Common Problems and Treatment in Yuanhao Bending Forming Process

Yuanhao Pull BendIs the metal sheet, pipe, profile bending into a certain curvature, shape, size of the workpiece stamping forming technology. Yuanhao bending forming is widely used in the manufacture of high-pressure vessels, boiler drags, boiler tubes, hull steel plates and bone ribs, various instruments, instrument components and packing malls.

When the material is stretched and bent in Yuanhao, the stress state of each part in the deformation area is different. The non-deformed part in the center of the cross-section is called the neutral layer. The metal other than the neutral layer is subjected to tensile stress, resulting in elongation deformation. The metal in the neutral layer is subjected to pressure, resulting in compressive deformation. Due to the opposite direction of the stress and strain of the metal on both sides of the neutral layer, after the load is eliminated, the elastic deformation recovery direction of the metal on both sides of the neutral layer is opposite, causing different degrees of springback. Tensile bending deformation is limited to certain areas of the material, but springback effects affect the accuracy of the bend. There are many factors that affect the springback, but these factors are difficult to control, and the precision problem of bending components caused by springback is the key to bending forming production.

1. Classification of Yuanhao Bend

According to the characteristics of the process, Jinan stretch bending can be divided into top bending, bending, roll bending and bending

Yuanhao bending is a commonly used bending method. Most of the equipment used is a general mechanical press or hydraulic press, and there are also special bending presses. The commonly used roll bending equipment is a plate bending machine. The three-high rolling mill continuously bends the slab on the grounds of a circle at three points. 3 The roller mill has 2 driving rollers (fixed) and 1 pressing roller (adjustable). The relative distance from the driving roller can be changed by adjusting the upper and lower positions of the pressing roller. When bending, the plate is placed between the driving roller and the pressing roller, and the driving roller rotates in the positive and negative directions to make the plate move back and forth. Adjust the pressure roller and gradually press down, the plate can be bent into the required curvature cylindrical surface, conical surface, small curvature of the hyperboloid. One end of the pressing roller is raised to facilitate removal of the workpiece. In addition, there are 4 rollers and multiple rollers. 4 rollers are used to roll thick plate cylinders, and multiple rollers above 4 rollers gradually bend the plate into a complex profile through multiple pairs of rollers.

Yuanhao stretch bending requires high precision, large length and radius of curvature, and small lateral size, and can use a special retractor for bending. When bending, because the tensile stress acts on the entire thickness of the plate, only tensile deformation occurs, and the deformation caused by the rebound after unloading is small, which is easy to ensure the accuracy.

2. The process parameters of Yuanhao bending.

The selection of appropriate processing parameters is the key to the Yuanhao bend forming process. In addition to the mold and other factors, the process parameters that affect the quality of bending forming include the tensile force and deformation in the bending process. The main factors limiting bending processing in production are bending fracture and excessive deformation of cross-sectional dimensions. To determine the drawing processing parameters, these two aspects must be considered first. In addition, minimizing the amount of elastic recovery is also one of the important bases for selecting bending parameters. In the edge bending process, selecting the wrong processing parameters is also an important factor to consider the instability and wrinkling of the web. Extruded profiles are considered to be a special kind of sheet metal material. The one-way size of the material itself is much smaller than other two-way sizes. In the forming process, it can usually be regarded as completed under plane stress. However, the bending of the profile is different from the forming of the sheet, which is usually considered to be isotropic, and the anisotropic characteristics of the extruded profile are more obvious. The tensile member is subjected to the axial tensile force and the bending moment, and the components are the bending members, including the eccentric tensile member and the pull rod member to which the transverse load acts. The application of flexural members in steel structures is less than that of flexural members, and the bending moment is not large. It is mainly under the action of axial tension, and its cross-sectional form is the same as that of ordinary axial tie rods. Under the joint action of bending tension and bending moment, the plastic hinge in the cross-section is considered to be the limit of bearing capacity. However, in lattice components and cold-formed thin-walled steel components, the strength limit is almost reached when the plastic at the edge of the cross-section. In general, Ji'nan bending parts lose the overall stability and the possibility of local stability is low.