RU2493928C1 - Device for forming thin-wall axially symmetric parts shaped to truncated cone - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy, particularly, to cold forging. Proposed device comprises cone with guide grooves, thrust ring, sliding sectors, female die and elastic element composed of tapered shell arranged between sliding sectors and female die. Height of elastic element equals that of female die. Note here that outer surface generating line passes through female die working surface points with maximum and minimum diameters.

EFFECT: better quality of faceting thin-wall axially symmetric tapered parts.

2 dwg

Description

The invention 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 a truncated tapering shape on double-acting presses.

A device is known for shaping axisymmetric tapering shells (AS USSR No. 755378, MKI 4 B21D 22/10, publ. 1980, Bull. No. 30), with which the workpiece in the form of a directed wave is successively deformed. The process scheme is carried out during one stroke of the press using a punch consisting of annular elastic elements (washers) with different compression characteristics, i.e. with variable compression stiffness. At the same time, elastic washers with greater rigidity should be located in the upper part of the punch, and the dimensions of the punch in the initial position should provide an upward-growing gap between the workpiece and the punch. The necessary increase in stiffness in the upper part of the punch is achieved through the use of harder grades of elastic media or by reducing the thickness of elastic washers with metal gaskets placed between them. In the process of forming a part with such a punch, at any given time, a small section of the workpiece is deformed with dimensions that do not allow loss of stability. The part of the preform lying below this section is already a molded and pressed elastic medium to the matrix, and the upper part is not yet in contact with the punch. In the molding process, it is freely pulled into the deformation zone, which reduces the thinning of the part wall and increases the limiting degree of the workpiece forming in one transition. However, the loss of stability of the free part is not ruled out for thin workpieces, since it deforms under the conditions of a stress-deformable circuit close to the drawing process, where compressive tangential stresses act.

(где S - толщина заготовки; D - средний диаметр) приводит к смятию и гофрообразованию заготовки.The disadvantage of this device is the need for significant additional shaping efforts due to the large area of the elastic medium from the side of the application of efforts for shaping. In addition, the presence of compression friction forces between the workpiece and the elastic medium for thin-walled workpieces $$\frac{S}{D}\le 0.008$$

(where S is the thickness of the workpiece; D is the average diameter) leads to crushing and corrugation of the workpiece.

The closest in technical essence are devices for shaping axisymmetric hollow parts with expandable sectors (E.A. Butuzov. Special types of stamping. Higher school. Moscow, 1963) when distributing pipes (Patent for invention 2026764, IPC B21B 41/02, published on January 20, 1995). The device comprises an expandable punch in the form of sectors installed with the possibility of radial movement around the conical core associated with a reciprocating axial movement drive, characterized in that it is equipped with an additional expandable punch mounted coaxially with the main one, and a spring placed between them, while the conical the core is made in the form of two truncated cones, motionlessly connected by their smaller bases.

A disadvantage of the devices is the faceting obtained during shaping by the distribution of an axisymmetric workpiece and the repetition of the process with rotation of the workpiece around the circumference after each transition or the presence of an additional heat-setting process. This leads to an increase in labor intensity, additional energy costs.

The objective of the invention is to obtain high-quality thin-walled axisymmetric tapering parts without cutting in one stroke of the press.

The task is achieved due to the fact that the device for forming, containing a punch, a cone with guide grooves, a support ring, sliding sectors, a matrix, according to the invention is additionally equipped with an elastic element in the form of a conical shell located between the sliding sectors and the matrix, the height of the elastic element is equal to the height matrix, while the generatrix of the outer surface passes through the points of the working surface of the matrix with the largest and smallest diameters, and the thickness of the elastic element is determined by formula is

$$S_0=\frac{S}{k},\left(\text{one}\right)$$

$$S=2\left({\rho }_{\partial }-\left(2-k\right)\sqrt{\frac{\Delta V\cos \alpha }{\pi \cdot h_m\left[{\left(2-k\right)}^2+\mathrm{one}\right]}}\right),\left(2\right)$$

where k = 0.9 ÷ 0.75 is the allowable degree of deformation in thickness;

α is the cone angle of cone;

h _m - the height of the working surface of the matrix;

ρ _∂ is the average radius of the part;

ΔV is the difference between the internal volume limited by the working surface of the matrix and the volume limited by the outer surface of the elastic element in the initial state.

The task is achieved using the device, a diagram of which is presented in figure 1, figure 2 is a section along aa.

The device consists of a punch 1 rigidly connected to the matrix 2, an elastic element 3 in the form of a conical shell, sliding sectors 4, a cone with guide grooves 5, a support ring 6, studs 7 installed in the press plate 8. Part 9, workpiece 10.

The device operates as follows.

The support ring 6 is raised up. The punch with the matrix is taken up to a height that allows the installation of the workpiece 10. The sliding sectors 4 are raised up together with the elastic element 3. In this position, the conical workpiece is mounted on top of the elastic element. Next, the punch with the die is dropped all the way to the support ring 6. In this case, the working surfaces in the elements of the largest and smallest diameters touch the elastic element. The working surface of the matrix h _m in height is greater than the height of the workpiece h ₃ , and the height of the elastic element h _E is equal to the height of the matrix h. When the punch moves down with it, the matrix 2 also drops, overcoming the resistance of the support ring 6, the sliding sectors 4 and the elastic element 3 together with the workpiece 10. The sectors, dropping down the cone 5, increase in diameter. At the same time, the elastic element also increases in diameter, which begins to deform the workpiece from inside pressure, tightly pressing it to the working surface of the matrix. The resulting part 9 is removed by first lifting the die with the die, and then the support ring 6.

A feature of such a device design is that the resulting part is faceted and its outer surface practically coincides with the working surface of the matrix, which eliminates the additional calibration operation.

The device must meet the following conditions. In order to avoid, when the diameter of the elastic element increases, its height decreases and compressive friction forces appear on the contact surface with the workpiece, which can lead to loss of stability of the thin-walled workpiece, the elastic element is clamped (at the initial moment) between the matrix and sectors in the regions of the largest and smallest diameters of the matrix. To reliably ensure the clamping conditions of the elastic element, it is necessary that its height be greater than the height of the working surface, but not exceed the total height of the matrix, otherwise the elastic element may fall into the gap between the matrix 2 and sectors 4. This eliminates the compressive friction forces on the inner surface of the workpiece. When an elastic element deforms, it increases its diameter and decreases its thickness, that is, it corresponds to the condition of a flat deformed state when the deformation in thickness ε _S is equal in magnitude and opposite in sign of deformation of the increase in the diameter of the elastic element ε _θ . It can be written approximately, assuming that the conditions for the constancy of volume for the elastic element are satisfied:

where ρ, r are respectively the radii along the middle surface and average over the center of the elastic element before and after deformation;

S ₀ , S - respectively, the average thicknesses along the source before and after deformation. Despite the decrease in the thickness of the elastic element, the increase in volume ΔV _ρ due to the increase in diameter should compensate for the difference between the internal volume limited by the working surface of the matrix and the volume limited by the outer surface of the elastic element in the initial state ΔV.

ΔV _ρ = ΔV or

where h _m is the height of the working surface of the matrix;

α is the cone angle of cone.

We express r from (3) and, substituting it into (4) after transformations, we obtain

Taking into account that ρ = ρ _∂ -0.5S, we have:

$$S=2\left({\rho }_{\partial }-\left(2-\frac{S}{S_0}\right)\sqrt{\frac{\Delta V\cos \alpha }{\pi \cdot h_m\left[{\left(2-\frac{S}{S_0}\right)}^2+\mathrm{one}\right]}}\right).\left(6\right)$$

We find the initial thickness of the elastic element by setting restrictions on the degree of deformation:

или $$\frac{S}{S_0}\le k\le 0.9÷0.75$$

or

, где $$S_0=\frac{S}{k}$$

where

$$S=2\left({\rho }_{\partial }-\left(2-k\right)\sqrt{\frac{\Delta V\cos \alpha }{\pi \cdot h_m\left[{\left(2-k\right)}^2+\mathrm{one}\right]}}\right),$$

where ρ _∂ is the average radius of the part.

Claims (1)

A device for shaping thin-walled axisymmetric parts of a truncated tapering shape, containing a punch, a cone with guide grooves, a support ring, sliding sectors, a matrix, characterized in that it is equipped with an elastic element in the form of a conical shell located between the sliding sectors and the matrix, the height of which is equal to the height matrix, and the generatrix of the outer surface passes through the points of the working surface of the matrix with the largest and smallest diameters, while the thickness of the elastic element is determined Xia formula
$$S_0=\frac{S}{k}$$

,
Where

,
where k = 0.9 ÷ 0.75 is the allowable degree of deformation in thickness;
α is the cone angle of cone;
h _m - the height of the working surface of the matrix;
ρ _∂ is the average radius of the part;
ΔV is the difference between the internal volume limited by the working surface of the matrix and the volume limited by the external surface of the elastic element in the initial state.

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