RU80371U1 - STAMP FOR PUNCHING HOLES - Google Patents

Abstract

A utility model relates to dies for punching one or a group of holes. The stamp contains an upper plate, a punch holder, a puller, a group of punches, a lower plate with a die. The group consists of punches of a round and oval contour, which are made of different lengths with a stepwise arrangement in height, and the working end of each punch of the oval contour is profiled by a body of revolution. Allows you to expand the technological capabilities of the press equipment by providing the process of simultaneous punching of multi-row holes on presses with limited capabilities. 1 C.p.F., 5 ill.

Description

The proposal relates to the field of engineering, in particular to metal forming devices and can be used in dies for punching one or a group of small holes in parts (blanks) of sheet material.

Stamping is the process of processing materials by pressure as a result of plastic deformation of the workpiece in the dies. For stamping, presses are used as equipment, and stamps are used as tools (equipment).

The proposal relates to the field of cold sheet stamping, namely to devices for processing materials by pressure without heating the workpiece. For sheet stamping, the source material is a sheet, strip, tape. Various materials are subjected to sheet stamping, such as steel, copper, brass, bronze, aluminum, as well as paper, cardboard, rubber and other metallic and non-metallic materials.

In modern mechanical engineering and metalworking, cold stamping takes one of the leading places in terms of the volume of metal processed, in the number and mass of manufactured machine parts, devices and consumer goods. The technological processes of sheet stamping are used at metal-working enterprises, as with

massive and large-scale, and with small-scale and single-character production.

The proposal relates to cold stamping separation operations, namely punching, when as a result of pressure treatment, one part of the workpiece is separated from another along a predetermined contour.

The process of punching holes in the workpiece sheet is similar to the cutting process and consists of three successive stages. This is the stage of elastic deformation, when the tool (punch) only begins to be pressed in and the stresses in the metal do not exceed the elastic limit. Then follows the plastic stage, when the deformations are residual, and the stresses in the metal exceed the yield strength and gradually increase to a maximum corresponding to the tensile strength of the metal during shear. The process is completed by the fracture stage, in which cracks are formed, etched along the sliding surfaces and causing the separation of one part of the metal from another.

The force required for punching depends on many factors: the thickness of the material, the mechanical properties of the material, the shape of the cutting edges of the punch and die, the clearance between the punch and the die, and also the condition of the cutting edges of the stamp.

From scientific and technical information, there are known devices for punching a series of holes in objects made of sheet material, which allow punching holes one at a time, with corresponding relative movement and fixing before punching each hole using dividing and fixing mechanisms [1].

These devices do not require much effort for punching holes, but they are not suitable for the manufacture of parts in which the holes are located close enough to each other, since then there is an accumulation of errors in the location of the holes due to the kinematic error of the dividing mechanism.

Known stamp for punching holes in parts of sheet material, where the width of the jumper between the holes is less than the thickness of the processed material, containing a matrix, punches mounted in the punch holder, a counter-pressure on the jumper [2].

The disadvantage of this device is that such a pattern of installation of punches leads when stamping to a sharp increase in the load on a limited area of the workpiece, which in turn causes its warping. In addition, when the location of the holes in the product is close enough to each other, it is structurally impossible to install punches in one row with high crowding.

Also known is a stamp for punching holes in sheet metal parts, containing a matrix and punches mounted in a puncheon and arranged in concentric rows forming regular polygons, with punches placed at the vertices of the polygons offset relative to each other [3].

The design of this stamp allows you to more evenly distribute the load on the surface of the workpiece and provides sequential punching operations in groups.

However, the known stamp is intended for the manufacture of steel grills for meat grinders and is not suitable for the manufacture of high-quality products from other metals, such as copper. Also, when sequentially punching holes in groups, it is difficult to achieve alignment of the holes, which also reduces the quality of the product.

Closest to the technical nature of the claimed solution is a stamp for punching a group of holes used on an open crank press KD 2330 with a force of 100 tons [4].

This stamp contains traditional parts that are included in all stamping devices for cold stamping. The stamp includes a bottom plate with a matrix placed on the press table, and a top plate with

punch holder, in which the punches are fixed, the puller of the finished product.

A disadvantage of the known device is that it cannot be used for the manufacture of products that require significant effort in excess of the established norm. In industrial enterprises, when carrying out repair work, it is inexpedient to use expensive high-performance equipment for the manufacture of parts that are required in small volumes. Therefore, it becomes necessary to use existing units by changing the equipment.

The technical result of the proposal is to expand the technological capabilities of the press equipment by providing a process for simultaneous punching of multi-row holes on presses with limited capabilities.

To achieve the specified technical result, in the punching stamp containing the upper plate, punch holder, puller, punch group, bottom plate with a die, according to the proposal, the group consists of round and oval contour punches that are made of different lengths with a stepwise height arrangement, and the working The end face of each punch of the oval contour is profiled by the body of revolution.

According to the proposal, in the manufacture of the stamp, the punch holder, together with the punches, which are fixed in it by pins, are assembled in a bag and fastened together by a binder composition with subsequent exposure for at least 24 hours.

The presence of the above distinguishing features indicates the conformity of the claimed technical solution to the patentability criterion of "novelty."

The essence of the proposal is illustrated by drawings, where figure 1 shows a longitudinal section of a stamp; figure 2 shows the matrix in plan; figure 3

the punch holder is shown in plan; figure 4 shows a longitudinal section aa of the punch holder; figure 5 presents the punches of the oval and round contour.

It should be noted that for clarity, only those details are presented that are necessary for understanding the essence of the technical solution, and related equipment, well known to specialists in this field, is not shown in the drawings.

The inventive stamp is intended for the manufacture of such parts as, for example, reinforcing board TE1-02.013, which is used to repair the water sections of diesel locomotives. The detail “reinforcing board” has a large number of holes (68 oval and 16 round), which in their location are repeated in increments of two rows.

Typically, in serial production, such parts are performed on equipment with automatic strip feeding, which makes it possible to produce tooling with the least number of repeating elements (in this case, two rows, that is, 17 oval and 4 round punches).

However, such expensive equipment is ineffective in small-scale production of products, the need for which arises as needed only for repair. In accordance with the technical requirements for the part “reinforcing board TE1-02.013”, the alignment deviations of the holes are minimal and amount to 0.1 mm. In this regard, element-wise stamping during manual feeding of the workpiece is unacceptable. Therefore, to obtain a high-quality product, it is necessary to perforate all holes at one stroke of a stamp.

Felling and punching - metal separation in a closed loop in a stamp. When cutting and punching the nature of the deformation of the workpiece is the same. These operations differ only in purpose. Cutting out the outer contour of the part, and punching - the inner contour (making holes).

When choosing a press, the cutting (punching) force is calculated by the formula: P = L _total . S σ _cf , where L _total - total perimeter of the punching contour (mm); S is the thickness of the stamped material (mm); σ _cf - shear resistance (MPa). For amplification board:

L _total = 68 (2 × l6.8 + π2R) + 16πD = 68 × 40.83 + 16 × 13.19 = 2987.44 mm.

S = 3 mm.

σ _cf = 16 MPa for soft copper, σ _cf = 24 MPa for solid copper [5].

Thus, the force for punching a sheet of soft copper was PM = 2987.44 × W × 16 = 110.31 tons, and for solid copper - RT = 2987.44 × W × 24 = 215.10 tons.

In addition, when selecting a press, the force to push the waste out of the matrix is added to the cutting (punching) force: Rpd = 0.1R.

Therefore, for a sheet of soft copper, Rpd = 0.1 × 110 = 11 t, and for solid copper, Rpd = 0.1 × 215 = 21.5 t [6].

The indicated forces act simultaneously; therefore, the required press force is calculated by the formula:

RPpress = 1.25 (P + RPD),

RPpress = 1.25 (110.31 + 11) = 151.64 tf for a sheet of soft copper,

RPpress = 1.25 (215D0 + 21.5) = 292.75 tf for a sheet of solid copper.

The claimed technical solution allows to reduce the cutting force by almost half and to use the KD 2330 crank press with limited force capabilities for the manufacture of reinforcing boards.

Crank press - a machine with a crank-slide mechanism, designed for stamping various parts. The working part of the press is a stamp, the fixed part of which is attached to the table, the movable part - to the slider of the press. The slider is moved by a crank-slide mechanism. For one revolution of the crank, the connecting rod makes a full stroke, during which stamping occurs when the slider moves forward. The force of the press is created due to the torque transmitted by the electric drive to the crank shaft. The drive consists of

an electric motor, a flywheel, an engagement clutch, a brake and a reduction gear, from which rotation is transmitted to the crank shaft. The electric motor rotates the flywheel, due to the inertia of which a torque appears on the crank shaft.

The stamp (figure 1) includes a lower fixed plate with a matrix of 1, while the plate is fixed to the press table (not shown). In the matrix 1 (figure 2), windows 2 and 3 are made of two types, respectively: 68 oval and 16 round. In the manufacture of the matrix 1, round holes 3 and blanks for oval holes 2 on the coordinate machine were originally made. Then, using a special red-hot device, oval holes 2 were punched in the crude matrix (first, a smaller rough size, and then a fine one with a minimum allowance for grinding). This excluded the milling of 84 windows of the matrix 1, which reduced the complexity of manufacturing the stamp, since the slightest error during milling spoils the entire part (matrix) at any stage of manufacture.

The device also contains an upper plate, which is attached through a shank to a press slider (not shown in the drawing). A punch holder 4 (FIGS. 3, 4) is fixed on the upper plate, in which punches 5 (68 pieces) and 6 (16 pieces) are fixed. In shape, punches 5 (oval) and 6 (round) are similar to windows 2 and 3 of matrix 1, respectively, but are smaller. The punches 5 and 6 are exposed (during installation) along the matrix 1 with the formation of a technological gap of 0.08 mm between their working side surfaces and the surfaces of the windows 2 and 3 of the matrix 1.

The working end face of each oval punch 5 is profiled by a body of revolution (Fig. 5), that is, it is made with sharpening along a radius R = 20 mm. Round punches 6 have a small diameter (6 mm), they have a flat end. Moreover, half of the punches 5 (34 pieces) and half of the punches 6 (8 pieces) are made of different lengths, short and long, and the height difference is H = 2.5 mm.

The stamp includes a puller 7 manufactured parts. To prevent tearing of punches 5 and 6 from the punch holder 4 during removal of the part by the puller 7 (pulling force of about 30 tf), pins 8 are inserted into the punches 5 and 6, which are located in the socket of the puncheon 4. The assembled package (punches 5 and 6, pins 8 and the punch holder 4) is poured with a binder, and after holding the assembly for at least 24 hours, the upper part of the bag is ground. A further stamp assembly scheme remains classic.

The device operates as follows.

A blank (a card 192 × 142 × 3) is fed into the stamp between the guide strips. When the press pedal is pressed, compressed air from the pneumatic system enters the clutch and transmits its movement to the crank. The crank begins its movement and pushes the slider press with the upper part of the stamp, which moves along the guides. The stamp closes.

When the slide moves downward, the punches 5 and 6, encountering a strip of material on their way, pierce the necessary holes, first with long punches, and then short. Then the press slider moves up. The part is removed by the puller 7.

In the claimed technical solution, the combination of known and newly introduced features allows to reduce the hole punching force and use a press with a force of 100 tons for the manufacture of reinforcing boards made of soft or hard copper.

The smallest value of the cutting (punching) force is obtained at optimal technological gaps for each stamped material and its thickness corresponding to such cutting conditions at which cracks coming from the punch and die converge (in our example 0.08 mm). This contributes to obtaining the cleanest cut surface, the absence of burrs and the preservation of the resistance of the stamp.

If the gap between the punch and the die is small, then cleaving cracks do not coincide with each other and the cut surface will be uneven, with

double belt. An excessively large gap leads to tearing and burrs along the contour of the part. When punching holes, the technological gap is provided by increasing the working hole of the matrix, and the size of the punch is equal to the size of the hole.

It is well known that the use of bevels reduces punching forces by up to 50% compared with the force required when working with a stamp with parallel cutting edges. Since punching does not occur simultaneously along the entire contour, but gradually, as the punch drops, the punching force will be less.

In our solution, the matrix is made flat, the bevel is formed on the punches, in this case the part remains flat, and the waste pushed out of the matrix is bent. Each of the oval punches is made with sharpening the end along the radius. The bevel must be two-sided and symmetrical with respect to the center of pressure of the stamp, since otherwise lateral forces arise that lead to a defect in the cutting edges, and the sharpening of the end along the radius reliably ensures that this condition is met. The experiments showed that to reduce the force by half, bevels are enough only on oval punches, therefore round punches are made with a flat end, without a bevel.

In order to reduce forces during multi-punching, punches are made of different lengths with a stepwise height arrangement. Reducing the load on the press occurs because the cutting forces occur at the same time. The difference H between the length of the punches usually varies within equal to half the thickness of the workpiece to a value equal to the thickness of the workpiece (the value of H for our example is 2.5 mm).

The device was developed and successfully used at the Orenburg Locomotive Repair Plant.

From the above it follows that the manufacture of this device in an industrial way does not cause difficulties, involves the use of developed materials and standard equipment, which

indicates the conformity of the claimed technical solution to the patentability criterion of "industrial applicability".

Information sources:

1 Copyright certificate SU No. 375119, B21D 28/26, 1973;

2 Copyright certificate SU No. 1183241, B21D 28/14, 1985;

3 Patent RU No. 2165324, B21D 26/14, 2001;

4 Operation manual KD2330-00-001-02RE, part 1, Standard, 1980;

5 Stamps for cold stamping. State Publishing House of Standards, Moscow, 1962. Appendix 20, p. 262;

6 Rudman L.I., Stamp Designer Handbook, Moscow, Mechanical Engineering, 1988, p. 58.

Claims (4)

1. A stamp for punching holes containing an upper plate, a punch holder, a puller, a group of punches, a lower plate with a die, characterized in that the group consists of punches of round and oval contours, which are made of different lengths with a stepwise height, and the working end face of each punch The oval contour is profiled by the body of revolution. 2. A stamp for punching holes according to claim 1, characterized in that during its manufacture, the punch holder, together with the punches, which are fixed in it with pins, are assembled in a bag and fastened together by a binder composition with subsequent exposure for at least 24 hours. 3. The stamp for punching holes according to claim 1, characterized in that the difference in the lengths of the punches is 2.5 mm 4. A stamp for punching holes according to claim 1, characterized in that the working end face of each oval punch is made with sharpening along a radius of R = 20 mm.