RU2086329C1 - Method of forming by elastic medium - Google Patents

Abstract

FIELD: plastic metal working, cold forming, namely, manufacture of parts from thin sheet blanks. SUBSTANCE: method comprises steps of bending blanks along rigid punch at several transitions by elastic medium; in first transition using cover plate placed between blank and said rigid punch and having rounded bosses on its ends; simultaneously with initial bending forming wave of excess material in bending zones and(or) in zones of possible stability loss of part. EFFECT: enhanced efficiency. 2 dwg

Description

 The invention relates to the field of metal forming, and more particularly to cold stamping, and can be used for the manufacture of parts from thin-walled blanks.

 Known are the methods of manufacturing parts by flexible molding, in which the workpiece is squeezed with an elastic medium onto a rigid punch (EI Isachenkov, Stamping with rubber and liquid. M. Mechanical Engineering, 1967, p. 36 39, 212 - 215).

 Closest to the proposed technical solution is the method presented in the patent of Russia 1829978, cl. B 21 D 22/10, 07/23/93, BI N 27.

 In this method, in the process of forming the part, the preform is preformed by special techniques and give it a surface equal to the surface of the final part. Then, the final stamping of the workpiece is performed, transforming the compression stresses into tensile stresses. These stresses cause the workpiece to move throughout the available volume. In this case, the radius of the mating of the walls and sides of the workpiece is usually taken close to three thicknesses of the material, since when bending to a smaller radius with a predominance of tensile stresses, significant thinning occurs and even cracks appear.

 After the load is removed, the side springing is observed, which leads to manual finishing work to obtain the desired accuracy.

Known technical solution has the following disadvantages:
a large amount of manual finishing work as a result of springing,
low accuracy and surface quality,
strength reduction due to thinning of the material in the bending zone,
the low stiffness of the bead is a consequence of the large radius of mating of the wall and the bead of the part, as well as the thinning of the material in the bending zone.

 the possibility of cracking and thinning of the material in the bending zone significantly reduce the reliability and resource of use of the part.

 The claimed technical solution is aimed at improving the quality of manufacturing parts from thin-walled materials, namely, to obtain parts with a mating radius of the wall and side close to zero and thickening in the bending zone, as well as in the zone of possible loss of stability of the part.

 This is achieved by the fact that in the method of stamping with an elastic medium onto a rigid punch, according to the invention, before the final stamping on the workpiece, a wave of excess material is created in the bending zones or in the zones of possible loss of stability.

 In FIG. Figure 1 shows the scheme for producing an intermediate workpiece: to the left of the axis of symmetry, the initial position of the workpiece before stamping, to the right is the preparation of an intermediate workpiece; in FIG. 2 a similar scheme for obtaining the finished part.

The proposed method can be implemented, for example, in a device consisting of a rigid punch 1 mounted on a sub-die plate 2, an elastic matrix 3 placed in a container 4, and an installation composite pin 5. For the formation of a wave of excess material in the bend between the workpiece 6 and the rigid the punch 1 is a removable pad 7, on which bulbs are made in places of bending or possible loss of stability of the part. The radius of the bulb is taken close to the minimum possible for this material. The length of the curvilinear part of the bulb and the location of the center of curvature with respect to the place of subsequent material upsetting is determined by a variety of parameters and mainly empirically. The most important of these options are:
the condition of abutment of the sides of the intermediate billet 6 in the sub-die plate 2 in the absence of a removable lining 7,
total spring must unfold the sides of the intermediate workpiece inward,
inner bending radius, bending angle and thickening in bending zones or in areas of possible loss of stability in the final part.

 Given these parameters, the area of the workpiece 6 exceeds the working area of the rigid punch 1 by 2-10%. The difference in these areas is formed using bulbs of a removable lining 7 into a wave of excess material above the place of its subsequent upsetting.

The method is as follows. At the first transition (Fig. 1), a removable cover 7 is mounted on the rigid punch 1, on which the sheet blank 6 is in turn placed and fixed in this position by the mounting composite pin 5. A press force is applied to the container 4 and stamping is performed. Before the second transition, the removable pad 7 and the lower part of the mounting composite pin 5 are removed. The stamped intermediate preform 6 is placed on a rigid punch 1 and fixed in this position by the upper part of the mounting composite pin 5 (Fig. 2). A press force is applied to the container 4, approximately 1.5 times more than during the first transition, and the final stamping is performed. In this case, all the gaps between the workpiece 6 and the rigid punch 1 are selected by material upsetting on the working surface of the rigid punch 1. As a result, the bending radius is close to zero and the thickening in the zone of precipitation of the wave of excess material is up to 20%
The use of an additional transition in the proposed method of stamping with an elastic medium leads to a redistribution of deformations and stresses in the bending zone, while they become compressive throughout the thickness of the material in the bending zones. As a result, springing is significantly reduced and stabilized, which eliminates the time-consuming manual manual finishing work. The method makes it possible to obtain parts with a bending radius close to zero with an increase in the thickness of the material in the bending zones, which increases their strength and rigidity, leads to an increase in the reliability and resource of use of the part. As a result, a thinner-walled material can be used to manufacture the part, which will reduce the weight of the part and the entire structure.

 An example of a specific implementation of the method.

 An experimental stamping of a sheet billet 1 mm thick was made of AMtsM material 51 mm long and 30 mm wide.

 At the same distance from the edges of the workpiece 25.5 mm, two holes were drilled for the mounting pins with a diameter of 5 mm. The center distance between the holes is 20 mm. Stamping was carried out on a punch 12 mm high and 26 mm wide with sharp rectangular edges. At the first transition, a removable pad with bulbs at the edges with a radius of about 3 mm was used. The protrusion of the bulb beyond the edges of the punch is about 2 mm. The length of the curved part of the bulb is equal to 3.5 radius of the bulb. The radius of the transition from the surface of the bulb to the surface of the lining is about 20 mm. The matrix is made of material SKU-7 L. Stamping at the first transition was carried out with a pressure of 100 kP, at the second 160 kP. After the first transition, the pad was removed in the transverse direction, since the set of springs leads to a small turn of the sides into the internal volume of the part. At the second transition, the board abuts against the punch plate and, when loaded, loses stability inward along the stamped radius, pressing against the punch. After precipitation of the wave of excess material and removal of the finished part, cracks or irregularities are not observed, only in the tangential direction there are small protrusions in the places of bending.

Claims (1)

 The method of stamping with an elastic medium, according to which bending is carried out on a rigid punch in several transitions when creating a wave of excess material in the bending zones and / or in the places of possible loss of stability of the part, using a patch at the first transition, which is placed between the workpiece and a rigid punch, characterized the fact that the patch is performed with rounded bosses at its ends, and a wave of excess material is formed simultaneously with the initial bend.

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