Swaging is not flattening the ferrule

Aluminium swaging fits a ferrule over the rope end and compresses it radially with dies so the ferrule metal flows and closes onto the wires. It is controlled cold forming, not flattening and certainly not glue or welding.

Too little compression and there is not enough grip between ferrule and wires; too much and the ferrule cracks or the wires are crushed. The aim of process control is to keep compression inside its specified window. Compression is usually judged by the across-flats dimension or outside diameter after swaging, measured at the positions and with the tools the maker specifies.

Swage or splice: when to choose swaging

Swaging gives high termination efficiency, a compact outline and good batch consistency, which suits factory production. Splicing needs simple tools and can be repaired on site, but quality depends more on the hand.

Rope construction affects the result. The number of outer wires, strand size and whether the rope is compacted decide how evenly the wires load up when the ferrule closes; confirm the match against ferrule maker data and rope construction, and for construction differences see wire rope strand construction

One ferrule does not serve every construction. When the rope construction or supplier changes, reconfirm ferrule, dies and pressure settings instead of carrying over the old process. When the construction changes, swage a few samples first and confirm dimensions and appearance before running the batch.

Ferrule material and rope matching

Aluminium ferrules are usually made in an alloy grade matched to the rope, with bore, wall and length designed for the rope diameter and construction. A mismatch can leave voids or over-press local areas after compression. The ferrule length must cover the specified swage zone; a short ferrule can be pressed hard and still have too little effective grip length.

Steel ferrules serve higher loads or special requirements and need greater compression force, so die and press capacity must rise accordingly. Aluminium and steel ferrules cannot share one set of parameters.

Aluminium in contact with steel wire carries a galvanic corrosion risk, so wet sites need sealing and protection. Oxide film, oil and burrs on the ferrule must be cleaned off before swaging.

Dies: size, shape and wear

The die bore and size decide the ferrule shape after compression. Oval and hexagonal dies are common; which one to use is set by the ferrule maker and cannot be swapped at will.

Dies are usually marked with the ferrule size and rope diameter they serve. The wrong die gives too much or too little compression, and the result may not be visible from outside.

Dies wear. As the bore grows, the same pressure produces less compression; cracks, chipped edges or dents in the die transfer defects to the ferrule. Dies should be measured and recorded at intervals. Upper and lower dies must be used as a pair; mixing dies with different wear produces ovality and off-centre pressure.

Press and pressure calibration

The gauge reading on a press is not the actual pressure the ferrule sees. Hydraulic condition, die clearance and ferrule size all affect transfer, so calibration follows the maker's method.

Calibrate with a standard test piece or load cell and record the relationship between pressure and compression. Recalibrate after changing dies, servicing the hydraulics or a long shutdown. Calibration records should trace back to machine number, dies and date.

The operator must know the day's settings rather than judging by eye that it looks about right. One batch should run on one calibrated set of parameters, with records kept. At the start of each shift, press a trial piece and confirm press-mark depth and appearance before running production.

Swage sequence and overlap

Swage sequence affects stress distribution in the ferrule and load transfer into the rope. Generally start at the rope-entry end and progress toward the eye, with each press overlapping the last, following the ferrule maker's written procedure.

Too little overlap leaves an uncompressed band that becomes the start of slip; too much overlap means pressing the same area repeatedly, work-hardening the ferrule and starting cracks. Do not reverse direction halfway through; a turning point tends to receive double compression and a stress concentration.

Rotate the assembly during swaging so compression is even around the ferrule and ovality stays within limits. Mark each press position so the work can be traced.

Burrs, ovality and appearance

Swaging raises burrs or flash at the die parting line, which should be dressed as specified, but never grind the ferrule body over a large area, because that thins the wall. Deburr along the ferrule axis; a crosswise file stroke leaves transverse scratches that can become crack starters.

Ovality measures how evenly the ferrule was compressed. Beyond the maker's limit, contact between ferrule and wires is uneven and grip falls. For how to measure, see wire rope dimensional inspection

Visual inspection also covers cracks, continuity of press marks, wires extruded at the ends and alignment of rope and ferrule. A cracked ferrule is scrapped, never repaired.

Proof load and sampling

After swaging, apply proof load as the standard or project requires. Proof load is usually a multiple of the rated load, set by the standard and termination type in force; for how the safety factor is chosen, see the wire rope safety factor guide

Batch production also needs sampling, covering appearance, dimensions and destructive tests at the frequency set by the standard or contract. Destructive results must reach the specified termination efficiency, not merely stay unbroken. Sample pieces must be drawn at random from the batch, not chosen for the best appearance.

Keep ferrule batch number, die number, pressure settings, operator and inspection records for each batch. When something goes wrong, those records are the only route back to the cause.

Common defects and their causes

Under-swaging is the most common defect: shallow press marks, high ovality and slip under load. Causes include low pressure, worn dies or a ferrule that does not match the rope.

Over-swaging cracks the ferrule or crushes wires, and broken wires then start in the swaged zone. Causes are usually excessive pressure, an undersized die or repeated pressing.

Wires damaged by the cutting tool before swaging, a misaligned ferrule, oil on the rope end and mixed ferrule batches all cause early failure. Such defects may not show at despatch but appear in service. Cut the rope end with a proper cutter or abrasive disc; the cut should be square, with no loose strands or heat discolouration.

To have ferrules and swaging matched to rope diameter and termination type, state load, rope construction and service environment through the wire rope quotation page