Machine tool and control position determination method thereof

Abstract

To provide a configuration capable of easily avoiding interference between a deburring tool and a workpiece due to a command error or the like when commanding movement of the deburring tool in the direction of a linear axis 3 with the workpiece as a reference.SOLUTION: Acquiring, by a controller U1 of a machine tool (1), values (CD) representing diameters corresponding to a circumferential portion C1p of a hole (C1) as viewed in a direction of a machining center line (X-axis direction) and values (OD) representing diameters corresponding to a circumference of a circle centered on a spindle center line AX1 and passing through the circumferential portion C1p in a cross section orthogonal to the spindle center line AX1; Based on the values (CD) and (OD), the linear-axis coordinate (Zp) corresponding to the cut position C1p changing along the circumference P1 in the linear-axis (Z-axis) and the rotation angle (Cp) corresponding to the cut position P1 in the rotation-axis (C-axis) are determined, and the relative positional relationship in the main-spindle-axis direction (Z-axis direction) is controlled to the linear-axis coordinate (Zp) so that the cut position P1 changes along the circumference C1p, and the rotation of the main spindle 11 is controlled to the rotation angle (Cp).SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a machine tool capable of cutting the periphery of a hole in a workpiece that is oriented perpendicular to the center line of its spindle, and a control position determination method for the machine tool. [Background technology]

[0002] Numerically controlled (NC) lathes are a well-known machine tool that uses tools to machine cylindrical workpieces held by a spindle. When a cross hole is formed in a workpiece using a rotary tool oriented along a machining centerline perpendicular to the spindle centerline, burrs form around the periphery of the cross hole. Therefore, burrs are removed using a dedicated tool attached to the tool post. NC lathes can remove burrs around the periphery of a cross hole by controlling the relative cutting position of the dedicated tool on the workpiece in three directions (X-axis, Y-axis, and Z-axis) according to a machining program created by an operator. The machine tool disclosed in Patent Document 1 chamfers the opening edge of a cross hole by moving a conical tool having a conical cutting blade in three directions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 178355 Summary of the Invention [Problem to be solved by the invention]

[0004] In a machining program, it is not easy to command the movement of a special tool in three directions (X-axis, Y-axis, and Z-axis) to remove burrs around a cross hole. If the movement command is not appropriate, there is a possibility that the special tool will interfere with the workpiece. The above-mentioned problems are not limited to lathes, but also exist in various machine tools such as machining centers.

[0005] The present invention discloses a configuration that can easily avoid interference between the deburring tool and the workpiece due to command errors when commanding movement of the deburring tool in three directions along a linear axis based on the workpiece. [Means for solving the problem]

[0006] The machine tool of the present invention comprises: a spindle that rotates together with the workpiece around the spindle center line; a tool rest to which a deburring tool is attached that cuts a peripheral portion of a hole in the workpiece along a machining center line that is perpendicular to the spindle center line; a control unit that controls a relative positional relationship between the spindle and the tool rest along a linear axis that extends along the spindle center line, and controls rotation of the spindle about a rotation axis that is centered on the spindle center line, The control unit A value (CD) representing a diameter corresponding to the peripheral portion when the hole is viewed from the machining center line direction along the machining center line, and a value (OD) representing a diameter corresponding to a circumference passing through the peripheral portion with the spindle center line as the center in a cross section perpendicular to the spindle center line are obtained; determining a translatory axis coordinate corresponding to a cutting position that varies along the circumference on the translatory axis and a rotational angle corresponding to the cutting position on the rotational axis based on the values ​​(CD) and (OD); The relative positional relationship in the spindle center line direction along the spindle center line is controlled to the linear axis coordinates, and the rotation of the spindle is controlled to the rotation angle, so that the cutting position changes along the circumferential portion.

[0007] Furthermore, a control position determination method for a machine tool of the present invention is a method for determining a control position for a machine tool comprising: a spindle that rotates together with a workpiece about a spindle center line; and a tool post to which a deburring tool is attached that cuts a peripheral portion of a hole in the workpiece oriented along a processing center line perpendicular to the spindle center line, the method controlling a relative positional relationship between the spindle and the tool post on a linear axis along the spindle center line, and rotation of the spindle on a rotation axis about the spindle center line, the method comprising: a first step of acquiring a value (CD) representing a diameter corresponding to the peripheral portion when the hole is viewed from a machining center line direction along the machining center line, and a value (OD) representing a diameter corresponding to a circumference centered on the spindle center line and passing through the peripheral portion in a cross section perpendicular to the spindle center line; and a second step of determining, based on the value (CD) and the value (OD), a linear axis coordinate corresponding to the cutting position on the linear axis and a rotation angle corresponding to the cutting position on the rotation axis, so that the cutting position by the deburring tool varies along the periphery. [Effects of the Invention]

[0008] According to the present invention, a configuration can be provided that can easily avoid interference between the deburring tool and the workpiece due to command errors when commanding movement of the deburring tool in three directions along the linear axis based on the workpiece. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view schematically showing an example of the configuration of a machine tool. [Figure 2] FIG. 2 is a block diagram schematically illustrating an example of the configuration of an electric circuit of a machine tool. [Figure 3] Figure 3A is a plan view schematically showing an example of a cylindrical workpiece having a cross hole, Figure 3B is a longitudinal cross-sectional view at position A1-A1 in Figure 3A, and Figure 3C is a transverse cross-sectional view at position A2-A2 in Figure 3A. [Figure 4] FIG. 4A is a plan view showing an example of a cutting position that changes along the circumference of a cross hole, and FIGS. 4B and 4C are cross-sectional views showing an example in which a deburring tool oriented along the spindle center line is placed on the outer peripheral surface of a cylindrical workpiece. [Figure 5] 5A and 5B are cross-sectional views that schematically show an example in which a deburring tool oriented along the center line of a spindle is disposed on the inner peripheral surface of a cylindrical workpiece. [Figure 6]10 is a diagram showing an example of determining a Z-axis coordinate Zp and a C-axis angle Cp corresponding to a cutting position based on a diameter value (CD) of a cross hole and an outer diameter value (OD) of a workpiece. FIG. [Figure 7] 10 is a diagram showing a schematic example of determining a Z-axis coordinate Zp and a C-axis angle Cp corresponding to a cutting position based on a diameter value (CD) of a cross hole and an inner diameter value (OD) of a workpiece. FIG. [Figure 8] 10 is a flowchart schematically illustrating an example of a deburring process. [Figure 9] 10A and 10B are diagrams illustrating an example of Z-axis movement and C-axis rotation of a workpiece during deburring. [Figure 10] FIG. 10 is a diagram showing a schematic example of determining the Z-axis coordinate Zp and C-axis angle Cp corresponding to the cutting position based on the diameter value (CD) of the long hole, the inner diameter value (OD) of the workpiece, and the center-to-center distance value (LC) of the arc portion. [Figure 11] 10 is a flowchart schematically illustrating an example of a deburring process for the periphery of a slotted hole. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention. Of course, the following embodiments are merely examples of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0011] (1) Summary of the aspects included in the present invention: First, an overview of the embodiments included in the present invention will be described with reference to the examples shown in Figures 1 to 11. Note that the figures in this application are diagrams showing examples in a schematic manner, and the magnifications in the directions shown in these figures may differ, and the figures may not be consistent with each other. Of course, each element of this embodiment is not limited to the specific example indicated by the symbol.

[0012] [Aspect 1] As illustrated in FIGS. 1 and 2, a machine tool (e.g., lathe 1) according to one embodiment includes a spindle 11, a tool rest 30, and a control unit U1. The spindle 11 rotates together with a workpiece W1 about a spindle center line AX1. A deburring tool TO3 is attached to the tool rest 30. The tool TO3 cuts a peripheral portion C1p of a hole (e.g., a cross hole C1) in the workpiece W1 oriented along a machining center line AX2 perpendicular to the spindle center line AX1. The control unit U1 controls the relative positional relationship between the spindle 11 and the tool rest 30 along a linear axis (e.g., the Z-axis) along the spindle center line AX1, and the rotation of the spindle 11 about a rotational axis (e.g., the C-axis) centered on the spindle center line AX1. The control unit U1 acquires a value (CD) representing a diameter corresponding to the peripheral portion C1p when the hole (C1) is viewed from a machining center line direction (e.g., the X-axis direction) along the machining center line AX2, and a value (OD) representing a diameter corresponding to a circumference centered on the spindle center line AX1 and passing through the peripheral portion C1p in a cross section perpendicular to the spindle center line AX1 (e.g., the cross section shown in the cross-sectional view 102 in FIGS. 6 and 7), as exemplified in Fig. 8, etc. The control unit U1 determines, based on the values ​​(CD) and (OD), a translational axis coordinate (e.g., Z-axis coordinate Zp) corresponding to cutting position P1 that changes along the peripheral portion C1p on the translational axis (Z-axis), and a rotational angle (e.g., C-axis angle Cp) corresponding to cutting position P1 on the rotational axis (C-axis). As illustrated in Figures 8 and 9, the control unit U1 controls the relative positional relationship in the spindle center line direction (e.g., Z-axis direction) along the spindle center line AX1 to the linear axis coordinate (Zp) so that the cutting position P1 changes along the peripheral portion C1p, and controls the rotation of the spindle 11 to the rotation angle (Cp).

[0013] By obtaining the value (CD) representing the diameter of the hole (C1) as viewed in the machining center line direction (X-axis direction) and the value (OD) representing the outer diameter or inner diameter of the workpiece W1 as viewed in the spindle center line direction (Z-axis direction), the peripheral portion C1p of the hole (C1) can be cut by the deburring tool TO3. In this case, the control unit U1 controls two axes: the linear axis (Z-axis) along the spindle center line AX1 and the rotational axis (C-axis) about the spindle center line AX1, rather than the three linear axes. The rotation angle (Cp) of the workpiece W1 around the spindle center line AX1 is controlled in accordance with the cutting position P1, while the relative drive axis coordinates of the deburring tool TO3 with respect to the workpiece W1 are controlled in accordance with the cutting position P1. This allows interference between the deburring tool TO3 and the workpiece W1 to be easily avoided. Therefore, the above aspect can provide a machine tool that can easily avoid interference between the deburring tool and the workpiece due to command errors when commanding movement of the deburring tool in the three linear axis directions based on the workpiece.

[0014] Here, the control unit may move the spindle along the spindle center line without moving the tool rest, may move the tool rest along the spindle center line without moving the spindle, or may move both the spindle and the tool rest along the spindle center line. A hole oriented along the machining center line can also be said to be centered on the machining center line. Holes oriented along the machining center line include cross holes that connect from the outer peripheral surface to the inner peripheral surface of a cylindrical workpiece, horizontal holes that cross the workpiece along the machining center line, and blind holes that are recessed from the outer peripheral surface to partway through the workpiece along the machining center line. The peripheral portion cut by the deburring tool may be the outer peripheral surface of the workpiece or the inner peripheral surface of the workpiece. For example, when a cross hole is formed in a cylindrical workpiece, burrs may occur on the peripheral portion of both the outer peripheral surface and the inner peripheral surface of the workpiece. The deburring tool may be any tool capable of cutting the periphery of a hole in the workpiece that is oriented along the machining center line, and a rotary tool such as an end mill may be used. When viewed from the machining centerline, the periphery of the hole only needs to have a portion that can be called a diameter, and may include straight portions, etc. The diameter corresponding to the periphery means the diameter of the portion that can be called a diameter. The value (CD) may be the diameter corresponding to the periphery, the radius corresponding to the periphery, or a value that can be converted to the diameter corresponding to the periphery. The value (OD) may be a diameter corresponding to a circumference passing through the periphery, a radius corresponding to a circumference passing through the periphery, or a value that can be converted to a diameter corresponding to a circumference passing through the periphery. The above remarks also apply to the following aspects.

[0015] [Aspect 2] 4B and 5A, the deburring tool TO3 may be attached to the tool rest 30 in an orientation along the spindle center line AX1. The tool rest 30 may rotate the deburring tool TO3 around a deburring tool center line AX3 that is aligned with the spindle center line AX1. In the above case, the peripheral portion C1p of the hole (C1) is cut by the deburring tool TO3, which rotates about the deburring tool center line AX3 that is aligned with the spindle center line AX1. Therefore, even if it is not possible to arrange the deburring tool TO3 in an orientation along the machining center line AX2 in the first place, or if another tool that is oriented along the machining center line AX2 is used, it is possible to deburr the peripheral portion of the hole that is oriented along the machining center line.

[0016] [Aspect 3] 5A, 5B, etc., the workpiece W1 may be cylindrical. The deburring tool TO3 may be attached to the tool rest 30 in a direction along the spindle center line AX1. The tool rest 30 may rotate the deburring tool TO3 about a deburring tool center line AX3 that is aligned with the spindle center line AX1. A maximum diameter TD of a portion of the deburring tool TO3 that is inserted inside the cylindrical workpiece W1 and that is centered on the deburring tool center line AX3 may be smaller than the inner diameter ID of the workpiece W1. In the above case, by inserting the deburring tool TO3, which rotates about the deburring tool center line AX3 along the spindle center line AX1, into the inside of the cylindrical workpiece W1, the peripheral portion C1p of the cross hole (C1) is cut inside the workpiece W1. When the cylindrical workpiece W1 has multiple cross holes (C1) oriented along the processing center line AX2, the above embodiment can reduce the amount of retraction of the deburring tool TO3 before and after deburring the inside of the workpiece W1, thereby shortening the workpiece processing cycle time.

[0017] [Aspect 4] 10, when viewed from the machining center line direction (X-axis direction), the peripheral portion C1p may include a first arc-shaped portion C21, a second arc-shaped portion C22, and a straight portion C23 connecting the first arc-shaped portion C21 to the second arc-shaped portion C22. As illustrated in FIG. 11, the control unit U1 may acquire the value (CD), the value (OD), and a value (LC) representing the center-to-center distance between the first arc-shaped portion C21 and the second arc-shaped portion C22. The control unit U1 may determine the translational axis coordinate (Zp) corresponding to the cutting position P1 and the rotation angle (Cp) corresponding to the cutting position P1 for each of the first arc-shaped portion C21, the second arc-shaped portion C22, and the straight portion C23, based on the value (CD), the value (OD), and the value (LC). The control unit U1 may control the relative positional relationship in the spindle center line direction (Z-axis direction) to the linear axis coordinate (Zp) so that the cutting position P1 changes along the first arc portion C21, the second arc portion C22, and the straight portion C23, and control the rotation of the spindle 11 to the rotation angle (Cp).

[0018] From the above, if the values ​​(CD), (OD), and the value (LC) representing the center-to-center distance between the first arc portion C21 and the second arc portion C22 can be obtained, the peripheral portion C1p of the oblong hole C2 can be cut with the deburring tool TO3. In this case, the control unit U1 only needs to control two axes: the linear axis (Z-axis) along the spindle center line AX1 and the rotational axis (C-axis) around the spindle center line AX1, rather than control in the three linear axes. Therefore, the above embodiment makes it easy to avoid interference between the deburring tool and the workpiece when deburring the peripheral portion of the oblong hole. Here, the diameter corresponding to the circumferential portion means the diameter of the first arcuate portion and the second arcuate portion. In this application, the terms "first", "second", etc. are terms for distinguishing between elements among a plurality of elements having similarities, and do not imply any order. These remarks also apply in the following aspects.

[0019] [Aspect 5] A ball end mill may be attached as the deburring tool TO3 to the tool rest 30. The tool rest 30 may rotate the ball end mill around a center line of the ball end mill (for example, a deburring tool center line AX3). The cutting position P1 of the peripheral portion C1p of the hole (C1) oriented along the machining center line AX2 in the workpiece W1 is controlled by the translatory axis coordinate (Zp) and the rotation angle (Cp). Because the deburring tool TO3 is a ball end mill, the peripheral portion C1p is cut so that the cutting amount is constant across the entire peripheral portion C1p. This allows the peripheral portion C1p of various holes (C1) to be deburred using a general-purpose ball end mill. Therefore, the above-described embodiment provides a preferred example of deburring the peripheral portion of a hole.

[0020] [Aspect 6] Furthermore, one embodiment of a control position determination method is a control position determination method for a machine tool (1) comprising: a spindle 11 that rotates together with a workpiece W1 around a spindle center line AX1; and a tool post 30 to which a deburring tool TO3 is attached that cuts a peripheral portion C1p of a hole (C1) in the workpiece W1 oriented along a machining center line AX2 that is perpendicular to the spindle center line AX1; the control position determination method controls the relative positional relationship between the spindle 11 and the tool post 30 along a linear axis (Z-axis) along the spindle center line AX1, and the rotation of the spindle 11 about a rotational axis (C-axis) about the spindle center line AX1, and includes the following steps (a1) and (a2), as illustrated in FIGS. 8 and 11 . (a1) A first step ST1 of acquiring a value (CD) representing the diameter corresponding to the peripheral portion C1p when the hole (C1) is viewed from the machining center line direction (X-axis direction) along the machining center line AX2, and a value (OD) representing the diameter corresponding to the circumference passing through the peripheral portion C1p and centered on the spindle center line AX1 in a cross section perpendicular to the spindle center line AX1. (a2) A second step ST2 of determining, based on the value (CD) and the value (OD), a linear axis coordinate (Zp) corresponding to the cutting position P1 on the linear axis (Z axis) and a rotation angle (Cp) corresponding to the cutting position P1 on the rotation axis (C axis) so that the cutting position P1 by the deburring tool TO3 changes along the circumferential portion C1p.

[0021] The above aspect can provide a control position determination method for a machine tool that can easily avoid interference between the deburring tool and the workpiece due to command errors when commanding movement of the deburring tool in three directions along the linear axis based on the workpiece.

[0022] (2) Specific examples of machine tool configurations: FIG. 1 is a front view that schematically illustrates the configuration of a lathe 1 as an example of a machine tool. FIG. 2 schematically illustrates the configuration of an electrical circuit of the lathe 1. FIGS. 3A to 3C schematically illustrate a cylindrical workpiece W1 having a cross hole C1. Here, FIG. 3A is a plan view of the workpiece W1, FIG. 3B is a vertical cross-sectional view taken at a position A1-A1 in FIG. 3A, and FIG. 3C is a horizontal cross-sectional view taken at a position A2-A2 in FIG. 3A. In FIG. 1, symbol D81 indicates the upward direction, symbol D82 indicates the downward direction, symbol D83 indicates the leftward direction, and symbol D84 indicates the rightward direction. These directions are based on the direction in which the lathe 1 shown in FIG. 1 is viewed. As shown in FIGS. 1 and 3, the control axes of the lathe 1 include the X-axis indicated by "X," the Y-axis indicated by "Y," the Z-axis indicated by "Z," and the C-axis indicated by "C." Here, the X-axis, Y-axis, and Z-axis are translational axes, and the C-axis is a rotational axis. The Z-axis direction is the direction of the spindle center line along the spindle center line AX1, which is the center of rotation of the workpiece W1, and is horizontal in FIG. 1. The X-axis direction is a direction perpendicular to the Z-axis and is horizontal in FIG. 1, but may also be a direction pointing up or down (upward direction D81 and downward direction D82). The Y-axis direction is a direction perpendicular to both the Z-axis and the X-axis. The C-axis is a rotational axis centered on the spindle center line AX1. The drawings referred to in this specification merely show examples for explaining aspects of the present application and do not limit the aspects of the present application. The explanation of the positional relationship of each part is merely an example. Therefore, reversing the left and right sides, reversing the direction of rotation, etc., are also included in the aspects of the present application. The identity of direction, position, etc. is not limited to strict agreement, and includes deviations from strict agreement due to error.

[0023] The lathe 1 is an NC lathe equipped with a headstock 10 having a spindle 11 with a gripper 12, a headstock drive unit 13, a support table 25 having mounting holes 26 for guide bushes 14, a tool rest 30, a tool rest drive unit 31, an NC device 70, and the like. Here, the headstock 10 collectively refers to a front headstock 15 and a back headstock 20, also called an opposing headstock. The front headstock 15 incorporates a front spindle 16 having a gripper 17, such as a collet. The back headstock 20 incorporates a back spindle 21 having a gripper 22, such as a collet. The spindle 11 collectively refers to the front spindle 16 and the back spindle 21, also called an opposing spindle. The gripper 12 collectively refers to the gripper 17 and the gripper 22. The headstock drive unit 13 collectively refers to a front headstock drive unit 18 that moves the front headstock 15 along the Z axis, and a back headstock drive unit 23 that moves the back headstock 20 at least along the Z axis. The lathe 1 shown in Figures 1 and 2 is a sliding spindle type lathe in which the front spindle 16 moves in the Z axis direction.

[0024] The front spindle 16 releasably grips a cylindrical workpiece W1 inserted from its rear end 16b using a gripper 17, and is rotatable together with the workpiece W1 around the spindle center line AX1. The front spindle 16 has a through-hole 16h that runs along the spindle center line AX1. If the unmachined workpiece W1 is a short material, the workpiece W1 may be fed from the front end 16a of the front spindle 16 to the gripper 17. The NC device 70 rotates the front spindle 16 around the spindle center line AX1 by driving the front spindle rotation drive unit 16c shown in FIG. 2, and controls the gripping state of the gripper 17 by driving the gripping actuator 17a shown in FIG. 2. The gripper 17 may be configured, for example, by a collet. The front headstock drive unit 18 moves the front headstock 15 in the Z-axis direction according to commands from the NC device 70. Therefore, the workpiece W1 held by the front spindle 16 moves in the Z-axis direction.

[0025] The front end 21a of the back spindle 21 faces the front end 16a of the front spindle 16. The back spindle 21 releasably grips the workpiece W1 in the middle of machining, which protrudes forward from the front end 16a of the front spindle 16, with a gripper 22, and is rotatable together with the workpiece W1 around the spindle center line AX1. The NC device 70 drives the back spindle rotation drive unit 21c shown in FIG. 2 to rotate the back spindle 21 around the spindle center line AX1, and drives the gripping actuator 22a shown in FIG. 2 to control the gripping state of the gripper 22. The gripper 22 can be configured, for example, with a collet. The back headstock drive unit 23 moves the back headstock 20 in the Z-axis direction and further in the X-axis or Y-axis direction in accordance with commands from the NC device 70.

[0026] The guide bush 14 is attached to the support base 25 while inserted in the mounting hole 26 of the support base 25, and supports the workpiece W1 protruding from the front spindle 16 toward the back spindle 21 (right direction D84) so ​​that it can slide in the Z-axis direction. The part of the workpiece W1 that protrudes from the guide bush 14 toward the back spindle 21 is machined by the tool TO1. When the guide bush is not in use, the front part of the front spindle 16 is inserted into the mounting hole 26, and the part of the workpiece W1 that protrudes from the front spindle 16 toward the back spindle 21 is machined by the tool TO1.

[0027] The tool rest 30 is equipped with a plurality of tools TO1 for machining a workpiece W1 held by at least one of the front spindle 16 and the back spindle 21. The tools TO1 include tools including cut-off tools, rotary tools such as rotary drills and end mills, and the like. Rotary tools include a cross tool TO2 shown in FIG. 3B and a deburring tool TO3 (e.g., a ball end mill). The tool rest 30 shown in FIG. 1 collectively refers to the comb tool rest 32 and the back machining tool rest 34. While only the deburring tool TO3 is shown in the back machining tool rest 34 shown in FIG. 1, the tool TO1 collectively refers to the tools attached to the tool rest 30, including the comb tool rest 32 and the back machining tool rest 34. Each tool rest 30 is equipped with a tool rotation drive unit 30c that rotates the rotary tool around the rotary tool centerline. The tool TO1 shown in FIG. 2 refers to a rotary tool. The tool rest 30 may include a turret tool rest or the like. The tool rest drive unit 31 shown in FIG. 1 collectively refers to the comb tool rest drive unit 33 and the back surface machining tool rest drive unit 35. The comb tool rest drive unit 33 moves the comb tool rest 32 along the X axis in accordance with commands from the NC device 70, and moves the comb tool rest 32 along the Y axis in accordance with commands from the NC device 70. The back surface machining tool rest drive unit 35 moves the back surface machining tool rest 34 along the Y axis in accordance with commands from the NC device 70. The tool rest 30 performs front machining of the workpiece W1 held by the front spindle 16 with the tool TO1, performs cut-off turning on the workpiece W1 held by both the front spindle 16 and the back spindle 21 after front machining, and performs back machining of the cut-off workpiece W1 held by the back spindle 21 with the tool TO1. In this manner, a product is formed from the workpiece W1.

[0028] As shown in FIG. 2, the NC device 70 is connected to an operation unit 80, a front headstock drive unit 18, a front spindle rotation drive unit 16c, a gripping actuator 17a, a back headstock drive unit 23, a back spindle rotation drive unit 21c, a gripping actuator 22a, a comb tool rest drive unit 33, a back machining tool rest drive unit 35, a tool rotation drive unit 30c, and the like. The front headstock drive unit 18, the back headstock drive unit 23, the comb tool rest drive unit 33, and the back machining tool rest drive unit 35 each include a servo motor and a servo amplifier (not shown), and change the position of the spindle 11 or the tool rest 30 according to commands from the NC device 70. The NC device 70 controls the position of the workpiece W1 or the tool TO1 by issuing commands to these elements (18, 23, 33, 35). The front spindle rotation drive unit 16c and the back spindle rotation drive unit 21c each include a servo motor (for example, a built-in motor) and a servo amplifier (not shown), and change the rotation angle of the spindle 11 according to commands from the NC device 70. The NC device 70 issues commands to these elements (16c, 21c) to control the rotation angle of the workpiece W1 about the spindle center line AX1.

[0029] The NC device 70 includes a CPU (Central Processing Unit) 71, which is a processor; a ROM (Read Only Memory) 72, which is a semiconductor memory; a RAM (Random Access Memory) 73, which is also a semiconductor memory; a clock circuit 74; and an I / F (Interface) 75 for peripheral elements (80, 18, 16c, 17a, 23, 21c, 22a, 33, 35, 30c). The ROM 72 stores a control program PR1 for interpreting and executing a machining program PR2. The ROM 72 may be a rewritable semiconductor memory. The RAM 73 stores the machining program PR2 created by an operator in a rewritable manner. The machining program is also called an NC program. The CPU 71 uses the RAM 73 as a work area and executes the control program PR1 stored in the ROM 72 to realize the functions of the NC device 70.

[0030] The operation unit 80 includes an input unit 81 and a display unit 82, and functions as a user interface for the NC device 70. The input unit 81 is configured, for example, by keys or a touch panel for receiving operation inputs from an operator. The display unit 82 is configured, for example, by a display for displaying the contents of various settings received as operation inputs from the operator and various information related to the lathe 1. The operator can store the machining program PR2 in the RAM 73 using the operation unit 80 or an external computer (not shown).

[0031] In this specific example, the NC device 70, the headstock drive unit 13 (front headstock drive unit 18 and rear headstock drive unit 23), and the spindle rotation drive units (16c, 21c) constitute a control unit U1. The NC device 70 and the headstock drive unit 13 control the relative positional relationship between the spindle 11 and the tool rest 30 in the Z axis along the spindle center line AX1. The NC device 70 and the spindle rotation drive units (16c, 21c) control the rotation of the spindle 11 in the C axis about the spindle center line AX1.

[0032] 3A to 3C has a cylindrical shape with a hollow portion W1h that runs through along the spindle center line AX1. Therefore, the workpiece W1 has an outward-facing outer peripheral surface W1o and an inward-facing inner peripheral surface W1i. A cross tool TO2, a rotary tool, is attached to the tool rest 30 for forming a cross hole C1 in the workpiece W1, connecting the outer peripheral surface W1o to the hollow portion W1h. The cross tool TO2 can be a drill or an end mill. The NC device 70 may control the drill as the cross tool TO2 to first form an opening in the workpiece W1, and then the end mill as the cross tool TO2 to form the cross hole C1. The cross tool TO2 shown in FIG. 3B is positioned with its longitudinal direction aligned with the X-axis and is rotatable around a rotary tool center line AX4 aligned with the X-axis. The rotary tool center line AX4 is aligned with the machining center line AX2 of the cross hole C1 and is perpendicular to the spindle center line AX1 in the XZ plane viewed from the Y-axis direction, as shown in FIG. 3B. The cross hole C1 formed by the cross tool TO2 is a hole that penetrates the workpiece W1 so as to connect the outer peripheral surface W1o to the inner peripheral surface W1i, centered on the machining center line AX2 along the X-axis, and can be said to be a hole oriented along the machining center line AX2, or a hole centered on the machining center line AX2. In the plan view shown in Figure 3A, the cross hole C1 is circular, and the center C1o of the cross hole C1 is on the spindle center line AX1.

[0033] When a cross hole C1 is formed in a workpiece W1 using the cross tool TO2, burrs may occur on the ridge line of the peripheral portion C1p of the cross hole C1. The term "ridge line" is used because burrs may occur on the peripheral portion C1p of both the outer peripheral surface W1o and the inner peripheral surface W1i. While a dedicated tool can be used to remove the burrs, in this example, a general-purpose deburring tool TO3, as shown in FIG. 4B, is attached to the tool rest 30, e.g., the back surface machining tool rest 34. The deburring tool TO3 shown in FIG. 4B is a ball end mill that can rotate around the deburring tool center line AX3 and has a spherical cutting part TO3b at its tip, which becomes spherical upon rotation. The tool rotation drive unit 30c of the tool rest 30 rotates the deburring tool TO3 around the deburring tool center line AX3. While the orientation of the deburring tool center line AX3 may be aligned with the machining center line AX2, in this example, it is aligned with the spindle center line AX1, as shown in FIG. 4B. First, an example will be described in which the peripheral portion C1p of the cross hole C1 on the outer peripheral surface W1o of the workpiece W1 is cut by the deburring tool TO3.

[0034] Fig. 4A shows a schematic diagram of the cutting position P1 varying along the periphery C1p of the cross hole C1. Fig. 4B is a longitudinal cross-sectional view corresponding to the position A1-A1 in Fig. 3A, showing a schematic diagram of the deburring tool TO3 oriented along the spindle center line AX1 and positioned on the outer peripheral surface W1o of the cylindrical workpiece W1. Fig. 4C is a transverse cross-sectional view corresponding to the position A2-A2 in Fig. 3A, showing a schematic diagram of the spherical cutting portion TO3b positioned on the outer peripheral surface W1o. In FIG. 4A, the cutting position P1 of the peripheral portion C1p by the spherical cutting part TO3b changes from an initial position P0 on the spindle center line AX1 to a full rotation around the peripheral portion C1p in a clockwise direction. Of course, the cutting position P1 may also change to a full rotation around the peripheral portion C1p in a counterclockwise direction. Here, the angle between the line segment connecting the center C1o to the initial position P0 and the line segment connecting the center C1o to the cutting position P1 is defined as θyz. In this example, the NC device 70 rotates the deburring tool TO3 as shown in FIG. 4B, moves the workpiece W1 back and forth in the Z-axis direction to align it with the cutting position P1, and then rotates the workpiece W1 to align it with the cutting position P1 as shown in FIG. 4C. This removes the burr from the peripheral portion C1p of the cross hole C1 on the outer peripheral surface W1o of the workpiece W1. Because the deburring tool TO3 is a ball end mill, the ridge of the peripheral portion C1p is cut with a consistent cutting amount across the entire peripheral portion C1p. Therefore, the burr removal process of the peripheral portion C1p can be performed using a general-purpose ball end mill instead of a dedicated tool.

[0035] Fig. 5A is a longitudinal cross-sectional view corresponding to the position A1-A1 in Fig. 3A, and illustrates a schematic diagram of the deburring tool TO3 oriented along the spindle center line AX1 and disposed on the inner peripheral surface W1i of the cylindrical workpiece W1. Fig. 5B is a transverse cross-sectional view corresponding to the position A2-A2 in Fig. 3A, and illustrates a schematic diagram of the spherical cutting part TO3b disposed on the inner peripheral surface W1i. Note that the cutting position P1 of the peripheral portion C1p by the spherical cutting part TO3b changes from the initial position P0 on the spindle center line AX1 to complete one revolution clockwise (or counterclockwise) on the peripheral portion C1p, as shown in Fig. 4A. As shown in FIG. 5B, the maximum diameter TD of the portion of the deburring tool TO3 inserted into the cylindrical workpiece W1, centered on the deburring tool centerline AX3, is smaller than the inner diameter ID of the workpiece W1. Therefore, the NC device 70 rotates the deburring tool TO3 as shown in FIG. 5A, reciprocates the workpiece W1 in the Z-axis direction to align it with the cutting position P1, and then rotates the workpiece W1 to align it with the cutting position P1 as shown in FIG. 5B. This removes the burr from the circumferential portion C1p of the cross hole C1 on the inner circumferential surface W1i of the workpiece W1. Because the deburring tool TO3 is a ball end mill, the ridge of the circumferential portion C1p is cut so that the cutting amount is consistent across the entire circumferential portion C1p. Therefore, deburring of the circumferential portion C1p can be performed using a general-purpose ball end mill rather than a dedicated tool.

[0036] Depending on the lathe, it may not be possible to arrange the deburring tool TO3 in an orientation along the machining center line AX2. For example, as shown in FIG. 1, if the orientation of the tool TO1 attached to the back machining tool post 34 is limited to an orientation along the spindle center line AX1 and it is desired to attach the deburring tool TO3 to the back machining tool post 34, the deburring tool TO3 will not be oriented along the machining center line AX2. Furthermore, even if the tool TO1 can be arranged on the tool post 30 in an orientation along the machining center line AX2, it may not be possible to attach the deburring tool TO3 if another tool is attached to the tool attachment location on the tool post 30 that is oriented along the machining center line AX2. The deburring process in this example can be easily performed with the deburring tool TO3 oriented along the spindle center line AX1.

[0037] Suppose we need to remove burrs remaining on the peripheries C1p of multiple cross holes C1 on the inner surface W1i of a workpiece W1. If the orientation of the deburring tool TO3 is along the machining center line AX2, when changing the cross hole C1 to be deburred on the inner surface W1i, the deburring tool TO3 must be significantly retracted toward the machining center line. This is because, after inserting the deburring tool TO3 into a certain cross hole C1 to remove the burrs on the inner surface W1i, the deburring tool TO3 must be retracted from the cross hole C1 before inserting the deburring tool TO3 into another cross hole C1 to remove the burrs on the inner surface W1i. The greater the retraction distance of the deburring tool TO3, the longer the workpiece machining cycle time. On the other hand, if the orientation of the deburring tool TO3 is along the spindle center line AX1, the amount of retraction of the deburring tool TO3 is reduced when changing the cross hole C1 whose inner surface W1i is to be deburred. This is because, after inserting the deburring tool TO3 into the hollow portion W1h of the workpiece W1 to remove the burr from the inner surface W1i of one cross hole C1, the deburring tool TO3 can be removed from the inner surface W1i of another cross hole C1 while still inserted in the hollow portion W1h. The reduced amount of retraction of the deburring tool TO3 shortens the workpiece machining cycle time.

[0038] 4A in the three directions of the X-axis, Y-axis, and Z-axis. This is because the ridge line of the peripheral portion C1p of the cross hole C1 is on the outer peripheral surface W1o or inner peripheral surface W1i of the workpiece W1, and therefore, as the cutting position P1 changes, not only the Y-axis coordinate and Z-axis coordinate but also the X-axis coordinate changes. If the three-dimensional coordinates (X-axis coordinate, Y-axis coordinate, and Z-axis coordinate) of the cutting position P1 are not calculated properly, interference between the deburring tool TO3 and the workpiece W1 may occur, and the peripheral portion C1p may not be cut properly. In this example, the above mentioned possibility is avoided by controlling the relative Z-axis coordinate of the deburring tool TO3 and the C-axis angle of the workpiece W1 based on parameters that are easily understood by the operator.

[0039] First, referring to FIG. 6, an example of controlling the cutting position P1 when cutting the circumferential portion C1p of the cross hole C1 on the outer peripheral surface W1o of the workpiece W1 will be described. FIG. 6 schematically shows an example of determining the Z-axis coordinate Zp and C-axis angle Cp corresponding to the cutting position P1 based on the diameter value (CD) of the cross hole C1 and the outer diameter value (OD) of the workpiece W1. In FIG. 6, a plan view 101 of the workpiece W1 is shown at the top, a cross-sectional view 102 of the workpiece W1 is shown below the plan view 101, and calculation formulas for the Z-axis coordinate Zp and the C-axis angle Cp are shown at the bottom. In the plan view 101, the upward direction is the +Z direction in the Z-axis direction, the downward direction is the -Z direction in the Z-axis direction, the rightward direction is the +Y direction in the Y-axis direction, and the leftward direction is the -Y direction in the Y-axis direction. In the cross-sectional view 102, the upward direction is the +X direction in the X-axis direction, the downward direction is the -X direction in the X-axis direction, the rightward direction is the +Y direction in the Y-axis direction, and the leftward direction is the -Y direction in the Y-axis direction.

[0040] The value CD represents the diameter corresponding to the peripheral portion C1p when the cross hole C1 is viewed from the X-axis direction, which is the machining center line direction. The value OD represents the diameter corresponding to the circumference, i.e., the outer peripheral surface W1o, of a circle centered on the spindle center line AX1 and passing through the peripheral portion C1p in a cross section (see cross-sectional view 102) that passes through the center C1o of the cross hole C1 and is perpendicular to the spindle center line AX1. The angle θyz is the angle between the line segment connecting the center C1o to the initial position P0 and the line segment connecting the center C1o to the cutting position P1. When the cutting position P1 is the initial position P0, the angle θyz is 0° or 360°, and the C-axis angle Cp is 0°. Figure 6 also shows point B corresponding to θyz = 90° and point A corresponding to θyz = 270°. The rate of change of the angle θyz is determined based on, for example, the feed rate. The angle θxy is the angle formed by the line segment connecting the center point O corresponding to the main shaft center line AX1 to point A and the line segment connecting the center point O to point B in the cross-sectional view 102.

[0041] The Z-axis coordinate Zp is a linear axis coordinate corresponding to the cutting position P1 that changes along the periphery C1p on the Z axis. When the tool rest 30 to which the deburring tool TO3 is attached does not move in the Z-axis direction, the Z-axis coordinate Zp corresponds to the coordinate on the Z axis of the workpiece W1 held by the spindle 11. The Z-axis coordinate Zp is expressed by the following equation using the diameter value CD corresponding to the periphery C1p and the angle θyz. Zp = (CD / 2) × cosθyz … (1) From the above, the Z-axis coordinate Zp corresponding to the cutting position P1 that changes along the periphery C1p is determined based on the value CD.

[0042] In the cross-sectional view 102, the radius value r corresponding to the outer circumferential surface W1o is half the value OD. r=OD / 2 …(2) The radius value CD / 2 corresponding to the value CD is expressed by the following equation using the radius value r and the angle θxy formed by the line segment between OA and the line segment between OB. CD / 2=r×sin(θxy / 2) …(3) From the above equation (3), sin(θxy / 2)=CD / 2r, and therefore the angle θxy is expressed by the following equation. θxy=2×arcsin(CD / 2r) …(4) "arcsin" is the inverse function of "sin" -1 " is also written as ". According to the above formula (4), the angle θxy is a fixed value calculated from the values ​​CD and OD.

[0043] The C-axis angle Cp is a rotation angle corresponding to the cutting position P1 that changes along the circumferential portion C1p on the C-axis, and is the angle on the C-axis of the workpiece W1 gripped by the spindle 11. Since the C-axis angle Cp changes within the range of -(θxy / 2)≦Cp≦+(θxy / 2), it can be expressed by the following equation using the angle θxy formed by the line segment between OA and the line segment between OB, and the angle θyz corresponding to the cutting position P1. Cp=(θxy / 2)×sinθyz =arcsin(CD / 2r)×sinθyz…(5) From the above, the C-axis angle Cp corresponding to the cutting position P1 that changes along the circumferential portion C1p is determined based on the values ​​CD and OD.

[0044] As illustrated in Figure 7, the same concept can be applied when cutting the peripheral portion C1p of the cross hole C1 on the inner peripheral surface W1i of the workpiece W1. Figure 7 schematically shows an example of determining the Z-axis coordinate Zp and C-axis angle Cp corresponding to the cutting position P1 based on the diameter value (CD) of the cross hole C1 and the inner diameter value (OD) of the workpiece W1. In Figure 7, a plan view 101 of the workpiece W1 is shown at the top, a cross-sectional view 102 of the workpiece W1 is shown below the plan view 101, and calculation formulas for the Z-axis coordinate Zp and the C-axis angle Cp are shown at the bottom.

[0045] The value CD is the same as when the deburring surface is the outer peripheral surface W1o, and represents the diameter corresponding to the peripheral portion C1p when the cross hole C1 is viewed from the X-axis direction. The value OD represents the diameter corresponding to the inner peripheral surface W1i, i.e., the circumference centered on the spindle center line AX1 and passing through the peripheral portion C1p in a cross section (see cross section 102) that passes through the center C1o of the cross hole C1 and is perpendicular to the spindle center line AX1. FIG. 7 also shows point B corresponding to θyz = 90° and point A corresponding to θyz = 270°. The angle θxy is the angle between the line segment connecting point A and center point O corresponding to the spindle center line AX1 in cross section 102, and the line segment connecting point O and point B.

[0046] The Z-axis coordinate Zp is the same as when the deburring surface is the outer circumferential surface W1o, and is expressed by the following equation using the diameter value CD corresponding to the circumferential portion C1p and the angle θyz. Zp=(CD / 2)×cosθyz …(6) In the cross-sectional view 102, the radius value r corresponding to the inner circumferential surface W1i is half the value OD. r=OD / 2 …(7) The radius value CD / 2 corresponding to the value CD is expressed by the following equation using the radius value r and the angle θxy formed by the line segment between OA and the line segment between OB. CD / 2=r×sin(θxy / 2) …(8) From the above equation (8), the angle θxy is expressed by the following equation. θxy=2×arcsin(CD / 2r) …(9) Since the C-axis angle Cp varies within the range of -(θxy / 2)≦Cp≦+(θxy / 2), it can be expressed by the following equation using the angle θxy between the line segment between OA and the line segment between OB, and the angle θyz corresponding to the cutting position P1. Cp=(θxy / 2)×sinθyz =arcsin(CD / 2r)×sinθyz…(10)

[0047] As described above, by determining the Z-axis coordinate Zp and C-axis angle Cp based on the values ​​CD and OD, deburring can be controlled by two-axis control of the Z and C axes. Therefore, by preparing a deburring command CM1 (see Figure 8) suitable for two-axis control deburring, deburring can be performed without commanding the cutting position P1 on the three axes of the X, Y, and Z axes.

[0048] (3) Examples of deburring processing: Fig. 8 shows a schematic example of the deburring process performed by the NC device 70. Fig. 8 also shows a deburring command CM1 included in the processing program PR2. When the NC device 70 shown in Fig. 2 reads the deburring command CM1 from the processing program PR2, it starts the deburring process.

[0049] The deburring command CM1 shown in Figure 8 has the format "G*** D** X** F**." The argument "***" after G indicates the number of the deburring command CM1. The argument "**" after D indicates the outer or inner diameter value OD (mm) of the workpiece W1. The argument "**" after X indicates the diameter value CD (mm) corresponding to the periphery C1p when viewing the cross hole C1 from the X-axis direction. The argument "**" after F indicates the feed rate per minute distributed between the movement speed of the workpiece W1 along the Z-axis and the rotation speed of the workpiece W1 on the C-axis. When the cutting position P1 makes one revolution on the periphery C1p, the Z-axis coordinate Zp moves from +CD / 2 to -CD / 2 and then back to +CD / 2, so the total movement distance of the workpiece W1 along the Z-axis is 2 x CD (mm). Furthermore, the C-axis angle Cp changes from 0° to +θxy / 2, passes through -θxy / 2, and then returns to 0°, so the total amount of rotation of the workpiece W1 on the C-axis is 2×θxy (deg). For example, assuming that a rotation amount of 1° corresponds to a movement distance of 1 mm, the time (T (min)) required for the cutting position P1 to make one revolution on the circumferential portion C1p can be calculated using the following formula. T = {(2 × CD) 2 +(2×θxy) 2} 1 / 2 / F =2×(CD 2 +θxy 2 ) 1 / 2 / F …(11) If the time that has elapsed since the cutting position P1 started to move from the initial position P0 is t (min), the angle θyz (deg) corresponding to the cutting position P1 can be calculated, for example, by the following formula. θyz=360×(t / T) …(12) Therefore, by applying the angle θyz corresponding to the cutting position P1 that changes along the circumferential portion C1p to the above equations (1) to (10) together with the values ​​CD and OD, the Z-axis coordinate Zp and the C-axis angle Cp can be determined.

[0050] If it is desired to reduce the cutting amount of the peripheral portion C1p in consideration of the size of the spherical cutting portion TO3b of the deburring tool TO3, the command value of the value CD may be set slightly smaller than the actual diameter of the peripheral portion C1p. Conversely, if it is desired to increase the cutting amount of the peripheral portion C1p, the command value of the value CD may be set slightly larger than the actual diameter of the peripheral portion C1p. Furthermore, the cutting amount of the peripheral portion C1p can be adjusted by adding an argument specifying an offset amount for adjusting the cutting amount of the peripheral portion C1p to the deburring processing command CM1.

[0051] A control position determination method for a machine tool is carried out after the deburring process shown in Fig. 8 is performed. The control position determination method of this specific example includes the following steps (a1), (a2), and (a3). (a1) A first step ST1 (corresponding to step S102) acquires a value CD representing the diameter corresponding to the peripheral portion C1p when the hole (C1) is viewed from the machining center line direction (X-axis direction), and a value OD representing the diameter corresponding to the circumference passing through the peripheral portion C1p and centered on the spindle center line AX1 in a cross section perpendicular to the spindle center line AX1. (a2) A second process ST2 (corresponding to steps S106 to S108) determines the linear axis coordinate (Zp) corresponding to the cutting position P1 on the linear axis (Z axis) and the rotation angle (Cp) corresponding to the cutting position P1 on the rotation axis (C axis) based on the values ​​CD and OD so that the cutting position P1 by the deburring tool TO3 changes along the circumferential portion C1p. (a3) A third process ST3 (corresponding to step S110) controls the relative positional relationship between the spindle 11 and the tool post 30 in the spindle center line direction (Z-axis direction) to the linear axis coordinate (Zp) and controls the rotation of the spindle 11 to the rotation angle (Cp) so that the cutting position P1 changes along the peripheral portion C1p. Hereinafter, the description of "step" will be omitted.

[0052] When the deburring process starts, the NC device 70 acquires arguments for the deburring process command CM1 (S102). This acquires a diameter value CD corresponding to the circumferential portion C1p as viewed from the X-axis direction and a diameter value OD corresponding to the circumference passing through the circumferential portion C1p as viewed from the Z-axis direction. Next, the NC device 70 controls the Z-axis coordinate Zp and the C-axis angle Cp to the initial position P0 (S104). For example, the NC device 70 controls the deburring tool TO3 to rotate around the deburring tool center line AX3, sets the Z-axis coordinate of the workpiece W1 to Zp = +CD / 2, controls the C-axis angle of the workpiece W1 to 0°, and controls the spherical cutting portion TO3b of the deburring tool TO3 to abut the initial position P0 of the circumferential portion C1p. Furthermore, since the rotation of the deburring tool TO3 only needs to start before the spherical cutting part TO3b hits the initial position P0, it may start after the coordinate of the workpiece W1 on the Z axis is controlled to Zp = +CD / 2, or after the C-axis angle of the workpiece W1 is controlled to 0°.

[0053] Thereafter, the NC device 70 determines the angle θyz corresponding to the cutting position P1 based on the feed rate F in accordance with the above formulas (11) and (12) (S106). Furthermore, the NC device 70 determines the Z-axis coordinate Zp and the C-axis angle Cp at the angle θyz based on the values ​​CD and OD in accordance with the above formulas (1) to (10) (S108). As a result of the above, the Z-axis coordinate Zp corresponding to the cutting position P1 that changes along the periphery C1p on the Z axis, and the C-axis angle Cp corresponding to the cutting position P1 on the C axis are determined.

[0054] After determining the Z-axis coordinate Zp and the C-axis angle Cp, the NC device 70 controls the relative positional relationship between the workpiece W1 and the deburring tool TO3 to the Z-axis coordinate Zp, and controls the workpiece W1 to the C-axis angle Cp around the spindle center line AX1 (S110). Thereafter, the NC device 70 determines whether the cutting position P1 has returned to the initial position P0 (S112). If the cutting position P1 has not returned to the initial position P0, the NC device 70 repeats the processes of S106 to S112. If the cutting position P1 has returned to the initial position P0, the NC device 70 ends the deburring process. As a result of the above, the NC device 70 controls the relative positional relationship between the spindle 11 and the tool post 30 in the Z-axis direction to the Z-axis coordinate Zp so that the cutting position P1 changes along the periphery C1p of the cross hole C1, and controls the rotation of the spindle 11 to the C-axis angle Cp.

[0055] Fig. 9 shows a schematic example of Z-axis movement and C-axis rotation of the workpiece W1 during deburring. The left side of Fig. 9 shows a plan view 101 of the workpiece W1 in states 111 to 114, and the right side of Fig. 9 shows a cross-sectional view 102 of the workpiece W1 in states 111 to 114. In state 111, where cutting position P1 is at the initial position P0, the Z-axis coordinate Zp is +CD / 2, so the workpiece W1 is at a position where it has moved a distance of CD / 2 in the -Z direction, and the C-axis angle Cp is 0°. After that, when cutting position P1 moves clockwise along the periphery C1p in the plan view 101, the Z-axis coordinate Zp decreases, so the workpiece W1 moves in the +Z direction, and the C-axis angle Cp increases toward +θxy / 2.

[0056] When the cutting position P1 reaches state 112 where θyz = 90°, the Z-axis coordinate Zp becomes 0 and the C-axis angle Cp becomes +θxy / 2. After that, the Z-axis coordinate Zp decreases, so the workpiece W1 moves in the +Z direction and the C-axis angle Cp decreases toward 0°. When cutting position P1 reaches state 113 where θyz = 180°, the Z-axis coordinate Zp becomes -CD / 2, so the workpiece W1 moves a distance of CD / 2 in the +Z direction, and the C-axis angle Cp becomes 0°. After that, the Z-axis coordinate Zp increases, so the workpiece W1 moves in the -Z direction, and the C-axis angle Cp decreases toward -θxy / 2.

[0057] When the cutting position P1 reaches state 114 where θyz = 270°, the Z-axis coordinate Zp becomes 0 and the C-axis angle Cp becomes -θxy / 2. After that, as the Z-axis coordinate Zp increases, the workpiece W1 moves in the -Z direction and the C-axis angle Cp increases toward 0°. When the cutting position P1 reaches θyz=360°, the state returns to state 111.

[0058] As a result of the above, the ridge line of the peripheral portion C1p of the cross hole C1 is cut along the entire circumference, and burrs on the outer peripheral surface W1o and the inner peripheral surface W1i are removed. Through the above-described deburring process, burrs formed on the periphery C1p of the cross hole C1 are removed based on the value CD representing the diameter of the cross hole C1 as viewed from the machining centerline direction and the value OD representing the outer or inner diameter of the workpiece W1 as viewed from the spindle centerline direction. The NC device 70 controls only two axes: the Z axis along the spindle centerline AX1 and the C axis around the spindle centerline AX1, rather than the three axes of the X, Y, and Z axes. Since the C-axis angle Cp of the workpiece W1 is controlled in accordance with the cutting position P1, and the Z-axis coordinate Zp of the deburring tool TO3 relative to the workpiece W1 is controlled in accordance with the cutting position P1, interference between the deburring tool TO3 and the workpiece W1 is easily avoided. Therefore, interference between the deburring tool TO3 and the workpiece W1 due to, for example, a command error when commanding the movement of the deburring tool TO3 in the direction of the linear axis 3 relative to the workpiece W1 can be easily avoided.

[0059] (4) Variation: The present invention can be modified in various ways. For example, the machine tool is not limited to a lathe, but may be a machining center or the like. The lathe 1 may be a fixed spindle type lathe in which the front spindle 16 does not move in the Z-axis direction. At least a part of the processing in S102 to S108 and S112 shown in FIG. 8 may be performed by a device other than the lathe 1, such as an external computer. The argument (OD) of D in the deburring processing command CM1 is not limited to a diameter value and may be a radius value, etc. The argument (CD) of X in the deburring processing command CM1 is not limited to a diameter value and may be a radius value, etc.

[0060] The hole to be deburred is not limited to the cross hole C1, but may be a bottomed hole recessed from the outer surface W1o to halfway through the workpiece W1 along the machining center line AX2, or a horizontal hole intended for a solid workpiece. A hole such as a cross hole C1 when viewed from the machining center line direction may have any shape that has a portion that can be called a diameter, and may be an elongated hole C2 that includes a straight portion in addition to an arc-shaped portion, as shown in Figure 10.

[0061] 10 shows a schematic example of determining the Z-axis coordinate Zp and C-axis angle Cp corresponding to the cutting position P1 based on the diameter value (CD) of the slotted hole C2, the inner diameter value (OD) of the workpiece W1, and the center-to-center distance value (LC) of the arc portions. In FIG. 10, a plan view 101 of the workpiece W1 is shown at the top, a cross-sectional view 102 of the workpiece W1 is shown below the plan view 101, and calculation formulas for the Z-axis coordinate Zp and the C-axis angle Cp are shown at the bottom. As shown in plan view 101, the peripheral portion C1p of the long hole C2, when viewed from the X-axis direction, includes a first arc portion C21 having an arc shape in the range Zp>0, a second arc portion C22 having an arc shape in the range Zp<0, and a straight portion C23 connecting the first arc portion C21 to the second arc portion C22.

[0062] The value CD represents the diameter corresponding to the circumferential portion C1p when the first arc-shaped portion C21 and the second arc-shaped portion C22 are viewed from the X-axis direction. The value OD represents the diameter corresponding to the circumference, i.e., the inner circumferential surface W1i, passing through the circumferential portion C1p and centered on the spindle centerline AX1 in a cross section (see cross-sectional view 102) perpendicular to the spindle centerline AX1 between the centers C1o. FIG. 10 also shows point B corresponding to θyz=90° in the first arc-shaped portion C21, point D corresponding to θyz=90° in the second arc-shaped portion C22, point C corresponding to θyz=270° in the second arc-shaped portion C22, and point A corresponding to θyz=270° in the first arc-shaped portion C21. FIG. 10 also shows a value LC representing the center-to-center distance between the center C1o corresponding to the first arc-shaped portion C21 and the center C1o corresponding to the second arc-shaped portion C22.

[0063] When the cutting position P1 is on the first arcuate portion C21, the Z-axis coordinate Zp is expressed by the following equation using the diameter value CD corresponding to the circumferential portion C1p, the angle θyz, and the value LC representing the center-to-center distance. Zp=(CD / 2)×cosθyz+(LC / 2) …(13) When the cutting position P1 is located on the second arcuate portion C22, it is expressed by the following formula. Zp=(CD / 2)×cosθyz-(LC / 2) …(14) When the cutting position P1 is on the first arc portion C21 or the second arc portion C22, the radius value CD / 2 corresponding to the value CD is expressed by the following formula using the radius value r=OD / 2 and the angle θxy. CD / 2=r×sin(θxy / 2) …(15) From the above equation (15), the angle θxy is expressed by the following equation. θxy=2×arcsin(CD / 2r) …(16) Since the C-axis angle Cp varies within the range of -(θxy / 2)≦Cp≦+(θxy / 2), it can be expressed by the following equation using the angle θxy and the angle θyz corresponding to the cutting position P1. Cp=(θxy / 2)×sinθyz =arcsin(CD / 2r)×sinθyz…(17)

[0064] From the above, by determining the Z-axis coordinate Zp and C-axis angle Cp for each of the first arc portion C21, the second arc portion C22, and the straight portion C23 based on the values ​​CD, OD, and the value LC representing the center-to-center distance, it is possible to control the deburring process by two-axis control of the Z and C axes. By preparing a deburring process command CM2 (see Figure 11) suitable for this two-axis control deburring process, it is possible to perform the deburring process without commanding the cutting position P1 on the three axes of the X, Y, and Z axes.

[0065] Fig. 11 shows a schematic example of the deburring process of the peripheral portion C1p of the elongated hole C2. Fig. 11 also shows a deburring command CM2 included in the machining program PR2. When the NC device 70 shown in Fig. 2 reads the deburring command CM2 from the machining program PR2, it starts the deburring process. In the deburring process shown in Fig. 11, S202 corresponds to the first step ST1, S206 to S210 correspond to the second step ST2, and S212 corresponds to the third step ST3. The deburring processing command CM2 shown in Fig. 11 has "L**" added to the deburring processing command CM1 shown in Fig. 8. The argument "**" after L indicates the value LC (mm) that represents the center-to-center distance between the arc portions (C21, C22).

[0066] When the cutting position P1 is on the straight line portion C23, the speed at which the cutting position P1 moves in the Z-axis direction is, for example, a feed rate F. The time (Tc (min)) required for the cutting position P1 to move on the arc portions (C21, C22) can be calculated using the following formula. Tc = {(2 × CD) 2 +(2×θxy) 2} 1 / 2 / F =2×(CD 2 +θxy 2 ) 1 / 2 / F …(18) If the time it takes for cutting position P1 to start moving from the initial position P0 and remain on the arc portion (C21, C22) is tc (min), the angle θyz (deg) corresponding to cutting position P1 can be calculated, for example, using the following formula. θyz=360×(tc / Tc) …(19) Therefore, by applying the angle θyz corresponding to the cutting position P1, which changes along the circumferential portion C1p, together with the values ​​CD, OD, and LC to the above equations (13) to (17), the Z-axis coordinate Zp and C-axis angle Cp when the cutting position P1 is on the arc portion (C21, C22) can be determined. When the cutting position P1 is on the straight portion C23, the C-axis angle Cp is +θxy / 2 or -θxy / 2, and the Z-axis coordinate Zp changes according to the feed rate F.

[0067] When the deburring process starts, the NC device 70 acquires arguments of the deburring process command CM2 (S202). This acquires the diameter CD corresponding to the first arc portion C21 and the second arc portion C22 as viewed from the X-axis direction, the diameter OD corresponding to the circumference passing through the first arc portion C21 or the second arc portion C22 as viewed from the Z-axis direction, and a value LC representing the center-to-center distance between the arc portions (C21, C22). Next, the NC device 70 controls the Z-axis coordinate Zp and the C-axis angle Cp to the initial position P0 (S204). For example, the NC device 70 controls the deburring tool TO3 to rotate around the deburring tool center line AX3, aligns the Z-axis coordinate of the workpiece W1 with Zp = +(CD / 2) + (LC / 2), controls the C-axis angle of the workpiece W1 to 0°, and controls the spherical cutting portion TO3b of the deburring tool TO3 to abut the initial position P0 of the peripheral portion C1p.

[0068] Thereafter, the NC device 70 determines the angle θyz corresponding to the cutting position P1 based on the feed rate F in accordance with the above equations (18) and (19) (S206). When the cutting position P1 is on the arc portion (C21, C22), the NC device 70 determines the Z-axis coordinate Zp and the C-axis angle Cp at the angle θyz based on the values ​​CD, OD, and LC in accordance with the above equations (13) to (17) (S208). When the cutting position P1 is on the straight portion C23, the NC device 70 determines the Z-axis coordinate Zp based on the feed rate F (S210). From the above, for each of the first arc portion C21, the second arc portion C22, and the straight portion C23, the Z-axis coordinate Zp corresponding to the cutting position P1 that changes along the circumferential portion C1p on the Z-axis, and the C-axis angle Cp corresponding to the cutting position P1 on the C-axis are determined.

[0069] After determining the Z-axis coordinate Zp and the C-axis angle Cp, the NC device 70 controls the relative positional relationship between the workpiece W1 and the deburring tool TO3 to the Z-axis coordinate Zp, and controls the workpiece W1 to the C-axis angle Cp around the spindle center line AX1 (S212). Thereafter, the NC device 70 determines whether the cutting position P1 has returned to the initial position P0 (S214). If the cutting position P1 has not returned to the initial position P0, the NC device 70 repeats the processes of S206 to S214. If the cutting position P1 has returned to the initial position P0, the NC device 70 ends the deburring process. As described above, the NC device 70 controls the relative positional relationship between the spindle 11 and the tool post 30 in the Z-axis direction to the Z-axis coordinate Zp so that the cutting position P1 changes along the periphery C1p of the oblong hole C2, and controls the rotation of the spindle 11 to the C-axis angle Cp. Therefore, in the example shown in Figures 10 and 11, interference between the deburring tool TO3 and the workpiece W1 can be easily avoided during deburring of the periphery C1p of the oblong hole C2.

[0070] Although the above-described oblong hole C2 is a vertically elongated hole whose size along the Z axis is larger than its size around the C axis, the oblong hole may also be a horizontally elongated hole whose size along the C axis is larger than its size along the Z axis. When the oblong hole is a horizontally elongated hole, the NC device 70 can perform control to change the C-axis angle Cp without changing the Z-axis coordinate Zp in the part of the periphery that is not an arc portion. Furthermore, the diameter corresponding to the first arc portion and the diameter corresponding to the second arc portion may be different. In this case, the NC device 70 may perform control to change the Z-axis coordinate Zp at a constant speed and change the C-axis angle Cp at a constant rotation speed in the portion of the circumferential portion that connects the arc portions.

[0071] (5) Conclusion: As described above, according to the present invention, it is possible to provide, through various aspects, configurations that can easily avoid interference between the deburring tool and the workpiece due to a command error when commanding the movement of the deburring tool in the directions of the linear axes 3 relative to the workpiece. Of course, even in an aspect that consists only of the constituent features of the independent claims, the basic actions and effects described above can be obtained. Furthermore, it is possible to implement configurations in which the components disclosed in the above examples are substituted with each other or the combination is changed, or configurations in which the components disclosed in the publicly known techniques and the above examples are substituted with each other or the combination is changed, etc. The present invention also includes these configurations. [Explanation of symbols]

[0072] 1...Lathe (example of machine tool), 10...headstock, 11...main spindle, 12...gripping section, 13...headstock drive section, 15... front headstock, 16... front spindle, 16c... front spindle rotation drive unit, 20... rear headstock, 21... rear spindle, 21c... rear spindle rotation drive unit, 30...tool rest, 30c...tool rotation drive unit, 31...tool rest drive unit, 32...Gang-shaped tool post, 34...Back processing tool post, 70...NC device, AX1...spindle center line, AX2...processing center line, AX3...deburring tool center line, AX4...rotary tool center line, C1...cross hole, C1o...center, C1p...periphery, C2...long hole, C21...first arc section, C22...second arc section, C23...straight section, CM1,CM2...deburring processing command, ID...inner diameter, P0...Initial position, P1...Cutting position, PR1: Control program, PR2: Machining program, ST1...first process, ST2...second process, ST3...third process, TO1...Tool, TO2...Cross tool, TO3...Deburring tool, TO3b...Spherical cutting part, TD: Maximum diameter, U1...control unit, W1...workpiece, W1h...hollow portion, W1i...inner surface, W1o...outer surface.

Claims

1. a spindle that rotates together with the workpiece around the spindle center line; a tool rest to which a deburring tool is attached that cuts a peripheral portion of a hole in the workpiece along a machining center line that is perpendicular to the spindle center line; a control unit that controls a relative positional relationship between the spindle and the tool rest along a linear axis that extends along the spindle center line, and controls rotation of the spindle about a rotation axis that is centered on the spindle center line, The control unit a value (CD) representing a diameter corresponding to the peripheral portion when the hole is viewed from the machining center line direction along the machining center line, and a value (OD) representing a diameter corresponding to a circumference that passes through the peripheral portion and is centered on the spindle center line in a cross section perpendicular to the spindle center line; determining a translatory axis coordinate corresponding to a cutting position that varies along the circumference on the translatory axis and a rotational angle corresponding to the cutting position on the rotational axis based on the values ​​(CD) and (OD); a machine tool that controls the relative positional relationship in the spindle center line direction along the spindle center line to the linear axis coordinates and controls the rotation of the spindle to the rotation angle so that the cutting position changes along the periphery.

2. The deburring tool is attached to the tool rest in a direction along the center line of the spindle, The machine tool according to claim 1 , wherein the tool rest rotates the deburring tool around a center line of the deburring tool that extends along the center line of the spindle.

3. The workpiece has a cylindrical shape, The deburring tool is attached to the tool rest in a direction along the center line of the spindle, the tool rest rotates the deburring tool around a deburring tool center line that is aligned with the spindle center line; 2. The machine tool according to claim 1, wherein a maximum diameter of a portion of the deburring tool that is inserted inside the cylindrical workpiece and that is centered on a center line of the deburring tool is smaller than an inner diameter of the workpiece.

4. When viewed from the processing center line direction, the peripheral portion includes a first arc portion having an arc shape, a second arc portion having an arc shape, and a straight line portion connecting the first arc portion to the second arc portion, The control unit The value (CD), the value (OD), and a value (LC) representing the center-to-center distance between the first arc portion and the second arc portion are obtained; determining the linear axis coordinate corresponding to the cutting position and the rotation angle corresponding to the cutting position for each of the first arc portion, the second arc portion, and the straight portion based on the value (CD), the value (OD), and the value (LC); The machine tool according to any one of claims 1 to 3, wherein the relative positional relationship in the spindle center line direction is controlled to the linear axis coordinates, and rotation of the spindle is controlled to the rotation angle, so that the cutting position changes along the first circular arc portion, the second circular arc portion, and the straight line portion.

5. a ball end mill is attached to the tool rest as the deburring tool; The machine tool according to any one of claims 1 to 3, wherein the tool rest rotates the ball end mill around a center line of the ball end mill.

6. A control position determination method for a machine tool comprising: a spindle that rotates together with a workpiece about a spindle center line; and a tool post having a deburring tool attached thereto that cuts a peripheral portion of a hole in the workpiece oriented along a machining center line that is perpendicular to the spindle center line, the method controlling a relative positional relationship between the spindle and the tool post along a linear axis along the spindle center line and a rotation of the spindle about a rotation axis about the spindle center line, the method comprising: a first step of acquiring a value (CD) representing a diameter corresponding to the peripheral portion when the hole is viewed from a machining center line direction along the machining center line, and a value (OD) representing a diameter corresponding to a circumference centered on the spindle center line and passing through the peripheral portion in a cross section perpendicular to the spindle center line; and a second step of determining a linear axis coordinate corresponding to the cutting position on the linear axis and a rotation angle corresponding to the cutting position on the rotation axis based on the value (CD) and the value (OD) so that the cutting position by the deburring tool changes along the periphery.

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