At present, the processing equipment and production line of mechanical spring are developing to 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 outer diameter, variable pitch and variable steel wire diameter (three variable) can be machined without molding. Since the development of three variable spring, tapered steel bar has been used for winding on CNC lathe, but the yield and price are not ideal. Now it is changed to control the roller speed and drawing force by spring coiling machine under heating state to obtain the required cone shape and quench it with processing waste heat.
2) The hollow stable spring rod is rolled and welded with low carbon boron steel plate.
3) The torsion bar is made of 45 steel with high purity and high frequency quenching to obtain high hardness and large residual compressive stress on the surface, so as to improve the fatigue life and anti relaxation ability.
4) The leaf spring widely used in electronic products is basically formed by stamping and automatic bending. At present, the joint technology of composite materials is mainly developed.
(1) Cold forming technology of spring1) One time automation capability of cold forming process. The cold forming machine has developed to 12 claws. The steel wire in the range of (0.3-14) mm is basically formed in one step by 8-claw forming machine. At present, the development direction of forming technology and equipment is as follows: ① increasing the forming speed, the main development trend is to improve the forming speed of the equipment, that is to say, the production efficiency; ② to improve the equipment durability by improving the precision of the equipment parts and strengthening the heat treatment effect; ③ adding the length sensor and the laser range finder to control the manufacturing process of CNC forming machine automatically.
2) Cold forming process range capability. At present, the maximum size of spring coiler with large wire diameter can reach 20 mm, = 2000 MPa, and the winding ratio is 5. The cold forming process of minic block spring and eccentric spring with variable diameter or equal diameter is still limited.
(2) Hot forming technology of spring
1) Speed capability of hot forming process. At present, only CNC2 shaft hot coiling machine is used for forming (9 ~ 25) mm in China, with the maximum speed of 17 pieces per minute. Compared with developed countries, there is a big gap.
2) Large spring hot forming process control ability. Because there is only CNC2 axis hot coiling spring machine, the shape control has less effect in three directions, and the precision is poor; moreover, there is no automatic bar rotation control and adjustment mechanism, so the forming process level and ability of hot coil spring are low. Therefore, the accuracy level and surface oxidation decarburization level of the spring are also low.