Abstract:
Provided is a technique capable of accurately cutting steel sheets of various shapes into desired shapes. A cutting method is a method for cutting a steel sheet by using a nibbler having a cylindrical case, a punch housed inside the case, and a die provided below the case, the nibbler making the punch continuously punch the steel sheet while moving. The cutting method includes: providing a guide member in the vicinity of the die of the nibbler located at a cutting position along a moving path of the nibbler, the guide member having a first guide surface for restricting movement of the nibbler from the cutting position to a first side of a direction perpendicular to a traveling direction and a top-bottom direction of the nibbler by contact with a side surface of the die; and moving the nibbler along the guide member.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a cutting apparatus and a cutting method for cutting a steel sheet. 
       BACKGROUND ART 
       [0002]    Conventionally, a nibbler is widely known as a device for cutting a steel sheet. 
         [0003]    Generally, the nibbler includes a cylindrical case, a punch arranged in the case, and a die arranged below the case. The nibbler makes the punch continuously punch a steel sheet fed between the case and the die while moving, thereby cutting the steel sheet. 
         [0004]    JP 9-234622 A discloses a nibbler configured to be grasped and moved by an operator to cut a steel sheet. 
         [0005]    The nibbler described in JP 9-234622 A can move linearly by sliding a linear guide plate of a cutting jig mounted on the nibbler on the side edge of the rectangular steel sheet. 
         [0006]    Furthermore, the nibbler described in JP 9-234622 A can move circularly around a hole formed in a steel sheet by inserting a center part of the cutting jig mounted on the nibbler into the hole. 
         [0007]    However, it is disadvantageous in that the nibbler described in JP 9-234622 A can linearly cut only a steel sheet having a linear side edge (e.g., a rectangular steel sheet) because the nibbler cut the steel sheet linearly by utilizing the linear guide plate of the cutting jig, which slides on the side edge of the steel sheet. 
         [0008]    Moreover, the nibbler described in JP 9-234622 A can cut the steel sheet circularly by utilizing the center part of the cutting jig, which is inserted into the hole formed in the steel sheet, but has a disadvantage of not cutting the steel sheet in a complicated curve. 
       CITATION LIST 
     Patent Literature 
       [0009]    PTL1: JP 9-234622 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    The object of the present invention is to provide a technique capable of accurately cutting steel sheets of various shapes into desired shapes. 
       Solution to Problem 
       [0011]    A first aspect of the invention is a cutting method for cutting a steel sheet by using a nibbler having a cylindrical case, a punch housed inside the case, which reciprocates in a top-bottom direction, and a die provided below the case, the nibbler making the punch continuously punch the steel sheet fed between the case and the die while moving, the cutting method including: providing a guide member in the vicinity of the die of the nibbler located at a cutting position along a moving path of the nibbler, the guide member having a first guide surface for restricting movement of the nibbler from the cutting position to a first side of a direction perpendicular to a traveling direction of the nibbler and the top-bottom direction by contact with a side surface of the die of the nibbler located at the cutting position; and moving the nibbler along the guide member. 
         [0012]    Preferably, the guide member further has a second guide surface for restricting downward movement of the nibbler from the cutting position by contact with a lower surface of the die of the nibbler located at the cutting position. 
         [0013]    Preferably, the guide member further has a third guide surface arranged on a side opposite to the first guide surface with respect to the die, for restricting movement of the nibbler from the cutting position to a second side of the direction perpendicular to the traveling direction of the nibbler and the top-bottom direction by contact with a side surface of the die of the nibbler located at the cutting position. 
         [0014]    Preferably, the guide member comes in contact with a lower surface of a removed part that is an unnecessary part of the steel sheet to support the removed part from below. 
         [0015]    Preferably, a part of the guide member, which is come in contact with the removed part of the steel sheet is made of a buffer material. 
         [0016]    Preferably, the above-mentioned method further includes: mounting the nibbler on a robot having an arm capable of changing a position and a posture of the arm; and controlling the robot to move the nibbler along the guide member. 
         [0017]    A second aspect of the invention is a cutting apparatus for cutting a steel sheet, including: at least one robot having an arm capable of changing a position and a posture of the arm; a nibbler that has a cylindrical case, a punch housed inside the case, which reciprocates in a top-bottom direction to punch the steel sheet, and a die provided below the case, and that is mounted on a tip of the arm of the robot; a guide member provided in the vicinity the die of the nibbler located at a cutting position along a moving path of the nibbler; and a controller that controls the robot to move the nibbler along the guide member. The guide member has a first guide surface for restricting movement of the nibbler from the cutting position to a first side of a direction perpendicular to a traveling direction of the nibbler and the top-bottom direction by contact with a side surface of the die of the nibbler located at the cutting position. 
         [0018]    Preferably, the guide member further has a second guide surface for restricting downward movement of the nibbler from the cutting position by contact with a lower surface of the die of the nibbler located at the cutting position. 
         [0019]    Preferably, the guide member further has a third guide surface arranged on a side opposite to the first guide surface with respect to the die, for restricting movement of the nibbler from the cutting position to a second side of the direction perpendicular to the traveling direction of the nibbler and the top-bottom direction by contact with a side surface of the die of the nibbler located at the cutting position. 
         [0020]    Preferably, the guide member comes in contact with a lower surface of a removed part that is an unnecessary part of the steel sheet to support the removed part from below. 
         [0021]    Preferably, a part of the guide member, which is come in contact with the removed part of the steel sheet is made of a buffer material. 
       Advantageous Effects of Invention 
       [0022]    The present invention makes it possible to accurately cut steel sheets of various shapes into desired shapes. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]      FIG. 1  shows a cutting apparatus according to an embodiment of the present invention. 
           [0024]      FIG. 2  shows a nibbler provided in the cutting apparatus according to the embodiment of the present invention, in which  FIG. 2A  is a sectional side view, and  FIG. 2B  is a sectional view taken along line A-A in  FIG. 2A . 
           [0025]      FIG. 3  is a plan view of a steel sheet, showing a moving path of the nibbler. 
           [0026]      FIG. 4  shows a guide member. 
           [0027]      FIG. 5  shows the guide member. 
           [0028]      FIG. 6  shows another embodiment of the guide member and another embodiment of the nibbler. 
           [0029]      FIG. 7  shows another embodiment of the guide member. 
           [0030]      FIG. 8  shows another embodiment of the guide member and another embodiment of the nibbler. 
           [0031]      FIG. 9  shows another embodiment of the guide member. 
           [0032]      FIG. 10  shows another embodiment of the guide member. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0033]    With reference to  FIGS. 1 to 3 , a cutting apparatus  1  as an embodiment of a cutting apparatus according to the present invention is described below. 
         [0034]    The cutting apparatus  1  cuts a workpiece W. 
         [0035]    The workpiece W is a steel sheet having a central part protruding upward, and a flange horizontally extending, which is formed around the central part. 
         [0036]    As shown in  FIG. 1 , the cutting apparatus  1  includes a support stand  10 , a lower die  20 , a guide member  30 , a robot  40 , a nibbler  50 , and a controller  60 . 
         [0037]    The support stand  10  is a stand that supports the lower die  20  and the guide member  30 . On the support stand  10 , the lower die  20  and the guide member  30  are fixed. 
         [0038]    The lower die  20  is a member on which the workpiece W is placed. The lower die  20  is configured to fix the workpiece W. The lower die  20  supports only the central part of the workpiece W such that the flange of the workpiece W is located outside the lower die  20 . 
         [0039]    The guide member  30  is a member that guides the nibbler  50  such that the nibbler  50  does not deviate from a predetermined moving path. The guide member  30  is provided along the moving path of the nibbler  50  so as to surround the lower die  20 , and arranged below the flange of the workpiece W. 
         [0040]    A detailed structure of the guide member  30  will be described later. 
         [0041]    The robot  40  has an arm with multiple joints. The robot  40  is configured to change a position and a posture of the arm. The nibbler  50  is mounted on the tip of the arm of the robot  40 . 
         [0042]    As shown in  FIGS. 2A and 2B , the nibbler  50  is a device that continuously punches the workpiece W while moving. The nibbler  50  includes a case  51 , a punch  52 , a supporting part  53 , a die body  54 , and a driving part  55 . 
         [0043]    For convenience, the top-bottom direction in  FIG. 2A  is defined as a top-bottom direction of the nibbler  50 . 
         [0044]    The case  51  is formed in substantially a cylinder extending in the top-bottom direction, and has an opened lower end part. 
         [0045]    The punch  52  is housed in the case  51  so as to slide in the top-bottom direction. 
         [0046]    The supporting part  53  for supporting the case  51  and the die body  54  is fixed to the inner circumferential surface of the case  51 . 
         [0047]    The punch  52  reciprocates in the top-bottom direction at a predetermined frequency to punch the workpiece W. The punch  52  has a blade  52   a  and a connecting part  52   b.    
         [0048]    The blade  52   a  has a sectional shape of substantially a horseshoe, and the lower end thereof is formed as a blade edge for punching the workpiece W. The blade  52   a  protrudes downward from the lower end of the case  51  to enter an after-mentioned die hole  54   a  when the punch  52  arrives at the bottom dead center. 
         [0049]    The connecting part  52   b  is connected to the driving part  55  such that the driving part  55  reciprocates the punch  52  in the top-bottom direction. 
         [0050]    The supporting part  53  is a member that supports the case  51  and the die body  54 . The upper end part of the supporting part  53  is fixed to the inner circumferential surface of the case  51 , and the supporting part  53  extends downward from the inside of the case  51 . The supporting part  53  has such a shape that an opening coincident with the sectional shape of the blade  52   a  is formed on the lower end surface of the case  51 . In other words, a space in which the punch  52  is housed is formed between the case  51  and a part of the supporting part  53  inserted into the case  51 , and the opening formed on the lower end surface of the case  51  has the shape coincident with the sectional shape of the blade  52   a.    
         [0051]    The die body  54  is fixed to the lower end part of the supporting part  53 . 
         [0052]    The die body  54  is arranged below the case  51  so as to be on the opposite side of the case  51  across the workpiece W. The die body  54  is formed in substantially a cylinder. The die body  54  is fixed to the supporting part  53  so as to cover the lower end part of the supporting part  53 . The die body  54  has the die hole  54   a  and an ejecting hole  54   b.    
         [0053]    The die hole  54   a  is formed such that the blade  52   a  enters thereinto when the punch  52  arrives at the bottom dead center. Specifically, the die hole  54   a  is formed between the die body  54  and a part of the supporting part  53  inserted into the die body  54 . The die hole  54   a  has a shape coincident with the sectional shape of the blade  52   a,  and opens on the upper end surface of the die body  54 . 
         [0054]    The ejecting hole  54   b  is a hole through which a crescentic scrap S punched from the workpiece W by the punch  52  is ejected to the outside of the die body  54 . The ejecting hole  54   b  is formed on the side surface of the die body  54 , and communicates with the die hole  54   a.    
         [0055]    The die body  54 , and the part of the supporting part  53  inserted into the die body  54  correspond to a “die” according to the present invention. 
         [0056]    The driving part  55  reciprocates the punch  52  in the top-bottom direction at a predetermined frequency. The driving part  55  has a connecting part  55   a,  a rod  55   b,  and a motor  55   c.    
         [0057]    The connecting part  55   a  is connected to the connecting part  52   b  of the punch  52 . 
         [0058]    The rod  55   b  is connected to the motor  55   c  and the connecting part  55   a  so as to transmit power of the motor  55   c  to the connecting part  55   a.    
         [0059]    The motor  55   c  transmits the power to the connecting part  55   a  through the rod  55   b.  Revolution of the motor  55   c  is converted into vertical movement of the connecting part  55   a  through the rod  55   b.    
         [0060]    As mentioned above, the nibbler  50  makes the punch  52  reciprocate in the top-bottom direction (direction in which punch  52  moves into and out of proximity with the die body  54 ) while being moved by the robot  40  with the workpiece W interposed between the case  51  and the die body  54 , thereby continuously punching the workpiece W. 
         [0061]    As shown in  FIG. 1 , the controller  60  is electrically connected to the robot  40  and controls the robot  40 . The controller  60  controls the robot  40  such that the nibbler  50  mounted on the tip of the arm of the robot  40  moves along a preset path. 
         [0062]    As shown in  FIG. 3 , in the present embodiment, the controller  60  controls the robot  40  such that the nibbler  50  moves over the whole circumference of the flange of the workpiece W to remove a removed part Wr that is an unnecessary part of the flange of the workpiece W. 
         [0063]      FIG. 3  is a plan view of the workpiece W, and the arrow on the workpiece W shows a moving path of the nibbler  50 . In the present embodiment, the workpiece W is formed in substantially rectangle in plan view. 
         [0064]    With reference to  FIGS. 4 to 5 , a structure of the guide member  30  is hereinafter described in detail. 
         [0065]    As shown in  FIG. 4 , the guide member  30  is arranged in the vicinity of the die body  54  of the nibbler  50  located at a position in cutting of the workpiece W (hereinafter referred to as a “cutting position”) on a side closer to the lower die  20  than the nibbler  50 , namely on a side opposite to the removed part Wr of the workpiece W. The guide member  30  is continuously formed along the moving path of the nibbler  50  so as to surround the lower die  20  (see  FIG. 3 ). 
         [0066]    As shown in  FIGS. 4 and 5 , the guide member  30  has a first guide surface  30   a  and a second guide surface  30   b.    
         [0067]    The first guide surface  30   a  is formed in the vertical direction so as to be in contact with a side surface, on a side close to the lower die  20 , of the die body  54  of the nibbler  50  located at the cutting position. The first guide surface  30   a  is continuously formed along the moving path of the nibbler  50  so as to be always in contact with the side surface of the die body  54  when the nibbler  50  cuts the workpiece W. 
         [0068]    The thus formed first guide surface  30   a  restricts movement of the die body  54  to a side closer to the lower die  20  than the first guide surface  30   a  when the nibbler  50  cuts the workpiece W. 
         [0069]    Consequently, the controller  60  controls the robot  40  to slide the die body  54  on the first guide surface  30   a,  so that it is possible to suppress deviation of the nibbler  50  from the moving path. 
         [0070]    Accordingly, the workpiece W can be accurately cut in a desired shape regardless of the shape of the workpiece W. 
         [0071]    The second guide surface  30   b  is horizontally formed so as to be in contact with the lower surface of the die body  54  of the nibbler  50  located at the cutting position. The second guide surface  30   b  is continuous to the first guide surface  30   a,  and extends from the lower end of the first guide surface  30   a  toward a side close to the removed part Wr of the workpiece W. The second guide surface  30   b  is formed so as to be in contact with a part, on a side close to the lower die  20 , of the lower surface of the die body  54  of the nibbler  50  located at the cutting position. The second guide surface  30   b  is continuously formed along the moving path of the nibbler  50  so as to be always in contact with the lower surface of the die body  54  when the nibbler  50  cuts the workpiece W. 
         [0072]    The thus formed second guide surface  30   b  restricts downward movement of the die body  54  with respect to the second guide surface  30   b  when the nibbler  50  cuts the workpiece W. 
         [0073]    Consequently, the controller  60  controls the robot  40  to slide the die body  54  on the second guide surface  30   b,  so that it is possible to hold a position, in the vertical direction to the workpiece W, of the nibbler  50 , and to properly cut the workpiece W. 
         [0074]    Particularly, even in a case where the flange of the workpiece W has a shape curved such that the vertical position is displaced, it is possible to hold the position, in the vertical direction to the workpiece W, of the nibbler  50 , and to properly cut the workpiece W. 
         [0075]    The second guide surface  30   b  is formed so as not to be located below the ejecting hole  54   b  formed in the die body  54  of the nibbler  50  located at the cutting position. In other words, the second guide surface  30   b  is formed so as to be located between the first guide surface  30   a  and the ejecting hole  54   b.    
         [0076]    Consequently, the scrap S punched from the workpiece W can be prevented from being ejected on the second guide surface  30   b  and hindering movement of the nibbler  50 . 
         [0077]    The thus configured guide member  30  guides the nibbler  50  such that the nibbler  50  does not deviate from the moving path, when the nibbler  50  cuts the workpiece W. In other words, the nibbler  50  is moved so as to slide the die body  54  on the first guide surface  30   a  and the second guide surface  30   b  of the guide member  30 , so that the workpiece W can be accurately cut without deviation of the nibbler  50  from the moving path. 
         [0078]    The guide member  30  is formed with the first guide surface  30   a  and the second guide surface  30   b  in the present embodiment, but may be formed with at least the first guide surface  30   a.    
         [0079]    Additionally, there can be provided a guide member formed with only a first guide surface, and a guide member formed with only a second guide surface. 
         [0080]    In the present embodiment, the guide member  30  is provided on the side closer to the lower die  20  than the nibbler  50  located at the cutting position, and the first guide surface  30   a  restricts the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 . However, a guide member configured in a substantially similar manner to the guide member  30  may be provided on a side closer to the removed part Wr of the workpiece W than the nibbler  50  in place of the guide member  30 , and a first guide surface of this guide member may restrict movement of the nibbler  50  from the cutting position to the side close to the removed part Wr of the workpiece W. In other words, the first guide surface of the guide member may restrict movement of the nibbler  50  from the cutting position to one side of a direction perpendicular to the advancing direction of the nibbler  50  along a horizontal plane (strictly, a surface of a part, punched by the punch  52  of the nibbler  50 , of the flange of the workpiece W). 
         [0081]    However, the guide member is provided on the side closer to the lower die  20  than the nibbler  50  located at the cutting position, so that the guide member is not located below the removed part Wr of the workpiece W, and the removed part Wr is ejected without staying on the guide member when being removed from the workpiece W completely. Therefore, the guide member is preferably provided on the side closer to the lower die  20  than the nibbler  50  located at the cutting position. 
         [0082]    In the present embodiment, the die body  54  of the nibbler  50  abuts on the first guide surface  30   a  and the second guide surface  30   b  formed in the guide member  30 , so that the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 , and the downward movement of the nibbler  50  from the cutting position are restricted. However, the present invention is not limited to this configuration. 
         [0083]    For example, as shown in  FIG. 6 , a protrusion  53   a  is provided as a part of the die on the lower end surface of the supporting part  53  of the nibbler  50 , and a guide member  130  is provided in place of the guide member  30 , so that the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 , and the downward movement of the nibbler  50  from the cutting position may be restricted. 
         [0084]    The protrusion  53   a  is formed in a columnar shape having a smaller outer diameter than the die body  54 , and protrudes downward from the lower end surface of the supporting part  53 . 
         [0085]    The guide member  130  is arranged below the flange of the workpiece W on a side closer to the lower die  20  than the nibbler  50  located at the cutting position. The guide member  130  has a rectangular sectional shape, and is continuously formed along the moving path of the nibbler  50  so as to surround the lower die  20 . The guide member  130  is formed such that a side surface, on a side close to the removed part Wr, of the workpiece W is in contact with the side surface of the die body  54  of the nibbler  50  located at the cutting position, and an upper surface is in contact with the lower surface of the die body  54  of the nibbler  50  located at the cutting position. 
         [0086]    With such a configuration, the controller  60  controls the robot  40  to slide the protrusion  53   a  on the side surface of the guide member  130 , and to slide the die body  54  on the upper surface of the guide member  130 , so that the workpiece W can be accurately cut without deviation of the nibbler  50  from the moving path. In other words, the side surface, on the side close to the removed part Wr of the workpiece W, of the guide member  130  functions as the first guide surface according to the present invention, and the upper surface of the guide member  130  functions as the second guide surface according to the present invention. 
         [0087]    In the present embodiment, the guide member  30  is provided on the side closer to the lower die  20  than the nibbler  50  located at the cutting position, and the first guide surface  30   a  restricts the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 . However, it is also possible to restrict both the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 , and the movement of the nibbler  50  from the cutting position to the side close to the removed part Wr of the workpiece W. 
         [0088]    For example, as shown in  FIG. 7 , a guide member  31  may be further provided in addition to the guide member  30 . 
         [0089]    The guide member  31  is arranged below the flange of the workpiece W on a side closer to the removed part Wr of the workpiece W than the nibbler  50  located at the cutting position. In other words, the guide member  31  is arranged below the removed part Wr of the workpiece W. The guide member  31  has a rectangular sectional shape, and is continuously formed along the moving path of the nibbler  50 . On a side surface, on a side close to the lower die  20 , of the guide member  31 , a third guide surface  31   a  that is in contact with the side surface of the die body  54  of the nibbler  50  located at the cutting position is formed. 
         [0090]    With such a configuration, the controller  60  controls the robot  40  to slide the die body  54  on the first guide surface  30   a  of the guide member  30  and on the third guide surface  31   a  of the guide member  31 , so that it is possible to suppress deviation of the nibbler  50  from the moving path. 
         [0091]    Particularly, the guide member  31  is provided such that the die body  54  is sandwiched between the guide member  31  and the guide member  30 , and therefore the workpiece W can be cut with extremely high accuracy. In other words, the first guide surface  30   a  of the guide member  30  functions as a first guide surface according to the present invention, which restricts the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 , and the third guide surface  31   a  of the guide member  31  functions as a third guide surface according to the present invention, which restricts the movement of the nibbler  50  from the cutting position to the side close to the removed part Wr of the workpiece W. 
         [0092]    A surface similar to the second guide surface  30   b  of the guide member  30  can be formed in the guide member  31 . 
         [0093]    As shown in  FIG. 8 , a sphere  53   b  is provided as a part of the die on the lower end of the supporting part  53  of the nibbler  50 , and a guide member  230  is provided in place of the guide member  30 , so that the movement of the nibbler  50  from the cutting position to the side close to the lower die  20 , the movement of the nibbler  50  from the cutting position to the side close to the removed part Wr of the workpiece W, and the downward movement of the nibbler  50  from the cutting position may be restricted. 
         [0094]    The sphere  53   b  is formed in a spherical shape having the substantially similar outer diameter to the outer diameter of the lower end surface of the supporting part  53 . The sphere  53   b  has a lower part fixed to the supporting part  53  so as to protrude downward from the lower end surface of the supporting part  53 . 
         [0095]    The guide member  230  is arranged below the flange of the workpiece W so as to support the nibbler  50  located at the cutting position. The guide member  230  has a substantially rectangular sectional shape, and is continuously formed along the moving path of the nibbler  50  so as to surround the lower die  20 . A groove  230   a  having a circular arc sectional shape allowing the sphere  53   b  to be fit is formed in the upper surface of the guide member  230  along the moving path of the nibbler  50  continuously. The guide member  230  is formed such that the surface of the groove  230   a  is in contact with the surface of the lower part of the sphere  53   b  in the nibbler  50  located at the cutting position. 
         [0096]    With such a configuration, the controller  60  controls the robot  40  to slide the sphere  53   b  on the surface of the groove  230   a  of the guide member  230 , so that the workpiece W can be cut with extremely high accuracy without deviation of the nibbler  50  from the moving path. In other words, the surface of the groove  230   a  of the guide member  230  functions as the first guide surface, the second guide surface, and the third guide surface according to the present invention. The sphere  53   b  can be rotatably mounted on the supporting part  53 . 
         [0097]    As shown in  FIG. 9 , a guide member  330  can be provided in place of the guide member  30 . 
         [0098]    The guide member  330  is arranged below the flange of the workpiece W on a side closer to the removed part Wr of the workpiece W than the nibbler  50  located at the cutting position. In other words, the guide member  330  is arranged below the removed part Wr of the workpiece W. The guide member  330  is configured such that an upper surface thereof is in contact with the lower surface of the removed part Wr of the workpiece W. In other words, the guide member  330  is configured so as to support the removed part Wr of the workpiece W from below. The guide member  330  is continuously formed along the moving path of the nibbler  50  so as to surround the lower die  20 . The guide member  330  has a first guide surface  330   a  and a second guide surface  330   b.    
         [0099]    The first guide surface  330   a  is vertically formed so as to be in contact with a side surface, on a side close to the removed part Wr of the workpiece W, of the die body  54  of the nibbler  50  located at the cutting position. The first guide surface  330   a  is continuously formed along the moving path of the nibbler  50  so as to be always in contact with the side surface of the die body  54  when the nibbler  50  cuts the workpiece W. 
         [0100]    The second guide surface  330   b  is horizontally formed so as to be in contact with the lower surface of the die body  54  of the nibbler  50  located at the cutting position. The second guide surface  330   b  is continuous to the first guide surface  330   a,  and extends from the lower end of the first guide surface  330   a  toward the side close to the lower die  20 . The second guide surface  330   b  is formed so as to be in contact with a part, on the side close to the removed part Wr of the workpiece W, of the lower surface of the die body  54  of the nibbler  50  located at the cutting position. The second guide surface  330   b  is continuously formed along the moving path of the nibbler  50  so as to be always in contact with the lower surface of the die body  54  when the nibbler  50  cuts the workpiece W. 
         [0101]    The thus configured guide member  330  guides the nibbler  50  such that the nibbler  50  does not deviate from the moving path when the nibbler  50  cuts the workpiece W. In other words, the controller  60  controls the robot  40  to slide the die body  54  on the first guide surface  330   a  and the second guide surface  330   b  of the guide member  330 , so that it is possible to accurately cut the workpiece W without deviation of the nibbler  50  from the moving path. 
         [0102]    Furthermore, the guide member  330  is configured so as to support the removed part Wr of the workpiece W, and therefore it is possible to reduce vertical vibration of the removed part Wr of the workpiece W when the nibbler  50  cuts the workpiece W. 
         [0103]    Accordingly, it is possible to reduce noise generated when the removed part Wr of the workpiece W collides with the guide member  330 . 
         [0104]    As shown in  FIG. 10 , a part, in contact with the removed part Wr of the workpiece W, of the guide member  330  is preferably a buffer part  330   c.    
         [0105]    The buffer part  330   c  is made of a buffer material, and the removed part Wr of the workpiece W can reduce impact generated when colliding with the buffer part  330   c.    
         [0106]    Accordingly, the buffer part  330   c  is provided in the guide member  330 , so that it is possible to further reduce the noise generated when the removed part Wr of the workpiece W collides with the guide member  330 . 
         [0107]    A guide member different from the guide member  330  is provided on the side closer to the lower die  20  than the nibbler  50  located at the cutting position, and the die body  54  can be sandwiched between the above guide member and the guide member  330 . 
         [0108]    Consequently, the workpiece W can be cut with extremely high accuracy. 
         [0109]    In the present embodiment, the nibbler  50  is moved such that a part of the die (the die body  54 , the protrusion  53   a,  or the sphere  53   b ) of the nibbler  50  located at the cutting position slides on the guide member. However, the nibbler  50  can be moved so as to form a minute clearance between the die of the nibbler  50 , and the guide member. In other words, positional relation between the nibbler  50  and the guide member can be maintained when the nibbler  50  cuts the workpiece W, and the nibbler  50  can abut on the guide member to restrict movement of the nibbler  50  in a predetermined direction in a case where the nibbler  50  moves so as to deviate from the moving path. 
         [0110]    The number of the robots  40  in the cutting apparatus  1  is not limited, and at least one robot  40  mounted with the nibbler  50  may be provided. 
         [0111]    In a case where two or more robots  40  are provided, at least one robot  40  should be mounted with the nibbler  50 . 
         [0112]    Additionally, an operator can hold the nibbler to cut a steel sheet along the guide member according to the present invention. 
       INDUSTRIAL APPLICABILITY 
       [0113]    The present invention is applicable to a cutting apparatus and a cutting method for cutting a steel sheet. 
       REFERENCE SIGNS LIST 
       [0114]      1 : cutting apparatus 
         [0115]      10 : support stand 
         [0116]      20 : lower die 
         [0117]      30 : guide member 
         [0118]      30   a:  first guide surface 
         [0119]      30   b:  second guide surface 
         [0120]      31 : guide member 
         [0121]      31   a:  third guide surface 
         [0122]      40 : robot 
         [0123]      50 : nibbler 
         [0124]      54 : die body 
         [0125]      60 : controller 
         [0126]    W: workpiece (steel sheet) 
         [0127]    Wr: removed part