Die unit for punching operations

Abstract: A die unit for performing punching operations in cooperation with a punch unit is disclosed. The die unit includes a die body (3) formed with a die hole (5) extending in an axial direction for receiving a cutting edge of the punch body (17) , and with an upper surface portion (7) extending in a plane normal to the axial direction. The die unit also includes a projecting portion (11) formed along the perimeter of the die hole (5) on the upper surface portion (7) of said die body (3). With this die unit, punching operations can be performed on a workpiece without producing s burr that projects downwardly below the lower surface of the workpiece. Thus burr removing operations are dispensed with after the punching operations.

Description: BACKGOUND OF THE INVENTION Field of the Invention The present invention relates to a die unit for performing punching operations on a workpiece in cooperation with a punch unit, and a method of extending the working life thereof. Description of the Prior Art As shown in Fig. 1, a conventional die unit 101 has a die body 103 formed with a die hole 105 passing vertically through a substantially center portion thereof. When a punching is performed on a metal workpiece W with the die unit 101 and a punch unit 107, the punch unit 107 is descended after the workpiece W is placed on an upper surface of the die body 103. Thus, the workpiece W is held between a punch guide 109 and the die body 103 and supported thereby. When a punch body 111 is further descended and a punching is performed on the workpiece W in cooperation with the die body 103, a refuse WA removed from the workpiece W is dropped off downwardly through the die hole 105. When the punching is performed by the above-mentioned conventional punch unit 107 and die unit 101, a burr B1 is formed under the workpiece W as shown in Fig. 2A. If this burr B1 is left as it is, the burr B1 may constitute a hindrance to the following processing. Therefore, a burr removing process for removing the burr B1 is performed, for example, by grinding tools. However, when the burr removing process is performed to remove the bur B1, a secondary burr B2 extending in the horizontal direction as shown in Fig. 2B may be formed in the workpiece W. Accordingly, there was a problem that the burr formed during punching operations could not completely be removed and constituted a hindrance to the following processing as it used to be. Further prior art is disclosed in JP-A-63101029, which illustrates the combination of features specified in the preamble of claim 1. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a die unit for performing punching operations on a workpiece in cooperation with a punch unit without producing a burr on the lower surface of the workpiece, and thereby the burr removing operations are no longer necessary. This object is achieved by the die unit according to claim 1. In this die unit, when the ridge portion having the horizontal plane portion is worn away during punching operations, the auxiliary cap is detached from the die body and the inclined portion is ground parallel to an original surface. Thus when the auxiliary cap is attached to the die body once more, the ridge portion again projects upwardly of the upper surface of the auxiliary cap by a desirable amount, and the life of the die unit is extended. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view illustrating a punching operation by conventional punch unit and die unit. Fig. 2 A is cross-sectional view illustrating a workpiece formed with a burr resulting from a punching operation by the conventional punch and die units, and Fig. 2B is a cross-sectional view illustrating a workpiece resulting from a burr removing operation on the workpiece of Fig. 2A. Fig. 3 is a cross-sectional view illustrating a further die unit. Fig. 4 is an explanatory view illustrating a punching operation with the die unit according to Fig 3. Fig. 5 is a cross-sectional view illustrating a workpiece processed by the punch unit and die unit according to Fig. 3. Fig. 6 is a cross-sectional view of an embodiment of the die unit according to the present invention. Fig. 7 is an explanatory view illustrating a punching operation on a workpiece by the punch unit and die unit according to the embodiment. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment, according to the present invention, will be described in detail with reference to the accompanying drawings. The examples according to Figures 3 to 5 serve to aid understanding, but do not relate to claimed subject-matter. Referring to Fig. 3, a die unit is composed of a die body 3. A die hole 5 passing vertically is formed in a substantially center portion of this die body 3. In an upper peripheral portion of this die hole 5, a projecting portion 11 slightly protruding upward relative to an upper surface 7 of the die body 3 is formed. The projecting portion 11 has a horizontal surface 9. Fig. 4 illustrates a punching operation performed on a workpiece W with the die unit 1. After the workpiece W is placed on the upper surface 7 of the die body 8 and the horizontal surface 9 of the projecting portion 11, a punch guide 15 of a punch unit 13 is descended. Then, the workpiece W is held between the punch guide 15 and the die body 3 and supported thereby. Next, when a punch body 17 is further descended and the workpiece W is punched by the engagement of the punch body 17 with the die body 3, a refuse WA is cut out from the workpiece W and a hole Wa is formed in the workpiece W. As shown in Fig. 5, a chamfering portion (or a recessed portion) M recessed upwardly is formed along the perimeter of the hole Wa with the projecting portion 9,. Accordingly, a burr B formed in the chamfering portion M does not project outwardly of a lower surface of the workpiece W. Since such burr B does not constitute a hindrance to the following processing, it is unnecessary to be removed. In this way, with the die unit of Figures 3 to 5, the chamfering portion M is formed in the workpiece so that the burr B is prevented from projecting below the lower surface of the workpiece W. Therefore burr removing operations are no longer necessary. Further, since the chamfering portion is formed during the punching operation, the operation is quick and simple. It is preferable that the height H of the protruding portion 11 is equal to 0.2 to 0.5mm, and the width A of the horizontal surface 9 is equal to 0.1 to 0.2mm. With the die having such dimensions, the chamfering operation can be favorably performed in a workpiece. That is, the burr B is located well inside the chamfering portion M; in other words, the burr B is surely prevented from protruding downward from the lower surface of the workpiece W. In Fig. 3, the outside surface of the protruding portion 11 is inclined relative to the vertical axis of the die body 3, but it may be parallel to the vertical axis. Further, a cross-sectional shape of the die hole 5 in a horizontal direction may be circular, rectangular or the like. Fig. 6 illustrates an embodiment 201 of the die unit according to the present invention. A die unit 201 of the second embodiment includes a die body 203 and an auxiliary cap 221. The die body 203 is formed with a die hole 205 passing vertically through a substantially center portion thereof. A conical surface portion 219 spreading outwards downwardly is further formed on the outer peripheral surface thereof, and a ridge portion 209 is formed at the upper portion 211 of the die body 203. The ridge portion 209 is preferably formed with a horizontal plane surface. The auxiliary cap 221 is detachably provided on the die body 203. In more detail, a hole 231 having conical shaped portion corresponding to the conical surface portion 219 is formed in the auxiliary cap 221 and the auxiliary cap 221 is provided on the die body 203 so that the conical shaped portion of the hole 231 engages with the conical surface portion 219. As illustrated in Fig. 6, the ridge portion 209 is designed to slightly protrude upward above an upper surface 223 of the auxiliary cap 221. The auxiliary cap 221 may be fixed to the die body 203 by suitable means. Fig. 7 illustrates the manner in which a workpiece W is processed by the punch unit 13 and the die unit 201 according to the second embodiment. After the workpiece W is placed on the upper surface 223 of the auxiliary cap 219 and the horizontal portion 209 of the body 203, the punch guide 15 of the punch unit 13 is descended to hold the workpiece W downwardly. Next, when the punch body 17 is further descended and the workpiece W is punched with the engagement of the punch body 17 with the die body 203, a refuse WA is cut out from the workpiece W and falls downward through the die hole 205. The die unit 201 of the embodiment has the same function as the die unit 101 of Figures 3 to 5. That is to say, as illustrated in Fig. 5, the chamfering portion (or the recess portion) M is formed along the perimeter of the hole Wa on a lower surface of the workpiece by the punching operation. Therefore the burr B formed along the perimeter of the punch hole Wa is located inside the chamfering portion (or the recessed portion) so as not to project downwardly below the lower surface of the workpiece W. Accordingly, burr removing operations after punching operations are no longer necessary. Furthermore, in the die unit 201 of the embodiment, when the ridge portion 209 of the die body 203 is worn away by punching operations, the auxiliary cap 221 is detached from the die body 203, and the inclined portion 219 is ground so that a new surface is parallel to the original surface. Thus, when the auxiliary cap 221 is again attached to the body 203, the new ridge portion 209 projects upwardly by a suitable amount above the upper surface 223 of the auxiliary cap 221. Grinding of the inclined portion 219 can be performed several times until the height of the vertical portion 203a of the body 203 becomes zero. Accordingly, the grinding operations can be repeatedly performed, whereby the life of the die is extended. In this connection, when the grinding operations are repeatedly performed, the height of the vertical portion 203a of the body 203 eventually becomes shorter than that of a vertical portion 231b of the hole 231 in the auxiliary cap 221. At this time, when the die 201 is attached to a punching press, an auxiliary member may be interposed between the die body 203 and a die holder of a punching press. It is preferable that the projecting height H of the ridge portion 209 relative to the upper surface 223 is equal to 0.2 to 0.5mm and the width A of the horizontal plane surface of the ridge portion 209 is equal to 0.1 to 0.2mm. The horizontal cross-sectional shape of the die hole 205 may be circular, rectangular or the like. The auxiliary cap 221 is made of a metal and preferably of the same metal as the die body 203. As is understood from the foregoing description, in the die unit of the present invention, the ridge portion projecting upwardly above the upper surface of the die body or auxiliary cap is provided in the upper peripheral portion of the die hole. Therefore, when a punching is performed on a workpiece, the chamfering portion is formed along the perimeter of the punched hole. Accordingly, the burr B produced around the punched hole Wa is located inside the chamfering portion so as not to project downwardly below the lower surface of the workpiece W. Accordingly, burr removing operations after punching operations are no longer necessary.

Claims: A die unit for performing punching operations in cooperation with a punch unit (13) that includes a punch body (17) comprising: a die body (203) formed at its substantially center portion with a die hole (205) extending in an axial direction for receiving a cutting edge of the punch body (17), on its outer peripheral surface with an inclined surface portion (219) spreading outwards downwardly, and at its upper portion with a ridge portion (209); and an auxiliary member (221) detachably fitted on the die body (203), the auxiliary member (221) being formed with a hole portion (231) engaging with said inclined portion (219) of the die body (203), and with an upper surface portion (223) extending in a plane normal to the axial direction so as to support a workpiece during the punching operations; wherein the auxiliary member (221) is so designed that the ridge portion (209) projects upwardly above the upper surface portion (223) of the auxiliary member (221) when the auxiliary member (221) is fitted on the die body (203), characterised in that the auxiliary member (221) is in the form of a cap, in that the die body (203) is a one piece element, and in that the inclined surface portion (219) delimits the outer shape of the ridge portion (209) so that the upper portion is constituted solely by the ridge portion (209) which solely projects upwardly above the upper surface portion (223) of the auxiliary member (221) when the auxiliary member is fitted on the die body. The die unit as recited in Claim 1, wherein the ridge portion (209) is formed in a wedge-shape in cross-section. The die unit as recited in Claim 1, wherein the ridge portion (209) is formed with a horizontal plane surface extending substantially parallel to the upper surface portion (223) of the auxiliary cap member (221). The die unit as recited in Claim 3, wherein the height of the ridge portion (209) above the upper surface portion (223) of the auxiliary cap member (221) is between 0.2 and 0.5mm, and the width of the horizontal plane surface of the ridge portion (209) is between 0.1 and 0.2mm. A method of extending the working life of a die unit according to claim 1 said method comprising: (a) detaching the auxiliary cap member (221) from the die body (203) when the ridge portion (209) of the die unit is worn away by punching operations; (b) grinding the inclined surface portion (219) of the die body (203) to form a new inclined surface portion that is parallel to the old inclined surface portion; and (c) attaching the auxiliary cap member (221) to the ground die body (203).

Inventors: IWAMOTO MASAMI, IWAMOTO, MASAMI
Applicants: AMADA METRECS COMPANY LTD, AMADA METRECS COMPANY, LIMITED
Application year: 1996
Main classification: B21D28
IPC codes: B21D28