JP5927904B2 - Machine tool dynamic characteristics calculation device - Google Patents

Description

  The present invention relates to a technique for calculating dynamic characteristics of a rotary tool such as an end mill used when cutting.

  When cutting with a rotary tool such as an end mill, acquiring the dynamic characteristics of the rotary tool is important in determining appropriate machining conditions. Patent Document 1 proposes a technique in which an unbalance master is attached to a main shaft, a shake amount of the unbalance master is detected by a shake amount measuring device, and dynamic stiffness of the main shaft is calculated. However, with the technique disclosed in Patent Document 1, it is possible to calculate the dynamic rigidity of the spindle, but it is not possible to acquire the dynamic characteristics of the rotary tool. For this reason, conventionally, an operator generally hits the rotary tool with a hammer, vibrates the rotary tool, measures the resonance frequency of the rotary tool (hammering test), and calculates the dynamic characteristics from this resonance frequency. It was the target.

JP 2010-274375 A (FIG. 1)

  However, in order to calculate the dynamic characteristics by such a method, it is necessary to attach an accelerometer to the rotary tool and then hit the rotary tool with a hammer. there were. In addition, after the operator hits the rotary tool with a hammer, the restored rotary tool may come into contact with the hammer. In this case, a measurement error occurs. there were. In addition, the dynamic characteristics cannot be measured by a hammering test while the main spindle is rotating, and the dynamic characteristics cannot be calculated accurately because the rigidity of the bearing differs when the main spindle is stationary and rotating. There was a problem.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a machine tool dynamic characteristic calculation apparatus that can acquire accurate dynamic characteristics of a rotary tool without taking time and effort.

(Claim 1)
Using a rotary tool having one or more blades in the circumferential direction on the outer peripheral side, the machine tool moves intermittently by moving relative to the workpiece while rotating the rotary tool about its axis. A device for calculating characteristics, wherein when the rotary tool is vibrated by intermittent cutting, a tool displacement amount detecting means for detecting a displacement amount of the rotary tool in a vibrating state, and the rotation and cutting resistance calculating means for calculating the cutting resistance of the tool, the displacement amount of the rotary tool in a state in which the tool displacement amount detecting means is vibrating the detected and the rotation that has been calculated by the cutting resistance calculating means based on the cutting resistance of the tool, it comprises a mass coefficient is a dynamic characteristic of the rotating tool, elastic modulus, and the dynamic characteristic calculating means for calculating at least one of the viscous damping coefficient, a.

(Claim 2)
During trial machining of the workpiece, on the basis of the displacement amount of the rotary tool in the state that vibrations detected by said tool displacement amount detecting means, the dynamic characteristic calculating means, the movement of the rotary tool Calculate the characteristics.

(Claim 3)
The rotary tool displacement amount detection means may be an imaging device.

(Claim 1)
The dynamic characteristic calculation means calculates at least one of a mass coefficient, an elastic coefficient, and a viscous damping coefficient, which are dynamic characteristics of the rotary tool, based on the displacement amount of the rotary tool and the cutting resistance of the rotary tool. Thereby, the dynamic characteristic of the rotary tool during rotation of the spindle to which the rotary tool is attached is calculated. For this reason, it is possible to obtain the dynamic characteristics more accurately than in the case where the dynamic characteristics are calculated while the main shaft is stopped. Further, the tool displacement amount detection means detects the displacement amount of the rotating tool that is vibrated by intermittent cutting, and calculates dynamic characteristics based on the detected displacement amount of the rotating tool. For this reason, it is not necessary to attach an accelerometer to the rotary tool as in the prior art, and since no experience is required in how to strike the hammer, the dynamic characteristics can be acquired without taking time and effort.

(Claim 2)
During the trial machining of the workpiece, the dynamic characteristic calculation unit calculates the dynamic characteristic of the rotary tool based on the displacement amount of the rotating tool in a vibrating state detected by the tool displacement amount detection unit. . As a result, the dynamic characteristics of the rotary tool can be calculated without affecting the quality of the final product.

(Claim 3)
The amount of displacement of the rotary tool during cutting is detected by the imaging device. Thereby, the outer edge of the rotary tool is detected from the image data including the rotary tool imaged by the imaging device, and the displacement of the rotary tool is detected. For this reason, compared with the conventional method of detecting the displacement of the rotary tool by an acceleration sensor or the like, it is not affected by noise such as vibration accompanying rotation of the rotary spindle to which the rotary tool is attached, and more accurately. The displacement of the rotary tool can be detected, and a slight displacement of the rotary tool can also be detected. Moreover, even if it is a small diameter rotary tool which cannot attach an acceleration sensor, a dynamic characteristic can be acquired.

It is a figure which shows the structure of the machine tool in this embodiment. It is a top view showing the positional relationship of a workpiece | work, a rotary tool, and a high-speed camera. It is explanatory drawing which shows the cutting resistance which arises in a rotary tool. It is a figure for demonstrating the generation | occurrence | production mechanism of a process error, Comprising: The cutting resistance which arises in a rotary tool, the actual cutting amount, and the behavior with respect to the elapsed time of the displacement of the rotation center of a rotary tool are shown. The positional relationship between the rotary tool and the workpiece at each time in FIG. 4 is shown. It is a functional block diagram of the machine tool of this embodiment. It is a graph showing the time-dependent change of the displacement Ty of the anti-cutting direction Y of a rotary tool. It is a flowchart which shows the dynamic characteristic calculation process by the dynamic characteristic calculation part of FIG. It is a graph showing the time-dependent change of the change of a rotary tool, a deformation speed, and a cutting speed. It is a flowchart which shows the dynamic characteristic calculation and the process performed by the control part of FIG.

(1. Configuration of the target machine tool)
A configuration of the machine tool 100 to which the dynamic characteristic calculation apparatus of the present embodiment is applied will be described. The machine tool 100 is a machine tool that cuts the workpiece W with a rotary tool. An example of the machine tool 100 will be described with reference to FIG. As shown in FIG. 1, the machine tool 100 captures an image of a bed 1, a rotating spindle 4 that holds a rotating tool 5, a table 6 on which a workpiece W is placed on the bed 1, and a rotating tool 5. A speed camera 9 and a control unit 50 that performs overall control of the machine tool 100 are provided.

  Here, the rotary tool 5 includes one or more blade portions 5a and 5b in the circumferential direction on the outer peripheral side. The rotary tool 5 includes, for example, a ball end mill, a square end mill, and a milling cutter. The rotation main shaft 4 can be moved in the X-axis, Y-axis, and Z-axis directions by an actuator (not shown). The machine tool 100 performs intermittent cutting by moving relative to the workpiece W while rotating the rotary tool 5 about the axis.

  The control unit 50 includes a CPU 50a that executes various programs and a storage unit 50b that stores programs executed by the CPU 50a and various setting values. The program stored in the storage unit 50b and executed by the CPU 50a corresponds to each calculation unit, processing unit, and control unit shown in FIG. The storage unit 50b corresponds to each storage unit shown in FIG. Each calculation unit and processing unit shown in FIG. 6 to be described later may be configured by ASIC (Application Specific Integrated Circuit).

  The high-speed camera 9 has an image sensor such as a CCD or CMOS, and a lens that forms an image on the image sensor, and is disposed on the side of the rotary tool 5. The high-speed camera 9 images the rotary tool 5 continuously from the side (for example, 5000 frames / second). An image including the rotary tool 5 captured by the high-speed camera 9 is output to the control unit 50. In the embodiment shown in FIG. 2, the high-speed camera 9 is arranged in the feed direction X with respect to the rotary tool 5 so that the deformation of the rotary tool 5 in the anti-cutting direction Y can be imaged. The control unit 50 and the high-speed camera 9 correspond to a dynamic characteristic calculation device that calculates the dynamic characteristic of the rotary tool 5. Although not shown, the machine tool 100 includes a coolant nozzle that supplies coolant, a coolant pump, and the like.

(2. Explanation of cutting force and displacement acting on rotating tool during machining)
Below, with reference to FIG. 3, the cutting force and displacement which act on the rotary tool 5 during a process are demonstrated. The rotary tool 5 that is cutting the workpiece W has a cutting resistance Fy in the anti-cutting direction Y and a cutting resistance Fx in the counterfeed direction. That is, the rotation center C on the tip side of the rotary tool 5 is displaced T in the direction of the combined resistance Fxy of the cutting resistances Fx and Fy in each direction (shown in FIG. 2). And the post-processing shape of the workpiece W changes by the displacement Ty of the anti-cutting direction Y by the cutting center F of the rotation center C of the front end side (part of blade part 5a, 5b) of the rotary tool 5 by cutting resistance Fy. Although FIG. 3 shows a square end mill, the same applies to a ball end mill.

  Here, if the cutting resistance Fy generated in the rotary tool 5 is constant, the amount of deflection on the tip side of the rotary tool 5 is constant. However, in the intermittent cutting with the rotary tool 5, the cutting resistance Fy generated in the rotary tool 5 changes sequentially. Therefore, the displacement amount of the rotation center C on the distal end side of the rotary tool 5 mainly changes sequentially in the Y direction. At this time, the displacement amount of the rotation center C on the distal end side of the rotary tool 5 and the cutting resistance Fy are the rotation tool 5. Depends on the dynamic characteristics of The dynamic characteristics of the tool indicate the deformation behavior with respect to the input force. The transfer function (compliance and phase lag) or the mass coefficient M, the viscous damping coefficient C, and the elastic coefficient (spring multiplier) K calculated from the transfer function (compliance and phase lag). And the natural frequency fd, the damping rate ζ, and the like. As shown in FIG. 2, in this embodiment, when viewed from the top, the displacement Ty in the anti-cutting direction Y of the rotary tool 5 is imaged and detected by the high-speed camera 9.

  Next, when performing intermittent cutting of the workpiece W while rotating and feeding the rotary tool 5, the cutting resistance Fy acting on the rotary tool 5 and the displacement amount of the rotation center C on the tip side of the rotary tool 5. The behavior of Ty with respect to the elapsed time t will be described with reference to FIGS. Here, the cutting resistance Fy in the anti-cutting direction (Y direction) and the displacement amount Ty of the rotation center C on the tip side will be described.

  The behavior of the cutting resistance Fy with respect to the elapsed time t will be described with reference to the solid line in FIG. 4 and FIGS. As shown by the solid line in FIG. 4, the cutting resistance Fy changes from near zero to a large value at time t1, and again changes to near zero at time t2. FIGS. 5A and 5B correspond to times t1 and t2 in FIG. 4, respectively. As shown in FIG. 5A, time t1 is the moment when one of the blades 5a starts to contact the workpiece W. That is, time t1 is the moment when cutting is started by one of the blade portions 5a. On the other hand, as shown in FIG. 5B, the time t2 is the moment when the cutting of the workpiece W by the one blade portion 5a is finished. Thus, one blade part 5a is cutting between t1 and t2.

  Thereafter, as shown in FIG. 4, the cutting resistance Fy is zero between t2 and t4. During this time, as shown in FIG. 5C corresponding to time t3, both the blade portions 5a and 5b are not in contact with the workpiece W. That is, the rotary tool 5 is idling.

  After that, as shown in FIG. 4, the cutting resistance Fy changes again to a large value at time t4 and again changes to near zero at time t5. At time t4 in FIG. 4, the other blade portion 5b starts to contact the workpiece W as shown in the corresponding FIG. 5 (d). That is, cutting is started by the other blade portion 5b. Further, at time t5 in FIG. 4, as shown in the corresponding FIG. 5 (e), the cutting with the other blade portion 5b is finished. Thus, the other blade part 5b is cutting between t4 and t5.

  Here, it can be seen from the current cutting region in FIG. 5 that the actual cutting amount h (instantaneous cutting amount) differs at the instants t1 to t2 and t4 to t5. That is, the actual cutting amount h increases at a stroke from the start of cutting and gradually decreases after reaching the peak. In more detail, it changes before and after the boundary between the part not cut last time and the part cut last time. Then, as shown in the portion of the cutting force Fy of FIG. 4 that is abruptly increased, the cutting resistance Fy during the cutting process has a substantially triangular shape, and changes according to the actual cutting depth h. I understand that

  In addition, when the rotary tool 5 starts cutting at times t1 and t4, in other words, it collides with the workpiece W at times t1 and t4. That is, at the moment when the rotary tool 5 starts cutting from the idling state, an intermittent cutting resistance Fy is generated in the rotary tool 5 due to a collision with the workpiece W.

  That is, the rotation center C on the distal end side of the rotary tool 5 generates an acceleration in at least the anti-cutting direction (Y direction) due to fluctuations in the cutting resistance Fy during cutting. Furthermore, due to the intermittent cutting, the rotational center C on the tip side of the rotary tool 5 is at least in the anti-cutting direction (Y) due to the cutting resistance Fy (force such as impact force) during cutting. Direction).

  Therefore, the displacement amount Ty of the rotation center C on the tip side of the rotary tool 5 vibrates according to the eigenvalue of the rotary tool 5 as shown by the broken line in FIG. In particular, the cutting resistance Fy, which fluctuates during the cutting process, becomes a vibration source and causes vibration, and is damped while the rotary tool 5 is idling. Then, the displacement amount Ty is increased again by the cutting resistance Fy, and the process is repeated.

(3. Functional configuration of machine tools)
Next, details of the functional configuration of the machine tool 100 will be described with reference to FIGS. The machine tool 100 is configured as shown in the functional block diagram of FIG. The functional configuration of the machine tool 100 shown in FIG. 6 will be described below.

  The cutting resistance detection sensor 71 detects the cutting resistance Fy in the anti-cutting direction Y that acts on the rotary tool 5 during cutting, and outputs a detection signal to the cutting resistance calculation unit 32. For example, as the cutting resistance detection sensor 71, a load sensor, a displacement sensor, a power consumption detector of a drive motor for a feed shaft, a supply current sensor, or the like can be applied. That is, the cutting force Fy itself can be directly detected by a load sensor, or the cutting force Fy can be indirectly detected by a displacement sensor or the like.

  The cutting resistance calculation unit 32 calculates the cutting resistance Fy in the anti-cutting direction Y that acts on the rotary tool 5 during cutting based on the detection signal output from the cutting resistance detection sensor 71. Note that the cutting resistance calculation unit 32 may calculate the cutting resistance Fy in the anti-cutting direction Y acting on the rotary tool 5 during cutting from the information and processing conditions of the rotary tool 5 by simulation.

  The tool displacement amount calculation unit 35 calculates the displacement Ty in the anti-cutting direction Y of the rotation center C of the rotary tool 5 captured by the high speed camera 9. Specifically, the tool displacement amount calculation unit 35 determines the boundary (edge) between the image of the rotary tool 5 and the image of the other portion (for example, the background) from the image data including the captured rotary tool 5 based on the brightness difference or the like. ) To detect the outer edge of the rotary tool 5. Then, the tool displacement amount calculation unit 35 detects how many pixels the outer edge of the rotary tool 5 has moved in the anti-cutting direction Y at a predetermined position in the axial direction of the rotary tool 5 for each frame. The displacement Ty of the rotation center C in the anti-cutting direction Y is calculated. In this way, the displacement amount (shown in FIG. 7) of the rotary tool 5 in the state of being vibrated and vibrated by intermittent cutting is continuously calculated. Note that the outer edge of the rotary tool 5 is detected by forming the blade parts 5a and 5b of the rotary tool 5 so that the displacement Ty in the anti-cutting direction Y of the rotary tool 5 is not affected by the presence or absence of the blade parts 5a and 5b. Not on the outer peripheral surface of the base.

  As shown in FIG. 7, the tool displacement amount storage unit 36 continuously stores temporal changes in the displacement Ty in the anti-cutting direction Y of the rotary tool 5 that is vibrated and vibrated by intermittent cutting. Is done. As shown in FIG. 7, the displacement Ty in the anti-cutting direction Y of the rotary tool 5 is the maximum displacement after any one of the blade part 5a and the blade part 5b of the rotary tool 15 first comes into contact with the workpiece W. It becomes Ty1, and then vibrates at a constant period T while gradually damped.

  The dynamic characteristic calculation unit 37 is based on the continuous displacement Ty in the anti-cutting direction Y of the rotary tool 5 stored in the tool displacement amount storage unit 36 and the cutting resistance Fy calculated by the cutting resistance calculation unit 32. The dynamic characteristics of the rotary tool 5 are calculated. FIG. 8 is a flowchart illustrating calculation of dynamic characteristics (natural frequency fd, angular natural frequency ωd, damping factor ζ, mass coefficient M, viscous damping coefficient C, and elastic coefficient K) of the rotary tool 5 by the dynamic characteristic calculation unit 37. Will be described below.

  First, the dynamic characteristic calculation unit 37 calculates the angular natural frequency ωd of the displacement Ty based on the continuous displacement Ty in the anti-cutting direction Y of the rotary tool 5 stored in the tool displacement amount storage unit 36 (S21). ). Specifically, first, as shown in the equation (1), the dynamic characteristic calculation unit 37 detects the interval between the times t1 and t2 of the maximum displacements Ty1 and Ty2 of the rotary tool 15, and the period T [ s] (shown in FIG. 7) is detected.

(Equation 1)
T [s] = t2-t1 (1)

  Next, the dynamic characteristic calculation unit 37 calculates the natural frequency fd [Hz] of the displacement Ty from the reciprocal of the period T of the displacement Ty, as shown in Expression (2).

(Equation 2)
fd = 1 / T (2)
fd: natural frequency

  Next, the dynamic characteristic calculation unit 37 calculates the angular natural frequency ωd [rad / s] of the displacement Ty as shown in Expression (3) (S21).

(Equation 3)
ωd = 2πfd (3)
ωd: angular natural frequency

  Next, based on the continuous displacement Ty in the anti-cutting direction Y of the rotary tool 5 stored in the tool displacement amount storage unit 36, the dynamic characteristic calculation unit 37, as shown in Expression (4), the rotary tool 15 The vibration damping rate ζ of the rotary tool 5 is calculated from the maximum displacements Ty1, Ty2 (shown in FIG. 7) (S22).

  Next, the dynamic characteristic calculation unit 37 makes contact with the workpiece W with one blade portion 5a based on the continuous displacement Ty in the anti-cutting direction Y of the rotary tool 5 stored in the tool displacement amount storage unit 36. The integrated value Ak (shown in FIG. 9) of the displacement Ty from the time t0 (shown in FIG. 9) at the start time to the time t1 (shown in FIG. 9) at the moment when cutting of the workpiece W by the one blade portion 5a is completed. Is calculated (S23).

  Next, the dynamic characteristic calculation unit 37 time-differentiates the continuous displacement Ty in the anti-cutting direction Y of the rotary tool 5 stored in the tool displacement amount storage unit 36, so that the deformation speed Vy ( 9 is calculated, and the deformation speed Vy is integrated over time from the time t0 to the time t1, and an integrated value Ac (shown in FIG. 9) of the deformation speed Vy of the rotary tool 5 is calculated (S24).

  Next, the dynamic characteristic calculation unit 37 integrates the cutting resistance Fy calculated by the cutting resistance calculation unit 32 from the time t0 to the time t1 described above, and an integrated value At (see FIG. 9) of the cutting resistance Fy of the rotary tool 5. ) Is calculated (S25).

Next, the dynamic characteristic calculation unit 37 calculates the mass coefficient M (S26). Below, the mass coefficient M calculation method is demonstrated.
The force F acting on the rotary tool 5 during cutting of the workpiece W includes the cutting resistance Fy in the anti-cutting direction Y acting on the rotary tool 5, the force Fk due to the elasticity of the rotary tool 5, and the viscosity of the rotary tool 5. Since it is the resultant force Fc due to damping, it is expressed by the following equation (5).

(Equation 5)
F = Fy + Fk + Fc (5)

F: Force in the anti-cutting direction Y acting on the rotary tool 5
Fy: Cutting resistance in the anti-cutting direction Y acting on the rotary tool 5
Fk: force due to elasticity of the rotary tool 5
Fc: Force due to viscous damping of the rotary tool 5

  Here, Fk is expressed by the following formula (6).

(Equation 6)
Fk = −KTy (6)

Fk: force due to elasticity of the rotary tool 5
K: elastic coefficient of the rotary tool 5
Ty: Displacement Ty in the anti-cutting direction Y of the rotary tool 5

  Fc is represented by the following formula (7).

(Equation 7)
Fc = −CVy (7)

Fc: Force due to viscous damping of the rotary tool 5
C: Viscous damping coefficient of rotating tool 5
Vy: Deformation speed Vy in the anti-cutting direction Y of the rotary tool 5

  Next, when the mass coefficient M of the rotary tool 5 is assumed and the acceleration of the rotary tool 5 is a, the formula (9) is derived from the above formula (5) and the following formula (8).

(Equation 8)
F = Ma (8)

F: Force in the anti-cutting direction Y acting on the rotary tool 5
M: Mass coefficient of the rotary tool 5
a: Acceleration of the rotary tool 5

(Equation 9)
a = (Fy + Fk + Fc) / M (9)

  Here, if the deformation speed of the rotary tool 5 at the time t0 is V0 (shown in FIG. 9) and the deformation speed of the rotary tool 5 at the time t1 is V1 (shown in FIG. 9), the speed of the rotary tool 5 during that time Since the change amount ΔVy = (V1−V0) is a value obtained by integrating the acceleration a of the rotary tool 5 from time t0 to time t1, the above expressions (6) and (7) are substituted into the above expression (9). Then, when time integration is performed from the time t0 to the time t1, the following expression (10) is derived.

  Substituting the integrated value At of the cutting force Fy calculated in S25, the integrated value Ak of the displacement Ty calculated in S23, and the integrated value Ac of the deformation speed Vy calculated in S24 into the above formula (10), 11) is derived.

(Equation 11)
MΔVy = At−KAk−CAc (11)

  Here, if the damping rate ζ is sufficiently small, the angular natural frequency ωd is expressed by the following equation (12) from the equation of motion of the damping vibration.

(Equation 12)
ωd = √ (K / M) (12)
ωd: angular natural frequency
K: elastic modulus
C: Viscous damping coefficient

  When the above equation (12) is deformed, the elastic coefficient K is expressed by the following equation (13).

(Equation 13)
K = ωd ² M (13)

  On the other hand, the damping rate ζ is expressed by the following equation (14) from the equation of motion of the damped vibration.

(Equation 14)
ζ = C / 2√ (K · M) (14)
ζ: Decay rate
K: elastic modulus
C: Viscous damping coefficient

  When the above equation (14) is transformed and the above equation (12) is substituted, the viscous damping coefficient C is expressed by the following equation (15).

(Equation 15)
C = 2ζ√ (K · M) = 2ζωdM (15)

  Next, when the above equation (13) and the above equation (15) are substituted into the above equation (11), the following equation (16) is derived.

(Equation 16)
At = MΔVy + Mωd ² Ak + 2MζωdAc (16)

And if the above equation (16) is transformed, the following equation (17) is derived.
(Equation 17)
M = At / (ΔVy + ωd ² Ak + 2ζωdAc) (17)

  Next, when the angular natural frequency ωd calculated in S21 and the damping factor ζ calculated in S22 are substituted into the above equation (17), the mass coefficient M of the rotary tool 5 is calculated.

  Next, the dynamic characteristic calculator 37 substitutes the elastic coefficient K of the rotary tool 5 by substituting the angular natural frequency ωd calculated in S21 and the mass coefficient M calculated in S26 into the above equation (13). Calculate (S27).

  Finally, the dynamic characteristic calculation unit 37 substitutes the angular natural frequency ωd calculated in S21, the damping factor ζ calculated in S22, and the mass coefficient M calculated in S26 into the above equation (15), thereby rotating the rotary tool. 5 is calculated (S28).

  The tool dynamic characteristic storage unit 38 includes a natural frequency fd, an angular natural frequency ωd, a damping factor ζ, a mass coefficient M, a viscous damping coefficient C, an elastic coefficient (spring multiplier) calculated by the dynamic characteristic calculating unit 37. ) The dynamic characteristics of the rotary tool 5 made of K are stored.

  The machining condition determination processing unit 39 determines the machining conditions for cutting based on the dynamic characteristics stored in the tool dynamic characteristic storage unit 38. For example, the machining condition determination processing unit 39, based on the natural frequency fd (resonance frequency) of the rotary tool 5, avoids the natural frequency fd of the rotary tool 5, so that the rotational speed S (rotational spindle 4) of the rotary tool 5 is avoided. The rotation speed). Note that the machining condition determination processing unit 39 can determine the machining conditions for the cutting process, change the NC data itself, and can correct the machining conditions for the cutting process during the cutting process.

  The machine control unit 41 controls each drive unit 61 based on the NC data and the machining conditions determined by the machining condition determination processing unit 39. The drive unit 61 includes a motor that rotates the rotation main shaft 4 and an actuator that moves the rotation main shaft 4 in the X-axis, Y-axis, and Z-axis directions.

(4. Description of dynamic characteristics calculation and processing)
Next, referring to the flowcharts of FIGS. 6 and 10, calculation of dynamic characteristics executed by each calculation unit of the control unit 50, the machining condition determination processing unit 39, and the machine control unit 41 shown in FIGS. 1 and 6 is performed. Processing will be described. First, the machine control unit 41 performs a trial machining by outputting a control signal to the drive unit 61 (S101). This trial processing includes processing of a portion that does not affect the quality of the product, rough processing before finishing processing, or cutting with a test piece. Next, the tool displacement amount calculation unit 35 calculates the displacement Ty in the anti-cutting direction Y of the rotary tool 5 based on the imaging data including the rotary tool 15 imaged by the high-speed camera 9 by the above-described processing. The displacement Ty of the rotating tool 5 that is vibrated and vibrated during the trial machining is detected (S102).

  Next, the cutting resistance calculation unit 32 calculates the cutting resistance Fy during the trial machining by the above-described processing (S103). Next, the dynamic characteristic calculation unit 37 is based on the displacement Ty in the anti-cutting direction Y of the rotary tool 5 during the trial machining detected in S102 and the cutting resistance Fy during the trial machining calculated in S103 by the above-described processing. Thus, the dynamic characteristics of the rotary tool 5 including the natural frequency fd, the angular natural frequency ωd, the damping factor ζ, the mass coefficient M, the viscous damping coefficient C, and the elastic coefficient K of the rotary tool 5 are calculated (S103).

  Next, the machining condition determination processing unit 39 determines a machining condition based on the dynamic characteristic calculated in S103 (S105). Next, the machine control unit 41 outputs the control signal to the drive unit 61 based on the NC data and the processing conditions determined in S105, thereby executing the main processing (S106) and completing the product. . Thus, in S101, by cutting the workpiece W at a location that does not affect the quality of the final product, in S102, the displacement amount Ty of the rotary tool 5 being trial-worked is detected. The dynamic characteristics are calculated, and in S105, the processing conditions are determined based on the calculated dynamic characteristics. In S106, the main processing is performed with the processing conditions optimized, so that the quality of the final product is not affected. Cutting can be performed with higher accuracy.

  According to the above-described dynamic characteristic calculation apparatus, the following effects can be obtained. The dynamic characteristic calculation unit 37 (dynamic characteristic calculation unit) illustrated in FIG. 6 is calculated by the displacement amount Ty in the anti-cutting direction Y of the rotary tool 5 during cutting calculated by the tool displacement amount calculation unit 35 and the cutting resistance calculation unit 32. Based on the cutting resistance Fy of the rotating tool 5 in the anti-cutting direction Y, the dynamic characteristic of the rotating tool 5 is calculated. As a result, the dynamic characteristics of the rotary tool 5 while the rotary spindle 4 is rotating are calculated. For this reason, it is possible to accurately calculate and acquire the dynamic characteristic as compared with the case where the dynamic characteristic is calculated in a state where the rotation main shaft 4 is stopped. The high-speed camera 9 (tool displacement amount detection means) detects the displacement amount Ty in the anti-cutting direction Y of the rotary tool 5 vibrated by intermittent cutting, and the detected displacement of the rotary tool 5 is detected. Based on the quantity Ty, the dynamic characteristic is calculated. For this reason, it is not necessary to attach an accelerometer to the rotary tool 5 as in the prior art, and since no experience is required in how to strike the hammer, the dynamic characteristics can be acquired without taking time and effort.

  Further, during the trial machining of the workpiece W, based on the displacement amount of the rotating tool 5 in the vibrating state detected by the high-speed camera 9 (tool displacement amount detection means), the dynamic characteristic calculation unit 37 (dynamic (Characteristic calculating means) calculates the dynamic characteristics of the rotary tool 5. Thereby, the dynamic characteristics of the rotary tool 5 can be calculated without affecting the quality of the final product.

  In this embodiment, the amount of displacement of the rotary tool 5 during cutting is detected by the high-speed camera 9 (imaging device). Then, the outer edge of the rotary tool 5 is detected from the image data including the rotary tool 5 imaged by the high-speed camera 9, and the displacement Ty in the anti-cutting direction Y of the rotary tool 5 is detected. For this reason, compared with the conventional method of detecting the displacement of the rotary tool 5 by an acceleration sensor or the like, the rotary tool 5 is not affected by noise such as vibration accompanying the rotation of the rotary spindle 4 and more accurately. The displacement in the anti-cutting direction Y can be detected, and a slight displacement of the rotary tool 5 can also be detected. Moreover, even if it is the small diameter rotary tool 5 which cannot attach an acceleration sensor, the dynamic characteristic of the rotary tool 5 is acquirable.

  In the embodiment described above, the high-speed camera 9 is used as the tool displacement amount detection means for detecting the displacement amount Ty in the anti-cutting direction Y of the rotary tool 5 during cutting the workpiece W. However, the tool displacement amount detecting means includes a laser light emitting element and a laser light receiving element, and the laser light emitting element irradiates the rotating tool 5 being cut with laser, and is reflected by the rotating tool 5 and received by the laser light receiving element. Thus, a laser displacement sensor that detects the displacement amount Ty in the anti-cutting direction Y of the rotary tool 5 during cutting may be used. Alternatively, as the tool displacement amount detection means, a spindle internal displacement sensor provided in the rotation main shaft 4 for detecting the displacement amount of the rotation main shaft 4 and the anti-cutting of the rotary tool 5 being cut from the displacement amount of the rotation main shaft 4. There may be a spindle internal displacement sensor system including a tool displacement amount calculation unit for calculating the displacement amount Ty in the direction Y.

  In addition, when there are a plurality of resonance points of the rotary tool 5, only the integral multiple of the rotation period of the rotary tool 5 is cut out from the displacement Ty in the anti-cutting direction Y of the rotary tool 5, and the diffusion Fourier expansion (DFT) is performed. It is preferable to calculate the dynamic characteristics of the rotary tool 5.

  5: Rotary tool, 5a, 5b: Blade part, 9 ... High-speed camera (imaging device, tool displacement amount detection means), 32: Cutting resistance calculation part (cutting resistance calculation means), 37: Dynamic characteristic calculation part (dynamic characteristic) Calculation means), 50: control unit, 100 ... machine tool, W: workpiece

Claims (3)

Using a rotary tool having one or more blades in the circumferential direction on the outer peripheral side, the machine tool moves intermittently by moving relative to the workpiece while rotating the rotary tool about its axis. A device for calculating characteristics,
A tool displacement amount detecting means for detecting a displacement amount of the rotating tool in a vibrating state when the rotating tool is vibrated by intermittent cutting;
Cutting force calculating means for calculating cutting resistance of the rotary tool;
The displacement amount of the rotary tool in a state in which the tool displacement amount detecting means is vibrating the detected and, based on the cutting force of the rotary tool calculated by the cutting resistance calculating means, movement of the rotary tool Dynamic characteristic calculating means for calculating at least one of a characteristic mass coefficient, elastic coefficient, and viscous damping coefficient ;
A machine tool dynamic characteristic calculation apparatus comprising: In claim 1,
During trial machining of the workpiece, on the basis of the displacement amount of the rotary tool in the state that vibrations detected by said tool displacement amount detecting means, the dynamic characteristic calculating means, the movement of the rotary tool Machine tool dynamic characteristic calculation device for calculating characteristics. In claim 1 or claim 2,
The tool displacement amount detection means is a dynamic characteristic calculation device of a machine tool which is an imaging device.

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