Q&A With HELU: Design Considerations for Dynamic Applications - Part 1 of 3

Q: How are drag chain and torsion-rated cables designed and manufactured differently from each other?

A: In many ways, with respect to the environment each cable will be installed in, they are very similar. Before those details are discussed, let’s talk about the most basic material found in the majority of industrial cables, the copper strand. The key thing to remember is that all copper strands, no matter how they are drawn, how many are used per conductor, or how they are stranded together, have memory. For example, think of a wire coat hanger. If you bend it in a particular direction and then attempt to bend it back to the original position it will not be exactly as it was before. The same applies to copper strands in a multi-conductor industrial cable. This is fine for stationary or fixed applications, but it creates the most basic of challenges for a cable manufacturer when that cable will be bending millions of times in a 2D (drag chain) or 3D (robotic) application. Without giving away too much of how HELUKABEL designs and manufactures these 2D- and 3D-style cables, managing the memory of each strand and conductor plays a major role in design efforts. The more demanding the mechanical application, the greater the cable’s performance characteristics must be. That means progressing from simple bunch or unilay construction for stationary cable to concentric with a short lay length (2D) or concentric with a longer lay length (3D). As the performance needs increase cables also switch from PVC to PP insulation, and to PUR or TPE jacket compounds.

Q: What are some of the cable design considerations for drag chain-rated cables?

A: There are many characteristics to consider and each machine’s drag chains require a full understanding of the application. To design a new cable or recommend a standard catalog cable, your solutions partner should be asking a lot of questions. This will yield the best results. Some of these questions are related to the mechanical parameters - acceleration, travel speed, travel length and cycles per day. There are environmental considerations as well, which include ambient operating temperature, whether the machine is indoors or outdoors, and the presence of chemicals or particulates that may come in contact with the drag chain, such as welding slag or diesel fluid (seen a lot in the wood processing industry). Some of the desired properties of any industrial cable would be a wide temperature range, sunlight resistance, high oil resistance, minimal elongation, high tensile strength, good abrasion resistance, small bend radius, low capacitance and flame propagation. It is possible to produce cables to meet many if not most of these criteria but the cost to produce such a cable would not be accepted by the market. Since a one-size-fits-all is not desirable for most OEMs and end users due to the cost, it is critical to match the best solution based on the overall application with total system cost as a secondary consideration.