Article written by igus.
In recent years, cable management has come into the limelight because even though robots have become more complex, machine reliability has increased dramatically. Unfortunately, the methods used to attach and guide cables and hoses on robots have not followed suit. While managing cables and hoses is often an afterthought in many designs, it is truly a vital part of any well-functioning robot.
Since the 1960s, cable management methods for robots have not changed dramatically. Most experts agree that one of the top mistakes is underestimating the knock-on effect of cable management issues. During a conference hosted by the Robotic Industries Association (RIA), a group of leading system integrators cited cable issues as the number one reason for downtime in robotics cells. Headaches range from tangled and corkscrewed cables, to complete breaks that cause downtime, lost revenue and damaged reputations.
The “Less is More” Approach
Current systems try to keep the cables on a six-axis robot static while everything operating around them is dynamic. Using one, long restrictive cable package prevents movement in sync with the robot. Restrictions stress cables, which accelerates failure. Often technicians bind cables with corrugated hose, cable ties or even duct tape. The goal is to minimise tangling and interference with the machine, but these types of solutions cause corkscrewing and failure.
The “less is more” approach to cable management is a best practice that robotics engineers and integrators can apply. It centres on designing cable management systems in three separate sections: the sixth to third axis; the third to second axis; and the second to first axis. This separation is the key to longer-lasting cables. Each cable section needs a minimal dresspack, strain relief with service loops, and a junction box that contains and protects the electrical connectors joining the cables.
Using strain relief systems can eliminate stresses and extend the service life of a moving cable. This strain relief may consist of standard elements such as tie wrap plates or clamps. An important measure is to ensure the cables are in the neutral axis, not touching the inner or outer radius of the cable management system.
Separating the dresspack into three shorter sections prevents it from wrapping, catching or snagging on machines and minimises stress on cables and hoses. This approach applies to any six-axis robot, regardless of manufacturer or application. While other fixes such as duct tape and ties wraps might cost less and work temporarily, in the long run, properly designed dresspacks reduce unnecessary downtime and maintenance costs.
In addition to the appropriate dresspack, it is imperative that six-axis robots use dynamic cables specifically designed for continuous flexing, and twisting, such as those found in the igus chainflex “robot” range. The most important feature to take into account is the cable’s shielding torsion-resistance. Shielded cables face a greater risk of failure because constant movements can easily make the shielding break down. Use unshielded, high-flex cables whenever possible to avoid problems. If this is not an option, turn to special “torsionable” cables.
To guide and protect
There are different options available for guiding and protecting cables on six-axis robots. The three most common are flexible tubing, enclosed dresspacks and robotic cable carrier systems.
Corrugated or flexible-tubing is available in a wide range of sizes and styles. It has superior tear resistance at connection points and a long service life, even with reverse-bend cycles. However, corrugated tubing has its limitations. It has minimal torsion resistance, and can only be fixed at two points with a defined length. The tubing can also stretch as the robot moves, which puts undue stress on the cables. Additionally, tooling interference can occur because there is no control path for movement.
An enclosed dresspack, on the other hand, mounts directly to the robot and is available in multiple configurations. It uses corrugated tubing installed inside a plastic-reinforced housing to protect the cables. The system’s spring-loaded design minimises catch and pinch points. Unfortunately, due to the enclosed design, cable maintenance is difficult, and because it is not modular, the entire unit must be replaced if one component breaks. Problems can also arise if the programming or movements of the robot change. This is because an enclosed dresspack does not prevent the cables from exceeding their maximum bend radius.
At the heart of the “less is more” approach is the robotic cable carrier system. It mounts directly to the robot and is available in multiple configurations. Like an enclosed dresspack, it has a spring-loaded design, which minimises catch and pinch points. However, robotic cable carriers offer additional benefits not available with the other systems. They can come equipped with strain relief options to extend the service life of the cables; cables can also be quickly added or removed without dismantling the system. The defined bend radius of a robotic cable carrier protects cables from exceeding their maximum bend radius.
Dresspacks made easy
The new online dresspack configurator from igus enables engineers to quickly find the right robotic cable carrier system based around the triflex R energy chain. Easy to install and fill, this multi-axis energy chain protects moving cables and hoses on robots and thus increases service life in operation.
Since its inception, the range of igus triflex R parts for robots has grown significantly. There are now 8 sizes, 5 methods of opening, 4 retraction module types and literally hundreds of other accessories, including mounting brackets, robot specific adaptor plates and protectors. This means that when dressing a robot, there are many options that could be quite overwhelming. With the new configurator, this is a thing of the past.
The dresspack configurator automatically accounts for which parts are compatible and only offers those that will work with any given robot. The engineer now simply selects the robot manufacturer, the type and model of robot and the number of axes to equip. The configurator then displays a 3D representation of the robot with the components of the energy supply system being added at each stage to ensure clarity of what is being provided.
The first step after robot choice is to select a retraction system, which is designed to keep the energy chain under tensile stress to avoid looping and protect against damage. The user then configures the triflex R e-chain type and the size. Extra accessories such as protectors, brackets or even extra triflex R chain links can also be added.
Once the configuration is complete, the tool creates a list of all the components of the energy supply system automatically, which can be added to the shopping cart for ordering. A total system price is displayed immediately too. CAD models of the components and a PDF report of the configuration are also provided.
To use the igus dresspack configurator, please visit: www.igus.co.uk/dresspack For additional information, please call igus directly on: 01604 677240.
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Based in Northampton in the UK and with global headquarters in Cologne, Germany, igus is a leading international manufacturer of energy chain systems and polymer plain bearings. The family-run company is represented in 35 countries and employs 3.800 people around the world. In 2017, igus generated a turnover of 690 million euros with motion plastics, plastic components for moving applications.
With plastic bearing experience since 1964, cable carrier experience since 1971 and continuous-flex cable since 1989, igus provides the right solution based on 100,000 products available from stock with between 1,500 and 2,500 new product introductions each year. igus operates the largest test laboratories and factories in its sector to offer customers quick turnaround times on innovative products and solutions tailored to their needs.
The terms igus, chainflex, CFRIP, conprotect, CTD, drylin, dry-tech, dryspin, easy chain, e-chain, e-chain systems, e-ketten, e-kettensysteme, e-skin, flizz, ibow, iglide, iglidur, igubal, manus, motion plastics, pikchain, readychain, readycable, speedigus, triflex, plastics for longer life, robolink and xiros are protected by trademark laws in the Federal Republic of Germany and internationally, where applicable.
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For further information, please contact:
Megan Campbell, igus
Tel: 01604 677240
Sumbul Baig, Publitek
Tel: 01582 390980
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