JP4392125B2 - Forging die equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a forging die apparatus in which a forging material is loaded in a cavity and the forging material is forged under the pressurizing action of a punch.
[0002]
[Prior art]
Conventionally, a forging material is loaded into a cavity formed in an upper die and a lower die joined together, and a forging material is forged into a predetermined shape by applying pressure to the forging material via a punch. A mold apparatus for molding is known.
[0003]
Using this type of mold apparatus, for example, an outer ring member (outer cup) of a constant velocity joint used for driving a vehicle wheel is manufactured by a cold forging method. The outer ring member includes a cup-shaped or cylindrical cup portion and a shaft portion formed integrally with the cup portion, and extends along the axial direction on the inner peripheral surface of the cup portion. Ball grooves or track grooves are formed, and balls or rollers are provided to roll along the ball grooves and the track grooves.
[0004]
The process for forging the outer ring member by the cold forging method according to the prior art will be schematically described below.
[0005]
First, a cylindrical work piece (forging material) connected to a predetermined length is subjected to a spheroidizing annealing treatment, and subsequently a lubricating conversion coating such as a phosphate coating is formed on the surface by a bonderite treatment. A shaft portion extending along the axial direction is formed by performing forward extrusion with the first forging die (first step).
[0006]
Next, a second step of performing upsetting on the unprocessed portion of the workpiece via another second forging die different from the first forging die is performed. And, for the molded product subjected to the upsetting, a low temperature annealing process for removing stress, a shot blasting process for removing oxide scale and the like generated during the low temperature annealing process, and an outer surface of the workpiece Bonderite treatment for forming a chemical conversion coating for lubrication is performed.
[0007]
Subsequently, a third step is performed on the workpiece, in which a cup portion is formed and backward extrusion is performed to form a ball groove or a track groove on the inner peripheral surface thereof. This backward extrusion molding is performed by another third forging die different from the first and second forging dies. The molded product subjected to the backward extrusion molding is subjected to a low-temperature annealing process to soften the workpiece, and then the oxide scale and the like are removed by shot blasting, and further, a bondelite process is performed to obtain lubricity at the time of molding. .
[0008]
Finally, the ironing process (final sizing molding) for finishing to the final product shape is performed as the fourth step by using another fourth forging die different from the first to third forging die. A finished product is obtained.
[0009]
As described above, in the forging method according to the prior art, various forging processes are performed on the workpiece using the first to fourth forging dies having different structures, and various processing operations are performed during the forging process. Made.
[0010]
Before performing the ironing process in the fourth step, the low temperature annealing process, the shot blasting process, the bonderite process, etc. are performed when the ironing process is continuously performed after the third process in which the rear extrusion is performed. This is because cracks may occur on the inner surface of the cup portion during ironing. For this reason, in the forging method according to the prior art, various processes such as a low-temperature annealing process are required before performing the ironing process.
[0011]
[Problems to be solved by the invention]
The present invention omits the fourth step which is the ironing process (final sizing molding) to finish the final product shape, and also omits various processes such as a low-temperature annealing process before the ironing process. To provide a forging die apparatus capable of greatly reducing the manufacturing cost by simplifying the manufacturing process and eliminating the need for an expensive fourth forging die used in the fourth step. Objective.
[0012]
In order to achieve the above object, the present invention provides an apparatus for forging and forming an outer ring member for a constant velocity joint by applying a pressing force to a forging material charged in a cavity.
A mold member formed with a cavity filled with the forging material;
A punch for applying a pressing force to the forging material loaded in the cavity to perform backward extrusion ,
With
On the cavity surface of the mold member, between the first molding part and the second molding part, the first molding part and the second molding part that are spaced apart by a predetermined distance along the axial direction and form the product accuracy of the outer shape. A cavity concave portion formed in a substantially stepped shape with three or more steps is provided, the central portion along the axial direction of the mold member being deepest and gradually shallower toward both end sides;
On the side surface of the punch, there is provided a punch recess formed in a substantially stepped shape having a cross section of three or more steps where the central portion along the axial direction of the mold member is deepest and gradually shallower toward both end sides,
When the punch reaches the lowering end position, the cavity concave portion and the punch concave portion are arranged at substantially opposite positions via the deformed forging material .
[0013]
In this case, each of the punch recess and the cavity recess may be formed in a substantially stepped cross section with an equal groove width .
[0014]
In this case, the punch recesses and the cavity recesses may be formed unevenly such that the groove width gradually decreases from the center toward both ends.
[0015]
In this case, the center point of the punch recess may be set at a position deviated from the center point of the length along the axial direction of the punch toward the convex side .
[0017]
According to the present invention, when the rear extrusion is performed by the punch, the inner shape accuracy is maintained by correcting by the punch-side concave portion formed to allow for the punch deflection amount (distortion amount), and the die member deflection. The accuracy of the outer shape is maintained by correction by the concave part on the mold member side that is formed in anticipation of the amount (distortion amount). Therefore, the inner shape and the outer shape accuracy of the product are simultaneously ensured under the cooperative action of the punch side recess and the mold member side recess.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of a forging die apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.
[0019]
In FIG. 1, reference numeral 10 indicates a forging die apparatus according to an embodiment of the present invention.
[0020]
The forging die apparatus 10 includes a first die plate 12 and a second die plate 14, and a press-fitting ring 18 formed thick on the first die plate 12 via a fixing member (not shown). Is fixed.
[0021]
In the hole of the press-fit ring 18, an insert member 20 formed in a cylindrical shape is fitted. In this case, the outer diameter of the insert member 20 is set slightly larger than the inner diameter of the press-fit ring 18, and the insert member 20 is fitted into the hole of the press-fit ring 18 by an interference fit.
[0022]
An upper die 22 and a lower die 24 formed in a divided manner are integrally coupled along the axial direction inside the insert member 20, and forging described later is placed inside the upper die 22 and the lower die 24. A cavity in which a working material is loaded is formed. The upper die 22 and the lower die 24 function as mold members.
[0023]
As shown in FIG. 1, a first ring body 30 in which a hole 28 for guiding a punch 26 is formed is joined to the upper surface of the upper die 22, and the first member 30 is joined to the upper surface of the insert member 20. A large-diameter second ring body 32 that is externally fitted to one ring body 30 is joined, and a large-diameter third ring body 34 that is externally fitted to the second ring body 32 is inserted into the annular recess of the press-fit ring 18. They are joined together.
[0024]
In this case, the third ring body 34 is fastened to the press-fit ring 18 so that the second ring body 32 is externally fitted, whereby the tapered surface 34 a formed on the third ring body 34 is formed on the second ring body 32. The force which presses the 1st ring body 30 and the 2nd ring body 32 toward the downward side acts on the reverse taper surface 32a formed.
[0025]
An annular guide groove (not shown) for guiding the punch 26 when the punch 26 is inserted may be formed in the upper portion of the hole portion 28 of the first ring body 30.
[0026]
On the lower side of the cavity formed by the upper die 22 and the lower die 24, a knockout pin 36 for extruding a forged product is disposed along a hole 38 formed in the first die plate 12 so as to advance and retract. The The cavity is filled with a secondary molded product described later as a forging material.
[0027]
The inner peripheral surface of the upper die 22 is composed of a set of substantially cylindrical surfaces that are spaced apart from each other by a predetermined distance along the axial direction. As shown in FIG. A plurality of portions formed between the first molding portion 40a and the second molding portion 40b in a substantially stepped manner, and taking into account the amount of deflection of the upper die 22 and the lower die 24 when forging. First to fourth recesses (mold member side recesses) 42a to 42d.
[0028]
As shown in FIG. 3, the first to fourth recesses 42 a to 42 d extend by a predetermined length along the axial direction between the first molding portion 40 a and the second molding portion 40 b, and in the circumferential direction. Along the entire circumference. Also, the groove widths of the first to fourth recesses 42a to 42d may be formed substantially equally as shown in FIG. 3, or the center first recess 42a as shown in FIG. Alternatively, the groove width may be non-uniformly formed so as to gradually decrease from the fourth recess 42d on the end portion side to the end portion side. Furthermore, as shown in FIG. 5, a single recess 42 may be formed between the first molding part 40a and the second molding part 40b.
[0029]
The concave portions 42, 42a to 42d are formed in a stepped shape or a curved shape with a gentle cross section from the center portion toward the first and second molding portions 40a, 40b on both ends in view of the amount of deflection at the time of molding ( (See FIG. 6) or a composite shape thereof.
[0030]
In this case, as shown in FIG. 3, the first concave portion 42a formed in the substantially central portion is formed in a concave shape by about 0.2 mm with respect to the first molded portion 40a and the second molded portion 40b. The second concave portion 42b adjacent to the first concave portion 42a is formed in a concave shape by about 0.15 mm, the third concave portion 42c adjacent to the second concave portion 42b is formed in a concave shape by about 0.1 mm, and The 4th recessed part 42d adjacent to the 3rd recessed part 42c is good to be formed in concave shape only about 0.05 mm.
[0031]
As shown in FIG. 1, an upper portion spaced apart from the press-fitting ring 18 by a predetermined distance is connected to a ram (not shown) of a mechanical press (not shown). An elevating member 44 that is displaced along is provided. A punch 26 is fixed to the elevating member 44 through a jig 46, and a guide sleeve 48 formed of a cylindrical metal material is fitted on a predetermined portion of the outer peripheral portion of the punch 26.
[0032]
As shown in FIG. 7, graphite 49 is embedded in the guide sleeve 48 through a plurality of holes, and the lubrication characteristics when inserted into the holes 28 of the first ring body 30 are improved. Can be held. In this case, the diameter on the outer peripheral side of the guide sleeve 48 fitted on the punch 26 is set to be slightly larger than the diameter on the inner peripheral side of the hole portion 28 of the first ring body 30.
[0033]
When the guide sleeve 48 is formed of a metal material such as SKD11 made of Rockwell hardness HRC58 to 60, and the first ring body 30 is formed of a metal material harder than the guide sleeve 48, for example. Is preferred.
[0034]
The punch 26 is provided so as to be displaceable in the vertical direction integrally with the elevating member 44 under the guiding action of a plurality of guide means (not shown) provided upright on the first die plate 12. For example, the punch 26 has a Rockwell hardness HRC62. It is preferable to be formed of a metal material such as SKH51 consisting of ˜64.
[0035]
As shown in FIGS. 8 and 10, three protrusions 50 a to 50 c are provided at one end of the punch 26 at a spacing angle of about 120 degrees along the circumferential direction. The portions 50 a to 50 c are formed so as to extend by a predetermined length along the axial direction of the punch 26. The three protrusions 50a to 50c correspond to guide grooves (track grooves) (not shown) formed on the inner wall surface of the cup part constituting the constant velocity joint, and the protrusions 50a to 50c of the punch 26 are formed. The three guide grooves extending along the axial direction of the cup portion and spaced apart at equal angles along the circumferential direction are formed by 50c. A chamfered portion 52 that is chamfered in a compound curve shape is formed over the entire circumference on the tip surface of the punch 26 that is one end side of the protruding portions 50a to 50c.
[0036]
FIG. 9 is a partially omitted enlarged plan view of one protrusion 50a (50b, 50c) as viewed from above, and one end side of this protrusion 50a (50b, 50c) (the tip side of the punch 26). In this, a molding land portion 54 formed of a convex portion having a predetermined width B is formed along the circumferential direction of the punch 26. The molded land portion 54 is formed over the entire circumference including the three protrusion portions 50a to 50c and the groove portions 56a to 56c between the adjacent protrusion portions 50a to 50c.
[0037]
As shown in FIG. 9, a convex portion 58 having a predetermined width C larger than the molding land portion 54 is formed in an intermediate portion of the punch 26 adjacent to the guide sleeve 48, and the convex portion 58 is formed in the molding portion 58. Similarly to the land portion 54, the land portion 54 is formed over the entire circumference including the three ridge portions 50a to 50c and the groove portions 56a to 56c between the adjacent ridge portions 50a to 50c.
[0038]
As shown in FIG. 3, between the molding land portion 54 and the convex portion 58, three protruding portions 50 a to 50 c and grooves 56 a to 56 c between adjacent protruding portions 50 a to 50 c are included. First to fourth recesses (punch side recesses) 60a to 60d having stepped cross sections are formed over the entire circumference, and the first to fourth recesses 60a to 60d are formed by forging the forging material by the forming land portion 54. It functions to increase product accuracy as a recess that allows for the amount of distortion.
[0039]
The first to fourth recesses 60a to 60d extend between the molding land portion 54 and the projection 58 by a predetermined length along the axial direction, and are formed over the entire circumference along the circumferential direction. Further, the groove widths of the first to fourth recesses 60a to 60d may be formed substantially equally as shown in FIG. 3, or the center first recess 60a as shown in FIG. Alternatively, the groove width may be non-uniformly formed so as to gradually decrease from the first concave portion 60d to the end portion side. Further, as shown in FIG. 5, a single concave portion 60 may be formed between the molding land portion 54 and the convex portion 58.
[0040]
The shape of the recesses 60, 60a to 60d is a stepped or curved cross section that is gentle from the central part toward the forming land part 54 and the convex part 58 on both ends from the center part (see FIG. 6). Or a composite shape thereof.
[0041]
In this case, as shown in FIG. 3, the first concave portion 60a formed in the substantially central portion is formed in a concave shape by about 0.3 mm with respect to the molding land portion 54 and the convex portion 58, and the first concave portion The second concave portion 60b adjacent to the second concave portion 60b is formed in a concave shape by about 0.2 mm, and the third concave portion 60c adjacent to the second concave portion 60b is formed in a concave shape by about 0.1 mm. The adjacent fourth recess 60d may be formed in a concave shape by about 0.05 mm.
[0042]
In addition, the first to fourth recesses 42a to 42d formed in the upper die 22 in anticipation of the amount of deflection of the mold member during molding, and the first portion formed in the punch 26 in anticipation of the amount of deflection of the punch 26 during molding. The first to fourth recesses 60a to 60d are each formed in a substantially symmetrical shape as shown in FIGS. 3 to 6, but may be formed in an asymmetric shape in cross section.
[0043]
Further, the upper die 22 and the lower die 24 are firmly held by the insert member 20 and the press-fit ring 18 that are fitted externally, and the inner wall surfaces of the upper die 22 and the lower die 24 are slightly on the forging material side during forging. Therefore, the depths of the first to fourth recesses 42a to 42d on the upper die 22 side are slightly shallower than the first to fourth recesses 60a to 60d on the punch 26 side.
[0044]
Furthermore, as shown in FIGS. 3 to 6, the length along the axial direction of the center point C <b> 1 of the deepest first recess 60 a and the punch 26 among the first to fourth recesses 60 a to 60 d. The center point C2 of the first recess 60a is provided so as to be deviated toward the convex portion 58 side. By offsetting the center point C1 of the first recess 60a toward the protrusion 58 by a predetermined distance from the center point C2 of the punch 26 itself, the meat of the forging material extruded rearward during forging is convex. The plastic flow toward the portion 58 side is promoted, and the deflection amount of the punch 26 can be suitably corrected.
[0045]
In this case, the first to fourth recesses 60a to 60d and the protrusion 58 formed over the entire circumference including the three protrusions 50a to 50c and the grooves 56a to 56c between the adjacent protrusions 50a to 50c, The distortion of the punch 26, which is the upper die, is transferred to the forging material, and the accuracy correction unit 62 that forms product accuracy is configured.
[0046]
The forging die apparatus 10 according to the embodiment of the present invention is basically configured as described above. Next, the operation, action, and effect thereof will be described. In addition, it demonstrates below by taking the case where the outer ring member which comprises a constant velocity joint as a forging product is forge-molded as an example.
[0047]
First, the forging process for the forging material will be described with reference to FIGS.
[0048]
By subjecting the cylindrical billet 70 shown in FIG. 12A to primary forging by a first forging die (not shown), primary molded products 72 having different diameters through the intermediate stepped portion. Is obtained (see FIG. 12B).
[0049]
Subsequently, after preforming the primary molded product 72 to obtain a preform 74 (see FIG. 12C), the preform 74 is further used by another second forging die (not shown). On the other hand, by performing the second forging, a second molded product 78 (see FIG. 12D) including the cup portion 76a and the shaft portion 76b is obtained.
[0050]
The forging die apparatus 10 according to the present embodiment finishes the final product shape by further performing the third forging by using the second molded product 78 as a forging material 78.
[0051]
First, as a preparatory work, it is assumed that the punch 26 is previously positioned with respect to the cavity formed by the upper die 22 and the lower die 24. Then, under the driving action of a mechanical press (not shown), the punch 26 is lowered integrally with the elevating member 44 connected to the ram (not shown), and the forging is started when the state shown in FIG.
[0052]
When the punch 26 is lowered integrally with the elevating member 44, a lateral load is suitably absorbed by a plurality of guide means (not shown) provided between the elevating member 44 and the first die plate 12. The punch 26 is smoothly inserted into the center of the hole 28 of the first ring body 30.
[0053]
When forging is started, a guide sleeve 48 fitted on a part of the outer peripheral surface of the punch 26 is an annular guide groove (not shown) formed at the upper end of the hole 28 of the first ring body 30. The punch 26 and the guide sleeve 48 are integrally displaced while being inserted into the hole portion 28 of the first ring body 30 as the punch 26 descends.
[0054]
In this way, the punch 26 is lowered and reaches the molding end position shown in FIG. 11 from the molding start position shown in FIG. 1, and the forging material is passed through the punch 26, the upper die 22 and the lower die 24. Forging is performed on 78, and the forging material 78 plastically flows along the shape of the cavity.
[0055]
That is, the extrusion land is formed on the inner wall surface of the forging material 78 by the forming land portion 54 formed on one end side of the punch 26, and the meat of the forging material 78 extruded by the forming land portion 54 is the punch 26. The accuracy is corrected and maintained by the convex portion 58 that flows along the first to fourth concave portions 60a to 60d and that transfers the distortion of the punch 26 to the forging material formed on the guide sleeve 48 side.
[0056]
In other words, even when the distortion of the punch 26 at the time of forging is transferred to the forging material 78 by the forming land portion 54, the first to fourth recesses 60a to 60a that allow for the deflection amount of the punch 26 are considered. 60d corrects the accuracy of the product in the middle of molding, and finally, a product (finished product) including a shape such as a guide groove (track groove) by the convex portion 58 continuous to the first to fourth concave portions 60a to 60d. The inner shape accuracy of the is secured.
[0057]
At the same time, upset molding and backward extrusion molding are performed on the outer peripheral surface of the forging material 78 by the first molding portion 40a, the second molding portion 40b, and the first to fourth recess portions 42a to 42d formed in the upper die 22. The
[0058]
That is, even when the distortion of the die member at the time of forging is transferred to the forging material 78, the first to fourth recesses 42 a to 42 d allow for the amount of deflection of the upper die 22 and the lower die 24. The amount of distortion is corrected, and finally, the outer shape accuracy of the product is formed by the first molding portion 40a and the second molding portion 40b provided adjacent to the first to fourth recesses 42a to 42d.
[0059]
After the forging is completed in this way, the punch 26 ascends to a predetermined position integrally with the elevating member 44 connected to a ram (not shown) under the driving action of a mechanical press (not shown). 26 and the guide sleeve 48 are separated from the hole 28 of the first ring body 30 and are in a standby state for the next process. Then, a forged product having finished product accuracy is taken out under the displacement action of the knockout pin 36.
[0060]
In the present embodiment, the first to fourth recesses 60a to 60d are formed between the molding land portion 54 and the projection 58 of the punch 26 in consideration of the deflection amount of the punch 26, which has a stepped or curved cross section. 60d and first to fourth recesses 42a to 42d formed between the first molding part 40a and the second molding part 40b of the upper die 22 in consideration of the amount of deflection of the mold member. The amount of distortion is corrected under the cooperative action with 42d, and the inner shape accuracy and outer shape accuracy of the product are simultaneously secured.
[0061]
Therefore, in the present embodiment, it is possible to omit the fourth step, which is a conventional ironing process (final sizing molding) to finish the final product shape, and to perform a low-temperature annealing process before the ironing process, etc. The various processes can be omitted to simplify the manufacturing process. As a result, in the present embodiment, an expensive fourth forging die (not shown) that has been conventionally used in the fourth step becomes unnecessary, and the manufacturing cost can be greatly reduced.
[0062]
In the present embodiment, the first to fourth recesses 42a to 42d are formed along the circumferential direction on the inner peripheral surface of the upper die 22, and the circumferential surface excluding the first to fourth recesses 42a to 42d. Since this becomes a contact surface with the forging material 78, the molding load during forging can be reduced, and the durability of the upper die 22 and the lower die 24 can be improved.
[0063]
Furthermore, in this embodiment, the description is based on a tripart type constant velocity joint as a finished product, but it is also applicable to a bar field type constant velocity joint (not shown) in which a ball rolling groove is formed in the cup. can do.
[0064]
In the present embodiment, the outer ring member constituting the constant velocity joint is used as the forging material, but the present invention is not limited to this. For example, the inner ring member such as a stepped part (not shown), a stepped gear, etc. Needless to say, the present invention can be applied to various forged products that require both shape accuracy and external shape accuracy.
[0065]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0066]
That is, the inner shape and the outer shape accuracy of the product are simultaneously secured under the cooperative action of the concave portion formed on the punch for correcting the distortion amount of the punch and the concave portion formed on the mold member for correcting the distortion amount of the mold member. For this reason, the fourth step, which is the ironing process (final sizing molding) for finishing the final product shape, which has been conventionally performed, is omitted, and various processes such as a low-temperature annealing process before the ironing process are performed. Can be omitted, and the manufacturing process can be simplified.
[0067]
In addition, in the present invention, the manufacturing cost can be greatly reduced by eliminating the need for an expensive fourth forging die conventionally used in the fourth step.
[Brief description of the drawings]
FIG. 1 is a partially omitted longitudinal sectional view of a forging die apparatus according to an embodiment of the present invention.
FIG. 2 is a partially enlarged view showing an inner wall surface of an upper die constituting the forging die device.
FIG. 3 is a partially enlarged longitudinal sectional view showing stepped recesses formed in a punch and an upper die, respectively.
4 is a partially enlarged longitudinal sectional view showing a first modified example of the recess shown in FIG. 3. FIG.
FIG. 5 is a partially enlarged longitudinal sectional view showing a second modification of the recess shown in FIG. 3;
6 is a partially enlarged longitudinal sectional view showing a third modified example of the recess shown in FIG. 3. FIG.
FIG. 7 is a longitudinal sectional view of a punch constituting the forging die device.
FIG. 8 is a partially omitted perspective view of the punch.
FIG. 9 is a partially omitted enlarged plan view of the punch.
10 is a view as seen from the direction of arrow A in FIG.
FIG. 11 is an operation explanatory view showing a state in which the punch is lowered and forging is completed.
FIGS. 12A to 12D are explanatory views showing a forging process for a forging material, respectively. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Forging die apparatus 12, 14 ... Die plate 18 ... Press-fit ring 20 ... Insert member 22 ... Upper die 24 ... Lower die 26 ... Punch 40a, 40b ... Molding part 42, 42a-42d, 60, 60a-60d ... Recess 48 ... Guide sleeve 50a-50c ... Projection 52 ... Chamfer 54 ... Molding land 56a-56c ... Groove 58 ... Convex 62 ... Accuracy correction part 78 ... Forging material

Claims (4)

In a device for forging by applying pressure to the forging material loaded in the cavity, and forming an outer ring member for a constant velocity joint,
A mold member formed with a cavity filled with the forging material;
A punch for applying a pressing force to the forging material loaded in the cavity to perform backward extrusion,
With
On the cavity surface of the mold member, between the first molding part and the second molding part, the first molding part and the second molding part that are spaced apart by a predetermined distance along the axial direction and form the product accuracy of the outer shape. is formed, cavities formed gradually shallower three or more cross section stepped central portion in which the axial direction is towards the deepest both ends of the mold member is provided,
Wherein the side surface of the punch, the punch recess formed gradually shallower three or more cross section stepped central portion in which the axial direction is towards the deepest both ends of the mold member is provided,
When the punch reaches the lowering end position, the cavity concave portion and the punch concave portion are disposed at substantially opposite positions with the deformed forging material interposed therebetween. The apparatus of claim 1 .
The punch recess and the cavity recess, respectively, forging mold, characterized in that it is formed in a substantially stepped such groove width GaHitoshi device. The apparatus of claim 1.
The forging die device, wherein the punch recess and the cavity recess are formed unevenly such that the groove width gradually decreases from the center toward both ends. In the apparatus of any one of Claims 1-3,
The forging die apparatus characterized in that the center point of the punch recess is set at a position deviated to the convex side with respect to the center point of the length along the axial direction of the punch.

Images