O DESCRIPTION ()664722
INVENTED AND I
Union of Soviets
Socialist
D. N. Korneev (71) Applicant (54) STAMP FOR CRIMPING TUBULAR BILLETS
The invention relates to metal forming and can be used for stamping parts mainly from thin-sheet materials.
Crimping dies are known, consisting of a lower part placed on the press table and an upper crimping die with a spring-loaded ejector (1) installed concentrically inside it.
The workpiece is placed in the lower part, and crimping is performed by the upper die using a press blow; the finished part is pushed out of the upper part of the die by a spring-loaded ejector. The disadvantage of the known stamp is that it can only crimp parts with relatively thick walls. The ratio of the thickness of the material to the diameter of the crimping contour when crimping in a known stamp is determined and, in order to avoid the formation of folds, it should not exceed certain values.
It is known that this drawback is partially eliminated in a stamp for crimping hollow workpieces, containing a coaxially installed punch, a clip for external support of the workpiece, a matrix, a mandrel and an ejector. The mandrel is made in the form of bushings made of elastic material mounted on the punch and concentrically installed, and on the ejector a profiled liner is installed, which fits into the hole in the inner sleeve of the mandrel. The disadvantage of such a stamp is that it can only crimp hollow through workpieces without a bottom (2).
There is also another known stamp for crimping thin-walled workpieces, containing a base, a matrix and a clamping means, including an elastic punch with a punch holder, an elastic buffer. The matrix is made in the form of two coaxially located parts, one of which is mounted on
15 on the base and is spring-loaded in the axial direction, and the other is installed concentrically with the punch with the possibility of axial movement with it, while the elastic buffer is placed along the axis of the stamp between the punch holder and the other part of the dies and has greater rigidity than the elastic punch (3).
The stamp works as follows.
The workpiece is installed in the lower part of the matrix. When the press slide moves downwards, both parts of the matrix are closed, the elastic punch, compressing, fills the entire space of the matrix, pressing the workpiece against the walls of the matrix. With further movement of the slider, the upper part of the matrix 664722 compresses the workpiece, and the punch holder moves upward, compressing the elastic buffer.
This device is closest to the invention in terms of technical essence and achieved result.
However, the pressure with which the elastic punch presses the workpiece against the die walls varies throughout the entire length of the press slide stroke, reaching its maximum value at the end of the stroke. It is not adjustable and ultimately depends on the stiffness and overall dimensions elastic buffer.
The technological capabilities of the stamp are limited when crimping hollow parts with a bottom. When crimping a part without a bottom, the crimped workpiece, at the beginning of the upward movement of the upper part of the die, is pressed against the matrix with an elastic punch until the elastic punch takes its original shape. When crimping the walls of a vessel with a bottom, all the pressure that creates an elastic buffer inside the workpiece is absorbed by the walls of the vessel. This circumstance makes it possible to crimp only vessels that are strong enough to withstand the pressure created during crimping.
The purpose of the invention is to expand the technological capabilities of the stamp, namely to provide the possibility of crimping vessels with relatively thin walls and having a bottom without the formation of folds by providing the ability to regulate the pressing force of the punch.
This goal is achieved by the fact that the known stamp is equipped with a hydraulic cylinder, the body of which is made in a matrix along its axis, and the piston is connected to an elastic punch, and a hydraulic accumulator connected to the piston cavity of the hydraulic cylinder. A pipeline with a valve that regulates the fluid pressure.
The presence of hydraulics makes it possible to regulate, using valves, the pressure inside the die (clamping force) to the required extent and remove this pressure, in accordance with technological feasibility, which cannot be done in known dies.
The drawing shows a cross-section of a stamp, and the half of the drawing to the left of the axis depicts a stamp in open position, and the right one is closed.
The stamp consists of a crimping matrix 1, mounted on a press slide, with a piston 2 placed inside it, at the bottom of which a punch 3 made of elastic material is fixed. The space above the piston is connected by a pipeline 4 with a hydraulic accumulator 5 through check valve 6 and an adjustable valve 7. The lower part of the die, installed on the press table, consists of a movable holder 8, spring-loaded
65 clamps 9, and a fixed base 10, on which the workpiece 11 is installed.
The stamp works as follows.
The workpiece 11 is installed in a movable holder 8 on the base 10. When the press slide moves downwards, the punch 3 touches the bottom of the workpiece, is deformed and fills the cavity of the workpiece. The lower edge of the crimping die 1 touches the holder 8 and with further downward movement the elastic punch fills the entire cavity of the workpiece 11 and the crimping die cone 1 before the base of the matrix cone touches the upper edge of the workpiece. The pressure above piston 2 increases during the adjustment of valve 7, and piston 2 remains in place. When the slider further moves downwards, the pressure above piston 2 increases sharply, and the liquid, overcoming the force of the valve spring 7, flows into the hydraulic accumulator 5. Piston 2 moves upward, and the cone of the matrix 1 compresses the wall of the workpiece 11.
When the slider reaches its lowest position, external pressure on valve 7 releases pressure above piston 2 under the action of an elastic punch
3, piston 2 moves upward, and the elastic punch partially frees the cavity of the product. When the press slide moves upward, piston 2 moves downward under the pressure of hydraulic accumulator 5. Fluid enters the space above the piston through check valve 6. Part 11 is pushed out of the crimping die by an elastic punch 3.
An essential point for the design of the stamp is the ability to regulate the clamping pressure and release this pressure at the moment when the pressure inside the workpiece is perceived by the matrix.
Both of these circumstances together expand the technological capabilities of the die, make it possible to crimp thin-walled parts that are currently manufactured using a rotary hood and, ultimately, provide increased productivity in these operations.
Claim
A stamp for crimping tubular blanks, containing a holder mounted on the base, a matrix and a pressing elastic punch installed coaxially with the matrix, characterized in that, in order to provide the ability to regulate the pressing force of the punch, it is equipped with a hydraulic cylinder, the body of which is made in the matrix along its axis, and the piston the hydraulic cylinder is connected to an elastic punch, as well as a hydraulic accumulator connected to the above-piston cavity of the hydraulic cylinder by a pipeline with a valve that regulates the fluid pressure
Compiled by I. Kapitonov
Techred N. Stroganova
Proofreaders: L. Orlova and A. Galakhova
Editor V. Kukharenko
Order 82812 Ed. No. 337 Circulation 1034 Subscription
NPO of the USSR State Committee for Inventions and Discoveries
1I3035, Moscow, Ya-35, Raushskaya embankment, 4/5
Printing house, Sapunova Ave., 2
Sources of information taken into account during the examination
1. Sheet stamping, atlas of diagrams, M., Mechanical Engineering, 1975, p. 115, fig. 308.
The utility model relates to metal forming, in particular to stamping of parts with elastic media from tubular blanks. The stamp contains a matrix consisting of upper and lower parts, a punch, and an elastic medium. The matrix is located in a container and a tubular blank with an elastic medium placed in it is installed in it; a hole of variable diameter is made in the lower and upper parts of the matrix, which ensures crimping of the end sections of the tubular blank and distribution of its middle part. The technical result consists in increasing the technological capabilities of the operation of stamping parts from tubular blanks due to the simultaneous performance of crimping and distribution of the tubular blank.
The utility model relates to metal forming, in particular to stamping of parts with elastic media from tubular blanks.
A device for distributing pipes is known (Use of polyurethane in sheet metal stamping production / V.A. Khodyrev - Perm: 1993. - p. 218, see p. 125), consisting of a split matrix and a punch. The matrix contains a tubular blank, inside of which an elastic medium is placed. This device makes it possible to produce parts from pipes by dispensing a tubular blank with elastic media over a rigid matrix.
The disadvantage of this device is its low technological capabilities. The device allows only pipe expansion, which manifests itself in an increase in the cross-sectional size of the tubular blank, determined by the limiting coefficient of forming.
The objective of the claimed utility model is to increase the technological capabilities of the operation of stamping parts from tubular blanks. The technical result achieved by the claimed utility model is to increase the technological capabilities of the operation of stamping parts from tubular blanks due to the simultaneous performance of crimping and distribution of the tubular blank.
This is achieved by the fact that in the stamp for distributing and crimping a tubular billet, containing a matrix consisting of upper and lower parts, a punch, an elastic medium, in the lower and upper parts of the matrix there is a hole of variable diameter, which ensures crimping of the end sections of the tubular billet and distribution of its middle parts.
What is new in the claimed device is that the matrix is located in a container and in the lower and upper parts of the matrix there is a hole of variable diameter, which ensures crimping of the end sections of the tubular workpiece and distribution of its middle part.
Due to the fact that the matrix, consisting of upper and lower parts, is located in the container, reliable movement of the upper part of the matrix is ensured, because the container serves as a guide for it. Due to the fact that in the lower and upper parts of the matrix there is a hole of variable diameter, which ensures the compression of the end sections of the tubular workpiece and the distribution of its middle part, in combination with other features, simultaneous compression of the ends of the tubular workpiece and the distribution of its middle part are ensured. Due to the fact that in parts of the matrix there is a hole of variable diameter so that in those places of the matrix where the end sections of the tubular workpiece are installed, the diameter of the hole is made smaller than the diameter of the pipe workpiece, this will ensure compression of the end sections of the workpiece. Due to the fact that the diameter of the hole is variable, namely, it is made larger than the diameter of the tubular blank in those parts of the matrix where the middle part of the tubular blank will be, it is possible to distribute its middle part. In addition, making holes in parts of the matrix with variable diameter, i.e. from a diameter smaller than the diameter of the pipe blank to a diameter larger than the diameter of the pipe blank, ensures vertical installation of the pipe blank in the matrix.
The design of the die allows for simultaneous crimping of the end sections of the pipe blank and distribution of its middle part.
The applicant is not aware of objects with this set of essential features, therefore, the claimed technical solution is novel.
The utility model is illustrated graphically. The figure shows a stamp for distributing and crimping a tubular blank.
The stamp includes a lower part 1 of the matrix, a container 2. A tubular blank 3 is installed vertically on the lower part 1 of the matrix. The stamp also includes an upper part 4 of the matrix, an elastic medium 5, for example, polyurethane granules. The finished part 6 is obtained from the workpiece 3. The elastic medium 5 is located in the tubular workpiece 3 and in the hole 8 of variable diameter in the upper part 4 of the matrix and in the hole 7 of variable diameter in the lower part 1 of the matrix; the die also includes a punch 9.
The stamp works as follows: the lower part 1 of the matrix is installed in the container 2, a tubular blank 3 is vertically inserted inside the lower part of the matrix, and the upper part 4 of the matrix is installed on top. The elastic medium 5 is poured into the hole 8 in the upper part 4 of the matrix into the tubular workpiece 3 and into the hole 7 in the lower part 1 of the matrix. By moving the press slide (not shown in the figure) with force P, the punch 9 moves, which causes the upper part 4 of the matrix to move, which leads to the movement of the tubular workpiece 3 into the hole 8 of variable diameter in the upper part 4 of the matrix and to the movement of the tubular workpiece 3 into hole 7 of variable diameter in the lower part 1 of the matrix, which leads to compression of the end sections of the tubular workpiece 3. Force P is also transmitted to the elastic medium 5, through which in turn it is transmitted to the walls of the tubular workpiece 3, which leads to the distribution of its middle part. After the press slider and punch 9 reach the maximum upper position, a recess is made finished part 6 and elastic medium 5 in reverse order.
A stamp for distributing and crimping a tubular workpiece, containing a matrix consisting of upper and lower parts, a punch, an elastic medium, characterized in that the matrix is located in a container and is made with holes of variable diameter in the lower and upper parts to allow crimping of the end sections of the tubular workpiece and simultaneous distribution of its middle part.
The dimensions of pipe parts are checked after each technological operation. Tolerances for dimensional deviations are specified in drawings and technical specifications for the supply of parts.
After the operation, the length of the workpiece or part is checked with a normal measuring instrument: ruler, tape measure, caliper, etc.
Control of the shaped cut of pipe ends can be done using end or solid templates that are placed on the pipe, similar to contour trim templates (SHOK).
If there are increased requirements for the quality of the shaped pipe cut, special plazas are made for inspection.
SEALING PIPE ENDS
Flaring
Flaring of pipe ends is the most commonly used operation in the manufacture of detachable nipple connections for pipelines of aircraft hydraulic and oil systems. Flaring of pipes with a diameter of up to 20 mm and a wall thickness of up to 1 mm can be done manually using a cone mandrel in two ways. To do this, the end of the pipe is clamped in a device pos.2 , consisting of two halves with a socket along the outer diameter of the pipe and a conical part in the shape of a flaring and a mandrel pos.1 apply several blows with a hammer or rotate the mandrel manually pos.3 until the required cone dimensions are obtained.
Flaring of pipes with a diameter of up to 20 mm and a wall thickness of up to 1 mm can be done manually using a cone mandrel in two ways. To do this, the end of the pipe is clamped in a device 2 , consisting of two halves with a socket along the outer diameter of the pipe and a conical part in the shape of a flaring and a mandrel 1 Apply several blows with a hammer or rotate the mandrel manually until the required cone dimensions are obtained. However, when flaring using these methods, it is difficult to obtain the required correctness and cleanliness of the inner conical surface. These qualities are especially important for nipple connections, in which tightness is created without additional seals. In addition, these methods are ineffective. Therefore, it is more rational to flare the ends of the pipes on special pipe-flaring machines. The essence of the process of flaring pipe ends on a machine is to obtain a conical
The socket is socketed by a concentrated force from inside the pipe using a rotating tool.
When flaring, the original pipe wall thickness decreases S 0
before S 1
. The wall thickness at the flaring edge can be calculated using the formula 
Where S 1 --- thickness walls at the end of the bell;
S 0--- pipe wall thickness in the cylindrical part;
D0 ---outer pipe diameter before flaring;
D 1--- outer diameter of the pipe after flaring. Flaring of short pipes is carried out using flaring dies.
Pipe end crimping
Pipes with crimped ends are used in the design of rigid aircraft control rods. The crimping process diagram is shown below.
Under the influence of compressive forces R there is a decrease in diameter with D0 before d, thickening of the wall with S 0 before S 1 and pipe extension with L 0 before L 1 .
There are two ways to crimp the ends of pipes. First way. Crimping by pushing the pipe into a ring die. 
The diagram of a pipe crimping die is shown above. Blank part (pipe) pos. 2 with diameter D0 placed in a matrix, position 3, which has a conical entry and calibrating part with a diameter d. During the working stroke of the press slide, the punch position 1 fixes the pipe along the outer diameter and pushes its lower part into the matrix, compressing the end of the pipe to the diameter d.
The limit for reducing the diameter of the original pipe is determined by the loss of stability (longitudinal bending) of the wall of the uncompressed part and the plasticity of the material. Buckling occurs when the stress in the material reaches its yield point. The stability of the pipe wall is affected by the ratio of pipe thickness to outer diameter S 0 / D0.
The maximum degree of pipe compression is determined by the limiting value of the compression ratio Kobzh, .
For increase Kobzh a pipe wall support is used between the matrix and the punch, preventing loss of stability.
Good results are obtained by local heating of the end of the pipe, which reduces the yield strength of the material in the deformed part. Due to the decrease in pressure on the pipes, loss of stability occurs much later. This method is especially effective when crimping pipes from aluminum alloys. Due to the high thermal conductivity of these alloys, it is not the pipe that is heated, but the matrix; the pipe heats up from contact with the matrix.
Second way. Crimping in split dies.
According to the first method, it is not advisable to crimp long pipes, since presses with a large closed height, large dies and special clamps are needed to protect the pipe from longitudinal bending. The method of crimping the ends of especially long pipes using split dies is more widespread. A diagram of the process is shown.
Scheme of the process of crimping the ends of pipes with split dies. Pos. 1 and 3 – upper and lower die strikers, pos. 2 – pipe, pos. 3 – calibrating mandrel.
Upper and lower strikers pos. 1 And 4 The stamps have a working part machined in a closed state and corresponding to the shape of the compressed part of the pipe. The strikers make a frequent back-and-forth movement (vibrate), squeezing the end of the pipe pos.2. The pipe is gradually fed into the stamp until the required length of the compressed part is obtained.
In cases where it is necessary to obtain the exact internal diameter of the compressed part of the pipe, a calibrating mandrel is inserted inside pos.3 and feed it into the stamp along with the pipe. After the process is completed, the mandrel is removed from the pipe. The advantages of the process of crimping pipe ends in a vibrating split die are as follows:
a) more favorable conditions are created for plastic deformation than when crimping with a ring matrix;
b) the axial force of the pipe into the die Q is significantly less than in the first method;
c) the number of transitions decreases;
d) a mandrel can be used, which makes it possible to obtain a calibrated internal diameter of the pipe without subsequent machining.
30. Typical designs of dies for drawing parts with a flange, stepped and conical shape.
With flange:
A typical design of a drawing die with a fold holder 2, operating from the buffer of a universal press, is shown in Fig. 229, a. The transmission link between the press buffer and the fold holder is the buffer pins /. The finished part is removed from the matrix 4 at the end of the lifting of the slider through the ejector 5 and the pusher 6. If the bottom of the stamped part is flat and located perpendicular to the drawing axis, then when the die is closed, a gap z is left between the ejector 5 and the upper plate 3, i.e. work without "hard" blow.
The process of converting a sheet blank into a hollow one using a fold holder is accompanied by complex loading of the material, especially in the flange area. The flange experiences tangential compression from compressive stress a, (Fig. 229.6), which is the main deformation of the material in this zone, radial tension from tensile stress o r and
shaping.
Conical shape:
Drawing low conical parts is usually done in 1 operation, but is complicated by the fact that art. The deformation of the workpiece is small (with the exception of places adjacent to the rounded edges of the punch), as a result of which the hood “springs back” and loses its shape. Therefore, it is necessary to increase the clamping pressure and
Rice. 229. Drawing out a hollow glass with workpiece clamping
create significant tensile stresses in the deformable workpiece that exceed the elastic limit
material, through the use of a matrix with exhaust ribs (Fig. 134, a).
In Fig. 134, b shows another method of drawing shallow but wide cones (lamp reflectors), produced in a stamp with a conical clamp. Drawing of this type of parts can also be done well hydraulic stamping. In most cases, drawing conical parts of medium depth is carried out in 1 operation. Only with a small relative thickness of the fastener, as well as in the presence of a flange, 2 or 3 drawing operations are required. When stamping parts from relatively thick material (S/D)100>2.5, s
a small difference in diametrical dimensions, the hood can occur without pressing, similar to the hood cylindrical parts. IN in this case calibration is required at the end of the working stroke with a dull blow. In the manufacture of thin-walled conical parts, this means. By the difference in the diameters of the bottom and top, a simpler rounded shape with a surface equal to the surface of the finished part is first drawn out, and then a finished part is obtained in a calibration stamp. form. Technological calculations of transitions here are the same as when drawing cylindrical parts with a flange. mn = dn /dn-1, dn and dn-1 are the diameters of the current and previous hoods.
Stepped shape:
Of particular interest is the dual process, combining a conventional hood with an inversion hood.
Reversible drawing brings great effect when stamping step-shaped parts. A typical example is the multi-step process for stamping deep parts such as car headlights. First, a cylinder or hemisphere is pulled out, and then the workpiece is pulled in the opposite direction (inverted) to obtain the desired shape of the product.
Schemes of reversible (reversible) hood
31. Typical designs of dies for flanging.
Flanging dies can be divided into two groups: dies without clamping the workpiece and stamps with clamping the workpiece. Dies without clamping the workpiece are used only when beading large products, where there is no fear of the workpiece being overstretched during flanging. Full clamping of the workpiece can usually be achieved by using flanging dies of the second group with strong pressure.
In Fig. 207, and a flanging stamp is presented with a lower clamp, operating from a rubber buffer 1 placed under the stamp, which transmits pressure through the washer 2 and rods 3 to the pressure plate 5. When lowering the upper part of the stamp, the workpiece 6, laid on the plate 5 so that the flanging punch 4 with its upper protrusion enters the preliminary hole, is first clamped by matrix 7, and then beaded. Ejecting the product from the top of the die after flanging can be done using a conventional rigid ejector (rod) operating from the press itself, or, as shown in the figure, using springs 9 and ejector 8.
When flanging larger products, instead of a rubber buffer or spring, it is better to use pneumatic or hydropneumatic devices.
In Fig. 207, b shows a similar stamp with an upper clamp for flanging a hole in the tractor clutch. Here, the product 4 is pressed when the upper part of the die is lowered by the plate 3, which is under the action of sixteen springs 2 located in a circle around the flanging punch 1.
Pressing the annular part of the material from below during the flanging process and subsequent ejection of the product from the matrix 5 after flanging is carried out by the ejector 6, which receives movement through the rods 7 from the lower pneumatic cushion of the press.
32. Typical designs of stamps for distribution.
The design of the dispensing die depends on the required degree of deformation, which
characterized by the distribution coefficient Krazd. If Krazd > Krazd. limit . , when local loss of stability is excluded, then a simple open stamp with a conical punch is used
(for free distribution) and a lower cylindrical clamp along internal diameter pipe blank, which is fixed to the bottom plate of the die.
At higher degrees of deformation,
when Krazd< Кразд.прел . применяют штампы со скользящим внешним подпором (рис. 1).
Fig. 1. Dies for distributing the ends of tubular blanks with sliding external support.
The stamp consists of an upper plate 1 and a conical punch 2 and rod pushers 3 attached to it. A cylindrical support mandrel 5 is fixed to the lower plate 7, the diameter of which D is equal to the outer diameter of the pipe blank. A support sleeve 4 moves along the mandrel, supported by springs 6. When the sleeve is in the upper position (shown in the figure with a dashed line), the workpiece is installed on the shoulder of the mandrel 5, and the workpiece protrudes from the sleeve by
(0.2-0.3) D.
When the top of the die is lowered, the conical punch enters the workpiece and begins to push it out.
At the same time, pushers 3 press on the support sleeve 4 (compressing the springs 6) and move it down along the mandrel, thereby allowing the punch to completely expand the pipe blank until
required sizes. During the reverse stroke, spring 6 lifts sleeve 4 up along with the stamped part.
The operation is mainly designed to increase the diameter of a cylindrical workpiece for
pipe joining. Optimal angle distributions 10300.
Figure 2.1-punch, 2-bushing, 3-pusher, 4- |
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the rod acts as a support. In stamps where |
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there is no possibility of loss of stability; they are used |
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dies without free part support |
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blanks. |
If the diameter of the initial hollow cylinder is d0, then the largest diameter is d1, up to which distribution can be carried out (Fig. 3).
d1 ,=Ksection * d0, where Ksection is the expansion coefficient depending on the relative thickness
blanks. s/d0 =0.04 Ksection =1.46 s/d0 =0.14 Ksection =1.68. The thickness of the material decreases during distribution. The smallest thickness at the point of greatest stretch is determined by
formula. s1 = s √ 1/ Ksection
Dispensing can be carried out at the edges of a hollow workpiece or at its middle part in dies with split dies, elastic media and other methods.
The dimensions of the workpiece for distribution are determined based on the equality of the volumes of the workpiece and the part without taking into account changes in the thickness of the metal.
Fig. 3. a - elastic punch. b- in detachable matrices.
33. Typical designs of crimping dies.
Crimping dies are divided into two groups : dies for free crimping and dies with workpiece supports. Stamps of the first group They have only guide devices for a tubular or hollow workpiece, without internal or external supports, as a result of which loss of stability during crimping is possible. To prevent loss of stability, the workpiece in one operation receives a shape change in which the required crimping force will be less than the critical one.
Rice. 1. Schemes of dies for free crimping of ends - parts.
In Fig. Figure 1 shows two diagrams of free crimping dies: on the first stamp, the end of pipe 3 (Fig. 1, a) is crimped in a stationary die, and on the second stamp, the neck is crimped
on a hollow product 3 (Fig. 1, b) is carried out by a movable matrix 1, fixed on the upper plate of the die using a matrix holder 5. To fix the workpiece, there is a cylindrical belt either on the matrix /, or on the plate 4. Removal of parts is carried out by ejector 2, powered by lower or from the upper buffer. The length of the compressed part is set by changing the stroke of the press.
In Fig. 2, a shows a diagram of a die with external support; in him
the part of the workpiece that is not subjected to crimping is covered by an outer ring 2, which prevents loss of stability and bulging of the workpiece outward. Due to this, such dies can produce a greater degree of deformation than in dies without supports. To facilitate installation of workpieces and removal of crimped parts from holder 2, it is made detachable; in the non-working state, it is unclenched by springs 1. The clamp is closed around the workpiece by moving the upper part of the die downwards with wedges 4. To remove the compressed part from the matrix 5, the die is equipped with an ejector 3, operating from a spring 6 or from a crossbar in the press slide.
There are also dies with a sliding outer ring that supports the workpiece along its entire undeformed part.
In Fig. 2, b and c show dies for crimping the end part of a pipe or hollow workpiece into a sphere, equipped with external (Fig. 2, c) or external and internal (Fig. 2, b) supports for the workpiece.
Rice. 2. Diagrams of dies for crimping the ends of parts with supports These dies allow you to make significant shape changes in one operation,
due to which the number of operations during multi-operation stamping is reduced. In a stamp intended for crimping the end part of a pipe (Fig. 2, b), the pipe blank is installed in the gap between the outer sliding race 2 and the internal rod base 3, on which there is a step to support the end of the blank. An insert is pressed into the hole of the rod 3, which has a spherical head along which the workpiece is crimped. In the stamp for crimping a hollow workpiece (Fig. 2, c), liner 6 is missing. The workpiece is installed along the holder 2 and the base rod 3.
When the press slide moves downwards, matrix 1 moves the sliding cage 2 downwards and compresses the workpiece along the sphere. The clip operates from the lower buffer through rods 4, sliding in the lower plate 5. The part is pushed out when the press moves upward with the insert 6, also connected to the lower buffer.
The operation is widely used for the production of cartridge cases. The optimal taper angle is 15-200. Feature of stamps There is a need to ensure the stability of the workpiece during the crimping process. Dies are divided into: 1. without workpiece support 2. with workpiece support. Without support it is rarely used and for relatively thick-walled workpieces.
Possibility of crimping cylindrical workpieces in one operation orped coefficient. crimping
d ,=Kobzh * D, where Kdiv is the distribution coefficient depending on design features stamp and type of material. Table 5.
Kobzh also depends on the relative thickness of the material. For mild steel (α=200).- s/D=0.02 Kobzh
0.8; s/D=0.12 Kobzh =0.65.
As the taper angle decreases, the value of Kobj decreases. The wall thickness at the crimp site increases due to compression of the metal. Greatest thickness at the place of greatest compression is determined by the formula.
s1 = s √ 1/ Kobzh
34. Design of dies with working elements made of hard alloy.
TV The alloy is ceramic (not metal) carbide W. Tv. alloys have an increased tendency to fracture, therefore only if special design and technological requirements are met is it possible reliable operation dies with working elements made of hard alloys, the so-called hard alloy dies, and increasing their durability by tens and hundreds of times compared to dies with steel working elements. Modern designs carbide dies should provide compared to steel increased rigidity, more accurate and reliable direction of the upper part of the die in relation to the bottom, maximum approximation of the shank axis to the center of pressure of the die, durability and reliability of removal units and elastic elements, increased wear resistance of the strip guides, a possibly greater number of regrinds and the absence of stress concentration on the carbide.
Increased rigidity and strength of the slabs is achieved by increasing their thickness. For matrices with a plan size of 350x200 mm, the recommended thickness of the bottom plate is 100-120 mm. The bottom and top plates and the stack plate are made of 45 steel. These plates are heat treated to a hardness of 30-35 HRC. The deviation from the flatness of the matrix base and the adjacent surface of the lower die plate, as well as the rear part of the punches with the punch holder and the adjacent surface of the upper plate (or intermediate backing plate) should not exceed 0.005 mm. Failure to comply with this requirement can reduce the durability of the stamp several times.
Carbide die screws are made from 45 steel and then heat treated. It should be taken into account that even slight stretching of the screws leads to a decrease in the durability of carbide dies.
A more accurate and reliable direction of the upper part of the carbide die in relation to the lower part, compared to steel, is achieved by using rolling guides (at least 4). The recommended tension in ball guides is 0.01-0.015 mm. In some cases, an interference of 0.02, -0.03 mm is used. An increase in tension leads to a decrease in the durability of the guides. However, it is advisable to increase the tension when cutting thin material up to 0.5 mm thick or when working on worn-out pressing equipment. The durability of rolling guides is 10-16 million operating cycles, depending on the amount of tension. Columns and bushings are made of steel ШХ15. After heat treatment Their hardness is 59-63 HRCе. Roller guides are used when cutting material up to 1.5 mm thick.
Elimination of stress concentration in the hard alloy is achieved by rounding the corners in the matrix windows with a radius of 0.2-0.3 mm (with the exception of the working angle in the window of the step knife of the sequential stamp) and by determining the thickness of the matrix, the minimum width of its wall and the distance between the working windows on the basis corresponding calculations.
Ensuring the durability and reliability of strip removal elements and strip guidance is achieved by reinforcing strippers with hardened steel plates and carbide elements, using carbide guide rods and release agents for strip direction and lifting, and using new stripper designs. The most common are two types of peelers: those that provide the direction of the strip as it moves over the matrix (Fig. 1 a) and those that do not provide it (Fig. 1, b). The use of the latter requires the presence in the stamp individual elements to guide the strip.
In most cases, moving pullers are performed on rolling guides. The guides have the greatest rigidity if the columns are rigidly fixed to the puller (Fig. 2). To avoid distortions resulting from the presence of burrs on the tape, the puller is not pressed against the tape; the gap between it and the composition-sheet tape is 0.5-0.8 mm (Fig. 3).
When cutting parts from material with a thickness of over 0.5 mm, as a rule,
stamps with fixed puller The parts cut out in these dies are slightly inferior in flatness to those obtained in dies with a movable stripper, since the cutting occurs with sharp working edges of the punches and dies. Increasing the rigidity of the punches is achieved by reducing their length to the minimum permissible and using stepped punches. It is necessary that the punch is securely fastened in the punch holder. As a rule, the thickness of the punch holder should be at least 1/3 of the height of the punch.
Designs of working parts of dies. The designs of carbide dies largely depend on the methods of manufacturing the main form-building parts, in particular matrices. The two most common methods for processing matrices are diamond grinding and
PAGE 124
LECTURE No. 17
Shape-changing operations of sheet stamping. Crimping and distribution
Lecture outline
1. Crimping.
1.1. Basic technological parameters of crimping.
1.2. Determination of the dimensions of the initial workpiece.
1.3. Determination of the required force during crimping.
2. Distribution.
2.1. Basic technological parameters of distribution.
2.2. Determination of the dimensions of the initial workpiece.
3.3. Die designs.
1. Crimping
Crimping is an operation that reduces the cross-section of the open end of a pre-stretched hollow product or pipe.
During crimping, the open end of a hollow workpiece or pipe is pushed into the funnel-shaped working part of the matrix, which has the shape finished product or intermediate transition (Fig. 1). The ring matrix has a working cavity with a rectilinear, inclined to the axis of symmetry or curvilinear generatrix.
Figure 1 - Scheme of the crimping process
If crimping is carried out in a free state, without backpressure of the workpiece from the outside and from the inside, only its section located in the cavity of the matrix is plastically deformed, the rest of the part is elastically deformed. The necks of cylindrical cans, aerosol packaging cans, various pipeline adapters, sleeve necks, and other products are produced by crimping.
1.1. Main technological parameters of crimping
During crimping, the deformable part of the workpiece is in a volumetrically deformed and volumetrically stressed state. In the meridional and circumferential directions there are compressive deformations and compressive stresses; in the radial direction (perpendicular to the generatrix) there are tensile deformations and compressive stresses of the ring elements of the hollow workpiece. If the fate that the inner surface of a hollow workpiece during crimping is not loaded, and with a relatively thin-walled workpiece is small compared to, then we can assume that the stress state diagram will be flat - biaxial compression in the meridian and circumferential directions. As a result, some thickening of the walls occurs at the edge of the product.
The deformation during crimping is estimated by the crimping coefficient, which is the ratio of the diameter of the workpiece to the average diameter of its deformed part:
The amount of thickening can be determined by the formula:
where is the wall thickness of the workpiece, mm;
wall thickness at the edge of the product after crimping, mm;
diameter of the hollow workpiece, mm;
diameter of the finished product (after crimping), mm;
crimp ratio.
For thin materials ( 1.5 mm) diameter ratios are calculated by the outer dimensions, and for thicker ones - by the average diameters. The crimp ratios are for steel products 0.85 0.90; for brass and aluminum 0.8-0.85. Limit crimp ratio
It is considered to be one at which the workpiece begins to lose stability and form transverse folds on it. The limiting crimp coefficient depends on the type of material, the magnitude of the friction coefficient and the taper angle of the crimp matrix.
where is the yield strength of the material;
P - linear hardening modulus;
- friction coefficient; = 0,2 -0,3;
- matrix taper angle.
The optimal taper angle of the die with good lubrication and a clean workpiece surface is 12…16 , with less favorable conditions friction 20…25 .
The number of crimps can be determined by the formula:
Annealing is required between crimping operations. The dimensions of the part after crimping increase due to springing by 0.5...0.8% of the nominal dimensions.
Crimping is carried out under conditions of uneven compression in the axial and circumferential directions. At certain critical values of compressive stresses and local loss of stability of the workpiece occurs, resulting in folding.
A B C D)
Figure 2 Possible options loss of stability during crimping: a), b) formation of transverse folds; c) formation of longitudinal folds; G) plastic deformation bottom
Consequently, the critical value of the crimp coefficient is regulated by local loss of stability. To prevent the formation of folds during crimping, a straightening rod is inserted into the workpiece.
The critical crimping coefficient, the dimensional accuracy of parts obtained by crimping, significantly depends on the anisotropic properties of the workpiece material. With increasing normal anisotropy coefficient R the limiting crimp ratio increases ( K = D / d )*** K = d / D less, because at the same time, the resistance of the workpiece walls to thickening and bulging increases. The consequence of planar anisotropy during crimping is the formation of scallops at the edge section of the crimped workpiece. This requires subsequent trimming and, therefore, increased material consumption.
The angle of inclination of the forming matrix for crimping has an optimal value at which the meridional stress is minimal, at
.
If 0.1, then = 21 36 ; and if 0.05, then = 17 .
When crimping in a conical die with a central hole, the edge part of the workpiece, when transitioning from a conical to a cylindrical cavity, bends (rotates) and then, as it passes through it, again acquires cylindrical shape, that is, the edge part of the workpiece is alternately bent and straightened under the influence of bending moments. The radius of curvature of the working edge of the matrix has a significant influence on the accuracy of the diameter of the compressed part of the workpiece (figure). This is explained by the fact that the natural bending radius (edge part) of the workpiece is quite certain value, depending on the thickness, diameter of the workpiece, and the angle of inclination of the forming matrix.
= (2 sin ) .
The thickness of the edge part of the workpiece can be determined by the following formula: =; where is the base of the natural logarithm.
Figure 3 Crimping in a conical die with a central hole
If , then the workpiece element moving from the conical part of the deformation zone into the resulting cylinder loses contact with the matrix and the diameter of the cylindrical part of the compressed part or semi-finished product decreases by, that is.
If, then this phenomenon does not occur, and the diameter of the compressed part of the workpiece corresponds to the diameter of the working hole of the matrix.
From the above it follows that the radius of the matrix must satisfy next condition:
and the possible change in the diameter of the cylindrical part of the compressed part can be determined by the formula:
1.3. Determining the dimensions of the original workpiece
The height of the workpiece intended for crimping, from the condition of equality of volume, can be determined using the following formulas:
in the case of cylindrical crimping (Fig. 4a)
in the case of conical crimping (Fig. 4, b)
in the case of spherical crimping (Fig. 4, c)
0.25 (1+).
Figure 4 Scheme for determining the dimensions of the workpiece
1.4. Determination of the required force during crimping
The crimping force consists of the force required for the crimping itself in the conical part of the matrix, and the force required to bend (rotate) the crimped edge until it stops against the cylindrical belt of the die
Figure 5 Scheme for determining crimp force
Section Oa corresponds to the force required to bend the edge of the workpiece to the taper angle of the die; the whole area Ov corresponds; plot Sun corresponds to strength; plot CD corresponds to the sliding of the edge of the workpiece along the cylindrical belt of the matrix, the crimping force increases slightly.
As the workpiece exits the matrix, the force drops slightly and becomes equal to the force during a steady-state crimping process Robzh.
Strength is determined by the formula:
= 1- 1+ + 1- 1+ 3-2 cos ;
where -extrapolated yield strength equal to .
Crimping is carried out on crank and hydraulic presses. When working on crank presses, the force should be increased by 10-15
If = 0.1…0.2; That
S 4.7
This formula gives a fairly accurate calculation when 10…30 ; ,1…0.2
The approximate deforming force can be determined by the formula:
2.Dispensing operation
A distribution operation used to obtain various parts and semi-finished products that have variable cross section, allows you to increase the diameter of the edge part of a hollow cylindrical workpiece or pipe (Fig. 6).
As a result of this process, there is a decrease in the length of the generatrix of the workpiece and the wall thickness in the zone of plastic deformation, covering an area with increased transverse dimensions. Dispensing is carried out in the stamp using a conical punch, which deforms the hollow workpiece in the form of a piece of pipe, a glass obtained by drawing, or a welded ring shell, penetrating into it.
A B C)
Figure 6. - Types of parts obtained by distribution: a)
2.1. Main technological parameters of distribution
The degree of deformation in technological calculations is determined by the expansion coefficient, which is the ratio largest diameter deformed part of the product to the original diameter of the cylindrical workpiece:
The smallest thickness of the workpiece is located at the edge of the resulting part and is determined by the formula:
The greater the expansion coefficient, the greater the wall thinning.
The critical degree of deformation is regulated by one of two types of loss of stability: folding at the base of the workpiece and the appearance of a neck, leading to destruction - a crack, in one or simultaneously several sections of the edge of the deformed part of the workpiece (Fig. 7).
Figure 7 Types of loss of stability during spreading: a) folding at the base of the workpiece; b) the appearance of a neck
The appearance of one or another type of defect depends on the characteristics mechanical properties the material of the workpiece, its relative thickness, the angle of inclination of the punch generatrix, the conditions of contact friction and the conditions for securing the workpiece in the die. The most favorable angle is from 10 up to 30 .
The ratio of the largest diameter of the deformed part of the workpiece to the diameter of the original workpiece, at which local loss of stability may occur, is called the limiting expansion coefficient.
The maximum distribution ratio can be 10...15% greater than that indicated in Table 1.
In the case of an operation with heating, the workpiece can be 20...30% larger than without heating. Optimal temperature heating: for steel 08kp 580…600 WITH; brass L63 480…500 C, D16AT 400…420 C.
Table 1 Distribution coefficient values
|
Material |
At |
|||
|
0,45…0,35 |
0,32…0,28 |
|||
|
without annealing |
with annealing |
without annealing |
with annealing |
|
|
steel 10 |
1,05 |
1,15 |
||
|
aluminum |
1,25 |
1,15 |
1,20 |
|
The force of distribution can be determined by the formula:
where C coefficient depending on the distribution coefficient.
At.
2.3. Determining the dimensions of the original workpiece
The length of the workpiece is determined from the condition that the volume of the workpiece and the part are equal, and the diameter and wall thickness are assumed to be equal to the diameter and wall thickness of the cylindrical section of the part. After expansion, the conical section of the part has an uneven wall thickness, varying from to.
The longitudinal length of the workpiece can be determined using the following formulas:
- when distributing according to scheme a) (Fig. 8):
Figure 8. Scheme for calculating the initial workpiece
2. when distributing according to scheme b) if the bending radii of the workpiece when moving it onto the conical part of the punch and leaving it are equal to each other and their values correspond to:
2.4. Die designs
Structural diagram stamp for dispensing depends on the required degree of deformation. If the degree of deformation is not large and the expansion coefficient is less than the maximum, then local loss of stability is excluded. In this case, open dies are used without backpressure on a cylindrical section of the workpiece.
At high degrees of deformation, when the coefficient is greater than the limiting one, dies with a sliding support sleeve are used, which creates back pressure on the cylindrical section of the workpiece (Fig. 9).
The sliding sleeve 4 is lowered down by length-adjustable pushers 3, mounted on the upper plate 1, which eliminates the possibility of pinching the workpiece in the contact area of the punch 2, the workpiece and the sliding sleeve 4. The use of a stamp with a sliding sleeve support allows increasing the degree of deformation by 25 30% .
Figure 9 - Diagram of a stamp for dispensing with back pressure: 1-top plate; 2-punch; 3pushers; 4-sliding bushing; 5-mandrel; 6-springs; 7-plate bottom
The maximum degree of deformation during expansion with a conical punch can also be increased if a small flange with a width at the internal bending radius is obtained on the edge of the workpiece (Fig. 10). During expansion, the flange absorbs without destruction higher circumferential tensile stresses than the edge of the workpiece without a flange. In this case, the maximum degree of deformation increases by 15 20%.
Figure 10 - Scheme of distribution of a workpiece with a small flange
Distribution of blanks into dies can be done using mechanical and hydraulic presses.