Cables are really the lifelines of any machine. They supply the power, data, etc. to the right components, and without them, nothing works. So why let cables take the abuse of rubbing, tangling, pulling, and bending when you can protect them easily with a cable carrier system?
Cable carriers guide and protect the cables and hoses on moving machinery. They prevent tangling and damage from debris or contact with the machine itself. Using cable carriers can extend the service life of both your cables, and the machine itself. Any application that involved moving machines and repetitive motion will benefit from a cable carrier system. They’re used on applications ranging from machine tools, automated robots, in cleanrooms, and on ship-to-shore cranes.
igus has it’s own line of cable carriers, called Energy Chain Systems. They are made entirely of plastic, so they are light in weight, and they are also maintenance-free and resistant to corrosion and wear. Plastic Energy Chains can replace metal or steel carriers in almost any application. They are available in a wide variety of sizes and styles; from micro-chains for very small applications, E-Z Chains for quick assembly, special chains for very low noise and vibrations, and even fully enclosed tubes for applications with flying debris, and multi-axis carriers for robotic applications.
Cable carriers are often forgotten in the design process – but shouldn’t be!! The cable carrier is a crucial part of any machine’s design, and should be considered early on in the design stages. They can be implemented to move in a variety of ways, most commonly in a horizontal, unsupported run with a short travel length. (See image below Left) In an application like this, the upper span of the carrier operates without touching the lower run throughout the entire length of travel. The maximum length that can be unsupported is different for each application, but an unsupported application will have the longest service life.
In the travel length is too long to be unsupported, the cable carrier can run on itself in a gliding fashion (See image below Right). Just a note- in a gliding application like this, a guide trough and glide bar should be used.
Choosing the Perfect Cable Carrier
There is a huge variety of cable carriers available, but which one would be best for your application? Follow these guidelines to choose the best fit your your application.
1. Gather Your Data
Before jumping to purchase and install a cable carrier on your machine, its necessary to gather all the technical data first. This includes your application’s length of travel, what cables or hoses you’re planning on installing in the carrier as well as their weight, and environmental factors like debris, heat, chemicals, speed, or acceleration.
2. Find the largest cable/hose in the system
The first question any cable carrier manufacturer will ask when you’re planning your carrier system is “What’s the largest hose or cable in your machine?” This will determine the minimum size of the carrier. To the diameter of the cable or hose, we add space to ensure proper clearance – 10% for cables and 20% for hoses – and the result is the minimum dimensions for the inner height of your carrier.
3. Style, style, style
The next decision is about what style carrier would work best in your application. Its recommended that you choose a carrier that snaps open whenever possible, allowing easier access to cables at any point along the carrier. If debris or other external conditions can be an issue, tube style carriers replace the link crossbars with lids, for a fully protected system. This is especially useful in applications where woodchips, metal shavings or other debris may be present. igus has created cable carriers with special features like split crossbars, zipper-like closure systems, or hinged crossbars. These are all styles that allow for easy installation and replacement of cables and hoses as needed, minimizing assembly and disassembly time. Carriers are also available for heavy-duty applications with long travels, using hinged crossbars that open from either side for flexible access as needed.
4. Consider the Environment
The environmental conditions of an application are a good way to determine what style of cable carrier to use. If debris is present, like woodchips or metal shavings, or if the carrier is operating in a contaminated area, an enclosed tube is your best bet. An open crossbar carrier system is great for easy inspection and replacement of cables in applications where this is a common occurrence. You should also consider whether the application is underwater or comes into contact with liquids or chemicals.
5. Bend Radius
All cable carriers have a predetermined radius stopping point on each link. When several links are assembled these points restrict the carrier from fully pivoting, forming a curve loop or minimum bend radius. Cable carriers have several bend radii to choose from, and the manufacturers typically suggest a minimum bend radius. Generally, the rule is 8-10 times the outer diameter of the largest cable or hose in the system. The larger the bend radius, the less stree placed on the cables, and the longer the service life will be. Just a note: the bend radius is measured from the center of the curve loop to the center of the pivot pin on the side link – don’t get confused and measure the overall curve height!
6. Cable and Hose Package
Since the purpose of a cable carrier system is to ensure that cables bend properly, then it is imperative to install the conduits correctly! To ensure the best possible service life in your machine, its recommended to used cables that have been specifically designed to use in a cable carrier, like igus’ Chainflex continuous-flex cables. Special features like a strain-relieving core and special jacket and shield designs ensure that these cables will be able to complete millions of cycles without failure in continually-moving machines.
7. Cable carrier length
To determine how long your cable carrier needs to be, first determine the position of the fixed end of the carrier. Ideally (and most cost effectively,) the fixed end should be positioned at the center of travel. This requires the least amount of carrier to move the necessary distance.
8. Acceleration and Inertia
It’s essential to ensure that the cable carrier you choose is strong enough to support your application. If it isn’t, the results can be devastating – a carrier can literally be snapped in two if the overload is great enough. To make sure your carrier selection will do the job, use the following formula to determine the force required to keep your application up and running:
First, determine the acceleration force. This is the force required to keep the carrier moving once it’s started.
Acceleration force (lb) = Total Weight lb (carrier and fill) x Acceleration ft/sec2
Then determine the push force, or the force required to get the carrier moving and overcome inertia.
Push Force (lb) = Total Weight x COF
Once these two values are determined, calculate the force of the application by adding them together: Acceleration force + Push force = Force required.
The force must be less than the maximum force for the cable carrier selected. Carrier manufacturers typically don’t publish the maximum force allowance for their products, but igus technicians will calculate the force your application requires, and help you select the best carrier to meet these requirements.
A variety of accessories are available to further facilitate the energy supply system for your machine, including:
Interior separators and shelves to properly align cables and prevent friction, tangles or corkscrewing. These are available in horizontal or vertical layouts (See above image).
Mounting brackets, which are almost always needed to attach the carrier to the machine. Plastic or steel brackets are available in one-piece designs for small carriers. Others have aluminum bushings in the bracket to prevent damage when tightening bolts. These can either pivot for most applications, or lock into place for vertical or side-mounted gliding applications.
Guide troughs are available for long applications, and for even longer travels, available rollers can be used.
Extender crossbars are available is oversized conduits are needed.
Strain relief is a common way to keep cables in position at either end of the carrier. Sometimes, strain relief is only needed on one side, and other times both side should be relieved. Strain relief can be made up of rails, clamps, or wraps. Imporper strain relief is a very common cause for failure, and while it may seem insignificant, can often make or break the success of an application.
To learn more about igus’ Energy Chain cable carrier systems, visit the E-chain page at igus.com/echains.