Câble plat pour un vélo de voyage à découpe oxyacétylénique

A cutting car does not move once and stop. It runs the same path continuously, so the cable is bent in the same places, in the same direction, thousands of times. A flat construction answers that duty in ways a round cable does not.

It bends in one plane. With the cores side by side, the neutral axis of the bend stays predictable and each conductor sees a consistent strain every cycle. In a round cable the cores are helically stranded, so the same bend loads different conductors differently along the length.

It does not corkscrew. Repeated pulling along a fixed path makes round cables untwist and take a permanent spiral set — what port and mining engineers call corkscrewing. A flat profile has no lay to open up.

It sits flat in a guide or festoon trolley. Flat cable stacks and rides without rolling, which is why flat constructions dominate festoon systems and machine travel guides.

It has a low build height, which helps where the machine route is a shallow channel or a tight guide.

Steel-plant cutting machines combine two loads that are individually manageable and jointly difficult: continuous movement et heat. The cable has to stay flexible while operating near its thermal limit, which is the opposite of what most compounds do as they age.

The usual exposures on this kind of route are radiant heat from the workpiece and the cutting head, slag and spark spatter, mill scale abrasion along the guide, and cutting oils or coolants. Standard rubber and PVC compounds are out of scope above roughly 90 °C continuous; silicone rubber covers the 180–200 °C band, and fluoropolymers such as PFA extend to around 250 °C. Silicone is mechanically soft, so where spatter or abrasion is present it needs a glass braid or protective covering.

Which of these actually governs depends on how close the cable route runs to the cutting head — something to be measured on site rather than assumed from a datasheet.