Rotary Swaging Machine Product

Overview

A rotary swager is a cold-forming machine that shapes tubes and solid rods by radially compressing them between rotating dies. Unlike hammer or drop-forge presses that apply load in one direction, a rotary swager applies load from all sides simultaneously (or alternating if a 2-die design). The dies rotate at 600–3,000 rpm, and as the workpiece feeds into the converging die zone, it undergoes progressive deformation, reducing diameter and changing profile with each revolution. Swaging is used to reduce tube diameters, form tapers, swage fittings onto tubes, and cold-head fasteners. The process is fast (10–100 pieces/min for short stock), requires no heating, and produces a smooth surface finish.

The Spindle Drive Motor drives the Swaging Head Assembly rotor at constant speed. The Automatic Feed System advances material incrementally into the Die Unit units. As the rotor spins, a cam-like mechanism (the Die Linkage) converts the rotor rotation into radial die motion, causing the dies to converge on the workpiece, then expand as the linkage rotates past center, gripping and releasing in rhythm. The Cooling & Lubrication sprays lubricant into the zone, reducing heat and wear. The Control & PLC Cabinet manages speed, feed advance, and cycle timing.

Swaging die motion and cycle

In a 4-die setup, the dies are positioned 90 degrees apart around the rotor. As the rotor rotates, a fixed Guide Ring on the machine body acts like a cam, forcing the dies radially inward, then releasing them outward. The inward motion compresses and shapes the workpiece; the outward motion allows the workpiece (or next piece) to be fed through.

The stroke (radial compression distance) depends on the die geometry and machine design: 2–6 mm is typical. At 1,200 rpm spindle speed with a 4-die setup, each die encounters 1,200 cycles per minute, so the workpiece is compressed 1,200 times per minute — intense work-hardening of the surface.

The Die Linkage is a four-bar mechanism: two links attach each die to a fixed pivot on the rotor, and a third link connects to a roller riding in the fixed guide ring. As the rotor rotates, the guide-ring profile cam pushes the roller, causing the linkage to open and close the die gaps. This is purely mechanical and requires no servo control; the compression force is determined by geometry and machine stiffness.

Material and die design

Swaging works best on ductile materials that work-harden but don't crack: mild steel, copper, aluminum, stainless steel. Titanium and super-alloys require careful control of deformation rate and heat (some swaging generates enough friction to anneal the workpiece locally).

Dies are hardened steel or tungsten-carbide, with profile faces matching the desired shape. A simple reducing die tapers from input diameter to output diameter. A more complex die might form a flange, taper, or swaged-on fitting (like a ferrule on a tube end). Die life is 5,000–50,000 pieces depending on material hardness and the severity of forming.

The dies are consumables; the cost of a die set (2–4 dies per set, plus guide ring inserts) is 500–2,000 USD. High-volume production (> 100,000 parts) justifies the tooling cost; small batches (< 10,000 parts) may be uneconomical.

Feed mechanism and timing

The Automatic Feed System grips the workpiece in a pneumatic or mechanical Material Gripper and advances it into the swaging head at a controlled rate. Feed is synchronized with the spindle rotation: the feed motor makes an incremental step each time the dies close, advancing the material by one "bite" (stroke distance, typically 2–4 mm).

The Feed Motor is a servo motor receiving position feedback from a Encoder on the spindle. The control software counts spindle revolutions and triggers the feed motor to step forward once per revolution (or once per N revolutions for slower feed). This synchronization prevents jamming and ensures uniform swaging along the entire workpiece length.

For tapered or non-uniform profiles, the feed rate is programmed to vary: fast feed through non-critical sections, slow feed (one step per revolution or even sub-revolution) through critical forming zones. This is called "profiled feed" and requires a servo or stepper motor controlled by the Control & PLC Cabinet PLC.

Strain-hardening and surface finish

Cold swaging work-hardens the surface layer, increasing hardness to 60–70 HB on mild steel (vs. 90–120 HB hot-rolled). The surface finish is excellent — 0.4–0.8 µm Ra — because the dies burnish the surface under high contact pressure. No secondary finishing is needed for most applications.

However, the core of the material remains at original hardness. For critical applications (fasteners under cyclic load), the hardness gradient is actually beneficial: the hard skin resists fatigue crack initiation, while the ductile core resists brittle fracture. For fatigue-critical parts, stress-relieving (250–350 °C for 1 hour) is sometimes specified to relax residual stresses.

Dimensional accuracy

Swaging achieves ±0.1–0.2 mm diameter tolerance on a 10 mm workpiece, good enough for most applications. However, length creep — material shortening slightly — occurs with each pass. A 100 mm tube might shorten to 99 mm after swaging. This must be accounted for in upstream cutting operations (add ~1–2 mm stock length to compensate).

Dies wear and open up slightly; as wear progresses, final diameter increases. Periodic die inspection (measure a sample every 1,000–5,000 pieces) detects wear before it exceeds tolerance. Dies are then re-faced (run against a grinding stone to sharpen profiles) or replaced.

Swaging applications

1. Tube reduction: Reducing 20 mm × 1 mm tube to 10 mm × 0.8 mm for compact hydraulic lines.

2. Fastener heading: Forming a bolt head by swaging a rod end; the cold-work improves tensile strength to match the original rod.

3. Ferrule attachment: Swaging a compression ferrule onto a tube end to create a mechanical fitting without soldering or brazing.

4. Taper forming: Creating a conical taper on a pin or shaft for press-fit assembly.

5. Rivet or rivet-nut heading: Forming the head of a specialty fastener.

Tooling and changeover

Changing die sets (e.g., from a 10 mm to a 12 mm reduction) requires removing the old die units and inserting new ones. The Guide Ring and Die Unit blocks are unbolted, swapped out, and re-installed — typically a 30–60 minute job. The Automatic Feed System advance distance must be re-entered into the HMI Display PLC.

The Cooling & Lubrication is critical to manage. Swaging generates heat and metal fines (wear particles). The coolant (usually a water-soluble emulsion) cools the dies and lubricates the workpiece, extending tool life. Every 2–4 weeks, the Coolant Tank is drained and refilled with fresh coolant; the Coolant Filter is replaced to prevent buildup of fines and rancidity.