Inside the Test Lab: The Development, Design and Testing of chainflex® Continuous-flex CablesOctober 10, 2017
For more than 25 years, igus® has been creating specially designed chainflex® cables, which stand up to millions upon millions of dynamic twisting or flexing cycles. To ensure performance, igus has a 29,600 square-foot lab where, at any given moment, there are over 700 tests running in parallel. Testing is performed in true-to-life application settings to ensure reliable performance in even the harshest environments. In the following guide, product managers and cable experts reveal their tried-and-true development methods that have resulted in cables that outlast and outperform conventional cables, as well as reveal the features of chainflex® design that provide the confidence to guarantee their performance for up to ten million dynamic cycles.
What Makes chainflex Different?
A great number of flexible cables are constructed in a layered design, at a lower cost to manufacture. However, such flexible cables are often constructed without attention to detail, including details such as the length of the pitch, the center-fill material, or the type and method of jacketing. While these cables may provide sufficient performance in the short-term or in certain short travel applications, in long travel, gliding or demanding flex applications, things can quickly change. The cables tend to fatigue, insulation and jacket materials lose their tensile and elongation properties, the cable core becomes compromised and the torsional forces of the conductors release and untwist in parts of the cable: the dreaded 'corkscrew effect' has taken hold.
To eliminate cable corkscrewing, as well as many of the other common modes of cable failure, chainflex continuous-flex cables are designed around seven major guidelines and are most often manufactured using a bundled design. Wires are twisted with a special pitch length, and the resulting conductors are cabled into bundles. For cables with large cross sections, this bundling technique is done around a strain-relieving center element.
The multiple bundling of the conductors changes the inner and outer radii of the bent cable several times at identical intervals. Pulling and compressing forces balance one another around the highly tensile center element, which provides the necessary inner stability. This keeps the cable core stable at all times, even while under maximum bending stress.
Extensive Testing Leads to Guarantee
Why is testing so important to igus? Flexible energy supply systems need to function properly. In the 1980s, an increase in the demands of automation technology led to an increased amount of cable failure across industries. One particular kind of failure caused by corkscrews – permanent deformation of flexing cables in automated applications caused by excessive stress – even led entire production lines to shut down, resulting in lost production and high-cost emergency repairs.
Since the introduction of chainflex cables, igus has conducted hundreds of thousands of tests to ensure that incidents like this do not occur. At any given moment, more than 700 tests are being conducted in a 29,600 square-foot lab for flexible cables, located at igus headquarters in Germany.
igus has been involved with numerous committees that are responsible for publishing standards and regulations, such as VDE, DNV-GL and UL, in order to create tests and production standards for chainflex cables that address requirements their customers need. This is what makes the igus tests so different from other cable manufacturers.
The lab is filled with over 50 different test rigs and machines, features a wide variety of travel distances –ranging from 1 foot to 394 feet – and can implement horizontal and suspended applications if needed. Included in the lab are torsion test rigs with 12 triflex® multi-axis cable carriers that provide a plethora of testing options and expand the torsion test product range, rounded out by four six-axis robots. In addition, the lab is equipped with special-purpose testing stations for wear and media testing, which require more realistic testing conditions than the exposure and aging tests based on UL or VDE standards.
In order to conduct its frost tests, which determine the thermal influences on moving cables, members test in a special cooling container with a 23-foot-long axis. Once tests are completed, all of the cables are taken apart and testing events are documented in detail. All of these tests are conducted with the sole purpose of providing the user with planning reliability for their cable selection.
What Kind of Tests Are Being Conducted?
Engineers at igus conduct a variety of tests, such as those for linear movements in short and long travels, torsional movements and application reliability, in addition to performing elaborate analysis and documentation.
• Quality assurance, which involves continuous batch testing in order to ensure cable quality
• Materials testing, which is needed for new materials being developed for conductors, insulation, jacket materials, etc.
• Rotation tests for tight bend radii
• Frost tests in which cables and cable carriers operate in temperatures of negative 40 degrees
• Media tests for durability against chemicals
• Tests for combined movements, which include a simulation of complex movements in robotic applications
• Special design tests for customers with specific motion sequences, which require testing before mass production can begin
igus even conducts service life endurance tests that can take up to four years to determine the maximum lifespan of selected cables. During these tests, the lab consistently monitors the parameters in order to recognize failure as it occurs in real time.
During the procurement process, customers want to know how long their cables will last. Thanks to the extensive testing methods at igus, it can now offer clear statements, allowing cable users to plan more effectively with regard to service life. igus was the first manufacturer to guarantee its cables’ safety and durability. Here’s how the chainflex Guarantee Program works: All standard chainflex cables receive a 3 year, 10 million-cycle guarantee when installed according to igus chainflex standards. It’s that simple!
Learn more at www.igus.com/chainflex.
Up Close and Personal: Cable Expert Q&A
Don Nester, Product Manager; Tim Marran, Product Specialist (igus Inc., USA); and Rainer Rössel, Unit Manager (igus GmbH), all for chainflex cables, give customers an inside look at the continuous-flex cable development process. Even with more than 25 years of cable design and production experience, igus still aims to improve. That is why its 29,600 square foot test lab is so important – to detect cable breakdowns before they even happen while operating in the field.
Can you tell us about continuous-flex cable's development process? How and where are the cables created?
All chainflex cables are created at igus headquarters in Cologne, Germany, igus is always driving our development team with new targets, such as what kinds of new material and design combinations can help increase the lifetime and reduce the production cost.
When we discuss the cable design, we define all the details of the structure, starting from the copper stranding; discuss all the materials in detail, down to the manufacturer of the plastic materials; and determine what types of machines would be able to produce the best cables.
After we create a new prototype, the most important part of the development process begins – the testing program! Even today, though we have more than 25 years of cable design and production experience, we still have to test our new designs and materials in our test lab before presenting the cable to the market. Some of the new products being released in 2016 were designed four years ago. Yes, that’s right – our testing can take four years before we are happy with the result and begin selling!
igus has one of the largest labs in the industry where cables are tested in real-life settings.
Can you explain some of the different equipment and machinery within the lab?
I believe that igus is operating the largest test lab for moving cables in the world. We began the development of our testing processes and procedures more than 25 years ago – of course, the lab was much smaller at that time. Today, we are operating our 29,600 square foot lab with more than 60 testing machines, which are completing approximately 2 billion test cycles and more than 1.5 million electrical measurements each year.
These test results and testing parameters go straight into our database, and from all these years of collected data, we have created our online lifetime calculator, and we are also able to offer a three-year guarantee on all our cables.
One of the main benefits of testing in the igus lab is that since we have the design of both the cables and cable carriers in our hands, we are able to test them together and optimize the design of both products. How important is the testing lab in the development of continuous-flex cables?
The test lab is the main development tool. We are still learning new things day by day, even after more than two decades. Of course, we are also constantly engaged in batch testing, meaning that we are taking our cables from our production line, following a statistical rule and testing them in the lab. This allows us to maintain the same level of production quality of our cables, and ensure it is always up to our standards. This offers protection for our customers, so they can be sure that our cables will always offer the same levels of performance.
During the testing phase, what happens when a cable does not meet the chainflex standard? How do you overcome issues and challenges that arise?
Having the occasional failing test is better than only having positive results, because we know our tests are effective. If you only see good results from every test you run, chances are your testing procedures are not as good as they should be. Instead, if we see test results that are not the best, we can analyze the possible reasons for the poor results, check to see what we can change and go all the way back to the prototyping stage if necessary and start again.
Who benefits from using chainflex cables?
The customer! Because of our testing know-how and ability to produce reliable cables, we are able to offer our customers not just one or two cable designs or families; for example, in the area of control cables, we can offer 13 different cable designs with a range of lifetimes, price targets and for particular industries or applications. For example, a four conductor 18 AWG control cable is in stock with six different performance levels and with shielded and unshielded versions.
The main benefit of chainflex cables is the ability of the customer to select a cable that best fits his or her application, at the lowest possible price. That’s our main objective in our development and testing process.
What separates chainflex cables from other continuous-flex cables on the market?
The big differences between igus/chainflex and other manufacturers are how much we know about the predicted lifetime of our cables and, of course, the huge range of different mechanical alternatives available for the same type of cable. For example, chainflex offers not just one or two Ethernet cable options, but more than 30! We offer this many options to provide the perfect cable for applications with long travel, cold temperatures, long free-hanging distances, robotic cables, etc. This is completely unique to chainflex; there is nobody else in the market who can match our cable offerings, and ours is available from stock, without order MOQ or cutting fees!
igus developed chainflex continuous-flex cables to deliver longer life and better performance for demanding applications that were springing up as a result of the new automation technology at the time. igus® now offers well over 1,000 chainflex cable varieties for all types of applications.
chainflex continuous-flex control cables are intended for use in energy chain® cable carriers. They are capable of torsional movement – depending on the cable – and can be used at high speeds and accelerations.
chainflex control cables are UV resistant, flame retardant, halogen free and can withstand very high or low temperatures. They are available shielded or unshielded, with a choice of PVC, PUR and TPE outer jackets. In addition, they have a bending radius as small as 4xD and are available at a range of price points to meet specific application requirements.
chainflex continuous-flex data cables have bend radii starting at 7.5xD. These data cables are available with PVC, PUR and TPE outer jackets and come layered, in twisted pairs, or in shielded twisted pairs. They also conform to key standards and are suitable for high mechanical load requirements at high speeds and accelerations. They are flame retardant, oil resistant and shielded. chainflex data cables are intended for travels up to 400 meters and are tested to stand up to dynamic flexing applications.
chainflex continuous flex bus cables conform to various key standards, can be used for high speeds and accelerations, and come with PVC, PUR or TPE outer jackets.
chainflex bus cables are available to meet a wide range of industry standards for bus and Ethernet network cables, including Profibus cable, Interbus cable, CAN-bus cable, Device-Net cable, CC-link cable, Ethernet cable, CAT5, CAT5e, CAT6, CAT6a, CAT7 Ethernet, GigE Profinet, FireWire, USB cable and DVI cables.
Measuring System Cables
chainflex measuring system cables are suitable for dynamics with medium to high mechanical load requirements and are available with PVC, PUR or TPE outer jackets. The measuring system cables are designed for more 18 specific motor types; conform to various key standards; and are flame retardant, coolant and oil resistant, depending on the outer jacket type. chainflex continuous flex measuring system cables can be used in applications with high speeds and accelerations, and comply with the specifications of drive systems manufacturers.
chainflex 50- and 75-ohm continuous flex coaxial cables are intended for use with maximum mechanical load requirements, are UV and bio-oil resistant, and are available as one- or five-core cables.
Fiber Optic Cables
chainflex continuous flex fiber optic cables are coolant and oil resistant, are made with plastic and glass fibers and have a bending radius up to 5xD.
PUR and TPE outer jackets are available. chainflex offers fiber-optic cables that are able to suit even long travel applications while maintaining transfer speeds, and are also available in single or milti-mode options.
chainflex servo cables are abrasion-optimized and have bend radii starting at 7.5xD. Both PVC and PUR servo cables are available with an inner fleece wrap or an inner jacket for high dynamics. chainflex servo cables are flame retardant and oil resistant and can be used for high speeds and accelerations. igus also offers a variety of space-saving, cost-effective hybrid servo cables.
chainflex continuous-flex motor cables are suitable for maximum mechanical load requirements and extreme applications. They are available shielded or unshielded and are available with PVC and TPE material outer jacket types. Single or multi-core options are available.
chainflex robot cables are designed to withstand torsional stress of ±180 degrees for every three feet of cable. These cables have been tested in applications that reproduce the forces and impacts that cables are typically exposed to in real-life industrial robotic applications. These tests have proven chainflex robotic cables to last up to 10 million torsional cycles.
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