RU102543U1 - DEVICE FOR FORMING THIN-WALL AXISYMMETRIC CONVEX DETAILS - Google Patents

Abstract

The utility model relates to cold sheet stamping, in particular to the shaping of thin-walled axisymmetric shells, and can be used in the manufacture of large-sized thin-walled parts of convex shape on double-acting presses. The essence of the utility model lies in the fact that the device for forming thin-walled axisymmetric shells containing an ejector, a die, a punch, a clamp is equipped with a stamp plate on which the container is mounted, an elastic element is located on it inside the backing plate; an elastic buffer is located between the stamp plate and the backing plate; characterized in that the displacement of the punch is less than the displacement of the backing plate. The utility model allows to improve the quality of the workpieces and to obtain parts with a uniform distribution of thickness along the generatrix. 1. s.p. f-ly, 1 ill.

Description

The utility model relates to cold sheet stamping, in particular to the shaping of thin-walled axisymmetric shells, and can be used in the manufacture of large-sized thin-walled parts of convex shape on double-acting presses.

A known method of producing thin-walled axisymmetric products from a welded sheet stock, based on the processes of flanging and molding (A. S. 1748905 USSR, MKI 5 V21D 22/30; publ. 23.07.92, bull. No. 27). With it, it becomes possible to obtain a uniform thickness of the product and reduce the thickness of the initial billet by 45-50% by reducing the allowance for machining in thickness for high convex-shaped parts. A distinctive feature of the method is the presence of active friction forces arising on the contact surface of the punch and the workpiece, which redistribute the stress σ _ρ (in the meridional direction).

A disadvantage of the known device is the low quality of the workpieces.

The closest in technical essence to the claimed one, which is taken as a prototype, is a device for shaping thin-walled truncated tapering shells, consisting of an ejector, container, matrix, stamp plate, underlay plate, clip, punch, elastic buffer, elastic element (Pat. 78709 of the Russian Federation , IPC ⁷ B21D 20/30; publ. 10.12.2008, Bull. No. 34).

A disadvantage of the known device is that the low degree of shaping and the quality of the workpieces.

The utility model is based on the task of improving the quality of workpieces and obtaining parts with uniform thickness.

The solution of this problem is achieved by the fact that the device for shaping thin-walled axisymmetric parts of a convex shape containing an ejector, a die, a punch, a clamp, a stamp plate on which the container is mounted, an elastic element is located on it on the underlay plate, an elastic buffer is located between the stamp plate and the underlay plate , according to the utility model, the inner diameter of the container is determined from the ratio:

where V ₁ is the volume of the displaced part of the elastic element during the shaping of the convex part;

Δh _b - the amount of compression of the elastic buffer;

d is the diameter of the smaller base of the part.

The drawing shows a stamp for forming convex thin-walled axisymmetric shells (to the left of the axis in the open, and to the right of the axis in the closed position).

A device comprising a pusher 1, a container 2, a die 3, a clamp 4, a punch 5, a stamp plate 6 on which the container 2 is mounted, an elastic element 7 is located on it inside the backing plate. The elastic element is pressurized using the backing plate, the back pressure of which determined using a buffer device 8 (either a press or a stamp, which is determined by the need for industrial production or experiment). The device operates as follows:

The workpiece 9, in the form of a truncated cone, is installed by the outer surfaces adjacent to the end face of the larger base, onto the die 3, and adjacent to the end of the smaller base, onto the ejector 1. Then the workpiece is clamped along the inner surfaces to the die 3 by pressing 4, and by the punch 5 to the ejector 1 The tool where the workpiece is clamped is made with work surfaces having a taper matching the taper of the workpiece. This geometry allows you to securely fix the workpiece until plastic deformation. The punch moves down, displacing part of the volume of the elastic element V ₁ , which moves the backing plate 10 down. Plastic deformation of the workpiece occurs under conditions of plane tension and significant active friction forces, between the punch - the workpiece and the elastic element - the workpiece. The process of plastic shaping is carried out until the workpiece is completely adhered over the entire surface of the punch, forming the dimensions of the finished part, and is limited by the amount of thinning of the workpiece in the danger zone of the smallest diameter. Active friction forces act on the contact surface of the elastic element and the workpiece, since the movement of the workpiece lags behind the backing plate.

The magnitude of the created pressure is determined by the elastic buffer 8, located under the backing plate 10. The calculation is based on the equality of the efforts of the elastic element and the elastic buffer acting on the backing plate (from different sides). The amount of movement of the backing plate is equal to the amount of compression of the elastic buffer 8. Knowing the required pressure, find the force acting on the backing plate, taking into account that the pressure created by the elastic element in a closed volume is distributed equally in all directions. From the condition of equality of efforts, both from the side of the elastic element and from the side of the elastic buffer we have:

where q, q _b - respectively, the pressure created by the elastic element and the elastic buffer;

D _b = (0.75-0.8) D _contact - the outer diameter of the elastic buffer;

D _b = d / (0.75-0.8) - the inner diameter of the elastic buffer.

The accepted ratio of the diameters are taken from the compression conditions of the elastic buffer to 25%. This eliminates the rapid wear of the elastic buffer and prevents destruction of the container at high pressures, in the event of an error in adjusting the stroke of the punch. From the expression (1) we find:

where D _cont - the inner diameter of the container, which is found from the condition:

where V is _e-elem. - the volume of the elastic element.

where V _con - internal volume bounded by a conical billet;

V _cyl - the volume formed by the cylindrical part of the ejector during shaping;

V _el. - the volume of the elastic cylinder;

h _el. - the height of the elastic cylinder.

Determine the diameter of the container, taking into account the record (3):

The volume of the displaced part of the elastic element during the shaping of the convex part is calculated:

where V _det - volume, details excluding allowances for clamps, equal

Where:

According constructed or known nomogram, with the found value q _b set the relationship between the deformation of the elastic buffer and the geometric ratio for the applied elastic buffer material:

where h _b - the height of the elastic buffer;

M is the accepted value.

The compression strain of an elastic buffer is calculated by the formula:

where Δh _b - the amount of compression of the elastic buffer.

The last ratios allow you to determine the height of the elastic buffer:

Equating the last two equalities, we obtain:

To find Δh _b , you need to keep in mind: the amount of compression of the elastic buffer depends on the magnitude of the displaced volume during the formation of a part of a given size. Since the elastic element is in a closed volume, the internal pressure in it depends on the possible movement of the backing plate 10, which creates a resistance force when compressing the elastic buffer 8. In this case, the punch, penetrating into the elastic element 7, moves part of the volume V ₁ (displaced volume ) into the volume V ₂ . Since the elastic element is practically incompressible, we can take V ₁ = V ₂ . The volume V ₁ , the cross section of which has a figure close to the triangle Δabc, is limited on the one hand by the outer surface of the part, and on the other, by the inner surface of the elastic element, which coincides with the outer surface of the workpiece. The volume V ₂ has in cross section the shape of the rectangle a'b'c'd 'and is equal to:

From the equality condition V ₁ = V ₂ we find:

Then, according to the nomogram, the intersection point of three lines is selected: a horizontal line corresponding to the pressure of the elastic buffer; a vertical line corresponding to the selected value of the buffer compression strain; the dependence curve q _b = f (ε) with the geometric relationship M. Moreover, the values of M and ε must satisfy the dependence (13). By the formulas (11, 12), the height of the elastic buffer was determined.

To implement the shaping process by the proposed method, a necessary condition is the creation of active friction forces at the boundary of the elastic element - the workpiece, which is performed if the displacement of the elastic buffer Δh _{b is} greater than the displacement of the punch Δh:

From expression (15) we find the value of the diameter of the container that satisfies the condition:

Using the device of the proposed design allows forming thin-walled axisymmetric parts of a convex shape with large deviations of the diameters of the large base to a smaller one and, by adjusting the pressure of the workpiece on the punch using an elastic element, to obtain a uniform distribution of thickness along the generatrix.

Claims (1)

A device for shaping thin-walled axisymmetric parts of a convex shape, containing a pusher, a die, a punch, a clamp, is equipped with a stamp plate on which the container is mounted, and an elastic element is located on the bed plate inside the container, and an elastic buffer is located between the stamp plate and the bed plate, characterized in that the inner diameter of the container D _cont determined from the ratio:

where V ₁ is the volume of the displaced part of the elastic element during the shaping of the convex part; Δh _b - the amount of compression of the elastic buffer; d is the diameter of the smaller base of the part.