Axle shaft hardening on a vertical scanner

The problem

An axle shaft is long, and the hardened length is most of it. Heating that entire length at once would need an enormous power supply and a coil as long as the shaft, both of which are impractical and neither of which would give a consistent result.

It also has to be hard where it runs and tough throughout, and any distortion introduced by the heat treatment shows up immediately as runout on a part whose whole job is to rotate true.

Our approach

Scanning solves it. The coil and quench ring stay put and the shaft traverses through them, so only a short band is hot at any moment and the quench follows a fixed distance behind. A far smaller power supply hardens a far longer part, and because the thermal gradient travels rather than sitting, distortion is lower than a single-shot approach would produce.

We built this as a PLC induction hardening machine for axle shafts on the ABE-50AB, a 50 kW supply. It can be customised for shaft hardening up to 60 mm diameter along with gears, bushes, JCB parts, tractor parts and flywheel rings.

The PLC holds traverse speed and power constant, which matters more here than anywhere: on a scanner, traverse speed is what sets case depth along the length, and it is the parameter most likely to drift under manual control.

What this achieves

Case depth stays consistent along the hardened length because the machine holds the traverse speed, not because an operator watched the colour.

The same scanner architecture covers 20 mm to 120 mm shafts on ABE-40 kW to ABE-120 kW supplies, so a shop hardening a family of shafts is not buying a machine per part.