Machine Design

Cable Carriers Smooth Machine Motion

Following guidelines for cable and hose carriers helps streamline the selection process.

Bart Bohne
Gortrac Div.
A& A Manufacturing
New Berlin, Wis.

Cable carriers come in many design configurations, sizes, and materials. They are typically assembled from off-the-shelf components, allowing manufacturers to quickly and economically tailor a design to an application.

Open nonmetallic link-type carriers are often used in applications that feature high speeds or long travel lengths.

Completely enclosed nonmetallic carriers economically protect hoses and cables from damaging environments. Easy-to-remove plates on this design allow quick access.

Metallic link-type carriers are typically used on machine tools, industrial robots, construction equipment, and steel-mill machinery.

Conduit-type carriers keep chips, weld spatter, and oil from interior components.

Cable and hose carriers provide an easy way to keep electric, hydraulic, pneumatic, and other lines in proper position on moving machinery. This protects them from premature wear and fatigue due to flexing and abrasion. Instead of allowing cables and hoses to twist and kink, they maintain the proper bend radius and impart a more gentle rolling action that feeds lines in and out as a machine moves back and forth.

Although the devices appear simple, selecting the right one can be more complex than it seems. The wide variety of designs, materials, and sizes available makes it important to work closely with the manufacturer to ensure the optimum combination of proper performance and long life. Here's a closer look.

Application essentials
While they are assembled mainly from off-the-shelf components, carriers are made in many design configurations, sizes, and materials. The bad news is that simply picking one out of a catalog is not likely to provide the best possible solution. The good news is that manufacturers can quickly produce customized carriers priced on par with standard units. The service conditions and physical configuration of each application require some engineering analysis that is often best provided through the manufacturer.

To work effectively with the carrier experts, start by gathering all available information about the application, including physical characteristics, service parameters, and environment. Design information includes cross-sectional size, carrier radius, travel length, and any high-clearance limitations. Other important parameters include the number and type of cables or hoses, travel speeds, and environmental conditions.

Cross section of the carrier should allow 10% clearance around cables and 20% clearance around hoses to prevent binding. Group components with similar diameters and services and use separators to keep unlike components apart. The carrier's minimum bend radius should equal or exceed the recommended minimum bend radius of the stiffest cable or hose it will carry. Cable and hose manufacturers typically publish accurate minimum-bend specifications. When this information is not known, the recommended minimum carrier radius is generally eight times the diameter of the largest cable or hose.

Carrier length may vary depending on mounting and machine configurations, but typically length is approximately half the total travel plus the curve length. Also calculate total weight per foot of the cables and hoses within the carrier, including the weight of any liquids the hoses contain.

Sorting out carriers
Most cable and hose carriers consist of parallel side links joined by parallel crossbars that support the hoses. Pivot pins and strips allow the links to travel through a predetermined arc. Some link-type designs are completely enclosed, while others are open between the links. Another variety, usually made of metal, is the conduit-type design, which is completely enclosed but does not use links.

Open nonmetallic, link-type carriers, available in a broad range of sizes and designs, are the first choice for most applications where high speed and long travel are factors. Made of heavy-duty fiberreinforced nylon, they are nonconductive and corrosion resistant, particularly when they incorporate nonmetallic pins or bars.

Typical uses include machine tools, industrial robots, and other moving equipment. Some lighter designs are particularly suited for light automation machinery and for applications where quiet operation is important. To accommodate these applications, nonmetallic carriers are available in a wide range of sizes from less than 1-in. wide for use with ribbon cables to others that handle cables and hoses larger than 4-in. diameter. Some types accommodate travel lengths exceeding 300 ft.

Various types of bars connect the two linked side members and provide support. Some designs offer optional hinge or snap-out bars that allow quick access and make it possible to install cables and hoses with fittings that cannot be fed through the carrier. Other options include separators, used to keep dissimilar cables and hoses apart, and poly rollers that reduce wear caused by relative motion of cables and hoses. Some nonmetallic carriers feature replaceable bearings for applications where heavy use or a harsh environment causes excessive wear. Window extenders, which add more vertical room to the carrier, and low-friction sliders, which reduce wear and load on extremely long travels and fast speeds, are also available with some nonmetallic carriers.

Completely enclosed nonmetallic carriers have a link-type design with an enclosed top and bottom to economically protect hoses and cables in damaging environments. They work well at high speeds and, with proper guiding, can be used for travel lengths exceeding 300 ft. The enclosure method varies, but several designs allow easy access to cables and hoses with removable slide strips or plates.

Lighter designs that combine high travel speeds, nonconductivity, and smooth, quiet operation are well suited for packaging machinery, printers, and robots. When cleanliness is a concern in such applications, carriers are available that generate little dust or particulate matter.

Metallic link-type carriers are designed for applications that include machine tools, cranes, industrial robots, mobile and construction equipment, and steel-mill machinery. In many designs, hardened steel pins join the metal links and provide both a bearing and lock point. One new design features a half-shear lockout system that eliminates parts, adds strength, and reduces costs. Many metallic link carriers are now designed without pinch points to eliminate hazards to operators. Some types use metal links with nylon or aluminum bars to combine the strength and ruggedness of steel carriers with the light weight of nonferrous materials.

Optional features add to carrier capabilities. For instance, window extenders add more vertical space for cables. Cables may be supported by bar carriers that join the side links or by machined carriers designed to fit a particular combination of hose and cable sizes.

Conduit-type carriers are formed with small convolutions designed to keep chips, weld spatter, coolant, cutting oil, and similar contaminants away from control cables, power cables, and hydraulic and air hoses. The totally enclosed design also improves machine appearance and provides quiet movement. Because the carriers are not restricted by the motion of individual links, they can operate at the higher speeds needed for applications such as robotics. Low weight and vibration-free movement also makes them suitable for applications that require fast accelerations.

Typical construction is heavy-duty, galvanized steel supported on a stainless-steel band attached to the carrier underside. Some offer a black oxide finish. Standard conduit-type carriers can be used at travel speeds to about 200 fpm, and in ambient temperatures from 20 to 180°F.

Additional details
Guidelines for deciding between metal and nylon carriers include the following. Use metal with heavy loads or temperatures exceeding 250°F, and nylon when speeds exceed 600 fpm. Metal carriers are practical for travel lengths to 50 ft. Beyond that, nylon may be more economical. Also consider appearance and open or closed construction.

Carrier size varies with type and construction. Interior dimensions range from widths smaller than 0.5 in. to as large as 14 in. high and 36 in. wide.

Mounting brackets are available in a variety of configurations. They are usually furnished as an integral part of the carrier and must be specified when ordering.

Support trough systems are sometimes required for nonmetallic carriers when total travel length exceeds the design's maximum free-carry potential. For many applications, some sag is acceptable. But experts recommend a support trough where applications involve long travel and high speeds. Manufacturers offer carriage-support systems for metallic-link carrier applications that require higher cable/hose loads and high travel speeds. They consist of major rollers and intermediate carrier supports over the entire travel length. The system rolls on channels mounted to the floor or crane bridge and allows speeds to 450 fpm for overhead crane applications.

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