Numerical control device

Abstract

The present invention addresses the problem of avoiding uncut portions of a workpiece and interference between a workpiece and a tool attributed to an incorrect movement direction or movement amount of the rotational axis, without changing a program.　The numerical control device according to the present invention is a numerical control device for a machine tool that implements machining while changing the relative position and relative orientation between a tool and a workpiece on the basis of a program, the numerical control device comprising: a contour shape generation unit that generates contour shape information pertaining to the contour shape of the workpiece on the basis of relative movement information between the tool and the workpiece described in the program; a relative orientation determination unit that determines a relative orientation of the tool in relation to the workpiece at a change point included in the contour shape information; and a relative orientation change direction determination unit that determines, according to the type of the contour shape, a change direction for the relative orientation in order to obtain the determined relative orientation.

Description

Technical Field

[0001] The present invention relates to a numerical control device.

Background Art

[0002] For high-speed machining and / or high-precision machining, there are known machine tools (for example, 5-axis machining centers, composite machine tools, etc.) that machine a workpiece while changing the relative posture between a tool and the workpiece by the cooperative operation of linear axes and rotary axes. In machining with such a machine tool, there is known a technique of commanding the position and relative posture of a cutting point in each block of a program and controlling linear axes and rotary axes according to these commands and a preset tool offset. See, for example, Patent Document 1.<G

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, even if the position of the rotary axis at the start point / end point of each block is correct, interference between the tool and the workpiece or uncutting of the workpiece may occur unless the moving direction (and the amount of movement) of the rotary axis is set appropriately. FIG. 9 is a diagram showing an example of interference with a workpiece when using a multi-edge tool for turning. FIG. 9 shows a case of turning with a multi-edge tool for turning along machining paths N1 to N3. In FIG. 9, for example, the linear axes (Z, X) and the B axis of the multi-edge tool for turning are controlled so that the edge 1 of the multi-edge tool for turning is always in contact with the workpiece. However, in conventional technology, if the user does not programmatically specify that the multi-edge turning tool move clockwise in accordance with the arc motion of the machining path N2 from the endpoint P of the machining path N1 to the endpoint Q of the machining path N2, the B-axis of the multi-edge turning tool may rotate counterclockwise. In this case, as shown in Figure 9, the multi-edge turning tool and the workpiece may interfere with each other.

[0005] Figure 10 shows an example of a case where uncut material remains on the workpiece when swarf machining is performed on the side surface of a frustocone using a ball end mill. In Figure 10, for example, the linear axis (X,Y) and C axis of the ball end mill are controlled so that the tool side of the ball end mill is always in contact with the workpiece side. However, in conventional technology, when moving around an arc from position P, if the user does not programmatically specify, for example, that the C axis rotate 360 ​​degrees clockwise in accordance with the movement of the arc, the tool tip of the ball end mill may not make contact with the workpiece side when it reaches the opposite side of the arc, as shown in Figure 10, and the workpiece may not be cut.

[0006] Possible workarounds for the problems shown in Figures 9 and 10 include dividing the block into two or more parts and issuing commands for each, or directly commanding the amount of movement of the rotation axis as described above. However, these methods require considerable effort to edit and verify the program. Furthermore, adopting this workaround makes the program itself more complex, leading to the problem of wasting program memory. Furthermore, this workaround cannot be applied to commands that generate movement commands within the numerical control unit, such as fixed cycles, and therefore the risk of interference may not be avoided.

[0007] Therefore, it is desirable to avoid tool-workpiece interference and workpiece incomplete machining caused by incorrect direction or amount of rotation of the rotating axis, without changing the program. [Means for solving the problem]

[0008] One embodiment of the numerical control device of the present disclosure is a numerical control device for a machine tool that performs machining by changing the relative position and relative orientation of a tool and a workpiece based on a program, comprising: a contour shape generation unit that generates contour shape information relating to the contour shape of the workpiece based on relative movement information between the tool and the workpiece described in the program; a relative orientation determination unit that determines the relative orientation of the tool with respect to the workpiece at change points included in the contour shape information; and a relative orientation change direction determination unit that determines the direction of change of the relative orientation to achieve the determined relative orientation according to the type of contour shape. [Effects of the Invention]

[0009] According to one embodiment, interference between the tool and the workpiece, as well as incomplete cutting of the workpiece, caused by incorrect direction or amount of movement of the rotating shaft, can be avoided without changing the program. [Brief explanation of the drawing]

[0010] [Figure 1] This is a functional block diagram showing an example of the functional configuration of a numerical control device according to the first embodiment. [Figure 2] This figure shows an example of a machining program when using a multi-edge tool for turning. [Figure 3] This figure shows an example of a program path (machining path) shown in the machining program in Figure 2. [Figure 4] This is a flowchart illustrating the control process of a numerical control device. [Figure 5] This is a functional block diagram showing an example of the functional configuration of a numerical control device according to the second embodiment. [Figure 6] This figure shows an example of a machining program when using a ball end mill. [Figure 7] This figure shows an example of a program path (machining path) shown in the machining program in Figure 6. [Figure 8] This figure shows an example of the relationship between the direction vector and offset vector of a ball end mill. [Figure 9]This figure shows an example of interference with a workpiece when using a multi-edge tool for turning. [Figure 10] This figure shows an example of a case where uncut material remains on the workpiece when swarf machining is performed on the side of a frustocone using a ball end mill. [Modes for carrying out the invention]

[0011] The first and second embodiments will be described in detail with reference to the drawings. Herein, each embodiment shares a common configuration in which contour shape information relating to the contour shape of the workpiece is generated based on relative movement information between the tool and the workpiece described in the program, and the relative orientation of the tool to the workpiece is determined based on the generated contour shape information to perform machining. However, in the first embodiment, a multi-edge turning tool is used as the tool, and the direction of change of the B-axis of the multi-edge turning tool is determined according to the type of contour shape, as the relative position of the multi-edge turning tool with respect to the workpiece. In contrast, the second embodiment differs from the first embodiment in that a ball end mill is used as the tool, and the direction of movement of the C-axis of the ball end mill is determined according to the type of contour shape, as the relative position of the ball end mill with respect to the workpiece. In the following, we will first describe the first embodiment in detail, and then describe the second embodiment, focusing on the differences from the first embodiment.

[0012] <First Embodiment> Figure 1 is a functional block diagram showing an example of the functional configuration of a numerical control device according to the first embodiment. Here, as described above, an example is shown in which a multi-edge tool for turning is used as the tool. However, the present invention is not limited to a multi-edge tool for turning and can be applied to any tool. Furthermore, the case of a circular arc is given as an example of a contour shape. Note that this is not limited to circular arcs, and can be applied to any type of contour shape. The numerical control device 10 and the machine tool 20 may be directly connected to each other via a connection interface not shown in the drawings. Note that the numerical control device 10 and the machine tool 20 may be connected to each other via a network not shown in the drawings, such as a LAN (Local Area Network) or the Internet. In this case, the numerical control device 10 and the machine tool 20 include a communication unit not shown in the drawings for communicating with each other by such a connection. Note that the numerical control device 10 may be included in the machine tool 20 as will be described later.

[0013] <Machine tool 20> The machine tool 20 is, for example, a five-axis machining center or the like that changes the relative position and relative orientation of a tool and a workpiece, which are known to those skilled in the art, to perform machining, and operates based on commands from the numerical control device 10 described later.

[0014] <Numerical control device 10> The numerical control device 10 is a numerical control device known to those skilled in the art, generates commands based on control information, and transmits the generated commands to the machine tool 20. Thereby, the numerical control device 10 controls the operation of the machine tool 20. As shown in FIG. 1, the numerical control device 10 includes a control unit 100 and a storage unit 200. The control unit 100 includes an NC command decoding unit 110, a contour shape generation unit 120, a relative orientation determination unit 130, a relative orientation change direction determination unit 140, and an axis control unit 150.

[0015] <Storage unit 200> The storage unit 200 is a storage unit such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The storage unit 200 stores an operating system, application programs, etc. that are executed by the control unit 100 described later. Furthermore, the memory unit 200 may pre-store shape information relating to the geometric shapes of multi-edge turning tools that can be selected for the machine tool 20. In addition, the memory unit 200 may store the offsets of each edge of the multi-edge turning tool in the X-axis direction and the Z-axis direction when the B-axis around the Y-axis is "0 degrees" as shape information for each multi-edge turning tool. Furthermore, the memory unit 200 may store the results of the analysis of the machining program by the NC command decoding unit 110 (described later) as relative movement information, or it may store contour shape information generated by the contour shape generation unit 120 (described later).

[0016] <Control Unit 100> The control unit 100 includes a CPU, ROM, RAM, CMOS memory, etc., which are configured to communicate with each other via a bus, and is known to those skilled in the art. The CPU is a processor that controls the numerical control unit 10 as a whole. The CPU reads system programs and application programs stored in ROM via the bus and controls the entire numerical control unit 10 according to the system programs and application programs. As a result, as shown in Figure 1, the control unit 100 is configured to realize the functions of the NC command decoding unit 110, contour shape generation unit 120, relative posture determination unit 130, relative posture change direction determination unit 140, and axis control unit 150. Various data such as temporary calculation data and display data are stored in RAM. The CMOS memory is backed up by a battery (not shown) and is configured as a non-volatile memory that retains its memory state even when the power to the numerical control unit 10 is turned off.

[0017] The NC command decoding unit 110 acquires a machining program 30 generated by an external device, such as a CAD / CAM system, and analyzes the acquired machining program 30. The NC command decoding unit 110 outputs the analysis results as relative movement information to the contour shape generation unit 120, which will be described later. Alternatively, the NC command decoding unit 110 may store the analysis results as relative movement information in the storage unit 200.

[0018] Figure 2 shows an example of a machining program 30 when using a multi-edge tool for turning. Figure 3 shows an example of a program path (machining path) shown by the machining program 30 in Figure 2. In Figure 3, the case in which "Edge 1" of the multi-edge tool 40 for turning is selected for turning is illustrated. Also in Figure 3, the machining paths corresponding to sequence numbers N11 to N13 in the machining program 30 are shown as N11 to N13, respectively. As shown in Figure 2, the machining program 30 is written in G code, and the program name "O1001" is set in the first block. The second block, sequence number N10, specifies the position of the tool tip by address (Z,X) through ZX plane selection in tool posture control mode "G42.9" and specifies the offset vector of edge 1 indicated by tool offset number "D1" of the multi-edge turning tool 40 stored in the memory unit 200. As a result, the relative posture change direction determination unit 140, described later, automatically positions the B axis of the multi-edge turning tool 40 according to the path of the machining program 30 so that the specified offset vector (arrow) points in the direction shown in Figure 3 at each position of the arc.

[0019] The third block, sequence number N11, as shown in Figure 3, uses tool position control mode "G42.9" to cut edge 1 of the multi-edge turning tool 40 along the machining path N11 in the negative Z-axis direction by "10 mm (= 60 - 50)" at a feed rate of "F0.3 (mm / spindle revolution)". The fourth block, sequence number N12, uses tool posture control mode "G42.9" and performs clockwise arc interpolation from the end of machining path N11 (50.0, 10.0) to the end of machining path N12 (30.0, 10.0), using a point (40.0, 7.321) which is shifted by -10.0 in the Z-axis direction and -2.679 in the X-axis direction from the end of machining path N11 (50.0, 10.0) to the end of machining path N12 (30.0, 10.0). In this case, the relative posture change direction determination unit 140, described later, controls the B axis clockwise during the arc interpolation so that the offset vector of edge 1 of the multi-edge turning tool 40 always coincides with the normal of the arc, as shown in Figure 3. The fifth block, sequence number N13, uses tool position control mode "G42.9" to cut edge 1 of the multi-edge turning tool 40 along machining path N13 in the negative Z-axis direction by "10 mm (=30-20)" at a feed rate of "F0.3 (mm / spindle revolution)".

[0020] The contour shape generation unit 120 generates contour shape information relating to the contour shape of the workpiece based on the relative movement information between the multi-edge turning tool 40 and the workpiece, which is described in the machining program 30. Specifically, the contour shape generation unit 120 generates the machining paths N11 to N13 shown in Figure 3 as contour shape information, for example, based on relative movement information obtained from analysis by the NC command decoding unit 110. The contour shape generation unit 120 stores the generated contour shape information in the storage unit 200.

[0021] The relative orientation determination unit 130 determines the relative orientation of the multi-edge turning tool 40 with respect to the workpiece at the change point included in the contour shape information. Specifically, the relative posture determination unit 130 determines the relative posture between the multi-edge turning tool 40 and the workpiece such that, for example, as shown in Figure 3, at the endpoints of the machining paths N11 and N12, which are change points included in the contour shape information, the direction of the offset vector of the multi-edge turning tool 40 (a vector shown by a solid line from the tip of edge 1 of the multi-edge turning tool 40 toward the rotation center) coincides with the normal of the arc, and the multi-edge turning tool 40 does not interfere with the workpiece. The relative posture determination unit 130 also determines whether or not the multi-edge turning tool 40 and the workpiece interfere, for example, using the shape information of the multi-edge turning tool 40 stored in the storage unit 200.

[0022] The relative attitude change direction determination unit 140 determines the direction of change of the relative attitude in order to achieve the determined relative attitude, for example, according to the type of contour shape (e.g., an arc) between change points (end points of each block or cycle). Specifically, the relative posture change direction determination unit 140, for example, based on the relative movement information which is the analysis result of the NC command decoding unit 110, determines that the contour shape of the machining path N12 is a clockwise arc, and automatically determines that the direction of change of the B axis of the multi-edge turning tool 40 is clockwise (i.e., it moves in the negative direction of the B axis). Furthermore, the relative posture change direction determination unit 140 determines the amount of change in the B axis of the multi-edge turning tool 40 as α degrees, based on the fact that the central angle α of the arc of the machining path N12 shown in Figure 3 is approximately 210 degrees.

[0023] The relative posture change direction determination unit 140 may also determine the amount of change along with the direction of change of the relative posture of the multi-edge turning tool 40. In this case, the relative posture change direction determination unit 140 may determine the amount of change within a range where the multi-edge turning tool 40 and the workpiece do not interfere with each other. For example, if the relative posture change direction determination unit 140 determines that the change in the B axis of the multi-edge turning tool 40 is α + 360 degrees × n (where n is an integer greater than or equal to 1), the multi-edge turning tool 40 will interfere with the workpiece in the middle of the machining path N12. Therefore, in the case of Figure 3, the relative posture change direction determination unit 140 automatically determines that the change in the B axis of the multi-edge turning tool 40 is α degrees, within a range where the multi-edge turning tool 40 and the workpiece do not interfere with each other.

[0024] Furthermore, the relative posture change direction determination unit 140 may calculate the speed V' of the B axis as V' = α × V / L when the arc length of the machining path N12 shown in Figure 3 is L and the tip speed of edge 1 of the multi-edge tool 40 for turning is V (for example, in the machining program 30 in Figure 2, the feed rate is "F0.3 (mm / spindle revolution)"). In this case, if the value of V' exceeds a predetermined tolerance, the relative posture change direction determination unit 140 may automatically reduce the tip speed V of edge 1 to below the feed rate "F0.3 (mm / spindle revolution)".

[0025] By doing so, the numerical control device 10 can automatically determine the direction and amount of movement of the B-axis of the multi-edge turning tool 40 in the machining program 30, without the user having to directly specify the direction and amount of movement of the B-axis of the multi-edge turning tool 40. This prevents interference between the multi-edge turning tool 40 and the workpiece caused by incorrect direction or amount of movement of the rotation axis. Furthermore, since users no longer need to manually divide blocks or directly command the movement amount of the B-axis, the effort required for program editing and verification is reduced.

[0026] The axis control unit 150 moves the multi-edge turning tool 40 or the workpiece relative to it, for example, based on the direction of change of the B axis of the multi-edge turning tool 40 and / or the amount of change of the B axis determined by the relative posture change direction determination unit 140.

[0027] <Control processing of the numerical control device 10> Next, the control process flow of the numerical control device 10 will be explained with reference to Figure 4. Figure 4 is a flowchart illustrating the control process of the numerical control device 10. The flowchart shown here is executed repeatedly each time the machining program 30 is run.

[0028] In step S11, the NC command decoding unit 110 acquires the machining program 30.

[0029] In step S12, the NC command decoding unit 110 analyzes the machining program 30 acquired in step S11. The NC command decoding unit 110 then outputs the analysis results as relative movement information to the contour shape generation unit 120.

[0030] In step S13, the contour shape generation unit 120 generates contour shape information relating to the contour shape of the workpiece based on the relative movement information received from the NC command decoding unit 110.

[0031] In step S14, the relative posture determination unit 130 determines the relative posture of the multi-edge turning tool 40 with respect to the workpiece at the change point (end point of the machining path) based on the contour shape information generated in step S13.

[0032] In step S15, the relative posture change direction determination unit 140 determines the direction of change of the relative posture of the multi-edge turning tool 40 to achieve the determined relative posture, according to the type of contour shape. The relative posture change direction determination unit 140 also calculates the tip speed V of edge 1 of the multi-edge turning tool 40 so that the speed V' of the B axis of the multi-edge turning tool 40 does not exceed a predetermined allowable value.

[0033] In step S16, the axis control unit 150 moves the multi-edge turning tool 40 and the workpiece relative to each other based on the direction of change of the relative orientation of the tool determined in step S16.

[0034] As described above, the numerical control device 10 according to the first embodiment generates contour shape information relating to the contour shape of the workpiece by setting the machining program 30 to the tool posture control mode "G42.9", determines the relative posture of the tool with respect to the workpiece at the change points included in the contour shape information, and determines the direction of change of the relative posture of the tool to achieve the relative posture determined according to the type of contour shape. In this way, the numerical control device 10 can avoid interference between the tool and the workpiece and unmachined workpiece caused by incorrect direction or amount of movement of the rotation axis, without changing the machining program 30. Furthermore, since users no longer need to manually split blocks or directly command the movement amount of the rotation axis, the effort required for program editing and verification is reduced. Furthermore, since the numerical control device 10 does not require program editing, the amount of program memory used does not increase. The first embodiment has been described above.

[0035] <Second Embodiment> Next, a second embodiment will be described. In the first embodiment, in the tool posture control mode "G42.9", the direction of change of the B axis of the multi-edge turning tool was determined according to the type of contour shape as the relative posture of the multi-edge turning tool with respect to the workpiece. In contrast, the second embodiment differs from the first embodiment in that, in the tool posture control mode "G43.5 P3", the direction of movement of the C axis of the ball end mill is determined according to the type of contour shape as the relative posture of the ball end mill with respect to the workpiece. As a result, the numerical control device 10A of the second embodiment can avoid interference between the tool and the workpiece, as well as incomplete cutting of the workpiece, caused by incorrect direction or amount of movement of the rotating shaft, without changing the program. A second embodiment will be described below.

[0036] Figure 5 is a functional block diagram showing an example of the functional configuration of the numerical control device 10A according to the second embodiment. Elements having the same functions as those of the numerical control device 10 in Figure 1 are denoted by the same reference numerals, and detailed explanations are omitted. The numerical control device 10A and the machine tool 20 may be directly connected to each other via a connection interface (not shown). Alternatively, the numerical control device 10A and the machine tool 20 may be interconnected via a network (not shown), such as a LAN or the Internet. In this case, the numerical control device 10A and the machine tool 20 are equipped with a communication unit (not shown) for communicating with each other via such connection. The machine tool 20 has the same functions as the machine tool 20 in the first embodiment.

[0037] <Numerical control device 10A> As shown in Figure 5, the numerical control device 10A has a control unit 100a and a storage unit 200a. Furthermore, the control unit 100a has an NC command decoding unit 110, a contour shape generation unit 120, a relative posture determination unit 130, a relative posture change direction determination unit 140a, and an axis control unit 150.

[0038] <Storage section 200a> The storage unit 200a is a storage unit such as an SSD or HDD. The storage unit 200a stores the operating system and application programs that will be executed by the control unit 100a, which will be described later. Furthermore, the memory unit 200a may pre-store shape information relating to the geometric shapes of ball end mills that can be selected by the machine tool 20. For example, the memory unit 200a may store the tool length compensation amount and the tool holder diameter for each ball end mill as shape information.

[0039] <Control Unit 100a> The control unit 100a includes a CPU, ROM, RAM, CMOS memory, etc., which are configured to communicate with each other via a bus, and is known to those skilled in the art. The CPU is a processor that controls the numerical control device 10A as a whole. The CPU reads the system program and application program stored in ROM via the bus and controls the entire numerical control device 10A according to the system program and application program. As a result, as shown in Figure 5, the control unit 100a is configured to realize the functions of the NC command decoding unit 110, the contour shape generation unit 120, the relative posture determination unit 130, the relative posture change direction determination unit 140a, and the axis control unit 150.

[0040] The NC command decoding unit 110, contour shape generation unit 120, relative posture determination unit 130, and axis control unit 150 have the same functions as the NC command decoding unit 110, contour shape generation unit 120, relative posture determination unit 130, and axis control unit 150 in the first embodiment.

[0041] Figure 6 shows an example of a machining program 30 when using a ball end mill. Figure 7 shows an example of a program path (machining path) shown by the machining program 30 in Figure 6. In Figure 7, an example is shown in which the ball end mill 45 performs swarf machining on the side surface of a frustocone based on the machining program 30 shown in Figure 6. In Figure 7, the program paths (machining paths) corresponding to sequence numbers N10 to N14 in the machining program 30 are shown as N10 to N14, respectively. As shown in Figure 6, the machining program 30 is written in G code, and the program name "O2001" is set in the first block. The second block, sequence number N01, is the side machining mode "G43.5 P3" for tool posture control. For example, the tool length compensation amount indicated by the tool offset number "H1" of the ball end mill 45 stored in the memory unit 200 is used to specify the position of the tool tip of the ball end mill 45 with (X,Y,Z), and the offset vector of the ball end mill 45 (the vector shown by the dashed line from the tool tip to the root of the ball end mill 45) is specified with (II,JJ,KK). By commanding the side machining mode "G43.5 P3" for tool posture control, as will be described later, the X,Y coordinates of the centers of the circle drawn by the tool tip of the ball end mill 45 and the circle drawn by the root of the ball end mill 45 coincide in the block of sequence number N12. For this reason, the arc command in the tool tip point control mode "G43.5 P3" has the information of "side of a frustocone". Furthermore, the offset vector (II, JJ, KK) of the ball end mill 45 is specified by sequence number N10, which will be described later.

[0042] The third block, sequence number N10, uses the side milling mode "G43.5 P3" for tool position control, rapidly traversing the tip of the ball end mill 45 to the position (10,0,0), and setting the direction of the offset vector (the vector shown by the dashed line from the tip to the root of the ball end mill 45) to (0,1,5) at the end of the machining path N10. The fourth block, sequence number N11, uses the side milling mode "G43.5 P3" for tool position control, maintaining the offset vector direction at (0,1,5) while linearly interpolating (cutting feed) to the position (12,0,0) at a feed rate of "F300 (mm / min)". The fifth block, sequence number N12, is the side machining mode "G43.5 P3" for tool posture control. It uses the point (12.0, 5.0), which is shifted by 0.0 in the X-axis direction and 5.0 in the Y-axis direction from the endpoint (12.0, 0.0) of the machining path N11, as the center position of the arc, and performs counterclockwise arc interpolation in the XY plane. In this case, the relative posture change direction determination unit 140a, described later, controls the tip position and posture (C-axis around the Z-axis) of the ball end mill 45 so that, during the arc interpolation, the direction vector V of the tool tip of the ball end mill 45 and the offset vector (dashed line) of the ball end mill 45 are always maintained at the same angle. The sixth sequence number, N13, is a side milling mode for tool position control, "G43.5 P3," which linearly interpolates (cutting feed) to the position (14,0,0) at a feed rate of "F300 (mm / min)" while maintaining the offset vector direction (0,1,5). The seventh sequence number, N14, is a side milling mode "G43.5 P3" for tool position control, which rapidly traverses to the position (20,0,0) while maintaining the offset vector direction (0,1,5).

[0043] The relative posture change direction determination unit 140a determines the direction of change of the relative posture in order to achieve the determined relative posture, for example, according to the type of contour shape (for example, the side surface of a frustum (swarf machining), etc.) between change points (the end point of each block or cycle). Specifically, as shown in Figure 8, the relative posture change direction determination unit 140a determines the direction of change of the C axis of the ball end mill 45 around the Z axis, such that, during the counterclockwise circular arc interpolation of the machining path N12 in the XY plane, the direction vector V of the tool tip of the ball end mill 45 and the offset vector (dashed line) of the ball end mill 45 are always maintained at the same angle. This is determined by the relative movement information obtained from the analysis of the NC command decoding unit 110, and the type of contour shape of the machining path N12 is the side surface of a counterclockwise frustum of a cone (swarf machining). In other words, since sequence number N12 is a block of counterclockwise arc interpolation in the side machining mode of tool posture control "G43.5 P3", the relative posture change direction determination unit 140a automatically determines that the movement direction (change direction) of the C axis of the ball end mill 45 is the positive direction, as shown in Figure 8.

[0044] Furthermore, since sequence number N12 is a block that completes exactly one revolution around the arc, the relative posture change direction determination unit 140a determines the amount of C-axis movement of the ball end mill 45 to be 360 ​​degrees. In other words, if the amount of C-axis movement is 0 degrees, 720 degrees, etc., the ball end mill 45 and the workpiece will interfere with each other. Furthermore, the relative posture change direction determination unit 140a may calculate the C-axis speed V' as V' = 360 degrees × V / L when the arc length of the machining path N12 shown in Figure 8 is L and the tip speed (direction vector) of the ball end mill 45 is V (for example, the feed rate is "F300 (mm / min)" in the machining program 30 in Figure 6). In this case, if the value of V' exceeds a predetermined tolerance, the relative posture change direction determination unit 140a may automatically reduce the tip speed (direction vector) V of the ball end mill 45 to a level lower than the feed rate "F300 (mm / min)".

[0045] By doing so, the numerical control device 10A can automatically determine the direction and amount of movement of the C-axis of the ball end mill 45 in the machining program 30, without the user having to directly specify the direction and amount of movement of the C-axis of the ball end mill 45. This avoids interference between the ball end mill 45 and the workpiece caused by incorrect direction or amount of movement of the rotation axis. Furthermore, since users no longer need to manually divide blocks or directly command the movement amount of the C-axis, the effort required for program editing and verification is reduced.

[0046] The control process of the numerical control device 10A is the same as in Figure 4, so a detailed explanation is omitted.

[0047] As described above, the numerical control device 10A according to the second embodiment generates contour shape information relating to the contour shape of the workpiece by setting the tool posture control to the side machining mode "G43.5 P3" in the machining program 30, determines the relative posture of the tool with respect to the workpiece at the change points included in the contour shape information, and determines the direction of change of the relative posture of the tool to achieve the relative posture determined according to the type of contour shape. In this way, the numerical control device 10A can avoid interference between the tool and the workpiece and unmachined workpiece caused by incorrect movement direction or amount of movement of the rotation axis without changing the machining program 30. Furthermore, since users no longer need to manually split blocks or directly command the movement amount of the rotation axis, the effort required for program editing and verification is reduced. Furthermore, since the numerical control device 10A does not require program editing, the amount of program memory used does not increase. The second embodiment has now been described.

[0048] Although the first and second embodiments have been described above, the numerical control devices 10 and 10A are not limited to the embodiments described above, and may include modifications, improvements, etc., to the extent that the objective can be achieved.

[0049] <Example 1> In the first and second embodiments, the numerical control devices 10 and 10A are separate devices from the machine tool 20, but the embodiment is not limited thereto. For example, the numerical control devices 10 and 10A may be included in the machine tool 20.

[0050] <Modification 2> Furthermore, while the first and second embodiments used a multi-edge turning tool 40 or a ball end mill 45 as the tool, the method is not limited to these. For example, it can be applied to any tool.

[0051] In the first and second embodiments, each function included in the numerical control devices 10 and 10A can be implemented by hardware, software, or a combination thereof. Here, implementation by software means that the function is implemented by a computer reading and executing a program.

[0052] Programs can be stored and supplied to a computer using various types of non-transitory computer-readable medium. Non-transitory computer-readable mediums include various types of tangible storage mediums. Examples of non-transitory computer-readable mediums include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, RAMs). Programs may also be supplied to a computer using various types of transient computer-readable mediums. Examples of transient computer-readable mediums include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable mediums can be supplied to a computer via wired communication channels such as electric wires and optical fibers, or via wireless communication channels.

[0053] Furthermore, the step of writing the program to be recorded on the recording medium includes not only processes that are performed chronologically in that order, but also processes that are not necessarily performed chronologically, but are executed in parallel or individually.

[0054] In other words, the numerical control device of this disclosure can take various forms having the following configurations.

[0055] (1) The numerical control devices 10 and 10A of the present disclosure are numerical control devices for a machine tool 20 that performs machining by changing the relative position and relative posture of a tool and a workpiece based on a machining program 30, and include a contour shape generation unit 120 that generates contour shape information relating to the contour shape of a workpiece based on relative movement information between the tool and the workpiece described in the machining program 30, a relative posture determination unit 130 that determines the relative posture of the tool with respect to the workpiece at change points included in the contour shape information, and relative posture change direction determination units 140 and 140a that determine the direction of change of the relative posture to achieve the determined relative posture according to the type of contour shape. With these numerical control devices 10 and 10A, it is possible to avoid interference between the tool and the workpiece, as well as incomplete cutting of the workpiece, caused by incorrect direction or amount of movement of the rotating shaft, without changing the program.

[0056] (2) In the numerical control devices 10 and 10A described in (1), the relative posture determination unit 130 may determine the relative posture by using a value commanded by the machining program 30 or by calculating based on the contour shape. By doing so, the numerical control devices 10 and 10A can easily determine the relative attitude.

[0057] (3) In the numerical control devices 10 and 10A described in (1) or (2), the relative posture change direction determination units 140 and 140a may determine the direction of relative posture change and / or the amount of relative posture change within a range in which the tool and the workpiece do not interfere with each other when the tool and the workpiece move relative to each other along the contour shape. By doing so, the numerical control devices 10 and 10A can maintain the machining quality of the workpiece.

[0058] (4) In the numerical control devices 10, 10A described in any of (1) to (3), the relative posture change direction determination units 140, 140a may control the tool and / or workpiece so as not to move at a speed greater than a predetermined speed when moving the tool and workpiece relative to each other according to the determined relative posture change direction. By doing so, the numerical control devices 10 and 10A can maintain machining quality for the workpiece and suppress tool deterioration. [Explanation of Symbols]

[0059] 10, 10A Numerical Control Device 100, 100a Control Unit 110 NC Command Decoding Unit 120 Contour shape generation unit 130 Relative attitude determination unit 140, 140a Relative attitude change direction determination unit 150 Axis control unit 200, 200a storage section 20 Machine tools 30 Machining Programs 40 Multi-edge tools for turning 45 Ball End Mill

Claims

1. A numerical control device for a machine tool that performs machining by changing the relative position and relative orientation of the tool and workpiece based on a program, A contour shape generation unit generates contour shape information relating to the contour shape of the workpiece based on relative movement information between the tool and the workpiece described in the program, A relative posture determination unit that determines the relative posture of the tool with respect to the workpiece at change points indicating the end of each block or cycle of the program included in the contour shape information, A relative posture change direction determination unit determines the direction of change of the relative posture so that the determined relative posture is maintained on the machining path in which the tool and / or workpiece moves between the two change points, depending on the type of contour shape between the change points. A numerical control device equipped with the following features.

2. The numerical control device according to claim 1, wherein the relative attitude determination unit determines the relative attitude by using a value commanded by the program or by calculating based on the contour shape.

3. The numerical control device according to claim 1 or 2, wherein the relative posture change direction determination unit determines the direction of the relative posture change and / or the amount of the relative posture change within a range in which the tool and the workpiece do not interfere with each other when the tool and the workpiece move relative to each other along the contour shape.

4. The numerical control device according to any one of claims 1 to 3, wherein the relative posture change direction determination unit controls the tool and / or the workpiece so that they do not move at a predetermined speed or higher when the tool and the workpiece are moved relative to each other according to the determined relative posture change direction.

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