Before 2010, there were very few Ethernet cables wired in drag chains. In recent years, the application of Ethernet cables has become increasingly widespread, replacing many traditional and complex wiring, and more and more Ethernet cables need to be wired in drag chains. However, many engineers still do not pay special attention to the ethernet cable that needs to be laid in the drag chain and moved back and forth. They directly use ordinary ethernet cables, which may not show any problems in the short term of 1-2 months. If the drag chain moves frequently, it usually does not exceed 3 months, and ordinary ethernet cables may experience occasional packet loss, equipment random shutdown and other problems.

I have been working on automation wiring harness matching for over 10 years, and have followed up on multiple projects in various industries such as automotive welding production lines, painting production lines, beverage automation packaging lines, lithium battery production lines, etc. I have encountered many similar problems.

A real fault case where the wrong cavo ethernet flessibile was selected, resulting in losses to the production line.

A 6-axis painting robot from an auto parts factory in Guangzhou, equipped with an industrial camera and EtherCAT bus on the drag chain, has a round-trip travel of 3.2 meters and 22 times per minute. At first, the company’s purchaser did not distinguish the ethernet cables that needed to be laid on the drag chain, and directly laid the commonly used ethernet cable CAT6A 4x2x26AWG in the drag chain.Not using Cavo Ethernet CAT6A specifically designed for drag chains.

Malfunctions began to occur after 32 days of production: the robot reported communication loss when it reached its extreme position, the camera screen intermittently went black, the average downtime per shift was 2-4 times, and each restart took 30 minutes for debugging. The daily production capacity directly decreased by 20%.

Because the other high flexibility cables in the equipment drag chain were provided by the author, when the ethernet cable malfunctioned, the customer’s purchaser contacted the author immediately, hoping that the author could provide a solution. The author arrived at the customer’s site, and the customer’s engineer disassembled and dissected the faulty cable, discovering two core issues:

1.The specifications of the ethernet cable are twisted pair shielded 4x2x0.14mm ² (26awg), and the conductor of each core is 7 strands of 0.16mm thick copper twisted. After long-term repeated bending, the outer copper wire is extensively fatigued and broken, with only a small amount of copper wire maintaining conductivity. The impedance jumps during motion and stretching;

2.Single layer aluminum foil shielding without copper mesh weaving, high-frequency electromagnetic interference directly penetrates welding machines and servo frequency converters, crosstalk exceeds the standard under 500MHz bandwidth, and a large number of 10Gbps data streams are lost.

The solution provided by the author to the client:

Replace all Cavi per catene portacavi in ​​PUR CAT6A with S/FTP double-layer shielding and 49 strands of ultra-fine twisted conductors. After replacement, it operated continuously for 13 months without any communication alarms, and the OEE of the production line returned to normal. The procurement cost of a single ethernet cable is 40% higher, but the monthly downtime loss is reduced by more than 60000 yuan, and the investment return gap is very obvious.

Some insights gained from years of experience:

In recent years of working on automation wiring harness matching, the deepest feeling is that many industry engineers do not attach importance to the ethernet cable used for drag chain, underestimating the impact of the ethernet cable on the stability of the entire production line. Ordinary Ethernet cables cannot be used for reciprocating motion in drag chains，Instead of spending several times the cost of repairing and reworking after a fault shutdown, it is better to match the dedicated high flexibility ethernet cable CAT6A according to dynamic working conditions in the early stage and standardize the construction wiring.