RU2684130C1 - Forming method of elastic medium sheet components with elements of “undercutting” type - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to metal forming and enables to obtain any sheet parts with "undercutting" on boards without defect "under-forming". Creating a virtual model of a movable rigging element by empirical selection in accordance with the required "undercutting" parameters. Movable element and a riser block with an inclined slot are made for the said movable tool element in accordance with the selected virtual model of the movable rigging element. Sheet billet is placed on the tooling installed on the riser block. Preforming the workpiece is performed. Further, the movable clamp is installed in the inclined slot provided for it and definite forming element of "undercutting" type by means of movable rigging element, on which elastic medium acts with provision of conditions close to all-round compression.EFFECT: defect "under-forming" on part boards is eliminated.1 cl, 16 dwg

Description

The invention relates to the field of metal forming and allows you to get rid of defects such as "under-stamping" during shaping by elastic medium of sheet parts with elements of the type "undercut".

There are options for joining sheet metal parts during assembly: overlapping and butt to back. The lap joint is simpler in design, has a lower mass and greater rigidity with respect to the butt joint with the patch. The disadvantage of the design using the lap joint is the need to form a hook. The length of the overlap is determined from the conditions for placing the number of fasteners required by the condition of strength. When forming a hook on the side surface of a part on existing equipment, the pressure of the elastic medium is not enough, as a result of which a defect of the type “under-stamping” arises. The butt-to-pad connection is more convenient to manufacture, but requires the manufacture of an additional part (cover) and has a large mass. Therefore, in aircraft construction, in most cases, the type of connection of parts with each other overlap is used, in connection with which there are so many “hooks” in sheet parts.

An advantageous field of use of the invention is aircraft construction.

In the field of aircraft construction, the issue of the production of sheet parts with elements of "cutting" is an acute issue. To eliminate defects "under-stamping" is used manual fine-tuning of parts with great complexity. As a result of fine-tuning the part in one place, the contour of the entire part leaves and, as a result, you have to finish the entire part. Also, with manual debugging, the meaning of accounting for springing in a snap is lost, since. when fine-tuning, the part in the area of the sweep completely copies the form from the snap-in with nominal dimensions.

The proposed method of eliminating the "under-stamping" on the details allows you to get a hook without a defect, and, in practice, eliminate manual finishing work.

Most often today in aircraft construction they use the method of forming sheet parts with an elastic medium. This is due to:

• exceptionally high productivity (the stamping cycle does not require a complex and lengthy change of the die and punch when changing parts);

• minimal costs for the stamping tool (one of the parts of the equipment does not need to be made, since the elastic medium acts in its role);

• achieving the best mechanical properties of the manufactured parts (the action of an elastic medium has a more gentle effect on the surface of the part than the effect of a metal tool);

• unlimited possibilities in terms of mechanization and automation of production (there is the possibility of using various auxiliary equipment accessories, either changing the stress-strain state of the workpiece, or acting on it, transmitting the force created by the elastic medium).

However, the use of this technology of shaping without additional snap-in elements does not allow obtaining a “hook” on a sheet metal part without the “under-stamping” defect.

A known method of forming elastic medium of sheet parts (RU 2124411 C1; IPC B21D 22/10; published on 01/10/1999). Using this method, you can get a “hook” on a sheet part, but not eliminate the defect “understamping”. Similar technologies that allow you to get a “hook” are described in the patents:

• RU 2089313 C1, IPC B21D 22/10, published on 09/10/1997;

• RU 2064355 C1, IPC B21D 22/10, published on July 27, 1996;

• RU 2232659 C2, IPC B21D 22/10, published July 20, 2004.

The technology proposed in patent RU 2124411 C1; IPC B21D 22/10, describes a device and technology for stamping with an elastic medium, in which an elastic lining and a supporting washer are used as elements that help stabilize the process and distribute the forming forces in the desired zones when lowering the container with the elastic matrix down and shaping. Since the support washer is on top, at the beginning the forming force is concentrated on the radius transitions, which are the most problem areas. The farther the base plate goes down, the larger the impact area becomes. Forming occurs with constant contact of the entire workpiece with an elastic medium, which provides increased forming force throughout the workpiece.

Signs that coincide with the proposed technology: shaping using an elastic medium and the use of additional devices for shaping.

However, in relation to the shaping of hooks, the technology used in the analogue cannot provide the desired result (eliminate the "under-stamping"). The material acting on the metal is an elastic medium, but it cannot provide sufficient force to eliminate the “understacking” defect. Even the use of a support washer and an elastic lining that concentrates the forming forces on the radial transitions (the "undercut" zone) in the initial stages of shaping and support them on the entire surface of the workpiece during the process, do not provide sufficient shaping effects. This is due to the fact that when shaping with an elastic medium, the stress-strain state necessary for hooking is not created.

A condition for the shaping of hooks without a defect of the “under-stamping” type is a condition close to full compression. This condition can be ensured by the use of an additional snap-in element recommended in the proposed technology.

The technology proposed in patent RU 2089313 C1, IPC B21D 22/10, describes a device and technology for stamping with an elastic medium, which uses supports from an elastic medium that meet the impact before the workpiece. Due to this, a change in the formation pattern and an increase in the forming effect in the area of backwater are achieved. This technology allows you to get parts having symmetrically located sides.

Signs that coincide with the proposed technology: shaping using an elastic medium and the use of additional devices for shaping.

However, during the shaping of hooks, this technology cannot provide the desired result (eliminate "under-stamping"), due to the fact that it cannot provide a sufficient form-forming effect to eliminate the "under-stamping" defect, and does not create a stress-strain state necessary for hooking. For the formation of hooks without a defect of the type "under-stamping", a state close to full compression is necessary. This condition can be ensured by the use of an additional snap-in element recommended in the proposed technology.

The technology proposed in patent RU 2064355 C1, IPC B21D 22/10, describes a block and technology for stamping parts with an elastic medium. This technology uses an elastic pillow as a forming element. This technology is implemented due to the smaller volume of the elastic pad inserted into the press than in conventional presses with an elastic medium, which reduces the required efforts for shaping (the height of the elastic pad is equal to the sum of the heights of the interchangeable equipment and the workpiece). However, this leads to a limitation in the developed pressure of the press, since the shaping ability of an elastic cushion of such a height, not pressed into the block, reduces the capabilities of the press. Such a technology is justified for experimental installations where it is necessary to develop small forming pressures with the relative simplicity of design solutions.

The main feature that coincides with the proposed technology is the shaping using an elastic medium.

With regard to the shaping of hooks, this technology cannot provide the desired result (eliminate "under-stamping"). Even the classical schemes of shaping by an elastic medium, where the thickness and volume of the elastic cushion significantly exceed the dimensions of the tooling and the workpiece, cannot develop sufficient effort to eliminate the "under-stamping" defect on the hook. This technology has even lower performance in terms of shape-forming ability and, therefore, also cannot ensure the elimination of the “under-stamping” defect on a hook.

A condition for the shaping of hooks without a defect of the “under-stamping” type is a condition close to comprehensive compression, which can be achieved by using an additional snap-in element, as recommended in the proposed technology. The technology proposed in patent RU 2064355 C1, IPC B21D 22/10 cannot implement such conditions.

The technology proposed in patent RU 2232659 C2, IPC B21D 22/10, describes a device for cutting and stamping technology with an elastic medium, which uses the effect of a sharp increase in pressure after cutting and its redistribution to the entire surface of the part evenly. Thanks to this effect, parts with curved sides can be shaped. Also, for greater effect in the technology, fluoroplastic liners are used, on which the workpiece slides after trimming, which allows increasing pressure on the radius transition zone.

Signs that coincide with the proposed technology: shaping using an elastic medium and the use of additional devices for shaping.

With regard to the shaping of hooks, this technology cannot provide the desired result (eliminate "under-stamping").

An elastic medium acts on the metal of the workpiece, but it cannot provide sufficient form-forming force to eliminate the “under-stamping” defect even taking into account the fact that during cutting there is a sharp increase in pressure and the liners provide maximum force on the radius transition (“under-stamping” zone). This is due to the fact that during shaping by an elastic medium, the stress-strain state necessary for the formation of a hook is not realized.

A condition for the formation of hooks without a defect of the type of "under-stamping" is a state close to full compression. This condition can be ensured by the use of an additional snap-in element, as recommended in the proposed technology.

None of the listed technologies (RU 2124411 C1; IPC B21D 22/10; RU 2089313 C1, IPC B21D 22/10; RU 2064355 C1, IPC B21D 22/10; RU 2232659 C2, IPC B21D 22/10) allows obtaining " hacking ”without the“ under-stamping ”defect. This defect also occurs on modern equipment with high pressure (100 MPa or more).

Unstamping occurs due to the occurrence of excessive stiffness in the region of the “hook” top during shaping by an elastic medium. This effect is due to the geometric shape of the “hook”. To overcome excessive rigidity in the region of the top of the hook, it is necessary to transfer the force of the elastic medium to an additional tooling element, which will transmit the increased force locally to the top of the hook and provide in it a condition of a stress-strain state close to full compression.

The maximum effect of the additional tooling element can be obtained by carrying out its movement during shaping. Based on this, the closest analogues of the proposed technology were selected.

A known method of forming rectangular box-shaped parts (SU 1530295 A1; IPC B21D 22/02; published December 23, 1989), according to which a rectangular box-shaped part is obtained due to two movable mutually perpendicular parts of the machine.

Signs of an analogue that coincide with the features of the claimed invention are: obtaining elements of a sheet part due to movable tooling elements; the use of movable rigid snap-in elements eliminates defects and improves the quality of the part.

In contrast to the claimed invention, the analog uses the force of the springs, transmitting the forming action to the workpiece, using two independent mutually moving movements.

The disadvantages of this method are: used two independent mutually moving movements; only applicable to box-type parts; the need to manufacture the device individually for each detail.

As a result of using this scheme, it is impossible to eliminate the “under-stamping” defect and obtain the “undercut” element, since the action is carried out sequentially in different directions through the springs, which does not allow for uniform distribution of the shaping effects and repeatability of the results with repeated shaping, which is a significant minus compared with the proposed scheme.

A known method of manufacturing parts using a stamp with movable upper tools (SU 1792770 A1; IPC B21D 22/02; published 02/07/1993), according to which a sheet blank is formed using the vertical movement of the punch and the rotary movements of two moving tool elements driven by the punch . As a result, the more the punch goes down, the more the movable elements act on the workpiece.

Signs of an analogue that coincide with the features of the claimed invention are: obtaining elements of a sheet part due to movable tooling elements; the use of movable rigid snap-in elements eliminates defects and improves the quality of the part; use as a drive the movement of the main forming element (matrix or punch).

Unlike the claimed invention, the analog uses the force of the punch, which sets in motion the moving tooling elements acting on the workpiece; the rotational movement of the movable elements is used to ensure shaping.

The disadvantages of this method are: the possibility of jamming of the movable elements in the final position; the need to use a specific pair of driving punch and moving elements; the need for massive guides.

When using an analog circuit, there are a number of disadvantages compared with the invention: it is impossible to eliminate the “under-stamping” and get a “hook”, since there is a risk of a lack of effort during shaping and jamming of the forming rotary parts (due to the fact that the impact occurs as a result of rotation moving parts); even with sufficient force in the “sweep” area, there will be a significant decrease in turning speed, which will lead to impulse movements and fatal defects during shaping.

The known method is similar in technical essence and the achieved result to the proposed invention, which is adopted as a prototype — a method of forming using a bending stamp (description of the invention to patent RU 117331; IPC B21D 5/06; published on June 27, 2012). The stamp contains a matrix and a punch with three movable elements with springs. When moving the plunger down, the springs provide a force of impact and pressure. Side effects are provided by pins passing through the springs.

Signs of the prototype, coinciding with the features of the claimed invention: the receipt of the elements of the sheet parts due to the movable elements of the snap; the use of movable rigid snap-in elements eliminates defects and improves the quality of the part; the use of movement of the main forming element (matrix or punch) as a drive; the ability to drive from an elastic medium.

The disadvantages of this method are as follows: a complex transfer of force from the vertical movement of the tool to the movable elements (by means of springs); three movable elements acting on different zones; unreliability of the transmission of force on the lateral movable elements (pins with springs); the possibility of a defect in contact with the sharp part of the lateral movable element with the workpiece; lateral movable elements act in such a way that it is difficult to form “hooks”.

As a result of using the prototype scheme, it is possible to eliminate the "under-stamping" and get a "hook", since the force action is at an angle to the deformation zone. However, a significant drawback is that the impact occurs in three different zones by different moving elements. This does not provide comprehensive compression as in the case of the proposed technology. Also, during shaping, zones with high friction can occur in the area of influence of the lateral movable elements, which can lead to the formation of scoring on the surface of the part during shaping. These disadvantages of the prototype method do not allow to achieve a technical result.

The claimed invention is directed to obtaining parts from a sheet with the elements of "hooking" without defects "under-stamping". Its technical result consists in obtaining a “hook” without the “under-stamping” defect by using an element driven by an elastic medium and providing the necessary state close to full compression.

The technical result is achieved by the fact that the method of shaping by elastic medium sheet metal parts with elements of the “hook” type, including creating a virtual model of the moving tooling element by empirical selection in accordance with the required parameters of “hooking”, manufacturing a movable element and a sub-die plate with an inclined groove for the specified movable snap-in element in accordance with the selected virtual model of the movable element, placement of sheet blanks on snap-in mounted on a sub-die the plate, preliminary shaping of the workpiece, installing a movable clamp in the inclined groove provided for it, and final shaping to obtain an element of the “sweep” type, which is carried out by means of a movable element that is exposed to an elastic medium with conditions close to comprehensive.

According to the invention, before forming, a snap is installed on the press table, mounted on a punch plate with a groove for installing the movable element, a workpiece is installed on the tool pins, after which preliminary shaping is carried out, then a movable element is installed on the punch plate in the grooves and final shaping is performed, which provides high-quality receipt of parts with a hook.

The elastic medium acts on the inclined surface of the element and sets it in motion along the inclined surface of the groove in the sub-die plate. The movement of the movable element during the final molding provides the necessary stress-strain state of compression and a sufficient force effect on the deformable zone of the part to avoid "under-stamping".

The method is as follows:

- a sub-die plate is installed on the press table with a groove for the movable element and positioning pins for installing the forming tool;

- the forming equipment is installed on the positioning pins;

- on the sheet blank is applied lubricant type TsIATIM;

- the workpiece is mounted on the base pins;

- pre-molding with an elastic medium without a movable element;

- CIATIM type grease is applied and a “Sevilen” type film is placed on the inclined surface of the die plate (after preliminary molding and receiving a “hook” with the “under-stamping” defect);

- a movable element is installed on the inclined surface of the groove in the sub-stamp plate;

- the final molding is performed.

As a result of the final molding, the defect in the “sweep” area is eliminated due to the movement of the movable element during the transfer of force from the elastic medium.

The presence of distinctive features from the prototype allows us to conclude that the proposed method meets the criterion of "novelty."

The use of an elastic medium as a driving device for a movable element avoids the manufacture of additional devices for different parts, it is enough to make a sub-stamp plate and a movable element of a certain size.

The use, calculated by empirical selection in accordance with the required parameters of "hooking", of the geometric shape of the surface of the movable element in contact with the elastic medium, provides the necessary transfer of force due to the inclined surface.

To ensure the regulation of the forming force, this element can be made precast.

Only one movable element is used, providing a forming force on the deformable zone. There is no difficulty in linking the movement of several moving elements.

There is a possibility of forming flat sides with a small forming pressure of an elastic medium or low side height.

By changing and selecting the geometric shape of the movable element, an increased force effect on the part can be achieved.

The use of smooth contours of the movable element in the area of contact with the workpiece eliminates damage to the surface of the workpiece.

The use of a movable element moving along the inclined surface of the die plate creates the conditions for comprehensive compression in the deformable zone of the part with a “hook” (the zone of occurrence of the “under-stamp” defect). The condition of comprehensive compression in the problem area is the only way to eliminate “under-stamping” during shaping.

The use of TsIATIM type grease and “Sevilen” type film on the inclined surface of the die plate eliminates jamming of the movable element and ensures its movement when exposed to an elastic medium.

The invention is illustrated by drawings, where:

• FIG. 1 - Installation of a sub-stamp plate with an inclined groove for the movable element and positioning pins for installing the forming tool on the sub-stamp plate;

• FIG. 2 - Installation of forming equipment on the positioning pins;

• FIG. 3 - Installation of the workpiece on the base pins;

• FIG. 4 - The position of the elements of the snap and workpiece before preliminary shaping;

• FIG. 5 and 6 — Location of the “under-stamping” defect after preliminary shaping (Fig. 6 shows the physical picture of the “under-stamping” distribution (white color));

• FIG. 7 - Installation of the movable element on the inclined surface of the groove in podshtampovoy plate;

• FIG. 8 - Section plane;

• Fig. 8 a (sectional view) - Installation of a movable element in a working position before final shaping;

• FIG. 9 (in a section) - The position of the elements before the final shaping;

• FIG. 10 (in a section) - Places of influence of an elastic medium on a movable element and the main vector of forming forces;

• FIG. 11 - Location of the defect "under-stamping" after the final shaping with a movable element (the defect is eliminated);

• FIG. 12 - Computer model of a part created in CAD (Computer-Aided Design) system NX 10;

• FIG. 13 - Finite-element model of a sheet blank (initial moment of modeling);

• FIG. 14 - Finite-element model of the molded part (the final moment of modeling);

• FIG. 15 - Detail obtained during the full-scale experiment.

• FIG. 16 - CIMCORE 75xxSE CMM complete with ScanWorks V5 scanner

The elements of the device designed to implement the claimed method of forming “hooks” on sheet parts with an elastic medium are assigned the following digital designations (see Fig. 1 and Fig. 2):

1 - press table;

2 - pins positioning the snap;

3 - sub-stamp plate;

4 - equipment for shaping;

5 - blank;

6 - movable element;

The method of the invention is carried out in the following sequence:

1) a virtual model of the movable element is created (6) by empirical selection of the model in accordance with the required parameters of "hooking" after shaping;

2) a movable element (6) and a sub-stamp plate (3) are manufactured on a machine with numerical control;

3) a sub-die plate (3) is installed on the press table and equipment (4) on it;

4) CIATIM type grease is applied to the sheet blank (5);

5) the workpiece (5) is installed through the pin holes on the snap studs;

6) preform is formed (5) without a movable element in advance;

7) CIATIM type grease is applied and a “Sevilen” type film is placed on the inclined surface of the die plate (3) (after preliminary molding and receiving a “hook” with a “non-stamping” defect);

8) a movable element (6) is mounted on a sub-stamp plate (3);

9) the part is finally formed.

As a result of the final molding, the defect in the “sweep” area is eliminated due to the transfer of force from the elastic medium through the movable element (6).

An example of the implementation of the method of shaping "hooking" using a movable element is considered on the example of the shaping of parts made of aluminum alloy 1163AM. In CAD (Computer-Aided Design) system NX 10 a computer electronic model of the part was created (Fig. 12). Further, in the CAE (Computer-aided engineering) PAM-STAMP system of the French company ESI Group, the unfolding process was simulated to obtain a workpiece (see Fig. 13) and shaping a sheet part (see Fig. 14). In numerical modeling, the finite element method and the implicit solution method were used. As a result of the calculation, the receipt with the use of the movable element of the part without the “under-stamping” defect is confirmed (Fig. 11, Fig. 13).

Based on the simulation results, a full-scale experiment was conducted on the Flexform QFC 1.2x3 - 1000 press from AVURE. The sub-die plate, tooling for forming and the movable element were made of plastic of the NECURON type.

As a result of shaping at a pressure of 80 MPa according to the scheme of the workpiece with a thickness of 2 mm, according to the technology described previously using a movable element, a part was obtained (Fig. 15).

In order to determine the magnitude of "understacking" after shaping, the part was measured using a volumetric scanning software and hardware complex (Fig. 16), which includes:

1) the hardware of the complex:

- coordinate measuring machine Hexagon Technology CIMCORE 7520SE;

- volume optical scanner Perceptron Scan Works V5 (hereinafter referred to as the scanner);

- PC based on x86-64 / EMT64 architecture.

2) the software part of the complex:

- Windows x64;

- RDS - complete KIM software;

- Scan Works 5.5 - complete scanner software.

As a result of measurements, the amount of under-stamping was 0.08 mm, which fits into the tolerance.

The experiment confirmed the efficiency of the proposed technology.

Claims (1)

The method of forming sheet parts with elements of the “hook” type using an elastic medium, including creating a virtual model of the moving tooling element by empirical selection in accordance with the required “hooking” parameters, manufacturing a moving element and a die plate with an inclined groove for the specified moving tooling element in accordance with the selected virtual model of a movable element, placement of a sheet blank on a tool installed on a sub-stamp plate, preliminary shaping for preparation, installation of the movable clamp in the inclined groove provided for it and the final shaping with the receipt of the element of type "hooking", which is carried out by means of a movable element, which is affected by an elastic medium, providing conditions close to comprehensive compression.

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