In a state of flex: specifying the correct continuous flex cable ...

Tag : Compound Tape
Conductor design

The demands placed on flexible control cables increase dramaticallywith the speed and sophistication of robots and automatedequipment. Continuous flexing, bending, and exposure to destructivesolvents and oils can take their toll on flexible control cables.

Cable materials must be resilient so that once the cable completesa flexing cycle, they will immediately return to their originalunstressed condition. The copper conductors must be made of finelydrawn strands rather than coarse strands. In addition, the cablemust be designed so that the individual conductors inside thejacket have freedom to move, preventing harmful stress on theconductors.

Control and power cables operating in high-speed automatedequipment, like gantry robots, pick-and-place machines, conveyorsystems, assembly systems, and machine tools, are subject tocontinuous flexing and twisting. While it is possible to usestandard control cables in these applications, they will notdeliver the long-term performance of cables designed exclusivelyfor this purpose.



Jacketing choices

The number of chemical solvents and oils used throughout theindustry is enormous and growing steadily. Each one is potentiallyharmful to a control cable. Some of these chemicals are potentenough to completely destroy cables. The hostile agent is drawninto the jacketing material, causing it to balloon, soften, andultimately disintegrate. Alternatively, it may leach a similarchemical from the jacketing material causing it to become brittle.Choosing the appropriate jacket material requires knowledge of itsexpected operating environment.

Stand PVC is the most used jacketing material. However, it is onlysuitable in environments with minimal amounts of industrial oils.Special types of PVC have been developed that are resistant to mostoils, and can be used freely where these oils are present.Polyurethane jackets have a similar resistance to oils and solventsas special types of PVC, while providing increased abrasionresistance.



What are the options?

There are seven categories of continuous flex cables:

1. Moderate flex cables are designed for use in cable tracks,automated handling equipment and machine components in constantoperation. They are often available with a flexible tinned copper braidshield to provide isolation from electrical interference. Specialfeatures include a moderate resistance to oils and a minimum bendradius equal to 10 times the cable diameter.

2. High-speed continuous flex cables are designed for continuousflex applications in high-speed automated equipment. They are also available with a flexible tinned copper braid shieldto provide isolation from electrical interference. Typicalapplications are found in industrial robotics, machine tools,automated doors and material handling centres. Special featuresinclude: resistance to oils, solvents, water-based coolants, andabrasion; a minimum bend radius of 8 times the cable diameter;non-wicking tape and specially formulated compounds enhancing thecables' flexibility; super fine copper stranding; and UL and CSArecognition.

3. Ultra flexible continuous flex cables are designed for smallbend radius application and can be used without restriction in themost modern automated manufacturing systems. The insulation and flame-retardant jacketing materials aremechanically and chemically resistant to harsh environments. Theyare available with a flexible tinned copper braid to provideisolation from electrical interference and are designed for use,both indoors and outdoors, in wet, dry, and extremely coldconditions. Typical applications are found in machine tools, gantryrobots, pick-and-place units, automated handling equipment,conveyor systems and packaging equipment. Special features include:resistance to oils, abrasion, and cold temperatures; a minimum bendradius of five times the cable diameter; non-wicking tape andspecially formulated compound enhancing flexibility; extra finecopper stranding; and CE conformance recommendation.

4. High-speed continuous flex data transmission cables are designedfor automated production processes requiring increased flex lifecharacteristics and durability. Special assembly techniques and small cable diameters allowinstallation in confined operating areas. The cables are availablewith a flexible tinned copper braid shield to provide isolationfrom electrical interference. The cables are also available withspecial paired assembly to ensure maximum interference suppressionin analogue or digital signal transmissions. Typical applicationsare found in gantry robots, pick-and-place units, automatedhandling equipment, conveyor systems and packaging equipment.Special features include: resistance to oils and abrasion; aminimum bend radius of eight to 15 times the cable diameter;non-wicking tape and specially formulated compounds enhancingflexibility; and extra fine copper stranding.

5. Continuous twisting robotic cables are designed for use inapplications where combined twisting and bending stresses occur. Special smooth-core insulation and slide wrapping ensureconsistent performance even when subjected to long term torsionalstress. This unique cable accurately transmits control signals andpower supply in automated applications requiring twisting movement.The maximum torsional angle these cables can accommodate is plus orminus 360° per metre. The cables are available with a flexibletinned copper braid shield to provide isolation from electricalinterference. Typical applications are found in bottling andpackaging equipment, welding robots, grinding and cutting machines,pick-and-place robots, rotary tables, and portable hand tools.Special features include: oil, chemical, and abrasion resistance; aminimum bending radius of 15 times the cable diameter; non-wickingtape and specially formulated compounds enhancing flexibility; finecopper stranding; and CE conformance recommendation.

6. Continuous flex servo cables are designed for automated servosystems. They provide power and signal to a servo motor while withstandingcontinuous flex cycles. A unique combination of signalling andpower cables in one jacket, they provide functional safety,reliability and durability, while reducing weight and saving space.They can be used in all electrical equipment in dry, damp, and wetconditions. Shielding is required to prevent distortion of theprecise control and feedback signals created by electromagneticinterference (EMI). Typical applications are found in cable tracks,assembly lines, CNC machines, industrial robots and pick-and-placemachines. Special features include: oil, chemical, and abrasionresistance; a minimum bending radius of 12 times the cablediameter; specially formulated compounds enhancing flexibility; andextra fine copper stranding.

7. The single conductor, double-insulated design utilises Class Kstranding, thereby providing an extremely tight bend radius andsuperior flexibility resulting in easier handling and installationin a confined operating area. These cables can be used for internal or external applicationswithout conduit. Typical applications are found in spindle motors,welding robots, cable handling systems and cable tracks requiringflexible power cable and interconnect wire from the power supply tothe machine. Special features include: resistance to abrasion,mineral and synthetic oils, and water-based coolants; a minimumbending radius of five times the cable diameter; and Class Kstranding.



Conclusion

Cable life can be increased dramatically by specifying the propercable and the proper jacketing material for each application,installing it correctly, and understanding its requirements. Thisknowledge will result in lower operating costs, higher reliability,and longer functional cable life. A full electronic cablespecification tool can be found on www.lappcable.co.za/cablefinder.html

For more information contact Grant Joyce, Lapp Cable, +27 (0)11 2013213, grant@lappcable.co.za , www.lappcable.co.za