RU2071863C1 - Method of manufacturing heads of wrenches - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: method comprises cutting out a cylindrical blank and extruding it in positions. At the fist two positions the edges at the end face of a blank is rounded. When the blank is transported from the first to the second position it rotates by 180°. To the next position the blank is fed parallel. At this position a space is extruded on one of the end faces of the blank by means of a hexahedral or dodecahedral punch. Rotating the blank by 180° it is transported then to the other position and a space is extruded by a square punch. In so doing the bottom of the previous space bears on the supporting cylindrical punch the area of the cross-section of which exceeds the area of the cross-section of the extruding square punch by no less than 25%. EFFECT: improved method. 2 cl, 2 dwg

Description

 The invention relates to the processing of metals by pressure, and in particular to methods of manufacturing hollow products by cold extrusion, and can be used in the manufacture of socket wrenches from high-strength steels.

 The closest set of essential features is the method of obtaining the heads of the socket wrenches, consisting in a segment of a cylindrical workpiece and its subsequent shaping at positions (1).

This method has the following disadvantages:
1. At the 4th position, three forming processes are concentrated, as a result of which, due to strain hardening of the metal, the tool at this position is overloaded, and the resistance of the square punch is low. Therefore, it is impossible to use blanks of high-strength alloy steels with increased intensity of hardening during deformation.

 2. The combined extrusion method at the 4th position can only be realized if the degree of deformation and, accordingly, the resistance to metal flow during direct extrusion of a cavity of a square relief and reduction of the outer surface are always less than the degree of deformation and, accordingly, resistance to metal flow when the back extrusion of a cavity of circular cross section, which limits the application of this method for the manufacture of a wide range of heads with different ratios of turnkey, square and aruzhnyh surfaces.

 3. At the 4th position, due to the possible radial flow of the metal of the thin wall of the workpiece from the side of the square relief face with mandatory emphasis on the ejector sleeve, an overload occurs during subsequent ejection of the square cross section onto this sleeve and the working element, which leads to their low resistance .

 4. Extrusion of the cavity of the wasps on the side of the hexagonal relief occurs by several punches, which also complicates the method and increases the metal consumption of the tooling.

 5. This method does not provide for the formation of roundings and chamfers at the ends of the workpiece, which can lead to sharp edges, burrs on finished products, crack formation during stamping due to remaining cutting defects, which are stress concentrators.

 The invention is aimed at solving the problem of manufacturing cold stamping in an economical way on machine heads of socket wrenches with sections of hexagonal or twelve-sided and square internal relief of high-strength alloy steel without subsequent mechanical refinement.

 The technical result of the invention is expressed in increasing the durability of the forming tool, reducing the complexity and intensity of manufacturing, improving the quality of finished products.

The specified technical result is achieved by the fact that in the method of obtaining the heads of the socket wrenches, consisting in a segment of a cylindrical workpiece and its subsequent shaping in positions, the first two positions are rounded at the ends of the workpiece, and its transfer from the first to the second position is carried out with a rotation of 180 ^o . The next position of the workpiece is transferred in parallel and the cavity is extruded on one end of the workpiece to the final dimensions with a punch of a hexagonal or twelve-sided section. Then the workpiece is transferred with a rotation of 180 ^o to another position and the cavity is squeezed out with a square punch, the bottom of the workpiece is supported by the bottom of the previously obtained cavity on a supporting cylindrical punch with a cross-sectional area that is not less than 25% the square size of the extruding punch. The radius R of the rounding at the first position is selected based on the ratio:
RD d
where D is the diameter of the workpiece obtained in the first position;
d is the largest diameter of the conical recess formed for subsequent chamfering to extrude the cavity with a punch of a hexagonal or twelve-sided section. In this case, d is 0.83 0.89 of diameter D _{1 of the} described circumference of the cross section of this punch.

 Due to the design of rounded edges at the ends of the workpiece, the cutting defects move from the periphery to the center of the workpiece, excluding cracking at subsequent positions and sharp edges on the finished products.

 Since defects that can form on the end face of the workpiece when forming a chamfer to extrude a hexagonal or twelve-sided relief are especially reduced in quality, special calculations and experimental work were carried out to determine the radius of curvature, as a result of comparison, a relationship was established for its selection.

At d <0.83 D _1, due to the uneven distribution of the load in the cavity of the matrix at the first forming position, its resistance decreases, and due to the re-mounting of the metal, the resistance of punches in the subsequent positions decreases. At d> 0.89 D _1, cut defects may remain at the ends.

 The use of only one punch, and namely a punch of a hexagonal or 12-sided section for extruding the entire cavity at one end of the workpiece to the final dimensions, reduces the complexity and metal consumption of the manufacture of the head.

 When squeezing a square relief, the dimensions of the previously obtained cavity are preserved without distortion. This is achieved by a directed metal flow, which is guaranteed by a certain ratio of the sizes of the cross-sectional areas of the extruding and supporting punches, determined by a series of experiments. If this ratio is not maintained, then the support punch will be introduced into the workpiece material, which will not allow to obtain the required cavity depth of the square relief and maintain the dimensions of the cavity of the multifaceted relief, and then lead to tool breakage.

 To simplify the configuration of tooling, the supporting punch is cylindrical.

 In order to unload the tool, the formation process was divided into positions with successive obtaining of various parts of the workpiece volume, as a result of which the tool life is significantly increased and it is possible to use workpieces made of high-strength alloy steel.

 Figure 1 presents the technological process of cold forging of the head of the socket wrench; in Fig.2 the position of extrusion of the cavity of a square relief.

 The method is as follows.

From the rod or riot cut measured workpiece. Then produce a draft with a small conical deepening and rounding of radii of radius R at one end and a conical basting at the other end. At the next forming position, the workpiece is rotated through 180 ^° , where a chamfer for extruding a hexagonal or twelve-sided relief is formed with the upper punch and a small conical recess in the bottom. At this end, rounding is also carried out. The workpiece is transferred to another position in parallel. At one end, the cavity is squeezed out with a punch of a hexagonal or twelve-sided cross-section to the final dimensions and the outer surface is pre-formed, on the other, a chamfer is formed to extrude a cavity of square relief. A blank is fed to a new position with a rotation of 180 ^° and the bottom of the previously obtained cavity is supported on the supporting cylindrical punch 1, and the cavity of the square relief is extruded with the upper punch 2 with the marking for punching the hole, and the final height and outer diameter of the product are obtained. At the last position, where the workpiece enters with a rotation of 180 ^o and rests on the end with a cavity of square relief, a hole is punched.

 An example of a specific implementation of the method of obtaining a socket head with sections of a twelve-sided and square inner relief.

Product parameters: total height H 36 mm, outer diameter D ₂ 26 mm, turnkey size of a square S 12.5 mm, cavity depth of square relief h 13 mm, turnkey size of a dodecahedron S ₁ 17 mm, cavity depth twelve-sided relief h ₁ 12 mm,
According to the calculations, the cross-sectional area of the punch extruding the cavity of the square relief F is 156.2 mm, and the cross-sectional area of the supporting cylindrical punch F _{1 is} chosen to be 30% larger.

The diameter D _{1 of the} described circumference of the twelve-sided section of the extruding punch is equal to the largest diameter d _{1 of the} chamfer in the second position and is 20.5 mm, while the largest diameter d of the conical recess is found from the expression:
d 0.87 • D ₁ 17.84 mm
The diameter D of the workpiece after the first forming position according to preliminary data will be 25.25 mm, from which the radius of curvature of the edges is determined
RD d 7.41 mm
Complete production of the socket wrench head takes place on a 1250-5DCF multi-position cold heading machine, where a rebellion of 25 mm diameter is made of 30GIP steel according to TU 14-1-4459-88 with a tensile strength of 500 MPa.

 The proposed method of forming provides optimal conditions for the plastic deformation of the workpiece and guarantees high quality of the resulting products.

Claims (2)

1. The method of obtaining the heads of the socket wrenches, which consists in cutting a cylindrical workpiece and its subsequent shaping in positions, characterized in that at the first two positions they round off the edges at the ends of the workpiece, and transferring it from the first to the second position is carried out with a rotation of 180 ^o , and to the next position, the workpiece is transferred in parallel and the cavity is extruded on one end of the workpiece to the final size with a hex or twelve-sided punch, then the workpiece is fed with a turn of 1 80 ^o to another position and squeeze the cavity out with a square-shaped punch, with the blank being supported by the bottom of the previously obtained cavity on a supporting cylindrical punch with a cross-sectional area that is at least 25% larger than the square size of the squeezing punch. 2. The method according to p. 1, characterized in that the radius R of the rounding at the first position is selected from the ratio
RD d
where D is the diameter of the workpiece obtained in the first position;
d is the largest diameter of the conical recess formed for subsequent chamfering to extrude the cavity with a punch of a hexagonal or twelve-sided section, and amounting to 0.83 0.89 of the diameter of the circumference of the cross section of this punch.

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