Cutting method and cutting apparatus

A tool main spindle, whose cutting angle can be changed, is translated by an X-axis moving mechanism portion on an X-axis provided in a plane perpendicular to an axis of a work; and is translated on a Y-axis by a Y-axis moving mechanism portion. Cutting of the work is performed by setting the cutting angle of the tool main spindle to an angle of the cutting tool at which the work has large dynamic rigidity, and causing an axis of a cutting tool to cross the work axis, and cutting the work with the cutting tool toward the axis of the work by cooperatively operating the X-axis moving mechanism portion and the Y-axis moving mechanism portion.

BACKGROUND OF THE INVENTION

This application claims the benefit of Japanese Patent Application Number 2008-179412 filed on Jul. 9, 2008, the entirety of which is incorporated by reference.

1. Field of the Invention

The present invention relates to cutting, more particularly, relates to a cutting method and a cutting apparatus which are capable of accurate cutting with a low incidence of chatter vibration and the like in a work.

2. Description of the Related Art

Cutting is generally performed by the structure shown in the illustration ofFIG. 11. InFIG. 11, reference numeral35indicates a workpiece (work) to be cut, reference numeral36indicates a tool post, reference numeral37indicates a cutting tool, reference numeral38indicates a motor, reference numeral M1indicates an axis of the work35, and reference numeral M5indicates a tool axis. As shown inFIG. 11, the tool post36has the cutting tool37so that the axis M1of the work35and the tool axis M5cross each other. The tool post36is translatable in an X-axis direction by the motor38. Outer-diameter cutting is performed by cutting the work35in the axis direction of the work35with the cutting tool from the X-axis direction by the motor38, and then feeding the cutting tool37in the work axis-M1direction while rotating the work35.

However, performing heavy cutting by this cutting method generates chatter vibration when the work35has low dynamic rigidity, thereby causing problems in some cases, such as reducing a finishing accuracy of a processing surface of the work35, damaging the cutting tool37, and the like. The cutting methods described in, for example, Japanese Registered Utility Model No. 2,590,593 and Japanese Unexamined Patent Publication No. S49-105277 were proposed to solve such problems. The method described in Japanese Registered Utility Model No. 2,590,593 suppresses vibration of the work35by bringing a steady rest into contact with the work35for lathe turning (cutting) of the work35. The method described in Japanese Unexamined Patent Publication No. S49-105277 suppresses chatter vibration by periodically changing the rotational speed of the work35, that is, the rotational speed of a main spindle.

However, the method described in Japanese Registered Utility Model No. 2,590,593 is not suitable for reducing the size of a machine tool because the steady rest for the work35is provided in a processing machine and thus a processing region is reduced. The method described in Japanese Unexamined Patent Publication No. S49-105277, on the other hand, changes the rotational speed of a main spindle during processing, and thus tends to leave marks on the processing surface of the work35due to the change in rotational speed, thereby causing a problem such as reduced finishing accuracy.

The chatter vibration and the dynamic rigidity of the work will now be described. The chatter vibration of the work is a vibration phenomenon which occurs during processing. Whether the chatter vibration occurs or not depends on the processing conditions, the dynamic rigidity of the work, and the like. The chatter vibration tends to occur under high-load conditions such as heavy cutting, and tends to occur when the work has low dynamic rigidity.

FIG. 12shows an example of a dynamic compliance of the work which is an inverse number of the dynamic rigidity. This figure shows that the dynamic compliance is small (the dynamic rigidity is large) in the direction of 30°, and the dynamic compliance is large (the dynamic rigidity is small) in the direction of 120°. Thus, the dynamic compliance of the work is normally anisotropic, and the dynamic rigidity varies according to the angle. The same applies to the case where the work itself has a cylindrical shape and is isotropic. This is due to the influence of intrinsic anisotropy in the spindle stock.

This measurement result shows that the chatter vibration tends to be generated during cutting when the cutting angle toward the rotation center of the work is set to be 120° which is an angle with large dynamic compliance, while the chatter vibration is less likely to be generated and excellent cutting can be performed when the cutting angle is set to be 30° which is an angle with small dynamic compliance. Rotary cutting using a rotating tool as the cutting tool is similar in this regard. In rotary cutting as well, cutting at an angle with small dynamic compliance is equal to cutting at an angle with high dynamic rigidity, whereby accurate cutting can be achieved.

SUMMARY OF THE INVENTION

The present invention was developed in view of the above characteristics of the dynamic rigidity of the work, and it is an object of the present invention to provide a highly versatile cutting method and a highly versatile cutting apparatus capable of suppressing chatter vibration and improving processing accuracy without reducing a processing region and without reducing the finishing accuracy of a processing surface.

In order to solve the above problems, the invention according to a first aspect is a cutting method for cutting a work comprising steps of; positioning a cutting tool from a direction perpendicular to an axis of the work toward the axis; providing an angle changing unit for changing a cutting angle of the cutting tool; detecting an angle of the cutting tool at which the work has large dynamic rigidity; adjusting the angle changing unit so that the cutting angle of the cutting tool toward the work axis becomes equal to the angle at which the work has large dynamic rigidity; and cutting the work with the cutting tool while maintaining the set cutting angle.

According to this method, cutting is performed by setting the cutting angle toward a rotation center of the work to a direction in which the work has large dynamic rigidity. Therefore, the generation of chatter vibration can be suppressed and accurate processing can be implemented. Further, since a device such as a steady rest is not required, high versatility can be obtained without affecting the processing region.

The invention according to a second aspect is a cutting apparatus for cutting a work including a cutting tool positioned from a direction perpendicular to an axis of the work toward the axis, wherein one of the work and the cutting tool rotates. The cutting apparatus includes: an angle changing unit for changing a cutting angle of the cutting tool; an angle detecting unit for detecting an angle of the cutting tool at which the work has large dynamic rigidity; an angle setting unit for controlling the angle changing unit; and a cutting control unit for controlling cutting. The angle setting unit controls the angle changing unit so that the cutting angle of the cutting tool becomes equal to the angle at which the work has large dynamic rigidity as detected by the angle detecting unit. The cutting control unit performs cutting of the work with the cutting tool while maintaining the cutting angle set by the angle setting unit.

According to this structure, the angle detecting unit detects the angle with largest dynamic rigidity, and the angle setting unit sets the cutting angle toward a rotation center of the work to the direction of the largest dynamic angle. Therefore, the generation of chatter vibration can be suppressed and accurate processing can be implemented. Further, since a device such as a steady rest is not required, high versatility can be obtained without affecting the processing region.

The invention according to a third aspect is the cutting apparatus of the invention according to the second aspect, wherein: the cutting tool is mounted to a tool main spindle that is positioned in a direction perpendicular to the axis of the work, while the angle changing unit includes a first moving unit moving on a first axis provided in a plane perpendicular to the axis of the work, a second moving unit moving on a second axis different from the first axis and provided in a plane perpendicular to the axis of the work, and a tool-main-spindle pivoting portion provided in the tool main spindle for enabling the cutting angle to be changed; the angle setting unit controls a cutting angle of the tool main spindle so that the cutting angle of the tool main spindle becomes equal to the angle at which the work has large dynamic rigidity as detected by the angle detecting unit, and controls the first moving unit and the second moving unit so that the axis of the cutting tool crosses the axis of the work; and the cutting control unit controls the first moving unit and the second moving unit to translate the cutting tool on the two axes, thereby cutting the rotating work toward a rotation center of the work while the two axes are maintained in the crossed state.

According to this structure, the cutting angle can be easily set to the angle with large dynamic rigidity by pivoting the tool-main-spindle pivoting portion. Moreover, the rotating work can be cut by translating the cutting tool using the first moving unit and the second moving unit. Thus, the generation of chatter vibration can be suppressed and accurate lathe turning can be implemented.

The invention according to a fourth aspect is the cutting apparatus of the invention according to the second aspect, wherein: the cutting tool is mounted to a tool post that is positioned in a direction perpendicular to the axis of the work, while the angle changing unit includes a composite saddle of a lower saddle for adjusting a height of the tool post and an upper saddle provided over the lower saddle for changing a cutting angle of the tool post; the upper saddle includes a single-axis moving unit for translating the cutting tool to a direction of the set cutting angle; the angle setting unit controls an angle of the upper saddle so that the cutting angle of the tool post becomes equal to the angle at which the work has large dynamic rigidity as detected by the angle detecting unit, and controls the lower saddle so that the axis of the cutting tool crosses the axis of the work; and the cutting control unit controls the single-axis moving unit to cut the rotating work toward a rotation center of the work.

According to this structure, the cutting angle can be easily set to the angle with large dynamic rigidity by changing a tilt angle of the tool post. Moreover, the rotating work can be cut by causing the axis of the cutting tool to cross the axis of the work with the lower saddle and the upper saddle and maintaining the cutting angle. Thus, the generation of chatter vibration can be suppressed and accurate lathe turning can be implemented.

The invention according to a fifth aspect is the cutting apparatus of the invention according to the second aspect, wherein: the cutting tool is mounted to a tool main spindle that is positioned in a direction perpendicular to the axis of the work and including a tool rotating unit, while the angle changing unit includes a first moving unit moving on a first axis provided in a plane perpendicular to the axis of the work, a second moving unit moving on a second axis different from the first axis and provided in a plane perpendicular to the axis of the work, and a tool-main-spindle pivoting portion provided in the tool main spindle for enabling the cutting angle to be changed; the angle setting unit controls a cutting angle of the tool main spindle so that the cutting angle of the tool main spindle becomes equal to the angle at which the work has large dynamic rigidity as detected by the angle detecting unit, and controls the first moving unit and the second moving unit so that the axis of the cutting tool crosses the axis of the work; and the cutting control unit controls the first moving unit and the second moving unit to translate the cutting tool on the two axes, and rotates the cutting tool while the two axes are maintained in the crossed state, thereby cutting the work toward an axis of the work.

According to this structure, the cutting angle can be easily set to the angle with large dynamic rigidity by pivoting the tool-main-spindle pivoting portion. Moreover, the work can be cut with the rotating tool by translating the cutting tool using the first moving unit and the second moving unit. Thus, the generation of chatter vibration can be suppressed and accurate rotary cutting can be implemented.

The invention according to a sixth aspect is the cutting apparatus of the invention according to the second aspect, wherein: the cutting tool is mounted to a tool post that is positioned in a direction perpendicular to the axis of the work and includes a tool rotating unit, while the angle changing unit includes a composite saddle of a lower saddle for adjusting a height of the tool post and an upper saddle provided over the lower saddle for changing a cutting angle of the tool post; the upper saddle includes a single-axis moving unit for translating the cutting tool to a direction of the set cutting angle; the angle setting unit controls an angle of the upper saddle so that the cutting angle of the tool post becomes equal to the angle at which the work has large dynamic rigidity as detected by the angle detecting unit, and controls the lower saddle so that the axis of the cutting tool crosses the axis of the work; and the cutting control unit controls the single-axis moving unit and rotates the cutting tool while the two axes are maintained in the crossed state, thereby cutting the work toward an axis of the work.

According to this structure, the cutting angle can be easily set to the angle with large dynamic rigidity by changing the tilt angle of the tool post. Moreover, the work can be cut with the rotating tool by causing the axis of the cutting tool to cross the axis of the work with the lower saddle and the upper saddle and maintaining the cutting angle. Thus, the generation of chatter vibration can be suppressed and accurate rotary cutting can be implemented.

According to the present invention, cutting can be performed by setting the cutting angle toward the rotation center of the work to a direction in which the work has large dynamic rigidity. Therefore, the generation of chatter vibration can be suppressed and cutting can be performed with high finished surface accuracy. Further, since a device such as a steady rest is not separately required, high versatility can be obtained without affecting the processing region.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

FIGS. 1 to 3are illustrations showing a first embodiment of a cutting apparatus according to the present invention.FIG. 1is a plan view from a Y-axis direction, andFIG. 2is a front view from an axis direction of a work. InFIGS. 1 and 2, reference numeral1indicates a spindle stock of the cutting apparatus, reference numeral2indicates a main spindle rotatably supported by the spindle stock1, reference numeral3indicates a chuck provided at the tip of the main spindle2and including a pawl4for holding the work5, reference numeral6indicates a cutting tool, reference numeral7indicates a tool main spindle to which the cutting tool6is attached, reference numeral8indicates a Y-axis moving mechanism portion for translating the tool main spindle7in the Y-axis direction, reference numeral9indicates a saddle mounted on a base (not shown) of the cutting apparatus for enabling the tool main spindle7to be moved in an X-axis direction, and reference numeral10indicates an X-axis moving mechanism portion for translating the saddle9in the X-axis direction.

The Y-axis moving mechanism portion8and the X-axis moving mechanism portion10are formed by ball screw mechanisms. The Y-axis moving mechanism portion8is driven by a Y-axis motor8amounted on the saddle9, and the X-axis moving mechanism portion10is driven by an X-axis motor10amounted on the base.

It should be noted that reference numeral M1indicates a work axis which is the rotation center of the work, reference numeral M2indicates a tool-main-spindle axis, and reference numeral M3indicates a tool axis. A plane perpendicular to the work axis M1is an XY plane. The tool main spindle7holds the cutting tool6at an end thereof in a rotationally indexable manner so that the tool-main-spindle axis M2and the tool axis M3cross each other. The tool main spindle7includes a tool-main-spindle pivoting portion L1for enabling the cutting angle of the cutting tool to be changed.

FIG. 3shows a control device for controlling this cutting apparatus. As shown inFIG. 3, the control device includes a numerical control device40for controlling various motors, an angle detection device41for calculating an angle with large dynamic rigidity, a main-spindle angle detector42for detecting a rotation angle of the main spindle2, an X-axis detector43for detecting an X-axis displacement amount resulting from driving with the X-axis motor10a, a Y-axis detector44for detecting a Y-axis displacement amount resulting from driving with the Y-axis motor8a, and a tool-angle detector45for detecting an angle of the cutting tool6.

It should be noted that reference numeral2aindicates a main-spindle motor for rotating the main spindle2, and reference numeral7aindicates a tool-main-spindle motor for driving the tool-main-spindle pivoting portion L1.

The numerical control device40includes a program storage section47for storing a work processing program, a program analysis section48for analyzing the processing program, and a drive control section49for controlling various motors. The angle detection device41includes an impulse hammer51, a dynamic-compliance calculation section52, and a computing section53for calculating the angle with the largest dynamic rigidity based on dynamic compliance.

More specifically, in the angle detection device41, vibration generated by the impulse hammer51is processed (e.g., Fourier analysis) into a dynamic compliance value in the dynamic-compliance calculation section52. The computing section53simultaneously receives the dynamic compliance value and the main-spindle angle, and obtains a main-spindle angle, i.e., a work angle (θ), of the smallest dynamic compliance (the largest dynamic rigidity). This process may be performed either by comparing the dynamic compliance values sequentially supplied during measurement by the impulse hammer with the previous value and leaving the smaller value and angle, or by storing the values for one rotation of the main spindle (work) and selecting the smallest angle.

Then, the angle with the largest dynamic rigidity obtained by the computing section53is applied to the drive control section49. The drive control section49combines the received angle with a control command generated by analyzing a normal processing program, thereby producing a motor driving signal to control each motor.

The cutting apparatus structured as described above performs cutting as follows. First, an angle (θ) with the largest dynamic rigidity is obtained by the above procedure. In the case where the measurement result shows that the direction in which the work5has large dynamic rigidity is at an angle of θ from the X-axis direction (the state shown inFIG. 2), the numerical control device40controls the tool-main-spindle pivoting portion L1of the tool main spindle7so that a cutting angle toward the axis M1of the work5, that is, toward the rotation center, becomes θ.

The numerical control device40then operates the X-axis motor10aand the Y-axis motor8aso as to maintain the state in which the tool axis M3of the cutting tool6crosses the work axis M1at this angle. Thus, a cutting control (lathe turning control) is performed so that the cutting tool6cuts the work5toward the work axis M1.

Outer-diameter cutting of the work5is performed by maintaining the cutting angle θ of the cutting tool6at a fixed value while rotating the work5together with the main spindle2, and translating the cutting tool6while maintaining the state in which the tool axis M3crosses the work axis M1. In other words, outer-diameter cutting is performed by cutting the work5with the cutting tool6toward the work axis M1.

The cutting tool6is translated by moving the tool main spindle7through cooperative operation of the X-axis motor10aand the Y-axis motor8a. The outer peripheral surface of the work5is cut in this manner. The cutting tool6is then fed along the work axis M1, whereby the outer-diameter cutting is performed.

It should be noted that a similar operation is performed when the outer periphery of the work5is grooved. Like outer-diameter cutting, cutting is performed by indexing an angle of the cutting tool6, and feeding the tool main spindle7along the tool axis M3in a moving operation achieved by synthesis of the X-axis and the Y-axis.

Because the cutting angle toward the rotation center of the work is thus set to a direction in which the work has large dynamic rigidity, the generation of chatter vibration can be suppressed and accurate processing can be implemented. Further, since a device such as a steady rest is not required, high versatility can be obtained without affecting the processing region.

Moreover, the cutting angle can be easily set to an angle with large dynamic rigidity by pivoting the tool-main-spindle pivoting portion. By translating the cutting tool using the X-axis moving mechanism portion and the Y-axis moving mechanism portion, cutting of the rotating work can be performed while the work axis and the tool axis are maintained in the crossed state. As a result, accurate lathe turning can be implemented.

Second Embodiment

FIG. 4shows a second embodiment of the cutting apparatus according to the present invention.FIG. 4is a front view from the axis direction of the work5. InFIG. 4, reference numeral15indicates a lower saddle which translates in the Y-axis direction, reference numeral16indicates a Y-axis moving mechanism portion for translating the lower saddle15in the Y-axis direction, reference numeral18indicates an upper saddle positioned above the lower saddle15for providing a cutting angle to a cutting tool19, reference numeral17indicates a jack for adjusting a tilt angle of the upper saddle18, reference numeral20indicates a tool post to which the cutting tool19is mounted, and reference numeral21indicates an XS-axis moving mechanism portion for translating the tool post20.

The upper saddle18has one end thereof on the work5side rotatably connected to the lower saddle15, and another end supported by the retractable jack17. The tool post20is mounted to the upper saddle18through the XS-axis moving mechanism portion21provided on the upper saddle18. The tool post20is mounted so as to be translatable in the maximum tilting direction of the upper saddle18.

The Y-axis moving mechanism portion16and the XS-axis moving mechanism portion21are formed by ball screw mechanisms. The Y-axis moving mechanism portion16is driven by a Y-axis motor16amounted on a base (not shown), and the XS-axis moving mechanism portion21is driven by an XS-axis motor21amounted on the upper saddle18. Thus, the tool post20moves vertically by a composite saddle formed from the lower saddle15and the upper saddle18, and the cutting angle of the tool post20can be changed. The tool post20can be set to any cutting angle by controlling the Y-axis motor16aand a jack drive motor (not shown) provided for the jack17. Reference numeral M4indicates a tool axis.

FIG. 5shows a control device for controlling this cutting apparatus. The control device ofFIG. 5is different from that ofFIG. 3with regard to the structures of the motors and the detectors controlled by the drive control section49. The control device ofFIG. 5includes the XS-axis motor21a, an XS-axis detector55for detecting a displacement amount resulting from driving with the XS-axis motor21a, a jack drive motor17afor driving the jack17, and a jack-angle detector57for detecting an angle which is changed by driving with the jack drive motor17a. It should be noted that components similar to those ofFIG. 3are denoted by the same reference numerals and characters as used inFIG. 3, and descriptions thereof will be omitted.

The cutting apparatus structured as described above performs cutting as follows. First, an angle (θ) with the largest dynamic rigidity is obtained by a procedure similar to that of the first embodiment. This angle is an angle viewed from the X-axis direction, andFIG. 4shows a state in which the cutting angle has been set to the obtained angle θ.

Based on the angle information thus obtained, the numerical control device40controls the jack drive motor17ato set the cutting angle toward the rotation center of the work5to θ.

Next, the numerical control device40adjusts the height of the tool post20using the Y-axis motor16aof the Y-axis moving mechanism portion16so that the work axis M1and the tool axis M4cross each other. Then, the numerical control device40controls the XS-axis motor21aof the XS-axis moving mechanism portion21to translate the tool post20and the cutting tool19, thereby cutting the work5toward the rotation center of the work5. Cutting is thus performed in this manner.

Because the cutting angle toward the rotation center of the work is thus set to a direction in which the work has large dynamic rigidity, the generation of chatter vibration can be suppressed and accurate processing can be implemented. Further, since a device such as a steady rest is not required, high versatility can be obtained without affecting the processing region.

Moreover, the cutting angle can be easily set to an angle with large dynamic rigidity by changing the tilt angle of the tool post. The lower saddle and the upper saddle cross the axis of the cutting tool with the axis of the work, and cutting of the rotating work can be performed while the work axis and the tool axis are maintained in the cross state. As a result, accurate lathe turning can be implemented.

It should be noted that, in the first and second embodiments, the cutting tools6,19are moved with respect to the work5. Cutting is performed through relative movement of the work5and the cutting tools6,19, however, and the work5may be moved with respect to the cutting tools6,19.

Third Embodiment

FIGS. 6 and 7are illustrations showing a third embodiment of the cutting apparatus according to the present invention.FIG. 6is a front view from the Y-axis direction, andFIG. 7is a front view from an axis-M direction of the work5. The cutting apparatus of the third embodiment has a similar tool drive mechanism to that of the first embodiment, but is different from the first embodiment in that a cutting tool25itself rotates to perform rotary cutting.

InFIGS. 6 and 7, reference numeral24indicates a tool main spindle having a built-in tool rotation motor (not shown), reference numeral25indicates a rotating tool (cutting tool) for performing rotary cutting, and reference numeral26indicates a main-spindle support for moving the tool main spindle24using a saddle9. Components similar to those ofFIG. 1are denoted by the same reference numerals and characters as used inFIG. 1. The main-spindle support26is provided with a tool-main-spindle pivoting portion L2for enabling the cutting angle of the cutting tool25to be changed.

FIG. 8shows a control device for controlling this cutting apparatus. The control device ofFIG. 8is different from that ofFIG. 3in that the control device ofFIG. 8additionally controls a tool rotation motor25afor rotating the tool25, and that the cutting angle of the cutting tool25is changed by a main-spindle-support motor26afor driving the tool-main-spindle pivoting portion L2. It should be noted that components similar to those ofFIG. 3are denoted by the same reference numerals and characters as used inFIG. 3, and descriptions thereof will be omitted.

The cutting apparatus structured as described above performs cutting as follows. First, an angle (θ) with the largest dynamic rigidity is obtained by the procedure described in the first embodiment. This angle is an angle viewed from the X-axis direction, andFIG. 7shows a state in which the cutting angle has been set to the obtained angle θ.

Based on the angle information thus obtained, the numerical control device40pivots the tool-main-spindle pivoting portion L2of the main-spindle support26to set the cutting angle toward the rotation center of the work5to θ. The numerical control device40then controls the X-axis motor10aand the Y-axis motor8aso that the tool axis M3of the cutting tool25crosses the work axis M1at this angle, and the cutting tool25cuts the work5toward the work axis M1.

In this case, cutting of the work5is performed without rotating the work5. Cutting of the work5is performed by rotating the cutting tool25using the tool rotation motor25awhile the cutting angle θ of the cutting tool25is maintained at a fixed value and the tool axis M3and the work axis M1are maintained in the crossed state. In other words, rotary cutting of the work is performed by cutting the work5toward the work axis M1with the rotating tool25.

It should be noted that a similar operation is performed when the outer periphery of the work is grooved or a plane surface of the work is processed by feeding a tool such as an end mill in the axis direction of the work. In this case, cutting is performed by indexing an angle of the cutting tool25, by cutting the work by feeding the tool along the tool axis M3in a moving operation achieved by synthesis of the X-axis and the Y-axis, and further by causing movement along a Z-axis (the work axis direction) that is not shown.

Because the cutting angle toward the rotation center of the work is thus set to a direction in which the work has large dynamic rigidity, the generation of chatter vibration can be suppressed and accurate processing can be implemented. In addition, since a device such as a steady rest is not required, high versatility can be obtained without affecting the processing region.

Moreover, the cutting angle can be easily set to an angle with large dynamic rigidity by pivoting the tool-main-spindle pivoting portion of the main-spindle support, and cutting with the rotating tool can be performed by translating the cutting tool using the X-axis moving mechanism portion and the Y-axis moving mechanism portion while the work axis and the tool axis are maintained in the crossed state. As a result, accurate rotary cutting can be implemented.

Fourth Embodiment

FIG. 9shows a fourth embodiment of the cutting apparatus according to the present invention.FIG. 9is a front view from the axis direction of the work5. The cutting apparatus of the fourth embodiment has a similar tool drive mechanism to that of the second embodiment, but is different from the second embodiment in that a cutting tool29itself rotates to perform rotary cutting.

InFIG. 9, reference numeral29indicates a rotating tool (cutting tool) for performing rotary cutting, and reference numeral30indicates a tool post having a built-in motor (tool rotation motor). Components similar to those ofFIG. 4are denoted by the same reference numerals and characters as used inFIG. 4, and descriptions thereof will be omitted.

FIG. 10shows a control device for controlling this cutting apparatus. The control device ofFIG. 10is different from that ofFIG. 5in that the control device ofFIG. 10additionally controls a tool rotation motor29afor rotating the cutting tool29. Components similar to those ofFIG. 5are denoted by the same reference numerals and characters as used inFIG. 5, and descriptions thereof will be omitted.

The cutting apparatus structured as described above performs cutting as follows. First, an angle (θ) with the largest dynamic rigidity is obtained by the procedure described in the first embodiment. This angle is an angle viewed from the X-axis direction, andFIG. 9shows a state in which the cutting angle has been set to the obtained angle θ. The numerical control device40controls the jack drive motor of the jack17to set the cutting angle toward the rotation center of the work5to θ.

Next, the numerical control device40adjusts the height of the tool post30using the Y-axis motor16aof the Y-axis moving mechanism portion16so that the work axis M1and the tool axis M4cross each other. Then, the numerical control device40controls the XS-axis motor21aof the XS-axis moving mechanism portion21to translate the tool post30and the cutting tool29, thereby cutting the work5toward the axis M1of the work5with the rotating cutting tool5. Cutting (rotary cutting) is thus performed in this manner.

It should be noted that, like the third embodiment, a similar operation is performed when the outer periphery of the work is grooved or a plane surface of the work is processed by feeding a tool such as an end mill in the axis direction of the work. In this case, cutting is performed by indexing an angle of the cutting tool29, cutting the work by feeding the tool along the tool axis M4in a moving operation along the XS-axis, and through further movement along the Z-axis (the work axis direction) that is not shown.

Because the cutting angle toward the rotation center of the work is thus set to a direction in which the work has large dynamic rigidity, the generation of chatter vibration can be suppressed and accurate processing can be implemented. Further, since a device such as a steady rest is not required, high versatility can be obtained without affecting the processing region.

Moreover, the cutting angle can be easily set to an angle with large dynamic rigidity by changing the tilt angle of the tool post. The lower saddle and the upper saddle cross the axis of the cutting tool with the axis of the work, and the work can be cut with the rotating tool while maintaining the cutting angle. As a result, the generation of chatter vibration is suppressed and accurate rotary cutting can be implemented.

It should be noted that in each of the above embodiments, the control device includes the angle detection device41, and obtains the direction with largest dynamic rigidity by calculating dynamic compliance through a control of the control device itself. However, the angle detection device41may be provided as a separate element from the control device, that is, as a separate element from the cutting apparatus, and the angle detection device41may be mounted when it is necessary to obtain dynamic compliance and the like.