Coolant flow rate setting device

Abstract

To provide a coolant flow rate setting device that sets a flow rate of a coolant for achieving prevention of grinding burn, suppression of increase in power consumption, and improvement in machining accuracy, in machining by a grinder.SOLUTION: A coolant flow rate setting device 1 that sets a flow rate of a coolant in a grinder which grinds a portion to be machined into a final target shape while supplying the coolant to the portion to be machined of a workpiece, comprises: a first correspondence relationship storage unit 51 which stores a grinding efficiency correspondence relationship being a correspondence relationship between a burn boundary grinding efficiency representing a maximum grinding efficiency of the grinder within a range where grinding burn does not occur in the portion to be machined and the flow rate of the coolant supplied to the portion to be machined when the burn boundary grinding efficiency is exhibited; a commanded grinding efficiency calculation unit 45 which calculates a commanded grinding efficiency for the grinder on the basis of a command value for machining the workpiece; and a coolant flow rate setting unit 55 which sets a flow rate of the coolant to be supplied to the portion to be machined on the basis of the commanded grinding efficiency and the grinding efficiency correspondence relationship.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a coolant flow rate setting device. [Background technology]

[0002] Conventionally, in grinding a workpiece, in order to prevent grinding burns from occurring on the processed part, a large amount of coolant is supplied to the processed part during processing to cool the processed part. For example, Patent Document 1 discloses a configuration that utilizes the fact that the coolant supplied to the processed part increases the power consumption of the rotating spindle of the processing tool, and starts processing when the power consumption exceeds a specified value, thereby preventing processing from starting in a dry state where no coolant is supplied.

[0003] Furthermore, since grinding burns may occur on the processed part even when coolant is supplied, it is also necessary to detect the occurrence of grinding burns.For example, Patent Document 2 discloses a configuration for detecting grinding burns by detecting structural changes that cause grinding burns in the processed part based on the output signal of an eddy current sensor installed near the processed part. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-329019 [Patent Document 2] Japanese Patent Application Publication No. 2018-189603 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while increasing the flow rate of coolant supplied to the workpiece generally improves the cooling effect, if the flow rate of coolant is excessive, the increased power consumption of the tool rotation spindle will outweigh the improved cooling effect, resulting in an increase in unnecessary power consumption and a decrease in the machining accuracy of the tool. Therefore, it is necessary to adjust the flow rate of the coolant, but Patent Documents 1 and 2 do not disclose how to adjust the flow rate of the coolant, leaving room for improvement.

[0006] The present invention aims to provide a coolant flow rate setting device that sets the flow rate of coolant to prevent grinding burn, suppress increases in power consumption, and improve machining accuracy during machining using a grinding machine. [Means for solving the problem]

[0007] One aspect of the present invention is 1. A coolant flow rate setting device for setting a flow rate of a coolant in a grinding machine that grinds a processed portion of a workpiece into a final target shape while supplying the coolant to the processed portion, a first correspondence relationship storage unit that stores a grinding efficiency correspondence relationship, which is a correspondence relationship between a burnt boundary grinding efficiency that indicates the maximum grinding efficiency of the grinding machine within a range in which grinding burn does not occur on the processed part, and a flow rate of coolant that was supplied to the processed part when the burnt boundary grinding efficiency was exhibited; a command grinding efficiency calculation unit that calculates a command grinding efficiency for the grinding machine based on a command value for machining the workpiece; a coolant flow rate setting unit that sets the flow rate of the coolant to be supplied to the workpiece based on the command grinding efficiency acquired by the command grinding efficiency calculation unit and the grinding efficiency correspondence relationship; The coolant flow rate setting device includes: [Effects of the Invention]

[0008] According to the above-described aspect, the flow rate of the coolant supplied to the workpiece is set based on the grinding efficiency correspondence relationship, which is the correspondence relationship between the burnt boundary grinding efficiency, which indicates the maximum grinding efficiency within the range where grinding burn does not occur on the workpiece, and the flow rate of the coolant supplied to the workpiece when the burnt boundary grinding efficiency is exhibited. Therefore, the flow rate of the coolant is optimized, which makes it possible to prevent grinding burn, suppress increases in power consumption, and improve machining accuracy.

[0009] As described above, according to the above aspect, it is possible to provide a coolant flow rate setting device that sets the flow rate of coolant to prevent grinding burn, suppress increases in power consumption, and improve processing accuracy during processing using a grinding machine. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a conceptual diagram showing a configuration including a coolant flow rate setting device and a grinding machine in the first embodiment. [Figure 2] FIG. 2 is a functional block diagram showing the configuration of a coolant flow rate setting device according to the first embodiment. [Figure 3] FIG. 2 is a diagram showing the configuration of a sizing device in the first embodiment. [Figure 4] FIG. 3 is a diagram showing an output signal of an eddy current sensor in the first embodiment. [Figure 5] 5A is a diagram showing an output signal of an eddy current sensor, FIG. 5B is a diagram showing an actual cutting depth, and FIG. 5C is a diagram showing power consumption of a driving device for a tool spindle in the first embodiment. [Figure 6] FIG. 4 is a diagram showing the correspondence relationship between the actual cutting depth and grinding efficiency in the first embodiment. [Figure 7] FIG. 3 is a conceptual diagram showing the correspondence relationship between the rotation speed of the tool spindle and the burnt boundary grinding efficiency in the first embodiment. [Figure 8] FIG. 10A is a conceptual diagram showing the grinding efficiency correspondence relationship stored in the first correspondence relationship storage unit in the first embodiment; FIG. 10B is a conceptual diagram showing the case where the coolant flow rate is set based on the command grinding efficiency and the grinding efficiency correspondence relationship. [Figure 9]1A is a conceptual diagram showing the grinding power correspondence relationship stored in the second correspondence relationship storage unit in embodiment 1, and FIG. 1B is a conceptual diagram showing the case where burn depth is evaluated based on the grinding power and the grinding power correspondence relationship. [Figure 10] In embodiment 1, (a) a conceptual diagram showing the coolant flow rate / power consumption correspondence relationship stored in the third correspondence relationship memory unit, and (b) a conceptual diagram when monitoring the coolant flow rate based on the coolant power consumption and the coolant flow rate / power consumption correspondence relationship. [Figure 11] FIG. 10A is a conceptual diagram showing the grinding power / coolant power consumption correspondence relationship stored in the fourth correspondence relationship storage unit in the first embodiment; and FIG. 10B is a conceptual diagram showing the case where grinding burn occurrence is monitored based on the coolant power consumption and the grinding power / coolant power consumption correspondence relationship. [Figure 12] FIG. 3 is a functional block diagram showing the configuration of a burn depth estimation unit in the first embodiment. [Figure 13] 3 is an enlarged cross-sectional view of the periphery of a workpiece when up-cut grinding is performed in the first embodiment. FIG. [Figure 14] 1A is an enlarged cross-sectional view of the area around the workpiece showing the cooling liquid in a nucleate boiling state, and FIG. 1B is an enlarged cross-sectional view of the area around the workpiece showing the cooling liquid in a film boiling state in the first embodiment. [Figure 15] FIG. 3 is a conceptual diagram illustrating the amount of heat Jm passing through the film boiling region in the first embodiment. [Figure 16] 10 is a conceptual diagram showing the correspondence relationship between the amount of heat passing through the film boiling region and the burn depth stored in a fifth correspondence relationship storage unit in the first embodiment. FIG. [Figure 17] FIG. 2 is a flowchart of a grinding process in the first embodiment. [Figure 18] FIG. 4 is a flowchart of a coolant flow rate setting process according to the first embodiment. [Figure 19] FIG. 4 is a flowchart of a burn evaluation process according to the first embodiment. [Figure 20] FIG. 4 is a flowchart of a coolant abnormality determination process according to the first embodiment. [Figure 21] FIG. 4 is a flowchart of a process for determining sharpness and cooling capacity in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1) The coolant flow rate setting device 1 of the first embodiment sets the flow rate of coolant supplied to a portion to be machined of a workpiece W in a grinding machine 2. Each component will be described in detail below.

[0012] 1. Overview of Grinding Machine 2 In the first embodiment, as shown in FIG. 1 , a grinding machine 2 rotates the workpiece W about the center line C of the workpiece W, 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 surface of the workpiece W multiple times to form the workpiece W into a predetermined final target shape. The grinding machine 2 may be a table traverse type grinding machine, a wheelhead traverse type grinding machine, or the like. The grinding machine 2 may also be a cylindrical grinding machine, a cam grinding machine, or the like.

[0013] 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.

[0014] 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 grinding machine 2 can grind workpieces having various shapes.

[0015] The processing unit 3 includes a coolant flow rate setting device 1 and a control device 31 that controls the grinding machine 2. The coolant flow rate setting device 1 sets the flow rate of the coolant supplied to the processed portion of the workpiece W in the grinding machine 2, and the control device 31 controls the grinding machine 2, thereby controlling the grinding process.

[0016] The coolant flow rate setting device 1 can function as a simulation device independent of the grinding machine 2 and the control device 31, or as a simulation device that operates in conjunction with the grinding machine 2 and the control device 31. In the former case, the coolant flow rate setting device 1 can determine the optimal coolant flow rate, for example, without actually grinding the workpiece W. In the latter case, the coolant flow rate setting device 1 can determine the optimal coolant flow rate by processing in parallel with the grinding process of the workpiece W by the grinding machine 2. The coolant flow rate setting device 1 can also be an integrated system of the grinding machine 2 and the control device 31.

[0017] 2. Configuration of the grinding machine 2 and the control device 31 The configuration of the grinding machine 2 will be described with reference to Fig. 1. In this embodiment 1, the grinding machine 2 is a wheelhead traverse type cylindrical grinding machine as an example. However, a table traverse type can also be used for the grinding machine 2. The 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 sizing device 17, a grinding wheel dressing device 18, a coolant device 19, and an eddy current sensor 20.

[0018] 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 around the center line C of the workpiece W. 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 opposite 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.

[0019] 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 wheel head 15 is provided on the upper surface of the traverse base 14 so as to be movable in the X-axis direction. A tool spindle 16b provided on the wheel head 15 is moved by driving a motor 15a provided on the traverse base 14. The grinding wheel 16 is connected to the tool spindle 16b and rotatably supported via the tool spindle 16b, and rotates by driving a tool spindle motor 16a provided on the wheel head 15. The grinding wheel 16 is composed of a plurality of abrasive grains fixed with a bond material.

[0020] 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.

[0021] 3, the sizing device 17 mainly includes a device main body 171, a pair of contacts 172a, 172b, a pair of fingers 173a, 173b, and a differential transformer 174. The contacts 172a, 172b are provided so as to be able to come into contact with the outer peripheral surface of the workpiece W. Specifically, of the pair of contacts 172a, 172b, one contactor 172a comes into contact with the outer peripheral surface of the workpiece W from above, and the other contactor 172b comes into contact with the outer peripheral surface of the workpiece W from below. The fingers 173a, 173b hold the contactors 172a, 172b and support the contactors 172a, 172b with respect to the device main body 171 so as to be able to move relative to the device main body 171. Specifically, one finger 173a of the pair of fingers 173a, 173b supports one contact 172a, and the other finger 173b supports the other contact 172b.

[0022] The differential transformer 174 is housed in the device main body 171. The differential transformer 174 detects the displacement of the pair of fingers 173a, 173b, which displaces in accordance with the displacement of the pair of contacts 172a, 172b, and outputs an electrical signal corresponding to the displacement of the fingers 173a, 173b to the control device 31. Based on the electrical signal output from the differential transformer 174, the control device 31 detects the positions of the fingers 173a, 173b when the pair of contacts 172a, 172b come into contact with the outer peripheral surface of the workpiece W, and can obtain the measurement result of the outer diameter of the workpiece W obtained by the sizing device 17 based on the positions of the fingers 173a, 173b. Note that the sizing device 17 may be equipped with other detectors, such as an acceleration sensor, a microphone, or a temperature sensor.

[0023] The eddy current sensor 20 functions as a burn occurrence detection unit, and is disposed so that its sensor head faces the processed portion of the workpiece W. In this embodiment 1, as shown in Fig. 3, the sensor head of the eddy current sensor 20 is attached to the device body 171 of the sizing device 17 and is positioned on the opposite side of the grinding wheel 16 with respect to the workpiece W. Note that in Figs. 1 and 3, the reference numeral 20 indicates the position of the sensor head, and the sensor body is not shown.

[0024] The eddy current sensor 20 has a coil (not shown), and when an excitation current is supplied to the coil, the coil applies a magnetic field to the workpiece W, inducing eddy currents inside the workpiece W. The eddy current sensor 20 then outputs a signal representing a change in the impedance of the coil due to the magnetic field created by the eddy current. The magnitude of the eddy current, and therefore the magnitude of the output signal, changes depending on the condition of the workpiece W's workpiece.

[0025] The eddy current sensor 20 is configured to supply multiple excitation currents with different frequencies to the coil. The frequency of the excitation current can be set by a frequency setting unit (not shown). 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 machined 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 magnetic property changes in areas shallow from the machined surface decreases, resulting in reduced detection accuracy.

[0026] 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 20 kHz to 100 kHz, 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.

[0027] In this embodiment, the eddy current sensor 20 is used as the burn occurrence detection unit, but this is not limited to this, and any device that can detect changes in the structure of the processed part can be used as the burn occurrence detection unit instead of the eddy current sensor 20.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The control device 31 grinds the workpiece W by controlling the drive of the grinding wheel 16, the coolant device 19, etc. on the grinding machine 2 based on an NC program generated 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.

[0032] 3. Configuration of coolant flow rate setting device 1 2, the coolant flow rate setting device 1 includes an output signal acquisition unit 40, a dimension information acquisition unit 41, an actual cutting depth calculation unit 42, a grinding efficiency calculation unit 43, a grinding burn occurrence estimation unit 44, a command grinding efficiency calculation unit 45, a coolant flow rate acquisition unit 46, a grinding power acquisition unit 47, a coolant power consumption acquisition unit 48, a burn boundary grinding efficiency evaluation unit 49, a correspondence relationship creation unit 50, a first correspondence relationship storage unit 51, a second correspondence relationship storage unit 52, a third correspondence relationship storage unit 53, a fourth correspondence relationship storage unit 54, a coolant flow rate setting unit 55, a burn depth estimation unit 56, a coolant supply status determination unit 57, a coolant supply status adjustment unit 58, and a sharpness cooling capacity evaluation unit 59, all of which are implemented by a storage device or a computing device. The coolant flow rate setting device 1 also includes a display unit 60, which is a predetermined display device.

[0033] The output signal acquisition unit 40 acquires the output signal P output from the eddy current sensor 20. The output signal P is acquired as an eddy current voltage, as shown in FIG.

[0034] The dimension information acquisition unit 41 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 using 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 31.

[0035] The actual cutting depth calculation unit 42 acquires the cutting depth of the workpiece W per rotation based on the amount of change in the dimensional information of the workpiece W acquired by the dimensional information acquisition unit 41.

[0036] The grinding efficiency calculation unit 43 calculates the grinding efficiency Z' based on the cutting depth per rotation acquired by the actual cutting depth calculation unit 42. The grinding efficiency Z' can be calculated from the rotation speed of the workpiece spindle motor and the actual cutting depth using the following formula (1).

[0037]

number

[0038] The calculation of the grinding efficiency Z' is performed at the rotational speeds of a plurality of workpiece spindles. In the first embodiment, as shown in FIG. 6, the grinding efficiency Z' was calculated for three patterns where the spindle rotational speeds are R1, R2, and R3 (where the relationship R1 < R2 < R3 is satisfied).

[0039] The grinding burn occurrence estimation unit 44 detects a rapid change region Sc where the output signal P acquired by the output signal acquisition unit 40 rapidly changes in a specific section Ts where the grinding efficiency of the grinding machine 2 is continuously changed by the control device 31, and estimates the occurrence of grinding burn in the workpiece portion. The specific section Ts is a section included in the rough grinding process S11 in the grinding process described later. And, as shown in FIG. 5(b), the specific section Ts is a transient response period until the actual depth of cut reaches the commanded depth of cut SA instructed from the control device 31 based on the grinding conditions from the initial value A0 (the state where the grinding wheel 16 and the workpiece W are not in contact). During this period, the actual depth of cut changes so as to continuously increase from the initial value A0 to the commanded depth of cut SA. And, as shown in Equation (1), since the actual depth of cut is proportional to the grinding efficiency Z', in the specific section Ts, 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 depth of cut SA.

[0040] The sudden change region Sc refers to a region in the specific section Ts where the output signal P suddenly changes from its initial value P0. For example, the sudden change region Sc can include the point where the value of the output signal P in the specific section Ts reaches a predetermined reference value Ps. In the first embodiment, as shown in FIG. 5(a), the reference value Ps corresponds to half the maximum change amount Pm, which is the maximum change amount of the output signal P from its initial value P0 in the specific section Ts. When the output signal P reaches the reference value Ps, the actual cutting depth is A and the drive power of the tool spindle is B, as shown in FIG. 5(b). Alternatively, the reference value Ps can be a region where the absolute value of the rate of change of the output signal P in the specific section Ts is greater than a predetermined reference rate of change.

[0041] In the sudden change region Sc, grinding burn occurs in the processed portion due to heat generated by grinding the processed portion of the workpiece W with the grinding wheel 16. 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 accordance with the work-affected layer generated on the workpiece W due to grinding burn, also changes within a short period of time, resulting in a steep change (sudden change) in the output signal. Therefore, the grinding burn occurrence estimation unit 44 can estimate the occurrence of grinding burn in the processed portion by detecting such a sudden change region Sc. Note that a display unit (not shown) for displaying the estimation results may be provided.

[0042] On the other hand, if grinding burn does not occur in the rough grinding process S11, no processing-affected layer due to grinding burn is generated, so the output signal of the eddy current sensor 20 changes gradually and does not exhibit a large change as shown by Pm in Figure 5(a), and therefore the output signal does not pass through the reference value Ps.

[0043] The command grinding efficiency calculation unit 45 shown in Fig. 2 calculates the command grinding efficiency for the grinding machine 2 based on the command cutting depth SA for machining the workpiece W. The command cutting depth SA is set appropriately and can be input by the user. The command grinding efficiency can be calculated from equation (1).

[0044] The coolant flow rate acquisition unit 46 acquires the flow rate of the coolant supplied to the workpiece during machining by the grinding machine 2. The coolant flow rate acquisition unit 46 can be constituted by a predetermined flow meter.

[0045] The grinding power acquisition unit 47 acquires the drive power B of the rotational drive of the tool spindle as the grinding power. The grinding power acquisition unit 47 can be constituted by a predetermined ammeter and voltmeter.

[0046] [[ID=⑧]]The coolant power consumption acquisition unit 48 calculates the coolant power consumption, which is the grinding power consumed by the coolant. The coolant power consumption can be calculated, for example, as the difference between the drive power during the idling of the tool spindle (when the tool is not in contact with the workpiece) in a state where no coolant is supplied and the drive power during the idling of the tool spindle when coolant is supplied during the idling.

[0047] Based on the estimation result of the grinding burn occurrence estimation unit 44, the burn limit grinding efficiency evaluation unit 49 evaluates the burn limit grinding efficiency Z', which indicates the maximum grinding efficiency in the grinding machine 2 within the range where no grinding burn occurs on the workpiece. Note that the grinding efficiency Z' indicates the volume of the workpiece that can be removed per second per unit width (1 mm). As shown in FIG. 7, a plurality of burn limit grinding efficiencies are acquired for each rotational speed of the workpiece spindle. In the first embodiment, as described above, the burn limit grinding efficiency Z' was acquired in three patterns where the rotational speeds of the workpiece spindle are R1, R2, and R3 (where R1 < R2 < R3) with the same tool sharpness. The tool sharpness at this time was set to be in a poor state in all cases. In addition, for the case where the rotational speed of the workpiece spindle is R1, the burn limit grinding efficiency Z' was acquired for both the case of poor tool sharpness and the case of good tool sharpness.

[0048] As shown in Figure 7, at rotational speeds R1, R2, and R3 (filled symbols in Figure 7) compared with the case where the tool was dull, the burnt boundary grinding efficiency Z' has a linear relationship with the rotational speed of the workpiece spindle, and the burnt boundary grinding efficiency Z' increases at a constant rate as the rotational speed of the workpiece spindle 12a increases. Furthermore, when comparing the case where the tool was dull (filled circles) with the case where it was good (open circles) at R1, the burnt boundary grinding efficiency Z' increased when the tool was good, even though the rotational speed of the workpiece spindle 12a was the same. Therefore, when evaluating the burnt boundary grinding efficiency Z', it is preferable to perform the evaluation when the tool was dull.

[0049] As described above, in the specific section Ts where the grinding efficiency Z' continuously changes from the initial value to the target value corresponding to the command cutting-in amount SA, the grinding efficiency Z' is continuously acquired for each of the rotational speed patterns R1, R2, R3 of the workpiece spindle 12a. Therefore, the burnt boundary grinding efficiency Z' for each of the rotational speed patterns R1, R2, R3 of the workpiece spindle 12a can be continuously evaluated, which can be performed with less testing man-hours and with higher accuracy than when performing discrete evaluation.

[0050] The correspondence creating unit 50 creates correspondences to be stored in a first correspondence storage unit 51, a second correspondence storage unit 52, a third correspondence storage unit 53, and a fourth correspondence storage unit 54, which will be described later.

[0051] The first correspondence relationship storage unit 51 stores a grinding efficiency correspondence relationship. The grinding efficiency correspondence relationship is a correspondence relationship between the burn boundary grinding efficiency Z', which indicates the maximum grinding efficiency of the grinding machine 2 within the range where grinding burn does not occur on the workpiece, and the flow rate of the coolant supplied to the workpiece when the burn boundary grinding efficiency Z' is exhibited. In this embodiment, the grinding efficiency correspondence relationship is created by first estimating the occurrence of grinding burn on the workpiece using the grinding burn occurrence estimation unit 44, and then acquiring the burn boundary grinding efficiency Z', which is the maximum grinding efficiency within the range where grinding burn does not occur on the workpiece, using the burn boundary grinding efficiency evaluation unit 49. Next, the coolant flow rate acquisition unit 46 acquires the coolant flow rate when the burn boundary grinding efficiency Z' is exhibited. The coolant flow rate and the burn boundary grinding efficiency Z' are then plotted on a two-dimensional plane as shown in FIG. 8(a), and a reference line indicating the grinding efficiency correspondence relationship is created.

[0052] The grinding efficiency correspondence relationship shown in FIG. 8(a) includes the grinding efficiency Z'a when the coolant flow rate is a first reference flow rate Amin, which is the minimum flow rate required to drive the grinding machine 2, and the maximum burnt boundary grinding efficiency Z', Z'b. The burnt boundary grinding efficiency Z' exhibits its maximum value Z'b when the coolant flow rate is a second reference flow rate Au, which is lower than the maximum flow rate Amax, which is the maximum coolant flow rate in the grinding machine 2. In other words, the second reference flow rate Au is the minimum flow rate at which the burnt boundary grinding efficiency Z' exhibits its maximum value Z'b. Therefore, even if the coolant flow rate is increased beyond the flow rate Au, the cooling effect of the coolant on the workpiece reaches a plateau, and the burnt boundary grinding efficiency does not substantially increase from Z'b.

[0053] The second correspondence relationship storage unit 52 stores a grinding power correspondence relationship. The grinding power correspondence relationship is a correspondence relationship between the burnt boundary power, which is the grinding power required to rotate the tool spindle 16b of the grinding machine 2 when the burnt boundary grinding efficiency Z' is exhibited, and the coolant flow rate supplied to the workpiece when the burnt boundary grinding efficiency Z' is exhibited. In this embodiment, the grinding power correspondence relationship is created by first estimating the occurrence of grinding burn in the workpiece using the grinding burn occurrence estimation unit 44, then acquiring the burnt boundary grinding efficiency Z' using the burnt boundary grinding efficiency evaluation unit 49, and acquiring the grinding power when the burnt boundary grinding efficiency Z' is exhibited using the grinding power acquisition unit 47. Then, acquiring the coolant flow rate when the burnt boundary grinding efficiency Z' is exhibited using the coolant flow rate acquisition unit 46. Next, the grinding power and the coolant flow rate when the burnt boundary grinding efficiency Z' is exhibited are plotted on a two-dimensional plane as shown in FIG. 9(a), and a reference line indicating the grinding power correspondence relationship is created.

[0054] A coolant flow rate / power consumption correspondence relationship is stored in the third correspondence relationship storage unit 53. The coolant flow rate / power consumption correspondence relationship is a correspondence relationship between the flow rate of the coolant supplied to the workpiece when the burnt boundary grinding efficiency Z' is exhibited and the coolant power consumption, which is the grinding power consumed by the coolant when the burnt boundary grinding efficiency Z' is exhibited.

[0055] In this embodiment, the coolant flow rate / power consumption correspondence relationship is created by first estimating the occurrence of grinding burn on the workpiece using the grinding burn occurrence estimation unit 44, then acquiring the burn boundary grinding efficiency Z' using the burn boundary grinding efficiency evaluation unit 49, and then acquiring the coolant flow rate when the burn boundary grinding efficiency Z' is exhibited using the coolant flow rate acquisition unit 46. The coolant power consumption acquisition unit 48 then acquires the grinding power consumed by the coolant supplied to the workpiece when the burn boundary grinding efficiency Z' is exhibited (hereinafter referred to as coolant power consumption) required to rotate the tool spindle of the grinding machine 2. The coolant flow rate and coolant power consumption when the burn boundary grinding efficiency Z' is exhibited are then plotted on a two-dimensional plane as shown in FIG. 10(a), creating a reference line indicating the coolant flow rate / power consumption correspondence relationship.

[0056] In the fourth correspondence relation storage unit 54, a correspondence relation between grinding power and coolant power consumption is stored. The correspondence relation between grinding power and coolant power consumption is a correspondence relation between the grinding power when the burning boundary grinding efficiency Z' is exhibited and the coolant power consumption when the burning boundary grinding efficiency Z' is exhibited.

[0057] In the present embodiment, for creating the correspondence relation between grinding power and coolant power consumption, first, the grinding burn occurrence estimation unit 44 estimates the occurrence of grinding burn in the workpiece, the burning boundary grinding efficiency evaluation unit 49 obtains the burning boundary grinding efficiency Z', and the grinding power acquisition unit 47 obtains the grinding power when the burning boundary grinding efficiency Z' is exhibited. Then, the coolant power consumption acquisition unit 48 obtains the coolant power consumption when the burning boundary grinding efficiency Z' is exhibited. After that, the grinding power and the coolant power consumption when the burning boundary grinding efficiency Z' is exhibited are plotted on a two-dimensional plane as shown in Fig. 11(a), and a reference line indicating the correspondence relation between grinding power and coolant power consumption is created. In Fig. 11(a), the symbol WCLmin indicates the coolant power consumption when the set value of the coolant flow rate is the flow rate Amin, and the symbol WCLu indicates the coolant power consumption when the set value of the coolant flow rate is the flow rate Au.

[0058] 4. Setting of coolant flow rate The coolant flow rate setting unit 55 shown in Fig. 2 sets the flow rate of the coolant supplied to the workpiece based on the commanded grinding efficiency Z'c obtained by the commanded grinding efficiency calculation unit 45 and the grinding efficiency correspondence relation stored in the first correspondence relation storage unit 51. In the present embodiment, in the grinding efficiency correspondence relation shown in Fig. 8(b), when Z'c < Z'a, the coolant flow rate setting unit 55 sets Amin as the coolant flow rate. When Z'a ≤ Z'c ≤ Z'b, the coolant flow rate setting unit 55 sets the flow rate Ac corresponding to the commanded grinding efficiency Z'c in the burning boundary grinding efficiency shown in Fig. 8(b) as the coolant flow rate. When Z'b < Z'c, the coolant flow rate setting unit 55 sets Au as the coolant flow rate. When Z'b < Z'c, the cooling effect of the workpiece by the coolant is insufficient, and burning will occur in the workpiece.

[0059] 5. Estimation of Depth of Grinding Burn The depth of grinding burn estimation unit 56 shown in FIG. 2 estimates the depth of grinding burn when grinding burn occurs in the workpiece portion based on the flow rate of the coolant acquired by the coolant flow rate acquisition unit 46, the grinding power acquired by the grinding power acquisition unit 47, and the grinding power correspondence relationship stored in the second correspondence relationship storage unit 52. In the present embodiment, as described above, when Z'b < Z'c, grinding burn occurs.

[0060] Regarding the cause of the occurrence of the grinding burn state in the workpiece portion Wa when the workpiece portion Wa of the workpiece W is ground by the grinding machine 2, as shown in FIG. 13, in the configuration in which the workpiece portion Wa is ground while supplying the coolant CL to the workpiece portion Wa of the workpiece W, it will be described from the viewpoint of the state change of the coolant supplied to the workpiece portion Wa during machining.

[0061] When the temperature of the workpiece portion Wa rises due to the heat generated in the workpiece portion Wa by the grinding of the workpiece W and reaches the boiling point of the coolant, first, as shown in FIG. 14(a), the coolant CL boils near the surface of the workpiece portion Wa to generate bubbles Bo. In the initial stage of boiling, each bubble Bo is generally independent, and the surface of the workpiece portion Wa is in a state where the liquid-state coolant CL is in contact. This state is called the nucleate boiling state of the coolant CL. In the nucleate boiling state, the cooling performance of the workpiece portion Wa by the coolant CL is maintained, so the workpiece portion Wa is prevented from being overheated, and no grinding burn occurs in the workpiece portion Wa.

[0062] 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 14(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.

[0063] As shown in FIG. 13 , 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 R of the grinding wheel 16. 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, while 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. Even in the case of down-cut grinding, in which the rotational direction R 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.

[0064] In this embodiment, as shown in FIG. 12 , the burn depth estimation unit 56 includes a film boiling boundary power acquisition unit 501, an estimated power calculation unit 502, a contact arc length acquisition unit 503, a contact arc heat flux calculation unit 504, a contact area length calculation unit 505, a heat transfer amount calculation unit 506, a feed rate acquisition unit 507, a fifth correspondence relationship storage unit 508, and a burn depth evaluation unit 509, which are configured by a storage device or a computing device.

[0065] 9(b), the film boiling boundary power acquisition unit 501 acquires the grinding power Z'b, which indicates the burn boundary power, as the film boiling boundary power Q'w. The film boiling boundary power Q'w is the energy required for the coolant supplied to the workpiece to enter a film boiling state when the workpiece is ground by the grinding machine 2, expressed in terms of grinding power. Then, the estimated power calculation unit 502 calculates the estimated power Q' using Q'w, Z'b, and Z'c according to the following relational expression (2).

[0066]

number

[0067] The contact arc length acquisition unit 503 acquires the length Lc of the contact arc LC between the grinding wheel 16 and the workpiece Wa in a cross section (see FIG. 13) perpendicular to the tool spindle 16b. The contact arc LC is a partial arc along the surface of the grinding wheel 16. Note that, since the length Lc of the contact arc LC between the grinding wheel 16 and the workpiece Wa is usually sufficiently small compared to the outer periphery of the grinding wheel 16, the contact arc LC may be approximated to a straight line, and the length Lc may be the length of a line segment. The length Lc can be geometrically calculated based on the dimensional information of the workpiece W acquired by the dimensional information acquisition unit 41, the outer diameter of the grinding wheel 16, and the cutting depth of the workpiece Wa.

[0068] 12 calculates the heat flux q per unit area in the contact arc LC between the grinding wheel 16 and the workpiece Wa. The heat flux q can be calculated from the following relational expression (3) based on the estimated power Q' acquired by the estimated power calculation unit 502 and the length Lc of the contact arc LC acquired by the contact arc length acquisition unit 503.

[0069]

Number

[0070] Based on the estimated power Q', the film boiling boundary power Q'w, and the length Lc of the contact arc LC, the film boiling region length calculation unit 505 calculates the length Lm of the film boiling region LM in the contact arc Lc. The calculation of Lm can be performed based on the following relational expressions (4) and (5).

[0071]

Number

[0072]

Number

[0073] In this embodiment, when calculating the length Lm of the film boiling region LM, it is assumed that Z'b < Z'c and burning occurs on the workpiece Wa. However, when Z'b < Z'c is not satisfied, if the length Lm of the film boiling region LM becomes 0 or less, it can be determined that the film boiling region LM has not occurred and grinding burn has not occurred. If the length Lm of the film boiling region LM is greater than 0, it can be determined that grinding burn has occurred.

[0074] The heat passing amount calculation unit 506 calculates the film boiling region passing heat amount Jm, which is the heat amount generated in the film boiling region LM, which is the region where the coolant CL becomes the film boiling state in the workpiece Wa, based on the estimated power Q' and the film boiling boundary power Q'w. In this embodiment, the calculation of the film boiling region passing heat amount Jm is performed using the following relational expression (6) based on the length Lm of the film boiling region LM shown in FIG. 15, the heat flux q per unit area in the contact arc Lc, and the feed rate v of the workpiece W with respect to the grinding wheel 16, which is a tool provided on the grinding wheel 2. The feed rate v of the workpiece W can be obtained by the feed rate acquisition unit 507 based on the rotation speed of the workpiece motor 12a.

[0075]

number

[0076] The fifth correspondence relationship storage unit 508 stores, as the fifth correspondence relationship, a correspondence relationship between the amount of heat Jm passing through the film boiling region and the depth tb of grinding burn that occurs on the processed portion Wa due to grinding by the grinding machine 2. In this embodiment, the fifth correspondence relationship is a linear relationship between the amount of heat Jm passing through the film boiling region and the depth tb of grinding burn, as shown in Fig. 16, and can be expressed by the relational expression tb = aJm (a is a coefficient). Note that Fig. 16 shows evaluation results when the processing conditions and grinding wheel sharpness shown in Figs. 6 and 7 are changed.

[0077] The burn depth evaluation unit 509 evaluates the grinding burn depth (burn depth) occurring in the processed portion Wa based on the amount of heat Jm passing through the film boiling region and the fifth correspondence relationship stored in the fifth correspondence relationship storage unit 508. In this embodiment, the burn depth D can be derived based on Jm in FIG. 16. The derived burn depth D is displayed on the display unit 60 shown in FIG. 12.

[0078] 6. Determine the coolant supply status The coolant supply status determination unit 57 shown in Figure 2 determines the coolant supply status based on the coolant flow rate / power consumption correspondence relationship stored in the third correspondence relationship memory unit 53, the coolant flow rate acquired by the coolant flow rate acquisition unit 46, and the coolant power consumption acquired by the coolant power consumption acquisition unit 48.

[0079] In this embodiment, as shown by reference symbol WCL1 in FIG. 10(b), if the coolant power consumption when the coolant flow rate is the set flow rate Ac is on the reference line in FIG. 10(b), the coolant supply status is determined to be normal. On the other hand, as shown by reference symbol WCL2, if the acquired coolant flow rate matches the set flow rate Ac but the coolant power consumption is below the reference line, it is determined that a coolant supply abnormality has occurred, causing the coolant flow rate supplied to the workpiece to be less than the set flow rate Ac, and that there is an abnormality in the way the coolant is being applied to the workpiece. Furthermore, as shown by reference symbol WCL3, if the acquired coolant flow rate does not match the set flow rate Ac but is a lower flow rate Ac' and the coolant power consumption is on the reference line at flow rate Ac', it is determined that there is an abnormality in that the coolant is not being supplied at the set flow rate.

[0080] 7.Adjusting the coolant supply 2 adjusts the coolant supply state when the coolant supply state determination unit 57 determines that there is an abnormality in the supply of coolant. In this embodiment, if the coolant supply state determination unit 57 determines that there is an abnormality in the way coolant is being applied to the workpiece, the coolant supply state adjustment unit 58 displays on the display unit 60 a message indicating that the orientation of the coolant nozzle of the coolant device 19 should be changed. The user can adjust the way coolant is being applied to the workpiece by changing the orientation of the coolant nozzle in accordance with this message.

[0081] Furthermore, if the coolant supply state determination unit 57 determines that the coolant flow rate is not being supplied as set, the coolant supply state adjustment unit 58 displays on the display unit 60 a message indicating that the coolant supply path, including the pump, coolant nozzle, etc. of the coolant device 19, should be inspected for abnormalities. In response to this, the user can carry out the inspection. Note that instead of instructing the user to make adjustments, the coolant supply state adjustment unit 58 may be configured to automatically make each adjustment.

[0082] 8.Evaluation of sharpness and cooling capacity The sharpness cooling capacity evaluation unit 59 evaluates the sharpness of the tool provided on the grinding machine 2 and the cooling capacity of the coolant based on the grinding power / coolant power consumption correspondence relationship stored in the fourth correspondence relationship storage unit 54, the grinding power acquired by the grinding power acquisition unit 47, and the coolant power consumption acquired by the coolant power consumption acquisition unit 48. The evaluation results by the sharpness cooling capacity evaluation unit 59 can be displayed on the display unit 60.

[0083] In this embodiment, in the coolant power consumption relative to grinding power shown in FIG. 11(b), when the coolant power consumption is set to WCLc and the grinding power is located on the reference line, as indicated by the symbol W1, the sharpness / cooling capacity evaluation unit 59 evaluates that the tool sharpness is normal and the coolant cooling capacity has not deteriorated. Note that the reference line in FIG. 11(b) was created when the tool sharpness was poor but within the acceptable range, so the case indicated by the symbol W1 can be evaluated as having deteriorated tool sharpness but within the acceptable range. Furthermore, when the coolant power consumption is set to WCLc and the grinding power is located in a region where the power is lower than the reference line, as indicated by the symbol W2 in FIG. 11(b), the sharpness / cooling capacity evaluation unit 59 evaluates that the tool sharpness is good and the coolant cooling capacity has not deteriorated.

[0084] 11(b), when the coolant power consumption is at the set value WCLc and the grinding power is in the region above the reference line, the sharpness and cooling capacity evaluation unit 59 evaluates that the tool sharpness has deteriorated beyond the allowable range and that the coolant cooling capacity has not deteriorated. In this case, it can be assumed that grinding burn has occurred due to the deterioration of the tool sharpness, and a message can be displayed to advise that the tool should be dressed.

[0085] 11(b), when the coolant power consumption is lower than the set value WCLc and the grinding power is equivalent to the grinding power of W1 when the coolant power consumption is the set value WCLc, the sharpness cooling capacity evaluation unit 59 determines that the cooling capacity of the coolant has decreased. In this case, it can be assumed that grinding burn has occurred due to the decrease in the cooling capacity of the coolant, and the display unit 60 can display a message that the coolant device 19 should be adjusted to restore the cooling capacity of the coolant.

[0086] 9. Grinding Process S1 Description The grinding process S1 will be described with reference to Fig. 17. As described above, the grinding process S1 includes a rough grinding step S11, a precision grinding step S12, a fine grinding step S13, and a spark-out step S14. Although not shown, a run-out removal step for the workpiece W is performed as a pre-processing step for the rough grinding step S11. As a result, the processed portion of the workpiece W is centered at the start of the rough grinding step S11.

[0087] In the rough grinding step S11, the control device 31 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 31 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 31 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.

[0088] The cutting depth can be adjusted by controlling the cutting position of the grinding wheel 16 with the control device 31. 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.

[0089] 10. Coolant flow rate setting process S2 Next, the coolant flow rate setting process S2 by the coolant flow rate setting device 1 will be described with reference to the flow chart in Fig. 18. The coolant flow rate setting process S2 is performed in parallel with the grinding process S1. Note that, when performing the coolant flow rate setting process S2 and subsequent processes, it is assumed that the first to fifth correspondence relationship storage units 51 to 54, 508 store the respective correspondence relationships created in advance.

[0090] 18, in the coolant flow rate setting process S2, first, in step S21, the command grinding efficiency calculation unit 45 calculates the command grinding efficiency Z'c based on the command cutting amount SA. Then, in step S22, the coolant flow rate setting unit 55 determines whether the command grinding efficiency Z'c satisfies Z'a≦Z'c≦Z'b.

[0091] In step S22, if the command grinding efficiency Z'c satisfies Z'a≦Z'c≦Z'b, proceed to Yes in step S22, and in step S23, the coolant flow rate setting unit 55 sets the coolant flow rate Ac to a flow rate based on the command grinding efficiency Z'c and the grinding efficiency correspondence relationship (burnt boundary grinding efficiency) stored in the first correspondence relationship memory unit 51, and then the flow is terminated.

[0092] On the other hand, in step S22, when the commanded grinding efficiency Z'c does not satisfy Z'a ≤ Z'c ≤ Z'b, proceed to No in step S22. In step S24, determine whether Z'c < Z'a by the coolant flow rate setting unit 55. In step S24, if Z'c < Z'a is satisfied, proceed to Yes in step S24. In step S25, set the coolant flow rate Ac to the minimum flow rate Amin by the coolant flow rate setting unit 55 and end the flow.

[0093] Also, in step S24, if Z'c < Z'a is not satisfied, proceed to No in step S24. In step S26, determine that Z'b < Z'c by the coolant flow rate setting unit 55 and set the coolant flow rate Ac to the flow rate Au and end the flow.

[0094] 11. Burn evaluation process S3 Next, the burn evaluation process S3 will be described with reference to the flowchart of FIG. 19. First, in step S31, determine whether Z'b < Z'c by the burn depth estimation unit 56. If it is determined that Z'b < Z'c, proceed to Yes in step S31. In step S32, evaluate that grinding burn has occurred in the workpiece.

[0095] Thereafter, in step S33, obtain Z'b as the film boiling boundary power Q'w by the film boiling boundary power acquisition unit 501. Further, in step S34, calculate Q' based on the above relational expression (2) by the estimated power calculation unit 502. Next, in step S35, obtain the length Lc of the contact arc LC between the grinding wheel 16 and the workpiece Wa by the contact arc length acquisition unit 503. Then, in step S36, calculate the heat flux q per unit area in the contact arc LC between the grinding wheel 16 and the workpiece Wa based on the above relational expression (3) by the contact arc heat flux calculation unit 504.

[0096] Then, in step S37, based on the above relational expressions (4) and (5), the film boiling region length calculation unit 505 calculates the length Lm of the film boiling region LM in the contact arc Lc based on the estimated power Q', the film boiling boundary power Q'w, and the length Lc of the contact arc LC. Next, in step S38, the heat passing amount calculation unit 506 calculates the heat passing amount Jm in the film boiling region using the above relational expression (6) based on the length Lm of the film boiling region LM, the heat flux q, and the feed rate v of the workpiece W with respect to the grinding wheel 16.

[0097] Thereafter, in step S39, based on the heat passing amount Jm in the film boiling region and the fifth correspondence relationship stored in the fifth correspondence relationship storage unit 508, the grinding burn depth (burn depth D) generated in the machined portion Wa is calculated by the burn depth evaluation unit 509, and the flow is terminated. On the other hand, in step S31, when it is determined by the burn depth estimation unit 56 that Z'b < Z'c does not hold, the process proceeds to No in step S31, and in step S40, the burn depth estimation unit 56 evaluates that no grinding burn has occurred in the machined portion and terminates the flow.

[0098] Note that when it is determined by the burn depth evaluation unit 509 that grinding burn has occurred, the commanded depth of cut SA may be adjusted so as to reduce the grinding efficiency.

[0099] 12. Coolant Abnormality Judgment Process S4 Next, the coolant abnormality judgment process S4 will be described with reference to the flowchart of FIG. 20. First, in step S41, the coolant flow rate acquisition unit 46 acquires the current coolant flow rate. Then, in step S42, the coolant supply state judgment unit 57 determines whether the current coolant flow rate matches the set value set by the coolant flow rate setting unit 55.

[0100] If the coolant supply state determination unit 57 determines in step S42 that the current coolant flow rate does not match the set value, the process proceeds to No in step S42, and in step S43 it is determined that there is an abnormality in the coolant supply. Then, in step S44, the display unit 60 displays a message indicating that an inspection of the coolant supply path including the coolant device 19 will be performed, and the flow ends.

[0101] On the other hand, if the coolant supply state determination unit 57 determines in step S42 that the current coolant flow rate matches the set value, the process proceeds to Yes in step S42, and in step S45 the coolant power consumption acquisition unit 48 acquires the current coolant power consumption. Then, in step S46, the coolant supply state determination unit 57 determines whether the current coolant power consumption matches the coolant power consumption corresponding to the set value of the coolant flow rate in the coolant flow rate-power consumption correspondence relationship stored in the third correspondence relationship storage unit 53.

[0102] If it is determined in step S46 that the current coolant power consumption does not match the coolant power consumption corresponding to the set value, the process proceeds to No in step S46, and it is determined in step S47 that there is an abnormality in the coolant supply. Then, in step S48, a message is displayed on the display unit 60 indicating that the coolant application method should be adjusted, and the flow ends.

[0103] On the other hand, if it is determined in step S46 that the current coolant power consumption matches the coolant power consumption corresponding to the set value, the process proceeds to Yes in step S46, and in step S49 it is determined that there is no abnormality in the coolant supply, and this is displayed on the display unit 60, and the flow ends.

[0104] 13. Sharpness and cooling capacity judgment process S5 Next, the sharpness cooling capacity determination process S5 will be described with reference to the flowchart in Fig. 21. First, in step S51, the current coolant power consumption is obtained by the coolant power consumption acquisition unit 48. Then, in step S52, the sharpness cooling capacity evaluation unit 59 determines whether the current coolant power consumption matches the coolant power consumption corresponding to the set value of the coolant flow rate in the grinding power / coolant power consumption correspondence relationship stored in the fourth correspondence relationship storage unit 54.

[0105] If it is determined in step S52 that the current coolant power consumption does not match the coolant power consumption corresponding to the set value, the process proceeds to No in step S52, and in step S53, the sharpness cooling capacity evaluation unit 59 determines that the cooling capacity of the coolant has decreased, displays this information on the display unit 60, and ends the flow.

[0106] On the other hand, if it is determined in step S52 that the current coolant power consumption matches the coolant power consumption corresponding to the set value, the process proceeds to Yes in step S52. Then, in step S54, the sharpness cooling capacity evaluation unit 59 determines whether the current grinding power acquired by the grinding power acquisition unit 47 exceeds the burn limit grinding power in the grinding power-coolant power consumption correspondence relationship stored in the fourth correspondence relationship storage unit 54.

[0107] If it is determined in step S54 that the current grinding power exceeds the burn limit grinding power, the process proceeds to Yes in step S54, and in step S55 the sharpness cooling capacity evaluation unit 59 determines that the sharpness of the grinding wheel 16 has deteriorated beyond the allowable range, displays this fact on the display unit 60, and the process ends. On the other hand, if it is determined in step S54 that the current grinding power does not exceed the burn limit grinding power, the process proceeds to No in step S54, and in step S56 the sharpness cooling capacity evaluation unit 59 determines that the sharpness of the grinding wheel 16 is within the allowable range, displays this fact on the display unit 60, and the process ends.

[0108] 14. Action and Effects According to the coolant flow rate setting device 1 of this embodiment, the flow rate of the coolant supplied to the workpiece is set based on the grinding efficiency correspondence relationship, which is the correspondence relationship between the burn boundary grinding efficiency Z', which indicates the maximum grinding efficiency within the range where grinding burn does not occur on the workpiece, and the coolant flow rate supplied to the workpiece when burn boundary grinding efficiency Z' is exhibited. This allows the coolant flow rate to be optimized, preventing grinding burn, suppressing increases in power consumption, and improving machining accuracy.

[0109] In this embodiment, the coolant flow rate setting unit 55 sets the coolant flow rate required to prevent grinding burns from occurring on the workpiece based on the command grinding efficiency Z'c and the grinding efficiency correspondence relationship, thereby further optimizing the coolant flow rate.

[0110] In this embodiment, the first correspondence relationship storage unit 51 stores a first reference flow rate Amin, which is the minimum coolant flow rate required for grinding in the grinding machine 2, and a second reference flow rate Au, which is the minimum flow rate when the burnt boundary grinding efficiency Z' is at its maximum. The coolant flow rate setting unit 55 sets the first reference flow rate Amin as the coolant flow rate when the coolant flow rate derived based on the command grinding efficiency Z'c is smaller than the first reference flow rate Amin, and sets the second reference flow rate Au as the coolant flow rate when the coolant flow rate derived based on the command grinding efficiency Z'c is larger than the second reference flow rate Au. This ensures the minimum necessary coolant flow rate and prevents unnecessary coolant supply.

[0111] The present embodiment further includes a second correspondence relationship storage unit 52 that stores a grinding power correspondence relationship between the burn boundary power, which is the grinding power required to rotate the tool spindle 16b of the grinding machine 2 when the burn boundary grinding efficiency Z' is exhibited, and the flow rate of coolant supplied to the workpiece when the burn boundary grinding efficiency Z' is exhibited; a coolant flow rate acquisition unit 46 that acquires the flow rate of coolant supplied to the workpiece during machining by the grinding machine 2; a grinding power acquisition unit 47 that acquires the grinding power during machining by the grinding machine 2; and a burn depth estimation unit 56 that estimates the depth of grinding burn when grinding burn occurs on the workpiece based on the coolant flow rate acquired by the coolant flow rate acquisition unit 46, the grinding power acquired by the grinding power acquisition unit 47, and the grinding power correspondence relationship. This allows the depth of grinding burn to be estimated with higher accuracy.

[0112] In this embodiment, the burn depth estimation unit 56 includes a film boiling boundary power acquisition unit 501 that acquires the maximum value Z'b of the burn boundary power as the film boiling boundary power Q'w, which is the energy required for the coolant supplied to the workpiece to enter a film boiling state when the workpiece is ground by the grinding machine 2, and a burn depth evaluation unit 509 that evaluates the depth D of grinding burn generated in the workpiece based on the command grinding efficiency Z'c, the maximum value Z'b of the burn boundary grinding efficiency Z', and the film boiling boundary power Q'w when the command grinding efficiency Z'c calculated by the command grinding efficiency calculation unit 45 exceeds the maximum value Z'b of the burn boundary grinding efficiency Z'. This makes it possible to evaluate the depth D of grinding burn generated in the workpiece with high accuracy.

[0113] The present embodiment further includes a third correspondence relationship storage unit 53 that stores a coolant flow rate / power consumption correspondence relationship, which is a correspondence relationship between the coolant flow rate supplied to the workpiece when the burnt boundary grinding efficiency Z' is exhibited and the coolant power consumption, which is the grinding power consumed by the coolant to rotate and drive the tool spindle of the grinding machine 2 when the burnt boundary grinding efficiency Z' is exhibited; a coolant flow rate acquisition unit 46 that acquires the coolant flow rate supplied to the workpiece during machining by the grinding machine 2; a coolant power consumption acquisition unit 48 that acquires the coolant power consumption, which is the grinding power consumed by the coolant; and a coolant supply status determination unit 57 that determines the coolant supply status based on the coolant power consumption correspondence relationship, the coolant flow rate acquired by the coolant flow rate acquisition unit 46, and the coolant power consumption acquired by the coolant power consumption acquisition unit 48. This makes it easy to grasp the coolant supply status.

[0114] Furthermore, this embodiment includes a coolant supply state adjustment unit 58 that adjusts the coolant supply state when the coolant supply state determination unit 57 determines that the coolant supply is abnormal. This allows the coolant supply state to be adjusted in response to the abnormality in the coolant supply.

[0115] In addition, this embodiment is equipped with a fourth correspondence relationship memory unit 54 that stores a grinding power / coolant power consumption correspondence relationship, which is the correspondence relationship between the grinding power required to rotate the tool spindle 16b of the grinding machine 2 when the burnt boundary grinding efficiency Z' is exhibited and the coolant power consumption, which is the grinding power consumed by the coolant that was supplied when the burnt boundary grinding efficiency Z' is exhibited; a grinding power acquisition unit 47 that acquires the grinding power required to rotate the tool spindle 16b of the grinding machine 2 when grinding burn occurs on the workpiece; a coolant power consumption acquisition unit 48 that acquires the coolant power consumption, which is the grinding power consumed by the coolant; and a sharpness / coolant power evaluation unit 59 that evaluates the sharpness of the grinding wheel 16, which is a tool provided on the grinding machine 2, and the cooling capacity of the coolant based on the grinding power / coolant power consumption correspondence relationship, the grinding power acquired by the grinding power acquisition unit 47, and the coolant power consumption acquired by the coolant power consumption acquisition unit 48. This allows the sharpness of the grinding wheel 16 and the cooling capacity of the coolant to be evaluated with high precision.

[0116] As described above, according to the above aspect, a coolant flow rate setting device 1 can be provided that sets the flow rate of coolant to prevent grinding burns, suppress increases in power consumption, and improve processing accuracy during processing using a grinding machine 2.

[0117] 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]

[0118] 1 Coolant flow setting device 2 Grinding machines 3 Processing section 12a Workpiece motor 16 Grinding Wheel (Tool) 16a Tool spindle motor 16b Tool spindle 17 Sizing device 19 Coolant unit 20 Eddy current sensor 31 Control device 43 Grinding efficiency calculation section 44 Grinding burn occurrence area 45 Command grinding efficiency calculation section 46 Coolant flow rate acquisition unit 47 Grinding power acquisition unit 48 Coolant power consumption acquisition unit 49 Burnt boundary grinding efficiency evaluation section 50 Correspondence creation section 51 First correspondence relationship storage unit 52 Second correspondence relationship storage unit 53 Third correspondence relationship storage unit 54 Fourth correspondence relationship storage unit 55 Coolant flow rate setting section 56 Burn depth estimation unit 57 Coolant supply status determination unit 58 Coolant supply condition adjustment unit 59 Sharpness and Cooling Capacity Evaluation Section 60 Display

Claims

1. 1. A coolant flow rate setting device for setting a flow rate of a coolant in a grinding machine that grinds a processed portion of a workpiece into a final target shape while supplying the coolant to the processed portion, a first correspondence relationship storage unit that stores a grinding efficiency correspondence relationship, which is a correspondence relationship between a burnt boundary grinding efficiency that indicates the maximum grinding efficiency of the grinding machine within a range in which grinding burn does not occur on the processed part, and a flow rate of coolant that was supplied to the processed part when the burnt boundary grinding efficiency was exhibited; a command grinding efficiency calculation unit that calculates a command grinding efficiency for the grinding machine based on a command value for machining the workpiece; a coolant flow rate setting unit that sets the flow rate of the coolant to be supplied to the workpiece based on the command grinding efficiency acquired by the command grinding efficiency calculation unit and the grinding efficiency correspondence relationship; A coolant flow rate setting device comprising:

2. 2. The coolant flow rate setting device according to claim 1, wherein the coolant flow rate setting unit sets the flow rate of the coolant required to prevent grinding burns from occurring on the workpiece, based on the command grinding efficiency and the grinding efficiency correspondence relationship.

3. the first correspondence relationship storage unit stores a first reference flow rate, which is a minimum flow rate of the coolant required for grinding in the grinding machine, and a second reference flow rate, which is a minimum flow rate when the burnt boundary grinding efficiency exhibits a maximum value; 3. The coolant flow rate setting device according to claim 2, wherein the coolant flow rate setting unit sets the first reference flow rate as the coolant flow rate when the coolant flow rate derived based on the command grinding efficiency is smaller than the first reference flow rate, and sets the second reference flow rate as the coolant flow rate when the coolant flow rate derived based on the command grinding efficiency is larger than the second reference flow rate.

4. a second correspondence relationship storage unit that stores a grinding power correspondence relationship that is a correspondence relationship between burnt boundary power, which is grinding power required to rotate and drive a tool spindle of the grinding machine when the burnt boundary grinding efficiency is exhibited, and a flow rate of coolant supplied to the workpiece when the burnt boundary grinding efficiency is exhibited; a coolant flow rate acquisition unit that acquires a flow rate of the coolant supplied to the workpiece during processing by the grinding machine; a grinding power acquisition unit that acquires the grinding power during processing by the grinding machine; 4. The coolant flow rate setting device according to claim 1, further comprising: a burn depth estimation unit that estimates the depth of grinding burn when grinding burn occurs on the workpiece, based on the flow rate of the coolant acquired by the coolant flow rate acquisition unit, the grinding power acquired by the grinding power acquisition unit, and the grinding power correspondence relationship.

5. The burn depth estimation unit a film boiling boundary power acquiring unit that acquires the maximum value of the burnt boundary power as film boiling boundary power, which is energy required for the coolant supplied to the workpiece to reach a film boiling state when the workpiece is ground by the grinding machine; a burn depth evaluation unit that evaluates the depth of grinding burn generated in the workpiece based on the command grinding efficiency, the maximum value of the burn boundary grinding efficiency, and the film boiling boundary power when the command grinding efficiency calculated by the command grinding efficiency calculation unit exceeds the maximum value of the burn boundary grinding efficiency.

6. a third correspondence relationship storage unit that stores a coolant flow rate / power consumption correspondence relationship, which is a correspondence relationship between a flow rate of the coolant supplied to the workpiece when the burnt boundary grinding efficiency is exhibited and a coolant power consumption that is a grinding power required to rotate and drive a tool spindle of the grinding machine consumed by the coolant when the burnt boundary grinding efficiency is exhibited; a coolant flow rate acquisition unit that acquires a flow rate of the coolant supplied to the workpiece during processing by the grinding machine; a coolant power consumption acquisition unit that acquires coolant power consumption, which is the grinding power consumed by the coolant; A coolant flow rate setting device as described in any one of claims 1 to 3, comprising a coolant supply state determination unit that determines the supply state of the coolant based on the coolant flow rate / power consumption correspondence relationship, the coolant flow rate acquired by the coolant flow rate acquisition unit, and the coolant power consumption calculated by the coolant power consumption acquisition unit.

7. 7. The coolant flow rate setting device according to claim 6, further comprising a coolant supply state adjusting unit that adjusts the supply state of the coolant when the coolant supply state determining unit determines that the supply of the coolant is abnormal.

8. a fourth correspondence relationship storage unit that stores a grinding power / coolant power consumption correspondence relationship, which is a correspondence relationship between grinding power required to rotate and drive a tool spindle of the grinding machine when the burnt boundary grinding efficiency is exhibited and coolant power consumption, which is grinding power consumed by the coolant supplied when the burnt boundary grinding efficiency is exhibited; a grinding power acquisition unit that acquires grinding power required to rotate a tool spindle of the grinding machine when grinding burn occurs on the workpiece; a coolant power consumption acquisition unit that acquires coolant power consumption, which is grinding power consumed by the coolant; 4. The coolant flow rate setting device according to claim 1, further comprising: a sharpness / cooling capacity evaluation unit that evaluates the sharpness of a tool provided on the grinding machine and the cooling capacity of the coolant based on the grinding power / coolant power consumption correspondence relationship, the grinding power acquired by the grinding power acquisition unit, and the coolant power consumption calculated by the coolant power consumption acquisition unit.

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