JP2002321022A - Method for precise blanking in metal press working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve yield, operational efficiency, and cost requirements in a compression shearing method by avoiding defects resulted from a wedge- shaped protrusion for providing a hydrostatic pressure. SOLUTION: In a conventional metal press where a punch 2 is disposed in a lower mold 22, when a metallic material 3 is blanked with the punch 2 and a die 26. The material 3 is previously formed into a little larger diameter than the diameter of the blanking hole of the die 26 by a cutting allowance. And the material 3 is supported and blanked by sandwiching between the punch 2 and an ejector 29 disposed in the blanking hole of the die 26, while restraining the flow in the direction that the material 3 escapes with a material restraining plate 30 attached in the upper mold 26. Consequently a product and a scrap are dropped into the lower mold 22 with the ejector 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision punching method (obtaining only a sheared surface without a fractured surface) in metal stamping with a general press, and more particularly to a wedge-shaped projection for applying hydrostatic pressure. The present invention relates to a precision punching method which is improved in cost, yield, and operability in a compression shearing method which avoids the drawbacks described above.

[0002]

2. Description of the Related Art As shown in FIG. 4, in finish punching in a metal press using a general press, a clearance (gap) between a female die 1 and a punch 2 is extremely small (0.
01 to 0.02 mm), and further, a method is adopted in which the cutting edge of the female mold 1 of the mold is rounded and removed. In the figure, 3 is the material, 4
Indicates a product.

[0003] However, the removed product 4 has large burrs and who.

[0004] As a processing method for eliminating the above-mentioned burr and drool generated by the normal punching, a blank 5 whose outer dimension is larger by 20% than a finished dimension as shown in FIG. There is a construction method in which the portion 5a of the fractured surface of the punched side surface is scraped off again without the clearance (gap) of No. 1.

The precision blanking method (fine blanking) eliminates all of the disadvantages, fracture surfaces and burrs without the interposition of a blank.

That is, in the conventional punching process, the blade portion begins to bend by the action of a tensile force acting on the surface of the material (the occurrence of drooping). When the stroke advances to reach the breaking stress, cracks are generated and gradually tear, forming a sheared surface.

Generally, a metal material has a property of increasing ductility when a compressive stress is applied. Therefore, utilizing the improvement of ductility due to the pressure effect, the separation process is performed while a high hydrostatic pressure is applied to the material during shearing. The fine blanking method is to obtain a cut end face only by shearing while suppressing the occurrence of cracks in the steel sheet.

[0008] In order to obtain this effect, as a mold mechanism,
The following requirements must be met: (A) The material is fixed by a die and a plate holder (also serving as a stripper plate). (B) At the beginning of the processing step, a V-shaped projection is provided along the sheared portion in the plate surface direction in order to apply a high compressive stress to the material. (C) The punched product is pressed by a punch and an ejector to prevent bending. (D) The clearance between the punch and the die must be minimal and uniform over the entire circumference of the product.

That is, the die and the plate holder function as a blank holder, and the ejector functions as a counter cushion for the punch. Further, in order to make it effective, V-shaped projections are provided on one or both of the top and bottom (die and plate holder) of the blank holder along the shearing profile, and the punching direction (perpendicular to the shear angle) in the initial stage of processing. It is a necessary condition that the material is completely fixed by applying a hydrostatic pressure to the V-shaped projection and forming a continuous wall shape.

FIG. 6 shows a typical example of fine blanking.

As shown in the drawing, a female press 1 and a punch 2 are used by using a special press 6 which moves up and down (returns) specially.
The clearance (gap) is extremely small (0.01 to 0.02 m
m), a wedge-shaped projection 8 is protruded from the material presser 7 as shown in FIG. b, and the outer periphery of the punched shape is strongly pressed to apply hydrostatic pressure to the material 3, and further pressed by the ejector 9 from below the material 3. It was a punch. P,
... show a hydraulic mechanism.

This method has drawbacks in that not only is it difficult to manufacture a wedge-shaped mold, but also that the shape of the mold must be changed depending on the processing conditions.

In view of this, various proposals have been made for a compression shearing method which avoids the drawbacks caused by the wedge-shaped projections for imparting hydrostatic pressure.

For example, Japanese Patent Publication No. 57-128 proposes FIG.
It is shown in i-ho.

In the drawing, 10 is a die, 11 is a punch provided in the die, 12 is a composite type which cooperates with the die 10 as a punch and cooperates with the punch 11 as a die. is there.

First, the outside of the material 3 is punched by using the composite die 12 and the die 10 as shown in FIG. 2B. The punching between the inner diameter of the concave portion of the die 10 and the outer diameter of the composite die 12 is necessary. In addition to providing an appropriate clearance, the concave portion of the die 10 facing the composite mold 12 is provided sufficiently deep, and the inside of the material 3 is punched in a state where the inside of the material 3 can be bent without being pressed by the concave portion and the composite mold 12. Is performed. The material 3 punched by the punch 11 and the die 10 has a shape in which the center portion is curved and protrudes toward the concave bottom surface of the die 10 due to the punching moment based on the clearance between the inner diameter of the concave portion of the die 10 and the outer diameter of the composite mold 12. As a result, the material 3 is sheared so as to be broken and remains in the die 10, and the actual length of the material 3 along the curved surface in the radial direction of the upper die in particular corresponds to the amount of bending. It is larger than the inner diameter of the die 10. The degree to which the upper side of the material 3 is curved and extended increases as the clearance between the die 10 and the composite mold 12 increases. In order to appropriately change the bending, a punch 11 ′ may be provided in the composite mold 12 so that the punch 11 ′ is projected only during the punching of the material 3.

Next, as a second step, as shown in FIG. 3C, the material 3 remaining in the die 10 is pressed between the bottom surface of the die 10 and the end surface of the punch 11 to flatten the material 3 (the material 3 is removed). In any case where the bending deformation is elastic or plastic, flattening is possible by taking a sufficiently large pressing force.), And the material 3 is not limited to the clamping force by the die 10 and the punch 11, and especially in the upper side thereof. As a result of the outer diameter of the material 3 being pressed against the inner diameter of the die 10 and being compressed by the difference between the actual length in the die radial direction and the inner diameter of the die 10, the material 3 receives a compressive force as a whole from its side surface.

Further, as a third step, the material 3 on which the compressive stress from the side surface is superimposed in the second step is subjected to shearing with a punch 11 and a die 12 as shown in FIG. 2 to obtain a product 13 as shown in FIG. Can be.

In this case, by superimposing the compressive stress from the side, the shear principal stress direction can be made perpendicular,
Further, since the stress state of the shear stress portion is a so-called hydrostatic pressure state in which pressure is applied from all directions, the ductility is increased and it is difficult to break, so that a product having no broken surface or burrs can be obtained by shearing.

By performing such compression shearing, it is possible to easily punch out a high-precision product that does not require the conventional secondary machining and shaving.

The proposal of Japanese Patent No. 2744963 is as follows.
As shown in FIGS.

That is, in the figure, 14 is a die, 15 is a blank holder provided in the hole 16 of the die 14 so as to be able to move up and down, and 17 is a punch having the same diameter as the hole 15. The metal plate material m is formed in advance so that the outer diameter thereof is larger than the inner diameter of the hole 16 by a notch c (for example, about 0.3 mm). When the material m is disposed on the hole 16, the surrounding member 18 surrounds the outer peripheral surface of the material m.
With a small gap g (for example, 0.2 m
m) is fixed on the die 11 via a plate-shaped spacer 19 having a required thickness. The surrounding member 18 has a tapered inner surface 20 so that the material m can be easily loaded into the hole 13 from above. Reference numeral 21 denotes a sleeve slidably covering the outer periphery of the punch 17.

For this reason, when the punch 17 is pressed down and the material m is pushed into the hole 16 of the die 14 and a shear stress is applied to the cut c, as shown in FIG.
8 and is extended as the chips d in the gap g by being guided by the inner surface of the chip 8. Then, by further reducing the punch 17, the chips d are separated from the material m as shown in FIG. 9A is a perspective view showing an example of a product p obtained by the punching method, and FIG.
FIG. 2 shows a perspective view of chips d formed at that time.

Since the surrounding member surrounding the outer peripheral surface of the metal plate material is provided and a gap is formed between the surrounding member and the upper surface of the die, the punch can be pressed down. According to the company, the cut surface obtained by pruning can be obtained, which has a beneficial effect of achieving high precision and beautiful finish.

[0025]

In the compression shearing method which avoids the drawbacks caused by the wedge-like projections for applying a series of hydrostatic pressures, a comprehensive study from the viewpoints of cost and operability will be made. In this case, a special expensive press that moves up and down specially must be used, resulting in high cost.

In the case of FIG. 6, as in FIG. 5, an expensive dedicated press is indispensable, and it takes two steps and the scrap becomes very small, so that there is a problem in scrap removal.

Further, according to the conventional processing method shown in FIG. 4, the outer peripheral portion of the material is provided with a material holder 1.5 to 2 times the material thickness.
And the yield of the material is poor for thick plates, but the methods of FIGS. 5 and 6 require more material.

In the case shown in FIG. 7, the blank is punched out and then the inner punching (a part to be a product) is performed by one mold because of a strong hydraulic device or a backward movement for the outer punching. A press (dedicated press) is required, which increases the cost. In the case of the one shown in FIGS. 8 and 9, the material is guided in a form developed from the shaving shown in FIG. With the small material restraining force received,
It is possible to obtain a product having a clearer shear surface without a fractured surface than conventional shaving. However, it is necessary to remove the guide of the material for each process in order to eliminate scraps, and the processing process takes a long time, and is not suitable for mass production.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fine shearing method in a compression shearing method that avoids the drawbacks caused by wedge-shaped projections for applying hydrostatic pressure. It is an object of the present invention to provide a precision punching method for producing an equivalent product by using a usual general press with a good material yield (economical efficiency), good operability, and low cost.

[0030]

In order to achieve the above object, a precision punching method according to the present invention employs a conventional metal press provided with a punch in a lower die, in which a metal material is punched by a punch and a die in advance. The material is formed to have a diameter slightly larger than the hole diameter of the die by the cutting amount, and the material is restricted in the escape direction by the material restraining plate attached to the upper die. The material is pinched and punched while the material is pinched by an ejector arranged in the inside, and the product and scrap are dropped to a lower mold by the ejector.

[0031]

[Function] Since a predetermined hydrostatic pressure can be obtained by restricting the flow of the material in the direction in which the material escapes by the material restraining plate attached to the upper die, it is sufficient if there is a material of about 1 mm on the outer periphery of the product shape, and material can be saved. Also, as the plate thickness increases, the yield rate of the material improves, and the material can be saved, and a product equivalent to fine blanking can be obtained.

Since no extra dedicated press equipment is required, it is not expensive, and products and scraps do not remain in the mold, so that they can be easily collected and operability is good.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS.

In the figure, reference numeral 22 denotes a lower die, on which a material guide 25 is provided on the upper surface of a scrap removing plate 24 supported by a spring 23, and a punch 2 is provided.

Reference numeral 26 denotes an upper mold, and a die 27 has a spring 2
8 is equipped with a backup ejector 29, and a material restraining plate 30 is attached to the lower surface of the die 27.

Thus, the material 3 having a margin of about 1 mm on the outer circumference is set via the material guide 25 (FIG. 1), and the upper mold 26 is lowered, and the material 3 between the ejector 29 and the punch 2 is moved.
The punch 2 is lifted up and punched (Fig. 2)
Then, the hydrostatic pressure acts by the flow restraining action of the material 3 of the material restraining plate 30 in the escape direction, and punching without burrs and drooping is achieved.

When the punch 2 returns, the upper mold 26 rises, and the ejector 29 descends, the product 31 and the scrap 32 fall onto the lower mold 22 and are collected (FIG. 3).

[0038]

Since the present invention is constituted as described above, a product equivalent to fine blanking can be produced by a conventional general method in a compression shearing method which avoids the drawbacks caused by wedge-shaped projections for applying hydrostatic pressure. The material press (economical efficiency), the operability, and the cost can be reduced by a mechanical press, which greatly contributes to the industry.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the procedure of the processing method of the present invention.

FIG. 2 is an explanatory view of a procedure of the processing method of the present invention.

FIG. 3 is an explanatory view of a procedure of the processing method of the present invention.

FIGS. 4A and 4B are explanatory diagrams of a finish punching procedure in a metal press using a general press.

FIGS. 5A and 5B are explanatory diagrams of procedures of a conventional processing method for eliminating burrs and drooling.

FIGS. 6A and 6B are explanatory diagrams of a procedure of a so-called fine blanking method.

FIGS. 7A to 7E are explanatory diagrams of the procedure of the conventional finish punching method in which the application of hydrostatic pressure is achieved without wedge-shaped projections.

8 (a) to 8 (c) are explanatory views of a procedure of a finish punching method in which hydrostatic pressure is applied without a conventional wedge-shaped projection.

9A and 9B are overhead views of products and scrap obtained by the method of FIG. 8;

[Explanation of symbols]

 1; female mold 2; punch 3; material 4; product 5; blank 6; press 7; material retainer 8; projection 9; ejector 10; dies 11, 11 '; punch 12; composite mold 13; product 14; dies 15; Blank holder 16; hole 17; punch 18; surrounding member 19; spacer 20; inner surface 21; sleeve 22; lower mold 23; spring 24; scrap removing plate 25; material guide 26; upper mold 27; die 28; spring 29: Ejector 30; Material restraint plate 31; Product 32; Scrap c; Cutting margin d; Chip g; Gap m; Material p; Product P;

Claims (1)

[Claims] When a metal material is punched by a punch and a die in an ordinary metal press having a punch formed in a lower die, the material is previously formed to have a diameter slightly larger than a hole diameter of the die by an amount corresponding to a cutting allowance. The material is restrained from flowing in the direction in which the material escapes by the material constraining plate attached thereto, and the material is punched out while the material is sandwiched between the punch and the ejector provided in the hole of the die. A precision stamping method in metal stamping, wherein the scrap is dropped onto a lower mold.