KR101582916B1

KR101582916B1 - Press apparatus for preventing spring back

Info

Publication number: KR101582916B1
Application number: KR1020140083941A
Authority: KR
Inventors: 김병민; 고대철; 최홍석; 이경훈
Original assignee: 부산대학교 산학협력단
Priority date: 2014-07-04
Filing date: 2014-07-04
Publication date: 2016-01-07

Abstract

The present invention relates to a mold apparatus for preventing spring back. The present invention can prevent the springback phenomenon regardless of the mold conditions such as the radius of curvature (R), shape, and holding force of the bending part in the plate material forming process, So that the productivity can be greatly improved.
The present invention relates to a punch which is fixedly mounted on an upper mold to be elevated and operated, has the same shape as the inner shape of a molded product, and has a mounting hole formed therein through which the mounting hole is longitudinally penetrated; And a plate disposed on a die on the lower mold while being raised and lowered in conjunction with the punch in a state where the plate is installed on a mounting hole formed inside the punch and protruding from the lower end of the punch by a predetermined height? A punch interlocking pad for compression and molding; And a lower pad which is installed inside the die so as to be able to move up and down and supports a lower portion of the plate placed on the die when the punch interlocking pad is compressed and formed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a mold apparatus for preventing spring back,

The present invention relates to a mold apparatus for preventing spring back, and more particularly, to a mold apparatus for preventing spring back, and more particularly, to a mold apparatus for preventing spring back, The present invention relates to a mold apparatus for preventing springback, which is capable of improving the quality of a molded article by preventing springback phenomenon and greatly improving productivity.

Generally, when a plate material such as a steel plate is to be molded into a desired shape, the plate material is pressed on a die having a profile corresponding to the shape of the molded article under a constant pressure by a punch moving up and down, To a desired angle and shape.

In the process of forming the plate by bending the plate, the elasticity of the plate itself is completely reduced due to the difference in the thickness direction and the in-plane stress of the region subjected to the bending force even when a force less than the elastic limit or a force greater than the elastic limit is applied It is difficult to remove the spring back phenomenon that the material tries to be restored to its original state.

The above-described spring back phenomenon has a great adverse effect on dimensional accuracy (accuracy) and shape freezing property of a molded product.

Accordingly, in order to improve the dimensional accuracy, the spring back amount is predicted in advance through computer simulation, and then the angle of the mold is designed to be smaller than the angle of the actual product so that the dimension after the elastic recovery is corrected to the dimension of the product.

However, not only the amount of spring back depends on the friction condition due to the damage of the mold during the molding of the product, the curved portion (R portion) of the mold, but also the difference in the property values such as the yield point of the plate under the same mold condition It is a reality that it has a big problem in.

Accordingly, various kinds of springback reduction methods have been applied in the field, and a representative method of reducing the springback is to coin the corner portions as shown in the following FIG. 1.

Figure 1. Coining method for springback reduction

The above coining technique refers to a press working method in which a metal plate material is compressed by a pair of upper and lower molds having concave and convex portions and is taken on a material. The corner portion of the molded product is locally formed by a punch having fine protrusions. It is known that the difference in stress in the thickness direction is reduced and the amount of spring back is reduced.

However, it is very difficult to perform locally plastic deformation of the plate material through the coining process for the corners, and the size of such protrusions is very limited in terms of molding load, which makes it difficult to apply the plate.

In addition, it is not only difficult to manufacture fine molds on the mold for coining, but also problems in that it is disadvantageous from the viewpoint of maintenance since the stress is concentrated on the protrusions during molding and the damage such as breakage is large. .

On the other hand, as another method of reducing the spring bag, a technique for controlling the stress state of the corner portion, which causes the spring back by controlling the pad load, has been proposed, as shown in Fig.

Figure 2. Spring Backlash by Pad Load

However, in the control technology of the pad load described above, there are problems in that it is difficult to apply the pad load because a lot of trial and error is generated in order to find the pad load at which the spring back becomes zero according to various conditions such as the product, mold shape, structure, material strength,

In addition, a variety of techniques have been developed to prevent springback during sheet metal forming. For example, Korean Patent Registration No. 10-0952000 (name: a mold for preventing springback, Quot;).

As shown in FIG. 1, the prior art 1 includes a steel which is mounted on a top mold and moves up and down according to a vertical movement of the upper mold; A pad mounted on the steel so as to move up and down according to the ascending and descending operations of the steel and move downward to fix the panel; A movable steel rotatably mounted at both ends of the steel and rotationally molding the panel into a desired shape; A cam mounted on an inner side of the elastic member and movably mounted on the lower mold; And an upper type drive which is mounted on both sides of the upper mold and is moved up and down according to the up and down motion of the upper mold and advances the cam by the lowering operation.

The prior art 1 described above has a problem in that it is molded while rotating around the folded portion of the panel, but has a relatively complicated structure.

As another example of the technique for preventing the springback, there is proposed a technique disclosed in Korean Patent Laid-Open Publication No. 10-2006-0110929 (name: a press device having a springback prevention function, hereinafter referred to as "Prior Art 2") .

2, the prior art 2 includes a main body 22 fixed to the cam slide 10 and configured to have a shape corresponding to one side of the lower mold, A driven piston (42) which is fitted in the upper part of the hollow part (24) and which is moved up and down; a hollow piston part (42) fitted in the lower end part of the hollow part (24) A top plate 30 provided on the upper end of the main body 22 so as to be movable in the vertical direction by the driven piston 42 and a drive piston 52 formed to extend toward the lower side, And a cam steel portion 20 composed of a plunger 54 connected to the plunger 54 '.

In the prior art 2, when the panel is bent, a force directed from the lower part to the upper part is applied so that the bending part of the panel is restrained by the residual stress to the utmost, but the structure of the punch itself is not improved, There is a problem that the structure is relatively complicated.

As another example of the technique for preventing the springback, a technique disclosed in Korean Patent Laid-Open Publication No. 10-2002-0066441 (hereinafter referred to as " Prior Art 3 " .

3, in the prior art 3, a coolant pipe for cooling a punch which is in contact with one side of a workpiece is installed in a punch and a heater for heating a die in contact with the other side of the workpiece is installed on the die Is to make the point of its technical composition.

In the prior art 3, bending is performed in a state where a temperature difference is generated on both surfaces of the work.

Korean Registered Patent Publication No. 10-0952000, "Mold for preventing springback ". Korean Patent Laid-Open Publication No. 10-2006-0110929, "Pressing device having springback prevention function ". Korean Patent Laid-Open Publication No. 10-2002-0066441, "Press device for reducing springback ".

SUMMARY OF THE INVENTION The present invention has been made in order to solve such conventional problems and it is an object of the present invention to provide a method of manufacturing a plate material which is capable of preventing springback phenomenon irrespective of mold conditions such as radius of curvature (R), shape, And to provide a mold apparatus for preventing a new spring back.

Another object of the present invention is to provide a mold apparatus for preventing a spring back, which can improve the quality of a molded article and can greatly improve productivity.

In order to attain the above object, the present invention provides a method of manufacturing an injection molding machine, which is fixed and installed on an upper mold to be elevated and operated, has the same shape as the inner shape of a molded product, A punch formed into a body; And a plate disposed on a die on the lower mold while being raised and lowered in conjunction with the punch in a state where the plate is installed on a mounting hole formed inside the punch and protruding from the lower end of the punch by a predetermined height? A punch interlocking pad for compression and molding; And a lower pad which is installed inside the die so as to be able to move up and down and supports the lower portion of the plate placed on the die during the compression molding of the punch interlocking pad.

In the present invention, the lower edge portion of the punch has a curved surface formed with the same radius of curvature as the inner edge portion of the bent portion of the plate material to be molded.

In the present invention, the punch interlocking pad may include a pressing part installed inside the mounting hole on the punch and having a curved corner at the lower end thereof; A support portion which is inserted into and extends from a lower portion of a mounting hole formed inside the punch to a space corresponding to an upper side of the latching jaw in a state of integrally extending vertically upward from an upper surface of the pressing portion; A release preventing plate detachably coupled to an upper end of the support portion and hooked on a latching protrusion formed on an operating hole of the punch; And a spring which is fitted around the outer periphery of the support portion and is provided inside the mounting hole between the upper surface of the pressing portion and the engaging jaw, and which exerts an elastic force such that the pressing portion always protrudes outward from the lower end of the punch.

In the present invention, the lower pad includes a plate supporting plate for supporting a lower portion of the plate placed on the die in a state where the lower pad is installed inside the die; A support rod fixedly coupled to a center of a bottom surface of the plate material support plate and penetrating a bottom surface of the die to be fitted into the lower mold; And a spring that applies an elastic force so that the plate member support plate is always positioned on the upper portion of the die while being fitted around the outer periphery of the support rod.

In the present invention, a seating groove is formed in an inner bottom surface of the die to receive a plate-material support plate constituting a lower pad when the punch and the punch interlocking pad are lowered, and a guide groove The ball has a feature that is formed.

According to the present invention, the punch interlocking pad is provided so as to protrude by a predetermined height from the lower end of the punch to perform primary compression molding by the punch interlocking pad during compression molding of the plate material, And secondary compression molding is performed by the lower end edge portion of the punch with respect to the bent portion of the plate material, regardless of the mold condition such as the radius of curvature R of the bending portion, the shape and the holding force, (Springback) phenomenon can be effectively prevented.

In addition, even if there is a change in the shape of the mold (R portion) and the scattering of the material, a uniform degree of dimension can be ensured, and therefore, the quality of the product is greatly improved.

1 is a cross-sectional view showing the prior art 1.
2 is a sectional view showing the prior art 2. Fig.
3 is a cross-sectional view showing the prior art 3.
4 is an enlarged sectional view showing a mold apparatus for preventing spring back according to the present invention.
5 is a cross-sectional view showing an initial state in which a plate material is formed by using a mold apparatus for preventing spring back according to the present invention.
6 is a cross-sectional view showing a primary compression / molding operation by a punch interlocking pad when a plate material is formed by using a mold apparatus for preventing spring back according to the present invention.
7 is a sectional view showing a secondary compression and molding operation of the punch with respect to the bent portion of the plate material when the plate material is formed by using the mold apparatus for preventing spring back according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 4, the mold apparatus 10 for preventing spring back according to the present invention is fixedly installed on an upper mold 11 which is raised and lowered, has the same shape as the inner shape of a molded product, A punch 20 is provided in which a mounting hole 13 partitioned by a latching jaw 12 is formed to penetrate in the longitudinal direction.

The mounting hole 13 formed in the punch 20 is coupled to the punch 20 in a state of being protruded outside the lower end portion of the punch 20 by a predetermined height H, A punch interlocking pad 30 for primarily compressing and molding the sheet material 16 placed on the die 15 on the lower mold 14 is provided.

The punch interlocking pad 30 has a lower pad 40 for supporting the lower portion of the plate 16 placed on the die 15 when the punch interlocking pad 30 compresses and molds the inside 16 of the die 15 So as to be able to be lifted and lowered.

The lower edge of the punch 20 is curved to have the same curvature radius as the inner edge of the bent portion 16a of the plate 16 to be formed.

In order to form the punch interlocking pad 30 in the present invention, a pressing portion 31 having a curved corner at the lower end is provided in the mounting hole 13 on the punch 20, and the pressing portion 31 The support portion 32 is inserted vertically upward from the upper surface of the punch 20 into a space corresponding to the upper side of the engaging jaw 12 from the lower side of the mounting hole 13 formed in the inside of the punch 20 Respectively.

A detachment prevention plate 33 is detachably coupled to an upper end of the support portion 32 so as to be caught by the retaining protrusion 12 formed in the operation hole 13 on the punch 20 and not to be pushed downward.

In the outer periphery of the support portion 32, a spring S for giving an elastic force is inserted so that the pushing portion 31 always protrudes outward from the lower end of the punch 20, And the engaging jaw (12).

In order to construct the lower pad 40 according to the present invention, a plate member support plate 41 for supporting a lower portion of the plate member 16 is provided in the die 15, A support rod 42 inserted through the bottom surface of the die 15 and fitted into the lower mold 14 is fixedly coupled to the center.

A spring S for applying an elastic force is disposed on the outer periphery of the support rod 42 such that the plate support plate 41 is always positioned on the upper side of the die 15.

The punch 20 and the punch interlocking pad 30 are lowered to the inner bottom surface of the die 15 so that the sheet material support plate 41 constituting the lower pad 40 is compressed And a guide hole 44 for guiding the lifting and lowering of the support rod 42 is formed at the center of the seating groove 43.

The operation of the present invention is as follows.

5, when the plate member 16 is to be formed by using the mold apparatus 10 for preventing spring back according to the present invention, the plate member 16 is fixed to the lower mold 14 The lower portion of the plate 16 is supported by the plate member support plate 41 on the lower pad 40 which is always raised upward inside the die 15 when the plate member 16 is placed on the upper surface of the die 15 State.

6, the entire punch 20 is lowered to the inside of the die 15, and at the same time, the punch 20 is moved to the outside of the lower end of the punch 20 at a constant height? The pressing portion 31 on the punch interlocking pad 30 protruded by the plate supporting plate 41 is lowered and the plate 16 supported by the plate supporting plate 41 is primarily compressed and formed.

The plate member 16 is primarily compressed and molded by the pressing portion 31 on the punch interlocking pad 30 and the plate member support plate 41 reaches the bottom dead point and is accommodated in the seating groove 43 7, since the lowering of the pressing portion 31 on the punch interlocking pad 30 is no longer carried out, the lowering of the punch 20 is performed by? H, The pressing portion 31 on the pad 30 is raised above the mounting hole 13 in the punch 20 while compressing the spring S. [

At the same time, the curved portion on the outer side of the lower end of the punch 20 is secondarily compressed and formed with respect to the bent portion 16a of the plate member 16.

When the punch 20 is lifted from the die 15 in accordance with the upward movement of the upper mold 11, the pressing portion 31 constituting the punch interlocking pad 30 is pushed by the restoring force of the spring S 20).

The plate member support plate 41 constituting the lower pad 40 also rises to the upper portion of the die 15 while supporting the lower portion of another plate member 16 while releasing the molded product by the restoring force of the spring S .

When the curved portion on the outer side of the lower end of the punch 20 is secondarily compressed and formed with respect to the bending portion 16a on the plate member 16, the bending portion 16a in the compression- The deformation effect is generated, so that the stress deviation of the elements causing spring back and spring go is reduced.

Bending was performed on each of the plate materials using a mold apparatus 10 for preventing springback according to the present invention, a general molding apparatus having no lower pad and a general molding apparatus having a lower pad, and then the springback amount was measured , And the results are shown in Fig.

Figure 3. Spring backlash by molding method

As can be seen from FIG. 3, in the case of a general molding apparatus without a lower pad, excessive compressive stress acts on the inner side of the bending portion during the pressing process when the excessive deflection generated during the molding process is excessive, ) Phenomenon occurred.

Also, in the case of a general molding apparatus having a lower pad, an excessive springback phenomenon occurs because the stress state inside / outside the corner portion is necessarily compression-tensioned.

In contrast, in the mold apparatus for preventing spring-back according to the present invention (denoted as "development process" in FIG. 3), the compression-tensile stress state of the bending portion is appropriately resolved, .

10: Mold device for preventing springback
11: Upper mold
12: hanging jaw 13: mounting ball
14: Lower mold 15: Die
16: plate member 16a: bent portion
20: Punch 30: Punch interlocking pad
31: pressing portion 32:
33: separation prevention plate 40: lower pad
41: plate receiving plate 42: supporting rod
43: seat 44: guide
S: Spring.

Claims

A mounting hole 13 which is partitioned by a latching jaw 12 is inserted in the longitudinal direction so as to be inserted into the upper mold 11, A formed punch 20;
The punch 20 is installed in a mounting hole 13 formed inside the punch 20 and moves up and down with the punch 20 in a state where the punch 20 is protruded from the lower end of the punch 20 by a predetermined height H, A punch interlocking pad 30 for primarily compressing and molding the plate material 16 placed on the die 15 on the die 14;
And a lower pad 40 which is installed in the die 15 so as to be able to move up and down and supports a lower portion of the plate 16 placed on the die 15 when the punch 30 is compressed and formed, ,
The lower edge of the punch 20 is curved to have the same radius of curvature as the inner edge of the bent portion 16a of the plate 16 to be molded,
The punch interlocking pad 30 is provided inside the mounting hole 13 on the punch 20 and has a pressing portion 31 whose lower end has a curved surface. Is inserted into a space corresponding to the upper side of the engaging jaw 12 from the lower side of the mounting hole 13 formed in the inside of the punch 20 while being integrally extended vertically upward from the upper surface of the pressing portion 31 (32); A separation preventing plate 33 detachably attached to the upper end of the support portion 32 and hooked on the upper portion of the engagement protrusion 12; The pressing portion 31 is always inserted in the mounting hole 13 between the upper surface of the pressing portion 31 and the engaging protrusion 12, And a spring S for applying an elastic force so as to protrude outward from the lower end of the main body 20,
The lower pad 40 includes a plate support plate 41 for supporting a lower portion of the plate 16 placed on the die 15 in a state that the lower pad 40 is installed inside the die 15; A support rod 42 fixedly connected to the center of the bottom surface of the plate material support plate 41 and inserted into the lower mold 14 through a bottom surface of the die 15; A spring S for applying an elastic force such that the plate-material support plate 41 is always positioned on the upper side of the die 15 in a state of being fitted around the outer periphery of the support rod 42; When the plate material support plate 41 constituting the lower pad 40 reaches the bottom dead point by the lowering operation of the punch 20 and the punch interlocking pad 30, A seating groove 43 for receiving the support plate 41; Wherein a guide hole (44) for guiding the lifting operation of the support rod (42) is formed at the center of the seating groove (43).

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