Patent Publication Number: US-2023147754-A1

Title: Metalworking apparatus and metalworking method

Description:
TECHNICAL FIELD 
     The present invention relates to a metalworking apparatus and a metalworking method. 
     BACKGROUND ART 
     A conventional metalworking apparatus that forms a hole in a metal plate by a shear-punching method using a punch and a die has been known (see Patent Literature 1 or the like, for example). In such an apparatus, the punch has an edge with a curved surface and a distal end with a conically recessed surface. This ensures that the shear cut surface of the hole does not crack or fracture. 
     PRIOR ART REFERENCE 
     Patent Document 
     
         
         Patent Literature 1: JP2002-120025A 
       
    
     SUMMARY OF INVENTION 
     Problem to be Solved 
     With conventional metalworking tools, rollover occurs by which a curve is radially formed at a peripheral edge of a punched hole. Also, in the case of boring a plurality of holes adjacently to each other, a metallic material between the holes sinks in, and thereby causes material drag. 
     Thus, there has been a demand for a further improvement to reduce rollover and material drag. 
     An object of the present invention is to provide a metalworking apparatus and a metalworking method capable of reducing rollover and material drag. 
     Means to Solve the Problem 
     A metalworking apparatus of the present invention includes a forging tool configured to work-harden a to-be-opened portion of a workpiece through forging, and a punching tool configured to form an opening portion in the to-be-opened portion by punching. The punching tool has an insertion portion that has a diameter equal to a diameter of the opening portion, and a shoulder portion which is joined to the insertion portion and has a diameter which is larger than a diameter of the insertion portion and increases as the shoulder portion extends toward a proximal end of the punching tool. When forming the opening portion by punching, the punching tool is inserted to such a position that the shoulder portion contacts a work-hardened portion remaining at an inner peripheral edge of the opening portion from an inner side surface. 
     Advantageous Effects of the Invention 
     According to the present invention, a metalworking apparatus and a metalworking method capable of reducing rollover and material drag are provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic cross-sectional view of a main part, describing a forging step with a forging tool in a metalworking apparatus and a metalworking method in an embodiment of the present invention. 
         FIG.  2    is a schematic cross-sectional view of a main part, describing a punching step with a punching tool in the embodiment. 
         FIG.  3    is a schematic cross-sectional view of a main part, describing a striking step with a striking tool in the embodiment. 
         FIG.  4    is a schematic cross-sectional view of a main part of a metal plate, showing that an opening portion has been processed to be flat in the embodiment. 
         FIG.  5    is a plan view of a metal plate in which plural opening portions are disposed adjacently to one another in the embodiment. 
         FIG.  6    is a cross-sectional view of the metal plate, taken at a position along the VI-VI line of  FIG.  5    in the embodiment. 
         FIG.  7    shows a comparative example and is a cross-sectional view of a metal plate taken at a position corresponding to that in  FIG.  6   . 
         FIG.  8    is a side view of a main part, showing an example of the punching tool. 
         FIG.  9 A  shows a modification of the forging tool of the embodiment, and is a schematic cross-sectional view of a main part, showing that a metal plate is work-hardened through forging with a forging tool having a flat end surface. 
         FIG.  9 B  is a schematic cross-sectional view of a forging tool having a tapered conical distal end with no flat portion therearound, showing how to use it. 
         FIG.  9 C  is a schematic cross-sectional view of a forging tool having a flat end surface with an inclined surface formed by chamfering the outer peripheral edge of the flat end surface, showing how to use it. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     An embodiment of the present invention will be described below with reference to the drawings as appropriate. Identical constituent components are denoted by the same reference sign and overlapping description is omitted. 
     In a metalworking apparatus  1 , a plate material  2 , which is a workpiece, is fixed on a clamping jig not shown. In this state, steps are sequentially performed. The steps include a forging step of striking and thus forging a to-be-opened portion  5  to work-harden the to-be-opened portion  5 , a punching step of forming an opening portion  3  in the forged to-be-opened portion  5  of the plate material  2  by punching, and a striking step of striking and flattening a small protrusion  6  appearing around the punched opening portion  3  with a striking tool. 
     Through these steps, the metalworking apparatus  1  of the present embodiment forms the plural opening portions  3  through the plate material  2  having a thin plate shape as shown in  FIG.  5    in an out-of-plane direction. As a result, the plate material  2  turns into a plate-shaped product  4  in which the opening portions  3  having a 3×4 formation or total of 12 are formed in a matrix pattern at equal intervals both vertically and horizontally (see  FIG.  5   ). In the present embodiment, the relation among the hole diameter, a plate thickness, and a pitch of the opening portions  3  is set such that the hole diameter is less than the plate thickness, and the pitch is less than or equal to three times the hole diameter. 
     Note that a case of forming a single opening portion  3  in the plate material  2  is mainly and exemplarily shown in the present embodiment for simple description. Descriptions for the other opening portions  3  are omitted, which are formed in a similar manner to the single opening portion  3 . 
     First, a configuration of a forging tool  10  to be used in the forging step will be described. 
     The metalworking apparatus  1  is provided with the clamping jig not shown for horizontally placing and fixing the plate material  2 , and a slide movement member. While the forging tool  10  is mounted on the slide movement member, the slide movement member moves the forging tool  10  along a slide direction (a vertical direction in  FIG.  1   ). 
     The forging tool  10  is provided with a pressing portion  11  at a lower end portion, and a flat portion  12  located around the peripheral edge of the pressing portion  11 . 
     The pressing portion  11  in the present embodiment has a distal end  11   a  provided to protrude in a tapered conical shape such that the lowest point of the pressing portion  11  is on a central axis S at the center in the radial direction. 
     When the forging tool  10  is mounted on the slide movement member, the distal end  11   a  of the pressing portion  11  faces the to-be-opened portion  5  of the plate material  2  horizontally fixed by the clamping jig. The to-be-opened portion  5  will be the opening portion  3  when the plate material  2  is completed as the plate-shaped product  4 . 
     Then, as the slide movement member is moved downward in the slide direction, the conical distal end  11   a  of the pressing portion  11  of the forging tool  10  comes into contact with a portion  2   a  of the upper surface of the plate material  2  and presses the to-be-opened portion  5  from above. 
     The pressing portion  11 , which is formed in a tapered conical shape, pushes away a metallic material presented in the to-be-opened portion  5  radially outward from the radial center. A portion  2   b  thus pushed away is work-hardened (base-material-hardened) and a density of the plate material  2  increases as compared to that of the other portion of the plate material  2 . 
     A radial dimension c 2  of a work-hardened portion at the peripheral edge of the to-be-opened portion  5  is larger than a radial dimension c 1  of the pressing portion  11  (c 1 &lt;c 2 ). 
     Also, the flat portion  12 , which has an annular shape, is provided around the pressing portion  11  in the present embodiment. The flat portion  12  is provided to be parallel to the plate material  2  mounted on the clamping jig. When the plate material  2  is forged by the pressing portion  11 , the flat portion  12  comes into contact with the peripheral edge of the to-be-opened portion  5  from above. 
     The flat portion  12  contacts the peripheral edge of the to-be-opened portion  5  and presses the plate material  2  downward from above in the out-of-plane direction toward the clamping jig supporting the plate material  2  from below. This prevents the metallic material at the peripheral edge of the to-be-opened portion  5  from moving upward in the out-of-plane direction, and thus promotes the work-hardening. 
     The metalworking apparatus  1  of the present embodiment includes a punching tool  20  to be used in the punching step, as shown in  FIG.  2   . The punching tool  20  forms the opening portion  3  in the to-be-opened portion  5  of the plate material  2  by punching. 
     The punching tool  20  integrally has: a cylindrical insertion portion  22  located on a distal end (lower end) side and having a diameter substantially equal to the radial dimension c 1  of the pressing portion  11  of the forging tool  10 ; a proximal end portion  24  on a proximal end (upper end) side being larger in diameter than the insertion portion  22  and mounted on the slide movement member to move with slide movement in the up-down direction; and a shoulder portion  26  provided between the insertion portion  22  and the proximal end portion  24  and joined to the upper side of the insertion portion  22  in the slide direction (up-down direction). 
     Of these, an inclination angle α 2  of the shoulder portion  26  is smaller than an inclination angle α 1  of the pressing portion  11  shown in  FIG.  1    (α 1 &gt;α 2 ). In the present embodiment, α 1 =approximately 45 degrees, and α 2 =approximately 10 degrees. 
     As shown in  FIG.  8   , a curved surface  28  is formed on the shoulder portion  26  in the present embodiment. The curved surface  28  is formed to gradually increase in diameter outward as the shoulder portion  26  extends from the insertion portion  22  toward the proximal end portion  24 . 
     A rate of increase in diameter of the curved surface  28  (an increased dimension r in the radial direction/a dimension h in the slide direction) is set such that the rate gradually increases as the curved surface  28  extends from the insertion portion  22  toward the proximal end portion  24 . 
     For example, assuming that sections of the curved surface  28  are given uniform dimensions in the slide direction (h 1 =h 2 =h 3 ), the amount of increase in the radial direction increases gradually at each section (r 1 &lt;r 2 &lt;r 3 ). 
     Thus, at the portion joined to the insertion portion  22 , the curved surface  28  has the smallest rate of increase in diameter and is flush with the side surface of the insertion portion  22 . Also, the curved surface  28  has the largest rate of increase in diameter at the portion joined to the proximal end portion  24 . 
     As shown in  FIG.  2   , the insertion portion  22  of the punching tool  20  is brought into contact with the work-hardened portion of the to-be-opened portion  5  to form the opening portion  3  by punching. At this time, it is preferable that the opening portion  3  is made within the work-hardened region in the to-be-opened portion  5 . 
     When the insertion portion  22  of the punching tool  20  is inserted in the slide direction, the insertion portion  22  punches the plate material  2  toward its lower surface while leaving the metallic material which has an increased density and is work-hardened around the insertion portion  22 . 
     When the shoulder portion  26  of the punching tool  20  comes into contact with an inner side surface  16  of the opening portion  3 , the shoulder portion  26  pushes the metallic material around the peripheral edge of the opening portion radially outward while urging the metallic material to be pushed out upward from the opening portion  3 . 
     Thus, the metallic material around the peripheral edge of the opening portion, which is urged to move downward in the slide direction by being dragged with the punching tool  20 , remains at its current position. This reduces the occurrence of rollover and material drag at the peripheral edge of the opening portion  3 . 
     Also, the metalworking apparatus  1  of the present embodiment includes a striking tool  30  to be used in the striking step, as shown in  FIG.  3   . The striking tool  30  slides in the vertical direction along with the slide movement member to strike and flatten a small protrusion  6  appearing around the opening portion  3  from above. 
     For example, as shown in  FIG.  2   , depending on the amount of insertion of the shoulder portion  26  when the opening portion  3  is punched with the punching tool  20 , a small protrusion  6  protruding upward from the peripheral edge of the opening portion  3  may appear. 
     The striking tool  30  has a flat striking surface  32  on the lower side thereof facing the plate material  2 . 
     The striking surface  32  is provided to be parallel to an upper surface  2   c  of the plate material  2  fixed by the clamping jig, and is capable of evenly striking and flattening the small protrusion  6  appearing around the opening portion  3  by sliding the slide movement member downward. 
     The punching tool  20  is pulled out of the opening portion  3 . By being struck with the striking tool  30  from above, the small protrusion  6  appearing around the opening portion  3  gets crushed to the same height as the upper surface  2   c , and thus becomes flat (see  FIG.  4   ). 
     In the present embodiment, as shown in  FIG.  5   , the plate-shaped product  4  is formed in which the opening portions  3  having a 3×4 formation or total of 12 are formed in a matrix pattern at equal intervals both vertically and horizontally. 
     In the punching step, as shown in  FIG.  6   , the amount of movement of each slide movement member in the slide direction is controlled to adjust the amount of insertion of the corresponding punching tool  20  into the corresponding opening portion  3 . For this reason, equipment capable of finely adjusting the dimension of insertion of the shoulder portion  26  is preferred. Also, the positional accuracy of the metalworking apparatus in the slide direction is desirably within ± 1/100 to 1/1000 mm. In this way, it is possible to adjust the pressing force of the shoulder portion  26  contacting the inner side surface  16  at the peripheral edge of the opening portion  3  and reduces the occurrence of the small protrusion  6 . 
       FIG.  7   , in contrast, shows a comparative example in which a metal plate not having work-hardened is worked by using a normal punching tool having a straight insertion portion without the shoulder portion  26 . In this comparative example, rollovers are formed at the peripheral edges of opening portions  3   a  to  3   c . The sizes of such rollovers (hereinafter also referred to as rollover amounts d 1 , d 2 , . . . ) are larger at a portion where the plural opening portions  3  are formed (e.g., d 1 &lt;d 2 ). Here, the rollover amount d 1  is approximately 0.1 mm, and the rollover amount d 2  is approximately 0.15 mm. 
     In particular, when the opening portions  3   a  to  3   c  are arranged in a straight line, the rollover amounts d 1 , d 2 , . . . formed at the peripheral edges of the opening portions  3   a  to  3   c  are such that the rollover amount is piled up toward the intermediate position. Thus, at a region around the middle opening portion  3   b , the material drag occurs by which the region sinks downward by a predetermined dimension H from the surrounding upper surface  2   c . Here, the predetermined dimension H is approximately 0.05 mm. 
     Next, advantageous effects of the metalworking apparatus and the metalworking method in the embodiment will be described. 
     In the present embodiment, as shown in  FIG.  1   , the to-be-opened portion  5  of the plate material  2  is work-hardened through forging with the forging tool  10 . 
     Specifically, in the forging step with the forging tool  10  of the present embodiment, firstly, the forging tool  10  is mounted on the slide movement member. The distal end  11   a  of the forging tool  10  is provided to protrude in a tapered conical shape on the central axis S at the center in the radial direction and is disposed immediately above a center portion of the to-be-opened portion  5 . 
     As the slide movement member is moved downward in the slide direction, the pressing portion  11  moves downward to approach the plate material  2  which is fixed horizontally. The distal end  11   a  is then brought into contact with the center of the to-be-opened portion  5  of the plate material  2 . 
     As the slide movement member is further moved downward in the slide direction, the pressing portion  11  of the forging tool  10  pushes away the metallic material radially outward from the radial center which the distal end  11   a  has contacted. The portion  2   b  thus pushed away is work-hardened (base-material-hardened) and the density of the to-be-opened portion  5  increases as compared to that of the other portion of the plate material  2 . 
     Here, since the pressing portion  11  of the present embodiment has the distal end  11   a  provided to protrude in a conical shape, the metallic material pressed evenly in all radially outward directions from the central axis S is pushed away. 
     In addition, the conical pressing portion  11  of the forging tool  10  of the present embodiment is provided to protrude in a tapered shape. Thus, when the metallic material in the to-be-opened portion  5  is evenly pushed away, the metallic material gets compressed downward from the pressing portion  11 . Also, since a large amount of the metallic material is evenly pushed away toward the radially outer surrounding region, the occurrence of cracking and the like is reduced. This makes it possible to obtain the to-be-opened portion  5  work-hardened with the radial dimension c 2 , which is larger than the outer radial dimension c 1  of the pressing portion  11 . 
     Note that, in the forging step, the clamping jig fixing the plate material  2  may have a concave portion recessed from the upper surface. It is more preferable that the concave portion be formed to be aligned with the central axis S. 
     In the forging step with the forging tool  10 , the flat portion  12  prevents the metallic material at the peripheral edge of the to-be-opened portion  5  from escaping upward in the out-of-plane direction. This enables greater compression, so that the efficiency of the work-hardening is excellent. 
     As shown in  FIG.  2   , the insertion portion  22  of the punching tool  20  is inserted into the work-hardened portion of the to-be-opened portion  5  to form the opening portion  3  by punching. The shoulder portion  26  of the punching tool  20  is brought into contact with the work-hardened portion remaining at the inner peripheral edge of the opening portion  3  from the inner side surface  16 . 
     At this time, the amount of insertion of the punching tool  20  is adjusted to stop the force applied from the shoulder portion  26  to the inner side surface  16  immediately before the small protrusion  6  protrudes upward beyond the upper surface  2   c . This makes the peripheral edge of the opening portion  3  flush with the upper surface  2   c  and hence improves the exterior quality. 
     Also, depending on the amount of insertion of the punching tool  20 , the small protrusion  6  that has appeared may protrude upward from the peripheral edge of the opening portion  3 . 
     In the present embodiment, the striking tool  30  is used to strike the small protrusion  6  protruding from the periphery from the opening portion  3  as shown in  FIG.  3   . This forms a flat surface flush with the upper surface  2   c  as shown in  FIG.  4   . 
     Hence, it is possible to reduce the rollover and the material drag even if the metalworking apparatus  1  does not have an excellent positional accuracy of the slide movement member in the slide direction. Accordingly, the plate-shaped product  4  with desired exterior quality is obtained without increasing a manufacturing cost. 
     Also, as shown in  FIG.  8   , the rate of increase in diameter of the curved surface  28  of the shoulder portion  26  (r/h) increases as the curved surface  28  extends from the insertion portion  22  on the distal end side toward the proximal end portion  24  on the proximal end side. 
     That is, the rate of increase in diameter is set smaller near the insertion portion  22  on the distal end side. Thus, even if the metalworking apparatus  1  does not have an excellent positional accuracy in the slide direction, the pressing force on the inner side surface  16  from the shoulder portion  26  does not change abruptly. It is therefore possible to use a metalworking apparatus with a slide movement member having a low positional accuracy in the slide direction, e.g., a metalworking apparatus with a positional accuracy of about 1/10 mm in the slide direction. This prevents an increase in manufacturing cost. 
     For example, with a curved surface  28  which has a rate of increase in diameter of r 1 /h 1  (or r 2 /h 2 ) lower than that of r 2 /h 2  (or r 3 /h 3 ), misalignment in the slide direction will cause only a small change in the amount of working of the opening portion  3 . 
     Also, the rate of increase in diameter of the shoulder portion  26  on the proximal end portion  24  side is set to be higher than that on the insertion portion  22  side. This reduces the amount of change in cross-sectional area in a direction perpendicular to the central axis at the portion where the shoulder portion  26  is joined to the proximal end portion  24  to avoid providing a portion of a bent origin. This improves the support rigidity of the insertion portion  22  of the punching tool  20 , and facilitates a work for a small opening portion  3 . 
     Also, as shown in  FIG.  3   , the striking tool  30  comes into contact with the flat striking surface  32  to strike and flatten the small protrusion  6  appearing around the opening portion  3 . 
     Thus, even if the positional accuracy of the slide movement member in the slide direction is not high, a region surrounding the opening portion  3  is made flush with the other region of the upper surface  2   c  of the plate material  2 , as shown in  FIG.  4   . 
     This reduces the rollover or the material drag and achieves a plate-shaped product  4  with a desired exterior quality. 
       FIGS.  9 A to  9 C  show modifications of the forging tool in the embodiment. Note that portions identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment are denoted by the same reference signs, and description thereof is omitted. 
       FIG.  9 A  shows a forging tool  40  of the modification. The forging tool  40  has a flat end surface  41  as a pressing surface. Moreover, the forging tool  40  work-hardens the plate material  2  through forging. 
     By the work-hardening, the to-be-opened portion  5  is pushed away radially outward from the radial center over a larger area than that of the embodiment to improve the density. 
     The other components and advantageous effects are identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment, and description thereof is therefore omitted. 
     In  FIG.  9 B , the plate material  2  is work-hardened through forging with a forging tool  50  which has a pressing surface  51  having a tapered conical distal end and does not have a flat portion around the pressing surface  51  (see the flat portion  12  in  FIG.  1   ). 
     With the forging tool  50  thus configured, the to-be-opened portion  5  is pushed away radially outward from the radial center to improve the density. 
     The other components and advantageous effects are identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment, and description thereof is therefore omitted. 
     In  FIG.  9 C , the plate material  2  is work-hardened through forging with a forging tool  60  which has a flat end surface  61  with an inclined surface  62  formed at its outer peripheral edge by chamfering. 
     With the forging tool  60  thus configured, particularly an outer peripheral edge portion of the to-be-opened portion  5  is pushed away radially outward from the radial center to improve the density. 
     The other components and advantageous effects are identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment, and description thereof is therefore omitted. 
     As described above, the metalworking method using the metalworking apparatus  1  of the present embodiment includes the forging step of work-hardening the to-be-opened portion  5  of the plate material  2  through forging (see  FIG.  1   ) and the punching step of forming the opening portion  3  in the forged to-be-opened portion  5  of the plate material  2  by punching (see  FIG.  2   ). 
     In this way, the to-be-opened portion  5  work-hardened in the forging step is punched in the punching step to form the opening portion  3 . 
     The metallic material at the peripheral edge of the opening portion  3  is pushed away radially outward from the radial center to improve the density. This reduces the rollover or the material drag at the peripheral edge of the opening portion  3 . 
     Also, in the striking step (see  FIG.  3   ), the striking tool  30  strikes and flattens the small protrusion  6  appearing around the punched opening portion  3 . Thus, even if the small protrusion  6  appears in the punching step due to a reason such as a low accuracy in the amount of movement of the punching tool  20  in the slide direction, the small protrusion  6  is struck in the striking step to be flush with the other region of the upper surface  2   c.    
     As described above, the metalworking apparatus and the metalworking method of the present embodiment reduces the rollover and the material drag and thus improves the exterior quality of the plate-shaped product  4 . 
     The present invention is not limited to the above-described embodiments, and various changes can be made. The above-described embodiments have been exemplarily presented in order to describe the present invention comprehensibly, and is not necessarily limited to an embodiment including all configurations described. Also, a part of a configuration of one embodiment can be replaced with a configuration of another embodiment, and a configuration of one embodiment can be added to a configuration of another embodiment as well. Also, a part of a configuration of each embodiment can be removed, or replaced with or added to another configuration. The above-described embodiments can be changed as below, for example. 
     The three modifications of the forging tool are presented as shown in  FIGS.  9 A to  9 C  in the present embodiments. Meanwhile, a forging tool, a punching tool, and a striking tool are not limited to those of the present embodiment. For example, their distal ends may be in semispherical shapes or the like. A forging tool, a punching tool, and a striking tool are not particularly limited in shape, number, and material as long as they work-harden the to-be-opened portion through forging. 
     LIST OF REFERENCE SIGNS 
     
         
           1  metalworking apparatus 
           3  opening portion 
           5  to-be-opened portion 
           10  forging tool 
           16  inner side surface 
           20  punching tool 
           22  insertion portion 
           24  proximal end portion 
           26  shoulder portion