The manufacturing process of the coil spring includes: a) roll-up, b) the production of hooks or finishing of the end face, c) heat treatment, d) process testing and pressure treatment.
Roll is to wrap the technically specified spring wire on the core rod. When mass production is made on a universal automatic reed machine, and in single pieces and small batches, in a regular lathe or manual winding machine.
Roll divided cold rolls and hot rolls two kinds. Cold rolls are used for spring wire with a diameter of d (8 to 10) mm after pre-heat treatment, and a strong spring made of larger diameter spring wire is a hot roll. The temperature at the hot roll is selected in the range of 800 to 1000 degrees C with the thickness of the spring wire. Whether cold or hot, the spring’s pitch should be adjusted as necessary, depending on the circumstances.
The spring should be heat treated after completing the above operation. There should be no significant decarbonization layer on the surface of the spring after heat treatment. The spring after the cold roll is only tempered to eliminate the internal stress generated when rolled.
In addition, the spring must be carried out process tests and in accordance with the requirements of the spring technical conditions for precision, impact, fatigue and other tests, in order to verify that the spring meets the technical requirements. In particular, the long-lasting strength and impact strength of the spring depends to a large extent on the surface condition of the spring wire, so the surface of the spring wire must be clean, no cracks and bruises and other defects. Surface decarbonization can seriously affect the long-lasting strength and impact resistance of the material. Therefore, the decarbonization layer depth and other surface defects should be specified in the technical conditions of the acceptance spring. Important springs are also subject to surface protection (e.g. galvanizing);
For important springs, it is also subject to strong pressure treatment. The pressure treatment is to carry the spring under the action of the extreme load for 6 to 48h in order to produce plastic deformation and residual stress in the hazardous area of the spring wire cross-section. Because the residual stress is the opposite of the operating stress symbol, the maximum operating stress of the strong pressure treated spring is small, and a single pressure treatment can improve the carrying capacity of the spring static load by 25%. It can be improved by 20% if treated with a shot. However, springs for long-term vibration, high temperature and corrosive media, as well as springs for general use, are not suitable for this reinforcement process.
Spiral stretching, twisting spring manufacturing, in addition to a few manufacturing plants in the introduction of foreign CNC spring forming machine once automatically forming a variety of patterns of stretching, twisting spring. The vast majority of manufacturing plants still use traditional processing methods to manufacture, now make a simple introduction.
1, the coil stretch spring. The process is basically the same as the coil compression spring, different is just the end of the hook ring processing, the tensile spring is formed as follows:
1) With the same method as the coil compression spring, winding after forming destressed annealing, and then hook ring processing, in addition to special shape hook ring or require strain high initial pull of the spiral stretch spring car bed with heart roll or hand roll, most of the spring is made with automatic reed rolling.
2) With a straight-tailed reed machine roll. It is a vertical reed machine with a spindle vertical. After rolling, destressed annealing, and then hook-ring processing. The end structure of the coil-stretching spring is in many forms, and there are many processing methods. Commonly used are: small springs using pliers-type special tools or special process devices for manual processing, ordinary coil edging spring with a hooker or mold with manual or automatic operation methods, long arm hook ring stretch ingenuity spring, generally when winding to leave the required material length, or roll out the required number of rings for processing, with straightening tools to straighten the two ends, and then with a special tool to bend the hook ring. The process specification for destressing annealing is described above. Spring rolled up after the first destressed annealing, and then cut off and hook ring processing, hook ring processing, generally 1 to 2 times to destress annealing. In order to prevent the relative angle of the two hook rings from changing, the temperature after the finishing processing of the hook ring should be 20 to 30 degrees C lower than that after the roll-up. The coil stretch inglis spring generally does not carry out blasting and strong pull treatment.
2, the coil twist inge spring. Its process and spiral compression, stretch ingenuation spring is basically the same, different also embedded in the instant-comcon? In small batch production and twisting arm is more complex case, most of the use of manual or semi-automatic with the central scroll reed method forming, and then the use of a clamped arm will be twisted arm according to the pattern requirements for processing. In the mass production, can be in the straight-tail reed machine and twisting reed special machine roll, twisting arm can not be completed according to the pattern, and then sub-process editing, fixtures to process. Depending on the characteristics of the coil-twisting spring, the following two points should also be noted when designing and manufacturing:
1) The spiral torsional spring end twisting arm should be bent and formed once during manufacture to avoid machining defects and correction plastic surgery. After the torque arm processing should be carried out a second destressed annealing;
2) The current coil twisting spring is mostly dense, so that between the spring rings produces a similar tensile of the initial pull force of the spring, in the loading and unloading will produce friction altogether phenomenon, when loading and rotation of the same or increase dummy, this tendency increases; Therefore, there should be a gap between the spring rings when designing and forming. In a large number of production, the manufacturing plant in the condition of conditions, the spiral stretching, twisting spring expansion, bending, bending and other processes can be processed by hydraulic, pneumatic and other methods.