JP7625807B2 - Machine Tools - Google Patents

Description

The present invention relates to a machine tool.

Patent Document 1 discloses a machine tool that can detect 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 tool breakage. 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.

JP 2000-343310 A

In the method for detecting tool breakage described in Patent Document 1, for example, if there is a chipped edge on the outer periphery of the tool but the length of the tool itself remains unchanged, it is determined that the tool is not broken. In this case, the workpiece (material to be cut) is machined using a tool with a chipped edge, but there is a risk of a decrease in the machining accuracy of the workpiece.

The present invention was made in consideration of the above circumstances, and aims to provide a machine tool that can detect chipping of tool edges.

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

The present invention makes it possible to provide a machine tool that can detect chipping of tool edges.

FIG. 1 is a schematic overall configuration diagram of a machine tool according to an embodiment. FIG. 2 is a flowchart of a process performed by the tool check means in the embodiment. 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. FIG. 4 is a schematic diagram showing a method for measuring the protruding length of a tool from a holder in the embodiment. 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. 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. FIG. 7 is a flowchart showing a process for detecting chipping of a tool edge in the embodiment. FIG. 8A is a schematic diagram for explaining a method for tracing the shape of the cutting edge of a tool, and FIG. 8B is a diagram showing an example of a light blocking detection signal. FIG. 9A is a schematic diagram for explaining a method for tracing the shape of a cutting edge of a tool that has a chipped portion, and FIG. 9B is a diagram showing an example of a light blocking detection signal. FIG. 10 is a diagram showing a pre-machining shape, an edge chipping limit line, and a post-machining shape in the embodiment.

[Embodiment]
The embodiments of the present invention will be described with reference to Figures 1 to 10. Note that the embodiments described below are shown as preferred specific examples for carrying out the present invention, and while some of the embodiments specifically exemplify various technical matters that are technically preferable, the technical scope of the present invention is not limited to these specific embodiments.

(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 "up and down" refer to the vertical direction of the machine tool 1 in use.

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 the tool 3 attached to the spindle 16 according to an NC program. However, the present invention 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 the table 13 and spindle 16, a horizontal machining center, a turning center, etc. can be used as the machine tool 1. 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.

The upper surface of the bed 11 is provided with a guide surface 111 extending in the Y direction perpendicular to the Z direction. The guide surface 111 guides the saddle 12 arranged on the bed 11 in the Y direction. The upper surface of the saddle 12 is provided with a guide surface 121 extending in the X direction perpendicular to both the Y direction and the Z direction. The guide surface 121 guides the table 13 arranged on the saddle 12 in the X direction. The Y direction movement means of the saddle 12 relative to the bed 11 and the X direction movement means of the table 13 relative to the saddle 12 can each 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.

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 on which the column 14 is provided in the Y direction will be referred to as the rear, and the opposite side will be referred to as the front. The column 14 has a portion that stands upright from the upper surface of the bed 11 and a portion that protrudes from the upper end of the portion to 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 Z-direction movement means of the spindle head 15 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. Based on the movement amounts of various movement means output from the encoder, the control device 2 is configured to obtain the position of the reference point 150 of the spindle head 15 (see Figures 3 and 4). The reference point 150 of the spindle head 15 is a coordinate point acquired by the control device 2, and in this embodiment, it is the lower end position of the spindle head 15 in the Z direction, and is the position where the center axis of the spindle 16 exists in the X and Y directions.

The spindle head 15 is provided with a spindle 16 to which tools such as cutting tools, including end mills and drills, are attached. The spindle 16 is configured to removably hold the tool 3 and to be able to rotate the held tool 3. The spindle 16 is also called a spindle or shaft.

As described below, a measuring device 4 is fixed on the table 13 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 is provided with an irradiating unit 41 that irradiates laser light 43 in the X direction and a light receiving unit 42 that receives the laser light 43 irradiated from the irradiating unit 41, at positions facing each other in the X direction. The laser device 4 is configured so that when the laser light 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 the reference point 150 (see Figures 3 and 4) of the spindle head 15 when the skip signal is received.

The control device 2 controls the movement of the spindle head 15 by controlling 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. 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 with a CAM (Computer Aided Manufacturing) function based on the target shape of the workpiece created using, for example, a CAD device 5 with 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.

The control device 2 includes a control unit 21 having a CPU (calculation processing unit) and RAM that serves as a calculation area when the CPU is operating, and a memory unit 22 including a ROM. The memory 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, and the focal position of the laser, etc. The control unit 21 includes a processing condition acquisition means 211, a tool check means 212, a processing means 213, a chipping detection means 214, and a threshold calculation means 215, and realizes various functions by the CPU executing the programs stored in the memory unit 22.

(Processing by the machining condition acquisition unit 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.

(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.

In step S1, when measuring the radius R' of the tool 3, 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 in the vicinity of the laser light 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 light 43 from one side in the Y direction. Then, when the tool 3 blocks the laser light 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 blocks the laser light 43 (i.e., the position away from the laser light 43 by the radius of the tool 3) 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 depending on 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 obtained 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 obtaining the type and shape of the tool 3 from the CAM device 6.

2, the measured radius R' of the tool 3 and the theoretical radius 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 R satisfy R'≦(R+0.005 mm). The 0.005 mm in the inequality R'≦(R+0.005 mm) is the allowable runout of the tool 3, and can be changed as appropriate depending on the type of tool 3 and the dimensional tolerance of the product formed after the workpiece is machined. If the measured radius R' of the tool 3 exceeds R+0.005 mm, the process moves 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 moves to the next step, tool length confirmation.

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

The method of measuring the protruding length L' in step S3 will be described with reference to Figures 3 and 4. First, as shown in Figure 3, the master bar 7, whose Z-direction length A has been measured with high accuracy in advance, 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 light 43 is obtained in advance. Here, for example, when machining multiple workpieces continuously, the use of the machine tool 1 causes the area around the spindle 16 to become hot, while other areas become relatively cold. This can cause thermal deformation, such as warping, in the column 14, which can cause errors in the result of the length C measured by the laser device 4. For this reason, the length C is measured each time the workpiece being machined is changed.

As shown in FIG. 4, when measuring the protruding length L' from the holder 18 of the tool 3 attached to the spindle 16, 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 a tool 3 such as a flat end mill 31 or a 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). Also, when measuring the protruding length L' of a tool 3 such as a drill 32 or a ball end mill, whose tip (lower end) is 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 light 43 when viewed from the Z direction is automatically output by the machining condition acquisition means 211 using information on the type, shape, etc. 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 light 43 is stored in advance in the storage unit 22.

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 the 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 Z direction length C 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 Z-direction protruding length L' of the tool 3 from the holder 18 is obtained by subtracting the known Z-direction length E of the holder 18 from the length D. In this way, the protruding length L' is obtained.

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+3mm). The 3mm in the inequality L<L'≦(L+3mm) is the allowable value of the difference between the actual tool length L' and the theoretical protrusion length L, and can be changed appropriately depending on the type of tool 3, the dimensional tolerance of the product formed after machining the workpiece, etc. If the measured protrusion length L' of the tool 3 is shorter than the theoretical protrusion length L of the tool 3 used when the tool path is calculated by the CAM device 6, there is a risk that the holder 18 will interfere with the workpiece during machining, and if the measured length L' of the tool 3 is greater than the predetermined length (L+3mm), it will cause machining defects. Therefore, if the measured protrusion length L' of the tool 3 and the theoretical protrusion length L do not satisfy L < L' ≦ (L + 3 mm), it is determined in step S4 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, if 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 moves to the next step, tool diameter measurement.

Next, the tool diameter is checked. In step S5, the laser device 4 is used to measure the diameter OD' [mm] of the tool 3 when the tool 3 is stationary (non-rotating).

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 light 43 from one side in the Y direction, and the Y-direction position of the reference point 150 at the time when the tool 3 comes into contact with the laser light 43 is measured. Similarly, the tool 3 is brought closer to the laser light 43 from the other side in the Y direction, and the Y-direction position of the reference point 150 at the time when the tool 3 comes into contact with the laser light 43 is measured. Then, based on the difference between these measured values, the length from one end of the tool 3 to the other end is calculated. This length is calculated multiple times while rotating the tool 3 around its central axis by a predetermined angle at a time to change its posture, and the maximum of the calculated values is the diameter of the tool 3. 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.

Then, it is determined whether 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 satisfy (OD-0.5 mm) < OD' < (OD + 0.5 mm). In other words, 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 for the difference between the actual diameter OD' of the tool 3 and the theoretical diameter value OD, and can be changed as appropriate depending on the type of tool 3, the dimensional tolerance of the product formed after workpiece machining, etc. If 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), an alarm is issued in step S6, as it is possible that a tool other than the intended tool 3 (the tool 3 set when the tool path was created by the CAM device 6) is attached to the spindle 16. On the other hand, if 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 determined that the intended tool 3 is attached to the spindle 16, and the tool check is terminated.

(Processing by 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 rotational speed of the tool 3, and the tool path of the tool 3.

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

In step Sa, the chipping detection means 214 first measures (traces) the shape (pre-machining shape 301) of the cutting edge 33 of the tool 3 before machining (see FIG. 5(a)) 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 the laser light 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 displayed 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.

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 move the tool 3 so that the bottom end position of the tool 3 and the laser light 43 are in 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 of 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 chipping detection means 214 rotates the tool 3 once and detects whether or not each of the laser beams 43 irradiated four times during that 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.

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

Then, detection of the position of each cutting edge 33 of the tool 3 is repeated up to a position that is a predetermined distance above the lower end position of the tool 3. In this embodiment, the detection is repeated up to a position that is 20 mm above 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 relative to the laser light 43, the position of each cutting edge 33 shifts in the rotation direction. Taking this into consideration, 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 reaches the end position on the laser light 43 side in the Y direction, regardless of the position of the cutting edge 33 detected at any position in the Z direction of the tool 3.

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

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 obtained 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 chipping amount W) as shown in FIG. 10 based on the traced pre-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, obtained from the CAM device 6. The machining conditions include conditions related to rough machining and finishing machining performed after rough machining. Rough machining does not require high machining accuracy compared to finishing machining, and chipping of the tool 3 is relatively easy to tolerate, while finishing machining requires high machining accuracy compared to rough machining, and the allowable chipping amount W of the tool 3 is small. Therefore, as shown in FIG. 7, in step Sd, the threshold calculation means 215 determines the allowable chipping amount W in consideration of the machining conditions for the next machining (second machining) of the workpiece using the tool 3 after the first machining, which are acquired from the CAM device 6, and calculates the 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. In other words, 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.

Then, as shown in FIG. 7, in step Se, the 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 post-machining shape 302). The tracing of the post-machining shape 302 is performed in the same manner as tracing the pre-machining shape 301. The traced post-machining shape 302 is shown by a solid line in FIG. 10.

Next, in step Sf, the chipping detection means 214 determines whether the traced post-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 pre-machining shape 301 and the post-machining shape 302 is equal to or greater than a predetermined threshold. If at least a portion of the post-machining shape 302 is located inside the chipping limit line 300, the chipping detection means 214 determines that the tool 3 has a chip, proceeds to step Sg, and generates an alarm.

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 in which a part of the cutting edge has been 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), it is assumed that the cutting edge has been 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 from the radius of the tool 3 by the allowable cutting edge amount W toward the inner periphery 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 inward from the radius of the tool 3 by the allowable chipping amount W with the laser light, the wear detection signal is interrupted for time t3 as shown in FIG. 9B, 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 machined 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 second machining process is started. In this way, the chipping detection means 214 detects chipping in the machined tool 3 by detecting that the difference between the pre-machining shape 301 and the post-machining shape 302 is equal to or greater than a predetermined threshold value (i.e., the allowable chipping amount W).

(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.

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 or a reamer), 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 when measuring the tool shape, thereby improving the accuracy of the shape measurement of the tool 3.

The machine tool 1 of this embodiment also includes a machining condition acquisition means 211 that acquires the machining conditions for the next machining of the workpiece using the machined tool 3, and a threshold calculation means 215 that calculates the predetermined threshold (allowable chipping amount 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 according to the machining conditions, it is possible to detect chipping of the tool 3 according to the allowable amount of chipping of the tool 3.

The threshold calculated by the threshold calculation means 215 is smaller when the machining conditions are for finish machining than when the machining conditions are for rough machining. In other words, because finish machining requires higher machining accuracy than rough machining, if the next machining is rough machining, a relatively large allowable amount of chipping W is set, and if the next machining is finish machining, a relatively small allowable amount of chipping W is set, which makes it possible to assist in efficient replacement of the tool 3.

The chipped edge detection means 214 also measures the shape of each blade of the tool 3 using the measuring device 4 based on the number of teeth 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 teeth of the tool 3 and the shape of the tool 3 are generally information that the machine tool 1 acquires from the CAM device 6, by utilizing this, 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.

As described above, this embodiment makes it possible to provide a machine tool 1 that can detect chipping of the cutting edge of the tool 3.

(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.

Furthermore, the present invention can be modified as appropriate by omitting some components or adding or substituting components without departing from the spirit of the invention.

For example, in the above embodiment, the measuring device for measuring the shape of the tool is a laser device, but this is not limited thereto, and the shape of the tool may be measured, for example, by image processing. Here, while dust particles, coolant mist, etc. are generated during machining within the machine tool, laser light is less susceptible to these effects, so a laser device is preferably used as the measuring device.

1...machine tool 211...machining condition acquisition means 214...edge chipping detection means 215...threshold calculation means 3...tool 4...measuring device (laser device)

Claims (5)

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. 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. 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. 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. 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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