German loehr springs loehr models loehr prices

loehr springs are helical springs that withstand compressive forces. The cross-section of the material used is mostly circular, but rectangular sections and multi-strand steel wires are also used. Springs generally have equal pitch. The shapes of compression springs include cylindrical, conical, convex, concave, and a small number of non-circular shapes. There is a certain gap between the coils of the compression spring. When subjected to external loads, the spring contracts and deforms, storing strain energy. Compression springs provide resistance to external compressive loads. Compression springs use multiple open coils to provide resistance to external pressure (such as gravity pressing down on wheels, or body weight pressing on a mattress). That is, they push back to resist external pressure. Compression springs are generally wound with metal wire at equal pitch and have a fixed wire diameter. In addition, there are conical compression springs, or springs combining conical and straight sections. Depending on the application area, compression springs can be used to resist pressure and/or store energy. Round wire is the most commonly used for compression springs, but compression springs made from square, rectangular, and special-shaped wires are also available.

loehr spring principles

When leaf springs are installed in an automobile suspension and the vertical load is positive, each spring leaf deforms under force, tending to arch upward. At this time, the axle and frame move closer together. When the axle and frame move apart, the positive vertical load and deformation on the leaf spring gradually decrease, sometimes even reversing. The eye of the main leaf is severely stressed and is a weak point. To improve the stress condition of the main leaf eye, the end of the second leaf is often bent into an eye that wraps around the outside of the main leaf eye, known as a wrap eye. A larger gap is left between the main leaf eye and the second leaf wrap eye to allow relative sliding between the leaves during elastic deformation. Some suspensions do not form eyes at the ends of the leaf springs but use other support connection methods, such as rubber support pads. Flat rectangular steel plates are curved and stacked to form chassis springs. One end is installed on the hanger with a pin, and the other end is connected to the frame beam with a shackle, allowing the spring to expand and contract. This is suitable for medium and large trucks. Automobile leaf springs are very important. As is well known, leaf springs are composed of many steel leaves that are elastic, have consistent width and thickness, but vary in length. Their function is to connect the frame and axle in a suspended manner, exposed between the frame and axle, bearing the load impact of the wheels on the frame, reducing severe vehicle vibration, and maintaining driving stability and adaptability to different road conditions. When leaf springs bear load impacts, they undergo extension motion, causing strong friction between the steel leaves, i.e., compression and tension phenomena. The two friction surfaces generate frictional forces in different directions, causing the temperature of the leaf spring to rise, resulting in surface scratches and fine cracks. As the frequency of load impact increases, the frictional force generated by the extension motion also increases. When the stress concentration point reaches the fatigue limit, it will cause single-leaf or entire-stack fracture. Tests based on the principles of kinematics prove that when a steel component undergoing compression-extension motion increases in frequency, its temperature rises and strength decreases. Cracks appear at stress concentration points and gradually expand and deepen, leading to damage at the fatigue limit. Leaf springs are similar, but they have higher elasticity and are more durable than general steel components. Apart from other causes, the main reason for leaf spring fracture is poor lubrication, which should be taken seriously by drivers and technical management personnel. Timely lubrication of leaf springs should be performed to reduce friction and disperse stress, preventing surface scratches on the steel leaves; reduce the intrusion of dust, dirt, and water to prevent rust; and dissipate heat to prevent a decrease in elastic strength. The general lubrication method is: perform lubrication after the new vehicle break-in period ends, and during use in summer and winter. For lubrication, first remove the leaf spring, open the center bolt to separate the steel leaves, then evenly apply lithium-based grease or graphite grease to both sides of the steel leaves. After reassembly, an oil film is formed between the two friction surfaces (completing the lubrication of one set of leaf springs takes only the time required to replace one broken leaf).

loehr spring measures to control springback

1) Select materials with good bending performance: Using materials with low yield limit and high elastic modulus as bending parts can achieve higher bending quality. In addition, the thickness tolerance of the blank, the quality of the surface finish, and the flatness have a significant impact on bending springback. For workpieces with high bending accuracy requirements, the quality of the blank in these aspects should also be screened. 2) Select a smaller relative bending radius: A small r/t value indicates a large degree of deformation. Generally, when r/t ≤ 3-5, it is considered that the bending zone of the sheet metal has fully entered the plastic state. A smaller bending radius is beneficial for reducing springback, but an excessively small bending radius may cause cracking in the bending zone. The minimum bending radii for materials provided in references are mainly absolute empirical data, which can serve as a reference for sheet metal designers when designing the bending radius of workpieces. 3) Select the required die clearance: For V type bending, the clearance value is achieved by high-speed machine tools and is independent of the die itself. For U type bending, springback decreases as the depth of the die opening increases, and springback decreases as the die clearance decreases. For workpieces with high bending accuracy, the single-side bending clearance can be taken as Z = t; if higher bending accuracy is required, bending with slight thinning is more effective in reducing springback. Because zero or negative clearance bending can change the stress state of the sheet metal, transforming ordinary bending into bending with tensile characteristics, putting the inner side of the neutral layer of the blank under compressive stress, so that the entire cross-section of the blank is in a tensile stress state in the tangential direction. After unloading, the springback of the inner and outer fibers cancels out, reducing springback (Figure 4). Therefore, using tensile bending processes and dies with adjustable clearance is very beneficial for controlling springback. 4) Design reasonable workpiece shapes: U type bending parts have less springback than V type parts. Complex workpiece shapes involve more mutual constraints between parts, making springback difficult to control. Therefore, ? type springback is smaller than U type. If suitable reinforcing ribs are pressed at the bending location, springback is even smaller. Therefore, flanging or hemming treatment of bending parts can both increase stiffness and reduce springback. 5) Adopt appropriate microstructural states: Materials after cold working hardening have large bending springback. For bending parts with high accuracy requirements, if the blank has cold working hardening, it should be annealed before bending. Where necessary and permissible, heating the blank during bending should be used to eliminate springback for thicker blanks. The springback angle in corrected bending is significantly smaller than in free bending, and the greater the correcting force, the smaller the springback. 6) Correct the shape of the bending punch: This is because the correcting bending force concentrates the punching force in the bending deformation zone, forcing the inner metal to be compressed. After the sheet is corrected, both the inner and outer fibers are elongated and will shorten after unloading. Since the springback trends of the inner and outer layers are opposite, the amount of springback will be reduced, thereby achieving the goal of overcoming or reducing springback. Therefore, corrected bending is a bending method similar in nature to tensile bending, and its application range is wider. Generally, the shape shown in Figure 5 is mostly used for corrected bending punches.

loehr spring compensation method for controlling springback

The compensation method for controlling springback involves controlling the geometric shape and dimensions of the working part of the die based on the direction and magnitude of the springback of the bending part, so that the springback after bending the workpiece is compensated. For example, for U shaped parts with large bending, the end face of the punch or the surface of the stripper plate can be made arc-shaped, or the punch and die can be made into inclined surfaces at a certain angle, so that the deformation generated at the arc or inclined areas during unloading can compensate for the springback deformation of the two corners. Extending from this, the bending compensation method can be used to bend workpieces that are difficult to bend using conventional methods. For the shape shown in Figure 8, the two sides are tightly closed with no forming space. Using deformation springback and correction compensation methods, bending can be achieved.

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