The perfect fit
By Irene Barber

The "why" and "how" of the world of custom-built cables

Irene Barber is president of elocab Tailor-Made Cables, the Canadian branch of elocab Sonderkabel, a leading European manufacturer of custom-made cables.

To most of us, buying custom-made no longer has the appeal it had for our forefathers. They didn't think twice about having a suit or a pair of boots made to order. Today, buying "off the rack" is most often the first option people look at.

In the cable world, using custom-made is, in many cases, the better business decision; often the only sensible choice, in extreme operating conditions. Increasingly, custom-made cables are seen as the optimum solution for the tough and challenging jobs, where cabling is exposed to moisture, pressure, constant movement, corrosive agents, extreme cold, heat or electromagnetic interference.

Imagine bending the printer cable from your computer in the same place, say, ten million times. Would it still work flawlessly after one million or more bending cycles? Custom-made power and control cables for robots at assembly lines have to be able to withstand that kind of repetitive flexing - and still deliver the power and the correct "commands" without failing.

This isn't to say custom-made is about to displace standard. Generally, standard cables will do just fine. Tailor-made cables are, and always will be, niche products. However, there are so many more niches for them today.

What is a tailor-made cable?

Whereas standard cable is manufactured in bulk and sold from catalogues or by order numbers, each custom-made cable is a unique product. It is designed, manufactured and tested to match each customer's specifications. Standard cables are generic; custom-made cables are created for specific applications or situations. It might be just one cable of many on a machine - the one cable that has to be especially thin, or resistant to very high heat, or have a high-flex capability, like cables for welding, paint-spray or handling robots.

Every custom cable begins with an in-depth analysis of the specific application needs. That usually means detailed consultation with the customer or even on-site reviews. At elocab, each custom cable is designed from scratch using the latest CAD technology. In average, our design engineers create a total of eight new cable constructions daily, for diverse applications.

Custom cables are not just for big jobs or big customers. At elocab, we design and build tailor-made cables in quantities as small as 100 meters, with analysis-to-delivery lead-time of no more than three to six weeks - a quick turnaround to enable responding to more and ever-newer applications.

Companies and institutions are increasingly opting for custom-designed cables for a simple reason: Each custom application gives the buyer an advantage or set of advantages that, over time, more than recoups the upfront cost of buying a designer product. Tailor-made cables end up paying for themselves through increased efficiency, reduced downtime and substantially longer service life than conventional cables. They can help optimize the performance of state-of-the-art production facilities or diagnostic equipment.

A company's operating costs and maintenance expenses are lowered because the cables are designed for greater longevity and reliability. In the just-in-time world, a production halt due to cable failure means lost output, idle workers, and an accumulation of inventory and unfinished product. For these reasons, custom cables have become the rule in automated manufacturing environments. In Europe's automotive industry, for example, 80 percent of all welding robots rely on tailor-made, high-flex cables designed and built by elocab's parent company in Germany.

Custom cables are viewed as essential in extreme operating conditions demanding the highest levels of reliability, such as in Europe's high-speed trains or in submarines and submersibles, and even on satellites in outer space.

A "tool box" of individual designs

Designing and building a tailor-made cable requires the "art" of translating the full range of existing design and material options into a superior tailor-made cable. Along with their accumulated knowledge of designing more than 6,000 individual types of customer-specific cables, our engineers have access to an extensive "tool box". It provides them with a wide range of materials for the jacketing, design options for the internal architecture and the sub-assembly of conductors, special shielding designs, and many other creative concepts.

For example, special strain-relief elements can be integrated into the jacket for greater stability of a cable. Or, low friction, sliding wrapping tapes can be used to effectively prevent "snagging" of the various components of a cable, a feature crucial in cables required to withstand mechanical stress, i.e. fast take-up and pay-off reeling operations.

EMI-shielding a major concern

A strong demand for tailor-made exists in cables designed for optimized protection against EMI (electromagnetic interference). At elocab, approximately every fourth customer is looking for special protection against strong magnetic fields and high-frequency interference.

Electromagnetic fields creating interference of sensitive signals appear particularly when power, sensor and control wires are run adjacent to each other. This applies to tight cable tracks and multi-cable bundles usually found in modern automation and machinery equipment. Typical sources of interference are controllers and electronic components. EMI also plays an important part in hybrid cables, where different components are combined in a single cable for cost and space savings.

In order to optimize their cables for protection against electromagnetic interference, design engineers appraise a full range of alternatives before selecting the best solution. The applied shielding designs range from the use of foils to served wire or braided shields. Extremely difficult problems are solved by shielding designs which may combine the same or different shielding in multiple layers.

The choice of material, the shielding conductor diameter, the angle of pitch and the number of strands are all factors which determine the density and the specific frequency resistance of a shield. High-permeable alloys, such as MU-metal, used as a wrapped foil shield, can absorb low-frequency magnetic fields.

Classic EMI "problem sectors", such as machine building, measurement and control systems, as well as the communications and high-frequency technologies, are among the prime users of perfectly-shielded, tailor-made cables. A strong demand for shielded cables is also found in the medical industry, where cables in X-ray machines and other diagnostic equipment carrying extremely sensitive video information require reliable protection against any interference.

Hospital patients may book tests on the latest diagnostic equipment weeks or even months in advance. A cable failure that debilitates equipment represents lost billable time for the institution and enormous inconvenience for staff and patients.

Cables on a diet

Putting cables on a diet (reducing their diameter) is one of the most common challenges to design engineers involved in building tailor-made solutions. Space is extremely limited in many machines and automation tools, where cables often must perform in tight cable tracks or in a confined working environment.

The compact design of small-diameter, high-flex cables with improved electrical properties offers easy installation as well as weight- and space-saving options. Ultimately, slimming down a cable translates into a more flexible and longer-lasting product. Design engineers are able to substantially reduce the diameter of tailor-made automation cables - by 30 to 40 percent - compared to standard products.

A significant portion of tailor-made automation cables are specifically designed for applications in cable tracks and on robots where they are required to flex millions of times at high speeds. The key to designing a superior product for these flex applications is to slim down the cable, which either allows for a tighter bending radius or increases the bend radius-to-cable diameter ratio.

At elocab, we build high-flex, diameter-reduced cables which can withstand a bending radius as small as five times the outside diameter, designed for a life-span of up to 20 million bending cycles or 20,000 operating hours.

The longer life-span is primarily attributed to unique cable designs. High-flex cables can, for instance, incorporate high conductor stranding. In tailor-made cables, particularly with a bigger diameter, the conductors are cabled in bundles of several components to prevent breakage.

Engineered for optimum performance in cable track applications, tailor-made high-flex cables deliver rugged, durable performance in robotic processes, high-speed assembly lines, automation equipment, machine tool and material handling systems. Cables used in cable tracks typically flex back and forth on one axis. Tailor-made cables are capable of performing high-speed flexing at speeds of up to 10 meters per second.

In addition, longevity is provided by special jacket materials that make the cables resistant to abrasion and other environmental challenges. The recently launched, UL-approved, flame-retardant, halogen-free polyurethane (PUR) material featured on elocab cables can withstand temperatures from -50C to +90C and has high tensile and shear strengths. From an environmental perspective, halogen-free PUR cables can be recycled, landfilled or incinerated without releasing dioxins or other toxic emissions.

Tailor-made cables not only offer high performance and reliability that looks good on the balance sheet, but is also noninvasive to the environment.

Where a perfect fit is a must, custom-made is the wiser option.