FLB" values are essential for:

Finding a suitable energy chain for your fill weight and travel distance

Identifying the maximum load for the selected energy chain

The following important factors should be considered to select the correct energy chain

Unsupported Length



Service life

Load bearing areas

Noise level

Technical environment

What to do if the unsupported length is insufficient?

If your application, fill weight and travel fall outside the "unsupported length" parameters of the desired energy chain, you have the following options:

Select a more stable energy chain

Support the cable carrier in the unsupported area (this possibility has restrictions for acceleration, speed and noise as a consequence; three fundamental examples are detailed below. Please consult igus® if you are considering this possibility. We will gladly provide you with a detailed proposal.)

Use a "multiband" cable carrier or "nest" two energy chains inside one another. (Please consult igus® regarding these options.)

Design the travel distance as a "gliding application".

Supported cable carrier sag Series 28 with support in the FLB area
Supported cable carrier sag Support of the FLG area. The overall straight, unsupported travel can be increased along the upper run by a maximum of 50% of the FLG and along the lower run by a maximum of 100%.
Cable carrier sag supported Support of the FLB area. The overall travel distance can be extended to a maximum of 100% from FLB.

Speed, acceleration and service life

For unsupported applications, the acceleration (a) is the critical parameter. High acceleration can cause the cable carrier to vibrate and reduce its service life. This is a particular danger if the cable carrier already has a sag greater than the FLG value. Maximum values for acceleration, speed, and service life are achieved only with cable carriers incorporating the FLG design. FLG designed energy chain systems can sustain very high loads. To date, a peak acceleration of 2,572 feet per second has been achieved during continuous use. Through ongoing testing in the igus® laboratory and from practical experience, standard values for service life have been formulated (see graphs). Our tests confirm that these standard values apply to all igus® energy chains and E-Tubes. It is crucial to determine whether the application will be designed as unsupported straight FLG or unsupported, with sag FLB.

Standard values of max. speed (v) and acceleration for unsupported lengths

    FL G FL B
v max. ft/s (m/s) 32.8 (10) 9.83 (3)
v peak [ft/s] 65.6 (20) -
a max. ft/s 2 (m/s2) 65.6 (20) 19.69 (6)
a peak ft/s 2 (m/s2) 2,572 (784) -
Standard value of FLG service life: 10 million cycles

Service life for unsupported straight applications Standard values on service life for FLG, (unsupported straight), dependent on acceleration
Service life for unsupported sag applications Standard values of service life for FLB, (unsupported sag), dependent on acceleration

Preferred series for max. speed and acceleration

Load-bearing surfaces

Unsupported energy chains normally require some type of surface on which the lower portion of the cable carrier runs. A wide range of configurations is available, as the drawings on the right demonstrates. Many material options are feasible: metals, polymers, stone, wood, concrete, glass, etc. We also have solutions to minimize the noise generated by the cable carrier’s lower portion. Please consult igus®. When selecting the running surface, be sure dirt and debris cannot collect in the cable carrier's path.

Cable carrier surfaces and guide troughs Different surfaces and guide troughs are possible

Mounting brackets

We recommend pivoting mounting brackets as standard for unsupported applications. Pivoting mounting brackets compensate for the camber, can be installed more easily and decrease the load on the first energy chain link in operation. Exception: if the acceleration is greater than 66 ft/s² or if the height is limited to the HF measurement, locking mounting brackets keep the energy chain under the HF measurement.

cable carriers

We recommend pivoting mounting brackets as standard. We recommend locking mounting brackets as standard if high speeds > 217 ft/s (66 m/s) or accelerations > 217 ft/s² (66 m/s²)

Unsupported lower run

energy chains without support along the lower run have restricted use. The value FLU usually must be determined in a test by igus®. The maximum permissible amount of the projection depends on the fill weight, the selected energy chain, the dynamics, and other factors, because the various combinations of these parameters can produce very different results. If the lower run of the energy chain cannot be supported over the whole travel, please consult igus®.

Partially unsupported cable carrier Series 40 energy chain partially unsupported. Please consult igus® regarding this type of configuration.