Abstract:
This machine tool is provided with an arithmetic control unit that: controls a motor so as to measure the positions of raw material holes in a boom using an imaging camera held on a main shaft (S 111 -S 113 ); calculates the positions of the center axes of the raw material holes on the basis of the information about the positions of the raw material holes captured by the imaging cameras (S 114 , S 115 ); calculates distances between two center axes of interest (S 116 ); and, when at least one of the calculated distances does not meet a prescribed value (S 117 ), calculates the most suitable positions for process holes from minimum holes that comply with formulae (1111-1) to (1114-1) and (1141-1) to (1144-1) on the basis of equations (1101), (1111) to (1114), and (1141) to (1144) (S 121 ); and controls the motor so as to form process holes in the positions calculated as the most suitable and cuts raw material holes using a tool held on the main shaft (S 122 , S 123 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a machine tool. 
       BACKGROUND ART 
       [0002]    The boom of, for example, an excavator sometimes includes a pair of plate members which are disposed in mutually facing postures and in each of which a plurality of holes are formed at predetermined positions for pivotally supporting an arm, a hydraulic cylinder, and the like, and a joint member joining and fixing the plate members to each other. In the case of such a boom, shafts cannot be inserted and supported in the mutually facing holes if the axes of these mutually facing holes are offset from each other. For this reason, after the plate members are disposed in the mutually facing postures and joined and fixed to each other with the joint member, mutually facing blank holes in the plate members are cut to expand their diameters with, for example, a horizontal boring and milling machine with counter spindles or the lie, so that the blank holes are worked and adjusted into worked holes positioned coaxially with each other. 
       CITATION LIST 
     Patent Literature 
       [0003]    Patent Literature 1: Japanese Patent Application Publication No. 2006-102843 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    In the case of the boom of an excavator as mentioned above, when the mutually facing blank holes are worked and adjusted into coaxially positioned worked holes, an error greater than or equal to a prescribed value (tolerance) may be present in the distance (pitch) between the axis of one worked hole and the axis of another worked hole. In this case, a hydraulic cylinder or the like cannot be joined between these worked holes, which makes the boom a defective product. 
         [0005]    Such a problem is not limited to the case mentioned above where the mutually facing blank holes in the boom of an excavator are worked and adjusted into worked holes by cutting the blank holes to expand their diameters with a horizontal boring and milling machine with counter spindles or the like. The problem possibly occurs like the above case when n blank holes (n is an integer greater than or equal to 3) formed in a workpiece are to be worked and adjusted into worked holes by cutting the blank holes to expand their diameters with a machine tool. 
         [0006]    In view of the above, an object of the present invention is to provide a machine tool capable of working and adjusting n blank holes (n is an integer greater than or equal to 3) formed in a workpiece into worked holes by cutting the blank holes to expand their diameters such that the blank holes are worked and adjusted to such optimized positions that the pitch error between the worked holes can be less than or equal to a tolerance. 
       Solution to Problem 
       [0007]    A machine tool according to the present invention for solving the above problem is a machine tool for working and adjusting n blank holes (n is an integer greater than or equal to 3) formed in a workpiece into worked holes by cutting the blank holes to expand diameters thereof, characterized in that the machine tool comprises: a table on which the workpiece is placed; a spindle capable of detachably holding a tool for cutting the blank holes in the workpiece and measurement means for measuring positions of the blank holes in the workpiece such that the tool and the measurement means are capable of being changed from one another; spindle drive means for rotationally driving the spindle; relative movement means for moving at least one of the table and the spindle to move the tool and the measurement means relative to the workpiece in an X-axis direction, a Y-axis direction, and a Z-axis direction; and arithmetic control means for controlling the relative movement means such that the positions of the blank holes in the workpiece are measured with the measurement means held on the spindle, calculating positions of center axes of the blank holes based on information on the positions of the blank holes measured with the measurement means, calculating a distance between each two center axes of interest among the center axes, in a case where at least one of the calculated distances does not satisfy a prescribed value, calculating optimized positions of the worked holes from minimized values satisfying Inequalities (110-1), (120-1), (130-1), (140-1), (150-1) below based on Equations (100), (110), (120), (130), (140), (150) below, and controlling the spindle drive means and the relative movement means to cut the blank holes with the tool held on the spindle such that the worked holes are formed at the calculated optimized positions of the worked holes. 
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         [0008]    Here, MX ki  is a position of a center axis of a blank hole G k  in the X-axis direction, MY ki  is a position of the center axis of the blank hole G k  in the Y-axis direction, MX ko  is a position, in the X-axis direction, of a center axis of a circular area where a worked hole H k  is capable of being formed by working and adjusting the blank hole G k , MY ko  is a position, in the Y-axis direction, of the center axis of the circular area where the worked hole H k  can be formed by working and adjusting the blank hole G k , OX k  is a position of an axis of the worked hole H k  in the X-axis direction, OY k  is a position of the axis of the worked hole H k  in the Y-axis direction, OX is a designed position of the axis of the worked hole H k  in the X-axis direction, OY ks  is a designed position of the axis of the worked hole H k  in the Y-axis direction, OX ms  is a designed position of a center axis of a worked hole H m  in the X-axis direction, OY ms  is a designed position of the center axis of the worked hole H m  in the Y-axis direction, P km  is a designed pitch between the worked holes H k , H m , ΔP km  is a calculated pitch error between the worked holes H k , H m , ΔX km  is an axis-to-axis error between the worked holes H k , H m  in the X-axis direction, ΔY km  is an axis-to-axis error between the worked holes H k , H m  in the Y-axis direction, ΔQ k  is an amount of offset between the center axis of the blank hole G k  and the calculated axis of the worked hole H k , ΔT k  is a length between the center axis of the circular area where the worked hole H k  is capable of being formed and the calculated axis of the worked hole H k , EP km  is a tolerance for the pitch error between the worked holes H K , H m , EX km  is a tolerance for the axis-to-axis error between the worked holes H k , H m  in the X-axis direction, EY km  is a tolerance for the axis-to-axis error between the worked holes H k , H m  in the Y-axis direction, EQ k  is a tolerance for the amount of offset between the center axis of the blank hole G k  and the axis of the worked hole H k , ET k  is a tolerance for the length between the center axis of the circular area where the worked hole H k  is capable of being formed and the axis of the worked hole H k , WP km  is a weight coefficient for ΔP km , WX km  is a weight coefficient for ΔX km , WY km  is a weight coefficient for ΔY km , WQ A  is a weight coefficient for ΔQ k , and WT k  is a weight coefficient for ΔT k . 
         [0009]    Also, the machine tool according to the present invention may be characterized in that, in the machine tool described above, the workpiece is a boom of an excavator. 
         [0010]    Also, the machine tool according to the present invention may be characterized in that, in the machine tools described above, the machine tool is a horizontal boring and milling machine with counter spindles. 
         [0011]    Also, the machine tool according to the present invention may be characterized in that, in the machine tools described above, the measurement means is anyone of an imaging camera and a touch sensor. 
       Advantageous Effects of Invention 
       [0012]    Even in the case of a workpiece with a pitch error greater than or equal to its tolerance between worked holes, the machine tool according to the present invention can work and adjust the worked holes to such optimized positions that all the pitch errors can be less than or equal to their respective tolerances. In this way, defective products can be greatly reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a plan view illustrating a schematic configuration of a main part of a first embodiment in which a machine tool according to the present invention is applied to a horizontal boring and milling machine with counter spindles. 
           [0014]      FIG. 2  is a front view illustrating a schematic configuration of a main part of the horizontal boring and milling machine with counter spindles in  FIG. 1 . 
           [0015]      FIG. 3  is a control block diagram of the main part of the horizontal boring and milling machine with counter spindles in  FIG. 1 . 
           [0016]      FIG. 4  is a schematic structure view of a boom of an excavator. 
           [0017]      FIG. 5  is a flowchart of a main part of actuation of the horizontal boring and milling machine with counter spindles in the first embodiment. 
           [0018]      FIG. 6  is an explanatory view of the center axes of worked holes. 
           [0019]      FIG. 7  is an explanatory view of the position of a worked hole formed in a flange portion. 
           [0020]      FIG. 3  is a control block diagram of a main part of a second embodiment in which the machine tool according to the present invention is applied to a horizontal boring and milling machine with counter spindles. 
           [0021]      FIG. 9  is a flowchart of a main part of actuation of the horizontal boring and milling machine with counter spindles in the second embodiment. 
           [0022]      FIG. 10  is an explanatory view of the center axes of protruding portions. 
           [0023]      FIG. 11  is an explanatory view of round portions of flange portions and their center axes. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Embodiments of a machine tool according to the present invention will be described with reference to the drawings. However, the present invention is not limited only to the following embodiments to be described with reference to the drawings. 
       First Embodiment 
       [0025]    A first embodiment of the machine tool according to the present invention will be described with reference to  FIGS. 1 to 7 . 
         [0026]    As illustrated in  FIGS. 1 and 2 , a table  112  is provided on a bed  111  slidably in an X-axis direction (the top-bottom direction of  FIG. 1 , the direction perpendicular to the plane of the sheet of  FIG. 2 ). Columns  122 ,  132  are provided upright on beds  121 ,  131  which are placed by the opposite sides of the table  112  in its width direction (the left-right direction of  FIGS. 1 and 2 ), respectively. 
         [0027]    On the surfaces of the columns  122 ,  132  on the table  112  side, spindle heads  123 ,  133  are provided movably in an Y-axis direction, which is a vertical direction (the direction perpendicular to the plane of the sheet of  FIG. 1 , the top-bottom direction of  FIG. 2 ), relative to these surfaces of the columns  122 ,  132 , respectively. On the surfaces of the spindle heads  123 ,  133  on the table  112  side, spindles  124 ,  134  are provided, respectively, with their tips facing the table  112  side. The spindles  124 ,  134  are movable toward and away from their respective spindle heads  123 ,  133  in a Z-axis direction, which is their axial direction (the left-right direction of  FIGS. 1 and 2 ). 
         [0028]    Imaging cameras  125 ,  135 , which serve as measurement means, are detachably attached to the spindles  124 ,  134 , respectively. The spindles  124 ,  134  are each capable of holding any one of the imaging camera  125 ,  135  and a tool not illustrated for cutting or the like such as a milling cutter so that the imaging camera  125 ,  135  and the tool can be changed from one another. 
         [0029]    As illustrated in  FIG. 3 , the imaging cameras  125 ,  135  are electrically connected to an input part of an arithmetic control unit  140 , which serves as arithmetic control means. An output part of the arithmetic control unit  140  is electrically connected to a drive motor  113  that moves the table  112  in the X-axis direction, to drive motors  126 ,  136  that move the spindle heads  123 ,  133  in the Y-axis direction, respectively, to drive motors  127 ,  137  that move the spindles  124 ,  134  forward and backward in the Z-axis direction, respectively, and to drive motors  128 ,  138  that rotationally drive the spindles  124 ,  134 , respectively. 
         [0030]    An input unit  141  that inputs various instructions is electrically connected to the input part of the arithmetic control unit  140 . The arithmetic control unit  140  is capable of controlling the actuation of the drive motors  113 ,  126  to  128 ,  136  to  138  based on information from the input unit  141  and information inputted in advance, and of performing arithmetic operation for controlling the actuation of the drive motors  113 ,  126 ,  127 ,  136 ,  137  based on information from the imaging cameras  125 ,  135  and information inputted in advance (details will be described later). 
         [0031]    As illustrated in  FIG. 4 , a boom  10  of an excavator, which is a workpiece, includes a pair of plate members  11 ,  12  disposed in mutually facing postures, and a joint member  13  joining and fixing them to each other. A plurality of (four in this embodiment) blank holes  11 A to  11 D and a plurality (four in this embodiment) of blank holes  12 A to  12 D for pivotally supporting an arm, hydraulic cylinders, and the like are formed in the plate members  11 ,  12  at predetermined positions, respectively. 
         [0032]    The blank holes  11 A,  11 B,  11 D,  12 A,  123 ,  12 D in the boom  10  are formed in (hollow) cylindrical protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d , respectively, which protrude outward of the plate members  11 ,  12  in their thickness direction. The blank holes  11 C,  12 C in the boom  10  are formed in bracket portions  11   c ,  12   c  around their round protruding ends, respectively, the bracket portions  11   c ,  12   c  protruding in flush with the surfaces of the plate members  11 ,  12 . 
         [0033]    Note that, in this embodiment, components such as the columns  122 ,  132 , the spindle heads  123 ,  133 , the drive motors  113 ,  126 ,  127 ,  136 ,  137  constitute relative movement means, and components such as the drive motors  126 ,  138  constitute spindle drive means. 
         [0034]    Next, description will be given of actuation of a machine tool  100  according to this embodiment as described above for working and adjusting the blank holes  11 A to  11 D,  12 A to  12 D in the boom  10  into worked holes  10 A to  10 D by cutting the blank holes  11 A to  11 D,  12 A to  12 D to expand their diameters. 
         [0035]    First, the boom  10  is placed at a prescribed position on the table  112  (S 111  in  FIG. 5 ), and the imaging cameras  125 ,  135  are attached to the spindles  124 ,  134  (S 112  in  FIG. 5 ). 
         [0036]    Then, the input unit  141  inputs information into the arithmetic control unit  140  which instructs imaging of the blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom  10  with the imaging cameras  125 ,  135 . In response, the arithmetic control unit  140  actuates the drive motors  113 ,  126 ,  127 ,  136 ,  137  to move the table  112  in the X-axis direction and move the spindles  124 ,  134  in the Y-axis direction and the Z-axis direction such that the blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom  10  can be imaged with the imaging cameras  125 ,  135  (S 113  in  FIG. 5 ). 
         [0037]    Based on information from the imaging cameras  125 ,  135 , the arithmetic control unit  140  finds the positions of the blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom  10  in the X-axis direction and the Y-axis direction (S 114  in  FIG. 5 ). 
         [0038]    Then, the arithmetic control unit  140  calculates the positions of such center axes  10   ai  to  10   di  in the X-axis direction and the Y-axis direction (see  FIG. 6 ) that the mutually facing blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  can be coaxial with each other with the smallest amounts of movement so that the positions of the mutually facing blank holes  11 A to  11 D,  12 A to  12 D in the X-axis direction and the Y-axis direction can coincide with each other, that is, the offset between their axes can be eliminated (S 115  in  FIG. 5 ). 
         [0039]    Thereafter, the arithmetic control unit  140  calculates the distance (pitch) between each two center axes of interest among the center axes  10   ai  to  10   di , in particular, four pitches in total including the pitch between the center axes  10   ai ,  10   bi , the pitch between the center axes  10   bi ,  10   ci , the pitch between the center axes  10   ci ,  10   di , the pitch between the center axes  10   ai ,  10   di  (S 116  in  FIG. 5 ). The arithmetic control unit  140  then determines whether or not all of these pitches are less than or equal to their respective prescribed values (tolerances) (S 117  in  FIG. 5 ). 
         [0040]    If all of the pitches are less than or equal to their respective prescribed values (tolerances), the imaging cameras  125 ,  135 , which are attached to the spindles  124 ,  134 , are changed to tools for cutting or the like such as milling cutters (S 118  in  FIG. 5 ). 
         [0041]    Then, the arithmetic control unit  140  controls the actuation of the drive motors  113 ,  126 ,  127 ,  136 ,  137  to move the table  112  in the X-axis direction and move the spindles  124 ,  134  in the Y-axis direction and the Z-axis direction and controls the actuation of the drive motors  128 ,  138  to rotationally drive the spindles  124 ,  134  such that the blank holes  11 A to  11 D,  12 A to  12 D are worked and adjusted by cutting cut with the tools into worked holes  10 A to  10 D having their axes on the center axes  10   ai  to  10   di  (S 119  in  FIG. 5 ). 
         [0042]    On the other hand, if even one of the pitches does not satisfy its prescribed value (tolerance), the arithmetic control unit  140  calculates minimized values satisfying Inequalities (1111-1) to (1114-1) (1141-1) to (1144-1) below based on Equations (1101), (1111) to (1114), (1141) to (1144) below, that is, the arithmetic control unit  140  calculates optimized positions of the center axes  10   ai  to  10   di  in the X-axis direction and the Y-axis direction, in other words, optimized positions of the axes of the worked holes  10 A to  10 D (S 121  in  FIG. 5 ). 
         [0000]        F ( OX   a   ,OX   b   ,OX   c   ,OX   d   ,OY   a   ,OY   b   ,OY   c   ,OY   d )=( WP   AB   ×ΔP   AB   2 )+( WP   BC   ×ΔP   BC   2 )+( WP   CD   ×ΔP   CD   2 )+( WP   AD   ×ΔP   AD   2 )+( WQ   A   ×ΔQ   A   2 )+( WQ   B   ×ΔQ   B   2 )+( WQ   C   ×ΔQ   C   2 )+( WQ   D   ×ΔQ   D   2 )  (1101)
 
         [0000]      Δ P   AB ={( OX   b   −OX   a ) 2 +( OY   b   −OY   a ) 2 } 1/2   −P   AB   (1111)
 
         [0000]      Δ P   CD ={( OX   d   −OX   c ) 2 +( OY   d   −OY   c ) 2 } 1/2   −P   CD   (1113)
 
         [0000]      Δ P   AD ={( OX   a   −OX   d ) 2 +( OY   a   −OY   d ) 2 } 1/2   −P   AD   (1114)
 
         [0000]      Δ P   AB   ≦EP   AB   (1111-1)
 
         [0000]      Δ P   BC   ≦EP   BC   (1111-2)
 
         [0000]      Δ P   CD   ≦EP   CD   (1111-3)
 
         [0000]      Δ P   DA   ≦EP   DA   (1111-4)
 
         [0000]      Δ Q   A ={( OX   a   −MX   ai ) 2 +( OY   a   −MY   ai ) 2 } 1/2   (1141)
 
         [0000]      Δ Q   B ={( OX   b   −MX   bi ) 2 +( OY   b   −MY   bi ) 2 } 1/2   (1142)
 
         [0000]      Δ Q   C ={( OX   c   −MX   ci ) 2 +( OY   c   −MY   ci ) 2 } 1/2   (1143)
 
         [0000]      Δ Q   D ={( OX   d   −MX   di ) 2 +( OY   d   −MY   di ) 2 } 1/2   (1144)
 
         [0000]      Δ Q   A   ≦EQ   A   (1141-1)
 
         [0000]      Δ Q   B   ≦EQ   B   (1142-1)
 
         [0000]      Δ Q   C   ≦EQ   C   (1143-1)
 
         [0000]      Δ Q   D   ≦EQ   D   (1144-1)
 
         [0043]    Now, the above values will be described. 
         [0044]    MX ai  is the position of the center axis  10   ai  in the X-axis direction. MY ai  is the position of the center axis  10   ai  in the Y-axis direction. MX bi  is the position of the center axis  10   bi  in the X-axis direction. MY bi  is the position of the center axis  10   bi  in the Y-axis direction. MX ci  is the position of the center axis  10   ci  in the X-axis direction. MY ci  is the position of the center axis  10   ci  in the Y-axis direction. MX di  is the position of the center axis  10   di  in the X-axis direction. MY di  is the position of the center axis  10   di  in the Y-axis direction. These are values calculated by the arithmetic control unit  140  based on the information from the imaging cameras  125 ,  135  such that the positions of the axes of the mutually facing blank holes  11 A to  11 D,  12 A to  12 D can coincide with each other, as described above. 
         [0045]    OX a  is the position of the axis of the worked hole  10 A in the X-axis direction. OY a  is the position of the axis of the worked hole  10 A in the Y-axis direction. OX b  is the position of the axis of the worked hole  103  in the X-axis direction. OY b  is the position of the axis of the worked hole  10 B in the Y-axis direction. OX c  is the position of the axis of the worked hole  100  in the X-axis direction. OY c  is the position of the axis of the worked hole  100  in the Y-axis direction. OX d  is the position of the axis of the worked hole  10 D in the X-axis direction. OY d  is the position of the axis of the worked hole  10 D in the Y-axis direction. These are values calculated by the arithmetic control unit  140  based on Equations (1101), (1111) to (1114), (1141) to (1144) and Inequalities (1111-1) to (1114-1), (1141-1) to (1144-1) above. 
         [0046]    P AB  is the designed axis-to-axis distance (pitch) between the worked hole  10 A and the worked hole  103 . P BC  is the designed axis-to-axis distance (pitch) between the worked hole  10 B and the worked hole  100 . P CD  is the designed axis-to-axis distance (pitch) between the worked hole  100  and the worked hole  10 D. P AD  is the designed axis-to-axis distance (pitch) between the worked hole  10 A and the worked hole  10 D. These are values inputted in advance in the arithmetic control unit  140 . 
         [0047]    ΔP AB  is the difference (pitch error) between the calculated axis-to-axis distance (pitch) between the axes of the worked hole  10 A and the worked hole  10 B and P AB  mentioned above. ΔP BC  is the difference (pitch error) between the calculated axis-to-axis distance (pitch) between the axes of the worked hole  10 B and the worked hole  10 C and P BC  mentioned above. ΔP CD  is the difference (pitch error) between the calculated axis-to-axis distance (pitch) between the axes of the worked hole  10 C and the worked hole  10 DC and P CD  mentioned above. ΔP AD  is the difference (pitch error) between the calculated axis-to-axis distance (pitch) between the axes of the worked hole  10 A and the worked hole  10 D and P AD  mentioned above. These are values calculated by the arithmetic control unit  140 . 
         [0048]    ΔQ A  is the length (amount of offset) between the center axis  10   ai  and the calculated axis of the worked hole  1 - 0 A. ΔQ B  is the length (amount of offset) between the center axis  10   bi  and the calculated axis of the worked hole  10 B. ΔQ C  is the length (amount of offset) between the center axis  10   ci  and the calculated axis of the worked hole  100 . ΔQ D  is the length (amount of offset) between the center axis  10   di  and the calculated axis of the worked hole  10 D. These are values calculated by the arithmetic control unit  140 . 
         [0049]    EP AB  is a tolerance for the pitch error between the worked holes  10 A,  10 B. EP BC  is a tolerance for the pitch error between the worked holes  10 B,  10 C. EP CD  is a tolerance for the pitch error between the worked holes  10 C,  10 D. EP AD  is a tolerance for the pitch error between the worked holes  10 A,  10 D. These are values inputted in advance in the arithmetic control unit  140 . 
         [0050]    EQ A  is a tolerance for the amount of offset between the center axis  10   ai  and the axis of the worked hole  10 A. EQ B  is a tolerance for the amount of offset between the center axis  10   bi  and the axis of the worked hole  10 B. EQ C  is a tolerance for the amount of offset between the center axis  10   ci  and the axis of the worked hole  100 . EQ D  is a tolerance for the amount of offset between the center axis  10   di  and the axis of the worked hole  10 D. These are values inputted in advance in the arithmetic control unit  140 . 
         [0051]    WP AB  is a weight coefficient for ΔP AB  mentioned above. WP BC  is a weight coefficient for ΔP BC  mentioned above. WP CD  is a weight coefficient for ΔP CD  mentioned above. WP AD  is a weight coefficient for ΔP AD  mentioned above. These are values greater than or equal to 0 set as appropriate in accordance with various conditions. 
         [0052]    WQ A  is a weight coefficient for ΔQ A  mentioned above. WQ B  is a weight coefficient for ΔQ B  mentioned above. WQ C  is a weight coefficient for ΔQ C  mentioned above. WQ D  is a weight coefficient for ΔQ D  mentioned above. These are values greater than or equal to 0 set as appropriate in accordance with various conditions. 
         [0053]    Here, assume for example that the tolerances E AB , E BC , E CD , E AD  for the pitch errors are each set at ±5 mm and the tolerances E A , E B , E C , E D  for the amounts of offset are each set at 2.5 mm, and that the pitch errors ΔAB, ΔBC, ΔCD, ΔAD and the amounts of offset ΔA to ΔD which do not satisfy their respective Inequalities (1111-1) to (1114-1), (1141-1) to (1144-1) are obtained as a result of calculating MX ai  to MX di , MY ai  to MY di  mentioned above based on the information from the imaging cameras  124 ,  134  and calculating Equations (1101), (1111) to (1114), (1141) to (1144) mentioned above with the weight coefficients W AB , W BC , W CD , W AD , W A  to W D  each set at “1.” In this case, the above values are calculated by gradually increasing (e.g. by 0.1) the weight coefficients W AB , W BC , W CD , W AD , W A  to W D  for the pitch errors ΔAB, ΔBC, ΔCD, ΔAD and amounts of offset ΔA to ΔD until they satisfy Inequalities (1111-1) to (1114-1), (1141-1) to (1144-1) (see Optimization Example 1 in Tables 1 to 4 below). 
         [0054]    Also, assume for example that the pitch errors ΔAB, ΔBC, ΔCD, ΔAD and the amounts of offset ΔA to ΔD which do not satisfy their respective Inequalities (1111-1) to (1114-1), (1141-1) to (1144-1) are obtained as a result of calculating Equations (1101), (1111) to (1114), (1141) to (1144) mentioned above with the weight coefficients W A  to W D  for the amounts of offset ΔA to ΔD each set at “1” and the weight coefficients W AD , W BC , W CD , W AD  for the pitch errors ΔAB, ΔBC, ΔCD, ΔAD each set at “0” in an attempt to reduce the amounts of offset ΔA to ΔD as much as possible, that is, to leave the removal stocks as much as possible. In this case, the above values are calculated by gradually increasing (e.g. by 0.1) the weight coefficients W A  to W D  for the pitch errors ΔAB, ΔBC, ΔCD, ΔAD until they satisfy Inequalities (1111-1) to (1114-1), (1141-1) to (1144-1) (see Optimization Example 2 in Tables 1 to 4 below). 
         [0055]    Also, for example, as illustrated in  FIG. 7 , if the worked hole  100  is formed in each bracket portion  11   c ,  12   c  on a positive side relative to the blank hole  11 C,  12 C in the X-axis direction and the Y-axis direction (the rightward direction and the upward direction of  FIG. 7 ), strength may possibly decrease. In this case, the above values are calculated such that Inequalities (1143-2), (1143-3) below are also satisfied (see Optimization Example 3 in Tables 1 to 4 below). 
         [0000]        OX   c   ≦MX   ci   (1143-2)
 
         [0000]        OY   c   ≦MY   ci   (1143-3)
 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Calculated 
                 Optimization 
                 Optimization 
                 Optimization 
               
               
                 Position 
                 Value 
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 MX ai   
                 497.762 
                   
                   
                   
               
               
                 MY ai   
                 496.657 
               
               
                 MX bi   
                 2502.737 
               
               
                 MY bi   
                 1502.044 
               
               
                 MX ci   
                 4497.585 
               
               
                 MY ci   
                 2002.928 
               
               
                 MX di   
                 7498.608 
               
               
                 MY di   
                 499.319 
               
               
                 OX a   
                   
                 498.866 
                 498.471 
                 498.562 
               
               
                 OY a   
                   
                 498.004 
                 497.427 
                 497.557 
               
               
                 OX b   
                   
                 2501.446 
                 2502.026 
                 2501.937 
               
               
                 OY b   
                   
                 1500.698 
                 1501.275 
                 1501.244 
               
               
                 OX c   
                   
                 4497.888 
                 4497.732 
                 4497.585 
               
               
                 OY c   
                   
                 2002.026 
                 2002.413 
                 2002.128 
               
               
                 OX d   
                   
                 7498.492 
                 7498.463 
                 7498.508 
               
               
                 OY d   
                   
                 500.221 
                 499.835 
                 500.119 
               
               
                   
               
               
                 Unit: mm 
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Axis-to-Axis 
                 Designed 
                 Calculated 
                 Optimization 
                 Optimization 
                 Optimization 
               
               
                 Distance (Pitch) 
                 Value 
                 Value 
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 P AB   
                 2236.068 
                   
                   
                   
                   
               
               
                 P BC   
                 2061.553 
               
               
                 P CD   
                 3354.102 
               
               
                 P AD   
                 7000.000 
               
               
                 {(MX bi  − MX ai ) 2  + 
                   
                 2242.928 
               
               
                 (MY bi  − MY ai ) 2 } 1/2   
               
               
                 {(MX ci  − MX bi ) 2  + 
                   
                 2056.771 
               
               
                 (MY ci  − MY bi ) 2 } 1/2   
               
               
                 {(MX di  − MX ci ) 2  + 
                   
                 3356.632 
               
               
                 (MY di  − MY ci ) 2 } 1/2   
               
               
                 {(MX ai  − MX di ) 2  + 
                   
                 7000.846 
               
               
                 (MY ai  − MY di ) 2 } 1/2   
               
               
                 {(OX b  − OX a ) 2  + 
                   
                   
                 2239.581 
                 2240.808 
                 2240.736 
               
               
                 (OY b  − OY a ) 2 } 1/2   
               
               
                 {(OX c  − OX b ) 2  + 
                   
                   
                 2058.424 
                 2057.609 
                 2057.547 
               
               
                 (OY c  − OY b ) 2 } 1/2   
               
               
                 {(OX d  − OX c ) 2  + 
                   
                   
                 3355.450 
                 3356.081 
                 3355.826 
               
               
                 (OY d  − OY c ) 2 } 1/2   
               
               
                 {(OX a  − OX d ) 2  + 
                   
                   
                 6999.627 
                 6999.946 
                 6999.946 
               
               
                 (OY a  − OY d ) 2 } 1/2   
               
               
                   
               
               
                 Unit: mm 
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Axis-to-Axis 
                   
                   
                   
                   
                   
               
               
                 Distance 
                   
                 Calculated 
                 Optimization 
                 Optimization 
                 Optimization 
               
               
                 (Pitch) Error 
                 Tolerance 
                 Value 
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 EP AB   
                 ±5 
                   
                   
                   
                   
               
               
                 EP BC   
                 ±5 
               
               
                 EP CD   
                 ±5 
               
               
                 EP AD   
                 ±5 
               
               
                 {(MX bi  − MX ai ) 2  + 
                   
                 6.860 
               
               
                 (MY bi  − MY ai ) 2 } 1/2  − 
               
               
                 AB 
               
               
                 {(MX ci  − MX bi ) 2  + 
                   
                 −4.782 
               
               
                 (MY ci  − MY bi ) 2 } 1/2  − 
               
               
                 BC 
               
               
                 {(MX di  − MX ci ) 2  + 
                   
                 2.530 
               
               
                 (MY di  − MY ci ) 2 } 1/2  − 
               
               
                 CD 
               
               
                 {(MX ai  − MX di ) 2  + 
                   
                 0.846 
               
               
                 (MY ai  − MY di ) 2 } 1/2  − 
               
               
                 AD 
               
               
                 ΔP AB   
                   
                   
                 3.513 
                 4.740 
                 4.668 
               
               
                 ΔP BC   
                   
                   
                 −3.129 
                 −3.944 
                 −4.006 
               
               
                 ΔP CD   
                   
                   
                 1.348 
                 1.979 
                 1.724 
               
               
                 ΔP AD   
                   
                   
                 −0.373 
                 −0.054 
                 −0.054 
               
               
                   
               
               
                 Unit: mm 
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Tol- 
                 Optimization 
                 Optimization 
                 Optimization 
               
               
                 Amount of Offset 
                 erance 
                 Example 1 
                 Example 2 
                 Example 3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 EQ A   
                 X-Axis 
                 2.500 
                   
                   
                   
               
               
                   
                 Direction 
               
               
                   
                 Y-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                 EQ B   
                 X-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                   
                 Y-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                 EQ C   
                 X-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                   
                 Y-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                 EQ D   
                 X-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                   
                 Y-Axis 
                 2.500 
               
               
                   
                 Direction 
               
               
                 ΔQ A   
                 OX a  − MX ai   
                   
                 1.104 
                 0.709 
                 0.800 
               
               
                   
                 OY a  − MY ai   
                   
                 1.347 
                 0.770 
                 0.900 
               
               
                 ΔQ B   
                 OX b  − MX bi   
                   
                 −1.290 
                 −0.711 
                 −0.800 
               
               
                   
                 OY b  − MY bi   
                   
                 −1.347 
                 −0.770 
                 −0.800 
               
               
                 ΔQ C   
                 OX c  − MX ci   
                   
                 0.302 
                 0.146 
                 0.000 
               
               
                   
                 OY c  − MY ci   
                   
                 −0.902 
                 −0.516 
                 −0.800 
               
               
                 ΔQ D   
                 OX d  − MX di   
                   
                 −0.116 
                 −0.145 
                 −0.100 
               
               
                   
                 OY d  − MY di   
                   
                 0.902 
                 0.516 
                 0.800 
               
               
                   
               
               
                 Unit: mm 
               
             
          
         
       
     
         [0056]    As can be seen from Tables 1 to 4, even when the pitch error between the worked holes  10 A,  10 B (6.860 mm) exceeds its tolerance (±5 mm), the amount of offset can be reduced to or below the tolerance (2.5 mm) and the pitch error can also be reduced to or below the tolerance (i.e. to 3.513 mm), as illustrated in Optimization Example 1 above. 
         [0057]    Further, as illustrated in Optimization Example 2 above, the pitch error (6.860 mm) between the worked holes  10 A,  10 B can of course be reduced to or below the tolerance (i.e. to 4.740 mm), and the amount of offset can also be reduced to a greater extent than in Optimization Example 1. 
         [0058]    Furthermore, as illustrated in Optimization Example 3 above, the pitch error between the worked holes  10 A,  10 B (6.860 mm) can be reduced to or below the tolerance (i.e. to 4.668 mm) without positioning the worked hole  10 C on the positive side relative to each blank hole  11 C,  12 C in the X-axis direction and the Y-axis direction (the rightward direction and the upward direction of  FIG. 7 ), that is, without making OX c −MX ci , and OY c −MY ci  positive values. Thus, the decrease in strength of the worked hole  10 C can be reduced. 
         [0059]    After the arithmetic control unit  140  calculates the optimized positions of the worked holes  10 A to  10 D as described above, the imaging cameras  125 ,  135 , which are attached to the spindles  124 ,  134 , are changed to tools for cutting or the like such as milling cutters (S 122  in  FIG. 5 ). 
         [0060]    Then, based on the above calculated results, the arithmetic control unit  140  actuates the drive motors  113 ,  126 ,  127 ,  128 ,  136 ,  137 ,  138  to cut the blank holes  11 A to  112 ,  12 A to  12 D with the tools to expand their diameters, sc that the blank holes  11 A to  11 D,  12 A to  12 D are worked and adjusted into the worked holes  10 A to  10 D in the boom  10  (S 123  in  FIG. 5 ). 
         [0061]    The boom  10  with the blank holes  11 A to  11 D,  12 A to  12 D worked and adjusted into the worked holes  10 A to  10 D as described above has all the pitch errors less than or equal to their respective tolerances. Hence, components such as hydraulic cylinders can be joined between the worked holes  10 A to  10 D without problems at all. 
         [0062]    Thus, with the machine tool  100  according to this embodiment, even when the boom  10  has a pitch error greater than or equal to its tolerance, the worked holes  10 A to  10 D can be worked and adjusted to such optimized positions that all the pitch errors are less than or equal to their respective tolerances. In this way, defective products can be greatly reduced. 
       Second Embodiment 
       [0063]    A second embodiment of the machine tool according to the present invention will be described with reference to  FIGS. 8 to 11 . Note that, for the same portions as those in the foregoing embodiment, the same reference signs as the reference signs used in the description of the foregoing embodiment will be used, and therefore description overlapping the description in the foregoing embodiment will be omitted. 
         [0064]    As illustrated in  FIG. 8 , the imaging cameras  125 ,  135  and the input unit  141  are electrically connected to an input part of an arithmetic control unit  240 , which serves as arithmetic control means. An output part of the arithmetic control unit  240  is electrically connected to the drive motors  113 ,  126  to  128 ,  136  to  138 . 
         [0065]    The arithmetic control unit  24 C is capable of controlling the actuation of the drive motors  113 ,  126  to  128 ,  136  to  138  based on information from the input unit  141  and information inputted in advance, and of performing arithmetic operation for controlling the actuation of the drive motors  113 ,  126 ,  127 ,  136 ,  137  based on information from the imaging cameras  125 ,  135  and information inputted in advance (details will be described later). 
         [0066]    Next, description will be given of actuation of a machine tool according to this embodiment including the above arithmetic control unit  240 . 
         [0067]    As in the foregoing embodiment, after performing Steps S 111 , S 112  described above, the input unit  141  inputs information into the arithmetic control unit  240  which instructs imaging of the protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  and the bracket portions  11   c ,  12   c  of the plate members  11 ,  12  of the boom  10  as well as the blank holes  11 A to  11 C,  12 A to  12 D with the imaging cameras  125 ,  135 . In response, the arithmetic control unit  240  actuates the drive motors  113 ,  126 ,  127 ,  136 ,  137  to move the table  112  in the X-axis direction and move the spindles  124 ,  134  in the Y-axis direction and the Z-axis direction such that the protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  and the bracket portions  11   c ,  12   c  of the plate members  11 ,  12  of the boom  10  as well as the blank holes  11 A to  11 D,  12 A to  12 D can be imaged with the imaging cameras  125 ,  135  (S 213  in  FIG. 9 ). 
         [0068]    Based on information from the imaging cameras  125 ,  135 , the arithmetic control unit  240  finds the positions of the blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom  10  in the X-axis direction and the Y-axis direction and the positions of the protruding portions  11   a ,  11   b ,  11   c ,  12   a ,  12   b ,  12   c  in the X-axis direction and the Y-axis direction. The arithmetic control unit  240  further finds the positions of the axes of round portions  11   ca ,  12   ca  of the protruding ends of the bracket portions  11   c ,  12   c  in the X-axis direction and the Y-axis direction (S 214  in  FIG. 9 ). 
         [0069]    Then, the arithmetic control unit  240  calculates the positions of the center axes  10   ai  to  10   di  in the X-axis direction and the Y-axis direction as in the foregoing embodiment. In addition, the arithmetic control unit  240  calculates the positions, in the X-axis direction and the Y-axis direction, of such center axes that the mutually facing protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  of the plate members  11 ,  12  can be coaxial with each other with the smallest amounts of movement, specifically, the positions, in the X-axis direction and the Y-axis direction, of center axes  10   ao ,  10   bo ,  10   do  of circular areas where the worked holes  10 A,  10 B,  10 D can be formed (see  FIG. 10 ). The arithmetic control unit  240  further calculates the positions, in the X-axis direction and the Y-axis direction, of such a center axis that the round portions  11   ca ,  12   ca  of the protruding ends of the mutually facing bracket portions  11   c ,  12   c  can be coaxial with each other with the smallest amounts of movement, specifically, the positions, in the X-axis direction and the Y-axis direction, of a center axis  10   co  of a circular area where the worked hole  10 C can be formed (see  FIG. 11 ) (S 215  in  FIG. 9 ). 
         [0070]    Thereafter, as in the foregoing embodiment, the arithmetic control unit  240  calculates the pitch between each two center axes of interest among the center axes  10   ai  to  10   di  (S 116  in  FIG. 9 ). The arithmetic control unit  240  then determines whether or not all of these pitches are less than or equal to their respective prescribed values (tolerances) (S 117  in  FIG. 9 ). 
         [0071]    If all of the pitches are less than or equal to their respective prescribed values (tolerances), Steps S 118 , S 119  described above are performed as in the foregoing embodiment. 
         [0072]    On the other hand, if even one of the pitches does not satisfy its prescribed value (tolerance), the arithmetic control unit  240  calculates minimized values satisfying Inequalities (1111-1) to (1114-1), (1141-1) to (1144-1) above and Inequalities (2151-1) to (2154-1) below based on Equation (2101) below, Equations (1111) to (1114), (1141) to (1144) above as well as Equations (2151) to (2154) below, that is, the arithmetic control unit  240  calculates optimized positions of the center axes  10   ai  to  10   di  in the X-axis direction and the Y-axis direction, in other words, optimized positions of the axes of the worked holes  10 A to  10 D (S 221  in  FIG. 9 ). 
         [0000]        F ( OX   a   ,OX   b   ,OX   c   ,OX   d   ,OY   a   ,OY   b   ,OY   c   ,OY   d )=( WP   AB   ×ΔP   AB   2 )+( WP   BC   ×ΔP   BC   2 )+( WP   CD   ×ΔP   CD   2 )+( WP   AD   ×ΔP   AD   2 )+( WQ   A   ×ΔQ   A   2 )+( WQ   B   ×ΔQ   B   2 )+( WQ   C   ×ΔQ   C   2 )+( WQ   D   ×ΔQ   D   2 )+( WT   A   ×ΔT   A   2 )+( WT   B   ×ΔT   B   2 )+( WT   C   ×ΔT   C   2 )+( WT   D   ×ΔT   D   2 )  (2101)
 
         [0000]      Δ T   A ={( OX   a   −MX   ao ) 2 +( OY   a   −MY   ao ) 2 } 1/2   (2151)
 
         [0000]      Δ T   B ={( OX   b   −MX   bo ) 2 +( OY   b   −MY   bo ) 2 } 1/2   (2152)
 
         [0000]      Δ T   C ={( OX   c   −MX   co ) 2 +( OY   c   −MY   co ) 2 } 1/2   (2153)
 
         [0000]      Δ T   D ={( OX   d   −MX   do ) 2 +( OY   d   −MY   do ) 2 } 1/2   (2154)
 
         [0000]      Δ T   A   ≦E   TA   (2151-1)
 
         [0000]      Δ T   B   ≦E   TB   (2151-2)
 
         [0000]      Δ T   C   ≦E   TC   (2151-3)
 
         [0000]      Δ T   D   ≦E   TD   (2151-4)
 
         [0073]    MX ao  is the position of the center axis  10   ao  in the X-axis direction. MY ao  is the position of the center axis  10   ao  in the Y-axis direction. MX bo  is the position of the center axis  10   bo  in the X-axis direction. MY bo  is the position of the center axis  10   bo  in the Y-axis direction. MX co  is the position of the center axis  10   co  in the X-axis direction. MY co  is the position of the center axis  10   co  in the Y-axis direction. MX do  is the position of the center axis  10   do  in the X-axis direction. MY do  is the position of the center axis  10   do  in the Y-axis direction. These are values calculated by the arithmetic control unit  240  based on the information from the imaging cameras  124 ,  134  such that the positions of the axes of the mutually facing protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  can coincide with each other and the positions of the axes of the round portions of the protruding ends of the bracket portions  11   c ,  12   c  can coincide with each other, as described above. 
         [0074]    ΔT A  is the length (amount of eccentricity) between the center axis  10   ao  and the calculated axis of the worked hole  10 A. ΔT B  is the length (amount of eccentricity) between the center axis  10   bo  and the calculated axis of the worked hole  10 B. ΔT C  is the length (amount of eccentricity) between the center axis co and the calculated axis of the worked hole  10 C. ΔT D  is the length (amount of eccentricity) between the center axis do and the calculated axis of the worked hole  10 D. These are values calculated by the arithmetic control unit  240 . 
         [0075]    ET A  is a tolerance for the amount of eccentricity between the center axis  10   ao  and the axis of the worked hole  10 A. ET B  is a tolerance for the amount of eccentricity between the center axis  10   bi  and the axis of the worked hole  10 B. ET C  is a tolerance for the amount of eccentricity between the center axis  10   ci  and the axis of the worked hole  10 C. ET D  is a tolerance for the amount of eccentricity between the center axis  10   di  and the axis of the worked hole  10 D. These are values inputted in advance in the arithmetic control unit  240 . 
         [0076]    WT A  is a weight coefficient for ΔT A  mentioned above. WT B  is a weight coefficient for ΔT B  mentioned above. WT C  is a weight coefficient for ΔT C  mentioned above. WT D  is a weight coefficient for ΔT D  mentioned above. These are values greater than or equal to 0 set as appropriate in accordance with various conditions. 
         [0077]    In sum, this embodiment takes into consideration not only the amounts of offset of the worked holes  10 A to  10 D relative to the blank holes  11 A to  11 D,  12 A to  12 D but also the amounts of eccentricity relative to the protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  and the round portions of the bracket portions  11   c ,  12   c.    
         [0078]    After this arithmetic control unit  240  calculates the optimized positions of the worked holes  10 A to  10 D as in the foregoing embodiment, Steps S 122 , S 123  described above are performed. As a result, the blank holes  11 A to  11 D,  12 A to  12 D can be worked and adjusted into the worked holes  10 A to  10 D in the boom  10 . 
         [0079]    Thus, for the worked holes  10 A,  10 B,  10 D, the amounts of unevenness in the thicknesses of the protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  in the radial direction can be optimized. For the worked hole  100 , the stock allowances for the protruding ends of the bracket portions  11   c ,  12   c  can be optimized. 
         [0080]    Hence, with this embodiment, it is possible to achieve similar advantageous effects to those by the foregoing embodiment and, in addition, more effectively reduce the decrease in strength of the protruding portions  11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  and the bracket portions  11   c ,  12   c  due to the formation of the worked holes  10 A to  10 D. 
       Other Embodiments 
       [0081]    In the foregoing embodiments, the imaging cameras  125 ,  135  are used to input the information on the blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom  10 , the information on the protruding portions  11   a ,  11   b ,  11   c ,  12   a ,  12   b ,  12   c , the information on the bracket portions  11   c ,  12   c , and other relevant information into the arithmetic control units  140 ,  240 . Note however that, as another embodiment, it is possible to use, for example, touch probes or the like in place of the imaging cameras  125 ,  135  to input the information on the blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom.  10 , the information on the protruding portions  11   a ,  11   b ,  11   c ,  12   a ,  12   b ,  12   c , the information on the bracket portions  11   c ,  12   c , and other relevant information into the arithmetic control units  140 ,  240 . 
         [0082]    Also, the foregoing embodiments have described the cases where the present invention is applied to a table moving-type horizontal boring and milling machine with counter spindles. However, as another embodiment, it is possible to apply the present invention to, for example, a column moving-type horizontal boring and milling machine with counter spindles. In this case, too, similar advantageous effects to those by the foregoing embodiments can be achieved. 
         [0083]    Also, the foregoing embodiments have described the cases where the mutually facing blank holes  11 A to  11 D,  12 A to  12 D in the plate members  11 ,  12  of the boom  10  of the excavator are worked and adjusted into the worked holes  10 A to  10 D by cutting the blank holes  11 A to  11 D,  12 A to  12 D to expand their diameters. However, the present invention is not limited to these cases and is applicable just as the foregoing embodiments to cases where n blank holes (n is an integer greater than or equal to 3) formed in a workpiece are to be worked and adjusted into worked holes by cutting the blank holes to expand their diameters. 
         [0084]    In the case of such a workpiece, the arithmetic control means calculates optimized positions of the worked holes from minimized values satisfying Inequalities (110-1), (120-1), (130-1), (140-1), (150-1) below based on Equations (100), (110), (120), (130), (140), (150) below. 
         [0000]    
       
         
           
             
               
                 
                   
                       
                   
                    
                   
                     [ 
                     
                       Formula 
                        
                       
                           
                       
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                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   150 
                   ) 
                 
               
             
             
               
                 
                   
                       
                   
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                         T 
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                       k 
                     
                   
                 
               
               
                 
                   ( 
                   
                     150 
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         [0085]    In the above equations and inequalities, MX ki  is the position of the center axis of a blank hole G k  in the X-axis direction; MY ki  is the position of the center axis of the blank hole G k  in the Y-axis direction; MX ko  is the position, in the X-axis direction, of the center axis of a circular area where a worked hole H k  is capable of being formed by working and adjusting the blank hole G k ; MY ko  is the position, in the Y-axis direction, of the center axis of the circular area where the worked hole H k  is capable of being formed by working and adjusting the blank hole G k ; OX k  is the position of the axis of the worked hole H k  in the X-axis direction; OY k  is the position of the axis of the worked hole H k  in the Y-axis direction; OX ks  is the designed position of the axis of the worked hole H k  in the X-axis direction; OY ks  is the designed position of the axis of the worked hole H k  in the Y-axis direction; OX ms  is the designed position of the center axis of a worked hole H m  in the X-axis direction; OY ms  is the designed position of the center axis of the worked hole H m  in the Y-axis direction; P km  is the designed pitch between the worked holes H k , H m ; ΔP km  is the calculated pitch error between the worked holes H k , H m ; ΔX km  is the axis-to-axis error between the worked holes H k , H m  in the X-axis direction; ΔY km  is the axis-to-axis error between the worked holes H k , H m  in the Y-axis direction; ΔQ k  is the amount of offset between the center axis of the blank hole G k  and the calculated axis of the worked hole H k ; ΔT k  is the length between the center axis of the circular area where the worked hole H k  is capable of being formed and the calculated axis of the worked hole H k ; EP km  is a tolerance for the pitch error between the worked holes H K , H m ; EX km  is a tolerance for the axis-to-axis error between the worked holes H k , H m  in the X-axis direction; EY km  is a tolerance for the axis-to-axis error between the worked holes H k , H m  in the Y-axis direction; EQ k  is a tolerance for the amount of offset between the center axis of the blank hole G k  and the axis of the worked hole H k ; ET k  is a tolerance for the length between the center axis of the circular area where the worked hole H k  is capable of being formed and the axis of the worked hole H k ; WP km  is a weight coefficient for ΔP km ; WX km  is a weight coefficient for ΔX km ; WY km  is a weight coefficient for ΔY km ; WQ A  is a weight coefficient for ΔQ k ; and WT k  is a weight coefficient for ΔT k . 
         [0086]    Here, ΔP km  mentioned above is the error in the axis-to-axis distance between the worked holes H k , H m . On the other hand, ΔX km , ΔY km  mentioned above are the axis-to-axis errors between the worked holes H k , H m  in the X- and Y-axis directions, and are values employed in a case where the error between the axes of the worked holes H k , H m  in the X-axis direction and the error between the axes of the worked holes H k , H m  in the Y-axis direction are considered individually or only one of these errors in the X-axis direction and the Y-axis direction should be considered. 
         [0087]    In short, the foregoing first and second embodiments are cases where n is set at “4,” the amount of offset between the worked holes  10 A,  100  and the amount of offset between the worked holes  10 B,  10 D are omitted, WX km , WY km  are set at “0,” and, in the foregoing first embodiment, WT k  is set at “0.” 
         [0088]    As described above, the present invention can handle various cases by optionally selecting, when necessary, those worked holes between which the pitch error is desired to be less than or equal to the tolerance, and optionally selecting various conditions (setting weight coefficients for unnecessary conditions at “0”) in accordance with the state of the workpiece. 
       INDUSTRIAL APPLICABILITY 
       [0089]    Even in the case of a workpiece with a pitch error greater than or equal to its tolerance between worked holes, the machine tool according to the present invention can work and adjust the worked holes to such optimized positions that all the pitch errors can be less than or equal to their respective tolerances. In this way, defective products can be greatly reduced. The machine tool according to the present invention can therefore be utilized significantly beneficially in various working industries. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  boom 
           10   ai  to  10   di ,  10   ao  to  10   do  center axis 
           10 A to  10 D worked hole 
           11 ,  12  plate member 
           11   a ,  11   b ,  11   d ,  12   a ,  12   b ,  12   d  protruding portion 
           11   c ,  12   c  bracket portion 
           11   ca ,  12   ca  round portion 
           11 A to  11 D,  12 A to  12 D blank hole 
           13  joint member 
           100  machine tool 
           111  bed 
           112  table 
           113  drive motor (for X-axis movement) 
           121 ,  131  bed 
           122 ,  132  column 
           123 ,  133  spindle head 
           124 ,  134  spindle 
           125 ,  135  imaging camera 
           126 ,  136  drive motor (for Y-axis movement) 
           127 ,  137  drive motor (for Z-axis movement) 
           128 ,  138  drive motor (for cutting) 
           140 ,  240  arithmetic control unit 
           141  input unit