Patent Publication Number: US-2012042707-A1

Title: Wire drawing device and method for manufacturing wire

Description:
TECHNICAL FIELD 
     The present invention relates to the technology of drawing a wire. 
     BACKGROUND ART 
     The conventional technologies of drawing wires are disclosed in Patent Document 1 and Patent Document 2. 
     In Patent Document 1, a plurality of intermediate drawing capstans are divided into two or more blocks such that some of them are accommodated in one block, and the plurality of intermediate drawing capstans are driven by one motor per block. 
     In Patent Document 2, a plurality of wire drawing units including a drive capstan and a capstan drive motor are disposed between unwinding means and winding means. 
     In the wire drawing machines as described above, the degree of diameter reducing deformation is set correspondingly to the intervals between the capstans, which are configured such that a wire is gradually subjected to diameter reducing deformation through a plurality of diameter reducing deformation processes. Specifically, dies are disposed between the capstans correspondingly to the degree of diameter reducing deformation. Further, the drawing speed ratio of capstans disposed so as to sandwich each die is set correspondingly to the degree of diameter reducing deformation by the die. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent Application Laid-Open No. 11-47821 (1999) 
     Patent Document 2: Japanese Patent Application Laid-Open No. 2005-103623 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     In the case of drawing a wire, it is necessary to appropriately set or change the degree of diameter reducing deformation of a wire in accordance with a material of a base wire to be processed, a target finished wire diameter or the like. 
     In the technology disclosed in Patent Document 1, however, a plurality of intermediate drawing capstans are rotatively driven by one drive motor per block, which makes it difficult to change the setting of the degree of diameter reducing deformation of a wire. 
     Meanwhile, in the technology disclosed in Patent Document 2, all capstans are rotatively driven by a motor in an individual manner, which complicates maintenance tasks. 
     Therefore, an object of the present invention enables easy response to, for example, adjustment or change of the degree of diameter reducing deformation of a wire in accordance with a material of a base wire, a target finished wire diameter or the like while simplifying maintenance tasks. 
     Means to Solve the Problems 
     In order to solve the above-mentioned problems, a first aspect relates to a wire drawing machine drawing a wire, which includes: a wire supply part supplying a wire; a wire pulling part pulling the wire; a first capstan mechanism part provided between the wire supply part and the wire pulling part on a side closer to the wire supply part, which includes a plurality of first capstans, a first rotation drive source, and a first rotation transmission mechanism part transmitting a rotation drive force of the first rotation drive source to the plurality of first capstans; a second capstan mechanism part provided between the wire supply part and the wire pulling part on a side closer to the wire pulling part than the first capstan mechanism part, which includes a plurality of second capstans, and a plurality of second rotation drive sources rotatively driving the plurality of second capstans in an individual manner; and a plurality of dies disposed between ones of the plurality of first capstans and the plurality of second capstans. 
     According to a second aspect, in the wire drawing machine according to the first aspect, drawing speed ratios between adjacent ones of the plurality of second capstans are set so that a wire that has passed through all of the plurality of second capstans has a smallest finished wire diameter among a plurality of types of finished wire diameters to be manufactured and that a wire that has passed through part of the plurality of second capstans has one finished wire diameter among the plurality of types of finished wire diameters to be manufactured. 
     According to a third aspect, in the wire drawing machine according to the first or second aspect, drawing speed ratios between adjacent ones of the plurality of second capstans are set so as to gradually decrease toward the wire pulling part. 
     According to a fourth aspect, in the wire drawing machine according to any one of the first to third aspects, a wire subjected to a wire drawing process is an aluminum wire or an aluminum alloy wire, and drawing speed ratios between ones of the plurality of first capstans are set so that the wire whose diameter has been reduced to 0.5 mm or smaller is subjected to the wire drawing process while the wire is drawn by the second capstan. 
     According to a fifth aspect, the wire drawing machine according to any one of the first to fourth aspects further includes a finishing capstan mechanism part provided between the wire supply part and the wire pulling part on a side closer to the wire pulling part than the second capstan mechanism part, which includes at least one finishing capstan, a finishing rotation drive source, and a finishing transmission mechanism part transmitting a rotation drive force of the finishing rotation drive source to the finishing capstan. 
     A sixth aspect relates to a strand manufacturing method of manufacturing a strand by drawing a wire with a wire drawing machine including: a wire supply part supplying a wire; a wire pulling part pulling the wire; a first capstan mechanism part provided between the wire supply part and the wire pulling part on a side closer to the wire supply part, which includes a plurality of first capstans, a first rotation drive source, and a first rotation transmission mechanism part transmitting a rotation drive force of the first rotation drive source to the plurality of first capstans; a second capstan mechanism part provided between the wire supply part and the wire pulling part on a side closer to the wire pulling part, which includes a plurality of second capstans, and a plurality of second rotation drive sources rotatively driving the plurality of second capstans in an individual manner; and a plurality of dies disposed between ones of the plurality of first capstans and the plurality of second capstans, the method including: setting rotational speeds of the plurality of second capstans so that a wire that has passed through all of the plurality of second capstans has a smallest finished wire diameter among a plurality of types of finished wire diameters to be manufactured and that a wire that has passed through part of the plurality of second capstans has one finished wire diameter among the plurality of types of finished wire diameters to be manufactured; and changing targets of the plurality of second capstans through which the wire passes to all or part thereof, to thereby manufacture strands having the plurality of types of finished wire diameters. 
     Effects of the Invention 
     According to the wire drawing machine of the first aspect, in the first capstan mechanism, the rotation drive force of one first rotation drive source is transmitted to a plurality of first capstans via the first rotation transmission mechanism part, which simplifies maintenance tasks. In the second capstan mechanism, the rotational speeds of a plurality of second rotation drive sources are individually adjusted so as to change the rotational speeds of the plurality of second capstans, which changes the drawing speed ratios between adjacent ones of the respective second capstans. This enables an easy response to adjustment or change of the degree of diameter reducing deformation of a wire in accordance with the material of a base wire, a target finished wire diameter or the like. 
     According to the second aspect, strands having a small diameter can be manufactured by performing the wire drawing process with all of the plurality of second capstans. Further, wire drawing performed by part of a plurality of second capstans enables to manufacture a strand having one of a plurality of types of finished wire diameters to be manufactured. Accordingly, once the drawing speed ratios between adjacent ones of the second capstans are set, the strands having a plurality of types of finished wire diameters can be easily manufactured without changing the setting. 
     According to the third aspect, the drawing speed ratios between adjacent ones become smaller as the diameter of the wire becomes smaller, which prevents cutting of the wire more reliably. 
     Generally, an aluminum wire or aluminum alloy wire is difficult to cut when having a diameter larger than 0.50 mm and is easy to cut when having a diameter smaller than 0.50 mm in the wire drawing process. Therefore, as in the fourth aspect, the wire drawing process is performed by the first capstan mechanism part to an extent that the diameter is reduced to approximately  0 .50 mm, which enables efficient wire drawing at a fixed delivery speed ratio. Meanwhile, a wire whose diameter has been reduced to 0.50 mm or smaller is subjected to the wire drawing process by drawing of the second capstans, which enables the wire drawing process in which the drawing speeds are adjusted so as to make it difficult to cut an aluminum wire or aluminum alloy wire. 
     According to the fifth aspect, the wire drawing process is performed at a relatively large degree of diameter reducing deformation by the first capstan mechanism part, and the wire drawing process is performed at a degree of diameter reducing deformation that is adjusted in accordance with a material or the like by the second capstan mechanism part, which enables the wire drawing process at a degree of diameter reducing deformation suitable for finishing by a plurality of finishing capstans. 
     According to the sixth aspect, the strands having a plurality of types of finished wire diameters can be easily manufactured without changing the rotational speeds of the second capstans. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic plan view showing a wire drawing machine according to an embodiment. 
         FIG. 2  is a schematic side view showing the wire drawing machine. 
         FIG. 3  is a figure showing examples of setting of percentage of area reduction. 
         FIG. 4  is a figure showing spots at which a wire is broken and factors of breaking. 
         FIG. 5  is an explanatory view showing an example of performing a wire drawing process with the use of part of second capstans. 
         FIG. 6  is a schematic plan view showing a wire drawing machine according to a modification. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Hereinafter, a wire drawing machine and a strand manufacturing method according to an embodiment are described.  FIG. 1  is a schematic plan view showing a wire drawing machine  20  according to the embodiment, and  FIG. 2  is a schematic side view showing the wire drawing machine  20 . 
     The wire drawing machine  20  is an apparatus that draws a wire so as to reduce diameters of wires  10 , and includes a wire supply part  22 , a wire pulling part  26 , a first capstan mechanism part  30 , a second capstan mechanism part  40  and a plurality of dies  60 . Note that the wires  10  generally refer to all wires including those before, after and during a wire drawing process, and in some cases, discrimination is made such that ones before the process are base wires  10   a  and drawn ones after the process are strands  10   b.  The strands  10   b  are used as, for example, cores of electric wires in a single manner or in a twisted manner. 
     The wire supply part  22  is configured so as to supply the base wires  10   a.  More specifically, the wire supply part  22  is configured to accommodate the base wires  10   a  that are wound around a reel-like member. The wire supply part  22  is rotatively supported on the upstream side of a predetermined wire drawing process line L such that the base wires  10   a  can be drawn from this wire supply part  22 . 
     The wire pulling part  26  is configured so as to pull the strands  10   b.  More specifically, in the wire pulling part  26 , a reel-like member capable of accommodating the strands  10   b  in a wound manner is supported to be rotatively driven by a rotation drive source such as a motor. The wire pulling part  26  is disposed on the downstream side of the wire drawing process line L such that the strands  10   b  processed to have a finished wire diameter are pulled by and accommodated in this wire pulling part  26 . 
     In the present embodiment, a plurality of (in this case, seven) wire supply parts  22  and a plurality of (in this case, seven) wire pulling parts  26  are provided so that a plurality of (in this case, seven) base wires  10   a  can be subjected to the wire drawing process. Needless to say, a twisting mechanism part that twists a plurality of strands  10   b  may be provided on the downstream side of the second capstan mechanism part  40 . In this case, only one wire pulling part that pulls only one twisted wire may be provided. 
     The first capstan mechanism part  30  is provided between the wire supply part  22  and the wire puling part  26  on the side closer to the wire supply part  22 , and includes a plurality of (in this case, eight) first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ), one first rotation drive source  34  and a first rotation transmission mechanism part  36 . 
     Each of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) is formed approximately in a disc shape or cylindrical shape, and a circumferential groove around which the wire  10  can be wound is formed on an outer circumference thereof. The circumferential grooves are formed in accordance with the number of wires  10  to be processed, and in this case, seven circumferential grooves are formed. The respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) are disposed so as to be lined at intervals along the wire drawing process line L from the upstream side toward the downstream side and supported so as to rotate about the rotation axis approximately in a horizontal direction almost perpendicular to the wire drawing process line L. The respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) are rotatively driven in the state in which the wires  10  are wound around the circumferential grooves of the respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ), so that the wires  10  are drawn at the drawing speed corresponding to the rotational speed. 
     Note that the rotation axis of each of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) may be an axis along an approximately perpendicular direction or a direction oblique to the approximately perpendicular direction. 
     The first rotation drive source  34  is a motor such as an AC motor and is configured so as to generate a rotation drive force. 
     The first rotation transmission mechanism part  36  is configured so as to transmit the rotation drive force of the one first rotation drive source  34  to the respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ). More specifically, the first rotation transmission mechanism part  36  includes drive shafts  36   a  that are respectively connected to the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) and speed change mechanisms  36   b  that change and transmit the speed of a rotation movement between the drive shafts  36   a  and so on. The speed change mechanism  36   b  is composed of various mechanisms such as a plurality of gears, a pulley and a transmission belt wound around the pulley, and is configured to transmit the rotation movement at a predetermined speed change ratio by appropriating setting a gear diameter, the number of teeth of the gear, a pulley diameter or the like. In this case, the rotation movement of the first rotation drive source  34  is transmitted to the first capstan  32 ( 8 ) on the downstream side at the rotational speed without change, and is transmitted from the downstream side to the first capstans  32 ( 7 ),  32 ( 6 ), . . . ,  32 ( 2 ) and  32 ( 1 ) on the upstream side at a gradually increasing speed. Accordingly, the rotational speeds of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) have values determined in accordance with the rotational speed of the first rotation drive source  34 , and the rotational speed ratio of the respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) is constant between ones of the upstream side and downstream side of the wire drawing process line L (in some case, simply referred to as between adjacent ones). In the present embodiment, description is given assuming that the respective capstans have the same diameter, and thus the constant rotational speed ratio between before adjacent ones means the constant drawing speed ratio between adjacent ones. In this case, in the respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ), the drawing speed ratios between adjacent ones thereof are set to be a given fixed value. A more specific setting example of the drawing speed ratio is described below. 
     The second capstan mechanism part  40  includes a plurality of (in this case, seven) second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) and a plurality of second rotation drive sources  44 , and is provided between the wire supply part  22  and the wire puling part  26  on the side closer to the wire pulling part  26  than the first capstan mechanism part  30 . The second capstan  42 ( 15 ) on the most downstream side of the wire supply line among the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) is referred to as a finishing capstan in some cases. 
     Similarly to the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ), each of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) is formed approximately in a disc shape or cylindrical shape, and a circumferential groove around which the wire  10  can be wound is formed on an outer circumference thereof. The respective second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are rotatively disposed and supported so as to be lined at intervals along the wire drawing process line L from the upstream side toward the downstream side in this order. The second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are rotatively driven in the state in which the wires  10  are wound around the circumferential grooves of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ), so that the wires  10  are drawn at the drawing speed corresponding to the rotational speed. 
     The second rotation drive source  44  is a motor capable of adjusting a rotational speed, such as an AC motor, and a plurality of (in this case, six) second rotation drive sources  44  are provided correspondingly to the respective second capstans  42 ( 9 ),  42  ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). The respective second rotation drive sources  44  are individually connected to the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ), and the respective second rotation drive sources  44  are configured so as to rotatively drive the second capstans in an individual manner. Accordingly, the rotational speeds of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) have values determined in accordance with the rotational speeds of the respective second rotation drive sources  44 , and the rotational speed ratios between adjacent ones of the respective second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) can be adjusted by the adjustment of the rotational speeds of the respective second rotation drive sources  44 . In the present embodiment, description is given assuming that the respective capstans have the same diameter, and thus the fact that the rotational speed ration between adjacent ones can be adjusted means that the drawing speed ratio between adjacent ones can be adjusted. In this case, the drawing speed ratios between adjacent ones of the respective second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are set so as to gradually decrease from the upstream side toward the downstream side of the wire drawing process line L (that is, are set such that the speed difference gradually decreases). A specific adjustment setting example of each drawing speed ratio is described below. 
     The configuration is made so as to include the first capstan mechanism part  30  and the second capstan mechanism part  40  as described above, with the result that the process region in which the drawing speed ratio is constant can be provided between adjacent ones of only the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) and that the process region in which the drawing speed ratio is variable can be provided between adjacent ones (that is, including the relation between the first capstan  32 ( 8 ) and the second capstan  42 ( 9 )) of the capstans including the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). 
     Provided between the second capstan mechanism part  40  and the wire pulling part  26  is a wire speed difference absorbing mechanism part  70  including a pair of rollers  72   a  and  72   b.  The wire speed difference absorbing mechanism part  70  is also referred to as, for example, a so-called dancer roller, and is configured such that the movable side roller  72   b  is supported so as to move close to and apart from the fixed roller  72   a.  The distance between both rollers  72   a  and  72   b  is adjusted in accordance with the wire speed difference between the second capstan  42 ( 15 ) and the wire pulling part  26 , whereby, for example, the slackness of the wire  10  between the second capstan mechanism part  40  and the wire pulling part  26  and the action by the excessive pulling force of the wire  10  are suppressed. 
     A plurality of dies  60  are processing tools for processing the wire  10  to have reduced diameter and deformed, and are detachably disposed between ones of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) and the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). More specifically, the dies  60  are members formed of metal or the like, in which a reduced diameter processing hole for allowing the wire  10  to pass therethrough is formed. In this case, a plurality of (in this case, seven) reduced diameter processing holes are formed in a parallel manner in accordance with the number of the wires  10  to be processed. The reduced diameter processing holes are formed into a through-hole shape whose diameter subsequently decreases from the upstream side toward the downstream side along the process line L. The aperture diameter on the upstream side of the reduced diameter processing hole is approximately identical to the diameter of the wire  10  guided by the die  60 , and the aperture diameter on the downstream side of the diameter reduced processing hole is approximately identical to a target diameter of one to be processed by the die  60 . In a case where the aperture area on the upstream side and the aperture area on the downstream side of the reduced diameter processing hole in the die  60  are represented by S 1  and S 2 , respectively, a percentage of reduction of the aperture area ((S 1 -S 2 )/S 1 ) is referred to as a percentage of area reduction. The percentage of area reduction is set in accordance with a target degree of diameter reducing process in the die  60 . A guide hole for guiding the wire  10  to the reduced diameter processing hole may be formed on the upstream side of the reduced diameter processing hole. Note that the respective dies  60  are detachably disposed for detachment, change, maintenance or the like of the dies  60 . In particular, in a case where the drawing speed ratio between adjacent ones is adjusted along with a change of the speeds of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ), it is necessary to replace the dies  60  with ones having a corresponding percentage of area reduction. 
     The relationship between the percentage of area reduction and the drawing speed ratio is now described. That is, when the wire  10  is processed to have a reduced diameter by the die  60 , the wire  10  is elongated to be long. Therefore, the speed of drawing the wire  10  needs to be made larger on the downstream side of the die  60  compared with the upstream side thereof. Further, the wire  10  is elongated more as the degree of diameter reducing process (percentage of area reduction) of the wire  10  by the die  60  becomes larger, and accordingly the ratio of the drawing speed on the downstream side to the drawing speed on the upstream side in the die  60  needs to be large. From the relationship of the cross-sectional area of the wire  10 , for example, in a case where the percentage of area reduction by the die  60  is “r”, it suffices that the ratio of the drawing speed difference to the drawing speed on the downstream side with the die  60  being sandwiched between the upstream side and the downstream side (that is, (V 2 -V 1 )/V 2 ) in the case where the drawing speed on the upstream side is V 1  and the drawing speed on the downstream side is V 2 ) is set to “r”. That is, when a study is made so as to perform processing in each capstan portion at a predetermined degree of diameter reducing deformation, the percentage of area reduction in the die  60  is determined as one type in terms of design. Correspondingly to this, the drawing speed ratio between adjacent capstans is determined as one type as well. That is, the setting and adjustment of the degree of diameter reducing deformation by each die  60  are synonymous with the setting and adjustment of the percentage of area reduction by a die and the setting and adjustment of the drawing speed ratio between adjacent capstans. The following description is given on that assumption. 
     Further, the wire drawing machine  20  includes a control unit  68 . The control unit  68  is a typical microcomputer including a CPU, ROM, RAM and the like. The control unit  68  receives, via an input part  68   a  such as a switch, on/off commands for the first rotation drive source  34  and each second rotation drive source  44  and a rotational speed command for each second rotation drive source  44 . Moreover, the control unit  68  controls on/off operation of the first rotation drive source  34  and each second rotation drive source  44  in accordance with the command and controls the rotational speed of each second rotation drive source  44 . Alternatively, the rotational speed of each second rotation drive source  44  may be adjusted by individual setting for each second rotation drive source  44 . 
     Hereinafter, the operation of the wire drawing machine  20  is described with reference to specific percentages of area reduction (%) of aluminum wire or aluminum alloy wire.  FIG. 3  is a figure showing examples of setting of the percentage of area reduction. Here, examples in which the base wire  10   a  that is made of an aluminum alloy and has a diameter of 1.100 mm is used as a base wire are assumed. In  FIG. 3 , the left column shows the numbers of brackets of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) and the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) (that is, order of capstans disposed from the upstream side toward the downstream side in the wire drawing process line L), the center column shows the diameter of the wire  10  wound around and drawn by each capstan, and the right column shows the percentages of area reduction by the die  60  located on the upstream side of each capstan. As described above, the percentage of area reduction represents the degree of diameter reducing deformation by the die  60  and also indirectly represents the drawing speed ratio between the adjacent capstans with the die  60  being sandwiched therebetween. 
     As shown in this figure, the percentage of area reduction is set to a given fixed value, 20% between ones of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) in the first capstan mechanism part  30 . That is, one configured to have a speed change ratio of that percentage of area reduction (drawing speed ratio) is used as the first rotation transmission mechanism part  36 . Note that the above-mentioned percentage of area reduction is a setting value that is obtained by considering that the wire drawing process for the wire  10  whose diameter has been reduced to 0.5 mm or smaller can be performed while drawing the wire  10  by the second capstan  42  ( 9 ). Accordingly, the base wire  10   a  having a diameter of 1.10 mm is deformed to have a reduced diameter in stages, from 0.98 mm to 0.87 mm, 0.78 mm, 0.70 mm, 0.62 mm, 0.56 mm and 0.50 mm. Then, the wire  10  whose diameter has been reduced to 0.50 mm is processed so as to be drawn by the die  60  between the capstan  32 ( 8 ) and the capstan  42 ( 9 ) while being drawn by the following second capstan  42 ( 9 ). 
     Description is now given of the reason why the wire drawing process is allowed for the wire  10  reduced to be 0.5 mm or smaller while drawing the wire  10  by the second capstan  42 ( 9 ). 
       FIG. 4  is a figure showing the spots in which a wire is broken in a case where the inventors have tried wire drawing process under various conditions, with various aluminum alloy wires as the base wires. The target wires herein include so-called 1000 series aluminum alloys (in particular, such as 1050 to 1080), 5000 series aluminum alloys (in particular, such as 5154 to 5454), and other aluminum alloys such as Al—Fe alloy, Al—Fe—Mg alloy and Al—Mg alloy in the JIS. As shown in this figure, wire breaking has occurred almost in the die portions processed in which a diameter is reduced to 0.5 mm or smaller. It is conceivable that an increased percentage of area reduction increases a possibility that wire breaking may be caused by factors such as an increase of drawing resistance and frictional heat due to improvements in speed. Therefore, the wire drawing process in the stage in which the wire  10  has a relatively large diameter is performed at the percentage of area reduction of a given fixed value by the respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) in the first capstan mechanism part  30 . On the other hand, the wire drawing process at the time when the wire  10  has a relatively small diameter (0.50 mm or smaller) is performed in the drawing process by the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) capable of, for example, changing setting of the percentage of area reduction. As a result, the wire  10  can be manufactured by adjusting the percentage of area reduction so as to make it difficult to cause wire breaking. 
     Between adjacent ones of the respective second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ), the percentages of area reduction are set to be smaller than the percentages of area reduction between ones of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) in the first capstan mechanism part  30  and are also set to gradually decrease toward the wire pulling part  26 . That is, setting is made such that the drawing speed ratios corresponding thereto gradually decrease toward the wire pulling part  26 . To what extent the percentage of area reduction is set or at what rate the percentage of area reduction is gradually decreased is experimentally determined in accordance with the material of the wire  10 , a target diameter thereof or the like. That is, it is preferable to set the percentage of area reduction as large as possible for processing with a minimum number of dies  60 . On the contrary, wire breaking is apt to occur when the percentage of area reduction is large. Whether wire breaking is apt to occur depends on the material of a wire, a process diameter thereof or the like, and thus the percentage of area reduction is experimentally determined so as to be set as large as possible within the range of a frequency causing no problem. 
     In this case, the respective percentages of area reduction are set such that in a case where the wire drawing process is performed via all of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ), the wire  10  has the smallest finished wire diameter among a plurality of types of finished wire diameters to be manufactured. Moreover, the percentage of area reduction is set such that in a case where the wire drawing process is performed via part of a plurality of second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) (that is, the wire is not wound around the remaining capstans, and corresponding dies are omitted), the wire  10  has one finished wire diameter among a plurality of types of finished wire diameters to be manufactured. In this case, a suitable speed command value is provided to the control unit  68  through the input part  68   a  and the speed command value is set and stored in the control unit  60  so as to obtain the above-mentioned drawing speed ratio, and the control unit  60  controls driving of the respective second rotation drive sources  44  in accordance with the control command value. 
     It is assumed here that the finished wire diameters of the strands  10   b  to be manufactured are 0.42 mm, 0.36 mm, 0.34 mm, 0.32 mm and 0.30 mm on the assumption of the case where those are used as the cores of the electric wires to be manufactured. 
     The percentage of area reduction between the first capstan  32 ( 8 ) and the second capstan  42 ( 9 ) is set to 16%, the percentage of area reduction between the second capstans  42 ( 9 ) and  42 ( 10 ) is set to 15%, the percentage of area reduction between the second capstans  42 ( 10 ) and  42 ( 11 ) is set to 14%, the percentage of area reduction between the second capstans  42 ( 11 ) and  42 ( 12 ) is set to 13%, the percentage of area reduction between the second capstans  42 ( 12 ) and  42 ( 13 ) is set to 12%, the percentage of area reduction between the second capstans  42 ( 13 ) and  42 ( 14 ) is set to 11%, and the percentage of area reduction between the second capstans  42 ( 14 ) and  42 ( 15 ) is set to 10%. Then, the diameter of the wire  10  is 0.45 mm at the time of being drawn by the second capstan  42 ( 9 ), is 0.42 mm at the time of being drawn by the second capstan  42 ( 10 ), is 0.39 mm at the time of being drawn by the second capstan  42 ( 11 ), is 0.36 mm at the time of being drawn by the second capstan  42 ( 12 ), is 0.34 mm at the time of being drawn by the second capstan  42 ( 13 ), is 0.32 mm at the time of being drawn by the second capstan  42 ( 14 ), and is 0.30 mm at the time of being drawn by the second capstan  42 ( 15 ). Accordingly, the strand  10   b  having the smallest diameter of 0.30 mm can be obtained in the case where the wire drawing process is performed via all of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). Alternatively, through the processes via ones up to the second capstan  42 ( 10 ), ones up to the second capstan  42 ( 12 ), ones up to the second capstan  42 ( 13 ), ones up to the second capstan  42 ( 14 ) and ones up to the second capstan  42 ( 15 ), it is possible to obtain the strands  10   b  having diameters of 0.42 mm, 0.36 mm, 0.34 mm and 0.32 mm to be manufactured. 
     That is, in the case of manufacturing the strand  10   b  having a diameter of 0.30, as shown in  FIG. 1  and  FIG. 2 , the wire  10  is wound around all of the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) and all of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). The dies  60  are disposed between ones among all of them, and the wires  10  are inserted through the all dies  60 . In this state, then, the respective first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) and the respective second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are rotated at rotational speeds so as to obtain the drawing speed ratios corresponding to the above-mentioned percentages of area reduction. Any one of rotational speeds is determined, whereby each of the actual rotational speeds is determined based on the determined one in accordance with the above-mentioned drawing speed ratio. Generally, a speed as high as possible is selected within the range where breaking of the wire  10  does not occur at a predetermined frequency or more on the most downstream side on which the wire speed becomes the highest. As a result, the wire  10  is sequentially processed through compression and deformation, whereby the strand  10   b  having the smallest diameter of 0.30 mm is manufactured. 
     For example, in the case of manufacturing a strand having a diameter of 0.32 mm, as shown in  FIG. 5 , part of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) and part of the dies  60  are omitted. More specifically, the wire  10  is caused to pass through without being around the second capstan  42 ( 14 ). In addition, the die  60  disposed between the second capstans  42 ( 14 ) and  42 ( 15 ) is removed, and the die  60  that has been disposed between the second capstans  42 ( 13 ) and  42 ( 14 ) is provided in that location. Not the second capstan  42 ( 15 ) on the most downstream side but the preceding second capstan  42 ( 14 ) is omitted because a motor having relatively large torque is selected as a finishing capstan in the second capstan  42 ( 15 ) on the most downstream side. 
     Also in the case of manufacturing the strand  10   b  having the other diameter of 0.42 mm, 0.36 mm or 0.34 mm, it can be manufactured in a similar manner to the above by omitting one or a plurality of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). 
     Accordingly, once the drawing speeds of a plurality of second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are set in accordance with the material of the wire  10 , a target diameter thereof or the like, it is possible to easily manufacture the strands  10  having a plurality of types of finished wire diameters depending on whether all of or part of a plurality of second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) is used. 
     Needless to say, the rotational speeds of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) may be changed or adjusted, or the dies  60  may be replaced in accordance with a finished wire diameter. 
     According to the wire drawing machine  20  configured as described above, in the first capstan mechanism part  30 , one first rotation drive source  34  is transmitted to a plurality of first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ) via the first rotation transmission mechanism part  36 , with the result that maintenance tasks can be simplified compared with the case of individually driving those by motors. In addition, in the second capstan mechanism part  40 , the rotational speeds of a plurality of second rotation drive sources  44  are individually adjusted and the rotational speeds of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are individually changed, with the result that the drawing speed ratio of the wire  10  can be changed between adjacent ones of the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ). This enables an easy response to the adjustment or change of the degree of diameter reducing deformation of the wire  10  in accordance with the material of the wire  10 , a target finished wire diameter or the like. 
     In the first capstan mechanism part  30 , the percentage of area reduction is set to a relatively large fixed value, and thus the wire drawing process can be performed with efficiency in the stage where the wire  10  has a relatively large diameter, resulting in a reduction of the number of the whole dies  60 . This contributes to reduction of a device size, cost or the like. 
     The drawing speed ratios between adjacent ones of the respective second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) are set so as to gradually decrease toward the downstream, that is, as the diameter of the wire  10  becomes smaller. That is, setting is made such that the degree of diameter reducing deformation by one die  60  becomes smaller as the diameter of the wire  10  becomes smaller. This prevents cutting of the wire  10  more reliably. 
       FIG. 6  is a schematic plan view showing a wire drawing machine  120  according to a modification. Similar components to those described in the embodiment above are denoted by the same reference numerals and description thereof is omitted, and differences are mainly described. 
     In the present modification, description is given of an example in which a finishing capstan located on the most downstream side is set to have a fixed drawing speed. The wire drawing machine  120  includes the wire supply part  22 , the wire pulling part  26 , a first capstan mechanism part  130 , a second capstan mechanism part  140 , a finishing capstan mechanism part  180  and the dies  60 . 
     Similarly to the first capstan mechanism part  30 , the first capstan mechanism part  130  is provided between the wire supply part  22  and the wire pulling part  26  on the side closer to the wire supply part  22  and includes a plurality of (in this case, three) first capstans  132 ( 1 ),  132 ( 2 ) and  132 ( 3 ) corresponding to the first capstans  32 ( 1 ),  32 ( 2 ), . . . ,  32 ( 6 ),  32 ( 7 ) and  32 ( 8 ), a first rotation drive source  134  corresponding to the first rotation drive source  34  and a first rotation transmission mechanism part  136  corresponding to the first rotation transmission mechanism part  36 . That is, this first capstan mechanism part  130  has a similar configuration to that of the first capstan mechanism part  30  except for a different number of first capstans  132 ( 1 ),  132 ( 2 ) and  132 ( 3 ) and a different number of rotation drive force transmission targets of the first rotation transmission mechanism part  136 . 
     Similarly to the second capstan mechanism part  40 , the second capstan mechanism part  140  is provided between the wire supply part  22  and the wire pulling part  26  on the side closer to the wire pulling part  26  than the first capstan mechanism part  130  and includes a plurality of (in this case, three) second capstans  142 ( 4 ),  142 ( 5 ) and  142 ( 6 ) corresponding to the second capstans  42 ( 9 ),  42 ( 10 ), . . . ,  42 ( 13 ),  42 ( 14 ) and  42 ( 15 ) and a plurality of (in this case, four) second rotation drive sources  144  corresponding to the second rotation drive sources  44 . That is, this second capstan mechanism part  140  has a similar configuration to that of the second capstan mechanism part  40  except for a different number of second capstans  142 ( 4 ),  142 ( 5 ) and  142 ( 6 ) and a different number of second rotation drive sources  144 . 
     The finishing capstan mechanism part  180  serves to draw the wire  10  at a constant drawing speed, is provided between the wire supply part  22  and the wire pulling part  26  on the side closer to the wire pulling part  26  than the second capstan mechanism part  140 , and includes a plurality of (in this case, three) finishing capstans  182 ( 7 ),  182 ( 8 ) and  182 ( 9 ), one finishing rotation drive source  182 , and a finishing transmission mechanism part  184  that transmits the rotation drive force of the finishing rotation drive source  182  to the plurality of finishing capstans  182 ( 7 ),  182 ( 8 ) and  182 ( 9 ). The plurality of (in this case, three) finishing capstans  182 ( 7 ),  182 ( 8 ) and  182 ( 9 ) have similar configurations to those of the plurality of first capstans  132 ( 1 ),  132 ( 2 ) and  132 ( 3 ), one finishing rotation drive source  182  has a similar configuration to that of the first rotation drive source  134 , and the finishing transmission mechanism part  184  has a similar configuration to that of the first rotation transmission mechanism part  136 . Accordingly, the drawing speed ratios between ones of the finishing capstans  182 ( 7 ),  182 ( 8 ) and  182 ( 9 ) in the finishing capstan mechanism part  180  have fixed given values. Needless to say, the number of finishing capstans  182 ( 7 ),  182 ( 8 ) and  182 ( 9 ) does not need to be the same as the number of the first capstans  132 ( 1 ),  132 ( 2 ) and  132 ( 3 ). Further, one drawing capstan may be provided. 
     Further, the dies  60  are respectively disposed between ones of the plurality of first capstans  132 ( 1 ),  132 ( 2 ) and  132 ( 3 ), the plurality of second capstans  142 ( 4 ),  142 ( 5 ) and  142 ( 6 ) and the plurality of finishing capstans  182 ( 7 ),  182 ( 8 ) and  182 ( 9 ). 
     This wire drawing machine  120  enables to perform the wire drawing process at a relatively large constant degree of diameter reducing deformation by the first capstan mechanism part  130 , perform the wire drawing process at a degree of diameter reducing deformation that is adjusted in accordance with a material of the wire  10  or the like by the second capstan mechanism part  140 , and perform the wire drawing process at a degree of diameter reducing deformation that is suitable for finishing by the finishing capstan mechanism part  180 . In particular, the finishing process can be performed on given conditions, leading to a merit of more stabilized finished quality. 
     While the description has been given by an example in which an aluminum wire or an aluminum alloy wire is assumed in the embodiment and modification above, those are also applicable to the wires  10  of various materials. That is, it suffices that the drawing speed ratios in the second capstan mechanism part  40 ,  140  are experimentally set or adjusted in accordance with the material of the wire  10 , a process diameter or the like. 
     While the description has been given assuming that the respective capstans have the same diameter, the respective diameters may differ from each other. In this case, the drawing speed may be taken as a value obtained by incorporating the diameter into the rotational speed. 
     Further, the case of a linear wire drawing process line L has been given in the embodiment above, which is not limited thereto. Alternatively, a line may be curved at each capstan portion or other guide roller portion. 
     While the wire drawing machine and the strand manufacturing method have been described in detail, the forgoing description is in all aspects illustrative, and the present invention is not limited thereto. It is therefore understood that numerous modifications and variations not illustrated can be devised without departing from the scope of the invention.