Machine tool, position information correction method, and computer program product

Abstract

The present application relates to a machine tool, a position information correction method, and a position information correction program. The machine tool has: a spindle that rotatably holds a workpiece; a tool holder that can be provided with a tool that processes the workpiece; a moving body that can be moved independently from the spindle and the tool holder; a contact sensor that moves along with the movement of the moving body; and a control device that calculates center position information indicating a center position of the spindle based on spindle position information acquired via the sensor, the sensor being moved to the vicinity of the workpiece by moving the moving body, the control device acquiring edge position information indicating a position of an edge of the tool via the sensor by moving the moving body, and correcting the edge position information based on the center position information.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a machine tool, a position information correction method, and a computer program product. BACKGROUND

[0002] Various techniques are known for detecting the position of a tool machining a workpiece in a machine tool such as a turning center or a machining center. For example, a technique is known in which a tool is manually abutted against 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 to an NC device as an offset. In addition, a technique is known in which a tool holder, which has been adjusted in advance in the position of the tool by a measuring jig called a preset device, is attached to a machine tool, which is also called off-machine preset. However, in these techniques, various problems arise such as an increase in the stop time of the machine tool and an increase in the labor of the operator.

[0003] To solve these problems, a technique is known in which the positional relationship between a workpiece and a tool is automatically measured in a machine tool. For example, in Japanese Patent Application Publication No. 2008-200798, a machine tool is disclosed which defines the position of the cutting edge of a tool 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, using the center coordinates of the workpiece measured by the probe as a reference position. In addition, in Japanese Patent Application Publication No. 2000-198047, a machine tool is described which calculates the position of the cutting edge of a tool with respect to the center line of a spindle based on the positional relationship between the tool and a sensor attached to a turret together with the sensor, and the center line of the spindle measured by abutting the detection portion of the sensor against a workpiece. SUMMARY

[0004] However, in the techniques described in Japanese Patent Application Publication No. 2008-200798 and Japanese Patent Application Publication No. 2000-198047, the center position of a workpiece is measured, but the position of the cutting edge of a tool is not measured. In the techniques described in Japanese Patent Application Publication No. 2008-200798 and Japanese Patent Application Publication No. 2000-198047, since the position of the cutting edge of a tool is not measured, when the position of the cutting edge of the tool is displaced due to heating or the like caused by machining of the workpiece or the like, the positional relationship between the workpiece and the tool can 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 of the present disclosure has a spindle that rotatably holds a workpiece, a tool holder that can be provided with a tool that processes the workpiece, a movable body that can be moved independently from the spindle and the tool holder, a contact sensor that moves along with the movement of the movable body, and a control device that calculates center position information indicating a center position of the spindle based on spindle position information acquired via the sensor, which is moved to the vicinity of the workpiece by moving the movable body, and acquires edge position information indicating a position of an edge of the tool via the sensor by moving the movable body, and corrects the edge position information based on the center position information.

[0007] Further, in the machine tool of the present disclosure, it is preferable that the control device move the movable body so that the center position of the sensor coincides with the center axis of the spindle, and move the tool holder so that the edge of the tool comes into contact with the sensor, thereby acquiring the edge position information.

[0008] Further, in the machine tool of the present disclosure, it is preferable that the sensor have a cylindrical support member and a detection portion having a plurality of contacts arranged on the peripheral surface of the support member, and moving the movable body so that the center axis of the support member coincides with the center axis of the spindle.

[0009] Further, in the machine tool of the present disclosure, it is preferable that the plurality of contacts include four contacts arranged at intervals of 90 degrees on the peripheral surface of the support member, and the distance between a pair of contacts arranged at an interval of 180 degrees among the four contacts be the same as the diameter of the workpiece.

[0010] Further, in the machine tool of the present disclosure, it is preferable that the movable body be a back spindle that can be arranged opposite the spindle.

[0011] In addition, the position correction method of the present disclosure is executed by a control device in a machine tool having a spindle that rotatably holds a workpiece, a tool holder that can be provided with a tool that processes the workpiece, a movable body that can be moved independently from the spindle and the tool holder, a contact sensor that moves along with the movement of the movable body, and a control device that calculates center position information indicating a center position of the spindle based on spindle position information acquired via the sensor, which is moved to the vicinity of the workpiece by moving the movable body, and acquires edge position information indicating a position of an edge of the tool via the sensor by moving the movable body, and corrects the edge position information based on the center position information.

[0012] Further, a position correction program of the present disclosure performs processing by a control device in a machine tool having: a spindle that rotatably holds a workpiece; a tool holder that can set a tool that processes the workpiece; a movable body that can move independently from the spindle and the tool holder; a contact sensor that moves along with movement of the movable body; and the control device that calculates center position information indicating a center position of the spindle based on spindle position information acquired via the sensor, the sensor moving to the vicinity of the workpiece by moving the movable body, the processing performed by the control device including: acquiring blade position information indicating a position of a blade of the tool via the sensor by moving the movable body, and correcting the blade position information based on the center position information.

[0013] The machine tool of the present disclosure can measure a positional relationship between a workpiece and a tool with high precision. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a perspective view of a machine tool of an embodiment.

[0015] Figure 2 is Figure 1 is a perspective view of a back-side spindle and a front-side tool holder disposed adjacent to the back-side spindle.

[0016] Figure 3 is a flowchart of a position information correction process performed by Figure 1

[0017] Figure 4 is a diagram for explaining the processing of S102 shown in Figure 3 is a diagram for explaining the processing of S102 shown in

[0018] Figure 5 is a diagram for explaining the processing of S103 shown in Figure 3 is a diagram for explaining the processing of S103 shown in DETAILED DESCRIPTION

[0019] Hereinafter, a machine tool, a control method of a machine tool, and a control program of a machine tool will be described with reference to the drawings. However, it should be understood that the present invention is not limited to the embodiments described below or the drawings.

[0020] Figure 1 is a perspective view of a machine tool of an embodiment.

[0021] ​The machine tool 1 has a bed 10, a front spindle 11, a back spindle 12, a guide bushing device 13, a tool holder 14, and an NC device 20. The front spindle 11, the back spindle 12, the guide bushing device 13, and the tool holder 14 are mounted on the bed 10. The front spindle 11 is a hollow member capable of holding a cylindrical workpiece Wl, and is movable in the Zl direction by a moving mechanism provided on a rail 15. The back spindle 12 is a hollow member capable of holding a cylindrical workpiece W2, and is movable in the Z2 direction and the X2 direction by a moving mechanism provided on rails 16 and 17. The guide bushing device 13 is fixed to the bed 10, and supports the workpiece Wl held by the front spindle 11 so as to be slidably guided in the Zl direction. The tool holder 14 is a member holding a plurality of tools that machine the workpieces Wl and W2 held by the front spindle 11 and the back spindle 12, and is movable in the Xl direction and the Yl direction by a moving mechanism provided on rails 18 and 19. The rotation or movement of the front spindle 11, the back spindle 12, and the tool holder 14 is controlled by the NC device 20 mounted on the machine tool 1. The front spindle 11, the back spindle 12, and the tool holder 14 are independently movable, that is, each of them is movable independently. The NC device 20 has an arithmetic circuit, a storage circuit storing a position correction program for performing a position correction process, and the like, and is a control device that instructs various actions of the machine tool. The position correction program can be installed in the management storage section 42 from a computer-readable removable recording medium such as a CD-ROM, a DVD-ROM, or the like, using a known setup program or the like.

[0022] Figure 2 FIG. 6 is a perspective view of the back spindle 12 and the front tool holder 21 disposed adjacent to the back spindle 12.

[0023] The front tool holder 21, also referred to as an opposed tool holder, is a member holding a rotary tool 22, a non-rotary tool 23, and a tool setting instrument 24, and moves integrally with the movement of the back spindle 12. The tool setting instrument 24 is a contact type position sensor having a cylindrical support member 25 and a detection portion 26 disposed on the peripheral surface of the top end of the support member 25. The detection portion 26 has four contacts disposed at intervals of 90 degrees on the peripheral surface of the support member 25, and the four contacts come into contact with an object member such as the workpiece Wl, thereby detecting the position of the object member from two directions each in the X2 and Y2 directions, for a total of four directions.

[0024] The gage 24 can make the four contacts contact the workpiece Wl as long as the distance between a pair of contacts included in the four contacts and spaced 180 degrees is smaller or larger than the diameter of the workpiece Wl to be machined. Further, it is preferable that the distance between the pair of contacts be the same as the diameter of the workpiece Wl by selecting the distance between the pair of contacts to be the same as the diameter of the workpiece Wl, so that the machining point of the workpiece Wl is approached more. Here, the distance between the pair of contacts is the same as the diameter of the workpiece Wl when the distance between the pair of contacts is 0.8 times or more and 1.2 times or less of the diameter of the workpiece Wl.

[0025] Figure 3 is a flowchart of the position information correction processing executed by the machine tool 1. Figure 3 The position information correction processing shown is executed in cooperation with the control of each element of the machine tool 1 according to an instruction from the NC device 20. In addition, Figure 3 The position information correction processing shown can be executed before the workpiece Wl is machined by the tool, or can be executed appropriately during the machining of the workpiece Wl by the tool. For example, Figure 3 The position information correction processing shown can be executed immediately after the machine tool 1 is started, can be executed before the machining of the workpiece Wl is started, or can be executed each time a prescribed number of machined workpieces are formed from the workpiece Wl.

[0026] First, the NC device 20 instructs the front spindle 11 to grip the workpiece Wl (S101). The front spindle 11 grips the workpiece Wl by a chuck not shown according to the instruction of the NC device 20.

[0027] Next, the NC device 20 instructs the acquisition of spindle position information indicating the position of the front spindle (S102).

[0028] Figure 4 is a diagram for explaining the processing of S102, Figure 4 (a) of is a perspective view of the rear spindle 12 and the guide sleeve device 13, Figure 4 (b) of is a front view of the guide sleeve device 13.

[0029] The NC device 20 moves the gage 24 to the vicinity of the workpiece Wl supported by the guide sleeve device 13 by moving the rear spindle 12. The NC device 20 acquires the spindle position information via the gage 24 moved to the vicinity of the workpiece Wl.

[0030] First, as shown by an arrow A in (b) of Figure 4 The NC device 20 brings the detection portion 26 of the gage 24 into contact with the workpiece Wl, and acquires first position information P1 indicating the upper end position of the workpiece Wl from the gage 24, as shown by an arrow A in (b) of Figure 4As shown by an arrow B in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the second position information P2 indicating the left end position of the workpiece Wl from the tool probe 24. Next, as shown by an arrow C in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the third position information P3 indicating the lower end position of the workpiece Wl from the tool probe 24. Next, as shown by an arrow D in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the fourth position information P4 indicating the right end position of the workpiece Wl from the tool probe 24. Then, the NC device 20 stores the first to fourth position information P1 to P4 acquired via the tool probe 24 as the spindle position information. Figure 4 As shown by an arrow C in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the third position information P3 indicating the lower end position of the workpiece Wl from the tool probe 24. Next, as shown by an arrow D in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the fourth position information P4 indicating the right end position of the workpiece Wl from the tool probe 24. Then, the NC device 20 stores the first to fourth position information P1 to P4 acquired via the tool probe 24 as the spindle position information. Figure 4 As shown by an arrow C in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the third position information P3 indicating the lower end position of the workpiece Wl from the tool probe 24. Next, as shown by an arrow D in (b), the NC device 20 brings the detection portion 26 of the tool probe 24 into contact with the workpiece Wl, and acquires the fourth position information P4 indicating the right end position of the workpiece Wl from the tool probe 24. Then, the NC device 20 stores the first to fourth position information P1 to P4 acquired via the tool probe 24 as the spindle position information.

[0031] Next, the NC device 20 calculates the center position information indicating the center position of the front spindle 11, based on the spindle position information acquired by the process of S102, via the tool probe 24 moved to the vicinity of the workpiece Wl by moving the back spindle 12 (S103).

[0032] The NC device 20 calculates the coordinate Px of the center position of the front spindle 11 in the XI direction, as the center value (P1+P3) / 2 of the first position information P1 indicating the coordinate of one side in the XI direction of the workpiece Wl and the third position information P3 indicating the coordinate of the other side in the XI direction of the workpiece Wl. Also, the NC device 20 calculates the coordinate Py of the center position of the front spindle 11 in the Yl direction, as the center value (P2+P4) / 2 of the second position information P2 indicating the coordinate of one side in the Yl direction of the workpiece Wl and the fourth position information P4 indicating the coordinate of the other side in the Yl direction of the workpiece Wl.

[0033] Next, the NC device 20 instructs the acquisition of the blade position information indicating the position of the blade of the tool (S104).

[0034] Figure 5 is a diagram for explaining the process of S104, Figure 5 (a) is a perspective view of the back spindle 12 and the guide bush device 13 (No. 1), Figure 5 (b) is a perspective view of the back spindle 12 and the guide bush device 13 (No. 2).

[0035] The NC device 20 moves the back spindle 12 so that the center position of the tool probe 24 coincides with the center axis of the front spindle 11, and moves the tool rest 14 so that the blade of the tool 140 held by the tool rest 14 comes into contact with the tool probe 24, thereby acquiring the blade position information.

[0036] First, as shown in (a) of FIG. 10, Figure 5As shown in (a), the NC device 20 moves the rear main shaft 12 in such a manner that the center axis of the support member 25 of the tool setting instrument 24 coincides with the center axis of the front main shaft 11 and the detection portion 26 of the tool setting instrument 24 approaches the workpiece Wl. The NC device 20 moves the rear main shaft 12 in such a manner that the positions of the center of the support member 25 of the tool setting instrument 24 in the Xl direction and the Yl direction coincide with the coordinates (Px, Py) indicated by the center position information calculated in the process of S103. Next, as shown in (b), the NC device 20 moves the rear main shaft 12 in such a manner that the cutting edge of the tool 140 approaches the tool setting instrument 24 from the Yl direction side of the tool holder 14. The NC device 20 acquires the first cutting edge position information K1 indicating the position of the lower end of the cutting edge of the tool 140 from the tool setting instrument 24. Next, as shown in (c), the NC device 20 moves the rear main shaft 12 in such a manner that the cutting edge of the tool 140 approaches the tool setting instrument 24 from the Xl direction side of the tool holder 14. The NC device 20 acquires the second cutting edge position information K2 indicating the position of the right end of the cutting edge of the tool 140 from the tool setting instrument 24. Based on the first cutting edge position information K1 and the second cutting edge position information K2, the NC device 20 calculates the coordinates (Kx, Ky) of the cutting edge of the tool 140 in the Xl direction and the Yl direction. Figure 5 As shown in (a), the NC device 20 moves the rear main shaft 12 in such a manner that the center axis of the support member 25 of the tool setting instrument 24 coincides with the center axis of the front main shaft 11 and the detection portion 26 of the tool setting instrument 24 approaches the workpiece Wl. The NC device 20 moves the rear main shaft 12 in such a manner that the positions of the center of the support member 25 of the tool setting instrument 24 in the Xl direction and the Yl direction coincide with the coordinates (Px, Py) indicated by the center position information calculated in the process of S103. Next, as shown in (b), the NC device 20 moves the rear main shaft 12 in such a manner that the cutting edge of the tool 140 approaches the tool setting instrument 24 from the Yl direction side of the tool holder 14. The NC device 20 acquires the first cutting edge position information K1 indicating the position of the lower end of the cutting edge of the tool 140 from the tool setting instrument 24. Next, as shown in (c), the NC device 20 moves the rear main shaft 12 in such a manner that the cutting edge of the tool 140 approaches the tool setting instrument 24 from the Xl direction side of the tool holder 14. The NC device 20 acquires the second cutting edge position information K2 indicating the position of the right end of the cutting edge of the tool 140 from the tool setting instrument 24. Based on the first cutting edge position information K1 and the second cutting edge position information K2, the NC device 20 calculates the coordinates (Kx, Ky) of the cutting edge of the tool 140 in the Xl direction and the Yl direction. Figure 5

[0037] Then, the NC device 20 corrects the cutting edge position information acquired in the process of S104 based on the center position information calculated in the process of S103 (S105). The NC device 20 corrects the coordinates (Kx, Ky) of the cutting edge of the tool 140 in the Xl direction and the Yl direction based on the coordinates (Px, Py) of the center position of the front main shaft 11 included in the center position information, and generates corrected coordinates (Cx, Cy). In the corrected coordinates (Cx, Cy), Cx is indicated as (Px - Kx), and Cy is indicated as (Py - Ky). The corrected coordinates (Cx, Cy) generated in the process of S105 are the distances from the position of the cutting edge of the tool 140 to the workpiece Wl, and Cx is also referred to as "diameter", and Cy is also referred to as "core".

[0038] Then, the position information correction process ends. After the position information correction process ends, the machine tool 1 performs a machining process on the workpiece Wl by the tool 140 at the tool cutting edge position corrected based on the position information correction process.

[0039] The machine tool 1 measures the positions of both the workpiece Wl and the tool 140 by the single tool setting instrument 24, and thus can correct the positional relationship between the workpiece Wl and the tool 140 with high accuracy.

[0040] In addition, the machine tool 1 makes the center position of the tool setting instrument 24 coincide with the center axis of the workpiece Wl, and thus can make the center position of the tool setting instrument 24 coincide with the center axis of the front main shaft 11 and make the tool setting instrument 24 approach the vicinity of the workpiece Wl (position at the time of machining).

[0041] ​In addition, in a state in which the tool setting instrument 24 is disposed in the vicinity of the workpiece W1, the machine tool 1 acquires the blade position information indicating the position of the blade of the tool 140 at a position close to the position at which the workpiece W1 is machined, and thus can acquire the blade position information with high precision as compared to a case in which the blade position information is acquired in a state in which the tool 140 is away from the workpiece W1.

[0042] In addition, after the center position information indicating the center position of the front spindle 11 is calculated, if a correction amount for the blade position information based on the center position information is stored in advance, the machine tool 1 can correct the positional relationship between the workpiece W1 and the tool 140 by the correction amount. In this case, the center axis of the workpiece W1 can not be made to coincide with the center position of the tool setting instrument 24.

[0043] In addition, the machine tool 1 performs the position information correction process during machining of the workpiece W1 by the tool 140, and thus can correct the positional relationship between the blade of the tool 140 and the workpiece W1 with high precision even in a case in which the blade of the tool 140 is worn. In addition, the machine tool 1 performs the position information correction process during machining of the workpiece W1 by the tool 140, and thus can detect breakage of the blade of the tool 140.

[0044] In addition, in a case in which the distance between a pair of contacts included in the detection portion 26 and disposed 180 degrees apart is the same as the diameter of the workpiece W1, the tool setting instrument 24 acquires the blade position information at a position closer than the position of the tool 140 at the time of machining of the workpiece W1. Since the distance between the pair of contacts included in the detection portion 26 and disposed 180 degrees apart is the same as the diameter of the workpiece W1, the tool setting instrument 24 can further improve the precision of the blade position information.

[0045] In addition, since the tool setting instrument 24 is mounted on the front tool rest 21 that moves along with the movement of the back spindle 12, the spindle position information and the tool position information can be acquired from the workpiece W1 and the tool 140 without the need to additionally provide a member for movement of the tool setting instrument 24.

[0046] In the machine tool 1, the tool setting instrument 24 is mounted on the front tool rest 21 that moves along with the movement of the back spindle 12, but in the machine tool of the embodiment, the contact sensor only needs to be held by a moving body that moves the contact sensor.

[0047] Further, in the machine tool 1, the detection portion 26 of the tool setting gauge 24 is configured with the contact portion so as to detect the X1 direction and the Y1 direction, but in the machine tool of the embodiment, the detection portion of the tool setting gauge can also be configured with the contact portion so as to be able to further detect the Z1 direction. By the detection portion of the tool setting gauge being able to further detect the Z1 direction, it is possible to generate the distance between the blade position of the tool 140 and the workpiece W1 as a three-dimensional coordinate including a "length" representing the Z1 direction in addition to a "diameter" representing the X1 direction and a "core" representing the Y1 direction.

[0048] Further, in the machine tool of the embodiment, the detection portion of the tool setting gauge can also be configured with the contact portion so as to be able to detect either of the X1 direction and the Y1 direction. For example, when the detection portion of the tool setting gauge is able to detect only the Y1 direction, the position information correction processing performs the position information correction processing only for the Y1 direction. The detector of the tool setting gauge can have only a single contact. When the detection portion of the tool setting gauge has only a single contact, the tool setting gauge is configured so as to be able to rotate around the Z1 direction.

[0049] Further, in the position information correction processing explained above, the guide sleeve device 13 that is able to guideably support the workpiece W1 is provided, but the machine tool of the embodiment can also not have the guide sleeve device 13.

Claims

1. A machine tool, characterized by having: a spindle which rotatably holds a workpiece; a tool holder which is capable of setting a tool for machining the workpiece; a moving body which is capable of moving independently from the spindle and the tool holder; a contact sensor which has a support member which moves integrally with the moving body, and a detection portion which is disposed on a peripheral surface of a tip end of the support member and detects a position of an object member by coming into contact with the object member; and a control device which calculates center position information indicating a center position of the spindle based on position information indicating a position of the workpiece detected by moving the moving body so that the detection portion comes into contact with the workpiece held by the spindle, the control device acquires blade position information indicating a position of a blade of the tool via the sensor by moving the moving body, and corrects the blade position information based on the center position information.

2. The machine tool according to claim 1, wherein the control device moves the moving body so that a center position of the sensor coincides with a center axis of the spindle, and moves the tool holder so that the blade of the tool comes into contact with the sensor, thereby acquiring the blade position information.

3. The machine tool according to claim 2, wherein the detection portion has a plurality of contact points disposed on the peripheral surface of the tip end of the support member, the moving of the moving body so that the center position of the sensor coincides with the center axis of the spindle includes moving the moving body so that a center axis of the support member coincides with the center axis of the spindle.

4. The machine tool according to claim 3, wherein the plurality of contact points include four contact points disposed at every 90 degrees on the peripheral surface of the support member, a distance between a pair of the contact points disposed at every 180 degrees among the four contact points is the same as a diameter of the workpiece.

5. The machine tool according to any one of claims 1 to 4, wherein the moving body is a back spindle which is capable of being disposed opposite to the spindle. in a machine tool, 6. A position correction method characterized by, the machine tool has: a spindle which rotatably holds a workpiece; a tool holder which is capable of setting a tool for machining the workpiece; a moving body which is capable of moving independently from the spindle and the tool holder; a contact sensor which has a support member which moves integrally with the moving body, and a detection portion which is disposed on a peripheral surface of a tip end of the support member and detects a position of an object member by coming into contact with the object member; and a control device which calculates center position information indicating a center position of the spindle based on position information indicating a position of the workpiece detected by moving the moving body so that the detection portion comes into contact with the workpiece, the position correction method includes: acquiring blade position information indicating a position of a blade of the tool via the sensor by moving the moving body, correcting the blade position information based on the center position information. the computer program for position correction causes a control device of a machine tool to execute processing, the machine tool has:

7. A computer program product comprising a computer program for position correction, characterized in that ​ ​ a main shaft that rotatably holds a workpiece; a tool holder that is capable of holding a tool that processes the workpiece; a movable body that is capable of moving independently from the main shaft and the tool holder; a contact sensor that has a support member that moves integrally with the movable body, and a detection portion that is disposed on a peripheral surface of a tip end of the support member and detects a position of an object member by coming into contact with the object member; and a control device that calculates center position information that indicates a center position of the main shaft based on position information that indicates a position of the workpiece detected by bringing the detection portion of the contact sensor into contact with the workpiece held by the main shaft by moving the movable body, the control device performs processing as follows: acquires blade position information that indicates a position of a blade of the tool via the sensor by moving the movable body, corrects the blade position information based on the center position information. ​

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