At present, the processing equipment and production line of mechanical spring are developing towards the depth and breadth of numerical control (NC) and computer control (CNC). However, with the change of spring material and geometry, the processing technology has also developed.
1) The suspension spring with variable spring outer diameter, variable pitch and variable wire diameter (three variations) realizes non molding processing. Since the development of the three variable spring, the tapered steel bar has been used for winding on the CNC lathe, but the yield and price are not ideal. Now, the roller speed and drawing force are controlled by the coil spring machine in the heating state to obtain the required cone shape and quench with the processing waste heat.
2) The hollow stable spring rod is formed by rolling and welding low carbon boron steel plate.
3) The torsion bar is made of high-purity 45 steel. After high-frequency quenching, high hardness and large residual compressive stress are obtained on the surface, so as to improve the fatigue life and anti relaxation ability.
4) Leaf springs widely used in electronic products are basically formed by stamping and automatic bending. At present, the joint technology of composite materials is mainly developed.
(1) Cold forming process of spring
1) One time automation capability of cold forming process. The cold forming machine has been developed to 12 claws. The steel wire within the range of (0.3-14) mm is basically formed at one time by the 8-jaw forming machine. At present, the development direction of the forming process equipment is: ① improve the forming speed, and the main development trend is to improve the forming speed of the equipment, that is, the production efficiency; ② Improve the durability of equipment by improving the precision of equipment parts and strengthening the heat treatment effect; ③ The length sensor and laser range finder are added to automatically control the manufacturing process of CNC forming machine.
2) Scope and capability of cold forming process. At present, for large wire diameter spring coiling machine, Z large specification can reach 20mm, = 2000mPa, and the winding ratio is 5. The cold forming process of minic block spring and eccentric spring with variable or equal diameter materials is still limited.
(2) Hot forming process of spring
1) Speed and capability of hot forming process. At present, there are only CNC2 axis hot coil spring machines in China with the size of (9 ~ 25) mm, and 17 pieces per minute at Z-speed. Compared with developed countries, the gap is large.
2) Large spring hot forming process control ability. Since there is only CNC2 axis hot coil spring machine, there are less three directions for shape control and the accuracy is poor; Moreover, there is no automatic rod rotation control and adjustment mechanism, so the forming process level and capacity of hot coil spring are low. The accuracy level and the surface oxidation decarburization level of the spring are also low.
