Development of spring processing technology
At present, the processing equipment and processing production line of mechanical spring are developing towards the depth and width of numerical control (NC) and computer control (CNC). However, with the change of spring material and geometry, the processing technology also develops.
1) Variable spring outer diameter, variable pitch and variable wire diameter (triple variable) suspension springs are mouldless. Since the development of triple spring, the tapered steel bar has been used for winding processing on the CNC lathe, but the yield and price are not ideal. Now, it is changed to use the spring coiling machine to control the roll speed and drawing force, obtain the required cone shape, and use the processing waste heat for quenching.
2) The hollow stable spring rod shall be rolled and welded with low-carbon boron steel plate.
3) High-purity 45 steel is adopted for torsion bar, and high hardness and large residual compression stress of surface are obtained through high-frequency quenching, so as to improve fatigue life and anti-relaxation capacity.
4) The leaf springs widely used in electronic products are basically formed by punching and automatic bending. At present, the joint technology of composite materials is mainly developed.
(1) Cold forming process of spring
1) One-time automation capacity of cold forming process. The cold forming machine has been developed to 12 jaws recently. Wires within the range 0.3-14mm are basically formed in one step on the 8-jaw former. Development direction of forming process equipment: ① improve forming speed, and the main development trend is to improve forming speed of equipment, i.e. production efficiency; ② Improve the durability of equipment by improving the precision of equipment parts and strengthening the heat treatment effect; ③ Length sensors and laser range finders are added to provide automatic closed-loop control of the manufacturing process for the CNC forming machine.
2) Capability of cold forming process range. At present, the spring coiler with large wire diameter has a maximum specification of φ20mm, σb= 2000MPa, winding ratio 5. The cold forming process of reducing or equal-diameter material Mini — Block spring and eccentric spring is still limited.
(2) Hot forming process of spring
1) Speed capability of hot forming process. Currently, China is only available for the φ 9~ φ 25mm specification with a CNC2 axis hot coil spring machine, with a maximum speed of 17 pieces per minute. Compared to developed countries, there is a significant gap.
2) Control capability of large spring hot forming process. As there is only CNC axis hot spring coiling machine, the shape control is less than three directions, and the precision is poor; Moreover, there is no automatic bar stock rotation control and adjustment mechanism, so the forming process level and capacity of hot coil spring are low. Therefore, the accuracy level and surface oxidation and decarbonization level of the spring are also low.
