Forming

Special alloy steel is used for production of coil springs and leaf springs. Round bars of suitable diameter and flat bars of suitable section are supplied by qualified suppliers. After cutting for suitable length, spring leaves and spring bars are heated as forming process takes place while material is hot. Coil springs after coiling and spring leaves after cambering are quenched in oil.


Heat treatment

Steel after quenching, despite its hardness, is too brittle to be used in vehicle suspension. For this reason springs are subject to heating in a suitable temperature so as to achieve such mechanical properties that ensure long product life. This process is called tempering. As a result of tempering, steel hardness is in fact slightly decreased, but high endurance and elasticity is kept.


Shot peening

All leaf springs and coil springs that we manufacture are shot peened. This operation consists in "bombarding" a coil spring or a spring leaf with a stream of small steel balls at high velocity. Owing to that, in a shot peened surface, contracting stress is introduced, which counteracts the occurrence of cracks and increases product fatigue life.


Setting

Setting consists in such deflection of coil springs and leaf springs so as to achieve plastic distortion of the spring. This eliminates or greatly reduces further loss of height during product operation - "settling".


Painting

Another production process is protecting products from corrosion. After phosphatizing springs are powder coated, which ensures both high corrosion resistance and abrasion resistance. Leaf springs are protected by phosphatizing or painting with zinc paint, which, apart from corrosion protection ensures reduced friction between leaves.


Inspection

Product inspection is equally important as production processes described before. Supplies, production processes and products are subject to inspection so as to reduce to the minimum the risk of occurrence of products which do not conform with the requirements. For example, 100% of coil springs are checked for load at a specific design height. On the basis of that check, products are selected into selection groups. Then, during the assembly of springs on one vehicle axle, one selection group is used. Moreover other design parameters are checked with the use of quality statistical control methods so that final product fully conformed with Customers' requirements.