Analysis of the bending process in the processing of metal stamping parts!

2021-03-23 18:39:36 admin

Analysis of the bending process in the processing of metal stamping parts!


     Analysis of the bending process in the processing of metal stamping parts! Metal stamping processing, also known as sheet punching or cold stamping, is one of the most advanced methods in pressure processing. Stamping processing generally uses sheet metal as the raw material (metal pipe and non-metallic materials are also used); the punching die installed on the press is used for reciprocating motion, and pressure is applied with the sheet metal at room temperature to cause separation or deformation. In order to obtain parts of a certain shape, size and performance. There are also many types of metal parts stamping processing, such as: punching, bending, stretching and other processing methods. So today we will talk about the analysis of the bending process.

Analysis of the bending process in the processing of metal stamping parts!


First, analysis of bending process




Bending is a stamping process that uses materials to produce plastic deformation and form a certain angle shape. Bending can be performed on a Euroton press with a mold, or can be completed on a dedicated bending machine or bending equipment.




According to different processing materials, bending can be divided into sheet metal bending, tube bending, profile bending, bar bending, etc.; according to the different equipment used for bending, it can be divided into bending, rolling, stretching, roll bending, etc. .




The accuracy of bending parts processing is related to many factors, such as the mechanical properties and material thickness of the bending part materials, mold structure and mold accuracy, the number of processes and the sequence of processes, and the shape and size of the bending parts themselves. Bending parts with high precision requirements must strictly control the material thickness tolerance. Generally, the economic tolerance level of bending parts is best to be below IT13 level, and it can reach IT11 level by adding shaping and other processes.



(1) Bending process


The process of bending is to use a V-shaped bending die to bend the mold structure of the V-shaped part. The convex mold 1 and the concave mold 2 are basically consistent with the inner and outer contours of the bending workpiece. When the external force (if the slider of the force machine moves) pushes the convex mold down, the sheet metal placed between the convex and the concave mold is bent into Required artifacts.




Bending can be divided into free bending and correcting bending. The difference is that free bending means that when the punch, sheet metal, and concave die are completely attached, the pressure is no longer pressed; while correcting bending is to apply on the basis of free bending. Pressing down makes the workpiece produce one-step plastic deformation to reduce the springback of the bent part.


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Second, bending deformation analysis


 The characteristics of bending deformation can be obtained by setting a square grid on the side of the sheet before bending and observing the changes of the grid before and after bending.



After observing the bending, it can be found through the coordinate grid:


(1) The square coordinate grid of the rounded part changes from a square to a fan shape, and the other parts are not deformed or deformed very little.




(2) In the deformation zone, the side grid changes from a square to a fan shape; the outer side close to the concave mold is stretched by hand tangentially, and the length is elongated; the inner side close to the convex mold is tangentially compressed and the length is shortened. From the inner and outer surfaces to the center of the sheet, the degree of shortening and elongation gradually decreases. The layer of metal whose length does not change before and after deformation between shortening and elongation becomes the neutral layer.






When a type of change in the cross section of the bending deformation zone occurs during stamping, we need to observe the change of the cross section after bending, we can find:




(1) The cross section of the sheet material in the deformation zone is deformed. After the inner layer of the curved narrow plate is tangentially compressed, it flows in the width direction to increase the width; after the outer layer is tangentially stretched, the material deficiency is supplemented by the width and thickness directions, resulting in a narrower width (the entire The section is a sector with a wide inside and a narrow outside). For a wide board with a large width, due to the large amount of material in the width direction, the resistance is large, and the material is difficult to flow in the width direction, and the cross-sectional shape remains basically unchanged, and it is still rectangular.



(2) The thickness is reduced. When the sheet is bent, the inner layer is shortened by the tangential compression surface, and the thickness should be increased. However, because the punch presses the sheet tightly, the thickness increase resistance is great, and the outer layer is stretched by tangential stretching, and the thickness direction becomes thinner. Bound. The increase in thickness is less than the decrease in the entire thickness, so that the phenomenon of thickness reduction occurs.




 The general bending parts belong to the wide plate bending, so the width direction of the plate is basically unchanged before and after bending. If the bending radius of the bending part is r and the thickness of the bent sheet material is t, the bending part with a smaller bending radius r/t will obviously become thinner in the deformation zone during bending. According to the principle of constant volume, It will inevitably increase the length of the sheet.