At present, the processing equipment and processing lines of mechanical springs are developing toward the depth and breadth of numerical control (NC) and computer control (CNC). However, with the changes in spring materials and new geometric shapes, the processing technology has also developed.
1) Variable spring outer diameter, variable pitch, and variable wire diameter (three-variable) Suspension springs achieve moldless machining. Since the development of the three-variable springs, taper steel rods have been used for winding on CNC lathes, but the yield and price are not satisfactory. It is now replaced by a coil spring machine under heating conditions to control the roll speed and pull-out force to obtain the required cone shape and quench with the process residual heat.
2) Hollow-stabilized spring rods are rolled and welded using low-carbon boron steel.
3) The torsion bar is made of high-purity 45 steel. After high-frequency quenching, the surface has a high hardness and a large residual compressive stress, thereby improving the fatigue life and the ability to resist relaxation.
4) The widely used sheet springs for electronic products are basically formed by stamping and automatic bending. At present, it is mainly the development of joint technology of composite materials.
(1) Spring cold forming process
1) One-time automation capability of cold forming process. Cold forming machines have now been developed to 12 claws. Wires in the range of (0.3 to 14) mm are basically formed once in an 8-jaw forming machine. At present, the development direction of the forming process equipment: 1 to improve the forming speed, the main trend is to improve the forming speed of the equipment, that is, production efficiency; 2 to improve the durability of the equipment by improving the precision of the equipment parts and enhance the heat treatment effect; 3 increase the length of the sensor and Laser distance meter, automatic closed-loop control manufacturing process for CNC forming machine.
2) Cold forming process range capabilities. At present, the large-diameter spring coil spring machine has a maximum specification of 20mm, =2000MPa, and a convolution ratio of 5. The cold forming process of the Minic-Block springs and eccentric springs for reducing or equal-diameter materials is still limited.
(2) Spring thermoforming process
1) Thermoforming process speed capability. At present, China only has CNC2 axis hot coil spring machine on the (9~25)mm specification, and the maximum speed is 17 pieces per minute. Compared with developed countries, there is a big gap.
2) Large spring thermoforming process control capability. Because only the CNC2 axis hot coil spring machine, so the shape control less three directions role, the accuracy is poor; and no automatic bar rotation control and adjustment mechanism, so the hot coil spring forming process level and ability is low. Therefore, the accuracy level of the spring and the surface oxidative decarburization level are also low.