The spring element makes the chain more elastic without losing traction.

© Igus

The E6.29 energy chain variant, which was subjected to a long-term test with over 400 million complete bends in the Igus technical center, is equipped with such an elastic spring element. According to an expert opinion from the Cologne University of Applied Sciences, none of the connectors used exhibited any visible or measurable damage.

The spring element also supports the modular design of the energy chain. The links of the chain side sections can be quickly connected or disconnected by inserting or removing the springs, so that the cable carrier can be easily adapted to the individual requirements of the respective application, fitted with cables and assembled. The chain can be opened in both the inner and outer radius. A plastic hammer, a screwdriver and a few hand movements are all that is needed to drive the connectors in or out. Last but not least, the internal layout can be variably determined by using dividers and divider bars as well as insertion and intermediate shelves, which enables individual feeding and quick cable installation. And the additional use of base and cover elements means that the energy chain can be converted into a closed tube without the need for time-consuming conversion work, offering special protection against dirt, chips and other environmental influences.

The smooth running of a chain equipped with elastic spring elements is also reflected in low noise levels and a measured sound pressure level of just 37 dB(A), as confirmed by an expert opinion from TÜV Rheinland. Manufactured from the electrically conductive material 'igumid ESD', the spring elements can also ensure a permanently constant conductivity and thus discharge capacity if required.

The new generation of smooth-running energy chains has an even smaller pitch and features a 'brake' in the stop system.

© Igus

Another way to reduce vibrations in a machine tool is through special design solutions. One example of this is the arrangement of energy chains on top of each other, which can significantly improve milling accuracy in individual cases. In addition to these 'inherent' solutions, which change the system properties of the machine, additional systems can be integrated that specifically use external forces to minimize or completely avoid harmful vibrations by damping or eliminating vibrations. A distinction can be made between passive and active auxiliary systems:

In passive systems, the damping effect is achieved by converting the vibration energy by means of an additional mass body converting the kinematic energy into thermal energy or a relative movement between the bodies. In active auxiliary systems, an externally supplied auxiliary energy is used to generate an antiphase vibration. However, both methods always mean additional costs, precisely because the additional systems can usually only be realized as special individual system solutions and cannot be used across machines. In the future, therefore, attention should primarily be paid to the sources of vibration, i.e. the low vibration level of the machine tool components.

Technological outlook

The new E6.1 series is a further development of the E6 energy chain mentioned above. In addition to a smoother interior and a weight reduction of around 30 %, it also brings a further improvement in quality in terms of vibration behavior. Thanks to the smaller pitch and a 'brake' in the stop system in the form of a wedge-shaped contour in the e-chain stop, the sound pressure has been reduced by a further 2 dB(A). In addition, the geometry has been optimized, making the run even 'rounder' and virtually eliminating the polygon effect. Also new: the opening bars have been rounded off, as have the transitions from the chain link to the opening bar. All gating and marking points are now outside the chain cross-section. In this way, the contact surfaces and therefore abrasion and vibration have been further reduced. Even at higher accelerations and speeds, this further increases running smoothness.

Author:
Lukas Czaja is Head of Sector Management Machine Tools at Igus.

Energy chains in comparison

© Igus

A study by the Laboratory for Machine Tools and Production Engineering (WZL) at RWTH Aachen University has compared the vibration behavior of five different energy chains. Among others, the E6 energy chains and the 380 series from the E4/00 standard range from Igus were examined. With internal widths of 100 to 105 mm and internal heights of 42 to 52 mm, all the chains tested fell into the same size category. The test rig consisted of a base frame and a highly dynamic direct drive, which moved the linear motor-driven carriage (feed force 14000 N) at four speeds (25 m/min, 50 m/min, 100 m/min, 200 m/min) and with two accelerations (10 m/s², 20 m/s²) over the 800 mm travel distance.

The level of vibration was measured by acceleration sensors with a sampling frequency of 6000 Hz, which were attached to the carrier and the support trough of the energy chains. Separate measurements were taken for the outward and return travel of the carriage in order to avoid confusion of the measured values due to the two directions of movement. The signals recorded by the sensors were evaluated in both the time and frequency domains. In the time domain, the moving effect value (RMS value) is the measure of the vibration energy at the point of measurement.

For all energy chains, the greatest vibration energy was found at the support trough in the direction of the applicator axis (z-axis). Accordingly, the comparative study concentrated on these maximum vibration signals in the z-direction. The different accelerations of 10 m/s² and 20 m/s² had no significant influence on the vibration values of the energy chains.

For the two Igus chains tested, an average 28% lower vibration value was measured than for the other cable carriers. They also exhibited a maximum effective value of around 4 m/s². The 'most vibrating' cable drag chain in this respect had a value of 5.6 m/s², which was 40% worse.