Design Decisions: Cable Carrier SpecificationDesign Decisions: Cable Carrier Specification
December 16, 2010
Any machine application involving constantrepetitive motion will benefit from a cable carrier system. To make the rightcable carrier decision for your design, be sure to consider the key decisionpoints outlined here.
Gatherdata. Before contacting a cable carrier vendor, gather all the necessarytechnical data. This includes length of travel, what cables or hoses will beinstalled, the size of cables and hoses and how much they weigh, and anyenvironmental factors such as debris, heat or chemicals, as well as speed andacceleration. Such data are critical, as the factors such as the largest cableor hose in your system will ultimately determine the minimum size of the cablecarrier. And be sure to account for proper clearance - add an extra 10 percentfor cables and 20 percent for hoses - to arrive at the minimum inner height ofthe carrier.
Access. Whenchoosing a carrier, make sure it allows for easy access to cables at any pointalong the carrier. Ideally, gaining access to interior cables or hoses shouldnot require the use of tools.
Cable Carrier Specification
Environment.If debris or other external conditions are an issue, tube-style cablecarriers with lids to fully enclose the carrier are essential, but even these shouldstill allow for easy access. Also consider whether the application isunderwater or comes in contact with liquids. In this environment, it isbeneficial to choose a cable carrier that is corrosion and chemical-resistant.
BendRadius. All cablecarriers have a predetermined radius stopping point on each link. When a numberof links are assembled, these stopping points restrict the carrier from fullypivoting and form a curve loop or minimum bend radius. All cable carriers havemultiple bend radii to choose from and all manufacturers suggest a minimum bendradius. The larger the bend radius, the less stress is placed on the cable andthe longer the service life will be. Bend radius is measured from the center ofthe curve loop to the center of the pivot pin on the side link. Do not confusethis with the dimension of the overall curve height.
Cable andhose packages. Sincethe primary function of a cable carrier system is to ensure cables bendproperly, it is imperative to install the conduits correctly. To ensure maximumcycle life for your machine, the easiest solution is to use cables designed foruse in a cable carrier.
Cable carrier length. Todetermine how long a cable carrier your application will require, firstdetermine the position of the fixed end. The ideal and most cost-effectiveposition is at the center of travel. This will require the minimum amount ofcarrier to achieve the necessary movement. Use the following formula todetermine the necessary cable carrier length: LK = S/2 + K (S = Maximum machinetravel distance; K = Curve length; LK = Carrier length; R = Bending Radius; I"M= Deviation from the center point).
Use this formula if the fixed end isanything other than the center of travel: LK = S/2 + a^+M + K
Acceleration and inertia. Itis critical to ensure that the cable carrier is strong enough to support theapplication. In order to determine if the carrier is strong enough, use thefollowing formula to determine the force required for your application:Acceleration Force + Push Force = Force Required. Acceleration force, which isrequired to keep the cable carrier moving once it has started, is calculatedby: Acceleration Force (lb) = Total Weight lb (carrier and fill) x Accelerationft/sec 2. Push force, which is required to get the cable carrier moving andovercome inertia, is calculated as such: Push Force (lb) = Total Weight x COFNote: The force required must be less than the maximum force for the selectedcarrier.
Accessories. Avariety of accessories should also be evaluated depending on the application,such as:
Interior separators or shelves to ensure proper alignment of the cables within the carrier and prevent friction, tangling and corkscrewing;
Mounting brackets to attach the carrier system to the machine itself;
Guide troughs for long-travel applications;
Rollers for even longer-travel applications;
Extender crossbars for oversized conduits; and
Strain relief to keep cables in position at both ends of the carrier.
JosephCiringione is national product and sales manager, Energy Chain Systems,igusInc.
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