Cable Stranding and Insulation Line Automation

There are three main types of stranding machine. On a rigid (cage) strander the bobbins sit on a rotating cage and the wires meet in the closing die as the cage turns; used for conductor and core stranding in power cable. On a tubular strander the bobbins stay still inside a tube and the wires run over the rotating tube; it reaches higher speeds. On a double-twist buncher the reel is stationary and a rotating bow gives two twists per turn; used for bunching fine wires. In all of them rotor, capstan and take-up are the three main axes.

Lay length is capstan line speed divided by rotor speed: lay (mm) = capstan speed (mm/min) / rotor speed (rpm); on a double-twist machine, which gives two twists per turn, this value is halved. On mechanical machines the ratio is fixed by a gearbox and gears are changed at product changes. On an electronic machine the rotor and capstan are driven by separate motors and the ratio is held by an electronic gear in software; lay length changes from the recipe and the ratio is held during acceleration and deceleration. Taping and armouring heads also turn in ratio to line speed in the same way.

The tension of every wire on the pay-off bobbins has to be equal; otherwise one wire is looser than the others in the strand. Tension is held by brakes, dancers or motorized pay-offs. On the take-up, motor speed drops as the reel diameter grows and tension is held by torque calculated from diameter or by a dancer; a traversing guide shifts the cable by one cable diameter per reel turn to build even layers and reverses at the reel flange.

An insulation line runs in this order: pay-off, preheater, extruder and crosshead, cooling trough, diameter and eccentricity gauge, spark tester, capstan, accumulator and take-up. Coating thickness is set by the ratio of extruder output to capstan speed; the diameter gauge signal corrects extruder speed or capstan speed in closed loop. On fast lines an accumulator keeps the line running during reel changes.

In the ONX architecture the capstan is the line master; rotor, taping and armouring heads are geared to it electronically in CODESYS SoftMotion, and lay length changes from the recipe. All axes run on the same ramp so the ratio is held during acceleration, deceleration and emergency stops; braking energy of heavy rotors is managed by regenerative or common DC bus drive structures.

Pay-off and take-up tension are held by dancers or by diameter calculation and torque control; the traverse axis is cammed to take-up speed and flange positions come from the recipe. On insulation lines the extruder, capstan and diameter gauge are on the same controller; thickness is corrected in closed loop and heating zones are held by PID.

The architecture on this page is built on the electronic gear and traverse cam platform ONX Control uses in winder tension control, load sharing and textile yarn machines. We work out your machine's axis layout together in a meeting.

A typical picture on cable machines: lay length fixed by a gearbox with gears changed at every product change, DC motor capstan and rotor, a mechanical traverse or one with no spare parts and pay-offs with tension set by hand. In a retrofit the rotor, capstan and take-up mechanics are kept; an electronic gear replaces the gearbox, the drives are renewed and lay length changes from the recipe.