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2021/08/17

Workpiece bending, in addition to plastic deformation, accompanied by elastic deformation, the phenomenon of rebound. Therefore, the corner of the bent part should not be too large. Otherwise, the bending angle stability cannot be guaranteed.

Bending angle R is too small easily lead to the outer layer of fiber pulling crack. For low carbon steel, the minimum bending angle of about 1.0T; brass and aluminum, the minimum bending angle of about 0.6T; for carbon steel, the minimum bending angle of about 1.5T.

In order to ensure the quality of the workpiece bending, bending products straight edge height h should not be too small, must be greater than or equal to the minimum bending height hmin. h ≥ hmin = r + 2t formula: r - bending angle t - bending plate thickness

When bending blanks with holes, the hole edge distance should not be too small. If the hole is too close to the bending edge, the shape of the hole will change when bending. From the hole edge to the bending side of the distance L, L should be consistent with the following formula: when t < 2, L ≥ r + t when t ≥ 2, L ≥ r + 2t formula: r - bending angle; t - the thickness of the bending piece.

To prevent deformation, the height of the bent parts should not differ too much. The shape and size of the bent parts should be as symmetrical as possible, or else at the small end will produce a distorted distortion. If such results in the design of difficult to improve, it must ensure that: h>r + 2t formula: h - the height of the small side; r - bending rounded; t - the bending piece plate thickness.

In the local bending of a section of the edge, in order to mind at the junction due to stress concentration and tearing, should not ignore the first punch unloading holes, cut grooves, or bending line displacement a certain distance.

Narrow side bending, the deformation area of the cross-sectional shape will be distorted, that is, the width of the inner surface becomes wider, the width of the outer surface becomes narrower. When the plate width b < 3t (t for the plate thickness), especially obvious.

If the width of the bent parts b high precision requirements, do not allow bulging phenomenon, should not ignore the bending line in advance to make the

Bending plastic deformation and elastic deformation at the same time. When the external load is removed, the elastic deformation disappears, resulting in rebound. Rebound value and material properties, the relative bending radius r / t, bending angle and other factors.

The higher the yield point σs of the material, the smaller the modulus of elasticity E, the smaller the r/t, the larger the bending angle, the greater the rebound. In order to ensure the accuracy of the workpiece, bending can not ignore the rebound.

Available to repair the mold, the use of different parts of the rebound direction, the local increase in the triangular rib method to reduce rebound, can also be used to reduce the swing block concave mold structure rebound.

For the bending radius of the parts, can not use the ordinary bending method. Otherwise, due to its large elastic deformation can not obtain the required shape and size, at this time the available pull bending method.

Before the bending of the sheet plus an axial tension, the data so that the stress within the blank section is slightly greater than the yield point of the material, and then bend in tension at the same time.

For the complex shape of the bending parts, can not be bent into a bending, and the need for multiple bending and forming. The principle of work order arrangement is to bend the outer corner. After the second bending can not affect the previous bending part of the deformation. The number of bending can be twice, three times, or even more.

Edge part of the notched bending parts, if the gap in the blank will be punched out, bending will appear forked, and in serious cases can not be formed. This is necessary to leave a connection at the gap, to be bent into shape and then the connection will be removed.

In the

Holes in the part should be used for positioning as much as possible. If the parts are not available holes, then consider the process hole positioning.

Bending die should be noted in the process of mold bending only in the part to determine the location of the bending line. The blank should not produce large local thinning and scratching.

Bending using the structure of the left, the position of the bending line at the outer corner C in the bending process is changing, first at point B, and finally to point C, so that the shape of the outer corner of the part is not allowed, the straight arm part thinning.

Bending mold structure should take into account the blank in the bending of the rotation space, can not prevent and prevent the blank to move and rotate, otherwise it will affect the shape and size of the workpiece. This is particularly important for the shape of complex multi-angle bending.

The size of the bending rebound and material modulus of elasticity is proportional. Small modulus of elasticity of the material after deformation of the elastic recovery, should not be used in the bending process.

The same yield point of the material, the elastic modulus of the material after deformation of the elastic recovery is small. Has been annealed low carbon steel than soft manganese brass suitable for bending workpiece material.

The size of the bending rebound is proportional to the yield limit of the material. High yield point of the material, the elastic recovery after deformation, should not be used in the bending process. That is, the same modulus of elasticity of the material, the yield point of high material, elastic recovery is larger. Therefore, cold hardening steel should not be used for bending process.

Bending radius and curvature angle are very large bending pieces should be rolled (rolled plate), and can not use the ordinary bending method. Roll bending is placed on the slab in 2 to 4 rolls through, with the roll rotation, so that the slab bent into shape. In addition, due to the position of the rollers can be properly changed relative to the slab, so it can also be made into quadrilateral, oval, and other non-circular section of the barrel-shaped pieces.

Long strip material around the longitudinal axis of the bending should be used to roll forming and should not use the ordinary bending method. Roll forming is placed in front of and behind the straight row of several groups of forming rollers through.

As the rollers rotate, the strip material is fed forward at the same time, and then bend the axial forming. Roll forming is capable of producing parts with complex cross-sectional shapes. The manufacture of the roll is simpler, lower cost, and longer life.

Variable cross-section slotted parts in small and medium-sized production, in order to reduce investment, roll forming can be used. At this time, the forming roller in addition to the longitudinal relative movement of the slab, but also the transverse imitation movement.

Although the nature of the deformation, pipe and profile bending and sheet bending is the same, but the process and the difficulty of a large difference. Bending of pipes and profiles must be prevented from bending deformation within the blank section shape distortion.

In production, the pipe and profile bending methods such as pull bending, rolling, push bending and bending around. It should be noted that the convex die of pulling bending, rolling bending rolls, pushing bending and bending around the fixed die, the working surface should be made to match the shape of the blank section groove to prevent the rotation of the section and shape distortion. If necessary, the tube should also be added to the corresponding mandrel.