Cylindrical spiral spring manufacturing
The spiral spring manufacturing process includes: a) rolling; b) production of hooks or finishing of face rings; c) heat treatment; d) process testing and high pressure treatment.
Rolling is the winding of a spring wire that conforms to the technical conditions. In mass production, it is wound on a universal automatic coil spring machine; in single-piece and small-batch production, it is rolled on an ordinary lathe or manual winder.
Rolling system is divided into cold roll and hot roll. Cold coils are used for spring wires of diameter d<(8-10) mm drawn after pre-heat treatment; hot springs of larger diameter spring wire are used for hot coils. The temperature at the time of hot coiling is selected in the range of 800 to 1000°C depending on the thickness of the spring wire. Regardless of whether cold or hot coils are used, the pitch of the springs should be adjusted as necessary depending on the actual situation.
After the spring has completed the above steps, heat treatment should be performed. The surface of the heat treated spring should not exhibit a significant decarburization layer. Cold coiled springs are only tempered to eliminate the internal stresses created during rolling.
In addition, the springs must be subjected to process tests and tests for accuracy, impact, and fatigue in accordance with the specifications of the spring's specifications to verify that the springs meet the technical requirements. It should be particularly pointed out that the long-term strength and impact strength of the spring depend to a large extent on the surface condition of the spring wire, so the surface of the spring wire must be clean and free of defects such as cracks and flaws. Surface decarburization can severely affect the material's long-lasting strength and impact resistance. Therefore, the decarburization depth and other surface defects should be specified in the technical conditions of the acceptance spring. Important springs must also be surface-protected (such as galvanized); ordinary springs are generally coated with oil or paint.
For important springs, strong pressure treatment is also required. The strong pressure treatment is to make the spring loaded under the limit load for 6-48h, so as to produce plastic deformation and residual stress in the danger zone of the spring wire cross-section. Since the residual stress is opposite to the working stress, the maximum working stress of the spring subjected to the strong pressure is small, and a high-pressure treatment can increase the static load carrying capacity of the spring by 25%. If shot blasted, increase by 20%. However, springs used for long-term vibrations, high temperatures and corrosive media, and general-purpose springs are not suitable for this reinforcement process.
The manufacture of spiral tension and torsion springs, except for a few manufacturers, has introduced a foreign CNC CNC spring forming machine to automatically shape and process various types of tensile and torsion springs. The vast majority of manufacturing plants still use traditional processing methods to manufacture them. Now they are briefly introduced.
1, spiral tension spring. The process is basically the same as the helical compression spring. The difference is only the end of the hook and ring processing, the forming method of the tension spring is as follows:
1) In the same method as the helical compression spring, after stress forming and annealing after winding, hook and ring processing is performed, except for special-shaped shackles or spiral tension springs requiring high initial tensile force. Outside the roll, most of the springs are rolled by an automatic coiler.
2) Rolling with a straight-end coil spring machine. It is a vertical centered coil spring machine with a vertical axis. After stressing, stress relief annealing is performed, and then hook and loop processing is performed. Spiral extension springs have many end structures and many processing methods. Commonly used are: small springs use pliers-type special tools or special process equipment for manual processing; common spiral tension springs are processed with hooks or molds by manual or automatic operation methods; long arm hooks are stretched The spring, usually the length required to leave the hook when winding, or the number of turns required for processing after rolling, straighten the ends with a straightening tool, and then use a special tool to bend the hook and loop. The stress relief annealing process specification is as described previously. After the spring roll is prepared, stress relief annealing is performed first, and then cutting and hooking and ring machining are performed. After the hook and loop processing is completed, a stress relief annealing of 1 to 2 times is generally performed. In order to prevent the relative angles of the two shackles from being changed, the temperature of the shaver-ring after finishing the stress relief annealing should be 20-30°C lower than the temperature after the shawl is finished. Spiral extension springs are generally not subjected to shot blasting and forced drawing.
2, spiral torsion springs. The process is basically the same as spiral compression and tension springs. In the case of small batch production and more complex torsion arms, most of them are formed manually or semi-automatically with a mandrel coil spring method, and then the torsion arms are processed according to the pattern requirements using a fixture. . In mass production, it can be rolled on straight-to-tail coil spring machines and special machines for torsion springs. The twist arm can't be finished according to the pattern, and then processes and fixtures can be used to process. According to the characteristics of spiral torsion springs, the following two points should also be taken into consideration when designing and manufacturing:
1) The torsion arm of the helical torsion spring end should be bent once during manufacture to avoid machining defects and correct shaping. A second stress relief annealing should be performed after the twist arm is finished;
2) The current spiral torsion springs are mostly dense, so that a similar compression force is generated between the springs, which is equivalent to the initial tension of the tension springs. Friction and hysteresis occur when loading and unloading. This tendency increases when the load is the same as the direction of rotation or when the number of turns increases; it also causes difficulty in the surface treatment process. Therefore, when designing and forming, there should be a slight gap between the spring coils. In mass production, under conditions, the manufacturer can use hydraulic and pneumatic methods to process the spiral tension, torsion spring deployment, bending, and hooking.