KR101826694B1

KR101826694B1 - Blanking method and apparatus thereof

Info

Publication number: KR101826694B1
Application number: KR1020150183816A
Authority: KR
Inventors: 정승원; 안차균
Original assignee: 전병철; 상신브레이크주식회사
Priority date: 2015-12-22
Filing date: 2015-12-22
Publication date: 2018-02-13
Also published as: KR20170074486A

Abstract

The present invention is not limited to a general blanking apparatus, and it is possible to adjust the clearance of the blanking punch of the upper metal mold to a very small value and to provide a uniform curvature to the blanking unit which is in direct contact with the workpiece in the lower metal mold, The present invention also provides a blanking method and apparatus that allow a level of processing accuracy to be achieved.
The blanking method according to the present invention for achieving the above object is a blanking method using a general blanking apparatus rather than a fine blanking apparatus, wherein a clearance between a blanking punch of an upper mold and a die plate of a lower mold And the blanking portion abutting the workpiece in the die plate is curved so as to have a radius of curvature of 0.2 to 0.8, and then the workpiece is blanked.

Description

[0001] BLANKING METHOD AND APPARATUS THEREOF [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blanking method and apparatus thereof, and more particularly, to a blanking method for adjusting a clearance of an upper mold and a curvature of a lower mold so that a general blanking apparatus can have a processing accuracy equivalent to that of a fine blanking apparatus. .

Generally, in blanking or stamping operations, parts are produced that have a shear shear shear with only 1/3 of the shear, and roughly 2/3 of the fractured section. If tolerance or good surface treatment conditions are required for these shear / fractured surfaces, the parts must be reworked by milling, grinding, and so on. Production of precise parts requires at least two or more additional operations per component, which is inefficient in terms of productivity.

With the development of fine blanking technology, we have been able to overcome the limitations of the above press work and provide superior quality products. Fine blanking technology is a technique to prevent the occurrence of a fracture by receiving a cushion in the same direction as a punch from the opposite side of a mold punch. In a single blanking process, the required fine cross section and good product precision are obtained over the entire thickness of the product Which is capable of obtaining a finished cross section that does not require further machining. This fine blanking technique is applied to a product which does not have economical efficiency, for example, a product having a thickness of about 2 to 15 mm because the subsequent process is increased when the precision is used in general press blanking for the purpose of use.

Therefore, fine blanking products are mainly used for products that require precision of products and surface quality, such as functional parts of automobiles, compressors of refrigerators, electric and electronic structural products, and general mechanical elements. However, since the fine blanking press for the fine blanking technique has a cost of 10 times or more higher than that of a general press, it has a problem of causing an increase in production cost. In the case of a fine blanking press currently used in Korea, Since the equipment is imported, considerable time and efforts must be taken in the event of equipment failure, which is disadvantageous in terms of A / S.

A technique for solving the problems of such an expensive fine blanking apparatus is disclosed in Korean Patent Laid-Open Publication No. 2005-0054662 (entitled "Fine Blanking Apparatus", published on Jun. 10, 2003) (Patent Document 1). This fine blanking apparatus can perform a fine blanking operation by simply installing a separate die set and a hydraulic unit on a mechanical or hydraulic type general press, thereby making it possible to enhance price competitiveness compared to existing fine blanking presses, And also it is possible to maximize the effect of the hydrostatic pressure by directly transmitting the strong hydraulic pressure using the hydraulic unit in the precision of the dimensions and the shape of the product, will be.

However, since this fine blanking apparatus actually requires a complicated die set and a hydraulic unit to be further connected and connected, the conventional blanking apparatus is not used as it is. In other words, the upper die set is installed on the slider of the press and assembled with the upper mold to provide the hydraulic binding force against the non-striking portion of the material during operation of the main punch of the upper mold, A lower die set for providing a hydraulic pressure force against the material striking portion during operation of the main punch of the upper mold, and a hydraulic unit for supplying hydraulic pressure to the upper die set and the lower die set while being installed on one side of the press In order to install such an upper die set, a lower die set, and a hydraulic unit, there has been a problem in that a conventional general blanking apparatus is largely remodeled and a high facility cost is required in addition to equipment installation.

KR 10-2005-0054662 A

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a blanking apparatus in which a clearance of a blanking punch in an upper metal mold is adjusted to be very small, The present invention provides a blanking method and apparatus for providing a uniform curvature to a portion of a blanking apparatus, thereby enabling the blanking apparatus to have a level of processing accuracy equivalent to that of a fine blanking apparatus.

The blanking method according to the present invention for achieving the above object is a blanking method using a general blanking apparatus rather than a fine blanking apparatus, wherein a clearance between a blanking punch of an upper mold and a die plate of a lower mold And the blanking portion abutting the workpiece in the die plate is curved so as to have a radius of curvature of 0.2 to 0.8, and then the workpiece is blanked.

According to another aspect of the present invention, there is provided a blanking method using a general blanking apparatus rather than a fine blanking apparatus, wherein the blanking punch includes a first blanking punch and a second blanking punch sequentially performing a blanking process Configured; Wherein the clearance between the primary blanking punch and the die plate of the lower die is adjusted to 0.1 to 0.6% of the thickness of the workpiece, and the clearance between the die plate of the secondary blanking punch and the lower die is a clearance of the primary blanking punch To 0.5% to 1.0% of the thickness of the workpiece while having a larger value; Wherein when the primary blanking punch is used, the primary blanking portion of the die plate abutting the workpiece is curved so as to have a radius of curvature of 0.4 to 0.8, and when the secondary blanking punch is used, The abutting secondary blanking portion is curved so as to have a curvature radius of 0.2 to 0.5 while having a curvature radius smaller than that of the primary blanking portion; A portion of the thickness of the workpiece is sheared using the primary blanking punch and then the remaining portion of the thickness of the workpiece is finally sheared using the secondary blanking punch.

At this time, 90% or more of the thickness of the workpiece can be sheared by using the primary blanking punch.

On the other hand, when using the primary blanking punch, a pad for elastically supporting the lower surface of the workpiece may be mounted on the die plate, and the pad may be mounted on the gas spring.

The first blanking punch and the second blanking punch are installed in the upper mold at regular intervals, and the workpiece is installed on the die plate so as to be moved by the predetermined distance to perform the primary blanking and the secondary blanking process Can be performed simultaneously.

In order to achieve the above object, a blanking apparatus according to the present invention is a general blanking apparatus which is not a fine blanking apparatus, in which the clearance between the blanking punch of the upper mold and the die plate of the lower mold is made 0.1 to 1.0% And a blanking portion of the die plate abutting the workpiece is curved so as to have a radius of curvature of 0.2 to 0.8, and then the workpiece is blanked.

According to another aspect of the present invention, there is provided a blanking apparatus, not a fine blanking apparatus, wherein the blanking punch is configured such that a primary blanking punch and a secondary blanking punch sequentially perform a blanking process; Wherein a clearance between the primary blanking punch and the die plate of the lower die is controlled to be 0.1 to 0.6% of a thickness of the workpiece, and a clearance between the die plate of the secondary blanking punch and the lower die is a clearance of the primary blanking punch Adjusted to 0.5 to 1.0% of the thickness of the workpiece while having a larger value; Wherein when the primary blanking punch is used, the primary blanking portion of the die plate abutting the workpiece is curved so as to have a radius of curvature of 0.4 to 0.8, and when the secondary blanking punch is used, The abutting secondary blanking portion is curved so as to have a curvature radius of 0.2 to 0.5 while having a curvature radius smaller than that of the primary blanking portion; Shearing a portion of the thickness of the workpiece using the primary blanking punch and then finally shearing the remaining portion of the thickness of the workpiece using the secondary blanking punch.

On the other hand, when using the primary blanking punch, a pad for elastically supporting the lower surface of the workpiece is mounted on the die plate, and the pad can be mounted on the gas spring.

The primary blanking punch and the secondary blanking punch are installed at predetermined intervals in the upper mold so that the primary blanking and the secondary blanking process can be performed at the same time, Lt; / RTI >

According to the blanking method and apparatus according to the present invention configured as described above, the accuracy of the general blanking can be improved to a fine blanking level by changing only the dimensions and shape of the upper mold and the lower mold without adding additional equipment. As a result, a component having excellent surface roughness and flatness can be produced without using an expensive fine blanking apparatus.

In addition, according to the present invention, it is not necessary to reprocess after milling, grinding or the like subsequent to a general blanking operation, so that the process can be greatly shortened and the production cost can be greatly reduced.

In addition, the lower surface of the workpiece is elastically supported by using a pad attached to the gas spring, thereby preventing the deformation of the workpiece generated in the blanking process to the utmost, thereby improving the flatness of the workpiece.

In addition, the primary blanking process and the secondary blanking process can be performed at the same time, thereby greatly improving the product production speed.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a configuration of a conventional general blanking apparatus. Fig.
2 shows a configuration of a blanking apparatus according to the present invention.
3 illustrates the operation of the blanking apparatus according to the present invention;
FIG. 4 is a photograph of a primary blanking and a secondary blanking working material according to the present invention. FIG.
5 is a comparison of a blanking material of the prior art and a cut surface of a blanking material according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawings, in which: Fig.

However, it should be understood that the present invention is not limited to the embodiments disclosed herein but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The blanking apparatus according to the present invention can achieve excellent processing accuracy of fine blanking without using an expensive fine blanking apparatus. That is, the most basic feature of the present invention is that a general blanking apparatus is used instead of the fine blanking apparatus.

In the fine blanking apparatus, the shearing force, the V-ring force, and the counter force are simultaneously applied to the common blanking apparatus while the shearing force acts only on one shearing force. It can be machined so that the whole cross section is 100% clean. Therefore, the general blanking apparatus other than the fine blanking apparatus can be defined as performing blanking with only the shearing force without using the Vringing force and the counter force. The present invention is capable of achieving excellent processing accuracy of fine blanking only by changing the dimensions and shape of the upper and lower dies in the general blanking apparatus using only the shearing force.

The dimensions and shapes of the upper and lower dies used in the conventional blanking apparatus will be briefly described with reference to FIG. 1 to help understand how the sizes and shapes of the upper and lower dies are changed in the present invention.

1 shows a process of producing a wave part 110 that enters a brake liner through a blanking process for the workpiece 100. [ For this purpose, when a blanking punch 300 is mounted on an upper mold (not shown) and a workpiece 100 is placed on a die plate 200 constituting a lower mold, the blanking punch 300 So as to cut the work material 100 by applying a shearing force thereto. The cut workpiece is discharged to the outside of the blanking apparatus along the discharge port 230 formed in the die plate 200, the blanking plate 210, and the lower holder 220.

Typically, the blanking apparatus is given a constant clearance between the blanking punch 300 and the die plate 200. This clearance is an important control factor for determining the machining quality of the blanking product, together with the wear of the blade, the presence or absence of lubrication, the tolerance of the plate thickness, the work hardening rate and the like. Blanking process is to cut the hole of the die plate according to the size of the product and make the punch small as clearance because the cut sheet is the product after processing.

If the clearance is too small or too large, a large number of machining defects such as roll-over, burr and camber will occur in the front end face. Therefore, in order to increase the operating precision, the clearance is controlled in a proper range It is important. The proper clearance varies depending on the type of material, hardness, softness, thickness, etc. In the case of ordinary carbon steel, as shown in Fig. 1, a clearance of about 7 to 10% of the thickness of the workpiece is given.

On the other hand, the die plate 200 has holes formed in the shape of the product. When the blanking punch descends, the outer edge of the hole of the product shape formed on the die plate 200 acts as a blade, (100). The blade edge portion of the die plate 200 is referred to as a blanking portion 205 which is typically machined to have a right angle (R = 0). When the blanking portion 205 is at right angles, it acts like a sharp blade, allowing the blanking process to be performed better.

As described above, in the conventional general blanking process, the clearance between the die plate and the blanking punch is set to about 7 to 10% of the thickness of the workpiece, and the blanking portion 205 of the die plate 200 is curved Without the need to be exposed. In the general blanking process, when only 30% or more of the thickness is sheared, the remaining thickness portion is broken. As a result, as shown in FIG. 5 (a), a part having a shear surface sheared cleanly about 1/3 and a roughly broken fractured surface about 2/3 was produced. This part had to be reprocessed by milling, grinding and the like in order to increase the surface precision, and it is already mentioned that this is a main cause of deteriorating the productivity.

The blanking method and apparatus according to the present invention can change the clearance of the blanking punch and the shape of the blanking portion 205 of the die plate 200 by changing only the two control factors described above, So that it has a shear section.

Fig. 2 shows a configuration of the blanking apparatus according to the present invention.

The blanking apparatus of the present invention is a general blanking apparatus that is not a fine blanking apparatus and has a clearance between the blanking punches 30 and 31 of the upper mold (not shown) and the die plate 20 of the lower mold, And the blanking portions 23 and 24 of the die plate 20 abutting the workpiece 10 are curved so as to have a curvature radius R of 0.2 to 0.8 And then blanking the workpiece.

According to the present invention, the clearance is usually adjusted to be 0.1 to 1.0% of the thickness of the workpiece 10. As described above, conventionally, a clearance of 7 to 10% is given to ordinary carbon steel. It is thought that many defects such as sagging, burr, and camber are generated in the cut surface when it is out of this range. However, in the present invention, such a conventional prejudice is boldly removed and the clearance is adjusted to 0.1 to 1.0% very small.

Also, in the present invention, the blanking portions 23 and 24 of the die plate 20, which are in contact with the workpiece 10 and serve as a blade, are curved so as to have a curvature radius of 0.2 to 0.8.

When the clearance between the blanking punch and the die plate is largely adjusted to the same range as the conventional one, the present inventors have found that many blank sections, machining defects, and the like are generated regardless of whether the blanking section is curved or not, It has been found that, if the blanking portion is not curved, the cut surface of the blanked product may have many broken edges, machining defects, and the like. Therefore, it has been confirmed that a clean cross section can be obtained only by the combination of a small range of clearance and a curved blanking portion.

It is difficult to completely mathematically prove the principle of obtaining a clean cross-section over all thicknesses by the combination of a small size clearance and a curved blanking portion. However, due to the change of the two control factors, The process proceeds to a similar principle to the process of FIG. In other words, the blanking portions 23 and 24 of the die-cut die plate 20 are cut as if the blade is a dull blade, .

At this time, if the clearance is made small, the gap between the blanking punches 30 and 31 and the blanking portions 23 and 24 of the die plate 20 becomes very narrow, so that the workpiece is processed with the curved portion of the blanking portion 23.24 This will allow more contact, so cutting with dull blades will be the main processing method.

As is well known in the general blanking process, a high compressive stress or bending stress is applied to the workpiece at the beginning of compression due to the strong lowering force of the blanking punch, and a crack is generated in the cut surface. When the blanking punch is further lowered, the crack propagates more and more, and eventually the crack is broken. As a result, it has already been described above that the blanking process usually produces 1/3 clean shear front end and 2/3 roughly broken end faces.

However, according to the present invention, since the curved blanking portion is cut as if it is rubbed like a blunt blade, the occurrence of cracks on the cut material surface is remarkably reduced, and when the material is almost completely processed in the drawing or drawing process The fracture surface due to the propagation of the crack does not occur. Therefore, according to the present invention, even when the thickness of the workpiece becomes 90% or more of the thickness of the workpiece, only the shear surface that is sheared without producing a fracture surface is produced.

As described above, in the present invention, the clearance between the blanking punches 30 and 31 and the die plate 20 is adjusted to be very small to 0.1 to 1.0%, and the blanking portions 23 and 24 of the die plate 20 It is preferable to perform a curved surface processing so as to have a radius of curvature of 0.2 to 0.8.

If the clearance is less than 0.1%, the machining error becomes too large to produce a blanking product having an accurate dimension. If the clearance exceeds 1.0%, the shearing of the material by the curved blanking portions 23, A fracture surface is generated by the cracks. When the radius of curvature of the blanking portions 23 and 24 of the die plate 20 is less than 0.2, a shear force due to a sharp blade is applied at a right angle, so that a large number of cracks are generated at the cutting surface of the blank at the beginning of blanking, If the radius of curvature of the blanking portions 23 and 24 exceeds 0.8, the blade portion becomes too thin and the cutting process itself becomes difficult, resulting in more defects on the surface.

FIG. 2 shows a blanking apparatus using two blanking punches, which is a preferred embodiment of implementing the technical idea of the present invention described above.

The blanking apparatus of this embodiment is a general blanking apparatus other than the fine blanking apparatus, and the blanking punch is configured such that the primary blanking punch 30 and the secondary blanking punch 31 sequentially perform the blanking process. The clearance C1 between the primary blanking punch 30 and the die plate 20 of the lower mold is adjusted to 0.1 to 0.6% of the thickness of the workpiece 10 and the secondary blanking punch 31 and lower The clearance C2 between the die plates 20 of the mold is adjusted to 0.5 to 1.0% of the thickness of the workpiece 10 so as to have a larger value than the clearance C1 of the primary blanking punch 30. [

When the clearance of the primary blanking punch 30 is less than 0.1%, the machining error becomes too large to produce a blanking product having an accurate dimension. If the clearance exceeds 0.6%, there is a possibility that a judgment surface due to cracks may occur , The clearance difference with the succeeding secondary blanking punch 31 is not large, and the secondary blanking operation may not be performed smoothly.

Even when the clearance of the secondary blanking punch 31 is less than 0.5%, the difference in clearance with the primary blanking punch 31 is not large enough to make the secondary blanking work unsuccessful. If the clearance exceeds 1.0% Shearing of the workpiece by the processed blanking portions 23 and 24 can not sufficiently take place and a fracture surface due to cracks is generated.

On the other hand, the reason why the clearance of the secondary blanking punch 31 is larger than the clearance of the primary blanking punch 30 is that the secondary blanking punch 31 is cut by the primary blanking punch 30 So that it can smoothly enter the space of the work material 10.

When using the primary blanking punch 30, the primary blanking portion 23 of the die plate 20 abutting the workpiece is curved so as to have a radius of curvature R1 of 0.4 to 0.8, The secondary blanking portion 24 of the die plate 20 abutting the workpiece 10 when using the blanking punch 24 has a curvature radius R2 smaller than that of the primary blanking portion 23, So that the curvature radius of the curved surface is equal to the curvature radius of the curved surface.

If the radius of curvature of the primary blanking portion 23 is less than 0.4, cracks may occur in the cutting surface of the blank in the initial stage of blanking. If the curvature radius of the primary blanking portion 23 exceeds 0.8, So that the cutting process itself becomes difficult and more defects are generated on the surface.

If the radius of curvature of the secondary blanking portion 24 is less than 0.2, a shear force due to a sharp blade is applied at a right angle, so that a large number of cracks are generated at the cutting surface of the blank at the initial stage of blanking, 24) is greater than 0.5, the edge of the blade is worn out, so that the effect of creating a clean cross-section at the initial stage of blanking can be reduced.

On the other hand, the curvature radius of the secondary blanking portion 24 is set to be smaller than the curvature radius of the primary blanking portion 23 because the secondary blanking shear only the remaining portion less than 10% after the primary blanking This is because by making the radius of curvature of the secondary blanking section 24 smaller, that is, by making the secondary blanking section 24 closer to a right angle, it is possible to obtain a clean front-face forming effect expected at the initial stage of general blanking.

Finally, a part of the thickness of the workpiece 10 is sheared by using the primary blanking punch 30 and then the remaining portion of the thickness of the workpiece 10 is cut by using the secondary blanking punch 31 And finally sheared. Preferably, the thickness T1 to be sheared by using the primary blanking punch 30 is 90% or more of the total thickness of the workpiece. This is because, if a clear shear cross section can be secured by 90% or more, a subsequent rework process is generally unnecessary.

In this manner, in the present embodiment, the two-stage blanking process is performed using the primary blanking punch 30 and the secondary blanking punch 31 provided adjacent thereto at a predetermined interval to achieve the following technical objective.

First, it is possible to obtain a clean cross section of 90% or more in the first blanking step. However, if the first blanking is completely cut, a fracture may occur in the remaining 10% portion due to the limit of the blanking process. In this embodiment, when a portion less than 10% is newly blanked, as in the case of a normal blanking apparatus, an initial 1/3 thickness is obtained as a clean front surface, and a portion of the last 10% or less is also blanked to a clean front surface. As a result, according to the two-step blanking process of this embodiment, a clean cross-section can be obtained over the entire thickness of the final blanking product.

Second, if the first blanking punch 30 and the second blanking punch 31 are installed in one upper mold, the first and second blanking processes can be performed simultaneously by only one lowering stroke of the upper mold. Therefore, if the workpiece is set to move on the die plate 20 by the distance between the primary blanking punch 30 and the secondary blanking punch 31, even if two blanking punches 30 and 31 are used, The blanking process can be completed only by a single lowering stroke of the mold.

According to the present embodiment, when the primary blanking punch 30 is used, a pad 25 for elastically supporting the lower surface of the workpiece 10 is mounted on the die plate 20. The pad 25 descends while uniformly supporting the workpiece 10 on the opposite side of the primary blanking punch 30 when the strong lowering force of the primary blanking punch 30 is applied to the workpiece 10, The compressive stress or the bending stress is unevenly applied or the stress concentration is reduced to some extent. As a result, the flatness of the product can be further improved.

In this case, when the pad 25 is attached to the general coil spring, the coefficient of elasticity of the coil is decreased with time, thereby reducing the effect of increasing the flatness. It is preferable to use a gas spring 26 which is superior in elastic holding force and durability to the coil spring.

FIG. 3 is a view showing the operation of the blanking apparatus according to the present invention. FIG. 4 is a photograph of a first blanking and a second blanking workpiece according to the present invention. This is a comparison of the cut surfaces of the blanking material.

The blanking apparatus according to the present invention first lowers the primary blanking punch 30 to perform a one-step blanking process on the workpiece 10. At this time, the clearance C1 between the primary blanking punch 30 and the die plate 20 of the lower mold is adjusted to 0.1 to 0.6% of the thickness of the workpiece 10, and the clearance C1 between the primary blanking portion 23 ) Is subjected to a blanking operation in a curved shape so as to have a radius of curvature (R1) of 0.4 to 0.8. As a result, 90% or more of the entire thickness of the workpiece 10 is blanked at the shear front end. In FIG. 4, it is possible to identify the half-finished blanking product 11 in which 90% or more of the total thickness of the workpiece 10 is cut by the one-step blanking process.

After the primary blanking process is completed, the workpiece 10 is moved by a predetermined distance, and then the secondary blanking punch 30 is lowered to perform a two-step blanking process. At this time, the clearance C2 between the secondary blanking punch 31 and the die plate 20 of the lower mold is controlled to 0.5 to 1.0% of the thickness of the workpiece 10, and the clearance C2 between the primary blanking portion 23 ) Is subjected to a blanking operation in a curved shape so as to have a radius of curvature (R2) of 0.2 to 0.5. Whereby the remaining 10% or less of the thickness of the workpiece 10 is also blanked to a completely clean front surface. In FIG. 4, the completely blanked product is discharged by the two-step blanking process and the remaining hole 12 can be identified.

As shown in FIG. 5, the product (A) produced through the blanking process coexisted with the front end and the fracture end, whereas the product (B) produced through the blanking process according to the present invention was clean Only the sheared shear plane exists.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, . Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

10: Working material 11: Primary blanking material
12: Secondary blanking material 20: Die plate
21: Blanking plate 22: Lower holder
23: primary blanking section 24: secondary blanking section
25: pad 26: gas spring
27: outlet 30: primary blanking punch
31: Secondary blanking punch

Claims

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A blanking method using a general blanking apparatus other than a fine blanking apparatus,
The blanking punch is configured such that the primary blanking punch and the secondary blanking punch sequentially perform the blanking process;
Wherein the clearance between the primary blanking punch and the die plate of the lower die is adjusted to 0.1 to 0.6% of the thickness of the workpiece, and the clearance between the die plate of the secondary blanking punch and the lower die is a clearance of the primary blanking punch To 0.5% to 1.0% of the thickness of the workpiece while having a larger value;
Wherein when the primary blanking punch is used, the primary blanking portion of the die plate abutting the workpiece is curved so as to have a radius of curvature of 0.4 to 0.8, and when the secondary blanking punch is used, The abutting secondary blanking portion is curved so as to have a curvature radius of 0.2 to 0.5 while having a curvature radius smaller than that of the primary blanking portion;
Wherein a portion of the thickness of the workpiece is sheared by using the primary blanking punch and then the remaining portion of the thickness of the workpiece is finally sheared using the secondary blanking punch.

The method of claim 2,
Wherein at least 90% of the thickness of the workpiece is sheared by using the primary blanking punch.

The method of claim 2,
Wherein when the primary blanking punch is used, a pad for elastically supporting the lower surface of the workpiece is mounted on the die plate.

The method of claim 4,
Wherein the pad is mounted on a gas spring.

The method of claim 2,
The primary blanking punch and the secondary blanking punch are installed at predetermined intervals in the upper mold, and the workpiece is installed on the die plate so as to move by the predetermined distance, so that the primary blanking and the secondary blanking process are simultaneously performed The blanking method comprising the steps of:

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As a general blanking apparatus other than a fine blanking apparatus,
The blanking punch is configured such that the primary blanking punch and the secondary blanking punch sequentially perform the blanking process;
Wherein a clearance between the primary blanking punch and the die plate of the lower die is controlled to be 0.1 to 0.6% of a thickness of the workpiece, and a clearance between the die plate of the secondary blanking punch and the lower die is a clearance of the primary blanking punch Adjusted to 0.5 to 1.0% of the thickness of the workpiece while having a larger value;
Wherein when the primary blanking punch is used, the primary blanking portion of the die plate abutting the workpiece is curved so as to have a radius of curvature of 0.4 to 0.8, and when the secondary blanking punch is used, The abutting secondary blanking portion is curved so as to have a curvature radius of 0.2 to 0.5 while having a curvature radius smaller than that of the primary blanking portion;
To shear a portion of the thickness of the workpiece using the primary blanking punch and then to final shear the remaining portion of the thickness of the workpiece using the secondary blanking punch.

The method of claim 8,
Wherein the primary blanking punch is used to shear at least 90% of the thickness of the workpiece.

The method of claim 8,
Wherein when the primary blanking punch is used, a pad for elastically supporting the lower surface of the workpiece is mounted on the die plate.

The method of claim 10,
Wherein the pad is mounted on a gas spring.

The method of claim 8,
Wherein the primary blanking punch and the secondary blanking punch are installed at a predetermined interval in the upper mold so that the primary blanking and the secondary blanking process are simultaneously performed, The blanking apparatus comprising: