Dressing completion determination method and dressing completion determination device

Abstract

To provide a dressing completion determination device that can conduct dressing completion determination of a grinding wheel at high accuracy, without requiring complicated preparatory work.SOLUTION: An integrated intensity value calculation section 70 calculates an integrated intensity value of an AE signal intensity occurring during dressing scanning, for every dressing scan, and a dressing completion determination section 74 determines completion of dressing processing on the basis of a saturated increase in the integrated intensity value of the AE signal intensity calculated for every dressing scan.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and device for determining the completion of dressing, which can determine the completion of dressing processing in which a grinding wheel is dressed or its shape is modified by a dresser, and in particular to a technology that eliminates the need for preliminary testing when the type of dresser or grinding wheel or the dressing conditions are changed, and that suppresses erroneous determinations of the completion of dressing. [Background technology]

[0002] As a device for automatically determining the completion of dressing work (sharpening, shape correction) for a grinding wheel, a device has been proposed that detects an AE signal (acoustic emission signal: a vibration wave in the ultrasonic range with a frequency of, for example, 100 kHz or more) and determines the completion of dressing based on whether the difference between the AE signal and a master waveform that has been obtained and stored in advance is within a preset threshold. For example, Patent Document 1 discloses a grinding wheel forming state determination device and a grinding wheel forming state determination method.

[0003] According to the grinding wheel forming state determination device and grinding wheel forming state determination method described in Patent Document 1, even when the AE signal changes depending on the cross-sectional diameter of the grinding wheel, it is possible to easily determine the shape correction state of the grinding wheel, and it is possible to simultaneously determine the completion of dressing and detect wear of the dresser. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5219600 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional dressing completion determination device described above, it was necessary to repeatedly perform preliminary tests to obtain the master waveform and threshold value each time the type of dresser or grinding wheel was changed, which made the preparation work complicated.Furthermore, when calculating the difference between the AE signal and the master waveform, highly accurate superposition of the AE signal waveform and the master waveform on the time axis was required, which created the problem of prone to erroneous determination.

[0006] The present invention has been made against the background of the above circumstances, and its purpose is to provide a method and an apparatus for determining the completion of dressing, which can determine the completion of dressing of a grinding wheel with high accuracy without requiring complicated preparation work. [Means for solving the problem]

[0007] The present inventors have conducted extensive research in light of the above circumstances and have found that when a dresser is repeatedly moved across the dressing surface of a grinding wheel in a dressing process, each time a certain depth of cut is provided, the integrated intensity of the AE signal generated during the dressing scan by the dresser increases with each dressing stroke, and that when dressing of the dressing surface is completed, the increase in the integrated intensity of the AE signal during the dressing scan reaches saturation. The present invention was made based on this finding.

[0008] That is, the gist of the first invention is that (a) a dressing scan is performed by sliding a dresser on a dressing surface of a grinding wheel and moving the dresser at a constant feed rate across the dressing surface in the width direction, and the scan is repeated every time a constant cutting amount is applied, and the completion of the dressing process of the dressing surface is determined by determining whether or not the dressing process is completed due to contact between the grinding wheel and the dresser. By crushing the abrasive grains of the grinding wheel Automatic judgment based on the AE signal generated Dressing completion determination deviceA method for determining completion of dressing, comprising: (b) an integrated intensity value calculation step of calculating an integrated intensity value of an AE signal intensity generated during a dresser scan for each dressing scan; and (c) calculating the integrated intensity value of the AE signal intensity for each dressing scan calculated by the integrated intensity value calculation step. is equal to or less than the maximum value of the integrated intensity of the AE signal intensity obtained by the dressing scans repeated up to that point, it is determined that the increase in the integrated intensity value of the AE signal intensity integrated for each dressing scan has saturated, and and a dressing completion determination step of determining completion of the dressing process based on the result of the dressing process.

[0009] The gist of the second invention is that (a) the grinding wheel and the dresser come into contact with each other. By crushing the abrasive grains of the grinding wheel a dressing completion determination device for automatically determining the completion of a dressing process of the dressing surface based on the AE signal, the dressing scan being performed by causing the dresser to scan across the dressing surface in a width direction at a constant feed rate while sliding the dresser against the dressing surface of the grinding wheel, and the dressing completion determination device for automatically determining the completion of a dressing process of the dressing surface based on the AE signal, the dressing scan being performed repeatedly every time a constant depth of cut is provided, the dressing completion determination device comprising: (b) an integrated intensity value calculation unit for calculating an integrated intensity value obtained by integrating the AE signal intensity generated during the dressing scan, for each dressing scan; and (c) an integrated intensity value of the AE signal intensity integrated for each dressing scan by the integrated intensity value calculation unit. is equal to or less than the maximum value of the integrated intensity of the AE signal intensity obtained by the dressing scans repeated up to that point, it is determined that the increase in the integrated intensity value of the AE signal intensity integrated for each dressing scan has saturated, and and a dressing completion determination unit that determines the completion of the dressing process based on the result of the dressing process.

[0010] The gist of the third invention is that in the second invention, (d) an AE signal judgment threshold determination unit that determines an AE signal judgment threshold based on the AE signal intensity obtained from the AE sensor in a non-dressing state where the dresser is separated from the dressing surface of the grinding wheel, and the time from when the AE signal intensity obtained from the AE sensor exceeds the AE signal judgment threshold to when it falls below the AE signal judgment threshold is calculated; , a spark time, which is the time during which the dresser is in contact with the dressing surface of the grinding wheel. as(e) a spark time calculation unit that calculates a theoretical spark time based on the feed speed of the dresser by the dresser feed mechanism and the width dimension of the dressing surface of the grinding wheel; and (f) a shape modification pass / fail determination unit that determines the completion of the shape modification based on the spark time calculated by the spark time calculation unit for each dressing scan exceeding the spark time determination threshold, and (g) the dressing completion determination unit determines the completion of the dressing process based on the saturation of the increase in the integrated intensity value of the AE signal intensity calculated by the integrated intensity value calculation unit for each dressing scan and the determination of the completion of the shape modification by the shape modification pass / fail determination unit.

[0012] No. 4 The gist of the invention is the second invention or the third invention (i) an AE signal judgment threshold determination unit that determines an AE signal judgment threshold based on the AE signal intensity obtained from the AE sensor in a non-dressing state where the dresser is separated from the dressing surface of the grinding wheel, and (j) a signal that exceeds the AE signal judgment threshold among signals output from the AE sensor during the dressing scan is used as the AE signal intensity used to determine the completion of the dressing process.

[0013] No. 5 The gist of the invention is 4 In the present invention, (l) the AE signal judgment threshold determination unit determines the AE signal judgment threshold based on an average value or a maximum value of an AE signal intensity obtained from the AE sensor when the dresser is scanned by a dresser feed mechanism in a state where the dresser is separated from the dressing surface of the grinding wheel, in a section in which a coefficient of variation is equal to or less than a predetermined value.

[0015] No. 6 The gist of the invention is the second invention to the first invention. 5In any one of the inventions, the AE sensors are a pair of AE sensors respectively provided at different radial positions within a range of the flange to which the grinding wheel is fixed, corresponding to the dressing surface of the grinding wheel, and the dressing completion determination unit determines the completion of the dressing process based on the saturation of the increase in the integrated intensity value of the AE signal intensity obtained from each of the pair of AE sensors, which is respectively integrated for each dressing scan. [Effects of the Invention]

[0016] According to the dressing completion determination method of the first invention, a dressing scan is repeatedly performed every time a certain cutting depth is applied, in which a dresser is brought into sliding contact with a dressing surface of a grinding wheel and the dresser is moved at a constant feed rate across the dressing surface in a width direction, and the completion of the dressing process of the dressing surface is determined by: Dressing completion determination device The grinding wheel and the dresser come into contact with each other. By crushing the abrasive grains of the grinding wheel When automatically determining based on the generated AE signal, an integrated intensity value calculation step calculates an integrated intensity value of the AE signal intensity generated during the dresser scan for each dressing scan, and a dressing completion determination step determines whether or not the dressing is completed based on the integrated intensity value of the AE signal intensity calculated for each dressing scan. is equal to or less than the maximum value of the integrated intensity of the AE signal intensity obtained by the dressing scans repeated up to that point, it is determined that the increase in the integrated intensity value of the AE signal intensity integrated for each dressing scan has saturated, and this determination The completion of the dressing process is determined based on the above. This makes it possible to determine the completion of dressing of the grinding wheel with high accuracy without requiring any complicated preparation work.

[0017] According to the dressing completion determination device of the second invention, the dressing completion determination device can determine whether or not the dressing completion occurs due to contact between the grinding wheel and the dresser. By crushing the abrasive grains of the grinding wheela dressing completion determination device for automatically determining the completion of a dressing process of the dressing surface based on the AE signal, the dressing scan being performed by causing the dresser to scan at a constant feed rate across the dressing surface in a width direction while sliding the dresser against the dressing surface of the grinding wheel, the dressing scan being performed repeatedly every time a constant depth of cut is provided; an integrated intensity value calculation unit calculates an integrated intensity value of the AE signal intensity generated during the dresser scan for each dressing scan; and a dressing completion determination unit calculates the integrated intensity value of the AE signal intensity calculated for each dressing scan. is equal to or less than the maximum value of the integrated intensity of the AE signal intensity obtained by the dressing scans repeated up to that point, it is determined that the increase in the integrated intensity value of the AE signal intensity integrated for each dressing scan has saturated, and this determination The completion of the dressing process is determined based on the above. This makes it possible to determine the completion of dressing of the grinding wheel with high accuracy without requiring any complicated preparation work.

[0018] According to the dressing completion determination device of the third invention, the spark time calculated by the spark time calculation unit , the time from when the AE signal intensity exceeds the AE signal determination threshold to when it falls below the AE signal determination threshold. When the completion of the shape modification is determined based on the fact that the spark time has exceeded the spark time determination threshold set by the spark time determination threshold setting unit, the completion of the dressing process is determined by the dressing completion determining unit based on the fact that the increase in the integrated intensity value of the AE signal intensity calculated for each dressing scan by the integrated intensity value calculating unit has saturated and the fact that the shape modification pass / fail determining unit has determined that the shape modification is complete. This further improves the accuracy of the determination of the completion of the dressing process.

[0020] No. 4 According to the dressing completion determination device of the present invention, a signal exceeding an AE signal determination threshold determined based on a signal output from an AE sensor in a non-dressing state where the grinding wheel and the dresser are not in contact with each other is used by an AE signal supply unit as the AE signal intensity used for determining the completion of the dressing process, thereby further improving the accuracy of determining the completion of the dressing process.

[0021] No. 5According to the dressing completion determination device of the present invention, the AE signal determination threshold determiner determines the AE signal determination threshold based on the average or maximum value of the signal output from the AE sensor when the dresser is moved by the dresser feed mechanism while the dresser is separated from the dressing surface of the grinding wheel and scanned, within a range in which the coefficient of variation is equal to or less than a predetermined value. This further improves the accuracy of determining the completion of the dressing process. Furthermore, the AE signal determination threshold need only be slightly larger than the average or maximum value of the signal and does not need to be determined based on strict experimental values, so it can be easily set, for example, to 1.1 times the average or maximum value.

[0023] No. 6 According to the dressing completion determination device of the present invention, the AE sensors are a pair of AE sensors respectively provided at different radial positions within a range of the flange to which the grinding wheel is fixed, corresponding to the dressing surface of the grinding wheel, and the dressing completion determination unit determines the completion of the dressing process based on the saturation of the increase in the integrated intensity value of the AE signal intensity obtained by integrating the AE signal intensity obtained from the pair of AE sensors for each dressing scan, thereby further improving the accuracy of the determination of the completion of the dressing process. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram illustrating the configuration of a dressing apparatus equipped with a dressing completion determination device according to an embodiment of the present invention. [Figure 2] 2 is a perspective view briefly explaining the main parts of a double-disc surface grinding machine using a surface grinding wheel that is dressed by the dressing device of FIG. 1. FIG. [Figure 3] FIG. 2 is a cross-sectional view illustrating the mounting structure of the surface grinding wheel of FIG. [Figure 4] 4 is a diagram illustrating in detail a flange to which the surface grinding wheel of FIG. 3 is attached. FIG. [Figure 5] The graph shows the AE signal intensities obtained from the outer periphery side AE ​​sensor and the inner periphery side AE ​​sensor during repeated dressing scans. [Figure 6] 6 is a diagram illustrating calculation of spark time STs from the AE signal waveform of FIG. 5 and an integration interval of signal intensity. [Figure 7] FIG. 10 is a diagram schematically showing integrated intensity values ​​Xs and spark times STs of AE signals obtained for each dressing scan in the dressing process. [Figure 8] 2 is a diagram showing the first half of a flowchart illustrating the control operation of the electronic control device of FIG. 1. FIG. [Figure 9] 2 is a diagram showing the second half of a flowchart illustrating the control operation of the electronic control device of FIG. 1. FIG. [Figure 10] 1 is a time-series chart showing the ratio (%) of the actual spark time STs, which is the ST evaluation value obtained for each peak waveform, to the theoretical spark time ST (=Wd / Vd), the pass / fail judgment of the shape modification indicating whether the ratio of the actual spark time STs to the theoretical spark time ST exceeds 95%, the integrated intensity value Xs, which is the strength evaluation value obtained for each peak waveform, and the pass / fail judgment of the dressing indicating whether the integrated intensity value Xs has saturated, when using the AE signal intensity Xi based on the signal from the outer periphery AE sensor 16a and when using the AE signal intensity Xi based on the signal from the inner periphery AE sensor 16b. [Figure 11] This is a line graph showing, in time series, the ST evaluation value (actual spark time STs) and the integrated intensity value Xs, which is the intensity evaluation value, when the AE signal intensity Xi based on the signal from the outer periphery side AE ​​sensor 16a is used. [Figure 12] FIG. 1 is a diagram showing an example of the surface shape of a grinding wheel measured by a stylus-type shape measuring instrument, together with the difference ΔTH (mm) between the contact start height and the truing completion height. [Figure 13] This figure shows the dressing depth CD until dressing completion was determined for five grinding wheels A to E, when dressing was performed using the same experimental conditions as experimental condition 1, and the truing amount ΔTH predicted from the surface shape of the grinding wheels measured in advance using a stylus-type shape measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present invention will be described in detail below with reference to the drawings. Note that the drawings in the following embodiment are for explaining the essential parts related to the invention, and the dimensions and shapes are not necessarily drawn accurately. [Example]

[0026] 1, a dressing device 10 performs a dressing process in which a dresser 12 is brought into sliding contact with a dressing surface 15 of a surface grinding wheel 14 to sharpen and modify the shape of the dressing surface 15. The dressing surface 15 is the portion of the grinding surface of the surface grinding wheel 14 that is the target of dressing (shape modification and sharpening) by the dresser 12, including the portion that contributes to grinding. The dressing device 10 includes AE sensors 16a and 16b that detect elastic waves generated when the grinding wheel 14 and the dresser 12 contact each other during the dressing process and output an AE signal, a dresser scanning motor 18 that causes the dresser 12 to reciprocate and scan at a constant feed rate across the dressing surface 15 in the width direction while sliding the dresser 12 against the dressing surface 15 of the surface grinding wheel 14, and a dresser feed motor 20 that causes the dresser 12 to cut into the dressing surface 15 by a constant cutting amount for each scan. The dresser feed mechanism 22 repeatedly performs dressing scans by moving the dresser 12 back and forth at a constant feed speed across the width of the dressing surface 15 while keeping the dresser 12 in sliding contact with the dresser feed mechanism 5, every time a constant cutting depth is provided; a dressing drive control device 26 that controls the drive of the dresser scan motor 18 and dresser feed motor 20 of the dresser feed mechanism 22 and the grinding wheel rotation drive motor 24 that rotates the surface grinding wheel 14 in accordance with commands; and an electronic control device 28 that outputs control commands to the dressing drive control device 26.

[0027] In this embodiment, the dresser 12 is a longitudinal single-stone dresser embedded with one end face of a single pillar-shaped diamond exposed. The dresser feed mechanism 22 includes a cutting mechanism (not shown) that feeds the dresser 12 in the longitudinal direction of the dresser 12 toward the surface grinding wheel 14, and a scanning mechanism (not shown) that moves the dresser 12 back and forth along the dressing surface 15 of the surface grinding wheel 14.

[0028] 2 is a perspective view showing the main parts of a vertical double-disc surface grinding machine 32 to which the surface grinding wheel 14 and a similar surface grinding wheel 30 are applied. The double-disc surface grinding machine 32 is equipped with a pair of opposing surface grinding wheels 14 and 30 that are rotated relative to each other about a vertical rotation axis CL, and a carrier plate 36 that carries a circular workpiece 34, such as the inner or outer ring of a bearing, so that it passes between the pair of surface grinding wheels 14 and 30, and performs surface grinding on both end surfaces of the workpiece 34.

[0029] The pair of surface grinding wheels 14 and 30 have the same configuration, so the following description will focus on the surface grinding wheel 14. As shown in FIG. 3, the back surface of the surface grinding wheel 14 is in close contact with a thick, disk-shaped flange 40 (not shown), which rotates integrally with the spindle 38 of the double-disc surface grinding machine 32. The back surface of the surface grinding wheel 14 is fixed to the flange 40 using a fastening bolt (not shown) that threads into a nut (not shown) embedded in the surface grinding wheel 14. A flat, annular dressing surface 15 is formed on the end surface of the pair of end surfaces of the surface grinding wheel 14 that is not in close contact with the flange 40. In this embodiment, the width direction of the dressing surface 15 refers to the radial direction passing through the rotation center line CL of the surface grinding wheel 14.

[0030] An electronic component storage chamber 42 is formed in the flange 40 and opens onto the surface opposite the surface grinding wheel 14. The opening of the electronic component storage chamber 42 is closed by a circular cover plate 44 made of a material that allows radio waves to pass through, such as plastic or ceramic, via a sealing rubber plate 46. The cover plate 44 and the sealing rubber plate 46 are fixed by fastening bolts 48 that pass through them and screw into the flange 40.

[0031] 4, an electronic circuit board 50 is disposed within an electronic component housing 42 formed in the flange 40. The electronic circuit board 50 includes a pair of outer AE sensors 16a and inner AE sensors 16b, a preamplifier for amplifying the output signals of the outer AE sensors 16a and inner AE sensors 16b, an A / D converter for converting the output signals of the preamplifiers into digital signals, a transmission module for transmitting the output signals of the outer AE sensors 16a and inner AE sensors 16b that have been converted into digital signals by the A / D converter, and a pair of power supply batteries 52. The A / D converter has high resolution and converts the AE signal SAE into a digital signal at a sampling period of 10 μsec (microseconds) or less, preferably 5 μsec or less, and more preferably 1 μsec or less.

[0032] The outer periphery side AE ​​sensor 16a and the inner periphery side AE ​​sensor 16b are arranged along one radial direction of the flange 40. The outer periphery side AE ​​sensor 16a is located at a position that is 80% or more, preferably 90%, of the radius of the flange 40 from the rotation axis CL of the flange 40 toward the outer periphery side, and the inner periphery side AE ​​sensor 16b is located at a position that is 35% or more and 50% or less, preferably about 40%, of the radius of the flange 40 from the rotation axis CL of the flange 40 toward the outer periphery side.

[0033] 1, the dressing device 10 is equipped with a receiving circuit 56 having an antenna 54 for receiving the AE signal SAE transmitted from the transmitting module in the electronic circuit board 50. The electronic control device 28 is a so-called microcomputer including a CPU, ROM, RAM, an interface, etc. The CPU utilizes the temporary storage function of the RAM and operates the dressing drive control device 26 in accordance with a program previously stored in the ROM to repeatedly perform a dressing scan, in which the dresser 12 is brought into sliding contact with the dressing surface 15 of the surface grinding wheel 14 and moved at a constant feed rate across the dressing surface 15 in the width direction, every time a constant depth of cut is provided. The electronic control device 28 also processes the AE signal SAE received by the receiving circuit 56 during dressing, determines the completion of the dressing process for sharpening and shape correction of the dressing surface 15, outputs a dressing completion command signal to the dressing drive control device 26, and calculates numerical values, graphs, figures, etc. representing the state of the dressing surface and displays them on the surface state display device 58.

[0034] The electronic control device 28 also functions as a dressing completion determination device, and functionally comprises a frequency analysis unit 60, an AE signal determination threshold setting unit 62, a spark time determination threshold setting unit 64, a spark time calculation unit 66, a shape modification pass / fail determination unit 68, an integrated intensity value calculation unit 70, a dressing pass / fail determination unit 72, and a dressing completion determination unit 74.

[0035] The frequency analysis unit 60, which corresponds to the frequency analysis step, performs frequency analysis (FFT) of the A / D converted AE signal SAE during dressing of the grinding wheel 14 to generate a power spectrum showing various signal powers indicating the magnitude of frequency components on the frequency axis (horizontal axis) for each frequency in a two-dimensional coordinate system with the vertical axis indicating signal power and the horizontal axis indicating frequency, and discriminates signal components from the AE signal SAE in a frequency band, for example, a wavelength band of 45 to 75 kHz, that sensitively reacts to the fracture of abrasive grains in the surface grinding wheel 14 during the dressing process, and outputs the integrated value of these signal components as the AE signal intensity Xi. For example, Figure 5 shows the AE signal intensities Xi sequentially output from the frequency analysis unit 60 based on the AE signals SAE obtained from the outer periphery AE sensor 16a and the inner periphery AE sensor 16b during repeated dressing scans, each expressed as an actual peak waveform. In the non-dressing section R1 in Figure 5, the AE signal intensity XiN under no load is shown, where the dresser 12 is not in contact with the dressing surface 15 of the grinding wheel 14, and in the dressing section R2, the peak waveform of the AE signal intensity Xi that is repeatedly generated with each dressing scan due to the dresser 12 coming into contact with the dressing surface 15 of the grinding wheel 14 is shown.

[0036] The AE signal judgment threshold setting unit 62 corresponds to the AE signal judgment threshold setting step, and calculates the no-load AE signal intensity XiN obtained from the outer periphery side AE ​​sensor 16a and the inner periphery side AE ​​sensor 16b in the non-dressing section R1 in which the dresser 12 is scanned for dressing by the dresser feed mechanism 22 without contacting the dresser 12 with the dressing surface 15 of the grinding wheel 14, and sets an AE signal judgment threshold P based on the no-load AE signal intensity XiN for removing noise generated under no-load conditions in a subsequent step. The amount by which the AE signal magnitude (AE signal intensity) Xi exceeds the AE signal judgment threshold P is a signal component resulting from contact between the grinding wheel 14 and the dresser 12 during the dressing process, and is subject to the dressing completion evaluation described below. For example, the AE signal judgment threshold setting unit 62 determines the coefficient of variation CV of the no-load AE signal intensity XiN from at least 100 pieces of data of the no-load AE signal intensity XiN during no-load dressing, calculates the average value Xav or maximum value Xmax of the data in an interval where the coefficient of variation CV is stable, for example, equal to or less than "0.1," and sets the average value Xav × 1.1 or the maximum value Xmax as the AE signal judgment threshold P.

[0037] The coefficient of variation CV of the no-load AE signal intensity XiN is the standard deviation σ of each data item of the no-load AE signal intensity XiN divided by the average value Xav of the no-load AE signal intensity XiN.

[0038] The spark time judgment threshold setting unit 64 corresponds to the spark time judgment threshold setting process, and calculates a theoretical spark time (spark time) ST (=Wd / Vd) from the constant scanning speed Vd of the dresser 12 by the dressing drive control device 26 and the width dimension Wd of the dressing surface 15 of the grinding wheel 14, and sets a spark time judgment threshold STt (sec) by multiplying the theoretical spark time ST by a predetermined ratio (coefficient), for example, "0.95," which determines the completion of shape modification.

[0039] The spark time calculation unit 66 corresponds to the spark time calculation step, and detects, as the actual spark time STs, the cumulative time counted (timed) from the time when the AE signal intensity Xi obtained from the outer periphery-side AE ​​sensor 16a and the inner periphery-side AE ​​sensor 16b exceeds the AE signal determination threshold P to the time when it falls below the AE signal determination threshold P during each dressing scan in the dressing section R2 of Fig. 5 in which the dresser 12 is repeatedly brought into contact with the dressing surface 15 of the grinding wheel 14. In Fig. 6, the peak waveform of the AE signal intensity Xi is schematically represented by a trapezoid to easily explain the meaning of the spark time STs.

[0040] The shape correction pass / fail judgment unit 68 corresponds to the shape correction pass / fail judgment process, and judges whether the actual spark time STs calculated by the spark time calculation unit 66 is equal to or greater than the spark time judgment threshold STt set by the spark time judgment threshold setting unit 64 for each scan of the dresser 12, and if it is greater than the spark time STs, judges that the shape correction is pass (completed).

[0041] The integrated intensity value calculation unit 70 corresponds to the integrated intensity value calculation step, and calculates an integrated intensity value Xs for each dressing scan by integrating components of the AE signal intensities Xi obtained from the outer periphery-side AE ​​sensor 16a and the inner periphery-side AE ​​sensor 16b that exceed the AE signal judgment threshold P within a section STs during a dressing scan period in which the dresser 12 is repeatedly brought into contact with the dressing surface 15 of the grinding wheel 14 in the dressing process of the dressing section R2 in Fig. 5. Fig. 7 shows the peak waveforms of the AE signal intensities Xi obtained sequentially for each dressing scan, schematically represented by rectangular waveforms, and the integrated intensity values ​​Xs correspond to the areas of the rectangular waveforms.

[0042] The dressing pass / fail determination unit 72 corresponds to the dressing pass / fail determination step and determines whether the increase in the integrated intensity value Xs calculated for each dressing scan by the integrated intensity value calculation unit 70 from the start of the dressing process has saturated. If the integrated intensity values ​​Xs of the AE signal intensities Xi obtained from the outer periphery AE sensor 16a and the inner periphery AE sensor 16b are both saturated, the dressing pass / fail determination unit 72 determines that the dressing has passed (sharpening has passed). For example, if the integrated intensity value Xs becomes equal to or less than the maximum integrated intensity value Xsp up to that point (Xs≦Xsp), the dressing pass / fail determination unit 72 determines that the increase in the integrated intensity value Xs has saturated. This saturation of the increase in the integrated intensity value Xs indicates saturation of the dressing effect. If STs≧STt and Xs>Xsp, the integrated intensity value Xs during the current dressing scan is updated (set) as the maximum integrated intensity value Xsp. This makes it possible to prevent erroneous judgments when peak waveforms of the AE signal intensity Xi occur intermittently in cases where the grinding machine is used in a retrofit manner that is not linked to the NC.

[0043] The dressing completion determination unit 74 determines the completion of the dressing process based on the fact that the shape modification pass / fail determination unit 68 has determined that the actual spark time STs has exceeded the spark time determination threshold STt and based on the fact that the increase in the integrated intensity value Xs of the AE signal intensities Xi integrated for each dressing scan by the integrated intensity value calculation unit 70 has saturated. That is, when the shape modification pass / fail determination unit 68 has determined that the shape modification has been successful and the dressing related to the dressing has been successful (sharpening passed) by the dressing pass / fail determination unit 72, the dressing completion determination unit 74 determines that the dressing has been completed, stops the dressing operation by the dressing drive control device 26, and causes the surface condition display device 58 to display a display message regarding the completion of dressing.

[0044] 8 and 9 are flowcharts illustrating the main control operations of the electronic control device 28. In FIGS. 8 and 9, in step S1 (hereinafter, the term "step" will be omitted), a theoretical spark time ST (=Wd / Vd) is calculated from the constant scanning speed Vd of the dresser 12 by the dressing drive control device 26 and the width dimension Wd of the dressing surface 15 of the grinding wheel 14, both of which have been input in advance. In S2, the theoretical spark time ST is multiplied by a predetermined ratio (coefficient), for example, "0.95," which determines whether shape modification is complete, to set a spark time determination threshold STt (sec). In this embodiment, S1 and S2 correspond to the spark time determination threshold setting unit 64.

[0045] In S3, the no-load AE signal intensities XiN obtained based on the signals from the AE sensors 16a and 16b when the dresser 12 is not in contact with the dressing surface 15 of the grinding wheel 14 in the non-dressing section R1 are read. In S4, it is determined whether the number of data points for the no-load AE signal intensities XiN read in the non-dressing section R1 exceeds 100. If the determination in S4 is negative, steps S3 and subsequent steps are repeated. If the determination is positive, in S5, the coefficient of variation CV (=σ / Xav) of the no-load AE signal intensities XiN is calculated. Next, in S6, it is determined whether the coefficient of variation CV of the no-load AE signal intensities XiN is equal to or less than 0.1. If the determination in S6 is negative, steps S3 and subsequent steps are repeated. If the determination is positive, in S7, the average value Xav × 1.1 or the maximum value Xmax of the data in the section where the coefficient of variation CV is stable, for example, equal to or less than 0.1, is set as the AE signal determination threshold P. In this embodiment, S3 to S7 correspond to the AE signal determination threshold setting unit 62.

[0046] Next, in S8, the dressing process is started, and the dresser 12 is brought into sliding contact with the dressing surface 15 of the surface grinding wheel 14, and is caused to scan back and forth across the dressing surface 15 in the width direction at a constant feed rate, while the dresser 12 cuts into the dressing surface 15 by a constant cutting depth with each scan. As a result, the dressing surface 15 against which the dresser 12 is brought into sliding contact is corrected to a flat shape, and the dressing surface 15 is also dressed.

[0047] In S9, the AE signal intensity Xi during the dressing process is read in. In S10, it is determined whether the magnitude of the AE signal intensity Xi is equal to or greater than the AE signal determination threshold P. If the determination in S10 is positive, contact between the surface grinding wheel 14 and the dresser 12, i.e., the abrasive grains of the surface grinding wheel 14 have started to break down, so in S11 an integrated intensity value Xs (= Xs + Xi) is calculated, and in S12, an actual spark time STs (= STs + Δt), which is the accumulated time since contact between the surface grinding wheel 14 and the dresser 12, i.e., the abrasive grains of the surface grinding wheel 14 have started to break down, is integrated by sequentially adding the integration period Δt.

[0048] If the magnitude of the AE signal intensity Xi falls below the AE signal determination threshold P and the determination in S10 is negative, in S13, the previous AE signal intensity X i-1 is below the AE signal determination threshold P. If the determination in S13 is affirmative, S9 and subsequent steps are repeatedly executed, but if the determination is negative, the spark time STs is determined in S14, and the integrated intensity value Xs of the AE signal intensity Xi is determined in S15. In this embodiment, S9, S10, S12, S13, and S14 correspond to the spark time calculation unit 66, and S9, S10, S11, S13, and S15 correspond to the integrated intensity value calculation unit 70.

[0049] In S16, it is determined whether the determined spark time STs is equal to or greater than the spark time determination threshold STt set in S2. If the determination in S16 is negative, the spark time STs is initialized in S17, and then S9 and subsequent steps are executed. However, if the determination in S16 is positive, a pass flag for the spark time STs is set in S18, and it is determined that the shape modification of the dressing surface 15 has been completed. In this embodiment, S16 and S18 correspond to the shape modification pass / fail determination unit 68.

[0050] In S19, it is determined whether the integrated intensity value Xs of the determined AE signal intensity Xi has saturated, i.e., whether it is equal to or less than the maximum integrated intensity value Xsp up to that point (Xs≦Xsp). If the determination in S19 is negative, the maximum integrated intensity value Xsp is updated to the immediately preceding integrated intensity value Xs in S20, and S9 and subsequent steps are then executed. However, if the determination in S19 is positive, a dressing pass (sharpening pass) flag is set in S21, and it is determined that dressing is complete. In this embodiment, S19 and S21 correspond to the dressing pass determination unit 72.

[0051] Then, in S22 corresponding to the dressing completion determination unit 74, the pass flag for the spark time STs is set and the dressing completion determination is made based on the fact that the pass flag for the dressing regarding the sharpening is set.

[0052] The results of a dressing experiment conducted by the present inventors under the following experimental condition 1 will be described below with reference to FIGS. 5, 10 and 11. FIG. (Experimental condition 1) Processing machine: Vertical axis double-head surface grinder Grinding wheel specifications: 83A 80 H 12 Type of grinding wheel: Surface grinding wheel with an outer diameter of 585 mm Grinding wheel spindle speed: 900 rpm Grinding oil: NK-81P (dilution ratio 50 times) Dresser: 1.0mm LL needle dresser with embedded diamonds Dressing depth: 0.01 mm (Signal processing conditions) FFT analysis data length: 65 ms Integral analysis pitch Δt: 65 ms Integration frequency range: 45 to 75 kHz

[0053] Dressing was performed under the above dressing conditions, and the AE signals obtained from the outer periphery AE sensor 16a and the inner periphery AE sensor 16b were frequency analyzed to integrate frequency components in the range of 45 to 75 kHz, thereby obtaining the AE signal intensity Xi for each frequency analysis period. In addition to the above integration, an average value or an rms value obtained by a band-pass filter may also be used. Figure 5 shows the AE signal intensity Xi obtained at this time on the time axis (horizontal axis). In Figure 5, the AE signal intensity Xi exhibits a mountain-shaped waveform in the section where the dresser is in contact with the surface grinding wheel during the dressing scan, and these peaks are numbered No. 1 to No. 20.

[0054] 10 shows, in time series, the ratio (%) of the actual spark time STs, which is the ST evaluation value obtained for each peak waveform, to the theoretical spark time ST (= Wd / Vd), the pass / fail judgment of the shape correction, which indicates whether the ratio of the actual spark time STs to the theoretical spark time ST continuously exceeds 95%, i.e., whether it has saturated, the integrated intensity value Xs, which is the strength evaluation value obtained for each peak waveform, and the pass / fail judgment of the dressing, which indicates whether the integrated intensity value Xs has saturated. According to this, when the AE signal intensity Xi based on the signal from the outer periphery side AE ​​sensor 16a was used, the pass of the shape correction was determined for peak waveform No. 8, and the pass of the dressing for the dressing was determined for peak waveform No. 18. Furthermore, when the AE signal intensity Xi based on the signal from the inner periphery side AE ​​sensor 16b was used, the pass of the shape correction was determined for peak waveform No. 8, and the pass of the dressing for the dressing was determined for peak waveform No. 17.

[0055] 11 shows a time series of the ST evaluation value (actual spark time STs) and the integrated intensity value Xs, which is the intensity evaluation value, when the AE signal intensity Xi based on the signal from the outer periphery AE sensor 16a is used. Both the ST evaluation value and the intensity evaluation value increase with each dressing scan after the start of dressing, but the ST evaluation value is judged as pass (saturated) before the intensity evaluation value is judged as pass (saturated).

[0056] Next, the inventors performed dressing using the same experimental conditions as experimental condition 1 for five grinding wheels, namely, wheels A to E, which had different degrees of shape deformation, and compared the dressing cut-in amount CD until dressing completion was determined with the truing amount ΔTH predicted from the surface shape of the grinding wheels measured in advance using a stylus-type shape measuring device.

[0057] The dressing cut-in amount CD (=0.01×Nsw) until the completion of dressing is determined is calculated from the dressing cut-in amount 0.01 mm in dressing and the number of scans Nsw of the dresser 12 until the completion of dressing using each of grinding wheels A to E is determined.

[0058] Figure 12 shows an example of the surface profile of a grinding wheel measured using a stylus-type profile measuring instrument. Note that this measurement data is for the profile of the upper surface grinding wheel 14, but for measurement purposes, the data is upside down. The surface profile of the surface grinding wheel 14 shown in the example of Figure 12 has a concave shape on the inner periphery compared to the outer periphery, and this must be flattened to complete truing. In this case, the depth of cut required to complete truing is the truing completion height, where the concave shape on the inner periphery is deepest, from the contact start height, where the dresser and the surface of the surface grinding wheel 14 first come into contact. Therefore, the difference ΔTH (mm) between the contact start height and the truing completion height is determined as the expected truing amount.

[0059] Figure 13 compares the actual dressing cut-in amount CD until dressing completion is determined with the truing amount ΔTH predicted from the surface shape of the grinding wheel measured in advance with a stylus-type profile measuring instrument for each of the above-mentioned grinding wheels A to E. Figure 13 shows that, for each of grinding wheels A to E, when the predicted truing amount ΔTH is large, the actual dressing cut-in amount CD is also large. This confirms that there is a correlation between the actual dressing cut-in amount CD until dressing completion is determined and the truing amount ΔTH predicted from the surface shape of the grinding wheel measured in advance with a stylus-type profile measuring instrument. Because the predicted truing amount ΔTH is the value at the time when shape correction is completed, the actual dressing cut-in amount CD is larger than the predicted truing amount ΔTH by the amount required to remove any remaining damage.

[0060] As described above, according to the dressing completion determination method of the dressing completion determination device (electronic control device 28) of this embodiment, a dressing scan is performed by sliding the dresser 12 against the dressing surface 15 of the surface grinding wheel 14 and moving the dresser 12 at a constant feed rate across the dressing surface 15 in the width direction, and the dressing completion of the dressing process of the dressing surface 15 is automatically determined based on the AE signal SAE. In the integrated intensity value calculation step (integral intensity value calculation unit 70), an integrated intensity value Xs of the AE signal intensity Xi generated during the dresser scan is calculated for each dressing scan. In the dressing completion determination step (dressing completion determination unit 74), the completion of the dressing process is determined based on saturation of the increase in the integrated intensity value Xs of the AE signal intensity Xi calculated for each dressing scan. This allows the completion of dressing of the grinding wheel to be determined with high accuracy without requiring any complicated preparation work.

[0061] Furthermore, according to the dressing completion determination device (electronic control device 28) of this embodiment, the integrated intensity value calculation unit 70 calculates the integrated intensity value Xs of the AE signal intensity Xi generated during the dresser scan for each dressing scan, and the dressing completion determination unit 74 determines the completion of the dressing process based on the saturation of the increase in the integrated intensity value Xs of the AE signal intensity Xi calculated for each dressing scan. This makes it possible to determine the completion of dressing of the grinding wheel with high accuracy without requiring any complicated preparation work.

[0062] Furthermore, according to the dressing completion determination device (electronic control device 28) of this embodiment, when the shape modification pass / fail determination unit 68 determines that the shape modification is complete based on the fact that the actual spark time STs calculated by the spark time calculation unit 66 has exceeded the spark time determination threshold STt set by the spark time determination threshold setting unit 64, the dressing completion determination unit 74 determines that the dressing process is complete based on the fact that the increase in the integrated intensity value Xs of the AE signal intensity Xi calculated for each dressing scan by the integrated intensity value calculation unit 70 has saturated and the fact that the shape modification pass / fail determination unit 68 has determined that the shape modification is successful (completed), this further improves the accuracy of the determination of the completion of the dressing process.

[0063] Furthermore, the dressing completion determination device (electronic control device 28) of this embodiment determines that the increase in the integrated intensity value Xs of the AE signal intensity Xi integrated for each dressing scan has saturated when the integrated intensity value Xs of the AE signal intensity Xi integrated for each dressing scan becomes equal to or less than the maximum integrated intensity Xsp of the AE signal intensity obtained by the dressing scans repeated up to that point. This allows a clear determination of the completion of the dressing process.

[0064] Furthermore, according to the dressing completion determination device (electronic control device 28) of this embodiment, among the signals output from the AE sensors 16a, 16b during the dressing scan, a signal exceeding the AE signal determination threshold P determined based on the signals output from the AE sensors 16a, 16b in the non-dressing section R1 is used as the AE signal intensity Xi used to determine the completion of the dressing process, thereby further improving the accuracy of determining the completion of the dressing process.

[0065] Furthermore, according to the dressing completion determination device (electronic control device 28) of this embodiment, the AE signal determination threshold determiner 62 determines the AE signal determination threshold P based on the average or maximum value of the AE signal intensities Xi output from the AE sensors 16a, 16b during unloaded scanning, in which the dresser feed mechanism is caused to scan the dresser 12 while the dresser 12 is separated from the dressing surface 15 of the surface grinding wheel 14. This further improves the accuracy of determining the completion of the dressing process. Furthermore, the AE signal determination threshold P need only be slightly larger than the average or maximum value of the AE signal intensities Xi and does not need to be determined based on strict experimental values. Therefore, it can be easily set to, for example, approximately 1.1 times the average or maximum value of the AE signal intensities Xi.

[0066] Furthermore, according to the dressing completion determination device (electronic control device 28) of this embodiment, the spark time calculation unit 66 calculates the time from when the AE signal intensity value Xi exceeds the AE signal determination threshold P to when it falls below the AE signal determination threshold P as the actual spark time STs, which is the time during which the dresser 12 is in contact with the dressing surface 15 of the surface grinding wheel 14. This allows the spark time STs to be calculated accurately, making it possible to determine with high precision whether a sufficient dressing width has been obtained, i.e., whether the correction (truing) of the grinding wheel shape has been completed.

[0067] Furthermore, according to the dressing completion determination device (electronic control device 28) of this embodiment, the AE sensors 16a, 16b are a pair of AE sensors respectively provided at different radial positions within a range corresponding to the dressing surface 15 of the surface grinding wheel 14 on the flange 40 to which the surface grinding wheel 14 is fixed, and the dressing completion determination unit 74 determines the completion of the dressing process based on the saturation of the increase in the integrated intensity value Xs of the AE signal intensities Xi obtained respectively from the pair of AE sensors 16a, 16b, which are integrated for each dressing scan. This further improves the accuracy of the determination of the completion of the dressing process.

[0068] Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can also be applied to other embodiments.

[0069] For example, the electronic control device 28 in the above-described embodiment was provided with the spark time judgment threshold setting unit 64, the spark time calculation unit 66, and the shape correction pass / fail judgment unit 68. However, depending on the type of work, the pass / fail of the shape correction may be judged before the pass / fail of the dressing for sharpening, as shown in Fig. 10, and in such cases, these units may not necessarily be provided. In this case, the dressing completion judgment unit 74 judges the completion of dressing based only on the judgment result of the dressing pass / fail judgment unit 72.

[0070] Furthermore, in the above-described embodiment, the completion of dressing is evaluated based on whether or not the integrated intensity value Xs, which is the sum of the scanning AE signal intensities Xi for each dressing scan that exceed the AE signal judgment threshold P, has saturated. However, if the AE signal judgment threshold P is small enough that it does not significantly affect the accuracy of the dressing completion judgment, the completion of dressing may be evaluated based on whether or not the integrated intensity value Xs of the scanning AE signal intensities Xi for each dressing scan has saturated, without using the AE signal judgment threshold P.

[0071] In the above-described embodiment, the outer AE sensor 16 a and the inner AE sensor 16 b are used, but only one of the outer AE sensor 16 a and the inner AE sensor 16 b may be used. In this case, the dressing pass / fail determination unit 72 determines whether the dressing is pass or not based on only the signal detected from either the outer AE sensor 16 a or the inner AE sensor 16 b.

[0072] In the above-described embodiment, the surface grinding wheel 14 having the annular flat dressing surface 15 is used for dressing, but a grinding wheel having a cylindrical grinding surface may also be used. In this case, the dresser 12 scans across the cylindrical grinding surface in a direction parallel to the rotation centerline.

[0073] The surface grinding wheel 14 in the above-described embodiment and the grinding wheel having a cylindrical grinding surface may be made of abrasive grains bonded together with various bonds such as resinoid grinding wheels and vitrified grinding wheels.

[0074] Furthermore, the dresser 12 in the above-described embodiment was a single-stone dresser in which one columnar diamond was embedded, but a rotary dresser in which multiple diamonds are embedded on the outer circumferential surface or other dressing tools may also be used.

[0075] It should be noted that the above is merely one embodiment of the present invention, and various modifications can be made to the present invention without departing from the spirit of the present invention. [Explanation of symbols]

[0076] 10: Dressing device 12: Dresser 14: Flat grinding wheel 16a: Outer AE sensor 16b: Inner AE sensor 28: Electronic control device (dressing completion determination device) 62: AE signal judgment threshold setting unit 64: Spark time judgment threshold setting unit 66: Spark time calculation section 68: Shape correction pass judgment section 70: Integrated intensity value calculation unit (integrated intensity value calculation step) 72: Dressing acceptance judgment section 74: Dressing completion determination unit (dressing completion determination process) STs: Actual spark times STt: Spark time judgment threshold Xs: Integrated intensity value

Claims

1. A dressing completion determination method for a dressing completion determination device, which automatically determines the completion of dressing of a dressing surface based on an AE signal generated by fracture of abrasive grains of the grinding wheel due to contact between the grinding wheel and the dresser, by repeatedly performing a dressing scan in which the dresser is moved at a constant feed rate across the dressing surface in a width direction while being brought into sliding contact with the dresser on the dressing surface, each time a constant depth of cut is provided, the method comprising: an integrated intensity value calculation step of calculating an integrated intensity value of AE signal intensity generated during a dresser scan for each dressing scan; a dressing completion determination step of determining that an increase in the integrated intensity value of the AE signal intensity calculated for each dressing scan in the integrated intensity value calculation step has saturated based on the fact that the integrated intensity value of the AE signal intensity calculated for each dressing scan in the integrated intensity value calculation step has become equal to or less than the maximum value of the integrated intensity of the AE signal intensity obtained by the dressing scans repeated up to that point, and determining completion of the dressing process based on this determination. A method for determining completion of dressing, comprising:

2. a dressing completion determination device for automatically determining the completion of a dressing process of the dressing surface based on the AE signal, the dressing scan being performed by causing the dresser to slide against the dressing surface of the grinding wheel and scan the dresser at a constant feed rate across the dressing surface in a width direction, the dressing scan being performed repeatedly every time a constant depth of cut is applied, the dressing completion determination device comprising: an AE sensor for detecting an AE signal generated by fracture of abrasive grains of the grinding wheel due to contact between the grinding wheel and the dresser; an integrated intensity value calculation unit that calculates an integrated intensity value obtained by integrating AE signal intensities generated during the dressing scan for each of the dressing scans; a dressing completion determination unit that determines that an increase in the integrated intensity value of the AE signal intensity integrated for each dressing scan has saturated based on the integrated intensity value of the AE signal intensity integrated for each dressing scan by the integrated intensity value calculation unit becoming equal to or less than a maximum value of the integrated intensity of the AE signal intensity obtained by the dressing scans repeated up to that point, and determines completion of the dressing process based on the determination. A dressing completion determination device characterized by:

3. An AE signal judgment threshold determination unit that determines an AE signal judgment threshold based on the AE signal intensity obtained from the AE sensor in a non-dressing state where the dresser is separated from the dressing surface of the grinding wheel, and a spark time calculation unit that calculates the time from when the AE signal intensity obtained from the AE sensor exceeds the AE signal judgment threshold to when it falls below the AE signal judgment threshold as the spark time, which is the time when the dresser is in contact with the dressing surface of the grinding wheel; a spark time determination threshold setting unit that sets a spark time determination threshold that is shorter than a theoretical spark time calculated based on the feed speed of the dresser by the dresser feed mechanism and the width dimension of the dressing surface of the grinding wheel; a shape modification pass / fail determination unit that determines completion of the shape modification based on whether the spark time calculated for each dressing scan by the spark time calculation unit exceeds the spark time determination threshold, The dressing completion determination unit determines the completion of the dressing process based on whether an increase in the integrated intensity value of the AE signal intensity calculated for each dressing scan by the integrated intensity value calculation unit has saturated and whether the shape modification pass / fail determination unit has determined that the shape modification has been completed.

3. The dressing completion determination device according to claim 2.

4. an AE signal judgment threshold determining unit that determines an AE signal judgment threshold based on an AE signal intensity obtained from the AE sensor in a non-dressing state in which the dresser is separated from the dressing surface of the grinding wheel; Among the signals output from the AE sensor during the dressing scan, a signal exceeding the AE signal determination threshold is used to determine whether the dressing process is completed.

4. The dressing completion determination device according to claim 2 or 3.

5. The AE signal judgment threshold determination unit determines the AE signal judgment threshold based on an average value or a maximum value of an AE signal intensity obtained from the AE sensor when the dresser is moved by a dresser feed mechanism in a state where the dresser is separated from the dressing surface of the grinding wheel and the coefficient of variation is equal to or less than a predetermined value.

5. The dressing completion determination device according to claim 4.

6. The AE sensors are a pair of AE sensors respectively provided at different radial positions within a range corresponding to the dressing surface of the grinding wheel on the flange to which the grinding wheel is fixed, and the dressing completion determination unit determines the completion of the dressing process based on whether the increase in the integrated intensity value of the AE signal intensity obtained by integrating the AE signal intensity obtained from the pair of AE sensors for each dressing scan has reached saturation.

6. The dressing completion determination device according to claim 2, wherein the dressing completion determination device is a device for determining whether or not a dressing is completed.

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