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Moving cables generate particles, but only recently has this phenomenon been quantified.
In clean rooms, it is imperative that dust and particulates be eliminated to a high degree. But particulates are problematic for clean-room cable systems that flex or rub up against other items.
In that regard, cables for motion -control equipment sitting in clean rooms are especially prone to throw off particulates. For one thing, cable movement within the cable chain contributes to particulation. Second, the amount of force placed on cable surfaces can cause particulation at those critical points - whether the force is caused by continuous flexing or arises from the weight of the cables themselves.
For these reasons, cable systems for clean rooms must be designed to reduce friction to keep particulation down. And reducing friction improves cable performance and life. Remarkably, there has not been a lot of third-party testing to verify particulation behavior in cables.
Recently we contracted with the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Germany to measure the particulation of cables and cable chains for ISO clean- room certification. Fraunhofer tested Gore flat cables inserted in two different cable chains and a set of two round cables in a low-vibration cable chain. The round cables were constructed with a lowparticulation jacket material. In addition, tests covered Gore selfsupported flat cable, which does not need a cable chain. Several interesting facts emerged that have a direct impact on cable management, particularly with respect to cable movement and velocity.
Round-cable movement
Round cables must be prevented from generating particles, they can't move within the chain. Otherwise, they tend to rub together and shed particles. Any movement results from both the acceleration of the cable chain and friction between the cables and the cable-chain components.
The conductors within the cable also move from the flexing motion energy which results in twisting, kinking, and walking. If the friction between conductor insulation, cable shielding, or jacketing is sufficiently high, the conductors creep within the cable. This action can result in kinks and a ruptured cable jacket. Such movement of the conductors causes round cables to corkscrew, which, in turn creates particles and causes conductors to fail.
The general rule of thumb for cable-chain designers is to allow space...