Abstract:
A polygon machining method whereby first polygon machining is carried out on a workpiece held by a main axis, by using a polygon cutter attached to a tool main axis, then machining using a tool other than the polygon cutter is carried out, and second polygon machining after said machining is carried out, using the polygon cutter. The polygon machining method comprises: a synchronized stopping step in which the main axis is stopped at a predetermined prescribed rotation position, in a state in which the main and the tool main axis during polygon machining are synchronously rotated when the first polygon machining has been completed; a synchronization release step in which the synchronization of the main axis and the tool main axis is released when starting machining after the first polygon machining; a main axis stopping step in which the main axis is stopped at a prescribed rotation position when the machining after first polygon machining has been completed; and a synchronization starting step in which the main axis and the tool main axis are synchronously rotated when starting second polygon machining.

Description:
FIELD 
       [0001]    The present invention relates to a polygon machining device and a polygon machining method. 
       BACKGROUND 
       [0002]    Polygon machining in which the outer peripheral surface of a workpiece is machined into a polygon or the like by using a polygon cutter is conventional. Polygon machining is carried out by rotating a workpiece gripped by a main shaft about the shaft line and by synchronously rotating the polygon cutter mounted to a tool spindle in a predetermined rotation ratio with respect to the workpiece. 
         [0003]    There is a polygon machining method in which polygon machining is carried out after matching the phase of a workpiece with that of the polygon cutter between each piece of the polygon machining in the case where a plurality of kinds of polygon machining is carried out on the outer peripheral surface of a workpiece (e.g., see Patent Document 1). 
       RELATED DOCUMENTS 
       [0004]    [Patent Document 1] Japanese Patent No. 5080120 
       SUMMARY 
     Technical Problem 
       [0005]    As described above, in the case where the polygon machining is carried out on the outer peripheral surface of a workpiece, first, it is necessary to carry out first polygon machining on the workpiece, then carry out deburring machining or the like to remove burrs generated on the outer peripheral surface of the workpiece in the first polygon machining on the workpiece on which the first polygon machining has been carried out, and to carry out second polygon machining to remove burrs generated on the inner peripheral surface of the workpiece in the first polygon machining on the workpiece on which the deburring machining or the like has been carried out after rotating the polygon cutter so that the position of the origin set on the rotary tool table and the polygon cutter are relatively in a predetermined arrangement relationship, and therefore there is a drawback in that the number of processes at the time of machining increases. 
         [0006]    An object of the present invention is to provide a polygon machining device and a polygon machining method for carrying out a plurality of pieces of polygon machining on a workpiece gripped by a main shaft that rotates by using a polygon cutter mounted to a tool spindle that rotates in synchronization with the main shaft. 
       Solution to Problem 
       [0007]    In order to implement the above-described object, according to the present invention, in a polygon machining device including a main shaft gripping a workpiece, a tool spindle to which a polygon cutter is mounted, and a control unit configured to control the rotation of the main shaft and the tool spindle, and being configured so as to carry out machining by a tool other than the polygon cutter on a workpiece after carrying out first polygon machining by the polygon cutter and to carry out second polygon machining by the polygon cutter after the machining, the control unit includes a synchronization stopping unit configured to stop the main shaft in a predetermined fixed rotation position in the state where the main shaft and the tool spindle are synchronously rotated at the time of the first polygon machining when the first polygon machining ends, a synchronization releasing unit configured to release the synchronization between the main shaft and the tool spindle when machining after the first polygon machining starts, a main shaft stopping unit configured to stop the main shaft in a fixed rotation position when machining after the first polygon machining ends, and a synchronization starting unit configured to synchronously rotate the main shaft and the tool spindle when the second polygon machining starts, and the control unit is configured so as to end the first polygon machining in the state where the synchronization stopping unit is in operation, to start machining after the first polygon machining by operating the synchronization releasing unit, to end machining after the first polygon machining in the state where the main shaft stopping unit is in operation, and to carry out the second polygon machining by operating the synchronization starting unit. 
         [0008]    In the present invention, a polygon machining method for carrying out machining by a tool other than a polygon cutter on a workpiece gripped by a main shaft after carrying out first polygon machining by the polygon cutter mounted to a tool spindle and for carrying out second polygon machining by the polygon cutter after the machining includes a synchronization stopping step of stopping the main shaft in a predetermined fixed rotation position in the state where the main shaft and the tool spindle are synchronously rotated at the time of the polygon machining when the first polygon machining ends, a synchronization releasing step of releasing the synchronization between the main shaft and the tool spindle when machining after the first polygon machining starts, a main shaft stopping step of stopping the main shaft in a fixed rotation position when machining after the first polygon machining ends; and 
         [0009]    a synchronization starting step of synchronously rotating the main shaft and the tool spindle when the second polygon machining starts, and 
         [0010]    the polygon machining method is configured so as to end the first polygon machining in the state where the synchronization stopping step is in operation, to start machining after the first polygon machining by operating the synchronization releasing step, to end machining after the first polygon machining in the state where the main shaft stopping step is in operation, and to carry out the second polygon machining by operating the synchronization starting step. 
       Advantageous Effects of Invention 
       [0011]    According to the present invention, it is possible to implement a polygon machining device and a polygon machining method for carrying out polygon machining on a workpiece gripped by a main shaft that rotates by using a polygon cutter mounted to a tool spindle that rotates in synchronization with the main shaft. According to the present invention, in the case where two kinds of polygon machining are carried out on the outer peripheral surface of a workpiece, it is possible to easily match the phase of the workpiece with the phase of the polygon cutter at both points in time, and therefore it is possible to accurately form a plurality of polygonal shapes in a predetermined phase relationship on the outer peripheral surface of the workpiece. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a section view illustrating an example of a configuration of a turret cutter holder that is mounted on a machine tool to which a polygon machining device according to the present invention can be applied; 
           [0013]      FIGS. 2A and 2B  are diagrams illustrating a state where a polygon cutter that is used in the polygon machining device according to an embodiment of the present invention is mounted to the turret cutter holder illustrated in  FIG. 3 , and  FIG. 2A  is a partial cutout side view and  FIG. 2B  is a partial cutout front view; 
           [0014]      FIG. 3  is a block diagram illustrating a control unit capable of carrying out the polygon machining method according to the embodiment of the present invention; 
           [0015]      FIG. 4  is a flowchart showing an operation flow of the polygon machining method according to the embodiment of the present invention; and 
           [0016]      FIGS. 5A to 5D  are diagrams explaining an example in which two kinds of polygon machining are carried out by the polygon machining method according to the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]      FIG. 1  is a section view illustrating an example of a configuration of a turret cutter holder that is mounted on a machine tool to which a polygon machining device according to the present invention can be applied.  FIGS. 2A and 2B  are diagrams illustrating a state where a polygon cutter that is used in the polygon machining device according to an embodiment of the present invention is mounted to the turret cutter holder illustrated in  FIG. 3 , and  FIG. 2A  is a partial cutout side view and  FIG. 2B  is a partial cutout front view. A turret cutter holder  10  is mounted on an automatic lathe, such as an NC lathe, which is a machine tool. The turret cutter holder  10  includes a cutter table main body  12  and a turret  14  that is supported revolvably by the cutter table main body  12 . 
         [0018]    The turret  14  has a hollow head part  20  having an outline in the shape of a column or prism and a shaft part  22  in the shape of a hollow cylinder extended concentrically in the shaft line direction from one end in the shaft line direction of the head part  20 . On the outer peripheral surface of the head part  20  of the turret  14 , a plurality of tool mount parts  24  to which a tool is mounted is provided for each predetermined indexed angle. It is possible to selectively mount a machining tool, such as a cutting tool  26 , and a rotary tool  28 , such as a drill and a milling cutter, to each tool mount part  24 . The shaft part  22  is supported by the cutter table main body  12  rotatably and movably in the shaft line direction. 
         [0019]    The turret  14  is engaged with the cutter table main body  12  so as to be capable of being disengaged therefrom via an engagement part  38 , and by disengaging the engagement part  38  by a servomotor  32  and by rotationally driving the shaft part  22 , the turret  14  is driven revolvably. The turret  14  is fixed in the indexed position on the cutter table main body  12 , and therefore it is possible to select a predetermined machining tool, by causing the engagement part  38  to engage in a predetermined revolving position of the turret  14 . 
         [0020]    Within the shaft part  22 , a drive shaft  42  that is driven rotationally by a servomotor  46  is supported pivotally. When the rotary tool  28  is mounted to the desired tool mount part  24  of the turret  14  via a holder  48  including the tool spindle, a driven gear  50  that is linked to the tool spindle engages with a drive gear  44  attached to the drive shaft  42  and the rotary tool  28  is driven rotationally by the servomotor  46 . 
         [0021]    To the predetermined tool mount part  24 , as illustrated in  FIG. 2 , it is possible to mount a polygon cutter  54  via a holder  60  including the tool spindle. When the polygon cutter  54  is mounted to the tool spindle of the holder  60  and a driven gear  62  that is linked to the polygon cutter  54  (tool spindle) via the power transmission within the holder  60  engages with the drive gear  44 , the polygon cutter  54  is driven rotationally by the servomotor  46 . 
         [0022]    It is possible to form an ellipse, a polygon, etc., on the outer peripheral surface of a workpiece W by carrying out polygon machining on the workpiece W gripped by the main shaft, by revolving the turret  14  to select the polygon cutter  54  and by synchronously rotating the main shaft that is driven rotationally by the main shaft motor and the polygon cutter  54  to maintain the phase relationship between the main shaft and the polygon cutter  54 . In the polygon machining, the tool spindle and the main shaft are driven rotationally so that the rotation speed of the workpiece W and the rotation speed of the polygon cutter  54  form a predetermined ratio. For example, in the case where a quadrangle is formed on the outer peripheral surface of the workpiece, it is possible to machine the quadrangle by rotating the polygon cutter in which two cutters, the number of cutters being half the number of angles of the quadrangle, are arranged twice while rotating the workpiece once. Further, for example, in the case where a hexagon is formed on the outer peripheral surface of the workpiece, it is sufficient to rotate the polygon cutter in which three cutters, the number of cutters being half the number of angles of the hexagon, are arranged so as to form, for example, a triangle three times while rotating the workpiece once. 
         [0023]    It is possible to carry out general cutting machining of the workpiece W with the shaft line of the main shaft as a center, by revolving the turret  14  to select the cutting tool  26 . For example, there is outer diameter machining of a workpiece using an outer diameter cutting tool or deburring machining to remove burrs generated on the outer peripheral surface of a workpiece. In the cutting machining, the polygon cutter  54  is not used, and therefore the synchronization between the main shaft and the tool spindle is not required and it is possible to set the rotation speed of the main shaft to a speed higher than that at the time of the polygon machining in an attempt to reduce the time taken by the workpiece machining. Normally, the maximum rotation speed of the tool spindle is set lower than the maximum rotation speed of the main shaft, and therefore in the case where the main shaft and the tool spindle are in synchronization, the maximum rotation speed of the main shaft is restricted by the maximum rotation speed of the tool spindle as a result. Thus, in the case of the above-described cutting machining, the synchronization between the main shaft and the tool spindle is released and the main shaft is driven rotationally at a rotation speed necessary for the cutting machining independently of the tool spindle. 
         [0024]      FIG. 3  is a block diagram illustrating a control unit capable of carrying out the polygon machining method according to the embodiment of the present invention. The drive of the tool spindle and the main shaft is controlled by the control unit illustrated in  FIG. 3 . The control unit includes an NC device  70  mounted on a numerical control (NC) lathe in the present embodiment. However, it is also possible to use another control device different from the NC device. 
         [0025]    The NC device  70  includes an input unit  72 , a display unit  74 , a processing unit (CPU)  76 , a storage unit (ROM  78  and RAM  80 ), a drive control unit  82 , etc. 
         [0026]    In the control device (NC device  70 ), the CPU  76  outputs an operation command to the drive control unit  82  based on various kinds of data, machining programs, etc., stored in the ROM  78  or the RAM  80 , and the control unit  82  controls the indexing drive source (servomotor)  32  and the rotation drive source (servomotor)  46  of the turret cutter holder  10  and, a drive mechanism  88 , such as a main shaft motor that drives the main shaft rotationally, respectively, and causes the turret  14  to revolve and the rotary tool  28  (tool spindle) and the main shaft to rotate. The control device is configured so as to be capable of switching between the synchronous drive and the asynchronous drive of the servomotor  46  (rotational drive of the rotary tool  28 ) and the main shaft motor (rotational drive of the main shaft). 
         [0027]      FIG. 4  is a flowchart showing an operation flow of the polygon machining method according to the embodiment of the present invention. 
         [0028]    First, at step S 101 , first polygon machining is carried out by the polygon cutter  54  by synchronously rotating the main shaft gripping the workpiece W and the tool spindle to which the polygon cutter  54  is mounted. 
         [0029]    After the first polygon machining, at step S 102 , the main shaft is stopped in a predetermined fixed point position while maintaining the synchronization between the main shaft and the tool spindle (i.e., phase relationship). The main shaft and the tool spindle are in synchronization, and therefore when the main shaft (workpiece) stops, the tool spindle (polygon cutter  54 ) also stops. As the fixed point position, the origin of the main shaft (position where the rotation angle of the main shaft is 0 degrees) or the like can be thought. 
         [0030]    Next, at step S 103 , the synchronization between the main shaft and the tool spindle is released and the main shaft is caused to rotate alone and the cutting machining is carried out on the workpiece gripped by the main shaft. At the time of the cutting machining at step S 103 , the polygon cutter  54  is retracted in advance. 
         [0031]    After the cutting machining, at step S 104 , the main shaft is stopped in the above-described fixed point position and the polygon cutter  54  in the retracted state is indexed. As a result, the phase relationship between the main shaft and the tool spindle becomes the same as that at step S 101 . The turret  14  is configured so that the phase of the tool spindle becomes the same before the retraction and after the indexing when the polygon cutter  54  temporarily retracts after stopping at step S 102  and is indexed again. 
         [0032]    The phase relationship between the main shaft and the tool spindle becomes the same as that at step S 101 , by the main shaft stopping in the above-described predetermined fixed point position, and therefore after step S 104 , second polygon machining is carried out by the polygon cutter  54  at step S 105 . 
         [0033]    As described above, the workpiece machining method according to the embodiment of the present invention includes: a synchronization stopping step (step S 102 ) of stopping the main shaft in a predetermined fixed rotation position in the state where the main shaft and the tool spindle are synchronously rotated at the time of polygon machining when the first polygon machining (step S 101 ) ends; a synchronization releasing step of releasing the synchronization between the main shaft and the tool spindle when the cutting machining (step S 103 ) starts; a main shaft stopping step (step S 104 ) of stopping the main shaft in a fixed rotation position when the cutting machining (step S 103 ) ends; and a synchronization starting step of synchronously rotating the main shaft and the tool spindle when the second polygon machining (step S 105 ) starts. The workpiece machining method is configured so as to end the first polygon machining (step S 101 ) in the state where the synchronization stopping step is in operation, to start the cutting machining (step S 103 ) by operating the synchronization stopping step, to end the cutting machining (step S 103 ) in the state where the main shaft stopping step is in operation, and to carry out the second polygon machining (step S 105 ) by operating the synchronization starting step. 
         [0034]    The polygon machining device that carrying out each piece of the above-described processing includes the main shaft gripping a workpiece, the tool spindle to which a polygon cutter is mounted, and the control unit configured to control the rotation of the main shaft and the tool spindle. The control unit includes: a synchronization stopping unit configured to stop the main shaft in a predetermined fixed rotation position in the state where the main shaft and the tool spindle are synchronously rotated at the time of the first polygon machining when the first polygon machining (step S 101 ) ends; a synchronization releasing unit configured to release the synchronization between the main shaft and the tool spindle when the cutting machining (step S 103 ) starts; a main shaft stopping unit configured to stop the main shaft in a fixed rotation position when the cutting machining (step S 103 ) ends; and a synchronization starting unit configured to synchronously rotate the main shaft and the tool spindle when the second polygon machining (step S 105 ) starts, and controls the rotation of the main shaft and the tool spindle so that the first polygon machining (step S 101 ) is ended in the state where the synchronization stopping unit is in operation, the cutting machining (step S 103 ) is started by operating the synchronization releasing unit, the cutting machining (step S 103 ) is ended in the state where the main shaft stopping unit is in operation, and the second polygon machining (step S 105 ) is carried out by operating the synchronization starting unit. 
         [0035]      FIGS. 5A to 5D  are diagrams explaining an example in which two kinds of polygon machining are carried out on the workpiece W gripped by the main shaft by using the polygon cutter  54  linked to the tool spindle and including three cutters  66  by the polygon machining method according to the embodiment of the present invention. The case is explained where two hexagons different in size are formed in the same phase on the outer peripheral surface of the workpiece W as illustrated in  FIG. 5A . 
         [0036]    First, at step S 201 , an outer diameter cutting tool  57  is indexed and the workpiece W gripped by the main shaft is guided by a guide bush  55 , and outer diameter machining (cutting machining) is carried out on the workpiece W. Next, at step S 202 , the polygon cutter  54  is indexed and the first polygon machining to form a hexagon is carried out on the portion of the workpiece W on which the outer diameter machining has been carried out as illustrated at step S 203 . After the polygon machining at step S 203 , the main shaft is stopped in the position of the main shaft origin (fixed point) while maintaining the synchronization (phase relationship) between the main shaft and the tool spindle. Next, at step S 204 , the outer diameter cutting tool  57  is indexed, the synchronization between the main shaft and the tool spindle is released, the main shaft is caused to rotate alone independently of the tool spindle, and the outer diameter machining is carried out on the workpiece W. After the cutting machining, the main shaft is stopped in the main shaft origin. Then, the polygon cutter  54  is indexed as illustrated at step S 205  and the second polygon machining to form a hexagon on the workpiece W is carried out. At the time of carrying out the first polygon machining and at the time of carrying out the second polygon machining, the phase of the polygon cutter  54  is the same as the phase of the workpiece W, and therefore it is possible to carry out the second polygon machining in the predetermined phase (in the present embodiment, in the same phase) with respect to the first polygon machining. Even in the case where cutting machining in which the phase of the polygon cutter  54  (tool spindle) and the phase of the workpiece W (main shaft) are not related is carried out between the first polygon machining and the second polygon machining, it is possible to easily carry out the polygon machining, which requires matching of the phase relationship therebetween, on the outer peripheral surface of the workpiece W only by stopping the main shaft in a predetermined fixed point position, such as the main shaft origin. 
       CITATION LIST 
       [0000]    
       
         
           
               10  turret cutter holder 
               12  cutter table main body 
               14  turret 
               20  head part 
               22  shaft part 
               24  tool mount parts 
               26  cutting tool 
               28  rotary tool 
               32  servomotor 
               38  engagement part 
               42  drive shaft 
               44  drive gear 
               46  servomotor 
               48  holder 
               50  driven gear 
               54  polygon cutter 
               55  guide bush 
               57  outer diameter cutting tool 
               60  holder 
               62  driven gear 
               66  cutters 
               70  NC device 
               72  input unit 
               74  display unit 
               76  CPU 
               78  ROM 
               80  RAM 
               82  drive control unit 
               84  movable structure 
               86  drive mechanism 
             W workpiece