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The basic concept of super group bending and bending of heat insulation broken window company

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The basic concept of super group bending and bending of heat insulation broken window company

Date:2014-08-07 Author: Click:

The basic concept of ultra-group stretch bending is to bend sheet metal, pipe and profile into a certain curvature, shape and size of the stamping process of the workpiece. Stretch bending is widely used in the manufacture of high pressure vessels, boiler drums, boiler tubes, steel plates and ribs of the hull, various utensils, instrumentation components and cabinet inserts.

When the material is stretched and bent, the stress state of each part in the deformation zone is different. The middle part of the cross section is not called a neutral layer. Tensile stress is produced by tensile stress outside the neutral layer. The compressive stress is produced by the compression of metal under the neutral layer. Because the stress and strain directions of the metals on both sides of the neutral layer are opposite, when the load is unloaded, the elastic deformation recovery directions of the metals on both sides of the neutral layer are opposite, resulting in different degrees of elastic recovery. Although the tension bending deformation is only limited to the local area of the material, the elastic recovery will affect the accuracy of the bending parts. There are many factors affecting springback, but these factors are difficult to control. The precision of stretch-bending parts caused by springback is always the key to the production of stretch-bending.

The classification of stretch bending

According to the technological characteristics, stretch bending can be divided into top bending, bending, rolling bending and bending.

Bending is the most commonly used bending method. Most of the equipment used is general mechanical press or hydraulic press, and it also has special bending press. The common roll bending equipment is bending machine. The three roll bending machine determines the principle of one circle according to three points, and carries out continuous bending of the slab. The three roll bending machine has two drive rollers (fixed) and one down roll (adjustable). The relative distance between the roller and the driving roller can be changed by adjusting the upper and lower positions of the down roll. When stretching and bending, the sheet metal is placed between the driving roll and the pressing roll, and the driving roll is rotated alternately in the positive and negative directions, thus making the sheet metal reciprocating motion. By adjusting the screwdown roll to gradually press down, the sheet can be bent into cylindrical, conical and hyperboloid surfaces with required curvature. One end of the down roll can be raised to facilitate unloading. In addition, there are four-roll and multi-roll plate rolling machine, four-roll plate rolling machine is used for rolling thick plate cylinder, more than four-roll multi-roll plate rolling machine, with many pairs of rollers will gradually bend the plate into a complex surface.

For bending parts with higher precision, larger length and radius of curvature and smaller transverse dimension, it can be stretched and bent on special stretching and bending machine. In tension and bending, the whole thickness of the plate is affected by tensile stress, so only elongation deformation occurs. After unloading, the deformation caused by elasticity is small, and the accuracy is easy to ensure.

Stretch bending process parameters

Selecting the right machining parameters is the key to the stretch bending process. In addition to the relatively small changes in dies and other factors, the process parameters affecting the quality of stretch bending include stretch force, deformation and so on. There are two main factors restricting the processing of stretch bending in production: one is the fracture of stretch bending, the other is the excessive deformation of section size. Two aspects must be considered before determining the tension and bending parameters. In addition, minimizing elastic recovery is also an important basis for selecting the parameters of stretch bending process. In the process of drawing and bending, the unstable wrinkling phenomenon will occur if the processing parameters are not properly selected, which is also an important factor to be considered. Extruded profiles are considered as a special kind of sheet metal material. The material itself has one dimension which is much smaller than the other two dimensions. Therefore, the extruded profiles can be considered to be completed under plane stress. But the biggest difference between stretch bending and sheet metal forming is that the sheet metal is usually considered to be isotropic, while the anisotropy of extrusion profile is more obvious.


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