JP6204444B2 - Method for manufacturing metal element for continuously variable transmission - Google Patents

Description

  The present invention relates to a method for manufacturing a metal element for a continuously variable transmission, in which a metal element for a continuously variable transmission is manufactured by pressing and punching a strip-shaped metal element material having a constant cross section using a die. About.

  In the manufacturing method of metal elements used for metal belts of belt-type continuously variable transmissions, the metal element material roughly formed into a shape close to the shape of the metal element product is pressed with a die consisting of a main punch and counter punch and finished. Patent Document 1 below discloses a technique for improving the accuracy of the shape in the vicinity of the rocking edge of the metal element while ensuring the durability of the mold by molding.

  In addition, the position of the rocking edge of the metal element used for the metal belt of the belt-type continuously variable transmission matches the front edge position of the saddle surface, which is the radially outer end position of the front surface of the body portion of the metal element. When the metal elements to be swung relative to each other with the rocking edge as a fulcrum, the positional relationship between the saddle surfaces of adjacent metal elements in the front-rear direction is kept constant, and the friction loss occurs between the saddle surface and the metal ring assembly. It is known from the following Patent Document 2 that prevents the occurrence of.

Japanese Patent No. 4132820 WO2014 / 196254A1

  By the way, as described in detail in the section of [Description of the Invention] in this specification, the device described in Patent Document 1 described above is used when a metal element is press-molded with a mold. Since the thickness of the body part located on the radially inner side is slightly smaller than the thickness of the ear part located on the radially outer side, a large number of metals are formed at the string part of the metal belt wound around the drive pulley and the driven pulley. When the elements are in close contact with each other to transmit the driving force, the chord portion of the metal belt may bend radially outward due to the plate thickness difference described above, which may reduce the transmission efficiency of the driving force.

  In addition, since the amount of the metal element material that is pushed away by the mold is large when the metal element is pressed from the metal element material with a mold, the one described in Patent Document 1 requires a large pressing load. Or the durability of the mold may be reduced.

  The present invention has been made in view of the above circumstances, and aims to reduce the press load of the body portion of the metal element to increase the durability of the mold and to make the plate thickness of each portion of the metal element uniform. To do.

  To achieve the above object, according to the first aspect of the present invention, a pair of ring slots into which a pair of metal rings are fitted, a neck portion positioned between the pair of ring slots, and the neck portion An ear part continuous to the radially outer side of the neck part, and a body part formed with a saddle surface supporting the inner peripheral surface of the metal ring connected to the radially inner side of the neck part. A strip-shaped metal element material having a constant cross section is formed of a metal element formed with a locking edge that overlaps the front edge of the saddle surface and extends in the left-right direction, and an inclined surface that extends radially inward and rearward from the locking edge. A method for manufacturing a metal element for a continuously variable transmission manufactured by pressing and punching using a die, corresponding to the inclined surface of the metal element. The inclined surface corresponding portion of the metal element material includes a first inclined surface corresponding portion inclined backward from the locking edge corresponding portion corresponding to the locking edge of the metal element at a first inclination angle, and the first inclined surface corresponding portion. And a second inclined surface corresponding portion inclined rearward at a second inclination angle larger than the first inclination angle from a radially inner end of the first, and the mold is a rocking edge forming portion that contacts the rocking edge corresponding portion A first inclined surface forming portion inclined backward at the first inclination angle, and the first inclined surface forming portion abuts against the first inclined surface corresponding portion of the metal element material during the press working. A method for manufacturing a metal element for a continuously variable transmission is proposed, in which a gap is formed between the two inclined surface corresponding parts.

  According to the invention described in claim 2, in addition to the structure of claim 1, a position corresponding to the ring slot and the neck portion of the metal element on the front surface of the metal element material faces backward. A method of manufacturing a metal element for a continuously variable transmission is proposed, in which a concave portion is formed.

  In addition, the neck part corresponding | compatible part 25 'of embodiment corresponds to the recessed part of this invention, and the counter punch 47 of embodiment corresponds to the metal mold | die of this invention.

  According to the configuration of the first aspect, the metal element material is pressed with the mold on the inclined surface extending radially inward and rearward from the locking edge formed so as to coincide with the front edge of the saddle surface of the body portion of the metal element. When processing and forming, the inclined surface corresponding portion of the metal element material corresponding to the inclined surface of the metal element includes a first inclined surface corresponding portion inclined backward from the rocking edge corresponding portion at a first inclination angle, and a first inclined surface corresponding portion. A rocking edge molding that includes a second inclined surface corresponding portion that is inclined backward from the radially inner end of the inclined surface corresponding portion with a second inclination angle that is larger than the first inclination angle, and the mold contacts the locking edge corresponding portion. Since the first inclined surface forming portion is inclined backward from the portion at the first inclination angle, the first inclined surface forming portion abuts on the first inclined surface corresponding portion of the metal element material at the time of press working and corresponds to the second inclined surface. With the department Gap is formed. As a result, the amount of the material of the metal element material that is crushed when the first inclined surface corresponding part is pressed can be minimized, the press load can be reduced, and the durability of the mold can be increased. By reducing the amount of material flowing from the first inclined surface corresponding portion to the inside in the radial direction of the metal element material, the plate thickness of the body portion in the vicinity of the rocking edge of the metal element is reduced with respect to the plate thickness of the ear portion. Can be prevented.

  According to the second aspect of the present invention, the concave portion that is recessed toward the rear is formed at the position corresponding to the ring slot and the neck portion of the metal element on the front surface of the metal element material. By machining sharply as the edge of the concave part of the metal element material in advance, it prevents the rocking edge from occurring due to the shear load when punching the concave part of the metal element material with a mold to manufacture the metal element. The processing accuracy of the rocking edge can be increased.

The figure which shows the whole structure of a belt-type continuously variable transmission. (Embodiment) The fragmentary perspective view of a metal belt. (Embodiment) The front view of a metal element. (Embodiment) FIG. 4 is a sectional view taken along line 4-4 of FIG. (Embodiment) The perspective view of a metal element material. (Embodiment) Sectional drawing of a punching device and a metal element material. (Embodiment) Action explanatory drawing corresponding to FIG. (Embodiment) Action explanatory drawing corresponding to FIG. (Embodiment) The figure which shows the state which wound the metal belt around the drive pulley and the driven pulley. (Embodiment) The graph which shows the change of the plate | board thickness difference according to a press load. (Embodiment) Sectional drawing of a punching device and a metal element material. (Conventional example) The graph which shows the change of the plate | board thickness difference according to a press load. (Conventional example)

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic structure of a belt-type continuously variable transmission T mounted on an automobile. The belt-type continuously variable transmission T has a drive shaft 11 connected to an engine and a driven shaft 12 connected to drive wheels. An endless metal belt 15 is wound around a drive pulley 13 provided on the drive shaft 11 and a driven pulley 14 provided on the driven shaft 12. The drive pulley 13 includes a fixed-side pulley half 16 fixed to the drive shaft 11 and a movable-side pulley half 17 that can be brought into and out of contact with the fixed-side pulley half 16. The half body 17 is biased toward the stationary pulley half body 16 by hydraulic pressure acting on the oil chamber 18. The driven pulley 14 includes a fixed-side pulley half 19 fixed to the driven shaft 12 and a movable-side pulley half 20 that can be brought into and out of contact with the fixed-side pulley half 19. The half body 20 is biased toward the fixed pulley half body 19 by hydraulic pressure acting on the oil chamber 21.

  As shown in FIGS. 2 to 4, the metal belt 15 is configured by supporting a number of metal elements 23 on a pair of left and right metal rings 22. In this specification, the direction in which the metal belt 15 travels is defined as the front in the front-rear direction, and the outer peripheral side of the drive pulley 13 and the driven pulley 14 is the diameter with the metal belt 15 wound around the drive pulley 13 and the driven pulley 14. The direction is defined as the outside of the direction, and the direction orthogonal to the front-rear direction and the radial direction is defined as the left-right direction. The metal element material 23 ′ (see FIG. 5), which is the material of the metal element 23, and the punching apparatus 41 (see FIG. 6) for forming and punching the metal element 23 from the metal element material 23 ′ are also used. The directions corresponding to the front-rear direction, radial direction, and left-right direction are defined as the front-rear direction, radial direction, and left-right direction.

  The metal element 23 manufactured from the metal element material 23 ′ has a body portion 24 extending in the left-right direction, a neck portion 25 extending radially outward from the center in the left-right direction of the body portion 24, and a radially outer end of the neck portion 25. A pair of ring slots 27 are formed between the body portion 24, the neck portion 25, and the ear portion 26 so as to open outward in the left-right direction and fit the metal ring 22. The A saddle surface 28 on which the inner peripheral surface of the metal ring 22 is seated is formed at the radially outer end of the body portion 24 facing the ring slot 27, and a rocking edge extending in the left-right direction at the radially outer end of the front surface of the body portion 24. 29 is formed, and an inclined surface 30 that is inclined radially inward and backward from the rocking edge 29 is formed on the front surface of the body portion 24. The locking edge 29 overlaps the front edge of the saddle surface 28, and therefore the locking edge 29 is located at the radially outer end of the front surface of the body portion 24.

  Pulley contact surfaces 31 that contact the V surfaces of the drive pulley 13 and the driven pulley 14 are formed on the left and right ends of the body portion 24 of the metal element 23. Further, on the front surface of the ear portion 26 of the metal element 23, a convex portion 32 that can be fitted into a concave portion 33 formed on the rear surface of the ear portion 26 is formed.

  The inclined surface 30 of the metal element 23 includes a first inclined surface 30a inclined radially inward and rearward from the rocking edge 29 at a first inclination angle θ1, and a second inclined angle from the radially inner end of the first inclined surface 30a. It comprises a second inclined surface 30b that is inclined inward and backward in the radial direction at θ2, and the front-rear direction plate thickness of the body portion 24 gradually decreases radially inward within the range of the inclined surface 30. The plate thickness in the front-rear direction of the body portion 24 becomes the maximum plate thickness t1 at the position of the rocking edge 29, and this maximum plate thickness t1 coincides with the plate thickness t2 in the front-rear direction of the ear portion 26 having a constant plate thickness of the metal element 23. Further, the front surface of the neck portion 25 is recessed rearward from the front surface of the ear portion 26 and the locking edge 29, and the front-rear direction plate thickness t3 is the maximum of the body portion 24 at the front-rear direction plate thickness t2 of the ear portion 26 and the locking edge 29. It is smaller than the plate thickness t1.

  Therefore, when the adjacent metal elements 23 are aligned in the chord portion of the metal belt 15, the front surface of the ear portion 26 of the rear metal element 23 comes into contact with the rear surface of the ear portion 26 of the front metal element 23, and the rear side. The locking edge 29 of the metal element 23 abuts on the upper end (the rear edge of the saddle surface 28) of the body portion 24 of the front metal element 23. Further, the rear metal element 23 can swing with respect to the rear surface of the front metal element 23 with a rocking edge 29 as a fulcrum, so that the metal belt 15 can be wound around the drive pulley 13 and the driven pulley 14. .

  As shown in FIG. 5, the metal element material 23 ′, which is a material for manufacturing the metal element 23, is composed of a strip-shaped metal plate that has been rolled so as to have a constant cross section in the longitudinal direction. The metal element material 23 ′ includes an ear portion corresponding portion 26 ′, a neck portion corresponding portion 25 ′, and a body portion corresponding 24 ′ corresponding to the ear portion 26, the neck portion 25, and the body portion 24 of the metal element 23, respectively.

  The ear portion corresponding portion 26 ′ has a constant plate thickness substantially the same as the plate thickness t 2 of the ear portion 26, and the neck portion corresponding portion 25 ′ has a constant plate thickness substantially the same as the plate thickness t 3 of the neck portion 25. doing. The body portion corresponding portion 24 'has substantially the same plate thickness as the maximum plate thickness t1 of the body portion 24 at the position of the rocking edge corresponding portion 29', and the plate thickness decreases radially inward therefrom. In other words, the inclined surface corresponding portion 30 'of the body portion corresponding portion 24' of the metal element material 23 'corresponds to the first inclined surface inclined inward and rearward in the radial direction at the first inclination angle θ1 from the rocking edge corresponding portion 29'. Part 30a ′ and a second inclined surface corresponding part 30b ′ inclined radially inward and rearward at a second inclination angle θ2 from the radial inner end of the first inclined surface corresponding part 30a ′.

  As described above, the cross-sectional shape of the metal element material 23 ′ substantially matches the cross-sectional shape of the metal element 23 except that the metal element material 23 ′ does not have portions corresponding to the convex portions 32 and the concave portions 33 of the metal element 23. Then, the locking edge corresponding portion 29 ′, which is the radially inner end of the neck corresponding portion 25 ′ constituting the groove-shaped recess, is processed into an edge shape having an acute angle.

  As shown in FIG. 6, the punching device 41 for punching the metal element 23 from the metal element material 23 ′ is capable of moving up and down on the lower die 43 fixed to the lower part of the frame body 42 and the upper part of the frame body 42. An upper die 45 that is supported and driven up and down by a die drive cylinder 44, a counter punch 47 that is fitted into a recess 43a that is open on the upper surface formed in the lower die 43 and is driven up and down by a counter punch drive cylinder 46, and an upper side And a main punch 49 which is engaged with a concave portion 45a formed on the lower surface of the die 45 and is driven up and down by a main punch driving cylinder 48.

  In FIG. 6, the counter punch 47 and the main punch 49 are depicted as being divided into two parts: a part for forming the ear part 26 of the metal element 23 and a part for forming the body part 24 of the metal element 23. Actually, each of the counter punch 47 and the main punch 49 is one member.

  The contour shapes of the counter punch 47 and the main punch 49 are the same as the contour shape of the metal element 23, and the convex shape forming portion 47 a for forming the convex portion 32 of the metal element 23 and the metal element 23 are formed on the counter punch 47. The rocking edge forming portion 47b for forming the rocking edge 29 and the first inclined surface forming portion 47c for forming the first inclined surface 30a of the metal element 23 are formed. A recessed portion forming portion 49a for forming the recessed portion 33 is formed.

  The first inclined surface forming portion 47c of the counter punch 47 is parallel to the first inclined surface corresponding portion 30a ′ of the inclined surface corresponding portion 30 ′ of the metal element material 23 ′, and the first inclined surface forming portion 47c and the first inclined surface forming portion 47c. Both of the surface corresponding portions 30a ′ are inclined by the first inclination angle θ1. Accordingly, the first inclined surface forming portion 47c has a gap α between the inclined surface corresponding portion 30 ′ of the metal element material 23 ′ and the second inclined surface corresponding portion 30b ′.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  As shown in FIG. 6, the metal element material 23 ′ manufactured in advance is placed on the lower die 43 and the counter punch 47 of the punching device 41. Subsequently, as shown in FIG. 7, the upper die 45 is lowered by the die drive cylinder 44, and the metal element material 23 ′ is sandwiched and fixed between the lower die 43 and the upper die 45, and then the main punch drive cylinder 48. The main punch 49 is lowered, and the metal element material 23 ′ is sandwiched between the counter punch 47 and the main punch 49 and is pressed. As a result, the convex portion 32 and the concave portion 33 of the metal element 23 are formed by the convex portion forming portion 47a of the counter punch 47 and the concave portion forming portion 49a of the main punch 49, and at the first inclined surface forming portion 47c of the counter punch 47. The first inclined surface corresponding portion 30a 'of the metal element material 23'b (that is, the first inclined surface 30a of the metal element 23) is formed.

  When the press forming of the metal element 23 is completed in this way, the counter punch 47 and the main punch 49 are moved to the counter punch driving cylinder 46 and the main punch driving with respect to the lower die 43 and the upper die 45 as shown in FIG. The metal element 23 is punched from the metal element material 23 ′ by being relatively lowered by the cylinder 48.

  Incidentally, as shown in FIG. 9, the metal belt 15 wound around the drive pulley 13 and the driven pulley 14 rotating in the direction indicated by the arrow is a drive-side string extending linearly between the drive pulley 13 and the driven pulley 14. 15a and a return-side string portion 15b, the adjacent metal elements 23 are in contact with each other in the drive-side string portion 15a, and the driving force is transmitted from the drive pulley 13 to the driven pulley 14 by the pushing force. .

  The front and rear metal elements 23 adjacent to each other on the drive-side chord portion 15a include an ear portion 26 having a front-rear direction plate thickness t2 and a rocking edge 29 of a body portion 24 having a front-rear direction plate thickness t1 equal to the front-rear direction plate thickness t2. However, in the conventional metal element 23, the plate thickness t1 of the rocking edge 29 is slightly smaller than the plate thickness t2 of the ear portion 26. There is a problem that the transmission efficiency of the driving force is lowered because the string portion 15a is curved radially outward.

  Hereinafter, the reason why the plate thickness of the body portion 24 is thinner than the plate thickness of the ear portion 26 in the conventional metal element 23 will be described.

  FIG. 11 shows a conventional example described in Patent Document 1 above. A punch for pressing the metal element material 23 ′ to finish the metal element 23 is a counter punch 51 for forming the front surface of the metal element 23. And a main punch 52 for forming the rear surface of the metal element 23. The forming part 52 a of the main punch 52 is basically a flat surface, but the forming part of the counter punch 51 is more flat than the flat first forming part 51 a that forms a radially outer part than the locking edge 29 and the locking edge 29. And a flat second molding portion 51b for molding the radially inner inclined surface 30, and a rocking edge molding portion 51c extending in the left-right direction is formed at the boundary between the first molding portion 51a and the second molding portion 51b. .

  The metal element material 23 ′ includes a locking edge corresponding portion 29 ′ corresponding to the locking edge 29 of the metal element 23 and an inclined surface corresponding portion 30 ′ corresponding to the inclined surface 30 of the metal element 23. The locking edge corresponding portion 29 ′ of the metal element material 23 ′ is displaced inward in the radial direction by an offset OS with respect to the locking edge forming portion 51 c of the counter punch 51.

  The forming part 52a of the main punch 52 and the first forming part 51a of the counter punch 51 are parallel to the radial direction, but the second forming part 51b of the counter punch 51 is inclined at an inclination angle θ3 with respect to the radial direction. doing. The inclined surface corresponding portion 30 ′ of the metal element material 23 ′ is also inclined at the inclination angle θ 4 with respect to the radial direction, but the inclined angle θ 4 of the inclined surface corresponding portion 30 ′ is that of the second forming portion 51 b of the counter punch 51. It is set larger than the inclination angle θ3.

  When the metal element material 23 ′ is pressed by the counter punch 51 and the main punch 52, the material of the inclined surface corresponding portion 30 ′ of the metal element material 23 ′ (see the shaded portion in the enlarged portion in FIG. 11) by the action of the offset OS. Although it tries to prevent the plate | board thickness of the body part 24 radially outer than the rocking edge 29 from flowing radially outward, the inner diameter direction end of the inclined surface 30 after molding and the second molded part 51b Since the gap β remains between them, the material of the inclined surface corresponding portion 30 ′ of the metal element material 23 ′ flows inward in the radial direction due to the gap β, and the body portion 24 radially outside the rocking edge 29. There is a tendency that the plate thickness becomes thinner than the plate thickness of the ear portion 26.

  FIG. 12 shows the plate thickness (body portion plate thickness) at the center portion in the left-right direction of the body portion 24 radially outside the locking edge 29 and the plate thicknesses at the left and right end portions of the ear portion 26 (ears). Part thickness) and how the difference between the average thicknesses of the left and right ear parts relative to the body part thickness changes according to the press load. As is apparent from the figure, the difference in plate thickness of the average value of the left and right ear portion thicknesses with respect to the body portion plate thickness becomes large regardless of the size of the press load.

  In contrast to the above-described conventional example, in the embodiment shown in FIG. 6, the first inclined surface forming portion 47c of the counter punch 47 abuts in parallel with the first inclined surface corresponding portion 30a 'of the metal element material 23' and is pressed. Since it does not abut against the second inclined surface corresponding portion 30b 'of the metal element material 23', the amount of the material that is pushed and pushed out by the first inclined surface corresponding portion 30a 'is (in the enlarged portion of FIG. 6) 11) is significantly smaller than the conventional example of FIG. 11, and the press load of the counter punch 47 and the main punch 49 can be reduced by that much, and the durability of the counter punch 47 and the main punch 49 can be reduced. Will improve. Moreover, since the amount of material flowing at the time of press molding is small, the problem that the plate thickness in the vicinity of the locking edge 29 of the body portion 24 decreases with respect to the plate thickness of the ear portion 26 of the metal element 23 is also eliminated. The decrease in efficiency is also eliminated.

  FIG. 10 shows how the plate thickness difference between the body portion plate thickness, the ear portion left and right plate thickness, and the average value of the ear portion left and right plate thickness with respect to the body portion plate thickness varies depending on the press load in the present embodiment. It shows what to do. As can be seen from the figure, according to the present embodiment, the plate thickness difference of the metal element 23 can be significantly reduced compared to the conventional example described in FIG. 12 regardless of the press load.

  Further, when the metal element 23 is manufactured from the metal element material 23 ′ by the punching device 41, the locking edge 29 of the metal element 23 is formed by punching a portion corresponding to the ring slot 27 by shearing. In general, when a metal member is cut by shearing, a part of the metal member's meat is plastically deformed and stretched at the boundary between the die and the punch, so that the edge of the shearing surface may be rounded (rounded). is there. However, if the rocking edge 29 of the metal element 23 falls, the plate thickness of the body portion 24 of the metal element 23 decreases in the vicinity of the rocking edge 29, and there is a difference in plate thickness from the plate thickness of the ear portion 26. For this reason, the locking edge 29 needs to be formed into a sharp shape without anybody.

  According to the present embodiment, the locking edge 29 of the metal element 23 is cut into a sharp shape in advance as the locking edge corresponding portion 29 ′ of the metal element material 23 ′. When the 23 'neck portion corresponding portion 25' is punched out by shearing at the rocking edge forming portion 47b of the counter punch 47, only the neck portion corresponding portion 25 'constituting the groove-shaped recess is punched, thereby cutting sharpened. The locking edge 29 can be left as it is.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the neck portion corresponding portion 25 ′ of the metal element material 23 ′ of the embodiment constitutes a groove-like recess, but this groove-like recess is not always necessary.

22 Metal ring 23 Metal element 23 'Metal element material 24 Body part 25 Neck part 25' Neck part corresponding part (concave part)
26 Ear portion 27 Ring slot 28 Saddle surface 29 Rocking edge 29 'Rocking edge corresponding portion 30 Inclined surface 30' Inclined surface corresponding portion 30a 'First inclined surface corresponding portion 30b' Second inclined surface corresponding portion 47 Counter punch (die)
47b Rocking edge forming part 47c First inclined surface forming part α Gap θ1 First inclination angle θ2 Second inclination angle

Claims (2)

A pair of ring slots (27) into which a pair of metal rings (22) are fitted, a neck portion (25) positioned between the pair of ring slots (27), and radially outward of the neck portion (25) A continuous ear part (26) and a body part (24) in which a saddle surface (28) supporting the inner peripheral surface of the metal ring (22) is formed continuously to the radially inner side of the neck part (25). A locking edge (29) extending in the left-right direction on the front surface of the body portion (24), overlapping the front edge of the saddle surface (28), and an inclination extending radially inward and rearward from the locking edge (29) The metal element (23) formed with the surface (30) is manufactured by pressing and punching a strip-shaped metal element material (23 ') having a constant cross section using a die (47). A manufacturing method of a metal element for a continuously variable transmission,
An inclined surface corresponding portion (30 ′) of the metal element material (23 ′) corresponding to the inclined surface (30) of the metal element (23) corresponds to the locking edge (29) of the metal element (23). A first inclined surface corresponding portion (30a ') inclined backward at a first inclination angle (θ1) from a rocking edge corresponding portion (29'), and a radially inner end of the first inclined surface corresponding portion (30a ') And a second inclined surface corresponding portion (30b ') inclined backward at a second inclination angle (θ2) larger than the first inclination angle (θ1), and the mold (47) corresponds to the rocking edge A first inclined surface forming portion (47c) inclined rearward at the first inclination angle (θ1) from a rocking edge forming portion (47b) contacting the portion (29 ′), and the first inclined surface during the press working Molding part (47c) is the gold A gap (α) is formed between the element material (23 ′) and the second inclined surface corresponding portion (30b ′) in contact with the first inclined surface corresponding portion (30a ′). A method for manufacturing a metal element for a continuously variable transmission. A concave portion (25 ') recessed toward the rear is formed at a position corresponding to the ring slot (27) and the neck portion (25) of the metal element (23) on the front surface of the metal element material (23'). The method of manufacturing a metal element for a continuously variable transmission according to claim 1, wherein the metal element is formed.

Images