Machine tool

Abstract

To provide a machine tool which can detect a chip of a blade of a tool.SOLUTION: A machine tool includes a tool, a measuring device, and blade chip detection means. In the tool, blades are provided at an outer periphery part. The measuring device is used to measure a shape of the tool. The blade chip detection means detects a difference between a pre-processing shape, a shape of the tool before use for processing of a workpiece, and a post-processing shape, a shape of the tool after the use for the processing of the workpiece which is measured by the measuring device, being larger than or equal to a predetermined threshold value to detect at least one blade chip of the tool after the processing.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a machine tool. [Background technology]

[0002] Patent Document 1 discloses a machine tool capable of detecting breakage of a tool such as a drill attached to a spindle. The machine tool described in Patent Document 1 uses a laser device to detect breakage of the tool. The laser device includes a light emitter capable of emitting laser light and a photoreceiver that receives the laser light emitted from the light emitter. The machine tool described in Patent Document 1 moves the tool so that the tip of the tool passes through the laser light, and if the photoreceiver stops receiving the laser light during this time, it determines that the tool is not broken, and if the photoreceiver continues to receive the laser light, it determines that the tool has broken and become shorter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-343310 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the method for detecting tool breakage described in Patent Document 1, for example, if the tool has a chipped edge on its outer periphery but the length of the tool itself remains unchanged, it is determined that the tool is not broken. In this case, the tool with the chipped edge is used to machine a workpiece (material to be cut), but this may result in a decrease in the machining accuracy of the workpiece.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a machine tool capable of detecting chipping of a tool edge. [Means for solving the problem]

[0006] The present invention includes a tool having a plurality of blades provided on an outer periphery thereof, a measuring device for measuring a shape of the tool, and blade chipping detection means for detecting chipping of at least one of the blades of the tool after machining by detecting that a difference between a pre-machining shape of the tool that is the shape of the tool before it is used to machine a workpiece and a post-machining shape of the tool that is the shape of the tool after it has been used to machine the workpiece measured by the measuring device is equal to or greater than a predetermined threshold value. a machining condition acquisition means for acquiring machining conditions for a next machining of the workpiece using the tool after the machining; and a threshold calculation means for calculating the threshold based on the machining conditions acquired by the machining condition acquisition means; The present invention provides a machine tool comprising: Effect of the Invention

[0007] According to the present invention, it is possible to provide a machine tool capable of detecting chipping of a tool edge. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic overall configuration diagram of a machine tool according to an embodiment. [Diagram 2] FIG. 2 is a flowchart of a process performed by a tool check means in the embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing a method for measuring the length from the origin position of the mechanical coordinate system to the laser light in the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a method for measuring the protruding length of a tool from a holder in the embodiment. [Diagram 5] FIG. 5(a) is a side view of a flat end mill in an embodiment, and FIG. 5(b) is a schematic diagram showing the positional relationship between the flat end mill and a laser light when measuring the protruding length of the flat end mill from a holder in an embodiment. [Figure 6] FIG. 6(a) is a side view of a drill in the embodiment, and FIG. 6(b) is a schematic diagram showing the positional relationship between the drill and a laser light when measuring the protruding length of the drill from a holder in the embodiment. [Figure 7] FIG. 7 is a flowchart showing a process for detecting chipping of a tool edge in the embodiment. [Figure 8]FIG. 8(a) is a schematic diagram for explaining a method for tracing the shape of the cutting edge of a tool, and FIG. 8(b) is a diagram showing an example of a light-blocking detection signal. [Figure 9] FIG. 9(a) is a schematic diagram for explaining a method for tracing the shape of the cutting edge of a tool that is partially chipped, and FIG. 9(b) is a diagram showing an example of a light-blocking detection signal. [Figure 10] FIG. 10 is a diagram showing a pre-machining shape, an edge chipping limit line, and a post-machining shape in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Embodiment Mode] An embodiment of the present invention will be described with reference to Figures 1 to 10. Note that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and while there are some parts that specifically exemplify various technical matters that are technically preferable, the technical scope of the present invention is not limited to this specific embodiment.

[0010] (Configuration of machine tool 1) 1 is a schematic overall configuration diagram of a machine tool 1 according to the present embodiment. In this embodiment, the vertical direction of the machine tool 1 in use is referred to as the Z direction. In addition, hereinafter, the expressions "upper" and "lower" refer to the vertical direction of the machine tool 1 in use.

[0011] The machine tool 1 in this embodiment is, for example, a three-axis vertical machining center equipped with a control device 2 that controls the movement of a tool 3 attached to a spindle 16 and the like in accordance with an NC program. However, the machine tool 1 is not limited to this, and other machine tools 1 such as a vertical machining center with four or more axes including the rotation direction of a table 13 and a spindle 16, a horizontal machining center, a turning center, etc. The machine tool 1 includes a bed 11, a saddle 12, a table 13, a column 14, a spindle head 15, a spindle 16, a tool 3, a measuring device 4, and a control device 2.

[0012] A guide surface 111 extending in a Y direction perpendicular to the Z direction is provided on the upper surface of the bed 11. The guide surface 111 guides the saddle 12 arranged on the bed 11 in the Y direction. A guide surface 121 extending in an X direction perpendicular to both the Y direction and the Z direction is provided on the upper surface of the saddle 12. The guide surface 121 guides the table 13 arranged on the saddle 12 in the X direction. The Y direction moving means of the saddle 12 relative to the bed 11 and the X direction moving means of the table 13 relative to the saddle 12 can be realized using, for example, a ball screw and a servo motor (not shown), and the amount of movement of the table 13 is output to the control device 2 from an encoder provided on the output shaft of the servo motor.

[0013] A column 14 is provided at the end of the upper surface of the bed 11 in the Y direction. In this embodiment, the column 14 is fixed to the bed 11. Hereinafter, the side of the bed 11 in the Y direction where the column 14 is provided is referred to as the rear, and the opposite side is referred to as the front. The column 14 has a portion erected upward from the upper surface of the bed 11 and a portion protruding from the upper end of the portion toward the tip side, and is approximately L-shaped. A guide surface 141 extending in the Z direction is provided on the front surface of the column 14. The guide surface 141 guides the spindle head 15 arranged in front of the column 14 in the Z direction. The movement means of the spindle head 15 in the Z direction relative to the column 14 can be realized using, for example, a ball screw and a servo motor, and the movement amount of the spindle head 15 is output to the control device 2 from an encoder provided on the output shaft of the servo motor. The control device 2 is configured to be able to obtain the position of a reference point 150 (see Figures 3 and 4) of the spindle head 15 based on the movement amounts of various movement means output from the encoder. The reference point 150 of the spindle head 15 is a coordinate point acquired by the control device 2, and in this embodiment, is the lower end position of the spindle head 15 in the Z direction, and is the position where the central axis of the spindle 16 exists in the X and Y directions.

[0014] The spindle head 15 is provided with a spindle 16 to which a tool such as a cutting tool, such as an end mill or a drill, is attached. The spindle 16 is configured to detachably hold the tool 3 and to rotate the held tool 3. The spindle 16 is also called a spindle or a shaft.

[0015] On the table 13, as described later, a measuring device 4 is fixed for measuring the dimensions of the tool 3 and detecting chipping of the tool 3. In this embodiment, the measuring device 4 is a laser device, and is referred to as the laser device 4 in this embodiment. The laser device 4 has a U-shape that opens upward, and includes an irradiating unit 41 that irradiates a laser beam 43 in the X direction and a light receiving unit 42 that receives the laser beam 43 irradiated from the irradiating unit 41, at positions facing each other in the X direction. The laser device 4 is configured such that when the laser beam 43 is blocked by an object, the light receiving unit 42 outputs a skip signal to the control device 2. The control device 2 stores the coordinate position of a reference point 150 (see FIG. 3 and FIG. 4) of the spindle head 15 at the time when the skip signal is received.

[0016] The control device 2 controls the movement of the saddle 12 in the Y direction relative to the bed 11, the movement of the table 13 in the X direction relative to the saddle 12, and the movement of the spindle head 15 in the Z direction relative to the column 14, thereby controlling the movement of the spindle head 15. When machining a workpiece with the machine tool 1, the control device 2 moves the tool 3 attached to the spindle 16 along a tool path (CL: Cutter Location) generated by a CAM device 6 having a CAM (Computer Aided Manufacturing) function based on a target shape of the workpiece created using, for example, a CAD device 5 having a CAD (Computer Aided Design) function. The control device 2 performs post-processing to convert the tool path data generated by the CAM device 6 into an NC (Numerical Control) program that can be read by the machine tool 1.

[0017] The control device 2 includes a control unit 21 having a CPU (arithmetic processing unit) and a RAM which serves as a calculation area when the CPU is in operation, and a storage unit 22 including a ROM. The storage unit 22 stores programs for implementing various functions performed by the control device 2, position information of the laser device 4 in the machine tool 1, the focal position of the laser, and the like. The control unit 21 includes a machining condition acquisition means 211, a tool check means 212, a machining means 213, an edge chipping detection means 214, and a threshold calculation means 215, and realizes various functions by the CPU executing the programs stored in the storage unit 22.

[0018] (Processing by the processing condition acquisition means 211) The machining condition acquisition means 211 acquires machining conditions such as the type, number of blades, diameter, length, feed speed of the tool 3 relative to the workpiece, rotation speed of the tool 3 during machining, tool path, etc. of the tool 3 used in machining from the CAM device 6, and stores them in the storage unit 22. The machining condition acquisition means 211 acquires the above-mentioned machining conditions from the CAM device 6 via an interface that communicates with the CAM device 6 by wired or wireless communication means.

[0019] (Processing by tool check means 212) Fig. 2 is a flowchart of the process performed by the tool check means 212. As shown in Fig. 2, the tool check means 212 first checks the tool runout. In the tool runout check, in step S1, the tool 3 is rotated at the rotation speed during machining, and the radius R' [mm] of the tool 3 is measured using the laser device 4.

[0020] In measuring the radius R' of the tool 3 in step S1, the Y-direction moving means of the saddle 12 relative to the bed 11, the X-direction moving means of the table 13 relative to the saddle 12, and the Z-direction moving means of the spindle head 15 relative to the column 14 are controlled to move the spindle head 15 so that the tool 3 is located near the laser beam 43. Then, the spindle 16 and the tool 3 fixed to the spindle 16 are rotated around the central axis of the spindle 16 and approach the laser beam 43 from one side in the Y direction. Then, when the tool 3 interrupts the laser beam 43, a skip signal is output from the light receiving unit 42, and the Y-direction position of the reference point 150 of the spindle head 15 when the tool 3 interrupts the laser beam 43 (i.e., the position separated by the radius of the tool 3 from the laser beam 43) is read from the encoders provided on the various servo motors. Then, the radius R' of the tool 3 is measured from the measured Y-direction position of the reference point 150 of the spindle head 15 and the Y-direction position of the laser light 43 stored in the memory unit 22. Here, the Z-direction position of the tool 3 where the radius R' is measured can be changed according to the type of the tool 3. For example, if the tool 3 is a ball end mill, the radius of the tool 3 is measured at a position shifted upward from the lower end position of the tool 3 by a length equivalent to the ball radius of the ball end mill acquired from the CAM device 6 (for example, ball radius + 0.1 mm, etc.). Also, if the tool 3 is a flat end mill, the radius of the tool 3 is measured at the outer periphery of the lower end position of the tool 3. This measures the radius of the main part (machined part) of the tool 3. The correspondence between the type and shape of the tool 3 and the Z-direction position of the tool 3 where the radius of the tool 3 is measured is stored in advance in the memory unit 22, and the Z-direction position of the tool 3 where the radius of the tool 3 is measured is automatically output by acquiring the type and shape of the tool 3 from the CAM device 6.

[0021] Then, as shown in step S1 of FIG. 2, the measured radius R' of the tool 3 and the theoretical radius value R [mm] of the tool 3 acquired by the machining condition acquisition means 211 from the CAM device 6 are used to determine whether the measured radius R' of the tool 3 and the theoretical radius value R satisfy R'≦(R+0.005 mm). The 0.005 mm in the inequality R'≦(R+0.005 mm) is the allowable runout amount of the tool 3, and can be changed appropriately depending on the type of the tool 3, the dimensional tolerance of the product formed after the workpiece is machined, and the like. If the measured radius R' of the tool 3 exceeds R+0.005 mm, the process proceeds to step S2, where it is determined that the tool 3 is excessively runout toward the outer periphery due to rotation, and an alarm is issued. On the other hand, if the measured radius R' of the tool 3 is equal to or less than R+0.005 mm, it is determined that no tool runout is occurring, and the process proceeds to the next step of tool length confirmation.

[0022] Next, the tool length is confirmed. In the tool length confirmation, the laser device 4 is used to measure the protruding length L' of the tool 3 from the holder 18 in the Z direction in step S3.

[0023] A method for measuring the protruding length L' in step S3 will be described with reference to Figs. 3 and 4. First, as shown in Fig. 3, the master bar 7 whose Z-direction length A has been measured in advance with high accuracy is attached to the spindle 16. Then, the spindle head 15 and the master bar 7 are lowered from a position where the reference point 150 of the spindle head 15 is at the height in the Z direction of the origin position 17 of the machine coordinates to a position where the lower end of the master bar 7 blocks the laser light 43. When the lower end of the master bar 7 blocks the laser light 43, a skip signal is output from the light receiving unit 42, and the length B from the origin position 17 to the reference point 150 of the spindle head 15 is obtained based on information read from the encoders provided on various servo motors. Then, the sum C=A+B of the known Z-direction length A of the master bar 7 and the measured length B from the origin position 17 to the reference point 150 of the spindle head 15 is calculated. This length C is the Z-direction length from the origin position 17 to the laser light 43. In this way, the Z-direction length C from the origin position 17 to the laser beam 43 is acquired in advance. Here, for example, when multiple workpieces are continuously machined, the use of the machine tool 1 causes the area around the spindle 16 to become hot while other areas become relatively cold, which may cause thermal deformation such as warping of the column 14, resulting in an error in the result of the length C measured by the laser device 4. For this reason, the length C is measured every time the workpiece to be machined is changed.

[0024] Then, as shown in FIG. 4, when measuring the protruding length L' of the tool 3 attached to the spindle 16 from the holder 18, first, the positions of the reference point 150 and the laser light 43 when viewed from the Z direction are adjusted as follows. First, when measuring the protruding length L' of the tool 3 such as the flat end mill 31 or the reamer whose tip (lower end) is at least located at a position away from the central axis of the tool 3 toward the outer periphery as shown in FIG. 5(a), the position of the outer periphery end of the tool 3 when viewed from the Z direction is made to coincide with the focal position of the laser light 43 as shown in FIG. 5(b). When measuring the protruding length L' of the tool 3 such as the drill 32 or the ball end mill whose tip (lower end) is located on the central axis of the tool 3 as shown in FIG. 6(a), the center position (reference point 150) of the tool 3 when viewed from the Z direction is made to coincide with the focal position of the laser light 43 as shown in FIG. 6(b). This is to ensure that the tool 3 is focused and measured during tool shape measurement, thereby ensuring measurement accuracy. Here, the positional relationship between the tool 3 and the focal position of the laser beam 43 when viewed from the Z direction is automatically output by the machining condition acquisition means 211 using information such as the type and shape of the tool 3 acquired from the CAM device 6. The relationship between the type and shape of the tool 3 and the positional relationship between the reference point 150 of the spindle head 15 and the laser beam 43 is stored in advance in the storage unit 22.

[0025] Next, the master bar 7 is removed from the spindle 16, and the tool 3 is attached to the spindle 16 via the holder 18. Then, as shown in FIG. 4, the spindle head 15, the spindle 16, and the tool 3 are lowered from a position where the reference point 150 of the spindle head 15 is at the height in the Z direction of the origin position 17 of the machine coordinates to a position where the tool 3 blocks the laser light 43. When the lower end of the tool 3 blocks the laser light 43, a skip signal is output from the light receiving unit 42, and a length Bα from the origin position 17 to the reference point 150 of the spindle head 15 is obtained based on information read from the encoders provided on the various servo motors. Then, the length D from the reference point 150 of the spindle head 15 to the lower end position of the tool 3 is obtained by subtracting the length Bα from the length C in the Z direction from the origin position 17 to the laser light 43 obtained in advance as described above. Here, the tool 3 is attached to the spindle 16 via a holder 18, and the holder 18 used has a known length E in the Z direction that has been accurately measured in advance. Therefore, the protruding length L' of the tool 3 in the Z direction from the holder 18 is obtained by subtracting the known length E of the holder 18 in the Z direction from the length D. In this manner, the protruding length L' is obtained.

[0026] Then, as shown in FIG. 2, in step S3, it is determined whether the measured protrusion length L' and the theoretical protrusion length L of the tool 3 acquired by the machining condition acquisition means 211 from the CAM device 6 satisfy L < L' ≤ (L + 3 mm). The 3 mm in the inequality L < L' ≤ (L + 3 mm) is the allowable value of the difference between the actual length L' of the tool and the theoretical protrusion length L, and can be appropriately changed according to the type of the tool 3, the dimensional tolerance of the product formed after the workpiece machining, etc. When the measured protrusion length L' of the tool 3 is shorter than the theoretical protrusion length L of the tool 3 used when calculating the tool path by the CAM device 6, there is a risk that the holder 18 may interfere with the workpiece during machining, and when the measured length L' of the tool 3 is greater than the predetermined length (L + 3 mm), it may cause machining defects. Therefore, when the measured protrusion length L' of the tool 3 and the theoretical protrusion length L do not satisfy L < L' ≤ (L + 3 mm), in step S4, it is determined that there is an abnormality in the attachment of the tool 3 to the holder 18 and an alarm is issued. On the other hand, when the measured protrusion length L' of the tool 3 and the theoretical protrusion length L satisfy L < L' ≤ (L + 3 mm), it is determined that the attachment of the tool 3 to the holder 18 is normal, and the process proceeds to the next step, which is the tool diameter measurement.

[0027] Next, the tool diameter is confirmed. In the tool diameter confirmation, in step S5, the diameter OD' [mm] of the tool 3 in the state where the tool 3 is stationary (non-rotating state) is measured using the laser device 4.

[0028] A method for measuring the diameter OD' of the stationary tool 3 in step S5 will be described. First, the tool 3 is brought closer to the laser beam 43 from one side in the Y direction, and the Y-direction position of the reference point 150 when the tool 3 contacts the laser beam 43 is measured. Similarly, the tool 3 is brought closer to the laser beam 43 from the other side in the Y direction, and the Y-direction position of the reference point 150 when the tool 3 contacts the laser beam 43 is measured. Then, based on the difference between these measured values, the length from one end to the other end of the tool 3 is calculated. Such length is calculated repeatedly a plurality of times while changing the posture by rotating the tool 3 around its central axis by a predetermined angle each time, and the maximum value of each calculated value is taken as the diameter of the tool 3. Note that the measurement position of the diameter of the tool 3 in the Z direction can be the same as the measurement position of the radius R' in the Z direction in step S1.

[0029] Then, based on the measured diameter OD' of the tool 3 and the theoretical diameter value OD [mm] of the tool 3 acquired by the machining condition acquisition means 211 from the CAM device 6, it is determined whether the measured diameter OD' of the tool 3 and the theoretical diameter value OD satisfy (OD - 0.5 mm) < OD' < (OD + 0.5 mm). That is, it is confirmed whether the measured diameter OD' of the tool 3 is equivalent to the theoretical diameter value OD of the tool 3 acquired from the CAM device 6. The 0.5 mm in the inequality (OD - 0.5 mm) < OD' < (OD + 0.5 mm) is the allowable value of the difference between the actual diameter OD' of the tool 3 and the theoretical diameter value OD, and can be appropriately changed according to the type of the tool 3, the dimensional tolerance of the product formed after workpiece machining, etc. When the measured diameter OD' of the tool 3 and the theoretical diameter value OD do not satisfy (OD - 0.5 mm) < OD' < (OD + 0.5 mm), in step S6, it is assumed that a tool different from the intended tool 3 (the tool 3 set when creating the tool path by the CAM device 6) may be attached to the spindle 16, and an alarm is issued. On the other hand, when the measured diameter OD' of the tool 3 and the theoretical diameter value OD satisfy (OD - 0.5 mm) < OD' < (OD + 0.5 mm), it is assumed that the intended tool 3 is attached to the spindle 16, and the tool check is terminated.

[0030] (Processing by the processing means 213) The machining means 213 machines the workpiece by controlling the means for moving the saddle 12 in the Y direction relative to the bed 11, the means for moving the table 13 in the X direction relative to the saddle 12, and the means for moving the spindle head 15 in the Z direction relative to the column 14, in accordance with an NC program generated by post-processing the tool path data acquired by the machining condition acquisition means 211 from the CAM device 6. The NC program includes commands related to machining conditions such as the feed speed of the tool 3 relative to the workpiece, the rotation speed of the tool 3, and the tool path of the tool 3.

[0031] (Processing by the chipped edge detection means 214 and the threshold value calculation means 215) The chipped edge detection means 214 detects whether or not a chip has occurred in the tool 3 after it has been used in machining by the machining means 213. Fig. 7 shows a flowchart of the chipped edge detection.

[0032] In step Sa, the chipped edge detection means 214 first measures (traces) the shape (before-machining shape 301) of the cutting edge 33 (see FIG. 5(a)) of the tool 3 before machining using the laser device 4. FIG. 8(a) is a schematic diagram for explaining a method for tracing the shape of the cutting edge 33 of the tool 3 without chipping. In FIG. 8(a), one tool 3 and a laser beam 43 for tracing it are shown in a time series in which time advances toward the right. Here, the tool 3 is an end mill 31 (see FIG. 5(a)), and is assumed to have four blades extending in a spiral shape. For convenience, the four blades of the tool 3 are called the first blade portion 3a, the second blade portion 3b, the third blade portion 3c, and the fourth blade portion 3d in the order of the counter-rotation direction of the tool 3 at the time of tracing. In addition, in FIG. 8(a), for convenience, a "1" is indicated on the first blade portion 3a, a "2" on the second blade portion 3b, a "3" on the third blade portion 3c, and a "4" on the fourth blade portion 3d.

[0033] When tracing the shape of the cutting edge 33 of the tool 3 using the laser device 4, the chipping detection means 214 controls various servo motors to move the spindle head 15, and moves the tool 3 so that the lower end position of the tool 3 and the laser light 43 are at the same position in the Z direction. Then, as shown in FIG. 8(a), the tool 3 is rotated once and the laser light 43 is irradiated to each cutting edge 33. Here, the chipping detection means 214 synchronizes the irradiation timing of the laser light 43 by the laser device 4 with the rotation speed of the tool 3 so that the laser light 43 is irradiated only when the cutting edges 33 of the first cutting portion 3a, the second cutting portion 3b, the third cutting portion 3c, and the fourth cutting portion 3d of the tool 3 come to the end position on the laser light 43 side in the Y direction (the upper end position of the tool 3 on the paper in FIG. 8(a)) when the tool 3 is rotated. Therefore, the chipped edge detection means 214 rotates the tool 3 once and detects whether or not each of the laser beams 43 irradiated four times during the one rotation has been blocked. This operation is performed multiple times, starting from a position where the tool 3 is not hit by the laser beam 43, while gradually decreasing the relative distance in the Y direction between the laser beam 43 and the tool 3. Then, the position of each cutting edge 33 at the bottom end position of the tool 3 is detected from the positional relationship between the reference point 150 and the laser beam 43 when the laser beam 43 is blocked by each cutting edge 33.

[0034] Here, when the laser light 43 is blocked while being irradiated (i.e., the light receiving unit 42 does not receive the laser light 43), the blade chipping detection means 214 is configured to receive an interruption detection signal from the laser device 4. FIG. 8(b) shows an example of a light interruption detection signal detected when all of the laser light 43 irradiated four times is interrupted by the cutting edge 33 of each blade of the tool 3 when the tool 3 rotates once. In FIG. 8(b), t1 is the time when the cutting edge 33 of the first blade portion 3a is irradiated with the laser light 43, t2 is the time when the cutting edge 33 of the second blade portion 3b is irradiated with the laser light 43, t3 is the time when the cutting edge 33 of the third blade portion 3c is irradiated with the laser light 43, and t4 is the time when the cutting edge 33 of the fourth blade portion 3d is irradiated with the laser light 43. In this way, when all of the laser light 43 irradiated four times per rotation is blocked, the light blocking detection signal is detected without interruption.

[0035] Then, the detection of the position of each cutting edge 33 of the tool 3 is repeated up to a position that is a predetermined length away from the lower end position of the tool 3. In this embodiment, the detection is repeated up to a position that is 20 mm away from the lower end position of the tool 3. Here, since each blade is formed in a spiral shape, when the tool 3 is shifted downward with respect to the laser light 43, the position of each cutting edge 33 is shifted in the rotation direction. In consideration of this, the cutting edge detection means 214 synchronizes the irradiation timing of the laser light 43 by the laser device 4 with the rotation of the tool 3 so that the laser light is irradiated only when the cutting edge 33 of each blade of the tool 3 comes to the position of the end on the laser light 43 side in the Y direction, regardless of the position of the cutting edge 33 of the tool 3 in the Z direction.

[0036] As described above, the shape of the cutting edge 33 of the tool 3 before machining (before-machining shape 301) is traced. The tracing result for the before-machining shape 301 is shown by a dashed line in Fig. 10. The diagram shown in Fig. 10 corresponds to a part of the outer shape of the cutting edge 33 of the tool 3 as viewed from below.

[0037] Then, in step Sb, the machining conditions for the next machining (i.e., the second machining) of the workpiece using the tool 3 after the first machining are acquired from the CAM device 6. Then, in step Sc, after the first machining of the workpiece using the tool 3, the threshold calculation means 215 calculates the allowable amount of chipping of the blade (allowable amount of chipping W) as shown in FIG. 10 based on the traced before-machining shape 301 and the machining conditions for the next machining (i.e., the second machining) of the workpiece using the tool 3 after the first machining, acquired from the CAM device 6. The machining conditions include conditions related to rough machining and finish machining performed after the rough machining. Rough machining does not require high machining accuracy compared to finish machining, and chipping of the tool 3 is relatively easily tolerated, while finish machining requires high machining accuracy compared to rough machining, and the allowable amount of chipping W of the tool 3 is small. Therefore, as shown in Fig. 7, in step Sd, the threshold calculation means 215 considers the machining conditions for the next machining (second machining) of the workpiece using the tool 3 after the first machining, acquired from the CAM device 6, and determines the allowable chipping amount W, and calculates a position inside the before-machining shape 301 by the allowable chipping amount W as the allowable outer shape of the blade (hereinafter referred to as the chipping limit line 300) as shown in Fig. 10. That is, the chipping limit line 300 is obtained by shrinking the position of each part of the before-machining shape 301 by the allowable chipping amount W inward in the normal direction of each part. The allowable chipping amount W can be set to 0.05 mm when the machining conditions for the second machining are rough machining, and a value smaller than 0.05 mm, for example, 0.02 mm, when the machining conditions for the second machining are finish machining.

[0038] 7, in step Se, the edge chipping detection means 214 uses the laser device 4 to trace the shape of the cutting edge 33 of the tool 3 after the first machining (the after-machined shape 302). The after-machined shape 302 is traced in the same manner as the before-machined shape 301. The traced after-machined shape 302 is shown by a solid line in FIG.

[0039] Next, in step Sf, the chipping detection means 214 determines whether or not the traced after-machining shape 302 has a portion located inside the chipping limit line 300. That is, the chipping detection means 214 checks whether the difference between the before-machining shape 301 and the after-machining shape 302 is equal to or greater than a predetermined threshold. If at least a portion of the after-machining shape 302 is located inside the chipping limit line 300, the chipping detection means 214 determines that there is a chip in the tool 3, and proceeds to step Sg to generate an alarm.

[0040] Here, FIG. 9(a) is a schematic diagram for explaining a method for tracing the shape of the cutting edge 33 of the tool 3 where a part of the cutting edge 33 is chipped. FIG. 9(b) shows an example of a light blocking detection signal detected when only one of the laser beams 43 irradiated four times during one rotation of the tool 3 is not blocked by the cutting edge of the tool 3. Here, as shown in FIG. 9(a), a case is assumed where a cutting edge is chipped in the third cutting edge 3c of the four cutting edges of the tool 3. In this case, when tracing a position (i.e., the position of the cutting edge limit line 300) shifted inward from the radius of the tool 3 by the allowable cutting edge amount W with the laser beam 43 in step Se, the laser beam 43 is blocked by the cutting edges 33 of the first cutting edge 3a, the second cutting edge 3b, and the fourth cutting edge 3d, but the laser beam 43 is not blocked by the third cutting edge 3c. Therefore, when tracing a position shifted from the radius of the tool 3 to the inner periphery by the allowable chipping amount W with the laser light, the wear detection signal is interrupted for a time t3 as shown in Fig. 9(b), and the chipping detection means 214 detects the chipping by detecting the interruption. On the other hand, when tracing the shape of the cutting edge 33 of the tool 3, if none of the after-machining shapes 302 are located inside the chipping limit line 300, the wear detection signal is not interrupted during one rotation of the tool, and it can be determined that there is no chipping in the tool 3, and the process moves to the second machining. In this way, the chipping detection means 214 detects chipping of the tool 3 after machining by detecting that the difference between the before-machining shape 301 and the after-machining shape 302 is equal to or greater than a predetermined threshold value (i.e., the allowable chipping amount W).

[0041] (Functions and Effects of the Embodiments) The machine tool 1 of this embodiment includes chipping detection means 214 that detects chipping of the tool 3 after machining by detecting that the difference between the before-machining shape 301 and the after-machining shape 302 is equal to or greater than a predetermined threshold value (allowable chipping amount W). Therefore, chipping of the tool blade can be detected.

[0042] In addition, when the tip of the tool 3 is on the central axis of the tool 3 (for example, a drill, a ball end mill, etc.), the chipping detection means 214 detects chipping of at least one edge of the tool 3 after machining by detecting that the difference between the pre-machining shape and the post-machining shape obtained by measuring the tip of the tool 3 with the laser device 4 is equal to or greater than a predetermined threshold. In addition, when the tip of the tool 3 is at least located at a position away from the central axis of the tool 3 on the outer periphery side (for example, a flat end mill, a reamer, etc.), the chipping detection means 214 detects chipping of at least one edge of the tool 3 after machining by detecting that the difference between the pre-machining shape and the post-machining shape obtained by measuring the outer periphery end of the tip position of the tool 3 with the laser device 4 is equal to or greater than a predetermined threshold. This allows the tool 3 to be reliably focused during tool shape measurement, thereby improving the accuracy of the shape measurement of the tool 3.

[0043] Furthermore, the machine tool 1 of this embodiment includes a machining condition acquisition means 211 that acquires machining conditions for the next machining of a workpiece using the machined tool 3, and a threshold calculation means 215 that calculates the predetermined threshold (allowable amount of chipping W) based on the machining conditions acquired by the machining condition acquisition means 211. Therefore, by appropriately changing the threshold for detecting chipping of the tool 3 in accordance with the machining conditions, it becomes possible to detect chipping of the tool 3 in accordance with the allowable amount of chipping of the tool 3.

[0044] In addition, the threshold value calculated by the threshold value calculation means 215 is smaller when the machining conditions are conditions for finish machining than when the machining conditions are conditions for rough machining. In other words, since finish machining requires higher machining accuracy than rough machining, it is possible to assist efficient replacement of the tool 3 by setting a relatively large allowable chipping amount W when the next machining is rough machining and a relatively small allowable chipping amount W when the next machining is finish machining.

[0045] Furthermore, the blade chipping detection means 214 measures the shape of each blade of the tool 3 using the measuring device 4, based on the number of blades of the tool 3 and the shape of the tool 3 acquired by the machining condition acquisition means 211 from the CAM device 6. Since the number of blades of the tool 3 and the shape of the tool 3 are information that the machine tool 1 generally acquires from the CAM device 6, by utilizing this information, it becomes unnecessary to separately input the number of teeth of the tool 3 and the shape of the tool 3, making it easier to automate the machining of the workpiece by the machine tool 1.

[0046] As described above, according to this embodiment, it is possible to provide a machine tool 1 capable of detecting chipping of the edge of the tool 3.

[0047] (Additional Note) Although the present invention has been described above based on the embodiment, the invention according to the claims is not limited to the embodiment. It should be noted that not all of the combinations of features described in the embodiment are necessarily essential to the means for solving the problems of the invention.

[0048] Furthermore, the present invention can be implemented in various ways, such as by omitting some components or adding or substituting components, without departing from the spirit of the invention.

[0049] For example, in the above embodiment, the measuring device for measuring the shape of the tool is a laser device, but the present invention is not limited to this, and the shape of the tool may be measured by image processing, for example. Here, although dust particles, coolant mist, etc. generated during machining are present inside the machine tool, laser light is not easily affected by these, and therefore a laser device is preferably used as the measuring device. [Explanation of symbols]

[0050] 1…Machine tool 211…Method for acquiring processing conditions 214...Blade chipping detection means 215...Threshold calculation means 3...Tools 4...Measuring device (laser device)

Claims

1. A tool having a plurality of blades provided on an outer periphery thereof; a measuring device for measuring a shape of the tool; a chipping detection means for detecting chipping of at least one of the blades of the tool after machining by detecting that a difference between a pre-machining shape, which is a shape of the tool before it is used to machine a workpiece, and a post-machining shape, which is a shape of the tool after it is used to machine the workpiece and is measured by the measuring device, is equal to or greater than a predetermined threshold value; a machining condition acquisition means for acquiring machining conditions for the next machining of the workpiece using the tool after the machining; and a threshold calculation means for calculating the threshold based on the processing conditions acquired by the processing condition acquisition means. Machine tools.

2. The tool has a tip located on a central axis of the tool, the edge chipping detection means detects chipping of at least one of the edges of the tool after machining by detecting that a difference between the pre-machining shape and the post-machining shape obtained by measuring the tip of the tool by the measuring device is equal to or greater than a predetermined threshold value. The machine tool according to claim 1.

3. The tool has a tip at least at a position spaced from a central axis of the tool toward an outer periphery, the edge chipping detection means detects chipping of at least one of the edges of the tool after machining by detecting that a difference between the pre-machining shape and the post-machining shape obtained by measuring an outer circumferential end portion at a tip position of the tool by the measuring device is equal to or greater than a predetermined threshold value. The machine tool according to claim 1.

4. The machining conditions acquired by the machining condition acquisition means include conditions regarding rough machining and conditions regarding finish machining which is performed after the rough machining, The threshold value calculated by the threshold value calculation means is a smaller value when the machining conditions are conditions related to the finish machining than when the machining conditions are conditions related to the rough machining. A machine tool according to any one of claims 1 to 3.

5. the machining condition acquisition means acquires the machining conditions, including the number of teeth of the tool, the diameter of the tool, and the length of the tool, from a CAM device that creates a path of the tool when machining a workpiece using the tool; the chipping detection means measures the shape of each of the blades of the tool by the measuring device based on the number of blades of the tool and the shape of the tool acquired by the machining condition acquisition means from the CAM device; A machine tool according to any one of claims 1 to 4.

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