Cooling capacity evaluation device and grinding burning state evaluation system

Abstract

To provide a cooling capacity evaluation device which can evaluate the cooling capacity of a coolant against grinding heat generated in a processing target part by grinding.SOLUTION: A cooling capacity evaluation device 3b, which evaluates a cooling capacity in a processing target part of a workpiece ground while supplying a cooling liquid by a grinder, comprises: a first estimation part 81 for estimating a transformation point temperature of the processing target part and a cooling time required for a tissue of the processing target part having reached the transformation point temperature to turn into a tissue providing a grinding burning; a second estimation part 82 for estimating temperature transition at a depth position of the grinding burning generated in the processing target part from the transformation point temperature, the cooling time, and a processing condition; a burning depth acquisition part 80 for acquiring the burning depth; a calorific power estimation part 85 for estimating a calorific power generated in the processing target part by grinding on the basis of the processing condition or grind energy required for grinding the processing target part; and a cooling volume estimation part 86 for estimating a cooling volume of the processing target part by the cooling liquid on the basis of the burning depth, the calorific power, and the temperature transition estimated by the second estimation part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a cooling capacity evaluation device and a grinding burn state evaluation system. [Background technology]

[0002] Conventionally, when grinding a workpiece, the temperature of the workpiece's surface tends to become high, which can lead to grinding burns on the workpiece's surface depending on the processing conditions. Grinding burns are undesirable because they can reduce the mechanical strength of the workpiece. One possible way to prevent grinding burns is to reduce the tool rotation speed and tool feed rate to make the processing conditions gentler, but this reduces processing efficiency. Therefore, for example, the configuration disclosed in Patent Document 1 improves processing efficiency while preventing grinding burns by supplying a coolant to the workpiece during grinding and optimizing the operating conditions of the grinding wheel and workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-83049 Summary of the Invention [Problem to be solved by the invention]

[0004] The configuration disclosed in Patent Document 1 ensures sufficient cooling by supplying a large amount of coolant to prevent overheating of the workpiece. However, excessive supply of coolant can increase power loss and consumption, which is undesirable from the perspectives of energy consumption and environmental impact. Furthermore, excessive supply of coolant increases dynamic pressure and increases deflection of the workpiece, necessitating an increased tool feed rate to machine the workpiece to the desired shape, resulting in an increase in cycle time. Meanwhile, an insufficient supply of coolant makes it difficult to prevent grinding burn. Therefore, there is a need to optimize the amount of coolant supplied.

[0005] However, in order to optimize the amount of coolant supplied, it is necessary to properly evaluate the cooling capacity of the coolant against the grinding heat generated in the workpiece during grinding. However, since the ratio of the cooling heat generated by the coolant to the grinding heat is not determined, it is difficult to optimize the amount of coolant supplied.

[0006] The present invention provides a cooling capacity evaluation device capable of evaluating the cooling capacity of a coolant for the grinding heat generated in a workpiece during grinding. [Means for solving the problem]

[0007] One aspect of the present invention is A cooling capacity evaluation device for evaluating the cooling capacity of a processed portion of a workpiece that is ground by a grinding machine while supplying a coolant, comprising: a first estimation unit that estimates a transformation point temperature of the processed part and a cooling time required for the structure of the processed part that has reached the transformation point temperature to change into a structure that exhibits grinding burn; a second estimation unit that estimates a temperature transition at a depth position of grinding burn occurring in the processed portion based on the transformation point temperature, the cooling time, and the processing conditions of the workpiece; a burn depth acquisition unit that acquires a burn depth, which is the depth of grinding burn occurring on the processed portion; a heat generation amount estimation unit that estimates a heat generation amount generated in the processed portion by grinding based on the processing conditions of the workpiece or grinding power, which is power required to grind the processed portion by the grinding machine; a cooling amount estimation unit that estimates a cooling amount of the workpiece by the coolant based on the burn depth, the heat generation amount, and the temperature transition estimated by the second estimation unit; The cooling capacity evaluation device includes: [Effects of the Invention]

[0008] According to the above aspect, the temperature transition at the depth position of the grinding burn (i.e., the position of the boundary surface between the area where grinding burn has occurred and the area where grinding burn has not occurred) is estimated from the transformation point temperature of the processed part, the cooling time required for the structure of the processed part that has reached the transformation point temperature to change into a structure that exhibits grinding burn, and the processing conditions of the workpiece, and the amount of cooling of the processed part by the coolant can be estimated from the temperature transition, the amount of heat generated in the processed part, and the burn depth, thereby making it possible to quantify and evaluate the cooling capacity of the coolant.

[0009] As described above, according to the above aspect, it is possible to provide a cooling capacity evaluation device that can evaluate the cooling capacity of a coolant for the grinding heat generated in a workpiece during grinding. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram showing the configuration of a grinding burn state evaluation system according to a first embodiment. [Figure 2] FIG. 1 is a functional block diagram showing the configuration of a grinding burn state evaluation system according to a first embodiment. [Figure 3] FIG. 1 is a functional block diagram showing the configuration of a cooling capacity evaluation device according to a first embodiment. [Figure 4] FIG. 2 is a diagram showing the vicinity of a sizing device equipped with an eddy current sensor in the first embodiment. [Figure 5] 3 is an enlarged cross-sectional view of the periphery of a processed portion in the first embodiment. [Figure 6] 4 is an enlarged cross-sectional view of the cooling liquid in a nucleate boiling state according to the first embodiment; FIG. [Figure 7] FIG. 3 is a conceptual diagram showing a first correspondence relationship in the first embodiment. [Figure 8] FIG. 2 is a diagram showing an example of a CCT diagram in the first embodiment. [Figure 9] 1A is a conceptual diagram showing the position of the burn depth, and FIG. 1B is a diagram showing the temperature transition estimated by the second estimation unit in the first embodiment. [Figure 10] FIG. 10 is a diagram showing a temperature transition estimated by a second estimation unit and a temperature transition when the cooling amount is changed in the first embodiment. [Figure 11] FIG. 3 is a conceptual diagram showing the configuration of a first correspondence relationship creating unit in the first embodiment. [Figure 12] FIG. 3 is a diagram showing an output signal of an eddy current sensor in the first embodiment. [Figure 13] FIG. 4 is a diagram showing the correspondence relationship between the actual cutting depth and grinding efficiency in the first embodiment. [Figure 14] 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 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] FIG. 4 is a conceptual diagram showing a second correspondence relationship in the first embodiment. [Figure 17] FIG. 3 is a conceptual diagram showing the configuration of a second correspondence relationship creating unit in the first embodiment. [Figure 18] FIG. 2 is a diagram for explaining an outline of synchronous detection in the eddy current sensor according to the first embodiment. [Figure 19] FIG. 1A is a diagram showing the relationship between time and the output signal of an eddy current sensor that serves as the first inflection point determination criterion in embodiment 1; and FIG. 1B is a diagram showing the output signal of an eddy current sensor that serves as the first inflection point determination criterion in the complex plane. [Figure 20] FIG. 1A is a diagram showing the relationship between time and the output signal of an eddy current sensor that serves as a second inflection point determination criterion in embodiment 1; FIG. 1B is a diagram showing the output signal of an eddy current sensor that serves as a second inflection point determination criterion, expressed on a complex plane. [Figure 21] 4 is a diagram showing the change over time in dimensional information of a workpiece and the burn depth in the first embodiment. FIG. [Figure 22] FIG. 2 is a flowchart of a grinding process in the first embodiment. [Figure 23] FIG. 3 is a flowchart of a cooling capacity evaluation process according to the first embodiment. [Figure 24] FIG. 4 is a flowchart of a coolant flow rate optimization process according to the first embodiment. [Figure 25] FIG. 3 is a flowchart of processing condition optimization processing in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1) 1. Configuration of Grinding Burn Condition Evaluation System 1 The grinding burn state evaluation system 1 of the first embodiment includes a grinding machine 2 as a processing device and a processing section 3, and evaluates the grinding burn state of a workpiece W ground by the grinding machine 2.

[0012] In the first embodiment, as shown in FIG. 1 , the grinding machine 2 rotates the workpiece W about a center line C, rotates a grinding wheel 16 as a tool that is a rotating body, and moves the grinding wheel 16 relatively close to the workpiece W in a direction intersecting the axis of the workpiece W, thereby grinding the outer or inner peripheral surface of the workpiece W. The 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. The relationship between the rotation direction of the workpiece W and the rotation direction of the grinding wheel 16 may be either an up-cut or a down-cut relationship.

[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 grinding burn state evaluation device 3a, a cooling capacity evaluation device 3b, and a control device 3c that controls the grinding machine 2. As will be described later, the grinding burn state evaluation device 3a evaluates the grinding burn state, including the burn depth caused by grinding on the workpiece W. The cooling capacity evaluation device 3b evaluates the cooling capacity of the coolant for the processed portion of the workpiece. The control device 3c controls the grinding process by controlling the grinding machine 2.

[0016] The grinding burn condition evaluation device 3a and the cooling capacity evaluation device 3b can function as simulation devices independent of the grinding machine 2 and the control device 3c, or as simulation devices operating in conjunction with the grinding machine 2 and the control device 3c. In the former case, the grinding burn condition evaluation device 3a and the cooling capacity evaluation device 3b can, for example, evaluate the burn condition and the cooling capacity without actually grinding the workpiece W. In the latter case, the grinding burn condition evaluation device 3a and the cooling capacity evaluation device 3b can, for example, determine the presence or absence of grinding burn, adjust grinding conditions, and operate to affect various controls by processing in parallel with the grinding of the workpiece W by the grinding machine 2. The grinding burn condition evaluation device 3a and the cooling capacity evaluation device 3b can also be incorporated into the grinding machine 2 and the control device 3c.

[0017] 2. Configuration of the grinding machine 2 and the control device 3c 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 supply 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 (lower side in FIG. 1) and on one end side in the Z-axis direction (left side in FIG. 1). The headstock 12 supports the workpiece W rotatably around the Z-axis with the center line C of the workpiece W as the center. The workpiece W is rotated by driving a workpiece motor 12a provided on the headstock 12. The tailstock 13 is provided on the upper surface of the bed 11, in a position facing the headstock 12 in the Z-axis direction, i.e., on the near side in the X-axis direction (lower side in FIG. 1) and on the other end side in the Z-axis direction (right side in FIG. 1). In other words, the headstock 12 and 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 traverse base motor 15a provided on the traverse base 14. The grinding wheel 16 is connected to 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] 4, 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 3c. The control device 3c 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 based on the electrical signal output from the differential transformer 174, and can obtain the measurement result of the outer diameter of the workpiece W 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 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.

[0024] 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.

[0025] The coolant supply device 19 supplies coolant from the coolant nozzle to the portion Wa of the workpiece W being machined by the grinding wheel 16. The coolant supply device 19 cools the collected coolant to a predetermined temperature and supplies it again to the portion Wa being machined. The coolant supply device 19 is capable of adjusting the flow rate and supply timing of the coolant using a coolant supply amount optimization unit 90 (see FIG. 3), which will be described later. In FIG. 1, reference numeral 19 indicates the position of the coolant nozzle. Also, as shown in FIG. 2, a thermometer 191 that acquires the temperature of the collected coolant and a flow meter 192 that detects the flow rate of the coolant are provided as detectors.

[0026] The control device 3c grinds the workpiece W by controlling the driving of the grinding wheel 16, the coolant supply device 19, etc. of 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, the cooling capacity of the coolant, and information on the flow rate or supply timing of the coolant. In particular, the control device 3c grinds the workpiece W until it reaches the finished shape (target shape) based on the processing conditions adjusted by a processing condition adjustment unit 91 (described later) and the diameter of the workpiece W measured by a sizing device 17. Furthermore, the control device 3c performs correction (truing and dressing) of the grinding wheel 16 by controlling the grinding wheel correction device 18, etc., at the timing to correct the grinding wheel 16.

[0027] 3. Grinding burns occurring on the processed part Wa of the workpiece W Next, the cause of grinding burn occurring on the processed portion Wa of the workpiece W when the processed portion Wa is ground using the grinding machine 2 will be explained from the perspective of the change in the state of the coolant supplied to the processed portion Wa during processing in a configuration in which the processed portion Wa of the workpiece W is ground while supplying coolant CL to the workpiece W, as shown in Figure 5.

[0028] When the workpiece W is ground, the heat generated in the workpiece Wa raises the temperature of the workpiece Wa and reaches the boiling point of the coolant. As shown in Figure 6(a), the coolant CL first boils near the surface of the workpiece Wa, forming bubbles Bo. In the early stages of boiling, each bubble Bo is largely independent, and the coolant CL in liquid form is in contact with the surface of the workpiece Wa. This state is called the nucleate boiling state of the coolant CL. In the nucleate boiling state, the coolant CL maintains its cooling performance for the workpiece Wa, preventing the workpiece Wa from overheating and preventing grinding burns from occurring on the workpiece Wa.

[0029] 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 6(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.

[0030] As shown in FIG. 5, 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.

[0031] 4. Cooling capacity evaluation device 3b 3, the cooling capacity evaluation device 3b includes a burnt depth acquisition unit 80, a first estimation unit 81, a second estimation unit 82, a CCT diagram storage unit 83, a temperature transition storage unit 84, a heat generation amount estimation unit 85, a cooling amount estimation unit 86, a cooling amount estimation model storage unit 87, a burnt depth allowance calculation unit 88, a final state evaluation unit 89, a coolant supply amount optimization unit 90, and a processing condition adjustment unit 91. These are configured as storage devices or arithmetic units. Each component will be described in detail below.

[0032] 4-1. Burn depth acquisition unit 80 The burn depth acquisition unit 80 shown in Fig. 3 acquires, as grinding burn information, burn depth x, which is the depth of grinding burn that occurs in the processed portion of the workpiece due to grinding. If there is variation in burn depth x, the maximum burn depth x is acquired. In this embodiment, the burn depth x that occurs in the processed portion Wa is acquired from the evaluation results by the grinding burn state evaluation device 3a, which will be described later. Alternatively, the burn depth x may be acquired by conducting a corrosion test.

[0033] 4-2.First estimation part 81 The first estimation unit 81 shown in Fig. 3 estimates the transformation point temperature T of the workpiece Wa and the cooling time t required for the structure of the workpiece Wa, which has reached the transformation point temperature, to change into a structure that exhibits grinding burn. The transformation point temperature T of the workpiece Wa is determined based on the material constituting the workpiece W. In this embodiment, the workpiece W is eutectoid steel (Fe-0.8C), and the transformation point temperature is the temperature of the A1 transformation point. That is, the first estimation unit 81 estimates the transformation point temperature T as approximately 723°C, which is the A1 transformation point temperature of eutectoid steel.

[0034] As shown in the CCT diagram of eutectoid steel (Fe-0.8C) in Figure 8, eutectoid steel transforms into an austenite structure when heated above the A1 transformation temperature. Subsequently, when cooled at a cooling rate equal to or greater than the upper critical cooling rate of 140°C / s, the structure transforms into martensite. When cooled at a cooling rate less than the upper critical cooling rate, the structure transforms into a structure containing pearlite and martensite. This martensite-only structure exhibits grinding burn. Therefore, the first estimation unit 81 estimates the cooling time t, which is the cooling time required for the phase transformation into a structure containing pearlite, i.e., the time t required to reach room temperature after cooling at the upper critical cooling rate shown in the CCT diagram. Because grinding involves rapid cooling after grinding, the transformation temperature T is used to estimate the cooling time t as the representative temperature of the workpiece Wa. The CCT diagram shown in Figure 8 was taken from "Fundamental Creation Engineering," a lecture material for Kyoto University, by Nobuyasu Tsuji (2008). The information relating to the CCT diagram is assumed to be stored in advance in the CCT diagram storage unit 83 shown in FIG.

[0035] 4-3.Second estimation part 82 The second estimation unit 82 shown in FIG. 3 estimates the temperature transition at the position of the grinding burn depth x occurring in the processed portion Wa (i.e., the position of the boundary surface between the area where grinding burn occurs and the area where grinding burn does not occur as shown in FIG. 9(a)) based on the transformation temperature T, the cooling time t, and the processing conditions of the workpiece W. The temperature transition is expressed, for example, as shown in FIG. 9(b), as a temperature transition having the transformation temperature T near the temperature peak and cooling to room temperature over the cooling time t. The temperature transition up to the temperature peak is expressed based on the workpiece removal rate calculated from the grinding wheel feed rate, workpiece diameter, and grinding wheel diameter based on the processing conditions. The temperature transition shown in FIG. 9(b) represents the temperature transition at the position of the burn depth x occurring in the processed portion Wa (i.e., the boundary surface of grinding burn). The temperature transition estimated by the second estimation unit 82 is stored in the temperature transition storage unit 84 shown in FIG. 3.

[0036] 4-4. Heat generation estimation unit 85 The heat generation amount estimation unit 85 shown in FIG. 3 calculates the heat generation amount Q a generated in the processed part Wa by grinding based on the processing conditions of the workpiece W. in The amount of heat generated Q in may be estimated based on the grinding energy Q′, which is the energy required for grinding the workpiece Wa by the grinding machine 2 and is acquired by the grinding power acquisition unit 31.

[0037] 4-5. Cooling amount estimation section 86 The cooling amount estimation unit 86 shown in FIG. 3 calculates the burn depth x and the heat generation amount Q in and the temperature transition estimated by the second estimation unit 82, the cooling amount Q of the workpiece Wa by the coolant is calculated. out In this embodiment, the cooling amount Q out The estimation is performed as follows: First, the relational expression (1) below is obtained based on the heat transfer equation.

[0038]

number

[0039] Based on the relationship in equation (1), Qout The temperature transition at the burn depth x, where and T are variables, is obtained. Then, a fitting process is performed on the temperature transition obtained based on the relational expression of Equation (1) to the temperature transition estimated by the second estimation unit 82. That is, Q is adjusted so that the temperature transition obtained based on the relational expression of Equation (1) matches the temperature transition estimated by the second estimation unit 82. out When the two match, Q out is estimated as the amount of cooling by the coolant.

[0040] For example, at burn depth x, Q out The temperature transitions obtained based on the relational expression (1) when Q is changed can be shown as shown in Figures 10(a) to 10(c). Comparing these with the temperature transitions estimated by the second estimation unit 82, Q out When Q is set to 5W, the temperature transition obtained based on the relational expression (1) and the temperature transition estimated by the second estimation unit 82 are almost the same. out The cooling amount is estimated as the optimal value of . Then, the burn depth x and Q out The relational expression of Equation (1) using the values ​​of is stored in the cooling amount estimation model storage unit 87 as a cooling amount estimation model.

[0041] 4-6. Burn depth allowance calculation section 88 The allowable burn depth calculation unit 88 shown in FIG. 3 calculates the allowable burn depth, which is the allowable burn depth x, based on the amount removed from the workpiece Wa by the time machining by the grinding machine 2 is completed.

[0042] 22, the grinding process S1 of the workpiece W includes a rough grinding step S11, a fine grinding step S12, a fine grinding step S13, and a spark-out step S14. Since grinding burn mainly occurs in the rough grinding step S11, the amount of material removed in the rough grinding step S11 and the subsequent fine grinding steps S12 and S13 can be calculated as the burn depth allowance.

[0043] 4-7. Final State Evaluation Section 89 3 evaluates the presence or absence of grinding burn in the workpiece Wa based on the burn depth x and the burn depth allowance. In this embodiment, the final state evaluation unit 89 compares the burn depth x with the burn depth allowance, and if it determines that the burn depth x is greater than the burn depth allowance, it evaluates that there is grinding burn in the workpiece Wa at the end of processing by the grinding machine 2. On the other hand, if it determines that the burn depth x is not greater than the burn depth allowance, it evaluates that there is no grinding burn in the workpiece Wa at the end of processing by the grinding machine 2.

[0044] 4-8. Coolant supply amount optimization unit 90 The coolant supply amount optimization unit 90 shown in FIG. 3 optimizes the amount of coolant supplied to the workpiece Wa based on the evaluation result of the final state evaluation unit 89. In this embodiment, if the evaluation result of the final state evaluation unit 89 indicates that grinding burn is present on the workpiece Wa, the coolant supply amount optimization unit 90 increases the flow rate of the coolant supplied to the workpiece Wa. On the other hand, if the evaluation result of the final state evaluation unit 89 indicates that grinding burn is not present on the workpiece Wa, the coolant supply amount optimization unit 90 reduces the flow rate of the coolant. The coolant supply amount optimization unit 90 then optimizes the amount of coolant supplied to the workpiece Wa by repeatedly increasing and / or decreasing the flow rate of the coolant based on the evaluation result of the final state evaluation unit 89.

[0045] 4-9. Machining condition adjustment section 91 3 adjusts the machining conditions based on the evaluation results of the final state evaluation unit 89. In this embodiment, when the evaluation results of the final state evaluation unit 89 indicate that grinding burn is present on the workpiece Wa, the machining condition adjustment unit 91 reduces the tool feed rate or tool spindle rotation speed of the grinding machine 2. On the other hand, when the evaluation results of the final state evaluation unit 89 indicate that grinding burn is not present on the workpiece Wa, the machining condition adjustment unit 91 increases the tool feed rate or tool spindle rotation speed of the grinding machine 2.

[0046] This makes it possible to optimize the tool feed rate or the tool spindle rotation speed while maintaining the coolant supply rate, thereby optimizing the coolant supply rate. Note that the tool feed rate or the tool spindle rotation speed may be optimized by the machining condition adjustment unit 91 in addition to optimizing the coolant supply rate by the coolant supply rate optimization unit 90.

[0047] 5. Grinding burn condition evaluation device 3a 3 acquires the burn depth x of grinding burn occurring on the workpiece Wa from the evaluation results obtained by the grinding burn state evaluation device 3a. The grinding burn state evaluation device 3a of this embodiment will be described in detail below.

[0048] 2, the grinding burn state evaluation device 3a includes a grinding power acquisition unit 31, a dimension information acquisition unit 41, a film boiling boundary power acquisition unit 50, a contact arc length acquisition unit 51, a contact arc heat flux calculation unit 52, a first correspondence relationship storage unit 53, a film boiling region length calculation unit 54, a heat transfer amount calculation unit 55, a feed rate acquisition unit 56, an evaluation unit 60, a display unit 61, a second correspondence relationship storage unit 62, a first correspondence relationship creation unit 100, and a second correspondence relationship creation unit 200. These are configured as storage devices or arithmetic units. Each component will be described in detail below.

[0049] 5-1. Grinding power acquisition unit 31 The grinding power acquisition unit 31 constitutes a grinding energy acquisition unit that acquires grinding energy Q', which is the energy required to grind the workpiece Wa by the grinding machine 2. In this embodiment, the grinding power acquisition unit 31 acquires grinding power, which is the power required to rotate and drive the tool spindle motor 16a, as the grinding energy Q'. The grinding energy Q' is not limited to this grinding power, but can also be calculated as the product of the tangential resistance between the tool (grinding wheel 16) and the workpiece W and the relative speed V+v between the tool and the workpiece W. Note that the grinding energy Q' is the grinding power per unit width in the axial direction of the tool spindle 16b at the workpiece Wa.

[0050] 5-2. Dimension information acquisition unit 41 The dimension information acquiring unit 41 acquires the output of the sizing device 17 and acquires the dimension information of the workpiece W. Note that, if the actual cutting depth is obtained according to the command value, the dimension information acquiring unit 41 may acquire the dimension information of the workpiece W based on the command value without using the sizing device 17.

[0051] 5-3. Film boiling boundary power acquisition part 50 The film boiling boundary power acquiring unit 50 constitutes a film boiling boundary energy acquiring unit that acquires film boiling boundary energy Q'w, which is the energy required for the coolant supplied to the workpiece Wa to reach a film boiling state when the workpiece Wa is ground by the grinding machine 2. In this embodiment, the film boiling boundary power acquiring unit 50 acquires, as the film boiling boundary energy Q'w, film boiling boundary power that corresponds to the grinding power required for the coolant supplied to the workpiece Wa to reach a film boiling state.

[0052] 5-3. Contact arc length acquisition unit 51 The contact arc length acquisition unit 51 acquires the length Lc of the contact arc LC between the grinding wheel 16 and the workpiece Wa in a cross section (see FIG. 5) perpendicular to the main spindle 16b of the grinding wheel 16. 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.

[0053] 5-4. Contact arc heat flux calculation unit 52 The contact arc heat flux calculation unit 52 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 (2) based on the grinding power Q' acquired by the grinding power acquisition unit 31 and the length Lc of the contact arc LC acquired by the contact arc length acquisition unit 51.

[0054]

number

[0055] 5-5. First Correspondence Relationship Storage Unit 53 The first correspondence relationship storage unit 53 stores a first correspondence relationship between the length Lw of the non-film boiling region LW, which is a region in the contact arc LC between the grinding wheel 16 and the workpiece Wa that has not yet reached film boiling, the heat flux qw per unit area generated in the non-film boiling region LW by grinding, and the film boiling boundary power Q'w. Because qw and Lw are inversely proportional, the following relational expression (3) holds. The first correspondence relationship indicates the boundary line for the occurrence of grinding burn on the graph of heat flux vs. contact arc length shown in Figure 7.

[0056]

number

[0057] 5-6. First Correspondence Relationship Creation Unit 100 The first correspondence relationship creating unit 100 creates the above-mentioned first correspondence relationship. In this embodiment, as shown in Fig. 11, the first correspondence relationship creating unit 100 includes a structure change detection unit (eddy current sensor 20), 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, and a grinding burn occurrence estimation unit 44, which are configured by a storage device or a computing device. Note that, in the first correspondence relationship creating unit 100, the configurations provided in the grinding burn state evaluation device 3a can be used for the components that overlap with those provided in the grinding burn state evaluation device 3a.

[0058] 5-6-1. Eddy current sensor 20 In this embodiment, an eddy current sensor 20 is used as a microstructural change detection unit that detects microstructural changes that occur in the workpiece Wa due to grinding by the grinding machine 2. In this embodiment 1, as shown in Fig. 4, 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 Fig. 4, reference numeral 20 indicates the position of the sensor head, and the sensor body is not shown.

[0059] As shown in Fig. 11, the eddy current sensor 20 has a coil serving as an oscillator 21, and applies an output signal to a probe 22 provided at the tip of the sensor head of the eddy current sensor 20, thereby applying a magnetic field to the workpiece W and inducing an eddy current inside the workpiece W. The eddy current sensor 20 then amplifies the change in impedance acquired via the probe 22 in an amplifier 23 and inputs it to a detector 24, extracts only the frequency component of the oscillator 21, processes the signal in a signal processor 25, and outputs it. The magnitude of the eddy current, and therefore the magnitude of the output signal, changes depending on the condition of the processed portion of the workpiece W, etc.

[0060] 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.

[0061] 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.

[0062] 5-6-2. Output signal acquisition unit 40 The output signal acquiring 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.

[0063] 5-6-3. Dimension information acquisition unit 41 The dimension information acquisition unit 41 acquires the dimension information of the workpiece W. As the dimension information of the workpiece W, in this embodiment, as described above, the dimension during the processing of the workpiece W can be acquired by the sizing device 17. Note that instead of 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 3c.

[0064] 5-6-4. Actual cutting amount calculation unit 42 The actual cutting amount calculation unit 42 acquires the cutting amount per rotation of the workpiece W based on the change amount of the dimension information of the workpiece W acquired by the dimension information acquisition unit 41. Then, in the grinding efficiency calculation unit 43, the grinding efficiency Z' is calculated based on the cutting amount per rotation acquired by the actual cutting amount calculation unit 42. The grinding efficiency Z' can be calculated by the following formula (4) from the rotational speed of the workpiece spindle motor and the actual cutting amount.

[0065]

Equation

[0066] Then, the rotational speeds (spindle rotational speeds) of the plurality of tool spindles 16b are acquired from the tool spindle motor 16a, and the calculation is performed at each spindle rotational speed. In the first embodiment, as shown in FIG. 13, the grinding efficiency Z' is calculated for three patterns of spindle rotational speeds R1, R2, and R3 (where the relationship R1 < R2 < R3 is satisfied).

[0067] The grinding burn occurrence estimation unit 44 detects a sudden change region Sc where the output signal P (eddy current voltage V) acquired by the output signal acquisition unit 40 suddenly changes as shown in FIG. 14(a) during a specific section Ts in which the grinding efficiency of the grinding machine 2 is continuously changed by the control device 3c, and estimates that grinding burn has occurred in the processed portion Wa. The specific section Ts is a section included in the rough grinding process S11 in the grinding process. As shown in FIG. 14(b), the specific section Ts is a transient response period in which the actual cutting depth changes from an initial value A0 (a state in which the grinding wheel 16 and the workpiece W are not in contact) to a command value SA instructed by the control device 3c based on the grinding conditions. During this period, the actual cutting depth changes so as to continuously increase from the initial value A0 to the command value SA. As shown in FIG. 13, since the actual cutting depth is proportional to the grinding efficiency Z', in the specific section Ts, the grinding efficiency Z' also changes so as to increase continuously from the initial value corresponding to the initial value A0 to the target value corresponding to the command value SA.

[0068] 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. 14(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, as shown in FIG. 14(b), the actual cutting depth becomes A, and as shown in FIG. 14(c), the drive power of the tool spindle motor 16a when the actual cutting depth becomes A is B. Alternatively, the reference value Ps can be a region where the rate of change of the output signal P in the specific section Ts is greater than a predetermined reference rate of change.

[0069] In the sudden change region Sc, grinding burn occurs on 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 time, and the output signal (eddy current voltage) of the eddy current sensor 20, which changes in response to the structural change (formation of a work-affected layer) caused in the workpiece W by grinding burn, also changes within a short time, so the output signal exhibits a steep change (sudden change).

[0070] Then, the driving power B (see FIG. 14(c)) of the tool spindle 16b acquired by the grinding burn occurrence estimation unit 44 is converted into a value per unit width and acquired as the film boiling boundary power Q'w in the above-mentioned first correspondence relationship. Further, the above-mentioned contact arc length acquisition unit 51 acquires the length of the contact arc in the abrupt change region Sc as Lw. Further, the above-mentioned contact arc heat flux calculation unit 52 calculates qw from the relational expression qw=Q'w / Lw. Then, these are stored as the first correspondence relationship in the first correspondence relationship storage unit 53.

[0071] 5-6-5. Cooling state grasping unit 102 The cooling state determining unit 102 determines the cooling state of the coolant CL and outputs information related to the cooling state. In this embodiment, the cooling state of the coolant CL includes at least the grinding wheel sharpness K and may further include the temperature Ta, flow rate Fa, and coolant power Qa of the coolant CL. Here, the film boiling boundary power Q'w varies depending on the grinding wheel sharpness K, the temperature Ta, flow rate Fa, and coolant power Qa acquired by the cooling state determining unit 102 shown in FIG. 11. Therefore, in order to reflect the influence of these changes on the film boiling boundary power Q'w, the cooling state reflecting unit 107 performs a regression analysis using the film boiling boundary power Q'w as the objective variable and at least one or all of the grinding wheel sharpness K, the temperature Ta, flow rate Fa, and coolant power Qa as the explanatory variables, and updates the film boiling boundary power Q'w stored in the first correspondence relationship storage unit 53 based on the results of the regression analysis. The explanatory variables preferably include the grinding wheel sharpness K because it has a large influence on the film boiling boundary power Q'w.

[0072] The grinding wheel sharpness K is calculated by the grinding wheel sharpness calculation unit 103 in the cooling state grasping unit 102 based on the relational expression K=(Q / width) / Z' from the grinding power Q of the tool spindle motor 16a and the grinding efficiency Z' calculated by the grinding efficiency calculation unit 43.

[0073] The temperature Ta of the coolant CL is acquired by a coolant temperature acquisition unit 105 in the cooling state grasping unit 102. The flow rate Fa of the coolant CL is acquired by a coolant flow rate acquisition unit 106 in the cooling state grasping unit 102. In addition, the coolant power Qa is calculated by a coolant power calculation unit 104 as the difference between the spindle power Q0 when the tool 16 is idling without supplying the coolant CL in the grinding machine 2, and the spindle power Q1 when the coolant CL is supplied.

[0074] In this embodiment, the film boiling boundary power Q'w can be expressed as the following relational expression (5) using a multiple regression equation for the regression analysis. Note that b0 to b4 are all coefficients. The regression analysis method is not limited to this, and known statistical methods or machine learning can also be applied.

[0075]

number

[0076] Then, the film boiling boundary power acquiring unit 50 acquires the film boiling boundary power Q'w from the heat flux q acquired by the contact arc heat flux calculating unit 52 and the length Lc of the contact arc LC acquired by the contact arc length acquiring unit 51, based on the first correspondence relationship (Q'w=q×Lw) that reflects the influence of each explanatory variable acquired by the cooling state grasping unit 102. That is, in the graph shown in Fig. 7, by specifying the coordinates of (Lc, q), the film boiling boundary power Q'w on the curve that indicates the first correspondence relationship is acquired.

[0077] 5-7. Film boiling region length calculation section 54 The film boiling region length calculation unit 54 calculates the length Lm of the film boiling region LM at the contact arc Lc based on the grinding power Q', the film boiling boundary power Q'w, and the length Lc of the contact arc LC. Lm can be calculated based on the following relational expressions (6) and (7).

[0078]

number

[0079]

number

[0080] Here, if the length Lm of the film boiling region LM is 0 or less, it can be determined that the film boiling region LM has not occurred and that grinding burn has not occurred, and if the length Lm of the film boiling region LM is greater than 0, it can be determined that grinding burn has occurred.

[0081] 5-8. Passing heat calculation section 55 The heat-transmitting calculation unit 55 calculates the film boiling region heat quantity Jm, which is the amount of heat generated in the film boiling region LM, which is the region where the coolant CL is in a film boiling state in the machined portion Wa, based on the grinding power Q' and the film boiling boundary power Q'w. In this embodiment, the film boiling region heat quantity Jm is calculated using the following relational expression (8) 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 speed v of the workpiece W relative to the tool 16 provided on the grinding machine 2. The feed speed v of the workpiece W can be acquired by the feed speed acquisition unit 56 based on the rotational speed of the workpiece motor 12a.

[0082]

number

[0083] 5-8.Evaluation Section 60 The evaluation unit 60 evaluates the grinding burn state of the workpiece Wa based on the grinding power Q' and the film boiling boundary power Q'w. In this embodiment, the evaluation unit 60 evaluates the grinding burn state of the workpiece Wa based on the film boiling region heat passing amount Jm. More specifically, the evaluation unit 60 evaluates the depth of grinding burn occurring in the workpiece Wa based on the film boiling region heat passing amount Jm and a second correspondence relationship described below.

[0084] Alternatively, the evaluation unit 60 can evaluate that the film boiling region LM has not occurred and that grinding burn has not occurred when the length Lm of the film boiling region LM is 0 or less, and that the film boiling region LM has occurred and that grinding burn has occurred when the length Lm of the film boiling region LM is greater than 0. The evaluation unit 60 can also evaluate whether grinding burn has occurred or not based on the grinding power Q' and the film boiling boundary power Q'w. For example, when Q'w / Q'<1 is satisfied, it can be evaluated that grinding burn has occurred. The evaluation result can be displayed on the display unit 61.

[0085] 5-9. Second Correspondence Relationship Storage Unit 62 The second correspondence relationship storage unit 62 stores, as the second correspondence relationship described above, a correspondence relationship between the amount of heat passing through the film boiling region Jm 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 second correspondence relationship is a linear relationship between the amount of heat passing through the film boiling region Jm 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 the evaluation results when the processing conditions and grinding wheel sharpness shown in Fig. 13 are changed.

[0086] 5-10. Second Correspondence Relationship Creation Unit 200 The second correspondence relationship creating unit 200 creates the second correspondence relationship described above. As shown in FIG. 17 , the second correspondence relationship creating unit 200 includes an eddy current sensor 20, an output signal acquiring unit 40, a first characteristic information acquiring unit 71, a time memory unit 72, an inflection point determination criterion memory unit 73, an inflection point calculating unit 74, a dimension information acquiring unit 41, a second characteristic information acquiring unit 75, a rotation time acquiring unit 76, an inflection point time extracting unit 77, and a burn depth calculating unit 78, all of which are configured as a storage device or a computing device. Note that the second correspondence relationship creating unit 200 can use the same components as those of the grinding burn condition evaluating device 3a or the first correspondence relationship creating unit 100.

[0087] 5-10-1. Eddy current sensor 20 The eddy current sensor 20 shown in FIG. 17 induces an eddy current inside the workpiece W using an excitation current and outputs an AC signal corresponding to the magnetic field generated by the eddy current. The eddy current sensor 20 may be configured to be able to change the phase of the output signal. In this embodiment, as shown in FIG. 17, the eddy current sensor 20 has a coil serving as an oscillator 21, and by supplying an excitation current to the coil, an output signal is applied to a probe 22 provided at the tip of the sensor head of the eddy current sensor 20, thereby applying a magnetic field to the workpiece W and inducing an eddy current inside the workpiece W. The eddy current sensor 20 then amplifies the change in impedance acquired via the probe 22 in an amplifier 23 and inputs it to a detector 24, extracts only the frequency component of the oscillator 21, and processes the signal in a signal processor 25.

[0088] The detection unit 24 detects the signal by synchronous detection. As shown in Fig. 18, the input signal v(t) to the detection unit 24 is a signal obtained by amplifying the output of the probe 22 in the amplifier unit 23, and v(t) is defined by the following equation (9). Note that t is time, A is amplitude, f is the frequency of the oscillator 21 inside the eddy current sensor 20, and θ is the phase difference with respect to the oscillator 21 inside the eddy current sensor 20.

[0089]

number

[0090] Then, v(t) that has passed through the amplifier section 23 is multiplied in the detector section 24 by a sine wave sin2πft having the same frequency f as that of the oscillator section 21 with respect to v(t). Let this be x(t). Similarly, let the result of multiplication by cos2πft be y(t). x(t) and y(t) can be expressed as in the following equations (10) and (11).

[0091]

Equation

[0092]

Equation

[0093] Next, x(t) and y(t) are passed through a low-pass filter having a sufficiently low cut-off frequency fc. Generally, the relationship fc << f holds. The first terms in equations (10) and (11) are AC because they include t, while the second terms are DC because they do not include t. Therefore, after passing through the low-pass filter, equations (10) and (11) become the real-axis signal X and the imaginary-axis signal Y shown in the following equations (12) and (13), respectively.

[0094]

Equation

[0095]

Equation

[0096] Then, as shown in the following equations (14) and (15), A and θ of v(t) can be obtained from equations (12) and (13).

[0097]

Equation

[0098]

number

[0099] The signal processing unit 25 performs gain and phase manipulation on the real axis signal X and imaginary axis signal Y of the detection unit 24. Therefore, the output signal of the eddy current sensor 20 is output from the detection unit 24 through the signal processing unit 25, and the frequency characteristics of the eddy current sensor 20 are the product of the frequency characteristics of the detection unit 24 and the signal processing unit 25. In general, the frequency characteristics of the signal processing unit 25 are equal to or less than the frequency characteristics of the detection unit 24. In the output signal output from the signal processing unit 25, X represents the real axis signal and Y represents the imaginary axis signal. The real axis signal X represents the real axis value of the output signal P, and the imaginary axis signal Y represents the imaginary axis value of the output signal P.

[0100] The eddy current sensor 20 is configured to supply multiple excitation currents with different frequencies to the coil. In the first embodiment, the frequency of the excitation current can be set by the frequency setting unit 26. 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 the magnetic property change characteristic decreases in areas shallow from the machined surface, resulting in reduced detection accuracy.

[0101] The frequency of the excitation current according to the penetration depth can be set in the frequency band of 20 kHz to 200 MHz, preferably 100 kHz to 200 MHz, and more preferably 250 to 2500 kHz. In this embodiment, the frequency of the excitation current is set to 250 kHz so that the penetration depth of the eddy current is 30 μm.

[0102] 5-10-1. Output signal acquisition unit 40 The output signal acquisition unit 40 acquires the output signal P output from the eddy current sensor 20. When expressed on a complex plane in Cartesian coordinate format, the output signal P has a value on the imaginary axis Y and a value on the real axis X, and can be expressed on the complex plane as shown in Figure 19(b) or Figure 20(b). The frequency of the excitation current output from the oscillator 21 in the eddy current sensor 20 can be adjusted by the frequency setting unit 26.

[0103] 5-10-2. First characteristic information acquisition unit 71 The first characteristic information acquiring unit 71 acquires first characteristic information. The first characteristic information is information obtained by linking at least one of the imaginary axis value and the real axis value when the output signal P acquired by the output signal acquiring unit 40 is represented on a complex plane in a Cartesian coordinate system with time information indicating the time when the workpiece W is ground. In this embodiment, both the imaginary axis value and the real axis value of the output signal P represented on the complex plane shown in Fig. 19(b) are linked to the elapsed time from the start of grinding measured by the time memory unit 72 described later.

[0104] 5-10-3. Time storage section 72 The time memory unit 72 measures the elapsed time from the start time T0 of the grinding process. In this embodiment, the grinding process S1 of the workpiece W includes a rough grinding process S11, a fine grinding process S12, a fine grinding process S13, and a spark-out process S14, as shown in Fig. 22. Each process will be described later.

[0105] 5-10-4. Inflection point judgment criteria storage section 73 The inflection point judgment criterion storage unit 73 pre-stores inflection point judgment criteria for determining whether the output signal represented on the complex plane has reached an inflection point (described later) for each frequency of the excitation current. In this embodiment, the inflection point judgment criterion can be created based on the correspondence between the frequency of the excitation current, first characteristic information acquired by applying an excitation current having that frequency to a workpiece for creating an inflection point judgment criterion during machining, and the grinding burn state of the workpiece for creating an inflection point judgment criterion. The workpiece for creating an inflection point judgment criterion has the same shape and material as the workpiece W to be evaluated, as shown in FIG. 1.

[0106] 19(a) and 19(b) show the correspondence relationship between the first feature information and the grinding burn state when the excitation current frequency is 250 kHz, and Fig. 20(a) and 20(b) show the correspondence relationship between the first feature information and the grinding burn state when the excitation current frequency is 1000 kHz. Comparing the case where the excitation current frequency is 250 kHz with the case where the excitation current frequency is 1000 kHz, the correspondence relationship shown on the complex plane for the case where the excitation current frequency is 1000 kHz is expressed as a shape rotated -90 degrees from the case where the excitation current frequency is 250 kHz.

[0107] Next, the trajectory of the output signal P on the complex plane will be described with reference to Fig. 19(b). On the complex plane shown in Fig. 19(b), the output signal P output from the eddy current sensor 20 is plotted at the position indicated by reference symbol A1 at the start of grinding. Thereafter, in the rough grinding step S11, when grinding burn occurs on the workpiece W, the magnetic characteristics change accordingly, and as a result, the value of the real axis of the output signal P on the complex plane decreases and the value of the imaginary axis increases slightly over time. After that, the value on the real axis decreases and the value on the imaginary axis decreases, and then the value on the real axis increases and the value on the imaginary axis decreases, until the position indicated by reference symbol A2 is reached, at which point the rough grinding step S11 ends.

[0108] Thereafter, when the fine grinding process S12 begins, as grinding burns (process-affected layer, softened layer) that had occurred on the workpiece W are gradually removed, the output signal P in the complex plane decreases in value on the real axis and gradually increases in value on the imaginary axis. That is, near the start point B1 of the fine grinding process S12, the vector direction in the imaginary axis direction in the locus of the output signal P in the complex plane is pointing upward. Thereafter, as grinding progresses further and the position indicated by reference symbol B2 is reached, the value on the real axis increases, but the value on the imaginary axis continues to gradually increase. Then, at the position indicated by reference symbol B3, the value on the real axis continues to increase, but the value on the imaginary axis decreases. That is, at reference symbol B3, the output signal P reaches its maximum value in the fine grinding process S12, and thereafter the vector direction in the imaginary axis direction in the locus of the output signal P in the complex plane changes to a downward direction. Thereafter, the value on the real axis increases, but the value on the imaginary axis decreases, until the position indicated by reference symbol B4 is reached and the rough grinding process S11 is completed.

[0109] 5-10-5. Inflection point calculation unit 74 The inflection point calculation unit 74 calculates an inflection point based on an inflection point determination criterion. An inflection point indicates a point where the vector direction of the output signal P on the complex plane changes in the imaginary axis direction or the real axis direction. Therefore, when the frequency of the excitation current shown in FIG. 19(b) is 250 kHz, the inflection point is represented by point B3 where the vector direction of the output signal P in the imaginary axis direction changes from upward to downward. Note that when the frequency of the excitation current shown in FIG. 20(b) is 1000 kHz, the inflection point is also represented by point B3 where the vector direction of the output signal P in the imaginary axis direction changes from downward to upward.

[0110] Since the locus of the output signal P in the complex plane changes depending on the frequency of the excitation current, the inflection point determination criterion for the inflection point also changes. In this embodiment, the inflection point determination criterion storage unit 73 stores the locus of the output signal P in the complex plane for each excitation current frequency for a workpiece used to create the inflection point determination criterion (master), and based on this, the inflection point determination criterion is stored for each excitation current frequency. For example, as described above, the inflection point determination criterion for a 250 kHz excitation current frequency is such that the inflection point is determined to be the point at which the direction of the vector of the locus of the output signal P stored in the inflection point determination criterion storage unit 73 shown in Figure 19(b) changes from upward to downward in the imaginary axis direction in the fine grinding process S12. Furthermore, the inflection point determination criterion when the frequency of the excitation current is 1000 kHz is that the inflection point is the point at which the direction of the vector of the trajectory of the output signal P stored in the inflection point determination criterion memory unit 73 shown in Figure 20(b) changes from downward to upward in the imaginary axis direction during the fine grinding process S12.

[0111] Furthermore, the inflection point judgment criterion storage unit 73 also stores the correspondence between the first characteristic information and the grinding burn state for the workpiece used to create the inflection point judgment criterion. When the excitation current frequency is 250 kHz as shown in FIG. 19(b), the region from the precision grinding process start point B1 to the inflection point B3 in the precision grinding process S12 indicates a state in which the workpiece W has a softened layer that will cause grinding burn. The region from the inflection point B3 to the vicinity of the processing end point B4 indicates a state in which the workpiece W does not have a softened layer, but a retained austenite-reduced layer that had formed deeper in the softened layer remains in the workpiece W. The retained austenite-reduced layer has mechanical properties closer to the base material than the softened layer, so it is not included in the grinding burn. At the processing end point B4, there is also no retained austenite-reduced layer. This is also true when the excitation current frequency is 1000 kHz as shown in FIG. 20(b).

[0112] 17 acquires dimensional information of the workpiece W, as described above, and in this embodiment, the sizing device 17 can detect the dimensions of the workpiece W during machining. Note that instead of using the sizing device 17, the dimensional information of the workpiece W may be indirectly calculated and acquired based on the coordinate position of the Z axis, which is the cutting axis of the workpiece W, output from the control device 3c.

[0113] 5-10-6. Second characteristic information acquisition unit 75 The second characteristic information acquisition unit 75 acquires the second characteristic information. The second characteristic information is information that links the dimension information acquired by the dimension information acquisition unit 41 with time information.

[0114] 5-10-7. Rotation time acquisition unit 76 The rotation time acquisition unit 76 shown in FIG. 17 stores the time acquired each time the workpiece W rotates once or a predetermined number of times from the end of the rough grinding step S11 as the rotation time. In this embodiment, the time acquired each time the workpiece W rotates once from the end of the rough grinding step S11 is stored as the rotation time. Here, in the grinding process S1, grinding burn occurs in the rough grinding step S11, which has high grinding efficiency. Therefore, the workpiece ground by the grinding wheel 16 at the end of the rough grinding step S11 has the largest burn depth, which is the depth of grinding burn. The rotation time corresponds to the time of the bottom of the valley shape that repeatedly appears in the real axis signal in FIG. 19(a). The lower envelope is drawn by connecting the bottoms of each valley shape.

[0115] 5-10-8. Inflection point time extraction part 77 17 extracts, from the first feature information, a time at which an inflection point appears in the trajectory of the output signal represented on the complex plane, as an inflection point time. In this embodiment, the inflection point time is extracted from among the multiple rotation times acquired by the rotation time acquisition unit 76. For example, in FIGS. 19(a) and 20(a), the inflection point time extraction unit 77 extracts the time at which inflection point B3 appears as inflection point time T2.

[0116] 5-10-9. Burn depth calculation section 78 The burn depth calculation unit 78 shown in Fig. 17 calculates the burn depth of the processed portion of the workpiece W based on the inflection point time extracted by the inflection point time extraction unit 77. As shown in Fig. 21, in the dimensional information of the workpiece W from the grinding start time T0 to the grinding end time Te, the burn depth tb at the end time T1 of the rough grinding process is calculated as the difference D1 between the dimensional information at the end time T1 of the rough grinding process and the dimensional information at the inflection point time T2.

[0117] In parallel with the calculation of the grinding burn depth tb in the second correspondence relationship creation unit 200, the heat quantity Jm passing through the film boiling region is calculated as described above by the heat quantity calculation unit 55 shown in Fig. 2. Then, by changing the grinding conditions and obtaining a plurality of relationships between the grinding burn depth tb and the heat quantity Jm passing through the film boiling region, a second correspondence relationship approximated by a straight line as shown in Fig. 16 is created, and this is stored in the above-mentioned second correspondence relationship storage unit 62 shown in Fig. 17.

[0118] 5-11. Evaluation of Burn Depth by Evaluation Unit 60 As described above, in this embodiment, the depth of grinding burn occurring in the processed portion Wa is evaluated based on the amount of heat Jm passing through the film boiling region and the second correspondence relationship created as described above by the evaluation unit 60 shown in Fig. 2. That is, by acquiring the amount of heat Jm passing through the film boiling region for the workpiece W to be evaluated, the depth tb of grinding burn at the end of the rough grinding step S11 can be evaluated using the second correspondence relationship shown in Fig. 16.

[0119] In addition, instead of using the second correspondence relationship, the evaluation unit 60 may evaluate the burn depth in stages, such as "large, medium, small," based on the magnitude of the heat quantity Jm passing through the film boiling region.

[0120] 6. Grinding Process S1 Description The grinding process S1 will be described with reference to Fig. 22. As described above, the grinding process S1 performed by the grinding machine 2 includes the rough grinding step S11, the fine grinding step S12, the fine grinding step S13, and the spark-out step S14.

[0121] In the rough grinding step S11, the control device 3c 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 3c 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 3c 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.

[0122] The cutting depth can be adjusted by controlling the cutting position of the grinding wheel 16 with the control device 3c. 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.

[0123] 7. Cooling capacity evaluation process S2 Next, the evaluation process S2 of the cooling capacity by the cooling capacity evaluation device 3b provided in the grinding burn state evaluation system 1 will be described with reference to the flowchart of Fig. 23. The evaluation process S2 of the grinding burn state can be performed in parallel with the grinding processing process S1.

[0124] In the grinding burn state evaluation process S2, first, in step S21 shown in Fig. 23, the burn depth in the processed part Wa is acquired by the burn depth acquisition unit 80. In this embodiment, the burn depth acquisition unit 80 acquires the burn depth from the evaluation result of the grinding burn state evaluation device 3a.

[0125] 23, the first estimation unit 81 estimates the transformation point temperature T and the cooling time t of the workpiece W. In this embodiment, the transformation point temperature T is the temperature of the A1 transformation point, and the cooling time t is estimated from the transformation point temperature T and the upper critical cooling rate shown in the CCT diagram shown in FIG.

[0126] 23, the second estimation unit 82 estimates the temperature transition at the burn depth position x of the processed portion Wa from the transformation point temperature T, the cooling time t, and the processing conditions of the workpiece W. In this embodiment, as shown in FIG. 9(b), the transformation point temperature T is near the temperature peak, and the temperature transition from cooling to room temperature over the cooling time t is estimated.

[0127] Then, in step S24 shown in FIG. 23, the heat generation amount estimating unit 85 estimates the heat generation amount generated in the processed portion Wa due to grinding based on the processing conditions of the workpiece W.

[0128] Next, the cooling amount estimation unit 86 calculates the burn depth x and the heat generation amount Q in and the temperature transition estimated by the second estimation unit 82, the cooling amount Q of the workpiece Wa by the coolant is calculated. out In this embodiment, Q is estimated based on the relational expression (1) above. out The temperature transition at the burn depth x, where and T are variables, is acquired, and the temperature transition obtained based on the relational expression of Equation (1) is calculated so that it matches the temperature transition estimated by the second estimation unit 82. out When the two match, Q out is estimated as the amount of cooling by the coolant. Then, this amount of cooling is evaluated as the cooling capacity. In addition, the burn depth x and Q out The relational expression of Equation (1) using the values ​​of is stored as a cooling amount estimation model in the cooling amount estimation model storage unit 87. Then, the cooling capacity evaluation process S2 is terminated.

[0129] 8. Coolant flow rate optimization process S3 Next, the coolant flow rate optimization process S3 performed by the grinding burn state evaluation system 1 will be described with reference to the flow chart of Fig. 24. The coolant flow rate optimization process S3 can be performed in parallel with the grinding process S1.

[0130] In the coolant flow rate optimization process S3, first, in step S31 shown in Fig. 24, the burn depth x in the workpiece Wa is acquired by the burn depth acquisition unit 80. In this embodiment, the burn depth acquisition unit 80 acquires the burn depth from the evaluation result of the grinding burn state evaluation device 3a.

[0131] 24, the cooling amount is estimated by the cooling amount estimation unit 86. The cooling amount is estimated by inputting the burnt depth x obtained in step S31 into the cooling amount estimation model stored in the cooling amount estimation model storage unit 87.

[0132] Next, in step S33 shown in Figure 24, the burn depth allowance calculation unit 88 calculates the burn depth allowance, which is the allowable burn depth x, based on the amount removed from the workpiece Wa by the time processing by the grinding machine 2 is completed.

[0133] 24, the final state evaluation unit 89 compares the burn depth x with the burn depth allowance. If it is determined in step S34 that the burn depth x is greater than the burn depth allowance, the process proceeds to Yes in step S34, and in step S35 the final state evaluation unit 89 evaluates that grinding burn will occur in the processed portion Wa at the end of machining by the grinding machine 2. Thereafter, in step S36, the coolant supply amount optimization unit 90 controls the coolant supply device 19 to increase the flow rate of the coolant supplied to the processed portion Wa.

[0134] On the other hand, if it is determined in step S34 that the burn depth x is not greater than the burn depth allowance, the process proceeds to No in step S34, and in step S37 the final state evaluation unit 89 evaluates that there is no grinding burn on the processed part Wa at the end of processing by the grinding machine 2. Thereafter, in step S38, the coolant supply amount optimization unit 90 controls the coolant supply device 19 to reduce the flow rate of the coolant supplied to the processed part Wa.

[0135] Then, after step S36 or step S38, in step S39, the coolant supply amount optimization unit 90 determines whether the increase and decrease in the coolant flow rate are smaller than the reference value. If it is determined in step S39 that the increase and decrease in the coolant flow rate are smaller than the reference value, the process proceeds to Yes in step S39, the optimization of the coolant supply rate is considered complete, and the flow ends. On the other hand, if it is determined in step S39 that the increase and decrease in the coolant flow rate are not smaller than the reference value, the process proceeds to No in step S39, and step S31 and subsequent steps are performed again. Note that when performing step S31 and subsequent steps again, the previously calculated allowable burn depth amount is used, and step S33 can be omitted.

[0136] 9. Processing condition optimization process S4 Next, the processing condition optimization process S4 by the grinding burn state evaluation system 1 will be described with reference to the flow diagram of Fig. 25. In the processing condition optimization process S4 shown in Fig. 25, steps equivalent to those in the coolant flow rate optimization process S3 shown in Fig. 24 are denoted by the same reference numerals as in the coolant flow rate optimization process S3, and descriptions thereof will be omitted.

[0137] In the machining condition optimization process S4, steps S31 to S35 and S37 are performed in the same manner as in the coolant flow rate optimization process S3 shown in Fig. 24. Then, in step S35 shown in Fig. 25, the final state evaluation unit 89 evaluates that grinding burn has occurred in the machined portion Wa at the end of machining by the grinding machine 2, and then in step S46, the machining condition adjustment unit 91 reduces the tool feed rate or tool spindle rotation speed of the grinding machine 2.

[0138] On the other hand, in step S37 shown in FIG. 25, the final state evaluation unit 89 evaluates that there is no grinding burn on the processed part Wa at the end of processing by the grinding machine 2, and then in step S48, the processing condition adjustment unit 91 increases the tool feed speed or tool spindle rotation speed of the grinding machine 2.

[0139] Then, after step S46 or step S48, in step S49, the machining condition adjustment unit 91 determines whether the increase or decrease in the tool feed rate or tool spindle rotation speed is smaller than the reference value. If it is determined in step S49 that the increase or decrease in the tool feed rate or tool spindle rotation speed is smaller than the reference value, the process proceeds to Yes in step S49, the optimization of the machining conditions is considered to be complete, and the flow ends. On the other hand, if it is determined in step S49 that the increase or decrease in the tool feed rate or tool spindle rotation speed is not smaller than the reference value, the process proceeds to No in step S49, and step S31 and subsequent steps shown in FIG. 25 are performed again.

[0140] 10. Action and Effects According to the cooling capacity evaluation device 3b of this embodiment, the temperature transition at the burn depth position is estimated from the transformation point temperature T of the processed part Wa, the cooling time t required for the structure of the processed part Wa that has reached the transformation point temperature to change into a structure that exhibits grinding burn, and the processing conditions of the workpiece W, and the temperature transition and the heat amount Q generated in the processed part Wa are calculated. in From the burn depth x, the cooling amount Q of the processed part Wa by the coolant out By estimating this, the cooling capacity of the coolant can be quantified and evaluated.

[0141] In the cooling capacity evaluation device 3b of this embodiment, the cooling amount estimation unit 86 calculates the burn depth x and the heat generation amount Q in and cooling amount Q out The cooling amount Q is calculated so that the temperature transition calculated based on the heat conduction equation matches the temperature transition estimated by the second estimation unit 82. out This estimates the cooling amount Q out can be estimated with high accuracy.

[0142] In the cooling capacity evaluation device 3b of this embodiment, the first estimation unit 81 estimates the time required for cooling from the transformation point temperature T to room temperature based on the CCT diagram as the cooling time t. This makes it possible to accurately estimate the cooling time t required for the structure of the processed portion Wa to change to a structure that exhibits grinding burn, and the cooling amount Q out can be estimated with high accuracy.

[0143] In the cooling capacity evaluation device 3b of this embodiment, the first estimation unit 81 estimates the cooling time t based on the upper critical cooling rate shown in the CCT diagram. This makes it possible to more accurately estimate the cooling time t required for the structure of the processed portion Wa to change into a structure that exhibits grinding burn, and the cooling amount Q out can be estimated with high accuracy.

[0144] Furthermore, in this embodiment, the burn depth acquisition unit 80 acquires grinding burn information for the workpiece Wa based on the grinding power (Q'), which is the power required to grind the workpiece Wa by the grinding machine 2, and the film boiling boundary power (Q'w), which corresponds to the grinding power required for the coolant supplied to the workpiece Wa to reach a film boiling state when the workpiece Wa is ground by the grinding machine 2. This makes it possible to achieve a highly accurate evaluation of the grinding burn state, taking into account the fact that the coolant CL reaches a film boiling state in the workpiece Wa.

[0145] Next, in the grinding burn state evaluation system 1 of this embodiment, the cooling capacity evaluation device 3b is equipped with a burn depth allowance calculation unit 88 that calculates a burn depth allowance, which is an allowable burn depth, based on the amount removed from the workpiece portion Wa by the time machining is completed by the grinding machine 2, and a final state evaluation unit 89 that compares the burn depth x with the burn depth allowance, and evaluates that there is grinding burn in the workpiece portion Wa at the end of machining if it is determined that the burn depth x is greater than the burn depth allowance, and evaluates that there is no grinding burn in the workpiece portion Wa at the end of machining if it is determined that the burn depth x is not greater than the burn depth allowance. This makes it possible to evaluate with high accuracy the presence or absence of grinding burn in the workpiece portion Wa at the end of machining.

[0146] The grinding burn state evaluation system 1 of this embodiment also includes a coolant supply amount optimization unit 90 that optimizes the amount of coolant supplied to the workpiece Wa based on the evaluation result of the final state evaluation unit 89. This makes it possible to prevent excessive supply of coolant while suppressing the remaining grinding burn.

[0147] Furthermore, in the grinding burn state evaluation system 1 of this embodiment, the coolant supply amount optimization unit 90 increases the flow rate of coolant supplied to the processed portion Wa when the evaluation result in the final state evaluation unit 89 indicates the presence of grinding burn on the processed portion Wa, and reduces the flow rate of coolant when the evaluation result in the final state evaluation unit 89 indicates the absence of grinding burn on the processed portion Wa. Then, by repeatedly increasing and / or decreasing the flow rate of coolant based on the evaluation result in the final state evaluation unit 89, the amount of coolant supplied to the processed portion Wa is optimized. This makes it possible to further prevent excessive supply of coolant while suppressing the remaining grinding burn.

[0148] The grinding burn condition evaluation system 1 of this embodiment also includes a machining condition adjustment unit 91 that adjusts the machining conditions based on the evaluation results of the final state evaluation unit 89. If the evaluation results of the final state evaluation unit 89 indicate the presence of grinding burn on the workpiece Wa, the machining condition adjustment unit 91 reduces the tool feed rate or tool spindle rotation speed of the grinding machine 2, and if the evaluation results of the final state evaluation unit 89 indicate the absence of grinding burn on the workpiece Wa, the machining condition adjustment unit 91 increases the tool feed rate or tool spindle rotation speed of the grinding machine 2. The machining conditions are optimized by repeatedly increasing and / or decreasing the tool feed rate or tool spindle rotation speed based on the evaluation results of the final state evaluation unit 89. This makes it possible to optimize the machining conditions while suppressing residual grinding burn.

[0149] As described above, according to the above aspect, it is possible to provide a cooling capacity evaluation device 3b capable of evaluating the cooling capacity of a coolant for the grinding heat generated in the workpiece Wa by grinding.

[0150] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the spirit of the present invention. For example, in this embodiment, both the coolant supply amount optimization unit 90 and the machining condition adjustment unit 91 are provided, but instead, a configuration may be adopted in which only one of them is provided. [Explanation of symbols]

[0151] 1 Grinding burn condition evaluation system 2 Grinding machines 3 Processing section 3a Grinding burn condition evaluation device 3b Cooling capacity evaluation device 3c Control device 19 Coolant supply device 80 Burn depth acquisition unit 81 1st estimation part 82 Second estimation part 83 CCT diagram storage section 84 Temperature transition memory section 85 Heat generation estimation section 86 Cooling amount estimation section 87 Cooling amount estimation model memory section 88 Allowable amount calculation section 89 Final State Evaluation Unit 90 Coolant supply amount optimization section 91 Machining condition adjustment section

Claims

1. A cooling capacity evaluation device for evaluating the cooling capacity of a processed portion of a workpiece that is ground by a grinding machine while supplying a coolant, comprising: a first estimation unit that estimates a transformation point temperature of the processed portion and a cooling time required for the structure of the processed portion that has reached the transformation point temperature to change into a structure that exhibits grinding burn; a second estimation unit that estimates a temperature transition at a depth position of grinding burn occurring in the processed portion based on the transformation point temperature, the cooling time, and the processing conditions of the workpiece; a burn depth acquisition unit that acquires a burn depth, which is the depth of grinding burn occurring on the processed portion; a heat generation amount estimation unit that estimates a heat generation amount generated in the processed portion by grinding based on the processing conditions of the workpiece or grinding energy, which is energy required to grind the processed portion by the grinding machine; a cooling amount estimation unit that estimates a cooling amount of the workpiece by the coolant based on the burn depth, the heat generation amount, and the temperature transition estimated by the second estimation unit; A cooling capacity evaluation device comprising:

2. 2. The cooling capacity evaluation device according to claim 1, wherein the cooling amount estimation unit estimates the cooling amount so that a temperature transition calculated based on a heat conduction equation from the burn depth, the heat generation amount, and the cooling amount matches the temperature transition estimated by the second estimation unit.

3. The cooling capacity evaluation device according to claim 1 or 2, wherein the first estimation unit estimates, as the cooling time, a time required for cooling from the transformation point temperature to room temperature based on a CCT diagram.

4. The cooling capacity evaluation device according to claim 1 , wherein the first estimation unit estimates the cooling time based on an upper critical cooling rate represented on a CCT diagram.

5. The cooling capacity evaluation device described in claim 1 or 2, wherein the burn depth acquisition unit acquires grinding burn information of the workpiece based on a grinding power (Q') that is the power required to grind the workpiece using the grinding machine and a film boiling boundary power (Q'w) that corresponds to the grinding power required for the coolant supplied to the workpiece to reach a film boiling state when grinding the workpiece using the grinding machine.

6. The cooling capacity evaluation device according to claim 1 or 2; a burnt depth allowance calculation unit that calculates a burnt depth allowance that is an allowable burnt depth based on the amount removed from the workpiece by the time the grinding by the grinding machine is completed; a final state evaluation unit that compares the burn depth with the burn depth allowance, and if it is determined that the burn depth is greater than the burn depth allowance, evaluates that there is grinding burn on the processed portion at the time of completion of processing by the grinding machine, and if it is determined that the burn depth is not greater than the burn depth allowance, evaluates that there is no grinding burn on the processed portion at the time of completion of processing by the grinding machine; A grinding burn condition evaluation system comprising:

7. 7. The grinding burn state evaluation system according to claim 6, further comprising a coolant supply amount optimization unit that optimizes the amount of coolant supplied to the workpiece based on the evaluation result of the final state evaluation unit.

8. The coolant supply amount optimization unit If the evaluation result in the final state evaluation unit indicates that there is grinding burn on the processed part, the flow rate of the coolant supplied to the processed part is increased; When the evaluation result in the final state evaluation unit indicates that there is no grinding burn on the processed portion, the flow rate of the cooling liquid is reduced, 8. The grinding burn state evaluation system according to claim 7, wherein the amount of coolant supplied to the workpiece is optimized by repeatedly increasing and / or decreasing the flow rate of the coolant based on the evaluation results in the final state evaluation unit.

9. a processing condition adjusting unit that adjusts the processing conditions based on the evaluation result of the final state evaluating unit; The processing condition adjustment unit When the evaluation result in the final state evaluation unit indicates that there is grinding burn on the processed portion, the tool feed rate or the tool spindle rotation speed of the grinding machine is reduced; When the evaluation result in the final state evaluation unit indicates that there is no grinding burn on the processed portion, the tool feed rate or the tool spindle rotation speed of the grinding machine is increased, 7. The grinding burn state evaluation system according to claim 6, wherein the machining conditions are optimized by repeatedly increasing and / or decreasing the tool feed rate or the tool spindle rotation speed based on the evaluation result in the final state evaluation unit.

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