RU2060092C1 - Blank for forming parts of п-shaped cross section with use of electric contact heating - Google Patents

Abstract

FIELD: metal pressure forming, namely forming of curvilinear parts from sheet blanks with use of electric contact heating. SUBSTANCE: flat sheet blank for forming parts, having п-shaped cross section, with use of electric contact heating has cross slits near its edges along a descending line of the part from a punch, having a predetermined length, taking into account a height of a bead, a joining radius of the bead and a wall along a neutral layer, an angle between the bead and the wall. EFFECT: enhanced efficiency. 1 cl, 6 dwg

Description

 The invention relates to the processing of metals by pressure, in particular to the stamping of curved parts from sheet blanks with electric contact heating, and can be used in aircraft construction and other engineering industries.

Known flat sheet blank used in the manufacture of parts using the device to the press for electrical contact heating, containing clamping mechanisms with jaws connected to the conductors, and the tension mechanism [1]
The disadvantage of such a workpiece is that in the manufacture of U-shaped parts, the sections of the part adjacent to the escape line from the punch are warped, since the clamps are flat and the part has a simple shape, which leads to stresses that tend to straighten the deformable workpiece. In the case of the execution of the jaws of the clamping device in the shape of the section of the part, their design is greatly complicated; in addition, for each type of section, it is necessary to produce a new set of clamping jaws.

Closest to the technical nature of the invention is a workpiece for stamping parts of a U-shaped cross-section with electrical contact heating, made from a sheet taking into account technological allowances [2]
The disadvantage of this workpiece is the low quality of the obtained parts of the U-shaped section due to warpage.

 The technical result achieved by the invention is to exclude warpage of U-shaped parts obtained from the workpiece.

This is achieved by the fact that on a flat sheet blank for stamping parts of a U-shaped cross-section with electrical contact heating, made from a sheet taking into account technological allowances, transverse cuts are made along the edges along the line of run of the part from the punch, which eliminates the occurrence of stresses that straighten the deformable workpiece when using flat clamping jaws. The lengths of the cuts l _i is determined by the formula:
l _i h _i + α _i R _i, where h is the height of the corresponding side;
R _{i is the} radius of the interface between the side and the wall along the neutral layer;
α _{i is the} angle between the side and the wall.

 In FIG. 1 shows a detail, a general view; in FIG. 2 the same plan; in FIG. 3 device for bending U-shaped parts; in FIG. 4, section AA in FIG. 3; in FIG. 5 finished part, general view; in FIG. 6 is a view along arrow B in FIG. 5.

As a blank for the manufacture of a U-shaped part, the cross section of which is shown in FIG. 1, a flat sheet blank was used, the dimensions of which are determined by the length of the part sweep taking into account technological allowances (Fig. 2). On the edges of the workpiece along the line of run of the part from the punch, transverse cuts of the required length l _{i are made} . During deformation with an axial tensile force P _{p of} such a workpiece in a stamp (Fig. 3, 4) with electric contact heating through flat clamping jaws 1 when the die 2 and the punch 3 are closed under the action of the press force P on which the stamp is mounted, the forming of part 4 According to the forming surfaces of the matrix and punch. The technological allowance remains flat and does not affect the shape of the part, since it is defined by the deformable part of the workpiece by cuts, and the rest of the workpiece retains its flatness. After deformation, a part is obtained (Figs. 5 and 6). Along with the exclusion of warping, the operation of trimming the stock is also simplified, since it remains flat.

The proposed blank was tested in the manufacture of U-shaped parts from VT-20 with electric contact heating in a stamp (Fig. 3 and 4) on a HVC-250 press. The thickness of the blanks is 2 mm, the side height varied from 40 to 60 mm, the radius of the interface between the side and the wall is 5 mm, the angle between the side and the wall is 90 ^° . Flat clamping jaws were used, through which electric current from the transformer was supplied to the workpiece. The axial tensile force was carried out using hydraulic cylinders. As a result, parts without warping were obtained, the shape of which corresponded to the shape of the matrix and punch.

 The proposed blank will improve the quality of the parts by eliminating warping.

Claims (1)

A blank for stamping parts of a U-shaped cross-section with electric contact heating, made of a sheet taking into account technological allowances, characterized in that the workpiece is made of transverse cuts along the edges along the line of run of the part from the punch length
l _i = h _i + α _i R _i ,
where h _{i the} height of the corresponding side;
R _{i is the} radius of the interface between the side and the wall along the neutral layer;
α _{i is the} angle between the side and the wall.

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