SU766705A1 - Bending die - Google Patents

Description

(54) FLEXIBLE STAMP

I

This invention relates to the field of cold sheet forming of low-plastic materials.

Stamps are known in which the formation of small bending radii is achieved with help and stops for compressing the flanges from the ends.

The compression of the shelves from the ends is carried out either by a forming cavity composed of working surfaces of the punch and die, or with the help of separately made stops with individual drives, or a pressure plate. The action of the stops on the shelves of the workpiece leads to a decrease in stresses (and deformations) of tension in the external fibers along the bend line, where the material usually fails during bending to a small radius.

Bending dies are also known for bending workpieces of small radius, containing a punch and a matrix interacting with it. The matrix is made of side elements having translational and rotational mutual displacements, and an emphasis located in the central part of the matrix. The stop is provided with a buffer.

The disadvantage of these stamps is that the deformation is localized on

bending lines, where tensile stresses act due to the absence of devices for pressing shelves, which prevents the bending of low-plastic materials for a small radius, as well as in the complexity of the matrix design (movable spring-loaded side elements, moving sliders, etc. ).

The aim of the invention is to simplify the design of the stamp and ensure the possibility of obtaining minimum radii of 10 are flexible in parts of low-plastic materials.

To this end, the side elements of the matrix are fixed, and the punch is made protrusions that interact with the ends of the shelves of the workpiece.

In addition, in order to provide the possibility of flexible materials with coatings, the working end of the abutment is made of an elastic material.

The device is a bending 20 punch of the second (final) transition to obtain parts of the profile type with flat shelves and a bending radius g less than allowed from the workpiece, previously uniformly bent to the radius R allowed by the ductility of the material. Preliminary bending is rationally carried out with a rigid punch in an elastic matrix.

The possibility of obtaining minimum radii of bending in parts of low-plastic materials is achieved by simultaneously pressing the shelves at the ends and clamping the workpiece along the bend line between the punch and the stop, which leads to the limitation of the deformation of the stretch in the danger zone.

FIG. 1 shows a schematic diagram; in fig. 2 shows the working end face of the stop.

The stamp consists of a punch 1 with protrusions 2 and a die. The matrix is made from placed in its Central part of the stop 3 and side elements 4, fixed stationary. The stop 3 is provided with a buffer 5, and the working end 6 of the stop is made of an elastic material. The protrusions 2 on the punch are made at a right angle to the working planes of the punch and at such a distance from the axis that when the punch and the die of the shelf 7 approach each other, the workpiece 7 rests against them. The height of the shoulders is (1.5-2.0) S, where 8 is the thickness of the material. They can be made either as part of a punch or removable.

The matrix has on the upper end face facing the punch, the counter projections 8 for centering and for fixing the shelves of the workpiece, but may not have them. The presence of protrusions allows for undercutting at the end of the working stroke.

A groove 9 formed by the side elements 4 of the die serves as a guide for the stop 3. The height of the working part of the stop is 1.5-1.2 times the distance between the punch and the die in the initial state. The height of the lower part of the abutment is selected from structural considerations.

Buffer 5 is placed in the groove 9 of the matrix with a certain gap, allowing deformation of the buffer.

The size of the gap, {the size of the buffer and its material are chosen so as to ensure the closure of the punch and the die, i.e., to make a working stroke, if there is a certain back pressure on the workpiece from the abutment side. The magnitude of the required backpressure depends on the mechanical properties of the material being molded and the size of the part and is chosen experimentally, and the back pressure should be the higher, the greater the strength of the material, the thickness of the workpiece and the curvature of the part.

The stop has in the upper part facing the workpiece 7, a longitudinal groove in which is placed from an elastic material directly in contact with the workpiece 7. The side surfaces of the groove 10 have a bevel of 10-15 ° and blunt edges. The width of the working part of the anvil and the corresponding size of the elastic insert 6 is chosen depending on the bending radius H and the thickness of the workpiece S: & (3-5) S f (2-3) S at the optimal height of the elastic insert

is 3-5 mm.

The stamp works as follows. In the initial position (Fig. 1, the position of the workpiece 7 of radius R is placed between the punch and the die so that the zone of probable destruction — the bending line — is located between the punch 1 and the stop 3. When the working pressure on the punch P increases also increases due to the compression of buffer 5, therefore, the material in the most hazardous zone (bending line) is practically not deformed.In addition, the presence of back pressure facilitates disassembly after bending.

As the punch and die approach (Fig. 1, position b) in the workpiece areas,

coming into contact with the tool, the deformation is limited, which contributes to its most uniform distribution over the section of the workpiece. The deformation zone is distributed from the middle of the shelves to the center and the ends of the workpiece.

The presence of protrusions on the punch leads to the fact that the deformation of the expansion of the bent shelves occurs under conditions of two-way pressure: from the ends resting against the shoulders, and in the center of the workpiece,

O pressed against the punch, ensuring the predominance of stresses and compressive deformations.

At the last stage of deformation, undercuts of the part take place in a closed volume, which allows to increase its accuracy.

 Thus, the preform is formed over a small radius fe by deforming the material not locally but over the entire length of the shelves under conditions of predominantly compressive stresses. By

For this, a reduction in the radius of bending is achieved by 1.5–2 times as compared with the value of R, which is possible with bending in known devices.

If necessary, obtaining parts with unequal shelves can be respectively

5 asymmetrically position the tabs on the punch. This will lead to additional material savings, since the commonly used bending dies for free bending are intended to produce only symJ metric parts that require a subsequent one-sided trimming allowance.

Claims (2)

1. A bending punch containing a punch and a matrix interacting with it, made of an abutment located in its central part, provided with a buffer, and side elements, characterized in that, in order to simplify the design and enable the minimum radii of bending to be obtained, in parts of low-plasticity materials, the side elements of the matrix are fixed, and the punch is made protrusions that interact with the ends of the shelves of the workpiece. 2. A bending device according to claim 1, characterized in that, in order to allow the materials with coatings to be flexible, the working end face of the support is made of an elastic material. Sources of information taken into account in the examination 1. USSR author's certificate No. 513765, cl. B 21 D 11/00, 03/19/75 (prototype). 2. The patent of Germany No. 1927520, cl. 7 sec., 5/04, 1969.