Leaf Spring Manufacture
Manufacturing of leaf springs can be divided in to three broad areas:
- Preparing leaves
- Bending - heat treatment - shot peening
- Assembling - presetting - surface treatment
Leaves for multi-leaf springs are prepared by cutting and stamping whilst parabolic leaves are hot rolled in a purpose-made rolling machine. The ends of the main leaf are heated and the eyes are then hot rolled. The leaves are heated and individually bent to the correct arc radius and, whilst still clamped between the bending tool, each leaf is quenched in oil to receive high strength and the correct shape. Parabolic leaves also have an arc radius but are however normally straight in the thicker central section. The leaves are finally tempered for high material toughness and strength.
After cooling, the shot peening process is necessary for all parabolic leaves. For multi-leaf springs however, it is normally only the two safety-critical leaves that require shot peening. The bushes are pressed into the eyes and the stack of leaves assembled. Positive stresses are then introduced into the spring by a pre-stressing process.
The multi leaf surfaces are protected against corrosion by painting of the outer surfaces and by lubrication between each leaf. Parabolic leaves are individually painted on all surfaces.