Machine tool and machining method

A machine tool includes a main spindle that rotates while holding a workpiece, a mover that moves a cutting tool including a linear cutting blade that cuts the workpiece, with respect to the workpiece in a moving direction including at least a Z-direction parallel or substantially parallel with the axis of the main spindle and a Y-direction perpendicular or substantially perpendicular to both the Z-direction and an X-direction determining the amount of cutting of the workpiece, a holder that holds the cutting tool in a state in which the direction of the linear cutting blade is inclined with respect to the Z-direction by a predetermined angle when seen from the X-direction, and an angle adjuster that changes the edge angle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a machine tool that cuts a workpiece and a machining method.

2. Description of the Related Art

A lathe, which is a machine tool, holds a workpiece to be machined, on a rotating shaft (spindle) and performs cutting or the like on the workpiece using a cutting tool while rotating the workpiece. As a machining method using a lathe, for example, there is known a machining method of cutting a workpiece while feeding a cutting tool in a tangential direction of the workpiece (a direction crossing the rotation axis (see Japanese Patent No. 3984052).

In this machining method, the edge of the cutting tool is positioned so as to be inclined with respect to the direction of a generating line of the cut portion of the workpiece by a predetermined angle. As the predetermined angle is reduced, the edge of the cutting tool comes closer to a state in which the edge is along the generating line of the workpiece. Accordingly, the cutting range in the direction of the generating line is widened, resulting in a reduction in the machining time. However, if a small-diameter workpiece, for example, is cut over a wide range thereof, the load on the workpiece (the cutting force applied to the workpiece) is increased. Thus, chattering vibration, bending, or the like may occur in the workpiece. For this reason, it is necessary to adjust the direction of the edge (edge angle) to reduce the load on the workpiece. A conventional machine tool is provided with multiple types of cutting tools or holders having different edge angles with respect to a generating line of a workpiece, and the operator replaces the cutting tool or holder with another to change the direction of the edge.

However, the method of replacing the cutting tool or holder has a problem that the operator has to do troublesome work such as demounting and mounting of the cutting tool or the like and this work takes time.

SUMMARY OF THE INVENTION

In view of the foregoing, preferred embodiments of the present invention provide a machine tool and a machining method that are able to easily change a direction of an edge of a cutting tool in a short time.

A machine tool according to a preferred embodiment of the present invention includes a main spindle that rotates while holding a workpiece, a mover that moves a cutting tool with respect to the workpiece in a moving direction including at least a Z-direction parallel or substantially parallel with an axis of the main spindle and a Y-direction perpendicular or substantially perpendicular to both the Z-direction and an X-direction, the X-direction being perpendicular or substantially perpendicular to the Z-direction and determining the amount of cutting of the workpiece, the cutting tool including a linear cutting blade that cuts the workpiece, a holder that holds the cutting tool in a state in which a direction of the linear cutting blade is inclined with respect to the Z-direction by a predetermined angle when seen from the X-direction, and an angle adjuster that changes the predetermined angle.

The moving direction may be a direction obtained by combining the Z-direction and the Y-direction. The angle adjuster may include a rotor that is able to rotate about an axis parallel or substantially parallel with the X-direction, and the holder may be mounted on the rotor. The rotor may be integral with the holder. The machine tool may further include a driver that rotates the rotor. The rotor and a support that supports the rotor may be provided with marks indicating the predetermined angle. The machine tool may further include a controller that controls movement of the mover on the basis of information about the predetermined angle and the workpiece.

A machining method according to a preferred embodiment of the present invention is a method for machining a workpiece rotating while being held by a main spindle. The method includes moving a cutting tool with respect to the workpiece in a moving direction including at least a Z-direction parallel or substantially parallel with an axis of the main spindle and a Y-direction perpendicular or substantially perpendicular to both the Z-direction and an X-direction, the X-direction being perpendicular or substantially perpendicular to the Z-direction and determining the amount of cutting of the workpiece, the cutting tool including a linear cutting blade that cuts the workpiece, holding the cutting tool in a state in which a direction of the linear cutting blade is inclined with respect to the Z-direction by a predetermined angle when seen from the X-direction, and changing the predetermined angle.

According to various preferred embodiments of the present invention, a cutting tool is held by the holder in a state in which the direction of the linear cutting blade is inclined with respect to the Z direction by the predetermined angle when seen from the X-direction, and the operator is able to change the predetermined angle using the angle adjuster. Thus, the operator is able to adjust the predetermined angle without having to replace the cutting tool or holder. As a result, the operator is able to easily change the direction of the edge of the cutting tool in a short time.

If the moving direction is a direction obtained by combining the Z direction and the Y direction, it is possible to cut a wide range of the workpiece in the Z direction by feeding the cutting tool in the combined direction and thus to reduce the machining time. If the angle adjuster includes the rotor that is able to rotate about the axis parallel or substantially parallel with the X-direction and if the holder is mounted on the rotor, the operator is able to rotate the cutting tool along with the holder by rotating the rotor. Thus, the operator is able to easily adjust the predetermined angle. If the rotor is integral with the holder, the length to the edge (overhang) is able to be reduced. If the machine tool further includes the driver that rotates the rotor, the predetermined angle is able to be automatically adjusted on the basis of the drive of the driver. If the rotor and the support that supports the rotor are provided with the marks indicating the predetermined angle, the operator is able to adjust the rotation of the rotor using the marks and thus is able to easily adjust the predetermined angle. If the machine tool further includes the controller that controls the movement of the mover on the basis of information about the predetermined angle and workpiece, it is possible to perform optimum machining such that the machining accuracy is improved without reducing the machining efficiency.

According to a machining method of a preferred embodiment of the present invention, the cutting tool is held such that the direction of the linear cutting blade is inclined with respect to the Z direction by the predetermined angle when seen from the X-direction, and the operator is able to change the predetermined angle. Thus, the operator is able to easily change the direction of the edge of the cutting tool in a short time in accordance with the machining condition of the workpiece and to accurately machine the workpiece.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited thereto. To clarify the preferred embodiments of the present invention, the drawings are scaled, for example, partially enlarged or highlighted, as necessary. In the drawings, directions are shown by an XYZ coordinate system. In the XYZ coordinate system, a plane parallel or substantially parallel with the horizontal plane is defined as a YZ plane; the direction of the rotation axis of a main spindle7(a counter spindle8) in the YZ plane is defined as a Z-direction; the direction perpendicular or substantially perpendicular to the Z-direction is defined as a Y-direction; the direction perpendicular or substantially perpendicular to the YZ plane is defined as an X-direction; and the X-axis represents a direction that is perpendicular or substantially perpendicular to the Z-direction and that determines the amount of cutting of a workpiece. In the drawings, directions shown by arrows are the positive directions of the X-, Y-, and Z-directions, and opposite directions are the negative directions thereof. Other preferred embodiments of the present invention also provide methods for machining a workpiece rotating while being held by a main spindle. A method according to a preferred embodiment of the present invention includes moving a cutting tool with respect to the workpiece in a moving direction including at least a Z-direction parallel or substantially parallel with an axis of the main spindle and a Y-direction perpendicular or substantially perpendicular to both the Z-direction and an X-direction, the X-direction being perpendicular or substantially perpendicular to the Z-direction and determining the amount of cutting of the workpiece, the cutting tool including a linear cutting blade that cuts the workpiece, holding the cutting tool in a state in which a direction of the linear cutting blade is inclined with respect to the Z-direction by a predetermined angle when seen from the X-direction, and changing the predetermined angle.

First Preferred Embodiment

A machine tool100according to a first preferred embodiment of the present invention will be described with reference to the drawings.FIGS. 1A and 1Bare diagrams showing an example of a machine tool100of the first preferred embodiment of the present invention, in whichFIG. 1Ais a side view; andFIG. 1Bis a front view. The machine tool100shown inFIGS. 1A and 1Bis a lathe. InFIGS. 1A and 1B, the front side of the machine tool100is located on the positive Y-side, and the back side thereof is located on the negative Y-side. The lateral sides of the machine tool100are located on the positive and negative Z-sides, and the Z-direction represents the horizontal direction of the machine tool100.

As shown inFIGS. 1A and 1B, the machine tool100includes a base1. The base1is provided with a headstock2and a tailstock4. The headstock2rotatably supports a main spindle7through a bearing or the like (not shown). While the headstock2is fixed to the base1, it may be movable in the Z, X, Y, or other directions by driving a motor or the like. The main spindle7includes a chuck driver9on the positive Z-side end thereof. The chuck driver9causes multiple grasping claws9ato move in the radial direction of the main spindle7and to hold a workpiece W. While, inFIGS. 1A and 1B, the workpiece W is grasped using three grasping claws9aequally spaced around the rotation axis of the main spindle7, other configurations may be used. The grasping claws9amay be in any number or shape as long as they are able to hold the workpiece W. The workpiece W grasped by the grasping claws9apreferably includes a cylindrical surface Wa (e.g., a cylindrical shape).

The negative Z-side end of the main spindle7protrudes from the headstock2in the negative Z-direction and includes a pulley11mounted thereon. A belt13extends between the pulley11and the rotating shaft of a motor12disposed in the base1. Thus, the main spindle7is rotationally driven by the motor12through the belt13. The rev or the like of the motor12is controlled in accordance with an instruction from a controller (not shown). The motor12is, for example, a motor including a torque controller. The main spindle7need not be driven by the motor12or belt13; the drive of the motor12may be transmitted to the main spindle7through a gear train or the like, or the motor12may directly rotate the main spindle7.

The tailstock4is preferably movable along a Z-direction guide3disposed on the base1. The tailstock4rotatably supports the counter spindle8through a bearing or the like (not shown). The directions of the rotation axes of the main spindle7and counter spindle8are both the Z-direction. The tailstock4includes a center10mounted on the negative Z-side end thereof. The counter spindle8may be fixed to the tailstock4and used as a dead center.

As shown by a dot-and-dash line inFIG. 1B, if the workpiece W has a long length (is long in the Z-direction), the positive Z-side end of the workpiece W is held by the center10of the tailstock4. Thus, the long workpiece is rotated while being sandwiched between the main spindle7and counter spindle8. As a result, the workpiece W is able to be rotated stably during cutting. If the workpiece W has a short length (is short in the Z-direction), it is rotated while being held by only the grasping claws9aof the main spindle7. In this case, the tailstock4need not be used.

As shown inFIGS. 1A and 1B, a Z-direction guide5is disposed on the base1in the Z-direction. A Z-direction guide5A similar to the Z-direction guide5is disposed in a negative X position of the Z-direction guide5in the Z-direction. The Z direction guides5and5A are provided with Z-axis slides17and17A, respectively, that are able to move along the Z-direction guides5and5A in the Z-direction. As shown inFIG. 1B, the Z-axis slide17is moved in the Z-direction by the drive of a Z-direction drive system (mover) M1and held in position. The Z direction drive system M1is, for example, an electric motor or hydraulic system. The Z-axis slide17A is provided with a drive system similar to the Z-direction drive system M1, and is moved in the Z-direction by the drive of this drive system and held in position. The configuration of the drive system of the Z-axis slide17A may be the same as or different from that of the Z-direction drive system M1.

The Z-axis slides17and17A have X-direction guides18and18A, respectively, thereon. The Z-axis slides17and17A are also provided with X-axis slides15and15A, respectively, that are able to be moved along the X-direction guides18and18A. The X-axis slide15is moved in the X-direction by the drive of an X-direction drive system (mover) M2and held in position. The X-direction drive system M2is, for example, an electric motor or hydraulic system. The X-axis slide15A is provided with a drive system similar to the X-direction drive system M2, and is moved in the X-direction by the drive of this drive system and held in position. The configuration of the drive system of the X-axis slide15A may be the same as or different from that of the X-direction drive system M2.

The X-axis slides15and15A include Y-direction guides16and16A, respectively, thereon. The X-axis slides15and15A are also provided with tool post drivers21and21A, respectively, that are able to be moved along the Y-direction guides16and16A. The tool post driver21is moved in the Y-direction by the drive of a Y-direction drive system (mover) M3and held in position. The Y-direction drive system M3is, for example, an electric motor or hydraulic system. The tool post driver21A is provided with a drive system similar to the Y-direction drive system M3, and is moved in the Y-direction by the drive of this drive system and held in position. The configuration of the drive system of the tool post driver21A may be the same as or different from that of the Y-direction drive system M3. The Z-direction drive system M1, X-direction drive system M2, and Y-direction drive system M3are controlled by a controller CONT.

The tool post drivers21and21A include rotational drivers, such as motors. The tool post driver21includes a first turret23mounted thereon. The first turret23is able to be rotated using the Z-direction as the axis by the drive of the rotational driver. Similarly, the tool post driver21A includes a second turret23A mounted thereon. The second turret23A is able to be rotated using the Z-direction as the axis by the drive of the rotational driver. The first turret23is positioned over the workpiece W (on the positive X-side thereof); the second turret23A is positioned under the workpiece W (on the negative X-side thereof). That is, the first and second turrets23and23A are positioned so as to sandwich the workpiece W.

The first and second turrets23and23A include, on the circumferential surfaces thereof, multiple holders that hold cutting tools T. The cutting tools T are held in all or some of the holders. Accordingly, a desired cutting tool T is selected by rotating the first turret23or second turret23A. The cutting tools T held in the holders of the first and second turrets23and23A are able to be replaced on a holder basis. The cutting tools T include cutting tools to cut the workpiece W, as well as rotary tools, such as a drill and an end mill.

The first turret23includes a tool head24defining and functioning as one of the holders thereon, and the second turret23A includes a tool head24A defining and functioning as one of the holders thereon. The configurations of the tool heads24and24A may be the same or different. Note that the second turret23A need not be provided with the tool head24A.

A cutting tool T1is mounted over the tool head24with a holder25(seeFIG. 2) therebetween. On the other hand, a cutting tool T is mounted over the tool head24A with a holder (not shown) therebetween. The cutting tool T may be the same as or different from the cutting tool T1mounted over the tool head24.

While, in the machine tool100shown inFIGS. 1A and 1B, the cutting tools T and T1are positioned on the positive-X and negative X-sides of the workpiece W so as to sandwich the workpiece W, a cutting tool may be positioned on either side. Also, while the cutting tools T and T1are positioned in the X-direction of the workpiece W (the vertical direction), these cutting tools may be located in the Y-direction of the workpiece W. Also, when cutting the workpiece W, the cutting tools T and T1may be used in any manner under the control of a controller (not shown). For example, one of the cutting tools may be used, or both may be used alternately or simultaneously.

While, inFIGS. 1A and 1B, the first and second turrets23and23A are used as tool rests, other types of tool rests may be used. For example, comb-shaped tool posts may be used. If comb-shaped tool posts are used, cutting tools T are held on the teeth of each comb-shaped tool post, and one of the cutting tools T is selected by moving the comb-shaped tool post in the direction in which the teeth are arranged.

FIG. 2is an enlarged perspective view of the main spindle7and first turret23, which corresponds to the workpiece W. As shown inFIG. 2, the tool head24is detachably mounted on the negative X-side surface23aof the first turret23. A holder25is mounted over the negative X-side of the tool head24with a rotor26(to be discussed later) therebetween. The holder25holds the cutting tool T1. The cutting tool T1is set so that a linear cutting blade Th thereof is along the YZ plane.

The cutting tool T1is positioned in the X-direction by driving the X-direction drive system M2. Thus, the amount of cutting of the workpiece W is determined. Also, by driving the Z-direction drive system M1, X-direction drive system M2, and Y-direction drive system M3, the cutting tool T1is able to be moved relative to the workpiece W along with the first turret23and tool head24in one of the Z-, X-, and Y-directions or in a direction obtained by combining two or more of these directions.

FIGS. 3A and 3Bare diagrams showing the negative X-side configuration of the tool head24.

As shown inFIGS. 3A and 3B, the tool head24includes a cylindrical opening24aon the negative X-side thereof, and the rotor26(to be discussed later) is inserted in the opening24aof the tool head24.

The tool head24also has a protrusion24bon the negative Z-side end surface thereof. The protrusion24bprotrudes in the negative Z-direction and includes a slit24d. The slit24dlinearly extends from the front end of the protrusion24bin the negative Z-direction. The slit24dcuts across the protrusion24b, which leads to the opening24a, as well as extends to a portion on the positive Z-side of the opening24a, and the protrusion24bis divided into two portions. In the present preferred embodiment, for example, the tool head24is elastically deformable so that the opening24ais narrowed when a force is applied in the direction in which the divided portions of the protrusion24bcome close to each other (e.g., in the Y-direction). The divided portions of the protrusion24bare fastened by bolts24c, for example. By tightening the bolts24c, a force is applied so that the divided portions of the protrusion24bcome close to each other in the Y-direction. Thus, the inner wall of the opening24afastens the rotor26. Also, by loosening the bolts24c, the force applied to the divided portions of the protrusion24bis released, thus loosening the fastened rotor26. In this case, the rotor26is allowed to rotate about a rotation axis AX parallel or substantially parallel with the X-direction.

The rotor26preferably has a cylindrical shape, for example. It is inserted in the opening24a, as well as supported by the tool head24. As seen above, the tool head24is a support member that supports the rotor26. The rotor26includes thereon a guide26gto insert the holder25.

The guide26gpreferably has a straight line shape, for example. The guide26gincludes a holder contact surface26hon the end thereof in the length direction (i.e., on the negative Y-side end inFIG. 3A). When the holder25contacts the holder contact surface26h, the holder25is positioned. The holder contact surface26hdefines and functions as a surface that receives the cutting force of the cutting tool T1. The size (width) of the guide26gin the short direction is set in accordance with the size of the holder25. The holder25is fixed to the rotor26by a fixing member (not shown). By fixing the holder25to the guide26g, the direction of the linear cutting blade Th of the cutting tool T1with respect to the rotor26is fixed to one direction. By rotating the rotor26about the rotation axis AX in this state, the holder25and cutting tool T1are rotated integrally with the rotor26, thus changing the direction of the linear cutting blade Th.

The rotor26includes marks26aand26bon the negative X-side end surface thereof. The marks26aand26bare preferably isosceles triangles, and the peaks thereof are oriented to, for example, the outer circumference of the rotor26. The tool head24includes a mark24eon the negative X-side surface thereof. The mark26epreferably is an isosceles triangle, and the peak thereof is oriented to, for example, the rotor26. The mark26eis disposed such that when rotating the rotor26about the rotation axis AX, the peak of the mark26aor26bcorresponds to the peak of the mark24eon the tool head24. The marks26aand26bmay be scale divisions or the like.

For example, with the holder25inserted in the rotor26, the mark26aindicates the rotation position of the rotor26such that the linear cutting blade Th is inclined with respect to the Z-direction by an angle α (e.g., about 45°) when seen from the X-direction. Hereafter, the angle (predetermined angle) by which the linear cutting blade Th is inclined with respect to the Z-direction when seen from the X-direction X will be referred to as the “edge angle.”FIG. 3Ashows a state in which the mark26aand mark24ecorrespond to each other. As shown inFIG. 3A, by adjusting the rotation position of the rotor26so that the peaks of the mark26aand mark24ecorrespond to each other, the edge angle is able to be set to α.

The mark26bindicates the rotation position of the rotor26such that the edge angle is β (e.g., about 60°).FIG. 3Bshows a state in which the mark26band mark24ecorrespond to each other. As shown inFIG. 3B, by adjusting the rotation position of the rotor26so that the peaks of the mark26band mark24ecorrespond to each other, the edge angle is able to be set to β. A mark corresponding to an edge angle different from α and β may be additionally provided.

The operator is able to change the edge angle to a predetermined angle (e.g., angle α, angle β) by rotating the rotor26about the rotation axis AX with the bolts24cloosened so that the mark26a, mark26b, or the like and the mark24ecorrespond to each other. Thus, the operator is able to efficiently change the direction of the linear cutting blade Th to a predetermined direction. As seen above, the rotor26and the tool head24supporting the rotor26are disposed as an angle adjuster29that is able to change the edge angle.

Next, the operation of the machine tool100thus configured will be described. First, the operator causes the main spindle7to hold the workpiece W to be machined. After the workpiece W is grasped, the operator rotates the workpiece W by driving the motor12and thus rotating the main spindle7. Note that when grasping the workpiece W using both the main spindle7and counter spindle8, the operator rotates the main spindle7and counter spindle8synchronously. The rev of the workpiece W is set in accordance with the machining process as appropriate.

Then, the operator selects the cutting tool T1by rotating the first turret23. Note that before selecting the cutting tool T1, the operator inserts the rotor26into the opening24ain the tool head24of the first turret23. The operator then inserts the cutting tool T1into the holder25and inserts the holder25into the rotor26(guide26g) of the tool head24. The holder25is fixed to the rotor26by a bolt or the like (not shown). Thus, the linear cutting blade Th is disposed in a direction parallel or substantially parallel with the YZ plane and so as to be inclined with respect to the Z-direction by a predetermined angle when seen from the X-direction. The operator then changes the edge angle by rotating the rotor26. At this time, the operator is able to easily set the edge angle by causing the mark26a,26b, or the like provided on the rotor26and the mark24eprovided on the tool head24to correspond to each other.

The operator then adjusts the position of the cutting tool T1in the X-direction. In this adjustment, the tool post driver21is moved in the X-direction by the X-direction drive system M2so that the linear cutting blade Th of the cutting tool T1corresponds to the cylindrical surface Wa of the workpiece W. The position of the linear cutting blade Th in the X-direction determines the amount of cutting of the cylindrical surface Wa of the workpiece W. The amount of cutting may be set to a predetermined value by the controller CONT, or may be set by the operator manually.

When the rotation of the workpiece W is stabilized, the operator cuts the cylindrical surface Wa of the workpiece W using the cutting tool T1. In the cutting process, the XYZ coordinate position to which the linear cutting blade Th of the cutting tool T1is moved is set, for example, by the movement of the Z-axis slide17in the Z-direction and the movement of the tool head24in the Y-direction. These movements are made on the basis of the drive of the Z-direction drive system M1and Y-direction drive system M3under the control of the controller CONT.

When the rotor26is rotated about the rotation axis AX, the posture of the cutting tool T1is changed. That is, the rotation of the rotor26changes the position of the edge of the linear cutting blade Th in the Y and Z-directions. The change in the position of the linear cutting blade Th vary with the shape or size of the cutting tool T1(linear cutting blade Th), the rotation position of the rotor26, or the like. For this reason, the operator may obtain a change in the position of the linear cutting blade Th caused by the rotation of the rotor26by an experiment, simulation, or the like in advance and then obtain the position of the linear cutting blade Th for each of cutting tools T1to be used or for each of the rotation positions of the rotor26. In this case, by correcting the drive of the Z-direction drive system M1or Y-direction drive system M3, it is possible to avoid, for example, a shift in the cutting start position of the cutting tool T1, or the like.

In an example of the present preferred embodiment, the workpiece W is cut by moving the linear cutting blade Th of the cutting tool T1in the Y-direction, which is a tangential direction of the cylindrical surface Wa of the workpiece W. This movement of the cutting tool T1in the Y-direction is made on the basis of, for example, machining information (machining recipe) preset in a storage, memory or the like of the controller (not shown). Note that this movement of the cutting tool T1may be made by the operator manually.

FIG. 4Ashows the operation of the cutting tool T1(linear cutting blade Th) on the workpiece W seen in the negative X-direction in a case in which the edge angle is set to a (e.g., about 45′).FIG. 4Bshows the operation of the cutting tool T1(linear cutting blade Th) seen form the Z-direction.FIG. 4Cshows the operation of the cutting tool T1(linear cutting blade Th) on the workpiece W seen in the negative X-direction in a case in which the edge angle is set to β (e.g., about 60°). In any of the cases shown inFIGS. 4A and 4C, when the linear cutting blade Th of the cutting tool T1moves from the negative Y-side to the positive Y-side with respect to a generating line (axis) D in the Z-direction on the cylindrical surface Wa of the workpiece W, the positive Z-side of the linear cutting blade Th contacts the workpiece W first.

Next, the workpiece W is cut by moving the linear cutting blade Th in a direction (moving direction) P1or P2obtained by combining the positive Y-direction and negative Z-direction. As shown inFIGS. 4A to 4C, this moving direction is a track along a tangent plane to the cylindrical surface Wa of the workpiece W. First, a positive Z-side first end Th1of the linear cutting blade Th contacts and cuts the cylindrical surface Wa. Then, the linear cutting blade Th moves along the cylindrical surface Wa in the positive Y-direction and the negative Z-direction (the direction P1or P2). Thus, the cut portion of the workpiece W gradually shifts from the first end Th1to a second end Th2in the negative Z-direction. As seen above, the linear cutting blade Th moves in the direction P1or P2, whereas the cut portion of the cylindrical surface Wa of the workpiece W moves in the Z-direction.

When the second end Th2of the linear cutting blade Th leaves the generating line D, the cutting of the cylindrical surface Wa is complete. While the cylindrical surface Wa is cut using all the portions of the linear cutting blade Th from the first end Th1to second end Th2, as seen above, the cylindrical surface Wa may be cut using some portions of the linear cutting blade Th.

In this cutting process, in a first case in which the edge angle is set to a small angle, for example, as shown inFIG. 4A(e.g., when the edge angle is set to α), the linear cutting blade Th comes close to the generating line D of the workpiece W compared to in a second case in which the edge angle is set to a large angle, for example, as shown inFIG. 4C(e.g., when the edge angle is set to β).

In the first case, as shown inFIG. 4A, the length L in the generating line D is cut by moving the linear cutting blade Th in the direction P1. The length L is the sum of a length A1(cos α of the width of the linear cutting blade Th) obtained by projecting the linear cutting blade Th on the generating line D and a length B1of the generating line D in the Z-direction that the linear cutting blade Th cuts while moving in the direction P1. In the second case, a length L is cut as well by moving the linear cutting blade Th in the direction P2. The length L here is the sum of a length A2(cos β of the length of Th) obtained by projecting the linear cutting blade Th on the generating line D and a length B2of the generating line D in the Z-direction that the linear cutting blade Th cuts while moving in the direction P2.

As shown inFIGS. 4A-4C, L=A1+B1, L=A2+B2, A1>A2, and B1<B2. Specifically, assuming that the same length L is cut and that the per-unit time feed of the cutting tool T1is the same, the workpiece is able to be machined in a shorter time and higher surface accuracy (lower surface roughness) is obtained in the first case than in the second case. Machining the workpiece W in the second case in the same time as that in the first case requires increasing the feed and therefore reduces the surface accuracy (increases the surface roughness). For example, when a small-diameter workpiece or a low-rigidity workpiece is machined or when a portion distant from the grasping claws9a, of the workpiece W (a portion having low grasping rigidity) is machined and when the edge angle is small as in the first case, the load on the workpiece W (the cutting force applied to the workpiece) is increased and thus chattering vibration, bending, or the like is more likely to occur in the workpiece W. In the second case, on the other hand, the edge angle is smaller than that in the first case and therefore if the same feed as that in the first case is set, the load on the workpiece W is reduced and thus chattering vibration, bending, or the like is less likely to occur in the workpiece W.

Accordingly, for example, when a large-diameter workpiece or a high-rigidity workpiece is machined or when a portion close to the grasping claws9a, of the workpiece W (a portion having high grasping rigidity) is machined, the edge angle is set to a small angle (e.g., a). Thus, the cutting range of the linear cutting blade Th in the Z-direction is increased, allowing for a reduction in machining time and an improvement in surface accuracy.

On the other hand, when a small-diameter workpiece or a low-rigidity workpiece is machined or when a portion having low grasping rigidity, of the workpiece W is machined, the edge angle is set to a large angle (e.g., β) without changing the feed. Thus, the cutting range of the linear cutting blade Th in the Z-direction is reduced, thus reducing the load on the workpiece W and making chattering vibration, bending, or the like less likely to occur in the workpiece W.

As seen above, when setting (changing) the edge angle, the operator only has to rotate the rotor26so that the marks26aand26bcorrespond to the mark24e, and thus is easily able to change the edge angle (the direction of the linear cutting blade Th).

While, in the present preferred embodiment, the cutting tool T1of the first turret23preferably is used when cutting the workpiece W, the cutting tool T (seeFIGS. 1A and 1B) of the second turret23A may be additionally used. In this case, the cutting tool T of the second turret23A may be caused to move on a track similar to that of the cutting tool T1on the negative X-side of the workpiece W and to cut the cylindrical surface Wa. When cutting the cylindrical surface Wa using both the cutting tools T1and T, the cutting tools may cut the same orbital portion of the cylindrical surface Wa in different amounts, or may cut different portions of the cylindrical surface Wa. When the cutting of the workpiece W is complete, the operator causes the grasping claws9ato release the workpiece W and takes out the workpiece W.

As seen above, the machine tool100of the present preferred embodiment is able to change the edge angle using the angle adjuster29with the cutting tool T1held by the holder25so that the direction of the linear cutting blade Th is inclined with respect to the Z-direction by a predetermined angle when seen from the X-direction. Thus, the operator is able to adjust the edge angle without having to replace the cutting tool T1or holder25. As a result, the operator is able to easily change the direction of the edge of the cutting tool T1in a short time.

Second Preferred Embodiment

A machine tool200according to a second preferred embodiment of the present invention will be described.

FIG. 5shows an example of a tool head124of the machine tool200of the second preferred embodiment seen in the positive X-direction. Elements not shown inFIG. 5are similar to those of the machine tool100shown inFIGS. 1A and 1B. Also, inFIG. 5, elements identical or equivalent to those in the first preferred embodiment are given the same reference signs, and the description thereof will be omitted or simplified. An angle adjuster129of the second preferred embodiment is configured differently from the angle adjuster of the first preferred embodiment (where the operator rotates the rotor26). As shown inFIG. 5, the angle adjuster129includes the tool head124, a rotor26, and a driver30. The driver30rotates the rotor26. The driver30is controlled by, for example, a controller CONT.

FIG. 6Ais a diagram of the inside of a first turret23(a second turret23A) seen in the positive Z-direction, andFIG. 6Bis a sectional view taken along line A-A inFIG. 6A. As shown inFIGS. 6A and 6B, the driver30includes a motor31, a worm gear32, a transmission shaft33, and bevel gears34and35.

The motor31is disposed on the positive Z-side of the first turret23and is mounted on, for example, a tool post driver21. The motor31includes an output shaft31aparallel or substantially parallel with the Y-direction. The output shaft31ais rotated about a rotation axis parallel or substantially parallel with the Y-direction. The worm gear32includes a screw gear32amounted on the output shaft31aand a helical gear32bmounted on a transmission shaft33. The worm gear32transmits the rotation of the output shaft31ato the transmission shaft33.

The transmission shaft33is supported by, for example, bearings33aand33bsuch that it can be rotated about a rotation axis parallel or substantially parallel with the Z-direction. The transmission shaft33includes the helical gear32bmounted on the positive Z-side end thereof. The transmission shaft33also includes the bevel gear34mounted on the negative Z-side end thereof. The bevel gear34is engaged with the bevel gear35. The bevel gear35is mounted on a shaft122. The bevel gears34and35transmit the rotation of the transmission shaft33to the shaft122.

The shaft122has a rotation axis AX2parallel or substantially parallel with the X-direction and is rotated about the rotation axis AX2by a drive force from the driver30. The shaft122is rotatably supported by, for example, bearings36aand36b. The shaft122includes a gear123aon the negative X-side end thereof, and the gear123ais rotated about an X axis integrally with the shaft122.

The rotor26includes a gear123bon the outer circumferential surface thereof. The rotation axis of the gear123bis identical to the rotation axis AX1of the rotor26. Teeth parallel or substantially parallel with the X-direction are arranged on the gear123balong the cylindrical surface of the rotor26. The gear123bis engaged with the gear123aand is rotated about the rotation axis AX1when the gear123ais rotated. Rotating the shaft122rotates the gear123a, which then applies a rotating force to the gear123b. This force rotates the rotor26about the rotation axis AX1. A shaft26aof the rotor26is supported by a slide bearing125. The inner circumferential surface of the slide bearing125supports the shaft26awhile receiving the radial force (the force in the radial direction) of the shaft26a; the lower edge (the negative X-side end surface) of the slide bearing125supports the rotor26while receiving the thrust force (the force in the X-direction) of the rotor26.

When the driver30drives the rotor26and thus the rotor26is rotated about the rotation axis AX1, the edge angle of a linear cutting blade Th of a cutting tool T1mounted on the holder25is changed. While the driver30stops driving the rotor26, the changed edge angle is maintained. As seen above, in the case of the angle adjuster129, the rotating position of the rotor26is set in accordance with whether the driver30is driving the rotor26, and the edge angle of the linear cutting blade Th of the cutting tool T1mounted on the holder25is set on the basis of the set rotating position of the rotor26.

As seen above, according to the second preferred embodiment, the machine tool200includes the driver30that rotates the rotor26. Thus, it is able to automatically adjust the edge angle by causing the driver30to drive the rotor26. As a result, the operator is able to adjust the edge angle without having to replace the cutting tool T1or holder25. That is, the operator is able to easily change the direction of the linear cutting blade Th of the cutting tool T1in a short time.

In the second preferred embodiment, the driver30is able to be automatically controlled under the control of the controller CONT. Thus, for example, when the diameter, rigidity, or grasping rigidity of the workpiece W is changed with respect to the Z-direction, the edge angle (the direction of the linear cutting blade Th) is able to be automatically changed in accordance with such a change. For example, when machining a portion close to the grasping claws9a, of the workpiece W, the operator is able to cause the machine tool200to machine the workpiece W in a short time, by setting the edge angle to a small angle and setting the feed speed to a high speed. On the other hand, when machining a portion distant from the grasping claws9a, of the workpiece W (the central portion of the workpiece W in the Z-direction, etc.), the operator is able to cause the machine tool200to machine the workpiece W in such a manner that chattering vibration or the bending of the workpiece W is significantly reduced or prevented, and the cylindricity or surface roughness of the workpiece W is not reduced, by setting the edge angle to a large angle and setting the feed speed to a low speed. Thus, the operator is able to efficiently perform high-quality machining. Note that the edge angle may be changed in synchronization with the feed of the cutting tool T1in the Y-direction or the rotation of the main spindle7. Further, there may be a machine tool that includes a sensor to detect chattering vibration or the bending of the workpiece W and changes the edge angle in accordance with the detection result of the sensor.

While the preferred embodiments have been described above, the present invention is not limited thereto. Various changes can be made to the preferred embodiments without departing from the spirit and scope of the present invention.

For example, while, in the above preferred embodiments, the rotor26is disposed independently of the holder25and the holder25is inserted in the rotor26, the holder25and rotor26may be disposed integrally.

While, in the above preferred embodiments, the workpiece W having the cylindrical surface Wa is cut, a workpiece W2having an inclined surface Wb such as a tapered surface or spherical surface may be cut.FIGS. 7A and 7Binclude diagrams showing an example of a tool head224of a modification, in whichFIG. 7Ais a perspective view; andFIG. 7Bis a diagram when seen from a direction Q inFIG. 7A.FIG. 8is a diagram of a first turret23seen in the negative Y-direction.

The tool head224includes a tool disposition surface224fhaving a cutting tool T1disposed thereon. The tool disposition surface224fis inclined with respect to a surface23a(a YZ plane) of the first turret23and is oriented toward a main spindle7(seeFIG. 8). The cutting tool T1is held by the tool head224with a rotor226therebetween. The rotor226includes a rotating portion226aand a holder226b. The rotating portion226aand holder226bare preferably integral. The rotating portion226apreferably has a cylindrical shape and is inserted in an opening (not shown) in the tool disposition surface224f. The rotating portion226ais rotatable about a rotation axis AX3. The opening preferably has a cylindrical shape and has a larger diameter than the rotating portion226a. The rotating portion226ais mounted over the tool disposition surface224fwith a lock sleeve227therebetween. The lock sleeve227includes a bolt228and a press-fit portion (not shown). The press-fit portion is press-fitted between the rotating portion226aand opening (not shown). The press-fit portion regulates the rotation of the rotating portion226a. By tightening the bolt228, the rotation position of the rotating portion226ais held by the lock sleeve227. Also, by loosening the tightened bolt228and thus loosening the press-fitted lock sleeve227, the rotor226can be rotated about the rotation axis AX3. The holder226bholds the cutting tool T1. As shown inFIG. 7B, the direction of the linear cutting blade Th seen from the Q direction is inclined. Accordingly, the direction of the linear cutting blade Th seen from the X-direction is also inclined with respect to the Z-direction by a predetermined angle. In the present preferred embodiment, by rotating the rotor226about the rotation axis AX3with the press-fitted lock sleeve227loosened, the inclination angle (edge angle) of the linear cutting blade Th is changed. As seen above, the rotor226, lock sleeve227, and bolt228define an angle adjuster229.

As shown inFIG. 8, the tool head224is moved integrally with the first turret23in the Z- and X-directions by a Z-direction drive system M1and an X-direction drive system M2. The tool head224is also moved in the Y-direction by the Y-direction drive system M3. That is, the tool head224is disposed so as to be movable in the Z-direction, X-direction, and Y-direction with respect to the workpiece W2by the Z-direction drive system M1, X-direction drive system M2, and Y-direction drive system M3, respectively. As a result, the cutting tool T1is able to move with respect to the workpiece W2in a direction obtained by combining all or some of the Z-direction, X-direction, and Y-direction. In this case, the operator is able to cut the inclined surface Wb of the workpiece W2by moving the linear cutting blade Th in a combined direction (moving direction) of the X-, Y-, and Z-directions while rotating the workpiece W2. The Z-direction drive system M1, X-direction drive system M2, and Y-direction drive system M3are controlled by a controller CONT.

As seen above, even when the workpiece W2having the inclined surface Wb such as a tapered surface or spherical surface is cut, the operator is able to easily change the inclination angle (edge angle) of the linear cutting blade Th with respect to the Z-direction when seen from the X-direction, by using the angle adjuster229. Thus, the operator is able to easily change the direction of the linear cutting blade Th of the cutting tool T1in a short time. While, inFIGS. 7A, 7B and 8, the rotating portion226ais integral with the holder226b, the rotating portion226aand holder226bmay be independent. The configuration in which the holder25and rotor26are integral is not limited to the configuration shown inFIGS. 7A, 7B and 8and may be applied to the above preferred embodiments of the present invention.

While, in the above preferred embodiments of the present invention, the cutting tool T1is moved in a direction obtained by combining the Y- and Z-directions (e.g., in the direction P1shown inFIG. 4), other configurations may be used. For example, the workpiece may be cut while moving the cutting tool T1only in the Y-direction.FIGS. 9A and 9Binclude diagrams showing a case in which the cutting tool T1is moved in the Y-direction, in whichFIG. 9Ais a diagram of a workpiece W seen from the X-direction; andFIG. 9Bis a diagram of a workpiece W seen from the X-direction and shows a case in which the edge angle is different. InFIG. 9A, the edge angle is set to α; inFIG. 9B, the edge angle is set to β.

In bothFIGS. 9A and 9B, the linear cutting blade Th of the cutting tool T1moves from the negative Y-side to the positive Y-side with respect to a generating line D along a tangent plane of the cylindrical surface Wa of the workpiece W; a positive Z-side first end Th1of the linear cutting blade Th contacts the cylindrical surface Wa first; and when a second end Th2of the linear cutting blade Th leaves the generating line D, the cutting of the cylindrical surface Wa is complete. The edge angle inFIG. 9Ais smaller than that inFIG. 9B, and a length A1obtained by projecting the linear cutting blade Th inFIG. 9Aon the generating line D is longer than a length A2obtained by projecting the linear cutting blade Th inFIG. 9Bon the generating line D. Thus, inFIG. 9A, the workpiece is able to be cut more widely in the Z-direction with one movement in the Y-direction than inFIG. 9B. However, a larger cutting force than that inFIG. 9Bis applied to the workpiece W and therefore causes chattering vibration or the like in the workpiece W. In such a case, the cutting force applied to the workpiece W is reduced by increasing the edge angle as seen inFIG. 9B.

In the above preferred embodiments, the controller CONT may automatically calculate the cutting start position and cutting end position of the cutting tool T1and create a machining program, on the basis of information about required surface roughness, the edge angle, the diameter of the workpiece W, and the size of the workpiece W in the length direction (Z-direction). In this case, the controller CONT controls the Z-direction drive system M1, X-direction drive system M2, and Y-direction drive system M3on the basis of the newly created machining program. The operator is able to input the various types of information to the machine tool100through an operation panel or the like.

The above machine tools may include a sensor to detect the direction of the linear cutting blade Th and control the edge angle of the linear cutting blade Th in accordance with an output from the sensor. The sensor may be an optical or magnetic non-contact sensor. Also, the rotor26need not be rotated on the basis of the above configuration and, for example, may be directly rotated by a servo motor or the like.

While, in the above preferred embodiments, the angle adjuster29or the like changes the edge angle of the cutting tool T1by moving the holder25with respect to the tool head24or the like, other configurations may be used. For example, the angle adjuster may change the edge angle of the cutting tool T1by moving the tool head24or the like or the first turret23or the like, or may change the edge angle by moving the cutting tool T1with respect to the holder25.

In the above preferred embodiments, the workpiece W is cut while moving the cutting tool T1with respect to the workpiece W (the main spindle7, etc.); instead, the workpiece W may be cut while moving the workpiece W with respect to the cutting tool T1or while moving both the cutting tool T1and the workpiece W.