You've got to be flexible

These days, industrial robot and production systems designers demand much more from cabling technology. Managing Editor Steve Kuehn takes a look at how far cabling quality and reliability have come.

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 By Steve Kuehn, Managing Editor

 

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o matter where their machines land in the global manufacturing landscape, industrial robot and production system designers all stand on common design and specification ground when it comes to cabling. To many, cabling may seem pretty mundane. But it’s a big deal when machine reliability and production throughput are all inexorably “connected” to the cabling that transfers network data, control and sensor signals and power to points across a production machine or robotic system.

System designers agree that poorly specified/low-quality cabling can be a chronic cause of machine failure and line downtime. You’ll also learn from them that cabling quality and reliability have come a long way. Ten to fifteen years ago, cable problems caused as much as 30–40% of downtime events in high-flex operations. Today, cables that would likely last about two years of duty are now lasting nearly the life of the machine. This article takes a look at how far the technology come.

It’s a Hard-Knock Life
It starts with system cabling’s ability to function in myriad environmental conditions from hot to cold, wet to dry, while being immune to flying sparks, potent chemicals, washdowns and other harsh conditions.

            FIGURE 1: THE TOUGH GET GOING
           
           

Robotic systems are being tasked to do increasingly more complex tasks in challenging industrial environments. That means the demands on the cabling that delivers power, data signals and networks are greater than ever. With advances in materials and design, cables are now tough enough to handle it.
 

Then one has to consider a cable’s ability to handle the dynamic torsional and linear stresses at work as they twist, bend, stretch and flex through millions of cycles. Automotive manufacturers in particular have embraced robotic production systems to automate manufacturing and assembly procedures. Suppliers such as ABB and Fanuc Robotics have developed machines that employ a complex range of motions to accomplish critical tasks in the production setting (Figure 1). For these kinds of systems, design engineers have much to consider when specifying cabling for their designs.

Experience counts and Bob Frease, staff engineer for Fanuc Robotics has several decades of it, providing vehicle and other manufacturers with reliable robotic production systems. “We first determine what the machine has to do. From that point we look backward and start taking into account a number of factors,” he says.

Frease points out that in robotic applications, cables engage applications from power cables to motors and drives, to communications with separate encoder and feedback links. “Some cables have to be intrinsically safe (IS), then there’s grounding, as well as high-voltage power service to other processes such as end efectors on welders to consider.”

Frease says Fanuc engineers analyze the environment and the machine’s intended duty carefully as well. “Then we look at national standards such as NEC and other relevant application and safety standards,” he adds. “What it boils down to is the cables have to be able to defend against the environment and stand up to the types of motion they will encounter as it functions.”

He also identifies the usual plant environmental issues, i.e., those that can affect the jacketing on the cables he specifies. “Robots, especially in automotive applications are doing much more,” he says. “They’re operating in places where oils, paint solvents, inks and flash can attack jackets , while other units must operate in ‘exotic’ environments with high levels of UV and other radiation, extreme cold and even vacuum.”

Clean to the Extreme
Another production dynamic is the environmental condition required to manufacture in extremely clean environments. While cabling in clean or sanitary environments (chip fabrication, food processing, electronics) isn’t likely to be subjected to severe conditions such as sparks or chemicals that can damage or degrade materials, it can’t shed particulate that can contaminate the working area.

To provide a solution to one of its customers, a Korean distributor sought a certified clean room cable that also was suitable for a high-flex cable track application. According to cable supplier Kabel Wächter Gmbh, there was no such product on the market—until the company’s engineering department designed special cabling to fill this need. “We use a polyurethane that is highly resistant to abrasion and features a sharply minimized fraying rate (the loosening of particles as a result of pressure and abrasion),” says Michael Andris, product manager for Kabel Wächter. “The production takes place under very clean conditions and there are no airborne particles such as talc, releasing agents or lacquer wetting inhibitors to be found in this cable.”

According to Andris the cable is especially valuable to users looking for properties such as resistance to oil grease, coolants and other lubricants,. It’s halogen-free, flame-retardant and can be employed in demanding motion applications.

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