MACHINE TOOL, POSITION INFORMATION CORRECTING METHOD, AND POSITION INFORMATION CORRECTING PROGRAM

Abstract

Provided is a machine tool comprising: a spindle that rotatably grips a workpiece; a blade mount on which a tool for processing the workpiece can be mounted; a moving body that is movable independently from the spindle and the blade mount; a contact type sensor that moves according to movement of the moving body; and a control device that calculates central position information indicating the central position of the spindle on the basis of spindle position information obtained via the sensor having been moved to the vicinity of the workpiece by moving the moving body. The control device obtains blade edge position information indicating the position of a blade edge of the tool via the sensor by moving the moving body, and corrects the blade edge position information on the basis of the central position information.

Description

[Technical field]

[0001] The present disclosure relates to a machine tool, a position information correction method, and a position information correction program. [Background technology]

[0002] In machine tools such as turning centers and machining centers, various techniques are known for detecting the position of a tool that processes a workpiece. For example, a technique is known in which a tool is manually brought into contact with a workpiece, the positional relationship between the cutting edge of the tool and the workpiece is measured, and the position of the tool is input as an offset to an NC device. In addition, a technique called "external preset" is known in which a tool holder in which the position of a tool is adjusted in advance by a measuring jig also called a presetter is attached to the machine tool. However, these techniques have various problems, such as a long downtime of the machine tool and increased labor by the operator.

[0003] To solve these problems, a technique is known for automatically measuring the positional relationship between a workpiece and a tool in a machine tool. For example, Japanese Patent Application Laid-Open No. 2008-200798 discloses a machine tool that determines the position of the cutting edge of a tool with the center coordinates of a workpiece measured by a probe as a reference position based on the positional relationship between the tip of a stylus of a probe that measures the center coordinates of a workpiece and the cutting edge of the tool. In addition, Japanese Patent Application Laid-Open No. 2000-198047 discloses a machine tool that calculates the position of the cutting edge of a tool relative to a spindle center line based on the positional relationship between the tip of a stylus of a probe that measures the center coordinates of a workpiece and the cutting edge of the tool. Summary of the Invention

[0004] However, in the techniques described in JP 2008-200798 A and JP 2000-198047 A, the center position of the workpiece is measured, but the position of the cutting edge of the tool is not measured. In the techniques described in JP 2008-200798 A and JP 2000-198047 A, since the position of the cutting edge of the tool is not measured, when the position of the cutting edge of the tool is displaced due to heat generation or the like caused by machining of the workpiece, the positional relationship between the workpiece and the tool may include an error caused by the displacement of the position of the cutting edge of the tool.

[0005] An object of the present disclosure is to provide a machine tool capable of measuring the positional relationship between a workpiece and a tool with high accuracy.

[0006] The machine tool disclosed herein has a spindle that rotatably grips a workpiece, a tool post on which a tool for machining the workpiece can be mounted, a movable body that can move independently of the spindle and the tool post, a contact-type sensor that moves in accordance with the movement of the movable body, and a control device that calculates central position information indicating the central position of the spindle based on spindle position information acquired via the sensor that has been moved to the vicinity of the workpiece by moving the movable body, and the control device acquires cutting edge position information indicating the position of the cutting edge of the tool via the sensor by moving the movable body, and corrects the cutting edge position information based on the central position information.

[0007] Furthermore, in the machine tool according to the present disclosure, it is preferable that the control device acquires cutting edge position information by moving the movable body so that the central position of the sensor coincides with the central axis of the spindle, and by moving the tool post to bring the cutting edge of the tool into contact with the sensor.

[0008] Furthermore, in the machine tool according to the present disclosure, it is preferable that the sensor has a detection unit having a cylindrical support member and a plurality of contacts arranged on the circumferential surface of the support member, and moving the movable body so that the central position of the sensor coincides with the central axis of the spindle includes moving the movable body so that the central axis of the support member coincides with the central axis of the spindle.

[0009] Furthermore, in the machine tool according to the present disclosure, the multiple contact points include four contact points arranged at 90 degrees intervals on the circumferential surface of the support member, and it is preferable that the distance between a pair of contact points arranged at 180 degrees intervals among the four contact points is the same as the diameter of the workpiece.

[0010] Furthermore, in the machine tool according to the present disclosure, the movable body is preferably a back spindle that can be arranged opposite to the spindle.

[0011] In addition, the position correction method disclosed herein is a position correction method executed by a control device in a machine tool having a spindle that rotatably grips a workpiece, a tool post on which a tool for machining the workpiece can be mounted, a movable body that can move independently of the spindle and the tool post, a contact-type sensor that moves in accordance with the movement of the movable body, and a control device that calculates central position information indicating a central position of the spindle based on spindle position information acquired via the sensor moved to the vicinity of the workpiece by moving the movable body, and includes the control device acquiring cutting edge position information indicating the position of the cutting edge of the tool via the sensor by moving the movable body, and correcting the cutting edge position information based on the central position information.

[0012] In addition, the position correction program disclosed herein is for a machine tool having a spindle that rotatably grips a workpiece, a tool post on which a tool for machining the workpiece can be mounted, a movable body that can move independently of the spindle and the tool post, a contact-type sensor that moves in accordance with the movement of the movable body, and a control device that calculates central position information that indicates the central position of the spindle based on spindle position information acquired via the sensor that has been moved to the vicinity of the workpiece by moving the movable body, and causes the control device to execute a process of acquiring cutting edge position information that indicates the position of the cutting edge of the tool via the sensor by moving the movable body, and correcting the cutting edge position information based on the central position information.

[0013] The machine tool according to the present disclosure can accurately measure the positional relationship between the workpiece and the tool. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 is a perspective view of a machine tool according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the back spindle and the front tool rest arranged adjacent to the back spindle shown in FIG. [Diagram 3] 4 is a flowchart of a position information correction process executed by the machine tool shown in FIG. [Figure 4] 4A and 4B are diagrams for explaining the process of S102 shown in FIG. 3, in which (a) is a perspective view of the back spindle and the guide bush device, and (b) is a front view of the guide bush device. [Diagram 5] 4A and 4B are diagrams for explaining the processing of S103 shown in FIG. 3, in which (a) is a perspective view (part 1) of the back spindle and the guide bush device, and (b) is a perspective view (part 2) of the back spindle and the guide bush device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a machine tool, a control method for the machine tool, and a control program for the machine tool will be described with reference to the drawings. However, it should be understood that the present invention is not limited to the drawings or the embodiments described below.

[0016] FIG. 1 is a perspective view of a machine tool according to an embodiment.

[0017] The machine tool 1 has a bed 10, a front spindle 11, a back spindle 12, a guide bush device 13, a tool rest 14, and an NC device 20. The front spindle 11, the back spindle 12, the guide bush device 13, and the tool rest 14 are mounted on the bed 10. The front spindle 11 is a hollow member capable of gripping a cylindrical workpiece W1, and is movable in the Z1 direction by being installed on a moving mechanism that moves along a rail 15. The back spindle 12 is a hollow member capable of gripping a cylindrical workpiece W2, and is movable in the Z2 direction and the X2 direction by being installed on a moving mechanism that moves along rails 16 and 17. The guide bush device 13 is fixed to the bed 10 and supports the workpiece W1 gripped by the front spindle 11 so as to guide it slidably in the Z1 direction. The tool rest 14 is a member that holds a plurality of tools for machining the workpieces W1 and W2 held by the front spindle 11 and the back spindle 12, and is movable in the X1 and Y1 directions by being placed on a moving mechanism that moves along rails 18 and 19. The rotation and movement of the front spindle 11, the back spindle 12, and the tool rest 14 are controlled by an NC device 20 mounted on the machine tool 1. The front spindle 11, the back spindle 12, and the tool rest 14 can be moved independently of each other, that is, separately. The NC device 20 has an arithmetic circuit, a memory circuit that stores a position correction program that executes position information correction processing, and is a control device that instructs various operations of the machine tool. The position correction program may be installed in the management storage unit 42 from a computer-readable portable recording medium such as a CD-ROM or DVD-ROM using a known setup program.

[0018] FIG. 2 is a perspective view of the back spindle 12 and the front tool rest 21 disposed adjacent to the back spindle 12. As shown in FIG.

[0019] The front tool rest 21, also referred to as the counter tool rest, is a member that holds a rotating tool 22 such as a drill, a non-rotating tool 23, and a tool setter 24, and moves integrally with the movement of the back spindle 12. The tool setter 24 is a contact-type position sensor having a cylindrical support member 25 and a detection unit 26 arranged on the circumferential surface of the tip of the support member 25. The detection unit 26 has four contacts arranged on the circumferential surface of the support member 25 at 90 degree intervals, and the four contacts come into contact with a target member such as a workpiece W1 to detect the position of the target member from a total of four directions, two in each of the X2 and Y2 directions.

[0020] The tool setter 24 may have a pair of contacts that are 180 degrees apart among the four contacts of the detection unit 26, and the distance between the pair of contacts may be smaller or larger than the diameter of the workpiece W1 to be machined, as long as the four contacts can contact the workpiece W1. Furthermore, it is preferable to select the distance between the pair of contacts to be the same as the diameter of the workpiece W1, since this brings the workpiece W1 closer to the machining point where it is machined. Here, when the distance between the pair of contacts is 0.8 to 1.2 times the diameter of the workpiece W1, the distance between the pair of contacts is considered to be the same as the diameter of the workpiece W1.

[0021] Fig. 3 is a flowchart of the position information correction process executed by the machine tool 1. The position information correction process shown in Fig. 3 is executed by controlling each element of the machine tool 1 in response to a command from the NC device 20 and in cooperation with the element. The position information correction process shown in Fig. 3 may be executed before the workpiece W1 is machined by the tool, or may be executed as appropriate while the workpiece W1 is being machined by the tool. For example, the position information correction process shown in Fig. 3 may be executed immediately after the machine tool 1 is started, may be executed before machining of the workpiece W1 is started, or may be executed every time a predetermined number of machined workpieces are formed from the workpiece W1.

[0022] First, the NC device 20 instructs the front spindle 11 to grip the workpiece W1 (S101). In response to the instruction from the NC device 20, the front spindle 11 grips the workpiece W1 with a chuck (not shown).

[0023] Next, the NC device 20 issues an instruction to acquire spindle position information indicating the position of the front spindle (S102).

[0024] 4A and 4B are diagrams for explaining the process of S102, in which FIG. 4A is a perspective view of the back spindle 12 and the guide bush device 13, and FIG.

[0025] The NC device 20 moves the back spindle 12 to move the tool setter 24 to the vicinity of the workpiece W1 supported by the guide bush device 13. The NC device 20 acquires spindle position information via the tool setter 24 that has been moved to the vicinity of the workpiece W1.

[0026] First, the NC device 20 brings the detection unit 26 of the tool setter 24 into contact with the workpiece W1 as shown by the arrow A in FIG. 4(b) to acquire from the tool setter 24 the first position information P1 indicating the position of the upper end of the workpiece W1. Next, the NC device 20 brings the detection unit 26 of the tool setter 24 into contact with the workpiece W1 as shown by the arrow B in FIG. 4(b) to acquire from the tool setter 24 the second position information P2 indicating the position of the left end of the workpiece W1. Next, the NC device 20 brings the detection unit 26 of the tool setter 24 into contact with the workpiece W1 as shown by the arrow C in FIG. 4(b) to acquire from the tool setter 24 the third position information P3 indicating the position of the lower end of the workpiece W1. Next, the NC device 20 brings the detection unit 26 of the tool setter 24 into contact with the workpiece W1 as shown by the arrow C in FIG. 4(b) to acquire from the tool setter 24 the fourth position information P4 indicating the position of the right end of the workpiece W1. Then, the NC device 20 stores the first position information P1 to the fourth position information P4 acquired via the tool setter 24 as spindle position information.

[0027] Next, the NC device 20 calculates center position information indicating the center position of the front spindle 11 based on the spindle position information acquired by the processing of S102 via the tool setter 24 which has been moved to the vicinity of the workpiece W1 by moving the rear spindle 12 (S103).

[0028] The NC device 20 calculates the X1-direction coordinate Px of the center position of the front spindle 11 as the median value (P1+P3) / 2 of the first position information P1 indicating one coordinate of the workpiece W1 in the X1 direction and the third position information P3 indicating the other coordinate of the workpiece W1 in the X1 direction. Also, the NC device 20 calculates the Y1-direction coordinate Py of the center position of the front spindle 11 as the median value (P2+P4) / 2 of the second position information P2 indicating one coordinate of the workpiece W1 in the Y1 direction and the fourth position information P4 indicating the other coordinate of the workpiece W1 in the Y1 direction.

[0029] Next, the NC device 20 issues an instruction to obtain cutting edge position information indicating the position of the cutting edge of the tool (S104).

[0030] FIG. 5 is a diagram for explaining the processing of S104, in which FIG. 5(a) is an oblique view (part 1) of the back spindle 12 and the guide bush device 13, and FIG. 5(b) is an oblique view (part 2) of the back spindle 12 and the guide bush device 13.

[0031] The NC device 20 moves the back spindle 12 so that the center position of the tool setter 24 coincides with the center axis of the front spindle 11, and also moves the tool rest 14 to bring the cutting edge of the tool 140 held on the tool rest 14 into contact with the tool setter 24, thereby acquiring cutting edge position information.

[0032] First, as shown in Fig. 5(a), the NC device 20 moves the back spindle 12 so that the central axis of the support member 25 of the tool setter 24 coincides with the central axis of the front spindle 11 and the detection unit 26 of the tool setter 24 approaches the workpiece W1. The NC device 20 moves the back spindle 12 so that the positions of the center of the support member 25 of the tool setter 24 in the X1 direction and the Y direction coincide with the coordinates (Px, Py) indicated by the center position information calculated in the process of S103. Next, as shown in Fig. 5(a), the NC device 20 brings the cutting edge of the tool 140 into contact with the tool setter 24 from one side in the X1 direction of the tool rest 14, and acquires first cutting edge position information K1 indicating the position of the lower end of the cutting edge from the tool setter 24. 5(b), the NC device 20 brings the cutting edge of the tool 140 into contact with the tool setter 24 from one side in the Y1 direction of the tool rest 14, and acquires second cutting edge position information K2 indicating the position of the right end of the cutting edge from the tool setter 24. From the first cutting edge position information K1 and the second cutting edge position information K2, the coordinates (Kx, Ky) of the cutting edge of the tool 140 in the X1 direction and the Y1 direction are calculated.

[0033] Then, the NC device 20 corrects the cutting edge position information acquired in the process of S104 based on the central position information calculated in the process of S103 (S105). The NC device 20 corrects the X1-direction and Y1-direction coordinates (Kx, Ky) of the cutting edge of the tool 140 based on the X1-direction and Y1-direction coordinates (Px, Py) of the central position of the front spindle 11 included in the central position information, and generates corrected coordinates (Cx, Cy). In the corrected coordinates (Cx, Cy), Cx is represented by (Px-Kx), and Cy is represented by (Py-Ky). The corrected coordinates (Cx, Cy) generated in the process of S105 are the distance from the cutting edge position of the tool 140 to the workpiece W1, and Cx is also referred to as the "diameter" and Cy is also referred to as the "center".

[0034] After the position information correction process is completed, the machine tool 1 performs machining on the workpiece W1 with the tool 140 at the tool tip position corrected based on the position information correction process.

[0035] Since the machine tool 1 measures the positions of both the workpiece W1 and the tool 140 by the single tool setter 24, it is possible to correct the positional relationship between the workpiece W1 and the tool 140 with high accuracy.

[0036] In addition, by aligning the center position of the tool setter 24 with the center axis of the workpiece W1, the machine tool 1 can align the center position of the tool setter 24 with the center axis of the front spindle 11, and move the tool setter 24 closer to the vicinity of the workpiece W1 (the position when machining).

[0037] Furthermore, with the tool setter 24 positioned near the workpiece W1, the machine tool 1 acquires cutting edge position information indicating the cutting edge position of the tool 140 at a position close to the position where the workpiece W1 is machined, so that the cutting edge position information can be acquired with higher accuracy than when the cutting edge position information is acquired when the tool 140 is separated from the workpiece W1.

[0038] Furthermore, if a correction amount for cutting edge position information based on the center position information is stored in advance after the machine tool 1 calculates center position information indicating the center position of the front spindle 11, the machine tool 1 can correct the positional relationship between the workpiece W1 and the tool 140 by the correction amount. In this case, it is not necessary to make the central axis of the workpiece W1 and the central position of the tool setter 24 coincide with each other.

[0039] Furthermore, by executing the position information correction process while the workpiece W1 is being machined by the tool 140, the machine tool 1 can correct the positional relationship between the cutting edge of the tool 140 and the workpiece W1 with high accuracy even if the cutting edge of the tool 140 is worn. Furthermore, by executing the position information correction process while the workpiece W1 is being machined by the tool 140, the machine tool 1 can detect damage to the cutting edge of the tool 140.

[0040] Furthermore, when the tool setter 24 is selected so that the distance between a pair of contacts arranged 180 degrees apart and included in the detection unit 26 is the same as the diameter of the workpiece W1, the cutting edge position information is acquired at a position closer to the position of the tool 140 when the workpiece W1 is machined. Since the distance between a pair of contacts arranged 180 degrees apart and included in the detection unit 26 of the tool setter 24 is the same as the diameter of the workpiece W1, the accuracy of the cutting edge position information can be further improved.

[0041] In addition, since the tool setter 24 is attached to the front tool rest 21 which moves in accordance with the movement of the rear spindle 12, it is possible to obtain spindle position information and tool position information from the workpiece W1 and the tool 140 without having to arrange any additional components for moving the tool setter 24.

[0042] In the machine tool 1, the tool setter 24 is attached to the front tool rest 21 which moves in accordance with the movement of the rear spindle 12, but in the machine tool according to the embodiment, the contact sensor may be held by a moving body which moves the contact sensor.

[0043] Furthermore, in the machine tool 1, the detection unit 26 of the tool setter 24 has contact points arranged to detect the X1 and Y1 directions, but in the machine tool according to the embodiment, the detection unit of the tool setter may have contact points arranged to further detect the Z1 direction. By allowing the detection unit of the tool setter to further detect the Z1 direction, the distance between the cutting edge position of the tool 140 and the workpiece W1 can be generated as a three-dimensional coordinate system including a "longitudinal direction" indicating the Z1 direction in addition to a "diameter" indicating the X1 direction and a "center" indicating the Y1 direction.

[0044] Furthermore, in the machine tool according to the embodiment, the detection unit of the tool setter may have a contact portion arranged so as to be capable of detecting either the X1 direction or the Y1 direction. For example, when the detection unit of the tool setter is capable of detecting only the Y1 direction, the position information correction process is performed only for the Y1 direction. The detection unit of the tool setter may have only a single contact. When the detection unit of the tool setter has only a single contact, the tool setter is arranged so as to be rotatable around the Z1 direction.

[0045] Further, in the position information correction process described above, the guide bush device 13 that supports the workpiece W1 in a guidable manner is provided, but the machine tool according to the embodiment does not necessarily have to include the guide bush device 13.

Claims

1. A spindle that rotatably holds a workpiece; a tool rest on which a tool for machining the workpiece can be mounted; a movable body that is movable independently of the spindle and the tool rest; a contact-type sensor having a detection unit that detects a position of a target member by contacting the target member and that moves in accordance with the movement of the moving body; a control device that calculates center position information indicating a center position of the spindle based on position information indicating a position of a workpiece detected by bringing the detection unit into contact with the workpiece gripped by the spindle by moving the movable body, The control device is characterized in that it acquires cutting edge position information indicating the position of the cutting edge of the tool via the sensor by moving the movable body, and corrects the cutting edge position information based on the center position information.

2. 2. The machine tool according to claim 1, wherein the control device acquires the cutting edge position information by moving the movable body so that a center position of the sensor coincides with a center axis of the spindle, and by moving the tool rest to bring the cutting edge of the tool into contact with the sensor.

3. The detection unit has a cylindrical support member and a plurality of contacts arranged on a circumferential surface of the support member, 3. The machine tool according to claim 2, wherein moving the movable body so that the center position of the sensor coincides with the central axis of the spindle includes moving the movable body so that a central axis of a support member coincides with a central axis of the spindle.

4. The plurality of contacts include four contacts arranged at 90 degree intervals on a circumferential surface of the support member, 4. The machine tool according to claim 3, wherein a distance between a pair of the four contact points that are arranged 180 degrees apart is equal to a diameter of the workpiece.

5. The machine tool according to any one of claims 1 to 4, wherein the movable body is a back spindle that can be arranged opposite to the spindle.

6. A spindle that rotatably holds a workpiece; a tool rest on which a tool for machining the workpiece can be mounted; a movable body that is movable independently of the spindle and the tool rest; a contact-type sensor having a detection unit that detects a position of a target member by contacting the target member and that moves in accordance with the movement of the moving body; a control device that calculates central position information indicating a central position of the spindle based on position information indicating a position of a workpiece detected by bringing the detection unit into contact with the workpiece gripped by the spindle by moving the movable body, the central position information indicating a central position of the spindle being calculated, the central position information being calculated based on position information indicating a position of the workpiece detected by the detection unit by moving the movable body, the central position information being calculated based on position information indicating a central position of the spindle acquiring cutting edge position information indicating a position of a cutting edge of the tool via the sensor by moving the movable body; correcting the cutting edge position information based on the center position information; A position correction method comprising:

7. A spindle that rotatably holds a workpiece; a tool rest on which a tool for machining the workpiece can be mounted; a movable body having a detection unit that detects a position of a target workpiece by contacting the target workpiece, the movable body being movable independently of the spindle and the tool rest; A contact sensor that moves in accordance with the movement of the moving body; a control device that calculates center position information indicating a center position of the spindle based on position information indicating a position of a workpiece detected by bringing the detection unit into contact with the workpiece gripped by the spindle by moving the movable body, By moving the movable body, cutting edge position information indicating a position of a cutting edge of the tool is acquired via the sensor; correcting the cutting edge position information based on the center position information; A position correction program for causing the control device to execute a process.

Images