JP2008290128A - Punching apparatus and punching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a punching apparatus with improved formability for extension flange on the brunching end surface, and exerting equal effect even in a workpiece having various strength. <P>SOLUTION: In the punching apparatus including a punch and a die, the punch has an outer periphery 10 having a punching blade on the periphery of the bottom surface, and a projection part 11 projecting from the bottom surface of the outer periphery inside the outer periphery. The height of the projection part 11 projecting from the bottom surface of the outer periphery is variable according to the load in punching. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a punching apparatus and a punching method for metal plates such as iron, aluminum, titanium, magnesium and alloys thereof used in automobiles, home appliances, building structures, ships, bridges, construction machines, various plants, penstocks, etc. In particular, the present invention relates to an improvement in stretch flangeability of a punching end face generated by punching.

  Metal plates such as automobiles, home appliances, and building structures are often punched with a punch 2 and a die 3 as shown in FIG.

  As shown in FIG. 2, the punched surface is formed within the clearance between the punch 4 and the die 3 formed by the workpiece 1 being entirely pushed by the punch 2 (hereinafter referred to as “clearance” unless otherwise specified). In this case, the workpiece 1 is drawn into the punch and die clearance) and the workpiece 1 drawn into the clearance between the punched surface 2 and the die 3 is formed. It is constituted by a fracture surface 6 formed by breaking the material 1 and a burr 7 generated on the back surface of the workpiece 1.

  As a condition of the punched end face with good stretch flangeability, the end face must be smooth and less work-hardened.

  From this point of view, as shown in FIG. 3, a punching method and apparatus in which a protrusion 8 smaller than the size to be cut by punching is provided at the tip of the punch 2 is proposed in Patent Document 1 (hereinafter referred to as protrusion). This is called a punch. According to Patent Document 1, bending is applied to the workpiece by the protrusion 8, and the workpiece is easily cut by applying a tensile hydrostatic pressure and work hardening to the surface of the workpiece, so that the workpiece can be formed with less plastic deformation. In order to separate, a smooth end face with less work hardening can be obtained.

  Further, Patent Document 2 proposes a punching method and apparatus that rounds the corners of the protrusion 8 and efficiently applies a bending deformation to the material.

  Furthermore, the method of shaving the end face that has been punched once is also effective in improving stretch flangeability because a smooth end face is obtained. For example, a method and apparatus for performing punching and subsequent shaving as in Patent Document 3 are proposed. Has been.

Other than these, it is not intended to improve stretch flangeability, but at the inner periphery of the punch having a punching blade, a movable pressing pin provided on the bottom of the punch and a plate reverse press provided with a recess (counter The workpiece is pulled up by pressing the plate reversely during processing, giving a tensile force to the workpiece, and forming a workpiece with high-precision convex and concave portions with less knitted meat by the pressing pin A punching method that can be performed is described in Patent Document 4.
JP-A-5-23755 JP 2006-224151 A JP-A-6-39450 JP 2000-280034 A

  The inventions disclosed in the above Patent Documents 1 to 4 have some difficulties. In the punches with protrusions shown in Patent Documents 1 and 2, an appropriate protrusion height effective in stretch flangeability is determined according to the strength of the workpiece.

  Therefore, when the strength of the workpiece changes, the optimum amount of bending deformation cannot be ensured, and good stretch flangeability of the punched cross section cannot be obtained. There is a problem that it has to be replaced and costs high.

  In the shaving process, the number of shaving steps is increased by one step, resulting in an increase in cost. Even when punching and shaving are performed in a single process described in Patent Document 3, wear of the shaving blade becomes a problem, and the die life is reduced, which also increases costs.

  The punching method described in Patent Document 4 can be expected to improve the stretch flangeability as long as the amount of pressing by an appropriate pressing pin is used. However, the pressing amount of the pressing pin is provided on the unevenness of the molded product, that is, the plate reverse pressing Since it corresponds to the recessed portion formed, when the yield strength of the workpiece changes, the stretch flangeability cannot always be improved.

  It is an object of the present invention to provide a punching device and a punching method that improve the stretch flangeability of a punching end face generated by punching regardless of a change in yield strength of a workpiece.

In order to solve the above problems, the gist of the present invention is as follows.

  (1) In the punching device having a punch and a die, the punch has an outer peripheral portion having a punching blade around a bottom surface, and a protruding portion protruding from the bottom surface of the outer peripheral portion inside the outer peripheral portion. The punching device characterized in that the height of the protruding portion protruding from the bottom surface of the portion is variable according to the load at the time of punching.

  (2) The punching device according to (1), wherein the outer peripheral portion is movable in the movement direction of the punch via an elastic body.

  (3) The punching device according to (1), wherein the outer peripheral portion is movable in a punch moving direction via a hydraulic cushion.

  (4) The punching device according to (1), wherein the outer peripheral portion and / or the protruding portion is movable in the punch moving direction using a servo motor as a driving means.

  (5) A punching method using the punching device according to (1) or (4), wherein a punching load is measured during punching, and the larger the punching load is, the more protruding from the bottom surface of the outer peripheral portion. The punching method is characterized by increasing the height of the protruding portion.

  (6) Using the punching device according to any one of the above (1) to (4), the larger the yield stress of the workpiece measured in advance, the larger the yield stress from the bottom surface of the outer peripheral portion during punching. A punching method characterized by increasing the height of the protruding portion protruding.

  According to the present invention, when a plurality of types of workpieces having different yield strengths are punched, the stretch flangeability of the punched end face can be improved without exchanging the die according to the material strength.

  The present invention is described in detail below.

  As shown in FIG. 4, the present invention is a punching apparatus using a punch having a protrusion 9 protruding from the bottom surface of the outer peripheral portion 10 on the inside of the outer peripheral portion 10 having a punching blade around the bottom surface. Yes, the height of the protruding portion 9 protruding from the bottom surface of the outer peripheral portion changes in accordance with the load at the time of punching (yield strength of the workpiece 1) (the invention according to (1) above).

  As a result of an experiment in which the projection height and the yield strength of the workpiece 1 are changed in order to estimate the projection height effective for stretch flangeability, the present inventors have found that the projection height at which stretch flangeability is the best. It has been found that the larger the yield stress (also referred to as yield strength) of the workpiece 1 is, the larger it is.

  This result is that the protrusion height needs to be adjusted in accordance with the yield strength of the workpiece 1 in the punching process with the protrusion-provided punch. The mechanism that is movable in the movement direction of the punch is invented (the invention according to (2) above).

  The apparatus shown in FIG. 5 includes a pressing pin 11 serving as a protruding portion of a punch, which is enclosed by a cylindrical outer peripheral portion 10 having a punching blade, and an elastic body between the collar 11 a and the outer peripheral portion 10 of the pressing pressure pin 11. 12 is sandwiched between them. The elastic body 12 is compressed by the shear load applied to the outer peripheral portion 10 (punching blade), and the pressing pin 11 protrudes from the bottom surface of the punch.

  This mechanism enables punching with a punch having a high protrusion height in the case of a large shear load. Although it depends on the yield strength of the workpiece 1, the elastic body 12 must have a durability greater than the punching load, and it is desirable to use a high load urethane spring, a disc spring, or the like.

  The initial projection height is determined by obtaining a projection height suitable for the workpiece 1 having a yield strength as a reference in advance by experiment, and obtaining the deformation amount of the elastic body 12 from an assumed punching load. Can do. With respect to the elastic coefficient of the elastic body 12 and the initial protrusion height, a certain amount of trial and error is required during processing so that desired stretch flange characteristics can be obtained. However, once the conditions are determined, there is almost no need for subsequent adjustments.

  If the punch is relatively large and the punch load assumed is large, the outer peripheral portion 10 may be movable in the punch moving direction via the hydraulic cushion 13 instead of the elastic body 12 as shown in FIG. Good (invention according to (3) above). The hydraulic cushion 13 is a brake that uses a set load value as a resistance force, and the device shown in FIG. 6 has a relatively high protrusion height because the higher the punch load, the slower the speed of the outer peripheral portion 10. Since the displacement can be controlled more finely than when the elastic body 12 is used, initial settings (hydraulic pressure and projection height) are easier than in the case of the elastic body.

  If it is desired to control the height of the protrusion in more detail, the outer peripheral portion 10 and / or the protruding portion 11 can be moved in the punch moving direction by using the servo motor 16 as a driving means, and the pressing amount of the pressing pin 11 can be adjusted Good (the invention of (4)). In this case, from the viewpoint of the rigidity of the servo motor movable portion, a screw method (screw 15 driven by the servo motor 14) as shown in FIG. 7 is desirable.

  Further, unlike the case of the elastic body 12 and the hydraulic cushion 13, the pushing amount of the pressing pin 11 can be arbitrarily increased or decreased, so that the outer peripheral portion 10 may be a movable portion (FIG. 8) or the pushing portion. The pressure pin 11 may be a movable part (FIG. 9).

  When the servo motor 16 is used, unlike the case where the elastic body 12 and the hydraulic cushion 13 are used, it is necessary to measure the load at the time of punching or to measure the strength of the workpiece in advance.

  When measuring the load during punching using the apparatus of the invention according to the above (1) or (4), the punch load at the punch punching amount serving as a reference is determined in advance, and the punch load is determined to be higher than the reference during punching. If the load value is high, the protrusion height is increased, and if it is low, the protrusion height is decreased (the invention according to (5) above). In order to determine the reference protrusion height and punch load, trial and error are necessary as in the case of using the elastic body 12 and the hydraulic cushion 13 described above, but once the reference is determined, most subsequent changes are necessary. Absent.

  When the yield stress of the workpiece is measured in advance using the apparatus according to any one of (1) to (4) above, if the yield stress is high, the protrusion height is increased. If it is low, the height of the protrusion is lowered (the invention according to (6)). The yield stress of the workpiece 1 that is an index of the protrusion height may be the one described in the mill sheet, or may be measured in advance by a tensile test or the like.

  The yield strength of the workpiece and the projection height to be set are determined by trial and error as in the case of the inventions according to (1) to (5).

  In order to confirm the effect of the present invention, a round hole having a diameter of 10 [mm] is punched into the workpiece 1 using the apparatus shown in FIG. 10, and then a conical hole expanding test for evaluating the stretch flangeability of the punched end face. (Japan Iron and Steel Federation Standard JFST1001) was conducted.

  The apparatus of FIG. 10 is movable in the punch moving direction via a high-load urethane spring 17 which is an elastic body provided between the outer peripheral portion 10 and the collar 11a of the pressing pin 11, and the higher the punching load, the higher the punching load. The protruding amount of the pressing pin 11 is increased. The workpiece 1 used was a steel plate having a thickness of 1.6 mm, a tensile strength 590 MPa class (yield strength 330 MPa class) and a tensile strength 440 MPa class (250 MPa class) steel sheet.

  In addition, the amount of protrusion (protrusion height) of the initial pressing pin 11 was determined by conducting a prior experiment using a punch with a conventional protrusion fixed, and the best stretch flangeability in punching of a tensile strength 440 MPa class steel plate. The protrusion height of 0.3 [mm] was 0.08 [mm] obtained by correcting the elastic deformation of polyurethane.

  The height (fixed) of the protrusion in the conventional example is 0.3 [mm]. In the example of the present invention, in the case of a steel sheet having a tensile strength of 590 MPa, the outer peripheral portion 10 is connected to the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.35 to 0.37 [mm]. In the case of a steel plate having a tensile strength of 440 MPa in contact, the outer peripheral portion 10 contacts the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.29 to 0.31 [mm]. . The height of the protrusion was estimated from the amount of bending of the urethane spring measured by image measurement and the displacement of the pressing pin 11 measured by a linear encoder attached to the press.

  The urethane spring has a diameter of 30 mm and a hole with a diameter of 6 mm, and a thickness of 0.4 mm so that the elastic coefficient of the urethane spring is about 5.0 t / mm. I used something.

  Each trial is 20 sheets.

  FIG. 11 shows a hole expansion value of a test piece punched by a conventional punch having a protrusion height of 0.3 mm and a punch having a movable protrusion according to the present invention. The hole expansion value of the 440 MPa class steel plate is almost the same between the punches with both protrusions, but the hole expansion value of the 590 MPa class steel plate is improved by about 10% on average in the punched material according to the present invention. This is considered to be because the punching process can be performed at an appropriate projection height with respect to the strength of the workpiece 1 by the present invention.

  In order to demonstrate the effect of the present invention, the same test as in Example 1 was performed except that the urethane spring 17 in FIG. 10 was replaced with a hydraulic cushion pin 18. A schematic diagram of the apparatus is shown in FIG. The initial protrusion height was set to 0 [mm], and the load of the hydraulic cushion pin 18 was set to 2.7 [t].

  The height (fixed) of the protrusion in the conventional example is 0.3 [mm]. In the example of the present invention, in the case of a steel sheet having a tensile strength of 590 MPa, the outer peripheral portion 10 is connected to the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.35 to 0.36 [mm]. In the case of a steel plate having a tensile strength of 440 MPa, the outer peripheral portion 10 is in contact with the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.31 to 0.32 [mm]. . The height of the protrusion was estimated from the amount of displacement of the hydraulic cushion pin and the pressure pin 11 measured by a linear encoder.

  The result of the hole expansion value is shown in FIG. The hole expansion value of the 440 MPa class steel plate is almost the same between the punches with protrusions of both the conventional example and the example of the present invention, but the hole expansion value of the 590 MPa class steel plate is improved by about 8% on average for the punched material according to the example of the present invention. ing. This is considered to be because the punching process can be performed at an appropriate projection height with respect to the strength of the workpiece 1 according to the present invention.

  In order to verify the effect of the present invention, a test similar to that of Example 1 was performed by replacing the urethane spring 17 of FIG. 10 with a screw drive type servo motor drive mechanism 16. A schematic diagram of the apparatus is shown in FIG. The load during the punching process was measured by a load cell 19 attached to the upper part of the punch.

  The punch push-in amount was measured by a linear encoder attached to the press device. As a control algorithm for the projection height to be changed according to the load measured during the punching process, the relationship between the punch load when the 440 MPa class steel sheet is punched and the punch indentation amount is used as a reference, and the punch indentation amount is 0.2 mm. The protrusion height is increased by a value obtained by multiplying the difference in punch load value [N] by a coefficient of 0.000014. The initial protrusion height was 0.3 [mm].

  The height (fixed) of the protrusion in the conventional example is 0.3 [mm]. In the example of the present invention, in the case of a steel plate having a tensile strength of 590 MPa, the outer peripheral portion 10 is connected to the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.35 to 0.355 [mm]. In the case of a steel plate having a tensile strength of 440 MPa in contact, the outer peripheral portion 10 is in contact with the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.298 to 0.30 [mm]. . The height of the protrusion was measured with a rotary encoder attached to the servo motor (estimated from the rotation angle information of the motor).

  The result of the hole expansion value is shown in FIG. The hole expansion value of the 440 MPa class steel plate is almost the same between the punches with protrusions of both the conventional example and the example of the present invention, but the hole expansion value of the 590 MPa class steel plate is improved by about 11% on average in the punched material according to the present invention example. ing. This is considered to be because the punching process can be performed at an appropriate projection height with respect to the strength of the workpiece 1 by the present invention.

  Instead of measuring the load measurement at the time of punching, the same test as in Example 3 was performed using the yield strength data of the workpiece 1 measured in advance as an index for controlling the protrusion height. The apparatus is the same as that of the third embodiment shown in FIG. The projection height control algorithm was based on the maximum tensile strength of the 440 MPa class steel sheet, and the projection height was increased by a value obtained by multiplying the difference in maximum tensile strength by 0.00008.

  The height (fixed) of the protrusion in the conventional example is 0.3 [mm]. In the example of the present invention, in the case of a steel sheet having a tensile strength of 590 MPa, the outer peripheral portion 10 is connected to the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 is 0.35 to 0.36 [mm]. In the case of a steel plate having a tensile strength of 440 MPa, the outer peripheral portion 10 was in contact with the workpiece 1 when the height of the protruding portion protruding from the bottom surface of the outer peripheral portion 10 was 0.29 to 0.30 [mm]. . The height of the protrusion was measured with a rotary encoder attached to the servo motor (estimated from the rotation angle information of the motor).

  The result of the hole expansion value is shown in FIG. The hole expansion value of the 440 MPa class steel sheet is almost the same between the punches with protrusions of both the conventional example and the present invention example, but the hole expansion value of the 590 MPa class steel sheet is the average of the workpiece 1 punched according to the present invention example. It has improved by about 15%. This is considered to be because the punching process can be performed at an appropriate projection height with respect to the strength of the workpiece 1 according to the present invention.

It is the figure which showed the punching process typically. (A) The case of punching is shown. (B) The case of cutting is shown. It is a figure which shows typically the to-be-processed material end surface punched. It is a figure which shows the conventional punch with a protrusion typically. It is a figure which shows typically the punching apparatus which uses the punch with a variable projection of this invention. (A) The case of punching is shown. (B) The case of cutting is shown. It is a figure which shows typically the apparatus of another this invention. (A) The case of punching is shown. (B) The case of cutting is shown. It is a figure which shows typically the apparatus of another this invention. (A) The case of punching is shown. (B) The case of cutting is shown. It is a figure which shows typically the screw drive type linear motion mechanism driven with a servomotor. It is a figure which shows typically the punching processing apparatus whose punch outer peripheral part 10 is movable by the servomotor shown by FIG. (A) The case of punching is shown. (B) The case of cutting is shown. It is a figure which shows typically the punching processing apparatus with which the pressing pin 11 is movable by the servomotor shown by FIG. (A) The case of punching is shown. (B) The case of cutting is shown. It is a figure which shows typically the stamping apparatus by this invention used for Example 1. FIG. It is a figure which shows the hole expansion test result obtained in Example 1. FIG. It is a figure which shows typically the punching apparatus by this invention used for Example 2. FIG. It is a figure which shows the hole expansion test result obtained in Example 2. FIG. It is a figure which shows typically the punching apparatus by this invention used for Example 3, 4. FIG. It is a figure which shows the hole expansion test result obtained in Example 3. FIG. It is a figure which shows the hole expansion test result obtained in Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Work material 2 Punch 3 Die 4 Droop 5 Shear surface 6 Fracture surface 7 Burr 8 Protrusion 9 in a punch with a conventional protrusion Movable punch protrusion 10 Punch outer peripheral part 11 with a punching blade Pressing pin 11a Pressing pin collar 12 Elastic body 13 Hydraulic cushion mechanism 14 Servo motor 15 Screw 16 Servo motor linear motion mechanism 17 using screw 17 High load urethane spring 18 Hydraulic cushion pin 19 Load cell

Claims (6)

  In the punching device having a punch and a die, the punch has an outer peripheral portion having a punching blade around a bottom surface, and a protrusion protruding from the bottom surface of the outer peripheral portion inside the outer peripheral portion, and the bottom surface of the outer peripheral portion The punching device characterized in that the height of the protruding portion protruding further is variable according to the load at the time of punching.   The punching device according to claim 1, wherein the outer peripheral portion is movable in the moving direction of the punch via an elastic body.   The punching device according to claim 1, wherein the outer peripheral portion is movable in a punch moving direction via a hydraulic cushion.   2. The punching device according to claim 1, wherein the outer peripheral portion and / or the protruding portion is movable in the punch moving direction using a servo motor as a driving means.   The punching method using the punching device according to claim 1 or 4, wherein the punching load is measured during punching, and the higher the punching load, the higher the protruding portion protruding from the bottom surface of the outer peripheral portion. A punching method characterized by increasing the height.   Using the punching device according to any one of claims 1 to 4, the larger the yield stress of the workpiece measured in advance, the larger the protrusion of the protruding portion that protrudes from the bottom surface of the outer peripheral portion during punching. A punching method characterized by increasing the height.