BASICS OF CABLE CARRIER SYSTEMS
A cable carrier guides and protects automated cables and hoses on all types of industrial machinery and equipment. The carrier is a structure which surrounds the cables and hoses, moving along the travel to maximize the life of these conduits. A cable carrier can take many forms (an open style chain, snap-open chain, fully enclosed tube) and is available in a variety of materials (all-polymer, hybrid polymer/metal, all-metal). Individual manufacturers even refer to this carrier element using different terms (cable carrier, cable management system, guidance track, etc.). The universal function of a carrier is cable guidance and protection, but construction method, material use and product range varies from manufacturer to manufacturer. Final selection is usually determined by the longest life at the best price. In order to make this choice, it is important to be aware of all that is available.
Construction techniques for a cable carrier vary from one type to another, but the most basic carrier design to make up one carrier link consists of two side plates, an inner radius crossbar or lid and an outer radius crossbar or lid. If the carrier is "modular" or interchangeable with other carrier components and made to snap open for conduit accessibility at any point along the carrier, this will total four separate parts, at minimum.
If the carrier has a zipper style or snap-on crossbar opening along one radius, the components are reduced to two parts, one U-shaped element consisting of the two side links and one molded-on crossbar and one separate crossbar or lid.
If the carrier does not need to open for conduit accessibility at all, the carrier link consists of just one element involving the two side plates and the two crossbars, all injection molded in one piece.
Some carrier links are manufactured with more components, such as connecting bolts, rivets, separate glide shoes, and separate bend radius determination elements, but the most advantageous designs keep the individual elements down to a minimum (four or five at most). The reasoning behind this is that the fewer elements involved, the stronger and more stable the carrier, because there are fewer connection points to inherently weaken the carrier. Use of fewer elements also improves handling by requiring fewer tools (ideally just a screwdriver if not by hand) and minimal time spent in assembly and disassembly. Also, generally speaking, the fewer the parts, the less expensive the unit. Other crucial elements included in the makeup of a complete cable carrier are separators, shelves, strain relief, mounting brackets, and connectors.
The different basic carrier materials available are all-polymer, all-metal or a hybrid of the two (usually polymer side plates with metal crossbars). Within these options, there are many blends available which affect the performance of the carrier under various environmental conditions. For example, some carrier makers offer special polymer material blends for carriers used in cleanrooms, those used in outdoor applications or those in radioactive settings. In fact, two or more manufacturers can offer all-polymer carriers with the same basic description of "fiber-reinforced nylon" which are actually very dissimilar in terms of integrity and strength, as well as other properties, based on the percentage of the fiber content, the preparation process for molding, the parameters of the injection molding machine, such as cycle time of the molded part, whether or not recycled materials are used, and many other factors. As a result, it is hard to say there is one industry-standard polymer.
One all-polymer cable carrier manufacturer (igus, Inc.) has created its own standard polymer material blend (igumid G) which is claimed to work in all of these environments without wear, particulation or degradation. Derived from polymer bearing technology, it meets Class 1 cleanroom standards. Special blends of polymers, such as for low-wear or which are electrically conductive, are also available for use in particularly demanding applications such as particularly demanding cleanroom situations and an material for applications such as mining and demolition site equipment.
The harder, stronger, sturdier polymer material, in conjunction with newer carrier link designs (developments in the connection between side plates and crossbars), has allowed all-polymer carriers to replace hybrid and all-metal carriers in most applications. Where metal carriers were traditionally chosen exclusively for oil rigs, ship-to-shore machinery and other outdoor equipment, all-polymer cable carriers can now be used. Their benefits in such applications include their comparatively light weight, easy installation and conduit maintenance, and built-in corrosion resistance.
Recent developments in all polymer carriers include double-locking mechanisms (patented by igus) that allow the carrier to be separated easily with the right tool but with no chance for accidental separation during operation. adds to the stability of the all-polymer carrier by ensuring easy separation with the right tool when desired without the fear of accidental separation during operation. The new design targets applications traditionally incorporating hybrids or other types of carriers.
Cable carriers come in a wide range of sizes and carrying capacities. Among the smallest is the igus E04 "pico," a polymer carrier with an inner height of 0.26 in. and an inner width of 0.28 in. Typical applications are those involving miniature power supplies as used in sensitive measuring equipment, medical equipment, and printing machinery.
The largest polymer cable carrier currently on the market (igus Series 800 "Mammoth") features an inner height of 7.87 in., an inner width range of 7.87 to 23.62 in., and the capacity to carry heavy-duty loads. Typical applications are in steel mills and offshore equipment, replacing metal carriers.
Many factors are involved in deciding which cable carrier to use for a specific application. Whichever type of carrier is ultimately selected, the various components in the system (the carrier, cables and/or hoses, mounting brackets, connectors, strain relief, and separation elements) need to work together well. It is possible to find vendors willing to serve as a single source for all these elements.
Selection issues
One of the most common failures that crop up in automation projects concern the energy supply cables or hoses. These cables often see constant cycling at high speeds with small bend radii. They also must have an abrasion-resistant outer jacket, even when two cables sit directly on top of one another with no separation, and conductors must be configured correctly within the jacket. Cables lacking such safeguards can corkscrew or deform irrevocably.
The threat of corkscrewing increases with higher automation speeds. Problem is, many cables that work fine at lower speeds and cycles cannot handle faster automation. The cable carrier sometimes gets blamed for such failures when, in fact, there are many factors involved.
Over-packing the cable package can lead to deformation and/or breakage of the carrier crossbars and links. Avoiding such difficulties involves selecting the right cables, the proper cable carrier (both size and type) and the correct peripheral components. Many companies go to a single supplier for all these components as a way of ensuring they all work well together.
For example, one cable carrier manufacturer developed its own line of flexible cables and air hoses specifically for use in cable carriers. Some cable carrier makers also offer in-house harnessing services, including purchase of any components they themselves do not manufacture. The larger manufacturers can provide multiple options for cable and hose accessibility (snap-open, zipper or push-through crossbars and snap-open lids on carriers), a variety of conduit strain relief and mounting options, a large selection of sizes, different price options for the same application (with a good explanation if one system is recommended over another), and various service options.