Lathe

0001The present invention relates to a lathe.

0002A lathe that machines a work in combined manners is called combined-machining lathe. A combined-machines lathe is disclosed in, for example, German Patent Application Laid-Open Publication <patcit id="pcit0001" dnum="DE10213778A1"><text>DE 10213778A1</text></patcit>, Unexamined Japanese Patent Application KOKAI Publication No.<patcit id="pcit0002" dnum="JPHI1138374B"><text>HI 1-138374</text></patcit>, and Unexamined Japanese Patent Application KOKA1 Publication No.<patcit id="pcit0003" dnum="JP2003117701A"><text>2003-117701</text></patcit>. German Patent Application Laid-Open Publication <patcit id="pcit0004" dnum="DE10213778A1"><text>DE 10213778A1</text></patcit> discloses a lathe which has main spindles facing each other, and a turret performing machining with a tool selected from a plurity of tools in <figref idref="f0016 f0017 f0018">FIGS. 16 to 18</figref>. According, to the lathe disclosed in said German Patent Application Laid-Open Publication, however, because machininq is performed with a tool mounted on the turret, an adjoining tool may interfere with the work. In the case of machining a long work, there is a problem resulting in that machining with a high precision is difficult because the work bends.

0003The lathe disclosed in Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0005" dnum="JPH11138374B"><text>H11-138374 </text></patcit>is a combined-machining lathe whose main spindle is fixed. This combined-machining lathe has a main spindle for gripping a work, a tailstock, a reciprocating carriage, and a tool spindle. The tailstock is arranged at a position opposite to the main spindle. The reciprocating carriage is a carriage that reciprocates in parallel with the centerline of the main spindle or of the tailstock. The tool spindle is fixed on the reciprocating carriage. The tool spindle grips a tool. The tool spindle can change the direction of the tool. A work that is gripped by the main spindle or the tailstock is machined by the tool.

0004When a lengthy work is machined by a combined-machining lathe having such a configuration as described above, the work extends from the main spindle with its one end gripped by the main spindle. Due to this, the work is pushed by the tool and bent. Precise machining cannot be applied if the work remains bent. Therefore, for machining a lengthy work; it is necessary to attach to the tailstock, a center that would abut on the end surface of the work to support the work in cooperation with the main spindle.

0005However, the following problems arise when a center is attached to the tailstock. <ol id="ol0001" compact="compact" ol-style=""><li>(1) Since the center is applied to the end surface of the work, the end surface (front surface) of the work cannot be machined.</li><li>(2) Since the center is attached to the tailstock, a chuck for gripping the work cannot be attached to the tailstock. Therefore, it is impossible to machine the back end surface (back surface) of the work with the work gripped by a chuck at the tailstock.</li><li>(3) Since there is a fear of the tool and the tailstock interfering with each other (colliding on each other), a portion of the work that is held close to the tailstock cannot be machined.</li></ol>

0006As described, with a lathe whose main spindle is fixed, it has been difficult to machine a lengthy work in combined manners.

0007Further, with the combined-machining lathe disclosed in the Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0006" dnum="JPH11138374B"><text>H11-138374</text></patcit>, length of work that can be machined is restricted depending on the distance between the main spindle and the tailstock. Therefore, a work having a length equal to or larger than the distance between the main spindle and the tailstock cannot be machined.

0008On the other hand, a method of machining a lengthy work without using a tailstock is disclosed in the Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0007" dnum="JP2003117701A"><text>2003-117701</text></patcit>. Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0008" dnum="JP2003117701A"><text>2003-117701</text></patcit> represents the basis for the preamble of claim 1 and discloses a technique for providing a guide bush for preventing bending of the work adjacently to the tool, and machining the lengthy work by moving the main spindle.

0009The lathe disclosed in Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0009" dnum="JP2003117701A"><text>2003-117701</text></patcit> has a first headstock for rotatably gripping a work, a second headstock and front tool rest which are arranged on a back headstock, a guide bush, a tool rest to which a bit for cutting a work is attached, a third headstock, a tool attached to the third headstock for machining the back surface of a work, and a rotatable tool carriage which is movable perpendicularly to the axial direction of a work.

0010The back headstock has a function for moving in the direction of axis of a work which is gripped by the first headstock, and a function for moving perpendicularly to this axial direction. The guide bush supports the work which is rotating. The second headstock grips the end surface (front surface) of the work. A drill for machining the front surface of the work is attached to the tool rest. The third headstock is arranged at a side of the guide bush.

0011According to the lathe disclosed in Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0010" dnum="JP2003117701A"><text>2003-117701</text></patcit>, the front end (front surface) of a work is machined by a tool attached to the front tool rest while the work is gripped by the first headstock and further supported by the guide bush. After this, the back headstock is moved, so that the front end surface of the work is gripped by the second headstock and then the work gripped by the second headstock is gripped by the third headstock. Sequentially, the front end of the work gripped by the third headstock is machined by the tool attached to the tool rest.

0012In a case where the back end (back surface) of the work is machined by this lathe, the back headstock is moved, so that the back end (back surface) of the work gripped by the second headstock is machined by a drill attached to the third headstock.

0013The lathe disclosed in Unexamined Japanese Patent Application KOKAI Publication No. <patcit id="pcit0011" dnum="JP2003117701A"><text>2003-117701</text></patcit> can machine the front end and back end of a lengthy work, but has the following problems. <ol id="ol0002" compact="compact" ol-style=""><li>(1) In order to form an angled hole in the work, it is necessary to attach an angled hole forming attachment to the tool rest.</li><li>(2) It is necessary to separately prepare a tool for machining the front end surface of the work and a tool for machining the back end surface thereof.</li><li>(3) When positioning a tool on the tool rest, it is necessary to consider a fear that the tool might interfere with (collide on) an adjacent tool.</li><li>(4) It is necessary to secure in the lathe, a place where the tool for machining the back end surface of the work is attached, in addition to a place where the tool for machining the front end surface of the work is attached. This makes it difficult to downsize the lathe and also deteriorates the working efficiency.</li><li>(5) The number of tools that can be attached to the tool rest and the third headstock is limited. This limits the kinds of works that can be machined in a complex manner without changing tools.</li><li>(6) It is necessary to stop the lathe when changing tools, making the working efficiency worse.</li></ol>

0014The present invention was made in view of the above-described circumstances, and an object of the present invention is to provide a lathe that can efficiently machine works of varied lengths from short length to long length.

0015Another object of the present invention is to provide a lathe that can machine a work without excluding both end surfaces thereof, into a complex shape.

0016Still another object of the present invention is to provide a lathe that can machine works varied in length, entirely without excluding both end surfaces thereof, into complex shapes.

0017To achieve the above objects, a lathe according to claim 1 is provided. The lathe may comprise a tool rest (60) which has one or a plurality of tools mounted thereon, and works independently from the tool holding member to machine the work gripped by the main spindle (30) or by the back spindle (50) by using the mounted tool. It is preferred that the tool rest (60) be movable in the X direction, the Z direction, and the Y direction.

0018The lathe may comprise a controller (201) which controls positions of the main spindle (30) and back spindle (50) and work gripping and work rotation by the spindles (30, 50), and controls a position and direction of the tool holding member (40, 100).

0019The main spindle (30) and the back spindle (50) can independently grip works respectively, and can grip one work in cooperation with each other.

0020These objects and other objects and advantages of the present invention will become more apparent upon reading of the following detailed description and the accompanying drawings in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a front elevation of an exemplary lathe which is not part of the present invention;</li><li><figref idref="f0002">FIG. 2</figref> is a plan view of the lathe;</li><li><figref idref="f0003">FIG. 3</figref> is a diagram showing an example of configuration of a turret and a tool rest shown in <figref idref="f0001">FIG. 1</figref>;</li><li><figref idref="f0004">FIG. 4</figref> is a diagram showing an example of modification of the tool rest;</li><li><figref idref="f0005">FIG. 5</figref> is an explanatory diagram of a machining example 1;</li><li><figref idref="f0006">FIG. 6</figref> is an explanatory diagram of a machining example 2;</li><li><figref idref="f0007">FIG. 7</figref> is an explanatory diagram of a machining example 3;</li><li><figref idref="f0008">FIG. 8</figref> is an explanatory diagram of a machining example 4;</li><li><figref idref="f0009">FIG. 9</figref> is an explanatory diagram of a machining example 5;</li><li><figref idref="f0010">FIG. 10</figref> is an explanatory diagram of a machining example 6;</li><li><figref idref="f0011">FIGS. 11</figref> are explanatory diagrams of a machining example 7;</li><li><figref idref="f0012">FIGS. 12</figref> are explanatory diagrams of a machining example 8;</li><li><figref idref="f0013">FIG. 13</figref> is an explanatory diagram of a machining example 9;</li><li><figref idref="f0014">FIG. 14</figref> is an explanatory diagram of a machining example 10;</li><li><figref idref="f0015">FIG. 15</figref> is an explanatory diagram of a machining example 11;</li><li><figref idref="f0016">FIG. 16</figref> is an explanatory diagram of a machining example 12;</li><li><figref idref="f0017">FIG. 17</figref> is an explanatory diagram of a machining example 13;</li><li><figref idref="f0018">FIG. 18</figref> is an explanatory diagram of a machining example 14;</li><li><figref idref="f0019">FIG. 19</figref> is a front elevation of a lathe according to an embodiment of the present invention;</li><li><figref idref="f0020">FIG. 20</figref> is a plan view of the lathe;</li><li><figref idref="f0021">FIG. 21</figref> is a diagram showing an example of configuration of a tool spindle and a tool rest shown in <figref idref="f0019">FIG. 19</figref>;</li><li><figref idref="f0022">FIG. 22</figref> is a diagram showing an example of modification of the tool rest;</li><li><figref idref="f0023">FIG. 23</figref> is an explanatory diagram of a machining example 15;</li><li><figref idref="f0024">FIG. 24</figref> is an explanatory diagram of a machining example 16;</li><li><figref idref="f0025">FIG. 25</figref> is an explanatory diagram of a machining example 17;</li><li><figref idref="f0026">FIG. 26</figref> is an explanatory diagram of a machining example 18;</li><li><figref idref="f0027">FIG. 27</figref> is an explanatory diagram of a machining example 19;</li><li><figref idref="f0028">FIG. 28</figref> is an explanatory diagram of a machining example 20;</li><li><figref idref="f0029">FIGS. 29</figref> are explanatory diagrams of a machining example 21;</li><li><figref idref="f0030">FIGS. 30</figref> are explanatory diagrams of a machining example 22;</li><li><figref idref="f0031">FIG. 31</figref> is an explanatory diagram of a machining example 23;</li><li><figref idref="f0032">FIG. 32</figref> is an explanatory diagram of a machining example 24;</li><li><figref idref="f0033">FIG. 33</figref> is an explanatory diagram of a machining example 25;</li><li><figref idref="f0034">FIG. 34</figref> is an explanatory diagram of a machining example 26;</li><li><figref idref="f0035">FIG. 35</figref> is an explanatory diagram of a machining example 27; and</li><li><figref idref="f0036">FIG. 36</figref> is an explanatory diagram of a machining example 28.</li></ul>

0021A lathe according to <figref idref="f0001 f0002">Fig. 1 and 2</figref> is a machine that can apply complex machining to a work W. As shown in <figref idref="f0001">FIG. 1</figref> and <figref idref="f0002">FIG. 2</figref>, the lathe comprise a bed 10, a main spindle 30 for gripping the work W, a turret 40, and a back spindle 50 for gripping the work W. In addition, the lathe comprises a controller 201 thereinside. The controller 201 controls the lathe on the whole.

0022The main spindle 30 has, for example, a chuck and grips the work W such that the centerline of the work W is oriented in a Z1-axis direction, which is one of the horizontal directions. The main spindle 30 is rotatably supported by a headstock 30A. The headstock 30A is mounted on two rails 11 and 12, and designed so as to move in the Z1-axis direction by driving a Z1-axis motor 13. The two rails 11 and 12 are laid on the bed 10 in parallel with the Z1-axis direction. The headstock 30A has a built-in work rotation motor 31. The work rotation motor 31 rotates the work gripped by the main spindle 30. The main spindle 30 has a hole 30H through which work W penetrates, so that the work can be gripped by said main spindle 30 and can extend by penetrating through said hole 30H.

0023The turret 40 is rotatable about a rotation axis 40K. The turret 40 has a plurality of tools 41 attached thereto along its circumferential direction. The turret 40 rotates and thereby moves a selected tool 41 to a machining position where the work W is to be machined. According to the present example, a position where the centerline of a selected tool 41 becomes horizontal is the predetermined position. The turret 40 has its position changed by a turret position setting mechanism to be explained later. The turret 40 has an unillustrated built-in motor for rotating each tool 41.

0024The turret position setting mechanism will now be explained with reference to <figref idref="f0001">FIG. 1</figref>, <figref idref="f0002">FIG. 2</figref>, and <figref idref="f0003">FIG. 3</figref>.

0025The turret position setting mechanism comprises a base 40A. The base 40A is mounted on two rails 15 and 16. The two rails 15 and 16 are laid on the bed 10 in a Z2-axis direction that is parallel with the Z1-axis direction. By driving a Z2-axis motor 17, the base 40A moves in the Z2-axis direction.

0026A ball screw 40B is incorporated into the base 40A such that it extends in an X1-axis direction which is one horizontal direction perpendicular to the Z2-axis. An X1-axis motor 18 for rotating the ball screw 40B is provided at the end of the ball screw 40B.

0027A column 40C is provided on the base 40A. A bracket 40J which is locked to the ball screw 40B is attached to the bottom of the column 40C. When the X1-axis motor 18 rotates, the column 40C moves in the X1-axis direction.

0028A ball screw 40D is incorporated into the column 40C such that it extends in a Y1-axis direction, which is a direction of height perpendicular to the Z2-axis and X1-axis directions. A Y1-axis motor 40E is attached to the end of the ball screw 40D.

0029A bracket 40F is locked to the ball screw 40D. The bracket 40F is movable in the Y1-axis direction. A support unit 40G for supporting the rotation shaft of the turret 40 is rotatably attached to the bracket 40F.

0030The support unit 40G has a direction change motor 40H and a tool selection motor 40I.

0031The direction change motor 40H changes the direction of the turret 40 by rotating the support unit 40G in a plane including the Z2-axis and the X1-axis. The tool selection motor 40I makes the center axis of a selected tool 41 horizontal by rotating the turret 40 about the rotation axis 40K.

0032When the Y1-axis motor 40E rotates, the bracket 40F and the support unit 40G move in the Y1-axis direction. As a result, the height of the centerline of the tool 41 which is selected to be made horizontal is shifted from the height of the centerline of the work W.

0033The above-described is the turret position setting mechanism.

0034The back spindle 50, for example, a chuck and grips the work W, while being opposed to the main spindle 30. The back spindle 50 is supported by a back headstock 50A. The back headstock 50A is mounted on two rails 20 and 21. The two rails 20 and 21 are laid on the bed 10 such that they extend in a Z3-axis direction which is parallel with the Z1-axis direction. By driving a Z3-axis motor 22, the back headstock 50A moves in the Z3-axis direction along the rails 20 and 21. The back headstock 50A has a built-in work rotation motor 51. The work rotation motor 51 rotates the work W gripped by the back spindle 50. The back spindle 50 has a hole 50H through which work W penetrates, so that the work can be gripped by the back spindle 50 and can extend by penetrating through said hole 50H.

0035The main spindle 30 and the back spindle 50 have a hole formed therein, through which the work W penetrates.

0036The lathe further comprises a tool rest 60, a tool magazine 70, a tool exchange mechanism 80, and a guide bush 90.

0037The tool rest 60 is mounted on the rails 20 and 21. By driving a Z4-axis motor 24, the tool rest 60 moves in a Z4-axis direction which is parallel with the Z2-axis direction. An X2-axis motor 25 is provided at a side of the tool rest 60. The X2-axis motor 25 moves the tool rest 60 in an X2-axis direction which is parallel with the X1-axis direction.

0038The tool rest 60 holds a plurality of tools 61 for machining the work W, and has a turret 62 as shown in <figref idref="f0003">FIG. 3</figref>. The tools 61 are attached to the turret 62. A tool 61 corresponding to a rotation angle of the turret 62 is selected for machining. A Y2-axis motor 63 is attached to the top of the tool rest 60. The Y2-axis motor 63 changes the position of the tool rest 60 in a Y2-axis direction which is parallel with the Y1-axis direction, i.e., adjusts the height of the tool rest 60.

0039The guide bush 90 is provided on the main spindle 30 at the side of the back spindle 50. The guide bush 90 slidably supports a portion of the rotating work W that projects from the main spindle 30.

0040In the present example, the tool rest 60 comprises the turret 62. However, a plurality of tools 66 may be arrayed in a support member 65 in a gang arrangement as shown in <figref idref="f0004">FIG. 4. FIG. 4</figref> is a diagram showing a modified example of the tool rest.

0041The tool magazine 70 contains the plurality of tools 41 to be attached to the turret 40. The tool exchange mechanism 80 exchanges a tool 41 attached to the turret 40 with a tool 41 contained in the tool magazine 70.

0042The lathe having the above-described configuration has the main spindle 30, the back spindle 50, and the guide bush 90. Accordingly, even when machining a lengthy work W, the lathe can prevent the work W from being bent and thus can apply a highly precise machining to the work W. Further, the lathe can machine the end surface of the work W.

0043Furthermore, the lathe can machine both end surfaces of the work W by cutting off the work W gripped by the main spindle 30 by a tool attached to, for example, the turret 40, machining one end surface of the work W while gripping the work W by the main spindle 30, then gripping the work W by the back spindle 50 to machine the other end surface of the work W. Accordingly, the lathe can machine works having varied lengths from a short length to a long length, entirely without excluding both end surfaces thereof, into complex shapes.

0044Next, the outline of the control executed by the controller 201 and the operation of the lathe will be explained along with explanation of examples of machining.

0045<figref idref="f0005">FIG. 5</figref> is an explanatory diagram of a machining example 1 in which outer diameter machining is applied to both of a work W1 gripped by the main spindle 30 and a work W2 gripped by the back spindle 50.

0046In a case where the works W1 and W2 gripped by the main spindle 30 and back spindle 50 respectively are to be machined, the controller 201 selects tools 41 for outer diameter machining from the plurality of tools 41 attached to the turret 40 (step S101), and rotates the tool selection motor 40I such that the centerline of the selected tools 41 horizontally faces the works W1 and W2 (step S102). Further, the controller 201 drives the direction change motor 40H to rotate the support unit 40G, and adjusts the direction of the turret 40 in a horizontal plane such that the centerline of the selected tool 41 becomes perpendicular to the centerline of the work W1 (step S103).

0047Then, by driving the Z1-axis motor 13 or the Z2-axis motor 17, the controller 201 positions the portion of the work W1 to be machined in front of the tool 41 (step S104). Then, while rotating the work W1 by driving the work rotation motor 31, the controller 201 drives the Z1-axis motor 13 and the X1-axis motor 18 (step S105). That is, the controller 201 controls the Z1-axis motor 13 and the X1-axis motor 18 such that the tool 41 abuts on the work W1 and machines the outer circumference of the work W1 gripped by the main spindle 30. After finishing machining of the work W1 gripped by the main spindle 30, the controller 201 drives the X1-axis motor 18 to retreat the turret 40 (step S106).

0048Then, the controller 201 drives the direction change motor 40H to rotate the support unit 40G by 180°, and at the same time, drives the tool selection motor 40I to rotate the direction of the selected tool 41 by 180° (step S107). Then, by driving the Z3-axis motor 22 and the Z2-axis motor 17, the controller 201 positions the portion to be machined of the work W2 gripped by the back spindle 50 in front of the selected tool 41 (step S108). While rotating the work W2 by driving the work rotation motor 51, the controller 201 drives the Z3-axis motor 22 and the X1-axis motor 18 (step S109).

0049As a result, the selected tool 41 abuts on the work W2, thereby machining the outer circumference of the work W2 gripped by the back spindle 50. Various kinds of machining are available depending on the kind of the selected tool 41 and the manner of driving the Z1-axis motor 13, the Z2-axis motor 17, the Z3-axis motor 22, and the X1-axis motor 18, and the works W1 and W2 can be formed into a desired shape such as a linear shape, a tapered shape, a circular arc shape, etc.

0050<figref idref="f0006">FIG. 6</figref> is an explanatory diagram of a machining example 2 in which hole drilling machining is applied to an end surface of both of a work W1 gripped by the main spindle 30 and a work W2 gripped by the back spindle 50.

0051In this case, the controller 201 selects a drill having a predetermined diameter from the plurality of tools 41 attached to the turret 40, as a machining tool 41 (step S201). The controller 201 rotates the tool selection motor 40I such that the centerline of the selected tool 41 becomes horizontal (step S202). The controller 201 drives the direction change motor 40H and rotates the support unit 40G such that the centerline of the selected tool 41 becomes parallel with the centerline of the work W1, thereby adjusting the direction of the turret 40 in a horizontal plane (step S203). Then, the controller 201 drives the X1-axis motor 18 to move the turret 40 in the X1-axis direction, and make the tip of the selected tool 41 face the end surface of the work W1 gripped by the main spindle 30 (step S204). Then, the controller 201 drives the Z1-axis motor 13 while rotating the work W1 by driving the work rotation motor 31, and moves the tip of the selected tool 41 toward the main spindle 30 (step S205). As a result, the selected tool 41 cuts the end surface of the work W1 gripped by the main spindle 30, thereby drilling a hole in the work W1 (step S206).

0052After finishing machining of the work W1 gripped by the main spindle 30, the controller 201 drives the X1-axis motor 18 to retreat the turret 40 (step S207). Then, the controller 201 drives the tool selection motor 40I to rotate the turret 40 by 180° and make the tip of the selected tool 41 turn to the end surface of the work W2 gripped by the back spindle 50 (step S208). The controller 201 again drives the X1-axis motor 18 to make the selected tool 41 face the end surface of the work W2 gripped by the back spindle 50 (step S209). The controller 201 drives the Z3-axis motor 22 while rotating the work W2 by driving the work rotation motor 51, and moves the tip of the selected tool 41 toward the back spindle 50 (step S210). Due to this, the selected tool 41 cuts the end surface of the work W2 gripped by the back spindle 50, and a hole is drilled in the work W2 (step S211).

0053The outline of the case where hole drilling machining is applied to an end surface of both of the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50 has been described. However, it is possible to drill a hole in both end surfaces of one work W.

0054In this case, the controller 201 controls the work W to be gripped by only the main spindle 30 (step S301). Then, the controller 201 applies hole drilling machining to the front end surface of the work W (step S302). When finishing hole drilling, the controller 201 drives the X1-axis motor 18 to retreat the turret 40 and the selected tool 41 (step S303). Then, by driving the Z3-axis motor 22, the controller 201 moves the back spindle 50 toward the main spindle 30 and controls the back spindle 50 to grip the end surface of the work W (step S304). After this, the controller 201 controls the main spindle 30 to release the work W (step S305), drives the Z3-axis motor 22 to move to a predetermined position (step S306), and returns the turret 40 and the selected tool 41 to the machining position by driving the X1-axis motor 18 (step S307). Thereafter, by performing the same processes as described above, the controller 201 performs hole drilling in the back end surface of the work gripped by the back spindle 50 (step S308).

0055<figref idref="f0007">FIG. 7</figref> is an explanatory diagram of a machining example 3 in which angled hole drilling is performed (a hole slanted with respect to the axis of the work W is drilled in the work W).

0056In this case, the controller 201 selects a drill from the plurality of tools 41 attached to the turret 40, as a machining tool (step S401).

0057The controller 201 drives the tool selection motor 40I such that the centerline of the selected tool 41 becomes horizontal (step S402). The controller 201 drives the direction change motor 40H to rotate the support unit 40G, and adjusts the direction of the turret 40 such that the centerline of the selected tool 41 is at a desired angle with respect to the center axis of the work W (step S403).

0058Next, the controller 201 drives the Z1-axis motor 13 or the Z2-axis motor 17 to bring the work W to a predetermined position (step S404). After this, the controller 201 drives the Z1-axis motor 13 and the X1-axis motor 18 while rotating the selected tool 41, and moves the work W and the selected tool 41 relatively with respect to each other such that the tip of the selected tool 41 enters the work W at the desired angle with respect to the center axis of the work W (step S405). As a result, an angled hole is drilled in the work W gripped by the main spindle 30.

0059In a case where an angled hole is to be drilled in the work W gripped by the back spindle 50, the controller 201 drives the direction change motor 40H before drilling, in order to adjust the direction of the turret 40 such that the centerline of the tool 41 is at a desired angle with respect to the center axis of the work W gripped by the back spindle 50 (step S406). Next, the controller 201 drives the Z3-axis motor 22 or the Z2-axis motor 17 to bring the work W to a predetermined position (step S407). After this, the controller 201 concurrently drives the Z3-axis motor 22 and the X1-axis motor 18 while rotating the selected tool 41, to move the work W and the selected tool 41 relatively with respect to each other such that the tip of the selected tool 41 enters the work W at the desired angle (step S408). As a result, an angled hole is drilled in the work W gripped by the back spindle 50.

0060<figref idref="f0008">FIG. 8</figref> is an explanatory diagram of a machining example 4 where inner diameter machining is performed.

0061In a case where inner diameter machining is to be applied to the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50, the controller 201 selects a tool 41 for inner diameter machining from the plurality of tools 41 attached to the turret 40 as a machining tool 41, and performs the same processes as for drilling a hole in the end surface.

0062That is, the controller 201 drives the direction change motor 40H to rotate the support unit 40G such that the centerline of the tool 41 for inner diameter machining becomes parallel with the centerline of the work W1, and adjusts the direction of the turret 40 (step S501). Then, the controller 201 drives the X1-axis motor 18 to make the tip of the selected tool 41 face the end surface of the work W1 gripped by the main spindle 30 (step S502). Next, while rotating the work W1 by driving the work rotation motor 31, the controller 201 drives the Z1-axis motor 13 to relatively move the tip of the selected tool 41 toward the main spindle 30 (step S503). Due to this, the selected tool 41 cuts the end surface of the work W1 gripped by the main spindle 30, thereby starting inner diameter machining of the work W1. Then, by driving the Z1-axis motor 13 and the X1-axis motor 18, the selected tool 41 is moved in the Z1-axis direction and in the X1-axis direction, and a hole having a desired inner diameter is thereby formed in the work W1 gripped by the main spindle 30.

0063After finishing the machining of the work W1 gripped by the main spindle 30, the controller 201 drives the X1-axis motor 18 to retreat the turret 40 (step S504). The controller 201 drives the tool selection motor 40I to rotate the selected tool 41 by 180° and make the tip of the selected tool 41 face the end surface of the work W2 gripped by the back spindle 50 (step S505). Then, the controller 201 rotates the work W2 by driving the work rotation motor 51, and drives the Z3-axis motor 22 to move the tip of the selected tool 41 toward the back spindle 50 (step S506). Then, by driving the Z3-axis motor 22 and the X1-axis motor 18, the controller 201 moves the selected tool 41 in the Z3-axis direction and in the X1-axis direction, thereby cutting the end surface of the work W2 gripped by the back spindle 50 (step S507). Due to this, a hole having a desired inner diameter is formed in the end surface of the work W2 gripped by the back spindle 50.

0064<figref idref="f0009">FIG. 9</figref> is an explanatory diagram of a machining example 5 in which the work W is cut linearly.

0065In a case where the work W is to be formed into a D character shape by cutting a portion of the work W, an end mill is attached to the turret 40 as a machining tool 41. The controller 201 drives the tool selection motor 40I and rotates the turret 40 such that the centerline of the selected tool 41 becomes horizontal. After this, the controller 201 drives the Y1-axis motor 40E while rotating the selected tool 41, to move the selected tool 41 in the Y1-axis direction, i.e., in the upward and downward direction, as shown in <figref idref="f0009">FIG. 9</figref>. Due to this, the work W is cut and the cross section of the work W becomes a D character shape.

0066<figref idref="f0010">FIG. 10</figref> is an explanatory diagram of a machining example 6 in which an eccentric hole is drilled.

0067In a case where an eccentric hole is formed in the work W by drilling a portion that is decentered from the centerline of the work W, a drill is attached to the turret 40. The controller 201 selects the drill as a machining tool 41, and drives the tool selection motor 40I to rotate the turret 40 such that the centerline of the selected tool 41 becomes horizontal. Then, the controller 201 moves the turret 40 to a predetermined position by driving the Z2-axis motor 17, and thereafter, drives the Y1-axis motor 40E to move the centerline of the selected tool 41 off from the height of the centerline of the work W . Next, while rotating the selected tool 41, the controller 201 advances the tool 41 as shown in <figref idref="f0010">FIG. 10</figref> by driving the X1-axis motor 18. As a result, an eccentric hole is formed in the work W.

0068<figref idref="f0011">FIG. 11A and FIG. 11B</figref> are explanatory diagrams of a machining example 7 in which the end portion of the work W is obliquely cut, where <figref idref="f0011">FIG. 11A</figref> shows a front elevation and <figref idref="f0011">FIG. 11B</figref> shows a side elevation.

0069In a case where the work W is to be obliquely cut, an end mill is attached to the turret 40 as a tool 41. The controller 201 selects the end mill 41 as a machining tool (step S601), drives the tool selection motor 40I to rotate the turret 40 such that the centerline of the selected tool 41 becomes horizontal (step S602). Then, by driving the direction change motor 40H, the controller 201 adjusts the direction of the turret 40 such that the centerline of the selected tool 41 is at a desired angle with respect to the centerline of the work W gripped by the main spindle 30 (step S603). The controller 201 drives the Y1-axis motor 40E to move the selected tool 41 in the Y1-axis direction (step S604). Due to this, the end mill 41 obliquely contacts the end portion of the work W, thereby obliquely cutting the end portion of the work W.

0070<figref idref="f0012">FIG. 12A and FIG. 12B</figref> are explanatory diagrams of a machining example 8 in which hob machining is applied to the work W, where <figref idref="f0012">FIG. 12A</figref> shows a front elevation and <figref idref="f0012">FIG. 12B</figref> shows a side elevation.

0071In a case where hob machining for forming the work W into a toothed gear is performed, a hob is attached to the turret 40 as a tool 41. The controller 201 selects the hob as a machining tool 41 (step S701), and drives the tool selection motor 40I to make the centerline of the hob horizontal (step S702). Next, the controller 201 moves the turret 40 to a predetermined position (step S703), and drives the direction change motor 40H to adjust the direction of the turret 40 such that the centerline of the selected tool is at a predetermined angle with respect to the centerline of the work W (step S704). Then, the controller 201 advances the work W by driving the Z1-axis motor 13, while synchronously controlling the rotation of the selected hob 41 and the rotation of the work W at a predetermined speed ratio (step S705). Due to this, the work W is moved while being cut by the selected tool 41, and a toothed gear is formed on the work W.

0072<figref idref="f0013">FIG. 13</figref> is an explanatory diagram of a machining example 9 in which outer diameter machining is applied to the work W by using a tool 41 and a tool 61.

0073In a case where outer diameter machining of the work W is performed by using the tool 41 attached to the turret 40 and the tool 61 attached to the tool rest 60, an outer diameter machining tool is attached to the turret 40. The controller 201 selects the outer diameter machining tool as a machining tool 41 (step S801), and drives the tool selection motor 40I to make the centerline of the selected tool 41 horizontal (step S802).

0074The controller 201 controls the main spindle 30, the back spindle 50, and the turret 40, in the same manner as for applying outer diameter machining to the work W by using only the tool 41.

0075On the other hand, an outer diameter machining tool is pre-attached to the tool rest 60 as a tool 61. As to the tool rest 60, the controller 201 rotates the turret 62 such that the selected tool 61 faces the outer circumferential surface of the work W (step S803), drives the X2-axis motor 25 (step S804) to make the tool 61 cut the outer circumference of the work W. Due to this, the outer diameter of the work W is machined by the tool 41 and the tool 61. The tool 41 and the tool 61 cut the work W while being positioned oppositely to each other with the work W placed therebetween. Accordingly, the work W is prevented from being fluctuated, and highly precise machining can be applied thereto. Further, since the outer diameter of the work W is machined by the two tools 41 and 61 simultaneously, the total machining time can be shortened.

0076<figref idref="f0014">FIG. 14</figref> is an explanatory diagram of a machining example 10 in which hole drilling machining is applied to the work W by using the tool 41 and the tool 61.

0077In a case where hole drilling machining is applied to the work W, drills are attached to the turret 40 and the tool rest 60 respectively. The controller 201 selects the drill on the tool rest 60 (step S901), and rotates the turret 62 such that the centerline of the selected tool 61 horizontally faces the work W (step S902). Further, the controller 201 selects the drill on the turret 40 as a machining tool 41 (step S903), and drives the tool selection motor 40I such that the centerline of the selected tool 41 horizontally faces the work W (step S904).

0078Next, the controller 201 drives the Z2-axis motor 17 and the Z4-axis motor 24 to move the selected tools 41 and 61 to predetermined positions (step S905). After this, while rotating the tool 41 and the tool 61, the controller 201 drives the X1-axis motor 18 and the X2-axis motor 25 to advance the tool 41 and the tool 61 toward the work W (step S906). By advancing, the tool 41 and the tool 61 abut on the work W and cut it. Due to this, holes are formed symmetrically in the work W.

0079The tool 41 and the tool 61 cut the work W while being positioned oppositely to each other with the work W placed therebetween. Accordingly, the work W can be prevented from being fluctuated, and highly precise machining can be applied thereto. Further, since the work W is machined by the two tools 41 and 61 simultaneously, the total machining time can be shortened, as compared to a case where only the tool 41 is used for machining.

0080<figref idref="f0015">FIG. 15</figref> is an explanatory diagram of a machining example 11 in which two works W1 and W2 are machined simultaneously.

0081For example, in a case where machining for boring an eccentric hole in the end portion of the work W1 gripped by the main spindle 30 is performed, and at the same time, outer diameter machining is applied to the work W2 gripped by the back spindle 50, an outer diameter machining tool is attached to the turret 40 and a drill is attached to the tool rest 60.

0082The controller 201 selects the outer diameter machining tool from the plurality of tools 41 attached to the turret 40 as a machining tool 41 (step S1001), and controls the centerline of the selected tool 41 to become horizontal at the same height as the work W2 gripped by the back spindle 50 and to face the work W2 in this state. The controller 201 selects the drill on the tool rest 60 as a machining tool 61, and adjusts the selected tool 61 such that its tip faces the portion to be machined of the work W1 gripped by the main spindle 30 by rotating the turret 62 and driving the X2-axis motor 25 (step S1002). Then, the controller 201 drives the X1-axis motor 18 to advance the selected tool 41 to a predetermined position (step S1003). Further, the controller 201 controls the selected tool 61 to advance toward the work W1 gripped by the main spindle 30 by driving the Z1-axis motor 13 while rotating the tool 61. As a result, an eccentric hole (a hole bored at a position decentered from the center of the work W1) is bored in the end portion of the work W1 gripped by the main spindle 30.

0083In parallel with these operations, the controller 201 drives the work rotation motor 51 to rotate the work W2, and drives the X3-axis motor 22 to advance the work W2 (step S1004). Due to this, the outer circumferential surface of the work W2 gripped by the back spindle 50 is cut.

0084<figref idref="f0016">FIG. 16</figref> is an explanatory diagram of a machining example 12 in which two works W1 and W2 are machined simultaneously.

0085A desired machining tool 41, for example, an outer shape machining tool is attached to the turret 40, and a desired machining tool 61, for example, an outer shape machining tool is attached to the tool rest 60.

0086As shown by solid lines, the work W1 gripped by the main spindle 30 is machined by the tool 41 attached to the turret 40, and the work W2 gripped by the back spindle 50 is simultaneously machined by the tool 61 attached to the tool rest 60.

0087Further, the work W1 gripped by the main spindle 30 is machined by the tool 41 attached to the turret 40 and the tool 61 attached to the tool rest 60 as shown by solid lines and one-dot dashed lines, and before or after this, the work W2 gripped by the back spindle 50 is machined by the tool 41 attached to the turret 40 and the tool 61 attached to the tool rest 60 as shown by solid lines and one-dot dashed lines.

0088<figref idref="f0017">FIG. 17</figref> is an explanatory diagram of a machining example 13 in which a "wrench application unit" is formed on the work W.

0089In a case where a "wrench application unit" is formed on the work W, end mills are attached to the turret 40 and to the turret 62 of the tool rest 60. The controller 201 selects these end mills as machining tools 41 and 61 (step S1101), and makes the centerlines of the tools 41 and 61 horizontal (step S1102).

0090The controller 201 moves the tools 41 and 61 to predetermined positions (step S1103). After this, the controller 201 drives the Y1-axis motor 40E and the Y2-axis motor 63 to move the tools 41 and 61 in the Y1-axis direction and the Y2-axis direction respectively (step S1104). Due to this, the both sides of the work W are cut, and a wrench application unit is formed thereon. The controller 201 may repeat the operation of moving the tools 41 and 61 in the Y1-axis direction and Y2-axis direction while moving them in the Z-axis directions (directions perpendicular to the drawing sheet) respectively.

0091<figref idref="f0018">FIG. 18</figref> is an explanatory diagram of a machining example 14 in which eccentric orifices are formed in two positions of the work W.

0092In a case where eccentric holes are formed in two positions of the work W, drills are attached to the turret 40 and the turret 62 of the tool rest 60. The controller 201 selects these drills as machining tools 41 and 61 (step S1201), and makes the centerlines of the selected tools 41 and 61 horizontal (step S1202). The controller 201 moves the tools 41 and 61 to predetermined positions in the Z2-axis direction and the Z4-axis direction by driving the Z2-axis motor 17 and the Z4-axis motor 24 (step S1203). Then, the controller 201 drives the Y1-axis motor 40E and the Y2-axis motor 63 to adjusting the tools 41 and 61 to be at predetermined positions in the Y1-axis direction and the Y2-axis direction (step S1204). Next, the controller 201 advances the tools 41 and 61 by driving the X1-axis motor 18 and the X2-axis motor 25 (step S1205). As a result, the work W is bored and two eccentric holes are formed simultaneously.

0093The lathe according to the present example has the following effects. <ol id="ol0003" compact="compact" ol-style=""><li>(1) The lathe according to the present example comprises the main spindle 30, the turret 40, the back spindle 50, and the guide bush 90. Accordingly, when the lathe applies machining to a lengthy work W, it prevents the work W from being bent, enabling a highly precise machining. Further, this lathe can apply machining to the end surface of the work W. Furthermore, this lathe can apply machining to both end surfaces of the work W by once cutting off the work W gripped by the main spindle 30, and after this handing the work W gripped by the main spindle 30 to the back spindle 50. Therefore, this lathe can apply machining to works having varied length from short length to long length, entirely without excluding both end surfaces thereof, into complex shapes.</li><li>(2) The work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50 can both be machined without the lathe being stopped.</li><li>(3) Since the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50 can be machined by a common tool 41, there is no need of preparing a same kind of tool in a plural number.</li><li>(4) Since the lathe comprises the tool magazine 70, it is possible to prepare plural kinds of tools 41 in advance.</li><li>(5) Since the lathe comprises the tool exchange mechanism 80, it is possible to exchange tools 41 without stopping the lathe.</li><li>(6) The turret 40 can be moved in the Y1-axis direction. Therefore, the position of the tool 41 is movable three-dimensionally, enabling complicated machining such as boring an eccentric hole or an angled hole in the work W, hob machining, etc.</li><li>(7) Since the tool rest 60 is provided, a tool to be used next can be prepared at the tool rest 60 while other machining is applied by using, for example, the tool 41 on the turret 40.</li><li>(8) Since machining can be applied by using the tool 41 and the tool 61 simultaneously, machining time can be shortened.</li><li>(9) Since machining can be applied by using the tool 41 and the tool 61 simultaneously, one can be used for rough machining and the other can be used for finishing machining.</li><li>(10) Since machining can be applied by using the tool 41 and the tool 61 simultaneously, different portions of the work W can be machined simultaneously.</li><li>(11) Since a plurality of tools 41 can be attached to the turret 40, there is no need of stopping the lathe each time the tools 41 are exchanged, resulting in a high machining efficiency.</li><li>(12) Since the back spindle 50 is provided with a hole through which the work W penetrates, a further lengthy work W can be attached to the lathe. This eliminates the need of upsizing the lathe.</li></ol>

0094<figref idref="f0019">FIG. 19</figref> is a front elevation of a lathe according to an embodiment of the present invention. <figref idref="f0020">FIG. 20</figref> is a plan view of the lathe. <figref idref="f0021">FIG. 21</figref> is a diagram showing an example of configuration of a tool spindle and a tool rest shown in <figref idref="f0019">FIG. 19</figref>. In these <figref idref="f0019 f0020 f0021">FIGS. 19 to 21</figref> and <figref idref="f0022 f0023 f0024 f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032 f0033 f0034 f0035 f0036">FIGS. 22 to 36</figref> to be mentioned later, same reference numerals as those used in the explanatory example are used for same or corresponding elements.

0095This lathe is a machine capable of applying complex machining to a work W. As shown in <figref idref="f0019">FIG. 19</figref> and <figref idref="f0020">FIG. 20</figref>, the lathe comprises a bed 10, a main spindle 30 for gripping the work W, a tool spindle 100, a back spindle 50 for gripping the work W, and a controller 201. The controller 201 controls the entire lathe.

0096A headstock 30A supporting the main spindle 30 is mounted on two rails 11 and 12 which are laid on the bed 10 in parallel with a Z1-axis direction. The rails 11 and 12 are laid on the bed 10 so as to extend in parallel with the Z1-axis direction. The headstock 30A is designed so as to move on the rails 11 and 12 in the Z1-axis direction by driving a Z1-axis motor 13. The headstock 30A has a built-in work rotation motor 31. The work rotation motor 31 rotates the work W gripped by the main spindle 30.

0097The tool spindle 100 rotatably grips an exchangeable tool 101. The tool spindle 100 is supported by a tool headstock 100A.

0098The tool headstock 100A is mounted on two rails 15 and 16. The rails 15 and 16 are laid on the bed 10 so as to extend in a Z2-axis direction parallel with the Z1-axis direction. By driving a Z2-axis motor 17, the tool headstock 100A moves on the rails 15 and 16 in the Z2-axis direction.

0099An X1-axis motor 18 which moves the tool headstock 100A in an X1-axis direction perpendicular to the Z2-axis direction is provided at a side of the tool headstock 100A. A direction change motor 103 and a Y1-axis motor 102 are attached to the upper portion of the tool headstock 100A. The direction change motor 103 changes the direction of a tool 101 by rotating the tool headstock 100A. The Y1-axis motor 102 changes the position of the tool headstock 100A in a Y1-axis direction (direction of height) perpendicular to the Z2-axis direction and the X1-axis direction.

0100The back spindle 50 grips the work W while being opposed to the main spindle 30. The back spindle 50 is supported by a back headstock 50A. The back headstock 50A is mounted on two rails 20 and 21 laid on the bed 10 in a Z3-axis direction parallel with the Z1-axis direction. The rails 20 and 21 are laid on the bed 10 so as to extend in a Z3-axis direction parallel with the Z1-axis direction. The back headstock 50A is designed so as to move in the Z3-axis direction by driving a Z3-axis motor 22. A work rotation motor 51 is built in the back headstock 50A. The work rotation motor 51 rotates the work W gripped by the back spindle 50.

0101The main spindle 30 and the back spindle 50 have a hole formed therein, through which the work W penetrates. The lathe further comprises a tool rest 60, a tool magazine 70, a tool exchange mechanism 80, and a guide bush 90.

0102The tool rest 60 is mounted on rails 20 and 21. The tool rest 60 is designed so as to move in a Z4-axis direction parallel with the Z2-axis direction, by driving a Z4-axis motor 24. An X2-axis motor 25 which moves the tool rest 60 in an X2-axis direction parallel with the X1-axis direction is provided at a side of the tool rest 60.

0103The tool rest 60 holds a plurality of tools 61 for machining the work W. The tool rest 60 has a turret 62, as shown in <figref idref="f0021">FIG. 21</figref>. The tools 61 are attached to the turret 62. A tool 61 corresponding to a rotation angle of the turret 62 is selected for machining. A Y2-axis motor 63 is attached to the upper portion of the tool rest 60. The Y2-axis motor 63 changes the position of the tool rest 60 in a Y2-axis direction (direction of height) parallel with the Y1-axis direction.

0104The guide bush 90 is provided on the main spindle 30 at a side of the back spindle 50. The guide bush 90 slidably supports a portion of the work W that projects from the main spindle 30.

0105In the present embodiment, the tool rest 60 has the turret 62. However, the present invention is not limited to this, but a plurality of tools 66 may be arrayed in a support member 65 in a gang arrangement, as shown in <figref idref="f0022">FIG. 22. FIG. 22</figref> is a diagram showing a modified example of the tool rest.

0106The tool magazine 70 contains a necessary number of tools 101 to be attached to the tool spindle 100. The tool exchange mechanism 80 comprises a mechanism for exchanging an arbitrary one of a plurality of tools 101 attached to the tool spindle 100, with any of the tools 101 contained in the tool magazine 70.

0107Next, the operation of the lathe will be explained along with explanation of examples of machining.

0108<figref idref="f0023">FIG. 23</figref> is an explanatory diagram of a machining example 15 in which outer diameter machining is applied to both of a work W1 gripped by the main spindle 30 and a work W2 gripped by the back spindle 50.

0109In this case, the main spindle 30 grips the work W1 and the back spindle 50 grips the work W2.

0110Next, the controller 201 positions the portion to be machined of the work W1 gripped by the main spindle 30 in front of the tool spindle 100, by driving the Z1-axis motor 13 and the Z2-axis motor 17 (step S1301).

0111The controller 201 drives the Z1-axis motor 13 and the X1-axis motor 18 while rotating the work W1 by driving the work rotation motor 31 (step S1302). As a result, the tool 101 abuts on the work W1, thereby machining the outer circumference of the work W1 gripped by the main spindle 30. The controller 201 retreats the tool spindle 100 by driving the X1-axis motor 18, after machining of the work W1 is finished (step S1303).

0112Then, the controller 201 rotates the tool 101 of the tool spindle 100 by 180° (step S1304). Then, by driving the Z3-axis motor 22 and the Z2-axis motor 17, the controller 201 positions the portion to be machined of the work W2 gripped by the back spindle 50 in front of the tool spindle 100 (step S1305). Next, the controller 201 rotates the work W2 by driving the work rotation motor 51 (step S1306), and drives and controls the Z3-axis motor 22 and the X1-axis motor 18 (step S1307). As a result, the tool 101 abuts on the work W2, thereby machining the outer circumference of the work W2 gripped by the back spindle 50.

0113The controller 201 applies various machining to the work W1 and the work W2 by appropriately managing the kinds of tools 11, the Z1-axis motor 13, the Z2-axis motor 17, the Z3-axis motor 22, and the X1-axis motor 18. For example, the work W1 and the work W2 are machined to have a linear outer circumference, or to have a tapered shape, or to have an outer circumference having a desired shape such as a circular arc shape, etc.

0114<figref idref="f0024">FIG. 24</figref> is an explanatory diagram of a machining example 16 in which a hole is drilled in the end surface of both of the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50.

0115In this case, the tool 101 to be attached to the tool spindle 100 is a drill.

0116The controller 201 drives the X1-axis motor 18 and the direction change motor 103 to control the tip of the tool 101 to face the end surface of the work W1 gripped by the main spindle 30 (step S1401). Next, while rotating the work W1 by driving the work rotation motor 31, the controller 201 drives the Z1-axis motor 13 so that the tip of the tool 101 advances toward the main spindle 30 (step S1402). Due to this, the tool 101 drills the end surface of the work W1, thereby drilling a hole in the end surface of the work W1.

0117After machining of the work W1 at the side of the main spindle 30 is finished, the controller 201 drives the X1-axis motor 18 to retreat the tool spindle 100 (step S1403). Then, the controller 201 drives the direction change motor 103 to control the tip of the tool 101 to face the end surface of the work W2 gripped by the back spindle 50 (step S1404). Then, while rotating the work W2 by driving the work rotation motor 51, the controller 201 drives the Z3-axis motor 22 so that the tip of the tool 101 advances toward the back spindle 50 (step S1405). Due to this, the tool 101 abuts on the end surface of the work W2 to drill the end surface, thereby drilling a hole in the work W2.

0118The above explanation shows the outline of the case where hole drilling machining is applied to the end surface of both of the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50. However, a hole can be drilled in both end surfaces of one work W.

0119In this case, the controller 201 first causes the work W to be gripped by the main spindle 30 (step S1401). Next, the controller 201 controls the tool 101 to drill a hole in one end surface of the work W (step S1402). When hole drilling is finished, the controller 201 drives the X1-axis motor 18 to retreat the tool spindle 100, and drives the Z3-axis motor 22 to move the back spindle 50 toward the main spindle 30 so that the end portion of the work W is gripped by the back spindle 50 (step S1403). After this, the controller 201 controls the main spindle 30 to release the work W (step S1404). Next, the controller 201 drives the Z3-axis motor 22 to move the back spindle 50 to a predetermined position (step S1405), and drives the X1-axis motor 18 to return the tool spindle 100 to the machining position (step S1406). After this, the tool 101 drills a hole in the other end surface of the work W in the same way as described above (step S1407).

0120<figref idref="f0025">FIG. 25</figref> is an explanatory diagram of a machining example 17 in which an "angled hole" is formed in the work.

0121In this case, the tool 101 to be attached to the tool spindle 100 is a drill.

0122Before the work W1 gripped by the main spindle 30 is machined, the controller 201 drives the direction change motor 103 to control the tool 101 to be at a desired angle to the axis of the work W1 gripped by the main spindle 30 (step S1501).

0123Next, the controller 201 drives the Z1-axis motor 13 or the Z2-axis motor 17 to adjust the relative positions of the work W1 and the tool 101 with respect to each other (step S1502). After this, while rotating the tool 101, the controller 201 simultaneously drives the Z1-axis motor 13 and the X1-axis motor 18 to relatively move the work W1 and the tool 101 in a manner that the tip of the tool 101 enters the work W1 at the desired angle to the axis of the work W1 (step S1503). Due to this, an angled hole is drilled in the work W1 gripped by the main spindle 30.

0124In a case where an angled hole is drilled in the work W2 gripped by the back spindle 50, the controller 201 controls the direction change motor 103 in a manner that the tool 101 is at a desired angle to the axis of the work W2 (step S1504). Next, the controller 201 drives the Z3-axis motor 22 or the Z2-axis motor 17 to adjust the relative positions of the tool 101 and the work W2 with respect to each other (step S1505). After this, while rotating the tool 101, the controller 201 synchronously drives the Z3-axis motor 22 and the X1-axis motor 18 to relatively move the work W2 and the tool 101 in a manner that the tip of the tool 101 enters the work W2 at the desired angle (step S1506). Due to this, an angled hole is drilled in the work W2.

0125<figref idref="f0026">FIG. 26</figref> is an explanatory diagram of a machining example 18 in which a hole having a desired diameter is formed in the work W (inner diameter machining is applied to the work W).

0126In a case where inner diameter machining is applied to the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50, the controller 201 performs the same process as applying hole drilling machining to an end surface, with an inner diameter machining tool attached to the tool spindle 100 as the tool 101. That is, the controller 201 controls the X1-axis motor 18 and the direction change motor 103 such that the tool 101 and the work W1 gripped by the main spindle 30 becomes coaxial and the tip of the tool 101 faces the end surface of the work W1 gripped by the main spindle 30 (step S1601). Next, the controller 201 drives the Z1-axis motor 13 or the Z2-axis motor 17 to move the tip of the tool 101 toward the main spindle 30 while rotating the work W1 by driving the work rotation motor 31 (step S1602). The controller 201 controls the Z1-axis motor 13 and the X1-axis motor 18 to move the tool 101 in the Z1-axis direction and the X1-axis direction and form a hole in the end surface of the work W1 by cutting the work W1, and adjusts the diameter and the depth of the hole (step S1603).

0127After machining of the work W2 is finished, the controller 201 drives the X1-axis motor 18 to retreat the tool spindle 100 (step S1604).

0128Subsequently, the controller 201 drives the direction change motor 103 to rotate the tool spindle 100 by 180° so that the tip of the tool 101 faces the end surface of the work W2 gripped by the back spindle 50 (step S1605). Then, the controller 201 drives the work rotation motor 51 to rotate the work W2 and drives the Z3-axis motor 22 or the Z2-axis motor 17 to relatively move the tip of the tool 101 toward the back spindle 50 (step S1606). Then, by controlling the Z3-axis motor 22 and the X1-axis motor 18, the controller 201 moves the tool 101 in the Z3-axis direction and the X1-axis direction to form a hole in the work W2, and adjusts the depth, diameter, and position of the hole (step S1607).

0129<figref idref="f0027">FIG. 27</figref> is an explanatory diagram of a machining example 19 in which the work W is cut linearly.

0130In a case where a portion of the work W is cut to form the cross section of the work W into a D character shape, an end mill is attached to the tool spindle 100 as the tool 101. The controller 201 moves the tool spindle 100 to a predetermined position (step S1701). After this, the controller 201 drives the Y1-axis motor 102 to move the end mill in the Y1-axis direction while rotating the tool 101 (step S1702). In accordance with necessity, the controller 201 moves the tool spindle 100 in the Z2-axis direction (the direction of axis of the work W) (step S1703). Due to this, the work W is cut and the cross section of the work W becomes a D character shape.

0131<figref idref="f0028">FIG. 28</figref> is an explanatory diagram of a machining example 20 in which an eccentric hole is formed in the work W.

0132In a case where a hole (eccentric hole) is formed in a position decentered from the center axis of the work W, a drill is attached to the tool spindle 100 as the tool 101. The controller 201 drives the Z2-axis motor 17 to move the tool spindle 100 to a predetermined position (step S1801). Then, the controller 201 drives the Y1-axis motor 102 to make the height of the tool 101 differ from the height of the center of the work W (step S1802). Then, while rotating the tool 101, the controller 201 drives the X1-axis motor 18 to advance the tool 101 and form a hole in the work W (step S1803). Due to this, an eccentric hole is formed in the work W.

0133<figref idref="f0029">FIGS. 29A and 29B</figref> are explanatory diagrams of a machining example 21 in which the end portion of the work is obliquely cut, where <figref idref="f0029">FIG. 29A</figref> shows a front elevation and <figref idref="f0029">FIG. 29B</figref> shows a side elevation.

0134In a case where the end portion of the work W is obliquely cut, an end mill is attached to the tool spindle 100 as the tool 101. The controller 201 drives the direction change motor 103 such that the tool 101 is at a desired angle to the axis of the work W gripped by the main spindle 30 (step S1901). Then, the controller 201 drives the Y1-axis motor 102 to move the tool 101 in the Y1-axis direction (step S1902). Due to this, the tool 101 obliquely abuts on the end portion of the work W, thereby cutting the end portion of the work W obliquely. In accordance with necessity, the controller 201 moves the tool spindle 100 and the work W relatively in the X-axis direction and Z-axis direction.

0135<figref idref="f0030">FIGS. 30A and 30B</figref> are explanatory diagrams of a machining example 22 in which hob machining is applied to the work W, where <figref idref="f0030">FIG. 30A</figref> shows a front elevation and <figref idref="f0030">FIG. 30B</figref> shows a side elevation.

0136In a case where hob machining for forming a toothed gear is applied, a hob is attached to the tool spindle 100 as the tool 101. The controller 201 moves the tool spindle 100 to a predetermined position (step S2001). Then, the controller 201 drives the direction change motor 103 to make the tool 101 to be at a predetermined angle (step S2002).

0137The controller 201 controls the rotation of the tool 101 and the rotation of the work W to be synchronous with each other at a predetermined speed ratio, and advances the work W by driving the Z1-axis motor 13 (step S2003). Due to this, the work W moves while being cut by the tool 101, and a toothed gear is formed on the work W.

0138<figref idref="f0031">FIG. 31</figref> is an explanatory diagram of a machining example 23 in which outer diameter machining is applied to the work W using the tool 101 and the tool 61.

0139In a case where outer diameter machining is applied to the work W by using the tool 101 attached to the tool spindle 100 and the tool 61 attached to the tool rest 60, an outer diameter machining tool is attached to the tool spindle 100 as the tool 101 and an outer diameter machining tool is selected as the tool 61.

0140The controller 201 controls the main spindle 30, the back spindle 50, and the tool spindle 100, in the same manner as for applying outer diameter machining to the work W using only the tool 101.

0141The controller 201 controls the tool rest 60 such that the turret 62 rotates and the selected tool 61 faces the outer circumferential surface of the work W, and drives the X2-axis motor 25 such that the tool 61 cuts the outer circumference of the work W. The tool 101 and the tool 61 cut the work W while being opposed to each other with the work W positioned therebetween. Accordingly, the work W is prevented from being fluctuated and a highly precise machining can be applied thereto. Further, since the outer diameter of the work W is machined by the two tools 101 and 61 simultaneously, the total machining time can be shortened.

0142<figref idref="f0032">FIG. 32</figref> is an explanatory diagram of a machining tool 24 in which hole drilling machining is applied to the work W.

0143In a case where hole drilling machining is applied to the work W, a drill is attached to the tool spindle 100 as the tool 101, and a drill is selected as the tool 61 of the tool rest 60. The controller 201 rotates the turret 62 to make the selected tool 61 face the work W (step S2011). Then, the controller 201 drives the Z2-axis motor 17 and the Z4-axis motor 24 to move the tool 101 and the tool 61 to predetermined positions (step S2012). After this, while rotating the tool 101 and the tool 61, the controller 201 drives the X1-axis motor 18 and the X2-axis motor 25 to advance the tool 101 and the tool 61 toward the work W so that the work W is cut by the tool 101 and the tool 61 (step S2013). Due to this, holes are symmetrically formed in the work W. The tool 101 and the tool 61 cut the work W while being opposed to each other with the work W positioned therebetween. Accordingly, the work W is prevented from being fluctuated, and a highly precise machining is available. Further, since the work W is machined by the two tools 101 ad 61 simultaneously, the total machining time can be shorter than a case where machining is applied by using only the tool 101.

0144<figref idref="f0033">FIG. 33</figref> is an explanatory diagram of a machining example 25 in which two works W1 and W2 are machined simultaneously.

0145For example, in a case where machining for forming an eccentric hole is applied to the end surface of the work W1 gripped by the main spindle 30 and outer diameter machining is applied to the work W2 gripped by the back spindle 50, an outer diameter machining tool is attached to the tool spindle 100 as the tool 101.

0146The controller 201 drives the X1-axis motor 18 to advance the tool 101 to a predetermined position (step S2101). The controller 201 rotates the turret 62 to select a drill as the tool 61 of the tool rest 60 (step S2102). Next, the controller 201 drives the X2-axis motor 25 to adjust the selected tool 61 such that its tip faces the portion of the work W1 that is to be machined (step S2103). Then, while rotating the tool 61, the controller 201 drives the Z1-axis motor 13 to advance the work W1 gripped by the main spindle 30 (step S2104).

0147Along with this process, the controller 201 rotates the work W2 by driving the work rotation motor 51 and drives the Z3-axis motor 22 to advance the work W2 gripped by the back spindle 50 (step S2105). Due to this, an eccentric hole is formed in the end surface of the work W1 and the outer circumferential surface of the work W2 is cut.

0148<figref idref="f0034">FIG. 34</figref> is an explanatory diagram of a machining example 26 in which the two works W1 and W2 are machined simultaneously.

0149For example, in a case where outer diameter machining is applied to the work W2 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50, the tool 101 attached to the tool spindle 100 and the tool 61 attached to the tool rest 61 may simultaneously apply machining to one work W, or the tool 101 and the tool 61 may independently apply machining to the work W1 and the work W2 respectively.

0150<figref idref="f0035">FIG. 35</figref> is an explanatory diagram of a machining example 27 in which a wrench application unit is formed on the work W.

0151In a case where a wrench application unit is formed on the work W, an end mill is attached to the tool spindle 100 as the tool 101. The controller 201 selects an end mill as the tool 61 of the tool rest 60 (step S2201). After this, the controller 201 moves the tools 101 and 61 to predetermined positions, and drives the Y1-axis motor 102 and the Y2-axis motor 63 to move the tool 101 and the tool 61 in the Y1-axis direction and the Y2-axis direction respectively (step S2202). Due to this, the both sides of the work W are cut and a wrench application unit is formed.

0152<figref idref="f0036">FIG. 36</figref> is an explanatory diagram of a machining example 28 in which eccentric holes are formed in the work W.

0153In a case where eccentric holes are formed in two portions of the work W, a drill is attached to the tool spindle 100 as the tool 101. The controller 201 selects a drill as the tool 61 of the tool rest 60. The controller 201 moves the tool 101 and the tool 61 to predetermined positions in the Z2-axis direction and the Z4-axis direction. After this, the controller 201 drives the Y1-axis motor 102 and the Y2-axis motor 63 to adjust the tool 101 and the tool 61 to be at predetermined positions in the Y1-axis direction and the Y2-axis direction. Next, the controller 201 advances the tool 101 and the tool 61 by driving the X1-axis motor 18 and the X2-axis motor 25. Due to this, hole drilling machining is applied to the work W and two eccentric holes are simultaneously formed.

0154As described above, the lathe according to the present embodiment has the following operation effects. <ol id="ol0004" compact="compact" ol-style=""><li>(1) Since the lathe comprises the main spindle 30, the tool spindle 100, the back spindle 50, and the guide bush 90, even when a lengthy work W is machined, it can be prevented from being bent. Accordingly, highly precise machining is available. Further, an end surface of the work W can be machined. Furthermore, both end surfaces of the work W can be machined by machining the work W gripped by the main spindle 30, and after this machining is finished, by machining the work W by moving the work W from the main spindle 30 to the back spindle 50. Therefore, it is possible to machine works W having varied lengths from a short length to a long length, entirely without excluding both end surfaces thereof, into complex shapes.</li><li>(2) It is possible to machine the work W1 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50 without stopping the lathe.</li><li>(3) The tool spindle 100 grips one tool 101. Accordingly, unlike the turret 40 in the example, no interference occurs between adjacent tools 41.</li><li>(4) The work W2 gripped by the main spindle 30 and the work W2 gripped by the back spindle 50 can be both machined by the same tool 101. Therefore, there is no need of preparing a same kind of tool 101 in a plural number.</li><li>(5) The lathe comprises the tool magazine 70. Accordingly, it is possible to prepare plural kinds of tools 101 in advance.</li><li>(6) The lathe comprises the tool exchange mechanism 80. Accordingly, it is possible to exchange the tools 101 without stopping the lathe.</li><li>(7) The lathe can move the tool spindle 100 in the Y1-axis direction. Accordingly, it is possible to freely move the tool 101 three-dimensionally. Therefore, complex machining such as machining for drilling an eccentric hole in the work W, machining for forming an angled hole, hob machining, etc. becomes available.</li><li>(8) The lathe comprises the tool rest 60. Therefore, the lathe can prepare a tool to be used next on the tool rest 60, while, for example, applying machining by using the tool 101 on the tool spindle 100. Crosswise, the lathe can prepare a tool to be used next on the tool spindle 100, while, for example, applying machining by using the tool 61 on the tool rest 60. This shortens the idle time for exchanging tools.</li><li>(9) The lathe can apply machining to the work W by simultaneously using the tool 101 and the tool 61. Accordingly, the machining time can be shortened.</li><li>(10) Since machining can be applied by simultaneously using the tool 101 and the tool 61, one can be used for rough machining and the other can be used for finishing machining.</li><li>(11) Since machining can be applied by simultaneously using the tool 101 and the tool 61, different portions of the work W can be machined simultaneously.</li><li>(12) Since the back spindle 50 has a hole formed therein, through which the work W penetrates, a lengthy work W can be attached thereto. Due to this, there is no need of upsizing the lathe.</li></ol>

0155The present invention is not limited to the above-described embodiment, but may be variously modified within the scope of the claims. Modifications include the followings. <ol id="ol0005" compact="compact" ol-style=""><li>(i) According to the above-described embodiments, the X1- and X2-axis directions, the Z1-, Z2-, Z3-, and Z4-axis directions, and the Y1- and Y2-axis directions are perpendicular to one another. However, they may not be perpendicular to each other as long as they are different directions.</li><li>(ii) According to the above-described embodiments, the X1-axis direction and the X2-axis direction are parallel with each other, and the Y1-axis direction and the Y2-axis direction are parallel with each other. However, they may not be parallel. For example, the turret 40 or the tool spindle 100 may be structured to obliquely fall from an upper position to a lower position to move the tool 41 or the tool 101 forward. Furthermore, symmetrically with the turret 40 or the tool spindle 100, the tool rest 60 may be structured to obliquely fall from an upper position to a lower position to move the tool 61 forward.</li><li>(iii) Machining may be applied to the work W by fixing the position of the tool spindle 100, or the tool rest 60 and moving the main spindle 30 or the back spindle 50. Crosswise, machining may be applied to the work W by fixing the position of the main spindle 30 or the back spindle 50 and moving the tool spindle 100, or the tool rest 60.</li></ol>

0156Various embodiments and changes may be made within the scope of the invention which is defined by the appended claims. The above-described embodiment is intended to illustrate the present invention, not to limit the scope of the present invention.