On a wire and cable line, the caterpillar haul-off is the machine that pulls the product through — and the steadiness of that pull is what decides whether your cable holds its dimensions from the first metre to the last.
What a caterpillar haul-off does
Positioned after the extruder and cooling trough, a caterpillar haul-off grips the cable between two continuous belts and draws it through the line at a precisely controlled speed. The name comes from those belt tracks, which give a long, distributed, slip-free grip — enough traction to pull the line without crushing or marking the insulation.
Why line tension is everything
The haul-off sets the line speed, and line speed measured against the extruder's output is what fixes the insulation or sheath wall thickness. So if the haul-off surges, slips or drifts, the consequences show up immediately in the product:
- Diameter varies — the cable drifts out of tolerance and fails inspection.
- The conductor can stretch under uneven pull, changing electrical properties.
- The take-up struggles to spool cleanly when feed speed is inconsistent.
This is why consistent, slip-free traction and speed control synchronised with the rest of the line are the entire purpose of the machine.
In one line: the extruder decides how much material goes on; the haul-off decides how fast it is pulled away. Together they set the dimension — so the haul-off has to be rock-steady.
What makes a good haul-off
- Belt length and grip area matched to the product — heavier cable needs a longer grip to pull without slip.
- Servo or VFD speed control synchronised precisely with line speed.
- Adjustable belt pressure to grip firmly without deforming softer insulation.
- Smooth acceleration so start-up and speed changes do not shock the line.
Caterpillar or capstan?
A caterpillar (belt) haul-off offers a long, gentle, distributed grip, which suits insulated cable and delicate products. A capstan wraps the product around a driven wheel, which suits bare wire and rod. For most insulated wire and cable work, the caterpillar type is the standard choice.
The haul-off is one link in a tension chain
Pay-off, extruder, cooling, caterpillar haul-off, and take-up all have to move in step, with the haul-off acting as the pace-setter. A mismatch anywhere along that chain reveals itself as diameter variation or spooling problems — which is why the haul-off and take-up are specified together with the extrusion line, not bolted on afterwards.