JP5821617B2 - Grinding state determination method and grinding state determination device - Google Patents

Description

  The present invention relates to a method for determining a grinding state and an apparatus for determining a grinding state in grinding a workpiece.

  For example, Japanese Patent Laying-Open No. 2003-291064 (Patent Document 1) describes a method of determining a grinding state by detecting a grinding feed rate of a grinding wheel in grinding a workpiece. In other words, when constant power control is performed so that the motor power of the grinding wheel becomes the target power, the grinding feed speed decreases as the grinding ability of the grinding wheel decreases, so the grinding feed speed of the grinding wheel during the roughing process is detected. When the detected grinding feed rate of the grinding wheel is low, it is determined that the grinding ability of the grinding wheel has decreased, and the target power during the finishing process is set low.

Japanese Patent Laid-Open No. 2003-291064

  Generally, when a grinding wheel surface of a grinding wheel is damaged during grinding of a workpiece, the motor power of the grinding wheel tends to increase. In such a case, in the grinding state determination method described in Patent Document 1, constant power control is performed so that the motor power of the grinding wheel that has been increased is lowered to become the target power. For this reason, it will enter into a finishing process, with the grindstone surface of a grinding wheel damaged, and there exists a possibility that the surface roughness of a finished product may deteriorate.

  This invention is made in view of such a situation, and it aims at providing the grinding state determination method and grinding state determination apparatus which can determine the state of the grindstone surface etc. of a grinding wheel with high precision. To do.

(Grinding condition judgment method)
(Claim 1) The grinding state determination method of the present invention uses a grinding machine that grinds the workpiece by relatively moving the workpiece and the grinding wheel, and the grinding wheel surface state of the grinding wheel is set as a grinding state. In the grinding state judging method for judging, the value obtained based on the grinding feed speed of the grinding wheel within a predetermined control range within the constant load control for controlling the grinding load when grinding the workpiece at a constant speed relationship. A speed relationship value calculation step to be obtained as a value, a tolerance value setting step for setting a tolerance value of the speed relationship value at which the grinding wheel surface of the grinding wheel as the grinding state is in a good state , the speed relationship value, and And a grinding state determination step for determining a grinding state based on the allowable value.

  (Claim 2) The grinding state determination method includes a first feed speed detecting step of detecting a grinding feed speed of the grinding wheel at an arbitrary first time point within the constant load control as a first feed speed; A second feed rate detecting step of detecting a grinding feed rate of the grinding wheel at a second time point within the constant load control after the time point as a second feed rate, wherein the speed relation value calculating step comprises A difference in feed speed between the first feed speed and the second feed speed may be obtained as the relation value.

  (Claim 3) The grinding state determination method includes a first time point detecting step for detecting an arbitrary first time point in the constant load control, and a grinding feed speed of the grinding wheel at the first time point as a first feed speed. A first feed rate detecting step that detects the second time point in the constant load control after the first time point, and a grinding feed rate of the grinding wheel at the second time point. A second feed rate detecting step for detecting the second feed rate, wherein the speed related value calculating step includes a feed rate difference between the first feed rate and the second feed rate as the speed related value, and the first The acceleration may be obtained from the time difference between the first time point and the second time point.

  (Claim 4) The first time point may be a start time of the constant load control.

  (Claim 5) Further, the first time point may be a start time of the constant load control, and the second time point may be an end time of the constant load control.

  (Claim 6) The grinding state determination method includes a minimum feed rate setting step of setting a minimum feed rate of a grinding feed rate of the grinding wheel, and the grinding state determination step includes the first feed rate and the minimum feed rate. The grinding state is determined based on the feed rate, the grinding state is determined based on the second feed rate and the minimum feed rate, and then the grinding state is determined based on the speed-related value and the allowable value. You may make it do.

  (Claim 7) The grinding state determination method may be applied in rough grinding of the workpiece.

(Grinding state judgment device)
(Claim 8) The grinding state determination apparatus of the present invention uses a grinding machine for grinding the workpiece by relatively moving the workpiece and the grinding wheel, and sets the state of the grinding wheel surface of the grinding wheel as a grinding state. In the grinding state judgment device for judging, the value obtained based on the grinding feed speed of the grinding wheel within a predetermined control range within the constant load control for controlling the grinding load when grinding the workpiece constant. A speed relation value calculating means to be obtained as a value, an allowable value setting means for setting an allowable value of the speed relation value, the speed relation value at which the state of the grinding wheel surface of the grinding wheel as the grinding state is good, and Grinding state determination means for determining a grinding state based on the allowable value.

  (Claim 1) In grinding a workpiece, for example, when the grinding wheel surface of the grinding wheel hits the workpiece and the grinding wheel surface is damaged, the grinding feed speed changes greatly. Therefore, as in the grinding state determination method of the present invention, an allowable value of the speed related value related to the grinding feed speed of the grinding wheel within a predetermined control range within the constant load control is set. As a result, when the speed-related value deviates from the allowable value, the grinding feed speed has changed greatly. Therefore, it is possible to determine with high accuracy that the state of the grinding wheel surface of the grinding wheel is defective. It is possible to prevent continuation of grinding by the grinding wheel whose surface is damaged.

  (Claim 2) Thereby, the state of the grindstone surface of the grinding wheel at the start point and the end point of an arbitrary control range in the constant load control can be determined with high accuracy.

  (Claim 3) Thereby, the state of the grinding wheel surface of the grinding wheel within an arbitrary control range in the constant load control can be determined with high accuracy.

  (Claim 4) Since the grinding wheel surface of the grinding wheel is normal at the start of constant load control, the state of the grinding wheel surface of the grinding wheel at a later time is determined by using the starting point of constant load control as a reference. Can be determined with high accuracy.

  (Claim 5) Thereby, the state of the grinding wheel surface of the grinding wheel within the entire control range of the constant load control can be determined with high accuracy.

  (Claim 6) Thereby, even if the speed-related value is within the range of the allowable value, when at least one of the first feed speed and the second feed speed is less than the minimum feed speed, the grinding wheel surface of the grinding wheel, etc. It can be determined that the state of is bad.

  (Claim 7) By applying the grinding state determination method in rough grinding of a workpiece, it is possible to prevent finish grinding by a grinding wheel whose surface is damaged.

  (Embodiment 8) According to the grinding state judging device of the present invention, the same effect as the above-described grinding state judging method is obtained. Further, other characteristic portions in the grinding state determination method can be similarly applied to the grinding state determination device of the present invention. And the same effect is produced.

It is a top view of a grinding machine. Embodiment: It is a functional block diagram of a grinding state determination apparatus. Embodiment: It is a flowchart of a grinding state determination program. It is a figure which shows the relationship between the grinding time and grinding load in a grinding cycle, and the relationship between grinding time and a grinding feed rate. The history display state of the screen of the display device is shown. It is a figure which shows the relationship between the grinding time for demonstrating the deformation | transformation aspect of the determination method of a grinding state, and a grinding feed rate. It is a figure which shows the relationship between the grinding time and grinding feed speed for demonstrating another deformation | transformation aspect of the determination method of a grinding state.

(1. Machine configuration of grinding machine)
As an example of the grinding machine 1, a headstock traverse type internal grinding machine will be described as an example and described with reference to FIG. 1. A case where the workpiece W to be ground by the grinding machine 1 is used as an outer ring of a bearing and the inner peripheral raceway surface of the outer ring of the bearing is ground using the grinding machine 1 will be described as an example. Here, a case where a plurality of workpieces W of the same type are ground, that is, a case where a workpiece W as a mass-produced product is manufactured will be described.

  As shown in FIG. 1, a grinding machine 1 includes a bed 10, a table 20, a headstock 30, a grindstone support device 40, a proximity switch 50, a control device 60, a contact detection sensor 80, and a sizing device. 90 and a grinding wheel molding device (not shown).

  The bed 10 has a substantially rectangular shape and is disposed on the floor. However, the shape of the bed 10 is not limited to a rectangular shape. A pair of Z-axis guide rails 11a and 11b are formed on the upper surface of the bed 10 so as to extend in the left-right direction (Z-axis direction) in FIG. The pair of Z-axis guide rails 11a and 11b are rails on which the table 20 can slide. Further, the bed 10 is provided with a Z-axis ball screw 11c for driving the table 20 in the left-right direction in FIG. 1 between the pair of Z-axis guide rails 11a and 11b. A Z-axis motor 11d that rotates is disposed.

  Further, on the upper surface of the bed 10, a pair of X-axis guide rails 12a and 12b on which the grindstone base 42 can slide are formed so as to extend in the vertical direction (X-axis direction) in FIG. Has been. Further, the bed 10 is provided with an X-axis ball screw 12c between the pair of X-axis guide rails 12a and 12b for driving the grinding wheel base 41 in the vertical direction in FIG. 1, and this X-axis ball screw 12c. An X-axis motor 12d that rotates the motor is disposed.

  The table 20 is formed in a long rectangular flat plate shape, and is slidably disposed on the pair of Z-axis guide rails 11 a and 11 b in the upper surface of the bed 10. The table 20 is connected to a nut member of the Z-axis ball screw 11c, and moves along the pair of Z-axis guide rails 11a and 11b by driving the Z-axis motor 11d. The Z-axis motor 11d has an encoder, and the encoder can detect the rotation angle of the Z-axis motor 11d.

  The headstock 30 is provided on the upper surface of the table 20 and supports the workpiece W in a rotatable manner. Specifically, the head stock 30 includes a head stock main body 31, a magnet chuck 32, a shoe 33, and a main shaft motor 34. The headstock body 31 is fixed to the left side of FIG. The headstock body 31 is provided with a magnet chuck 32 that can rotate about the Z-axis. The magnet chuck 32 attracts and holds a bearing, which is a workpiece W, by a magnetic force. The shoe 33 and the magnet chuck 32 are provided on the headstock 30, and the workpiece W is positioned by supporting the side surface of the workpiece W by the shoe 33. The magnet chuck 32 is rotationally driven with respect to the head stock body 31 by the main shaft motor 34. The main shaft motor 34 has an encoder, and the rotation angle of the main shaft motor 34 can be detected by the encoder.

  The grinding wheel support device 40 includes a grinding wheel base 41, a grinding wheel driving motor 42, and a grinding wheel 43. The grinding wheel base 41 is slidably disposed on the pair of X-axis guide rails 12a and 12b on the upper surface of the bed 10. The grindstone base 41 is connected to the nut member of the X-axis ball screw 12c, and moves along the pair of X-axis guide rails 12a and 12b by driving the X-axis motor 12d.

  A grinding wheel driving motor 42 is fixed to an end surface of the grinding wheel head 41 in the X-axis direction on the head stock 30 side. At the tip of the grinding wheel drive motor 42, a grinding wheel 43 for grinding the inner peripheral raceway surface of the bearing outer ring, which is the workpiece W, is provided. That is, the grinding wheel 43 is attached to the grinding wheel base 41 so as to be rotatable around the Z axis.

  The proximity switch 50 is a switch that is provided on the upper surface of the bed 10 and detects the start and end of the grinding cycle of the bearing outer ring that is the workpiece W by the grinding wheel 43. That is, the proximity switch 50 determines that the grinding cycle starts when the grinding wheel base 41 approaches the proximity switch 50 and the Z-axis direction separation distance between the proximity switch 50 and the grinding wheel base 41 becomes equal to or less than the set value. On the other hand, the proximity switch 50 determines that the grinding cycle is completed when the grinding wheel base 41 is moved away from the proximity switch 50 and the Z-axis direction separation distance between the proximity switch 50 and the grinding wheel base 41 exceeds a set value.

  The contact detection sensor 80 is a sensor that is provided on the side surface of the headstock body 31 and detects the start of grinding of the bearing outer ring that is the workpiece W by the grinding wheel 43. That is, when the grinding wheel 43 contacts the workpiece W, the contact detection sensor 80 detects the contact and determines that grinding is started. For example, an AE sensor is used as the contact detection sensor 80.

  The sizing device 90 is provided on the upper surface of the table 20, and measures the inner diameter of the workpiece W at the grinding feed position when the grinding wheel 43 is grinding the inner peripheral raceway surface of the bearing outer ring which is the workpiece W. It is. This sizing device 90 is configured such that an L-shaped arm 91 extending from the device main body can be moved in the left-right direction and the vertical direction in FIG. It is configured to be able to always contact the inner peripheral raceway surface of the bearing outer ring.

  The grinding wheel molding device (not shown) is a dresser that is provided on the headstock 30 or the bed 10 and molds the outer peripheral surface of the grinding wheel 43, for example. The grinding wheel 43 dressed by this grinding wheel molding device is in a state of good sharpness and is formed in a desired shape.

  The control device 60 controls each motor to rotate the workpiece W around the Z axis, rotate the grinding wheel 43, and make the workpiece W and the grinding wheel 43 relative to each other in the Z axis direction and the X axis direction. By moving, the grinding of the inner peripheral raceway surface of the bearing outer ring which is the workpiece W is controlled. Here, as shown in FIG. 4, the grinding cycle is generally performed in the order of air polishing, rough polishing, finishing, and spark-out. And in RAR, there is also a process which is divided into first RAR and second RAR, and in the first rough process, the black skin is mainly removed. The control device 60 performs constant load control for controlling the grinding load on the workpiece W to be constant in the second roughing process. Since the grinding load has a relationship that increases as the driving power of the grinding wheel driving motor 42 increases, the control device 60 performs constant power control based on the driving power of the grinding wheel driving motor 42.

  In this embodiment, the driving power of the grinding wheel driving motor 42 is used as the grinding load. In addition to this, the current value of the grinding wheel driving motor 42 and the relative movement between the grinding wheel 43 and the workpiece W are determined. The current value and power value of the X-axis motor 12d to be performed, the current value and power value of the spindle motor 34 that drives the workpiece W to be rotatable, the amount of deflection deformation of the grinding wheel 43 or the support portion of the workpiece W, and the like are used. it can.

  Further, as the grinding load, the deformation amount of the grinding part in the workpiece W, that is, the deflection displacement amount of the workpiece W caused by being pressed against the grinding wheel 43 can be used. This is because the amount of deflection displacement depends on the grinding load. The deflection displacement amount of the grinding part in the workpiece W is measured by, for example, a displacement sensor.

  Moreover, the temperature of the grinding site | part of the workpiece W can be used as a grinding load. This is because the temperature depends on the grinding load. However, it is not easy to measure the temperature of the workpiece W in contact with the grinding wheel 43, that is, the temperature of the grinding point. Therefore, the temperature of the portion of the workpiece W having a phase shifted from the grinding point (contact point with the grinding wheel 43) in the grinding portion (inner peripheral surface or outer peripheral surface) is measured. The temperature of the grinding part of the workpiece W differs depending on the phase deviated from the grinding point and the phase deviated from the grinding point, but the phase temperature deviated from the grinding point is a value corresponding to the temperature of the grinding point. Therefore, even a phase shifted from the grinding point can be measured sufficiently. And the temperature of the phase shifted | deviated from the grinding point among the grinding | polishing parts of the workpiece W is measured with the contact-type temperature sensor made to contact the said site | part, or the non-contact-type temperature sensor made non-contact with the said site | part.

  The control device 60 compares the value relating to the grinding feed speed of the grinding wheel 43 (speed related value) with the allowable value of the speed related value in the second roughing process under constant load control, and determines the grinding state. A determination device 70 is provided. However, the grinding state determination device 70 is not limited to the one provided inside the control device 60, and can also be applied as an external device. In addition, although this embodiment demonstrates the grinding state determination apparatus 70 which determines a grinding state in a 2nd rough process, it is good also as a grinding state determination apparatus which determines a grinding state in a finishing process.

(2. Explanation of grinding condition, grinding wheel speed-related values and allowable values)
Next, the grinding state determined by the grinding state determination device 70, the speed relationship value of the grinding wheel calculated by the grinding state determination device 70, and the allowable value set in the grinding state determination device 70 will be described. The grinding state includes the state of the grinding wheel surface of the grinding wheel 43, that is, whether or not damage has occurred on the grinding wheel surface, and the processing state, that is, presence or absence of coolant, occurrence of abnormality such as the shape and hardness of the workpiece W, and the like. is there.

As shown in FIG. 4, the speed relation value obtained based on the grinding feed speed of the grinding wheel 43 is the start time Ts (second stage) of the second roughing process in which the driving power of the grinding wheel driving motor 42 is controlled to be constant. 1) between the start feed speed Vs (first feed speed) of the grinding wheel 43 and the end feed speed Ve (second feed speed) of the grinding wheel 43 at the end time Te (second time) of the second roughing process. There is a feed speed difference ΔV. Further, there is an acceleration a obtained from a feed speed difference ΔV between the start feed speed Vs and the end feed speed Ve and a time difference ΔT between the start time Ts and the end time Te. Further, there is a minimum feed speed Vmin that is a minimum grinding feed speed at which grinding by the grinding wheel 43 is possible. As the allowable value of the speed related value, there is an allowable value dV of the feed speed difference ΔV or an allowable value da of the acceleration a that can keep the grinding state actually measured by the operator in a good state.

(3. Configuration of grinding state determination device)
Next, the grinding state determination device 70 will be described with reference to the functional block diagram of FIG. Here, in describing the grinding state determination device 70, FIG. 2 also describes a partial configuration of the grinding machine 1 described above. Here, in FIG. 2, the same code | symbol is attached | subjected about the structure same as the structure of the grinding machine 1 of FIG. The grinding wheel driving motor 42 is provided with a motor wattmeter 42a for measuring the driving power of the grinding wheel driving motor 42. Instead of the motor wattmeter 42a, the power value may be directly collected by a motor amplifier of the grinding wheel driving motor 42.

  The grinding state determination device 70 includes a grinding feed speed reading unit 71, a grinding time reading unit 72, a speed relation value calculation unit 73, an allowable value storage unit 74, a grinding state determination unit 75, and an output unit 76. Configured.

  The grinding feed rate reading unit 71 reads the grinding feed rate of the grinding wheel 43 from the control device 60. The grinding time reading unit 72 reads the grinding time by the grinding wheel 43 from the control device 60. The speed relation value calculation unit 73 calculates a speed relation value based on the grinding feed rate read by the grinding feed rate reading unit 71 and the grinding time read by the grinding time reading unit 72 if necessary. The allowable value storage unit 74 stores the allowable value of the speed related value. The grinding state determination unit 75 compares the speed relationship value calculated by the speed relationship value calculation unit 73 with the allowable value of the speed relationship value stored in the allowable value storage unit 74 to determine the grinding state.

  The output unit 76 performs display processing on the screen of the display device 81, printing processing by the printing device 82, storage processing in the storage device 83, or communication output to an external device by the communication device 84 with respect to the grinding state information. . The output is selected by the operator. Thereby, the operator can grasp | ascertain a grinding state reliably by the output form selected by the operator about the information regarding a grinding state.

(4. Processing by grinding state determination device)
Next, execution of the grinding state determination program by the grinding state determination device 70 will be described with reference to FIG. As shown in FIG. 4 as an example, the grinding state determination program calculates the start feed speed Vs and the end feed speed Ve of the grinding wheel 43 at the start time Ts and the end time Te of the second roughing process in which constant load control is performed. Reading, comparing each feed rate Vs, Ve and the minimum feed rate Vmin to determine the grinding state, and further comparing the feed rate difference ΔV between each feed rate Vs, Ve and the allowable value dV to determine the grinding state. . This will be described in detail below.

  As shown in FIG. 3, it is determined whether or not an allowable value dV of the feed speed difference ΔV is already stored as a speed related value (step S1). If not yet stored, the allowable value dV of the feed speed difference ΔV is read (step S2).

  If the allowable value dV of the feed speed difference ΔV is stored, the grinding cycle is started (step S3). When the grinding cycle is started, as shown in FIG. 2, the control device 60 drives each motor and starts grinding the inner circumferential raceway surface of the bearing outer ring as the workpiece W by the grinding wheel 43. More specifically, after starting the grinding cycle, as shown in FIG. 1, the grinding wheel base 41 is moved to the reference position (see FIG. 1) toward the position where the grinding wheel 43 can enter the inside of the bearing outer ring, which is the workpiece W, in the radial direction. (Not shown) is moved in the X-axis direction. Then, the grinding wheel 43 enters the radial inner side of the bearing outer ring, which is the workpiece W, by moving the table 20 in the Z-axis direction. Then, the grinding wheel 43 moves in the X-axis direction toward the inner peripheral raceway surface of the bearing outer ring that is the workpiece W, and after detecting contact between the workpiece W and the grinding wheel 43, grinding is started. The workpiece W is ground after the first rough grinding and then the second rough grinding, and then finish grinding. When the grinding is finished, the operation is performed in the reverse order from the start of grinding, the process returns to the reference position, and the grinding cycle is finished.

  When the proximity switch 50 is in an ON state, that is, when a grinding cycle is started, the contact detection sensor 80 detects contact between the workpiece W and the grinding wheel 43, that is, determines whether or not the first roughing process has been started (step S4). ). Then, when the first roughing process is started and executed (step S4: Yes, step S5), the grinding of the predetermined cutting amount of the first roughing process set in advance is completed and the second roughing process is started. It is determined whether or not (step S6). Specifically, based on the inner diameter of the workpiece W read from the sizing device 90 by the grinding feed rate reading unit 71 of FIG. 2, whether or not grinding of a predetermined cutting amount in the first roughing process is completed. judge. Alternatively, after the contact with the workpiece W is detected by the contact detection sensor 80, it is determined whether or not the first roughing process has been completed based on whether or not the grindstone table 41 has moved by a predetermined depth of cut.

  When the second roughing process is started (step S6: Yes), the start feed speed Vs of the grinding wheel 43 at the start time Ts of the second roughing process is read (step S7). Specifically, the grinding feed rate reading unit 71 reads the start feed rate Vs of the grinding wheel 43 from the control device 60. Then, it is determined whether or not the starting feed speed Vs of the grinding wheel 43 is less than the minimum feed speed Vmin (step S8). Specifically, the grinding state determination unit 75 in FIG. 2 reads the starting feed speed Vs from the grinding feed speed reading unit 71 and reads the minimum feed speed Vmin from the allowable value storage unit 74 and compares them.

  If the starting feed speed Vs of the grinding wheel 43 is less than the minimum feed speed Vmin (step S8: Yes), it is determined that the grinding state is defective, and the output unit 76 in FIG. Is displayed, and the defect contents are stored in the storage device 83 (step S9). Then, the grinding is stopped (step S10). Note that dressing of the grinding wheel 43 may be promoted without stopping grinding.

  On the other hand, when the starting feed speed Vs of the grinding wheel 43 is equal to or higher than the minimum feed speed Vmin (step S8: No), the second roughing process is executed (step S11). And it is determined whether the 2nd rough process was complete | finished (step S12). Specifically, the grinding feed speed reading unit 71 determines whether or not the inner diameter of the workpiece W read from the sizing device 90 has reached the dimension at the end of the second roughing process. Alternatively, in consideration of the grinding wheel diameter of the grinding wheel 43, it is determined whether or not the second roughing process has been completed based on whether or not grinding has been completed when the grinding wheel base 41 has reached a predetermined position.

  When the second roughing process is finished (step S12: Yes), the end feed speed Ve of the grinding wheel 43 at the end time Te of the second roughing process is read (step S13). Then, it is determined whether or not the end feed speed Ve of the grinding wheel 43 is less than the minimum feed speed Vmin (step S14). When the end feed speed Ve of the grinding wheel 43 is less than the minimum feed speed Vmin (step S14: Yes), it is determined that the grinding state is defective, and the output unit 76 in FIG. Is displayed, and the defect contents are stored in the storage device 83 (step S9). Then, the grinding is stopped (step S10). Note that dressing of the grinding wheel 43 may be promoted without stopping grinding.

  On the other hand, when the end feed speed Ve of the grinding wheel 43 is equal to or higher than the minimum feed speed Vmin (step S14: No), the feed speed between the start feed speed Vs and the end feed speed Ve as the speed-related value of the grinding wheel 43. The difference ΔV is calculated (step S15), and it is determined whether or not the feed speed difference ΔV is within the allowable value dV (step S16). When the feed speed difference ΔV is outside the allowable value dV (step S14: No), it is determined that the grinding state is defective, and the defect content is displayed on the display device 81 by the output unit 76 of FIG. The defect contents are stored in the device 83 (step S9). Then, the grinding is stopped (step S10). Note that dressing of the grinding wheel 43 may be promoted without stopping grinding.

  On the other hand, when the feed speed difference ΔV is within the allowable value dV (step S14: Yes), the finishing process is executed (step S17). Then, it is determined whether or not the finishing process has been completed (step S18). If the finishing process has been completed, it is determined whether or not the proximity switch 50 is in an OFF state, that is, whether the grinding cycle has been completed (step S19). . When the grinding cycle is completed, it is determined whether or not there is a next workpiece W (step S20). If there is a next workpiece W, the installation of the workpiece W is set up ( The process is repeated from step S21) and step S3. On the other hand, if there is no next workpiece W, grinding is stopped (step S10).

  In step S15, the grinding state is determined by calculating the feed speed difference ΔV between the start feed speed Vs and the end feed speed Ve as the speed related value of the grinding wheel 43. However, the start feed speed Vs and the end feed speed Ve are determined. The acceleration a obtained from the feed speed difference ΔV and the time difference ΔT between the start time Ts and the end time Te is calculated and compared with the allowable value da, and the grinding state is determined in the same manner as the feed speed difference ΔV. Also good. In this case, in steps S7 and S15, the grinding time reading unit 72 shown in FIG. 2 reads the start time Ts and the end time Te of the second roughing process from the control device 60, and the grinding feed speed reading unit 71 reads the grinding time reading unit 72. , The start time Ts and the end time Te of the second roughing process are read to calculate the acceleration a.

  Further, the comparison process of the start feed speed Vs and the end feed speed Ve and the minimum feed speed Vmin in steps S8 and S14 is omitted, and the grinding state is determined only by the comparison process of the feed speed difference ΔV and the allowable value dV. It may be configured.

(5. History display status of display device screen)
Next, the history display state of the screen of the display device 81 will be described with reference to FIG. When a grinding state failure occurs due to the execution of the grinding state determination program in FIG. 3 (steps S 8, 14, and 16 in FIG. 3), the content of the failure is stored in the storage device 83. The storage device 83 may store not only defective contents but also good contents. When a large number of workpieces W are ground, the past failure history is stored in the storage device 83. Moreover, it turns out that the workpiece W which is not memorize | stored as a grinding defect is favorable. Further, when good contents are stored in the storage device 83, it is possible to grasp the work W that is good directly.

  If it does so, as shown in FIG. 5, it will be displayed on the screen of the display apparatus 81 whether the grinding state is favorable about all the workpieces W. Thus, by storing the past history of information related to the grinding state, the tendency of the grinding state can be grasped. Therefore, by using the tendency of the grinding state, it is possible to predict a sign of occurrence of a grinding state defect when performing future grinding. As a result, appropriate measures can be determined for future grinding.

(6. Modifications)
In the above-described embodiment, grinding is performed by reading the grinding feed speed of each grinding wheel 43 at the start time Ts of the constant load control as the first time when the constant load control is performed and at the end time Te of the constant load control as the second time. Although the state has been determined, it is also possible to determine the grinding state by reading the grinding feed speed of the grinding wheel 43 at each point of time as the first point of time and the second point of time during the constant load control. Further, for example, as shown in FIG. 6, the grinding state may be determined by repeatedly reading the grinding feed speeds V1 and V2 of the grinding wheel 43 at arbitrary time points T1 and T2 at regular intervals ΔT. This is because the grinding feed speed during the constant load control does not always change constantly, but may change rapidly or may change finely.

  For example, as shown in FIG. 7, the grinding feed speed Vs of the grinding wheel 43 at the start time Ts of the constant load control is read as the first time point, and the grinding wheel 43 at the arbitrary time Tn of the constant load control is read as the second time point. The grinding feed speed Vn may be read to determine the grinding state. Since the grinding wheel surface of the grinding wheel 43 is still normal at the start time Ts of the constant load control, the state of the grinding wheel surface and the like of the grinding wheel 43 at a later time is based on the starting time Ts of the constant load control. This is because it can be determined with high accuracy.

  Moreover, although the grinding state in the case of grinding the inner peripheral surface of the workpiece W as the grinding part of the workpiece W by the grinding wheel 43 is determined, the outer peripheral surface of the workpiece W and other workpieces are ground. The grinding state can also be determined.

(7. Effect of grinding state judgment processing)
In grinding the workpiece W, for example, if grinding is continued in a state where the grinding wheel surface of the grinding wheel 43 hits the workpiece W and the grinding wheel surface is damaged, the grinding feed speed changes greatly. Therefore, an allowable value of a speed related value related to the grinding feed speed of the grinding wheel 43 within a predetermined control range within the constant load control is set. For example, the allowable value dV of the feed speed difference ΔV between the start feed speed Vs of the grinding wheel 43 at the start time Ts of the second roughing process and the end feed speed Ve of the grinding wheel 43 at the end time Te of the second roughing process is set. To do. As a result, when the feed speed difference ΔV deviates from the allowable value dV, the grinding feed speed has changed greatly, so that it is determined with high accuracy that the state of the grinding wheel surface of the grinding wheel 43 is defective. It is possible to prevent continuation of grinding by the grinding wheel 43 whose grinding wheel surface is damaged.

1: grinding machine 10: bed, 11a, 11b: Z-axis guide rail, 11c: Z-axis ball screw 11d: Z-axis motor, 12a, 12b: X-axis guide rail, 12c: X-axis ball screw 12d: X-axis motor 20 : Table 30: Spindle base, 31: Main spindle body, 32: Magnet chuck, 33: Shoe 34: Spindle motor 40: Grinding wheel support device, 41: Grinding wheel base, 42: Grinding wheel drive motor 42a: Motor wattmeter, 43 : Grinding wheel 50: proximity switch, 60: control device, 80: contact detection sensor, 90: sizing device 70: grinding state determination device, 71: grinding feed rate reading unit, 72: grinding time reading unit 73: speed related value Calculation unit 74: Allowable value storage unit 75: Grinding state determination unit 76: Output unit

Claims (8)

In the grinding state determination method for determining the state of the grinding wheel surface of the grinding wheel as a grinding state using a grinding machine that grinds the workpiece by relatively moving the workpiece and the grinding wheel ,
A speed relation value calculation step for obtaining a value obtained based on a grinding feed speed of the grinding wheel within a predetermined control range as a speed relation value in constant load control for controlling the grinding load at a constant time when grinding the workpiece. When,
An allowable value setting step for setting an allowable value of the speed-related value at which the state of the grinding wheel surface of the grinding wheel as the grinding state is in a good state ;
A grinding state determination step of determining the grinding state based on the speed relation value and the allowable value;
A grinding state determination method comprising: In claim 1,
The grinding state determination method includes:
A first feed rate detecting step of detecting a grinding feed rate of the grinding wheel at an arbitrary first time point within the constant load control as a first feed rate;
A second feed rate detecting step of detecting a grinding feed rate of the grinding wheel at a second time point within the constant load control after the first time point as a second feed rate;
With
The speed relation value calculating step is a grinding state determination method for obtaining a feed speed difference between the first feed speed and the second feed speed as the speed relation value. In claim 1,
The grinding state determination method includes:
A first time point detecting step of detecting an arbitrary first time point within the constant load control;
A first feed rate detecting step of detecting a grinding feed rate of the grinding wheel at the first time point as a first feed rate;
A second time point detecting step of detecting a second time point in the constant load control after the first time point;
A second feed rate detecting step of detecting a grinding feed rate of the grinding wheel at the second time point as a second feed rate;
With
In the speed relation value calculating step, a grinding state determination method for obtaining acceleration as a speed relation value from a feed speed difference between the first feed speed and the second feed speed and a time difference between the first time point and the second time point. . In claim 2 or 3,
The grinding state determination method, wherein the first time point is a start time of the constant load control. In claim 2 or 3,
The grinding state determination method, wherein the first time point is a start time of the constant load control, and the second time point is an end time of the constant load control. In any one of Claims 2-5,
The grinding state determination method includes:
A minimum feed rate setting step for setting a minimum feed rate of the grinding feed rate of the grinding wheel,
With
The grinding state determination step determines a grinding state based on the first feed speed and the minimum feed speed, determines a grinding state based on the second feed speed and the minimum feed speed, and then A grinding state determination method for determining a grinding state based on a speed relation value and the allowable value. In any one of Claims 1-6,
The grinding state determination method is a grinding state determination method applied in rough grinding of the workpiece. In a grinding state determination device that determines the state of the grinding wheel surface of the grinding wheel as a grinding state using a grinding machine that grinds the workpiece by relatively moving the workpiece and the grinding wheel ,
Speed relation value calculation means for obtaining, as a speed relation value, a value obtained based on the grinding feed speed of the grinding wheel within a predetermined control range within constant load control for controlling the grinding load when grinding the workpiece at a constant level. When,
An allowable value setting means for setting an allowable value of the speed relation value at which the state of the grinding wheel surface of the grinding wheel as the grinding state is in a good state ;
A grinding state determination means for determining a grinding state based on the speed relation value and the allowable value;
A grinding state determination apparatus comprising:

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