Spring leaves are sized to the required lengths, they are subjected to various processes like punching, eye rolling, cover/wrapper rolling, endcropping, taper rolling, and so on. A state of the art fully computerised Taper Rolling machine for the manufacture of Parabolic springs is available with the company.
After being heated in a Furnace ,the leaves are passed on to the taper rolling mill, where the parabolic curve is created on the leaves. This operation being fully controlled by the Computer, in which the parabolic co-ordinates are stored.
The spring leaves are then fed into a walking beam furnace with automatic temperature controls where they are heated to the critical temperature depending upon the grade of the material used .
After attaining the correct temperature, the spring leaves are placed on a combined leaf spring cambering and hardening machine where the spring leaves are cambered to a predetermined curvature .Simultaneously they are oil hardened by the rotation of the drum type cambering machine into the quenching oil bath. By this operation of rapid oil quenching at the critical temperature, the grain structure of the spring leaf is transformed to martensite, which imparts the required hardness to the leaf.
The spring leaves are then fed into a conveyorised tempering furnace, passing through various temperature zones with automatic temperature controls, to relieve the stresses developed due to oil hardening. The spring leaves are then checked to ensure that they have attained the required hardness and tempered martensite structure. Next, the spring leaves are passed through a shot penning machine, which induces a residual compressive stress on the surface, thereby increasing the fatigue life of the spring. The spring leaves are then processed, after application of Zincrich primer / Graphite Primer undercoating. The spring leaves thus processed are assembled into a leaf spring assembly on a Hydraulic Assembling Machine to the required camber. The spring assembly is subje- cted to a scragging operation by deflecting it by an amount which will develop a maximum stress equal to 90% of the yield stress of the material after heat treatment. This operation ensures that the spring will not take any further set when in use on the vehicle. The spring assemblies are finally degreased, derusted and spray painted with anti-corrosive paint and baked in an oven to achieve the necessary anticorrosive properties.