Grinding burn depth estimation device

Abstract

To provide a grinding burn depth estimation device which can estimate a grinding burn depth of a workpiece with high accuracy.SOLUTION: A grinding burn depth estimation device 1 includes: a grinding condition input part 50 to which grinding condition information on grinding a workpiece is input; a temperature history calculation part 51 which calculates a temperature history of a part to be worked on the basis of the grinding condition information; a burn index calculation part 52 which calculates a burn index corresponding to a heat input energy amount acting on transformation of the part to be worked from an integral value of temperature change in a period with a temperature equal to or higher than a tempering temperature of the part to be worked on the basis of the temperature history; a correspondence storing part 32 which stores a correspondence between the burn index and a burn depth generated in the part to be worked; and a burn depth estimation part 53 which estimates a depth of a grinding burn generated in the part to be worked, on the basis of the burn index calculated by the burn index calculation part 52, and the correspondence.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a grinding burn depth estimation device. [Background technology]

[0002] Conventionally, when grinding a workpiece, the temperature of the workpiece's processing location tends to become high, which can cause grinding burns on the workpiece's surface depending on the processing conditions. Grinding burns are undesirable because they can cause a decrease in the mechanical strength of the workpiece. As a method for detecting such grinding burns, Patent Document 1 discloses a simulation method that calculates total grinding heat energy from the relative speed of the grinding wheel with respect to the workpiece at the grinding point and the grinding resistance, calculates the distribution rate of the heat energy received by the workpiece in the total grinding heat energy, and calculates the grinding burn depth of the workpiece based on the total grinding heat energy and the distribution rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-83048 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration disclosed in Patent Document 1, there is a difference between the estimated burn depth obtained by simulation and the actually measured burn depth, resulting in a decrease in estimation accuracy. This is presumably because the conventional simulation does not fully consider the contact state between the grinding wheel and the workpiece, resulting in a low calculation accuracy of the thermal energy received by the workpiece. Therefore, there is room for improvement in order to estimate the burn depth with higher accuracy.

[0005] The present invention provides a grinding burn depth estimation device that can estimate the grinding burn depth of a workpiece with high accuracy. [Means for solving the problem]

[0006] One aspect of the present invention is A grinding burn depth estimation device that estimates the grinding burn depth of a processed portion of a workpiece that is machined into a final target shape by grinding the surface of the workpiece with a tool, a grinding condition input unit into which grinding condition information relating to grinding of the workpiece is input; a temperature history calculation unit that calculates a temperature history of the workpiece based on the grinding condition information; a burnt index calculation unit that calculates a burnt index corresponding to the amount of heat input energy acting on the transformation of the processed portion from an integral value of temperature change during a period in which the temperature is equal to or higher than the tempering temperature of the processed portion based on the temperature history; a correspondence relationship storage unit that stores a correspondence relationship between the burn indicator and the burn depth generated in the processed portion; The grinding burn depth estimation device includes a burn depth estimation unit that estimates the depth of grinding burn that occurs in the workpiece based on the burn index calculated by the burn index calculation unit and the correspondence relationship. [Effects of the Invention]

[0007] According to the above aspect, a burn index corresponding to the amount of heat input energy acting on the transformation of the workpiece is calculated from the integrated value of temperature change over a period in which the temperature of the workpiece is equal to or higher than the tempering temperature based on the temperature history. Because grinding burn occurs when the workpiece is transformed by heat input energy equal to or higher than the tempering temperature of the workpiece, the burn index is an index that shows a strong correlation with the occurrence of grinding burn. Then, by estimating the depth of grinding burn occurring on the workpiece based on the correspondence between the burn index and the burn depth occurring on the workpiece, the depth of grinding burn occurring on the workpiece can be estimated with higher accuracy.

[0008] As described above, according to the above aspect, it is possible to provide a grinding burn depth estimation device that can estimate the grinding burn depth of a workpiece with high accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a conceptual diagram showing the configuration of a grinding system including a grinding burn depth estimation device according to a first embodiment. [Figure 2] FIG. 2 is a functional block diagram showing the configuration of a grinding burn depth estimation device according to the first embodiment. [Figure 3] FIG. 2 is a functional block diagram showing the configuration of an eddy current sensor and a burn depth calculation unit in the first embodiment. [Figure 4] FIG. 2 is a functional block diagram showing the configuration of an eddy current sensor and a burning boundary power calculation unit in the first embodiment. [Figure 5] FIG. 3 is a diagram showing an output signal of an eddy current sensor in the first embodiment. [Figure 6] FIG. 1A is a diagram showing the relationship between time and the output signal of an eddy current sensor that serves as the first inflection point determination criterion in embodiment 1; and FIG. 1B is a diagram showing the output signal of an eddy current sensor that serves as the first inflection point determination criterion in the complex plane. [Figure 7] 1A is a diagram showing an output signal of an eddy current sensor, FIG. 1B is a diagram showing an actual cutting depth, and FIG. 1C is a diagram showing tool rotational power, which is power consumption of a drive unit of a tool spindle, in the first embodiment. [Figure 8] 3 is an enlarged cross-sectional view of the periphery of a processed portion in the first embodiment. [Figure 9] 1A is an enlarged cross-sectional view of the peripheral portion showing the cooling liquid in a nucleate boiling state, and FIG. 1B is an enlarged cross-sectional view of the peripheral portion showing the cooling liquid in a film boiling state in the first embodiment. [Figure 10] 4 is a conceptual diagram showing an example of a temperature history calculated by a temperature history calculation unit in the first embodiment. FIG. [Figure 11] 4 is a conceptual diagram showing an example of a burn index calculated by a burn index calculation unit in the first embodiment. FIG. [Figure 12] 4 is a conceptual diagram showing an example of a correspondence relationship between a burn index and a burn depth stored in a correspondence relationship storage unit in the first embodiment. FIG. [Figure 13] FIG. 2 is a flowchart of a grinding process in the first embodiment. [Figure 14] FIG. 4 is a flowchart of a grinding burn state estimation process according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) The grinding burn depth estimation device 1 of the first embodiment evaluates the grinding burn state of the workpiece W that is ground by a processing device. Each component will be described in detail below.

[0011] 1.Configuration of processing equipment In the first embodiment, a cylindrical grinding machine 2 shown in Fig. 1 is provided as a processing device. The cylindrical grinding machine 2 rotates a workpiece W about a center line C, rotates a grinding wheel 16 as a tool that is a rotating body, and moves the grinding wheel 16 relatively close to the workpiece W in a direction intersecting the axis of the workpiece W, thereby grinding the outer or inner peripheral surface of the workpiece W. The cylindrical grinding machine 2 can be a table traverse type grinding machine, a wheelhead traverse type grinding machine, or the like.

[0012] In this embodiment, as shown in Fig. 1, the workpiece W is, for example, a member formed in a shaft shape, and the outer circumferential surface of the workpiece W is the part to be machined. However, the shape of the workpiece W is not limited to a shaft shape, and it can be any shape, such as a cylindrical shape having an inner circumferential surface. When the workpiece W is cylindrical, the inner circumferential surface of the workpiece W can be the part to be machined.

[0013] In this embodiment, the workpiece W is generally rod-shaped and is supported at both ends by workpiece support members. However, the workpiece W shown in Fig. 1 is merely an example, and the cylindrical grinding machine 2 can grind workpieces having various shapes.

[0014] The processing unit 3 includes a grinding burn depth estimation device 1 and a control device 3a that controls the cylindrical grinding machine 2. As will be described later, the grinding burn depth estimation device 1 evaluates the state of grinding burn caused by grinding on the workpiece W, and adjusts the processing conditions for the workpiece W based on the evaluation results. The control device 3a controls the cylindrical grinding machine 2, thereby controlling the grinding process.

[0015] The grinding burn depth estimation device 1 can function as a simulation device independent of the cylindrical grinding machine 2 and the control device 3a, or as a simulation device that operates in conjunction with the cylindrical grinding machine 2 and the control device 3a. In the former case, the grinding burn depth estimation device 1 can, for example, determine optimal processing conditions without actually grinding the workpiece W. In the latter case, the grinding burn depth estimation device 1 can, for example, determine the presence or absence of grinding burns, adjust processing conditions, and operate to affect various controls by processing in parallel with the grinding of the workpiece W by the cylindrical grinding machine 2. The grinding burn depth estimation device 1 can also be incorporated into the cylindrical grinding machine 2 and the control device 3a.

[0016] 2. Configuration of Cylindrical Grinding Machine 2 and Control Device 3a The configuration of the cylindrical grinding machine 2 will be described with reference to Fig. 1. In this embodiment 1, a wheelhead traverse type cylindrical grinding machine is used as an example of the cylindrical grinding machine 2. However, a table traverse type can also be used for the cylindrical grinding machine 2. The cylindrical grinding machine 2 mainly includes a bed 11, a headstock 12, a tailstock 13, a traverse base 14, a wheelhead 15, a grinding wheel 16, a grinding wheel dressing device 18, a coolant device 19, and an eddy current sensor 20.

[0017] The bed 11 is fixed on a mounting surface. The headstock 12 is provided on the upper surface of the bed 11, on the near side in the X-axis direction (the lower side in FIG. 1) and on one end side in the Z-axis direction (the left side in FIG. 1). The headstock 12 supports the workpiece W rotatably around the Z-axis with the center line C of the workpiece W as the center. The workpiece W is rotated by driving a motor 12a provided on the headstock 12. The tailstock 13 is provided on the upper surface of the bed 11, in a position facing the headstock 12 in the Z-axis direction, i.e., on the near side in the X-axis direction (the lower side in FIG. 1) and on the other end side in the Z-axis direction (the right side in FIG. 1). In other words, the headstock 12 and the tailstock 13 rotatably support both ends of the workpiece W.

[0018] The traverse base 14 is provided on the upper surface of the bed 11 so as to be movable in the Z-axis direction. The traverse base 14 is moved by driving a motor 14a provided on the bed 11. The grinding wheel head 15 is provided on the upper surface of the traverse base 14 so as to be movable in the X-axis direction. The grinding wheel head 15 is moved by driving a motor 15a provided on the traverse base 14. The grinding wheel 16 is rotatably supported on the grinding wheel head 15. The grinding wheel 16 is rotated by driving a motor 16a provided on the grinding wheel head 15. The grinding wheel 16 is composed of a plurality of abrasive grains fixed together with a bond material.

[0019] The sizing device 17 functions as a detector that measures the dimension (diameter) of the workpiece W. However, the detector is not limited to the sizing device 17, and may be a contact sensor having a single probe or a non-contact sensor such as a laser displacement meter. The sizing device 17 is provided so as to be movable in the Z-axis direction in synchronization with the traverse base 14 via a mechanism not shown.

[0020] The eddy current sensor 20 has its sensor head attached to the main body of the sizing device 17 and is disposed so as to face the processed portion of the workpiece W. In the first embodiment, the sensor head of the eddy current sensor 20 is positioned on the opposite side of the workpiece W from the grinding wheel 16. In FIG. 1, the reference numeral 20 indicates the position of the sensor head, and the sensor main body is not shown.

[0021] The eddy current sensor 20 induces an eddy current inside the workpiece W using an excitation current and outputs an AC signal corresponding to the magnetic field generated by the eddy current. The eddy current sensor 20 is used when creating a correspondence relationship between the burn index and the burn depth and when acquiring the burn boundary power Q'w, as will be described later, but does not need to be used in the subsequent burn depth estimation process. Alternatively, another configuration capable of detecting the burn depth may be used instead of the eddy current sensor 20.

[0022] The eddy current sensor 20 may be configured to be able to change the phase of the output signal. In this embodiment, as shown in Fig. 4, the eddy current sensor 20 has a coil serving as an oscillator 21, and by supplying an excitation current to the coil, an output signal is applied to a probe 22 provided at the tip of the sensor head of the eddy current sensor 20, thereby applying a magnetic field to the workpiece W and inducing an eddy current inside the workpiece W. The eddy current sensor 20 then amplifies the change in impedance acquired via the probe 22 in an amplifier 23 and inputs it to a detector 24, extracts only the frequency component of the oscillator 21, and processes the signal in a signal processor 25.

[0023] The detection unit 24 detects the signal by synchronous detection. As shown in Fig. 5, the input signal v(t) to the detection unit 24 is a signal obtained by amplifying the output of the probe 22 in the amplifier unit 23, and v(t) is defined by the following equation (1). Here, t is time, A is amplitude, f is the frequency of the oscillator 21 inside the eddy current sensor 20, and θ is the phase difference with respect to the oscillator 21 inside the eddy current sensor 20.

[0024]

number

[0025] Then, in detection unit 24, v(t) that has passed through amplifier unit 23 is multiplied by a sine wave sin2πft, which has the same frequency as frequency f of oscillator 21. This is called x(t). Similarly, the result of multiplying by cos2πft is called y(t). x(t) and y(t) can be expressed as the following equations (2) and (3).

[0026]

number

[0027]

number

[0028] Next, pass x(t) and y(t) through a low-pass filter with a sufficiently low cut-off frequency fc. Generally, the relationship fc << f holds. The first terms in equations (2) and (3) are alternating currents because they contain t, while the second terms are direct currents because they do not contain t. Therefore, after passing through the low-pass filter, equations (2) and (3) become the real-axis signal X and the imaginary-axis signal Y shown in the following equations (4) and (5), respectively.

[0029]

Number

[0030]

Number

[0031] And, as shown in the following equations (6) and (7) from equations (4) and (5), A and θ of v(t) can be obtained.

[0032]

Number

[0033]

Number

[0034] In the signal processing unit 25, operations such as gain and phase are performed on the real-axis signal X and the imaginary-axis signal Y of the detection unit 24. Therefore, the output signal of the eddy current sensor 20 is output through the signal processing unit 25 from the detection unit 24, and the frequency characteristics of the eddy current sensor 20 are the product of the frequency characteristics of the detection unit 24 and the signal processing unit 25. Generally, the frequency characteristics of the signal processing unit 25 are lower than those of the detection unit 24. In the output signal output from the signal processing unit 25, X represents the real-axis signal and Y represents the imaginary-axis signal. The real-axis signal X indicates the value of the real axis in the output signal, and the imaginary-axis signal Y indicates the value of the imaginary axis in the output signal.

[0035] The eddy current sensor 20 is configured to supply multiple excitation currents with different frequencies to the coil. In this first embodiment, the frequency of the excitation current can be set by a frequency setting unit 310, which will be described later. Since the penetration depth of the eddy current varies depending on the frequency of the excitation current, the frequency of the excitation current can be set according to the target penetration depth of the eddy current. The target penetration depth of the eddy current is set to match the surface layer where grinding burn may occur, and can be, for example, 1 to 100 μm from the processed surface, preferably 1 to 50 μm, and more preferably 10 to 30 μm. If the penetration depth is shallow, the sensitivity of the eddy current sensor becomes too high, resulting in a lower signal-to-noise ratio and reduced detection accuracy. On the other hand, if the penetration depth is deep, the detection level of the magnetic property change characteristic decreases in areas shallow from the processed surface, resulting in reduced detection accuracy.

[0036] The frequency of the excitation current according to the penetration depth can be set in the frequency band of 20 kHz to 200 MHz, preferably 100 kHz to 200 MHz, and more preferably 250 to 2500 kHz. In this embodiment, the frequency of the excitation current is set to 250 kHz so that the penetration depth of the eddy current is 30 μm.

[0037] The grinding wheel dressing device 18 shown in Figure 1 dresses the shape of the grinding wheel 16. The grinding wheel dressing device 18 is a device that performs truing on the grinding wheel 16. The grinding wheel dressing device 18 may be a device that dresses the grinding wheel 16 in addition to or instead of truing. Furthermore, the grinding wheel dressing device 18 also has a function of measuring the dimensions (diameter) of the grinding wheel 16.

[0038] Truing here refers to a reshaping operation, such as shaping the grinding wheel 16 to fit the shape of the workpiece W when the grinding wheel 16 has worn down due to grinding, or removing runout of the grinding wheel 16 due to one-sided wear. Dressing refers to a dressing (sharpening) operation, such as adjusting the protrusion amount of the abrasive grains and creating cutting edges for the abrasive grains. Dressing is an operation to correct dullness, clogging, missing grains, etc., and is usually performed after truing.

[0039] The coolant device 19 supplies coolant from a coolant nozzle to the point where the workpiece W is ground by the grinding wheel 16. The coolant device 19 cools the collected coolant to a predetermined temperature and supplies it again to the grinding point. The coolant device 19 is capable of adjusting the flow rate and supply timing of the coolant. In FIG. 1, reference numeral 19 indicates the position of the coolant nozzle. Although not shown, a temperature sensor may be provided as a detector to acquire the temperature of the collected coolant.

[0040] The control device 3a grinds the workpiece W by controlling the driving of the grinding wheel 16, coolant device 19, etc. in the cylindrical grinding machine 2 based on an NC program generated based on operation command data such as the shape of the workpiece W, processing conditions, the shape of the grinding wheel 16, and coolant flow rate or supply timing information. In particular, the control device 3a grinds the workpiece W until it reaches the finished shape (target shape). Furthermore, the control device 3a performs correction (truing and dressing) of the grinding wheel 16 by controlling the grinding wheel correction device 18, etc., at the timing to correct the grinding wheel 16.

[0041] 3. Configuration of grinding burn depth estimation device 1 2, the grinding burn depth estimation device 1 includes a burn depth calculation unit 30, a correspondence relationship creation unit 31, a correspondence relationship storage unit 32, a burn boundary power calculation unit 40, a grinding condition input unit 50, a temperature history calculation unit 51, a burn index calculation unit 52, a burn depth estimation unit 53, a burn evaluation unit 54, and a processing condition adjustment unit 56, which are configured as a storage device or a computing device.The grinding burn depth estimation device 1 also includes a burn state display unit 55 configured as a predetermined display device.

[0042] 3-1. Burn depth calculation unit 30 The burn depth calculation unit 30 calculates the burn depth in order to create a correspondence relationship between the burn index S (described later) and the burn depth. The burn depth calculation unit 30 includes a signal acquisition unit 300, a first characteristic information acquisition unit 301, a time storage unit 302, an inflection point determination criterion storage unit 303, an inflection point calculation unit 304, an inflection point time extraction unit 305, a rotation count acquisition unit 306, a rotation angle acquisition unit 307, an average data minimum value time acquisition unit 308, and a first calculation unit 309.

[0043] The signal acquiring unit 300 acquires the output signal output from the eddy current sensor 20. When expressed on a complex plane in Cartesian coordinate format, the output signal has a value on the imaginary axis Y and a value on the real axis X, and can be expressed on the complex plane as shown in FIG.

[0044] The first characteristic information acquisition unit 301 acquires first characteristic information. The first characteristic information is information obtained by linking at least one of the imaginary axis value and the real axis value of the output signal acquired by the signal acquisition unit 300 when the output signal is represented on a complex plane in a Cartesian coordinate system with time information indicating the time when the workpiece W is ground. In this embodiment, both the imaginary axis value and the real axis value of the output signal represented on the complex plane shown in Fig. 6(b) are linked to the elapsed time from the start of grinding, which is measured by a time memory unit 302 described later.

[0045] The time memory unit 302 measures the elapsed time from the start time T0 of the grinding process. In this embodiment, the grinding process S1 of the workpiece W includes a rough grinding step S11, a fine grinding step S12, a fine grinding step S13, and a spark-out step S14, as shown in Fig. 13. Each step will be described later.

[0046] The inflection point judgment criterion storage unit 303 shown in Fig. 3 pre-stores inflection point judgment criteria for determining whether the output signal represented on the complex plane has reached an inflection point (described later) for each frequency of the excitation current. In this embodiment, the inflection point judgment criterion can be created based on the correspondence between the frequency of the excitation current, first characteristic information acquired by applying an excitation current having that frequency to a workpiece for creating an inflection point judgment criterion during machining, and the grinding burn state of the workpiece for creating an inflection point judgment criterion. The workpiece for creating an inflection point judgment criterion has the same shape and material as the workpiece W to be evaluated shown in Fig. 1.

[0047] For example, the correspondence relationship between the first feature information and the grinding burn state when the frequency of the excitation current set by the frequency setting unit 310 is 250 kHz is shown in Figures 6(a) and 6(b). When the frequency of the excitation current is different, the correspondence relationship between the first feature information and the grinding burn state also changes accordingly. For example, although not shown, the correspondence relationship shown on the complex plane for 1000 kHz is expressed as a shape rotated -90 degrees from the case of 250 kHz.

[0048] Next, the trajectory of the output signal on the complex plane will be described with reference to Fig. 6(b). On the complex plane shown in Fig. 6(b), the output signal output from the eddy current sensor 20 is plotted at the position indicated by reference symbol A1 at the start of grinding. Thereafter, in the rough grinding step S11, when grinding burn occurs on the workpiece W, the magnetic characteristics change accordingly, and as a result, the output signal's real axis value on the complex plane decreases and its imaginary axis value increases slightly over time. After that, the real axis value decreases and the imaginary axis value decreases, and then the real axis value increases and the imaginary axis value decreases, until the position indicated by reference symbol A2 is reached, at which point the rough grinding step S11 ends.

[0049] Thereafter, when the fine grinding process S12 begins, as grinding burns (machining-affected layer, softened layer) that had occurred on the workpiece W are gradually removed, the output signal in the complex plane decreases in real axis value and gradually increases in imaginary axis value. That is, near the start point B1 of the fine grinding process S12, the vector direction in the imaginary axis direction in the output signal locus in the complex plane is pointing upward. Thereafter, as grinding progresses further and the position indicated by reference symbol B2 is reached, the real axis value increases but the imaginary axis value continues to gradually increase. Then, at the position indicated by reference symbol B3, the real axis value continues to increase but the imaginary axis value decreases. That is, at reference symbol B3, the output signal reaches its maximum value in the fine grinding process S12, and thereafter the vector direction in the imaginary axis direction in the output signal locus in the complex plane changes to a downward direction. Thereafter, the real axis value increases while the imaginary axis value decreases until the position indicated by reference symbol B4 is reached and the fine grinding process S12 ends.

[0050] The inflection point calculation unit 304 calculates an inflection point based on an inflection point determination criterion. An inflection point indicates a point where the direction of the vector of the output signal on the complex plane changes in the imaginary axis direction or the real axis direction. Therefore, in the case where the frequency of the excitation current shown in FIG. 6(b) is 250 kHz, the inflection point is point B3 where the direction of the vector of the output signal in the imaginary axis direction changes from upward to downward.

[0051] Since the locus of the output signal in the complex plane changes depending on the frequency of the excitation current, the inflection point determination criterion for the inflection point also changes. In this embodiment, the inflection point determination criterion storage unit 303 stores the locus of the output signal in the complex plane for each excitation current frequency for the workpiece used to create the inflection point determination criterion (master), and based on this, the inflection point determination criterion is stored for each excitation current frequency. For example, as described above, the inflection point determination criterion for when the excitation current frequency is 250 kHz is that the point at which the direction of the vector of the output signal locus stored in the inflection point determination criterion storage unit 303 shown in Figure 6(b) changes from upward to downward in the imaginary axis direction in the fine grinding process S12 is determined to be the inflection point.

[0052] Furthermore, the inflection point judgment criterion storage unit 303 also stores the correspondence between the first characteristic information and the grinding burn state for the workpieces used to create the inflection point judgment criterion. When the frequency of the excitation current is 250 kHz as shown in FIG. 6(b), in the fine grinding process S12, the region from the fine grinding process start point B1 to the inflection point B3 indicates a state in which a softened layer that will cause grinding burn is present on the workpiece W. The region from the inflection point B3 to the vicinity of the processing end point B4 indicates a state in which no softened layer is present on the workpiece W, but a retained austenite-reduced layer that had formed deeper on the softened layer remains on the workpiece W. The retained austenite-reduced layer is not included in the grinding burn because its mechanical properties are closer to those of the base material than those of the softened layer.

[0053] The inflection point time extraction unit 305 extracts, from the first feature information, the time at which the inflection point B3 occurs in the trajectory of the output signal represented on the complex plane as the inflection point time. In the example shown in Figure 6(a), the time Ta of the inflection point B3 is extracted as the inflection point time.

[0054] The rotation count acquisition unit 306 acquires the number of rotations of the workpiece W from the start time of acquiring the number of rotations to the inflection point time Ta. The start time of acquiring the number of rotations can be, for example, the end of the rough grinding process, i.e., the start time T1 of the fine grinding process. Note that the number of rotations at the start time of acquiring the number of rotations is set to 0.

[0055] If the headstock 12 has a rotation angle acquisition unit 307 that acquires the rotation angle of the rotation axis of the workpiece W, the number of rotations of the workpiece W can be acquired based on the rotation angle of the rotation axis of the workpiece W acquired by the rotation angle acquisition unit 307.

[0056] During grinding of the workpiece W by the cylindrical grinder 2, the phase during one rotation of the workpiece W that is most affected by heat, i.e., the phase resulting in the maximum burn depth, corresponds to the time when an extreme value appears in the output signal of the eddy current sensor 20. This extreme value is either a maximum or minimum value, and which of these values ​​is determined by the workpiece temperature due to grinding heat. The period during which this extreme value appears corresponds to the rotation period of the workpiece W. The method for obtaining the extreme value is to obtain the maximum or minimum value for each rotation period of the workpiece starting from the end of the rough grinding process, i.e., the start of the fine grinding process, T1. Here, when measuring eddy currents in steel materials with different tempering temperatures, it has been found that the eddy current value reverses at steel materials tempered at approximately 250°C. At temperatures above 250°C, softened tissue is formed by tempering, and the higher the temperature, the more positive the output signal value of the eddy current sensor 20. On the other hand, at temperatures below 250°C, tempering does not occur and softened tissue is not formed, so the higher the temperature, the more negative the output signal value of the eddy current sensor 20. The temperature at which the eddy current value is reversed varies depending on the material of the workpiece W.

[0057] 6(a), this boundary is estimated to be the time Tb of the average data minimum value, which corresponds to the downward convex portion of the average data of the waveform of the real axis signal of the eddy current sensor 20. Since the temperature of the workpiece due to grinding is higher towards the surface, the phase with the deepest thermal influence is the time of the maximum value before this downward convex portion (the time Tb of the average data minimum value), and the time of the minimum value after the downward convex portion.

[0058] The average data minimum value time Tb is acquired by the average data minimum value time acquisition unit 308 shown in Fig. 3. A known method can be used to calculate the average data. In this embodiment, the average data of the output signal of the eddy current sensor acquired by the signal acquisition unit 300 is represented by a solid line in Fig. 6(a), and the time at which the average data becomes a minimum value is represented as time Tb.

[0059] Based on this, in this embodiment, the rotation count acquisition unit 306 acquires the number of rotations of the workpiece W based on the extreme value data of the output signal of the eddy current sensor 20. More specifically, the rotation count is acquired based on the maximum value data of the output signal of the eddy current sensor in a first interval F1 from the rotation count acquisition start time T1 to the average data minimum value time Tb, and the rotation count is acquired based on the minimum value data of the output signal of the eddy current sensor 20 in a second interval F2 from the average data minimum value time Tb to the inflection point time Ta.

[0060] 6(a), the maximum value data in the first interval F1 are the peaks of the mountain-shaped peaks that repeatedly appear in the real axis signal, and the number of occurrences is four. The minimum value data in the second interval F2 are the bottoms of the valley-shaped peaks that repeatedly appear in the real axis signal, and the number of occurrences is five. Since the inflection point time Ta is located between the last minimum value data Va and the next minimum value data Vb in the second interval F2, the interpolated data obtained by linearly interpolating between the two can be set to 0.5. Therefore, the rotation count acquisition unit 306 can acquire the number of rotations as 9.5, which is the sum of the number of peaks (4) that appear in the first interval F1, the number of bottoms (5) that appear in the second interval F2, and the interpolated data (0.5).

[0061] The first calculation unit 309 calculates the grinding burn depth of the workpiece based on the number of rotations N acquired by the rotation number acquisition unit 306 and the cutting depth q per rotation of the workpiece W. More specifically, the grinding burn depth D can be calculated by the formula D=N·q, which is the product of the number of rotations N acquired by the rotation number acquisition unit 306 and the cutting depth q per rotation of the workpiece W. The cutting depth q per rotation of the workpiece W can be a value preset as a grinding condition. The burn depth calculation unit 30 shown in FIG. 2 then outputs the grinding burn depth D calculated by the first calculation unit 309 as the calculation result.

[0062] 3-2. Burning boundary power calculation unit 40 The burn boundary power calculation unit 40 shown in Fig. 2 calculates the burn boundary power Q'w, which is the maximum value of power required to rotate the grinding wheel 16 within a range in which grinding burn does not occur in the machined portion of the workpiece W. As shown in Fig. 4, the boundary power calculation unit 40 includes a signal acquisition unit 300, a sudden change time extraction unit 400, a dimension information acquisition unit 401, an actual cutting depth calculation unit 402, a tool rotation power acquisition unit 403, a machined width acquisition unit 404, and a second calculation unit 405. Note that the same components as those already described are assigned the same reference numerals, and their description will be omitted.

[0063] To calculate the burn boundary power Q'w, the sudden change time extraction unit 400 first extracts a time p at which the output signal acquired by the signal acquisition unit 300 suddenly changes during the transient response period Sa in the rough grinding process S11, during which the actual cutting-in amount changes from the initial value A0 (a state in which the grinding wheel 16 and the workpiece W are not in contact) to the commanded cutting-in amount instructed by the control device 3a based on the grinding conditions, as shown in Figure 7(b). During the transient response period Sa, the grinding efficiency Z' also changes so as to continuously increase from the initial value corresponding to the initial value A0 to the target value corresponding to the commanded cutting-in amount.

[0064] The sudden change time extraction unit 400 extracts the sudden change time p as follows. First, a sudden change region Sc, where the output signal suddenly changes from the initial value P0 during the transient response period Sa, is extracted. The sudden change time p is included in the sudden change region Sc. For example, the sudden change region Sc can include the point at which the value of the output signal during the transient response period Sa reaches a predetermined reference value Ps. In the first embodiment, as shown in FIG. 7(a), the reference value Ps corresponds to half the maximum change amount Pm, which is the maximum amount of change in the output signal from the initial value P0 during the transient response period Sa, and the time at which the reference value Ps is reached is defined as the sudden change time p. Alternatively, the sudden change time p can be defined as the time at which the value of the imaginary axis of the output signal reaches a local maximum during the transient response period Sa.

[0065] The dimension information acquisition unit 401 acquires dimension information of the workpiece W. In this embodiment, as described above, the dimension information of the workpiece W can be obtained by detecting the dimension of the workpiece W during processing by the sizing device 17. Note that instead of using the sizing device 17, the dimension information of the workpiece W may be indirectly calculated and acquired based on the coordinate position of the X-axis, which is the cutting axis of the workpiece W, output from the control device 3a.

[0066] The actual cutting-in amount calculation unit 402 acquires the cutting-in amount per rotation of the workpiece W based on the amount of change in the dimensional information of the workpiece W acquired by the dimensional information acquisition unit 401. In this embodiment, as shown in Fig. 7(b), the actual cutting-in amount is calculated, the actual cutting-in amount at the sudden change time p is t(p), and the actual cutting-in amount at the steady state Sb in the rough grinding process S11 (a state in which the actual cutting-in amount after the transient response period Sa has become equivalent to the command cutting-in amount) is ts.

[0067] The tool rotational power acquisition unit 403 acquires the rotational power of the grinding spindle that holds the grinding wheel 16 as a tool from the drive device 16a of the control device 3a. In this embodiment, as shown in Fig. 7(c), the rotational power Q of the grinding spindle in the steady state Sb in the rough grinding process S11 is acquired.

[0068] The machined width acquisition unit 404 acquires the width of the machined portion of the workpiece W. In this embodiment, the width b of the machined portion is the length in a direction parallel to the axial direction of the workpiece W at the contact surface between the grinding wheel 16 and the workpiece W.

[0069] The second calculation unit 405 calculates the burn boundary power Q'w according to the following equation (8) using the actual cutting depth t(p) at the sudden change time p, the actual cutting depth ts at steady state Sb, the rotational power Q of the grinding wheel spindle at steady state Sb, and the width b of the workpiece.

[0070]

number

[0071] In the sudden change region Sc, when the coolant supplied to the workpiece Wa shown in FIG. 8 enters a film boiling state due to heat generated by grinding the workpiece W with the grinding wheel 16, grinding burn occurs in the LM of the workpiece Wa. Grinding burn occurs in a short period of time, and the output signal (eddy current voltage) of the eddy current sensor 20, which changes in response to the damaged layer that occurs on the workpiece W due to grinding burn, also changes within a short period of time (particularly at the sudden change time p), resulting in a steep change (sudden change) in the output signal. Therefore, the rotational power of the grinding wheel 16 that exhibits the actual cutting depth t(p) at the sudden change time p corresponds to the burn boundary power Q'w.

[0072] 3-3. Grinding condition input section 50 2 receives input of grinding condition information for performing grinding processing on the cylindrical grinding machine 2. The grinding condition information includes tool rotational power, specification information of the tool (grinding wheel 16), specification information of the workpiece W, specification information of the processing conditions, specification information of the cooling conditions of the processed portion of the workpiece W, burn boundary power, and a heat distribution factor which is the ratio of the heat amount distributed to the processed portion in the total grinding thermal energy.

[0073] The tool rotational power is the rotational power Q of the grinding wheel spindle during steady state Sb in the rough grinding process S11, which is acquired from the drive device 16a of the control device 3a by the tool rotational power acquisition unit 403. The tool rotational power can be acquired using a wattmeter, but it may also be calculated from tangential resistance or motor current.

[0074] The specification information of the tool (grinding wheel 16) includes the dimensions of the grinding wheel 16 and physical properties such as thermal diffusivity. The specification information of the workpiece W includes the dimensions of the workpiece W and physical properties such as thermal diffusivity. The specification information of the processing conditions includes the grinding efficiency Z', grinding power, rotational speed of the tool and workpiece, and feed rate of the tool. The burn boundary power can be the burn boundary power Q'w calculated by the burn boundary power calculation unit 40. The thermal diffusivity can be derived from thermal conductivity / (specific heat x density).

[0075] The specification information of the cooling conditions for the processed portion of the workpiece W includes the convection heat transfer coefficient of the coolant. The convection heat transfer coefficient can be set based on the depth of the softened layer formed by actually processing the workpiece W under conditions that result in the formation of a white layer that exhibits grinding burn.

[0076] The heat distribution ratio, which is the ratio of the heat energy distributed to the workpiece in the total grinding heat energy, will be explained below. First, the total grinding heat energy is the sum of the grinding heat energy on the shear surface, the grinding heat energy on the rake face, and the grinding heat energy on the flank face, calculated based on the relative speed of the grinding wheel 16 to the workpiece W at the grinding point and the grinding resistance. The heat distribution ratio, which is the ratio of the heat energy distributed to the workpiece in the total grinding heat energy, can be calculated based on Jaeger's theory of moving heat sources (J.C. Jaeger: Proceedings of Royal Society of New South Wales, vol. 76, (1942) 203).

[0077] 3-4. Temperature history calculation unit 51 The temperature history calculation unit 51 calculates the temperature history of the processed portion of the workpiece W. The target position for the temperature history can be a position on a virtual line Wp that will become the outermost surface after processing in the processed portion Wa during grinding processing shown in FIG. 8. It can also be a position at a predetermined depth from the position on the virtual line Wp that will become the outermost surface. In this embodiment, the temperature history calculation unit 51 calculates the temperature history of the position on the virtual line Wp.

[0078] As shown in Figure 8, in an example of up-cut grinding, coolant CL flows between the grinding wheel 16 and the workpiece Wa of the workpiece W along the rotational direction V of the grinding wheel 16, cooling the workpiece Wa. However, when the temperature of the workpiece Wa rises due to heat generated in the workpiece Wa during grinding of the workpiece W and reaches the boiling point of the coolant CL, the coolant CL first boils near the surface of the workpiece Wa, forming bubbles Bo, as shown in Figure 9(a). In the initial boiling stage, each bubble Bo is generally independent, and the liquid coolant CL is in contact with the surface of the workpiece Wa. This state is called nucleate boiling of the coolant CL. During nucleate boiling, the coolant CL maintains its cooling performance for the workpiece Wa, preventing overheating and preventing grinding burns from occurring on the workpiece Wa.

[0079] On the other hand, if the temperature of the workpiece Wa further rises and exceeds the boiling point of the coolant CL, the boiling of the coolant CL near the surface of the workpiece Wa becomes more active, generating numerous bubbles B, which then fuse together. As the bubbles B fuse together, a bubble layer Bm is formed, as shown in Figure 9(b). Because the surface of the workpiece Wa is covered by this bubble layer Bm, the liquid coolant CL no longer comes into contact with the surface of the workpiece Wa. This state is called film boiling of the coolant CL. In film boiling, the cooling performance of the coolant CL for the workpiece Wa is significantly reduced, causing the workpiece Wa to overheat, resulting in grinding burns. Therefore, the timing at which the coolant CL transitions from nucleate boiling to film boiling is the timing at which grinding burns occur on the workpiece Wa.

[0080] 8, in an example of up-cut grinding, of the contact arc LC between the grinding wheel 16 and the workpiece Wa, indicated by the symbol Lc, the region LW, indicated by the symbol Lw, which is close to the inflow position of the coolant CL, is a nucleate boiling region, and the region LM, indicated by the symbol Lm, which is far from the inflow position of the coolant CL, is a film boiling region. As the workpiece W is fed in the direction of arrow v during grinding, the workpiece Wa is removed as shown by the dashed line, and the film boiling region relatively advances in the opposite direction to the feed direction of the workpiece W. Note that even in the case of down-cut grinding, in which the rotation direction V of the grinding wheel 16 is reversed, the region close to the inflow position of the coolant CL is a nucleate boiling region, and the region far from the inflow position of the coolant CL is a film boiling region.

[0081] Therefore, the point on Wp, which is the target position of the temperature history in the temperature history calculation unit 51, passes through the film boiling region LM from the start of grinding and then passes through the nucleate boiling region LW in the rough grinding step S11. As a result, the temperature history acquired by the temperature history calculation unit 51 rises as it passes through the film boiling region LM, and suddenly drops when it reaches the nucleate boiling region LW, as shown in Fig. 10, for example. In this embodiment, the temperature history calculation unit 51 acquires the temperature history at least when the coolant CL is in a film boiling state.

[0082] 3-5. Burn index calculation unit 52 The tempering index calculation unit 52 shown in FIG. 2 calculates the tempering temperature θ of the workpiece Wa based on the temperature history calculated by the temperature history calculation unit 51. temp From the integral value of the temperature change during the period above, a burn index S corresponding to the amount of heat input energy acting on the transformation of the workpiece Wa is calculated. temp The integral value of the temperature change during the period above is calculated as the burnt index S. The integral value as the burnt index S can be calculated using the following formula (9) based on the tempering parameter (Hollomon Jaffe parameter) and the activation energy of the tempering process.

[0083]

number

[0084] 3-5. Correspondence Creation Unit 31 and Correspondence Storage Unit 32 The correspondence relationship creating unit 31 shown in FIG. 2 creates a correspondence relationship between the burn index S and the burn depth. The created correspondence relationship is stored in the correspondence relationship storage unit 32. The correspondence relationship creating unit 31 calculates the burn depth using the burn depth calculation unit 30 for grinding burn that occurs when a workpiece for creating the correspondence relationship is ground, and calculates the burn index S using the burn index calculation unit 52, thereby creating a correspondence relationship between the two. As shown in FIG. 12, the correspondence relationship can be expressed as an approximate function of a plurality of burn depths and a plurality of corresponding burn indexes S. In this embodiment, the correspondence relationship is expressed as an approximate formula Af that indicates a linear relationship, as shown in FIG. 12.

[0085] 3-6. Burn depth estimation section 53 2 estimates the depth of grinding burn occurring in the processed portion Wa of the workpiece W to be estimated at the end of the rough grinding step S11, based on the burn index S calculated for the workpiece W to be estimated by the burn index calculation unit 52 and the correspondence stored in the correspondence storage unit 32. In this embodiment, the burn depth estimation unit 53 calculates the burn index Sp using the burn index calculation unit 52, and then calculates the burn depth hp corresponding to the burn index Sp based on the approximation formula Af, which is the correspondence stored in the correspondence storage unit 32, as shown in FIG. 12, and sets the burn depth hp as the estimation result.

[0086] 3-7. Burn evaluation unit 54 and burn status display unit 55 The burn evaluation unit 54 evaluates whether or not burn remains in the machined portion of the workpiece W at the end of machining, based on the burn depth hp estimated by the burn depth estimation unit 53. If the burn evaluation unit 54 estimates that the burn depth is 0 at the end of the rough grinding step S11, it evaluates that there is no grinding burn at the end of machining. Furthermore, if the burn depth is estimated to be H at the end of the rough grinding step S11 and the depth of the machined portion Wa to be removed in the subsequent fine grinding step S12 (finishing allowance A) is greater than the burn depth H, it evaluates that there is no grinding burn at the end of machining. On the other hand, if the finishing allowance A in the fine grinding step S12 is equal to or less than the burn depth H, it evaluates that there is grinding burn at the end of machining. The evaluation result by the burn evaluation unit 54 can be displayed on the burn state display unit 55.

[0087] 3-8. Machining condition adjustment section 56 The machining condition adjustment unit 56 shown in FIG. 2 adjusts the machining conditions of the cylindrical grinding machine 2 based on the evaluation results of the burn evaluation unit 54. For example, if the evaluation result of the burn evaluation unit 54 indicates that grinding burn will be present at the end of machining, the machining conditions can be adjusted to reduce the burn depth at the end of the rough grinding step S11, thereby preventing grinding burn at the end of machining. On the other hand, if the evaluation result of the burn evaluation unit 54 indicates that grinding burn will not be present at the end of machining, the burn that was present at the end of the rough grinding step S11 has been completely removed in the fine grinding step S12. Therefore, the machining conditions for the rough grinding step S11 can be maintained unchanged, or the machining conditions can be adjusted to further increase the grinding efficiency Z' in the rough grinding step S11 and shorten the machining time. Note that if grinding burn remains at the end of machining even after adjusting the machining conditions, a truing and dressing command may be displayed on the burn status display unit 55.

[0088] 4. Grinding process S1 The grinding process S1 will be described with reference to Fig. 13. As described above, the grinding process S1 includes the rough grinding step S11, the fine grinding step S12, the fine grinding step S13, and the spark-out step S14.

[0089] In the rough grinding step S11, the control device 3a rotates the grinding wheel 16 at a predetermined speed based on operation command data such as the shape of the workpiece W, grinding conditions, the shape of the grinding wheel 16, and coolant flow rate or supply timing information, to grind the workpiece W with a first depth of cut. In the fine grinding step S12, the control device 3a grinds the workpiece W with a second depth of cut that is smaller than the first depth of cut. In the fine grinding step S13, the control device 3a grinds the workpiece W with a third depth of cut that is smaller than the second depth of cut. In the spark-out step S14, the workpiece W is rotated at a preset rotation speed to grind away the portion left unground in the fine grinding step S13, resulting in a perfectly circular cross-sectional shape. The depth of cut in the spark-out step S14 can be set to zero.

[0090] The cutting depth can be adjusted by controlling the cutting position of the grinding wheel 16 with the control device 3a. The first to third cutting depths in each of the steps S11 to S13 are appropriately set within a range that satisfies the above-mentioned relationship, and the actual cutting depth in the spark-out step S14 is substantially zero. The first cutting depth in the rough grinding step S11 is the largest, and the rough grinding step S11 has the highest grinding efficiency among the steps S11 to S14. Therefore, grinding burn occurs substantially only in the rough grinding step S11.

[0091] 5. Grinding burn depth estimation process S2 Next, the grinding burn depth estimation process S2 performed by the grinding burn depth estimation device 1 will be described with reference to the flow chart in Fig. 14. The grinding burn state estimation process S2 is performed in parallel with the grinding process S1. In the grinding burn depth estimation process S2, it is assumed that the correspondence between the burn depth and the burn index S created by the correspondence creation unit 31 as described above is stored in advance in the correspondence storage unit 32. It is also assumed that the burn boundary power Q'w has been calculated in advance by the burn boundary power calculation unit 40 as described above.

[0092] In the grinding burn depth estimation process S2, first, in step S21, the tool rotational power acquisition unit 403 acquires the rotational power Q of the grinding wheel spindle at steady state Sb in the rough grinding process S11 from the drive device 16a of the control device 3a. Next, in step S21, each grinding condition is input to the grinding condition input unit 50 together with the rotational power Q of the grinding wheel spindle.

[0093] Thereafter, in step S23, the temperature history calculation unit 51 calculates the temperature history of the processed portion Wa of the workpiece W. For example, the temperature history shown in Fig. 10 is calculated. Then, in step S24, the burn index calculation unit 52 calculates the burn index S as the integral value of the integral interval in which the temperature is equal to or higher than the tempering temperature θtemp in the temperature history shown in Fig. 11.

[0094] Next, in step S25, the burn depth estimation unit 53 estimates the burn depth in the processed portion Wa of the workpiece W based on the burn index S calculated by the burn index calculation unit 52 and the burn depth-burn index correspondence relationship stored in the correspondence relationship storage unit 32. For example, in the burn depth-burn index correspondence relationship shown in FIG. 12, the burn depth hp is estimated from the burn index Sp calculated by the burn index calculation unit 52.

[0095] Thereafter, in step S26, the burn evaluation unit 54 evaluates whether the burn depth hp is greater than the finishing allowance A. If it is evaluated in step S26 that the burn depth hp is not greater than the finishing allowance A, the process proceeds to No in step S26, and in step S27 it is evaluated that there will be no burn residue at the end of processing. Note that even if the burn depth estimation unit 53 determines that the burn depth is 0, that is, no burn has occurred, it is also evaluated in step S27 that there will be no burn residue at the end of processing. Then, in step S28, the burn status display unit 55 displays that there is no burn residue, and the process ends.

[0096] On the other hand, if it is determined in step S26 that the burn depth hp is greater than the finishing allowance A, the process proceeds to Yes in step S26, and it is determined in step S29 that there is a burn residue at the end of processing. Then, in step S30, the burn state display unit 55 displays that there is a burn residue.

[0097] Thereafter, in step S31, the processing conditions are adjusted by the processing condition adjustment unit 56. For example, the processing conditions can be adjusted by the processing condition adjustment unit 56 to reduce the grinding efficiency Z' so that the depth of grinding burn at the end of the rough grinding step S11 is reduced. After the processing conditions are adjusted by the processing condition adjustment unit 56, the process ends.

[0098] In this embodiment, various grinding conditions are input in step S22. However, during stable operation, only the tool rotational power is input as a grinding condition, and other grinding conditions may be maintained as most recent ones, with other grinding conditions being input only when conditions are changed, such as when changing stages.

[0099] 6. Action and Effects According to the grinding burn depth estimation device 1 of the first embodiment, a burn index S corresponding to the amount of heat input energy acting on the transformation of the workpiece Wa is calculated from the integrated value of the temperature change during the period when the temperature of the workpiece Wa is equal to or higher than the tempering temperature θtemp, based on the temperature history. Because grinding burn occurs when the workpiece Wa is transformed by heat input energy equal to or higher than the tempering temperature θtemp of the workpiece Wa, the burn index S is an index that shows a strong correlation with the occurrence of grinding burn. Then, by estimating the depth of grinding burn occurring in the workpiece Wa based on the correspondence relationship between the burn index S and the burn depth occurring in the workpiece Wa, the depth of grinding burn occurring in the workpiece Wa can be estimated with higher accuracy.

[0100] In this embodiment, the grinding condition information includes specification information of the tool (grinding wheel 16), specification information of the workpiece W, specification information of the processing conditions, specification information of the cooling conditions of the processed portion Wa, burn boundary power Q'w in the processed portion Wa, and heat distribution factor Rw, which is the ratio of the heat distributed to the processed portion Wa to the total grinding thermal energy. As a result, the grinding condition information used to estimate the burn depth sufficiently includes factors involved in the occurrence of grinding burn, thereby improving the accuracy of estimating the burn depth.

[0101] In this embodiment, the temperature history calculation unit 51 calculates the temperature history at the position that will be the outermost surface of the processed part Wa after processing or at a position at a predetermined depth from the outermost surface, thereby improving the accuracy of estimating the burn depth.

[0102] In this embodiment, the temperature history calculation unit 51 acquires the temperature history when the coolant CL supplied during grinding reaches a film boiling state in the workpiece Wa. Since grinding burns can occur when the coolant CL reaches a film boiling state, the burn depth can be estimated by acquiring the temperature history when the film boiling state is reached.

[0103] This embodiment also includes an eddy current sensor 20 that is disposed opposite the machined portion Wa of the workpiece W, induces eddy currents inside the workpiece W using an excitation current, and outputs an AC output signal corresponding to the magnetic field generated by the eddy current. The burn boundary power Q'w is calculated based on the actual cutting depth t(p) at the time when the output of the eddy current sensor 20 suddenly changes, the cutting depth ts during steady rough grinding, the tool rotational power Q during steady rough grinding, and the width b of the machined portion Wa. This allows the burn depth to be estimated with even greater accuracy.

[0104] Furthermore, this embodiment includes a burn evaluation unit 54 that evaluates whether or not grinding burn will remain when machining is completed based on the estimation result of the burn depth estimation unit 53 and a preset finishing allowance A. This makes it possible to evaluate whether or not grinding burn will remain when machining is completed.

[0105] Furthermore, this embodiment includes a processing condition adjustment unit 56 that adjusts the processing conditions for the grinding process based on the evaluation result of the burn evaluation unit 54. This makes it possible to adjust the processing conditions so that no grinding burn remains when processing is completed.

[0106] Furthermore, this embodiment includes a burnt state display unit 55 that displays the evaluation result of the burnt evaluation unit 54. This makes it easier for the user to recognize the evaluation result of the burnt evaluation unit 54.

[0107] As described above, according to the above-described embodiment, it is possible to provide the grinding burn depth estimation device 1 that can estimate the grinding burn depth of a workpiece with high accuracy.

[0108] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention. [Explanation of symbols]

[0109] 1. Grinding burn depth estimation device 2 Cylindrical grinding machines 3 Processing section 3a Control device 16a Drive unit (motor) 17 Sizing device 20 Eddy current sensor 30 Burn depth calculation section 31 Correspondence creation section 32 Correspondence memory unit 40 Boundary power calculation unit 50 Grinding condition input section 51 Temperature history calculation unit 52 Indicator calculation section 53 Burn depth estimation unit 54 Burn Evaluation Section 55 Burn status indicator 56 Machining condition adjustment section

Claims

1. A grinding burn depth estimation device that estimates the grinding burn depth of a processed portion of a workpiece that is machined into a final target shape by grinding the surface of the workpiece with a tool, a grinding condition input unit into which grinding condition information relating to grinding of the workpiece is input; a temperature history calculation unit that calculates a temperature history of the workpiece based on the grinding condition information; a burnt index calculation unit that calculates a burnt index corresponding to the amount of heat input energy acting on the transformation of the processed portion from an integral value of temperature change during a period in which the temperature is equal to or higher than the tempering temperature of the processed portion based on the temperature history; a correspondence relationship storage unit that stores a correspondence relationship between the burn indicator and the burn depth generated in the processed portion; a burn depth estimation unit that estimates the depth of grinding burn that occurs in the workpiece based on the burn index calculated by the burn index calculation unit and the correspondence relationship.

2. 2. The grinding burn depth estimation device according to claim 1, wherein the grinding condition information includes specification information of the tool, specification information of the workpiece, specification information of machining conditions, specification information of cooling conditions of the machined portion, burn threshold power which is the maximum value of power required to rotate the tool within a range in which grinding burn does not occur in the machined portion, and a heat distribution factor which is a ratio of the amount of heat distributed to the machined portion in total grinding thermal energy.

3. 3. The grinding burn depth estimation device according to claim 1, wherein the temperature history calculation unit calculates the temperature history at a position that will be the outermost surface of the processed part after processing or at a position that is a predetermined depth from the outermost surface.

4. 3. The grinding burn depth estimation device according to claim 1, wherein the temperature history calculation unit acquires a temperature history at least when a coolant supplied during grinding reaches a film boiling state in the processed portion.

5. an eddy current sensor disposed opposite to a portion to be machined of the workpiece, which induces an eddy current inside the workpiece by an excitation current, and outputs an AC output signal corresponding to a magnetic field generated by the eddy current; 3. The grinding burn depth estimation device according to claim 2, wherein the burn boundary power is calculated based on an actual cutting depth at a time when the output of the eddy current sensor suddenly changes, a cutting depth during steady rough grinding, a tool rotational power during steady rough grinding, and a width of the workpiece.

6. 3. The grinding burn depth estimation device according to claim 1, further comprising a burn evaluation unit that evaluates whether or not grinding burn remains upon completion of machining based on the estimation result of the burn depth estimation unit and a preset finishing allowance.

7. 7. The grinding burn depth estimation device according to claim 6, further comprising a processing condition adjustment unit that adjusts processing conditions in the grinding process based on the evaluation result of the burn evaluation unit.

8. The grinding burn depth estimating device according to claim 7 , further comprising a burn state display unit that displays the evaluation result of the burn evaluation unit.

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