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What do you need to know about industrial robot cables?

2023-05-01 11:08:49

What do you need to know about industrial robot cables?

With the intelligent requirements of industrial production, the industrial robot development from the unit and to multi-function, as a carrier to transmit signal and power, industrial robot cables need to meet higher performance with higher bending resistance, torsion resistance, resistance to mobility. 

Robot cables refer to the robot main body, power supply, signal, control, and robot peripheral cables. Generally, they can be classified as: 1. Robot power cables, which are generally fixed installation.2. controller to tech pendant cable, usually flexible cable with tensile strength demand 3. control host computer to main body cable, including power I/O, signal cables, etc., fixed or move installation, drag chain cable applied on movement with bending performance. 4. Robot main body cables, including power cables, I/O cables, signal cables, etc., require high bending performance, besides electrical performance and weather resistance, robot cables also need withstand long time bending movements, large angle twisting movements and high-speed reciprocating movements.

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At present, the current domestic and international standards for robot cables testing are below 

1. CRIA 0003.1-2016 "special cables for industrial robots " released by the China Robotics Industry Alliance in 2016, which has become a national standard. 

2. TUV 2 PfG 2577 "Requirements for Cable Used in Robot System" issued by TUV Rheinland company in August 2016, specifying eight mechanical durability test items for robot cables, which is popular standard for most robot cable companies.

3. Germany VDE company published in July 2018 VDE-PB-0022 "Test Specification Classification of Flexible Industrial Cables", the standard is classified into five major parts: mechanical test, chemical resistance test, temperature resistance test, EMC electromagnetic compatibility test, flammability test, etc.

4. UL RP 5770 "Rcom" issued by UL in August 2018 "Recommended Practice for Evaluating Cables for Use in Repeated Flexing Applications", which is specifies four mechanical performance test based on the UL 758 standard.

The above standards use mechanical life tests such as drag chain test, torsion test, bending test and flexing test as an important basis for verifying the mechanical and physical performance of robot cables. The standard has different requirements for the test parameters and test results. After 5 million to 20 million times drag chain, 1 million to 10 million times torsion, 5 million to 10 million times bending, and 300,000 to 1 million times by flexing, there are no visible cracks on the surface of the sample sheath and insulation cores, The conductor DC resistance changes within 10%-25%, and the mechanical and material performance of the cable is registered and classified according to the test conditions and results.

If need more mechanical and physical performance evaluation of the cable, EN 50289-3--2001, GB/T 5013.2--2008, GB/T 5023.2--2008, GB/T 7424.2--2008 and other standards can be used to conduct abrasion tests, impact tests, compression tests, tensile performance tests, cable rigidity tests and twisting tests.


The design of industrial robot cable:

1.  Conductor structure. It is recommended to use 6 types of ultra-soft grade conductors with flexibility. Generally, the thinner the conductor, the better the flexibility of the cable. Through long-term tests, the manufacturers optimize the diameter of single conductor to make it have the most suitable tensile strength and flexibility.

2. Wire insluation. Common robot cable insulation materials include polyvinyl chloride PVC, thermoplastic elastomer TPE, thermoplastic polyester elastomer TPE-E, ethylene tetrafluoroethylene ETFE, and polyurethane PUR, and the insulation/jacket combination is polyolefin POE/PUR, TPE/PUR, or TPE/TPE, which can reach 10 million drag chain movements and 1-3 million twists without failure. If higher movement performance is required, the insulation material can be selected as ETFE or TPE-E, and the jacket material can be selected as low-friction PVC, which can greatly increase the movement performance and bending radius.

3. Tensile Component. The midsection of the cable, and the space in the crossover area of each core wire, tensile components such as polyester fibers, aramid ropes, and steel wire reinforcements should be filled in to effectively protect the stranded structure and prevent the stranded from benefiting the central area of the cable.

4.Inner sleeve. For shielded cables, an inner sleeve can be selected before the shield to reduce abrasion between the insulation and the shield and protect the insulated wire from being damaged. An extrusion-molded inner sleeve should be used to package the stranded wire structure so that it will not be scattered.

5. Shielded braided layer.  The optimized shielding tightly weaves the shielding layer outside the inner sleeve, and the shielding layer needs to have excellent anti-twisting ability to avoid electromagnetic compatibility (EMC) failure caused by printing fracture.

6. Outer jacket. Outer Jacket Outer jackets usually have several materials such as PVC, TPE, and PUR. Among them, PUR has higher flexibility, wear resistance and good flexibility at low temperature. It can better meet the requirements of abrasion resistance, bending and flexibility of robot cables, and can meet different functions through material properties, such as UV resistance, low-temperature resistance, oil resistance, and cost optimization. High abrasion resistance is a necessary characteristic for all cables.

Industrial robotic cable.jpg

How to select the proper industrial robot cable

Cables, as an important component of robots, directly affect the life of robots. All robot cables have a service life, and they need to be replaced on average every half year, which is a significant expense for the user. Therefore, the robot manufacturer should analyze the performance and requirements of the cable, and clarify the customer's requirements when designing the cable to provide cost-effective products to improve the customer's utilization rate and reduce robot maintenance costs. The following aspects should be considered: 

1. Specify the state of use. Whether the cable is subjected to one-way or two-way twisting for a long time, whether it is subjected to joint actions of bending twisting and stretching, requirements for abrasion resistance, tear resistance, flexibility, etc. The structure and finished outer diameter of the cable need to be designed according to the bending radius and twist radius, and pay attention to the influence of production process on the bending radius of the cable.

2.Specify the cable function. Whether it is a power cable, control signal cable, monitoring feedback signal cable, data transmission cable, composite cable, etc. Flexible cables for robots include 0.6 / 1KV and below power cables, 450 / 750V and below control cables, servo cables, and 30V signal cables

3.Specify the applied equipment. Industrial robots are divided into arc welding robots, spot welding robots, assembly robots, painting robots, handling robots, etc. Special robots have special requirements, such as arc welding robots requiring cables to be resistant to high temperature and sparks.

4.Specify the requirements for operating rate, operating length, allowed voltage, data transmission performance, etc. 

5. Specify the use environment, such as temperature and humidity, and other special features that the cable should have, such as flame resistance, acid and alkali resistance, weather resistance, high and low-temperature resistance, environmental requirements, anti-interference requirements, etc. 

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