Trimming device

Abstract

A dressing device includes a detector that detects at least one of a surface condition evaluation value that indicates a surface condition of a workpiece in an axial direction and an outer diameter evaluation value that indicates an outer diameter at a plurality of axial positions; a calculation unit that calculates a shape deterioration degree from a reference surface condition on a grindstone based on the evaluation value corresponding to a surface condition of the workpiece detected by the detector; a determination unit that determines at least one of whether or not dressing of the grindstone is possible and whether or not a condition for changing the dressing is possible based on the shape deterioration degree; and a performing unit that performs the dressing of the grindstone based on a determination result of the determination unit.

Description

Technical Field

[0001] This invention relates to a trimming device. Background Technology

[0002] In a grinding machine that grinds a workpiece while rotating it over a grinding stone, the grinding stone is dressed to restore its original shape. Dressing is generally performed after a predetermined number of workpiece grinding passes. The shape of the grinding stone is affected by the number of workpiece grinding passes, but to avoid producing defective workpieces, a margin of safety is set. Therefore, this margin becomes a significant factor in reducing the lifespan of the grinding stone. To achieve stable workpiece quality, it is desirable to extend the lifespan of the grinding stone.

[0003] Japanese Patent Application Publication No. 10-000556 describes obtaining a specific frequency that is an integer multiple of the rotational frequency of the grinding stone during the vibration of a grinding machine, and determining the dressing period and the quality of dressing based on the amplitude of this vibration. Furthermore, Japanese Patent Application Publication No. 2000-263437 describes that if the current value of the motor driving the rotation of the grinding stone exceeds a threshold, it is determined that the sharpness of the grinding stone has deteriorated, and grinding stone finishing is performed. Summary of the Invention

[0004] This invention provides a dressing device that can stabilize workpieces and extend the life of grinding stones through a different method than before.

[0005] The dressing apparatus comprises: a detector that, as an evaluation value representing the surface condition of a workpiece having a central axis, detects at least one of a surface condition evaluation value representing the surface characteristics of the workpiece in the axial direction and an outer diameter evaluation value representing the outer diameter at a plurality of axial positions; a calculation unit that, based on the at least one evaluation value corresponding to the surface condition of the workpiece detected by the detector, calculates the degree of shape damage on a grinding stone configured to grind the workpiece, calculated from a reference surface condition; a determination unit that, based on the degree of shape damage, determines whether dressing the grinding stone can be performed and whether at least one of the conditions for dressing can be changed; and an execution unit that performs the dressing of the grinding stone based on the determination result of the determination unit.

[0006] As an evaluation value representing the surface condition of a workpiece, at least one evaluation value, including a surface texture evaluation value and an outer diameter evaluation value, is used. This evaluation value represents the surface condition of the workpiece itself. Furthermore, since the surface condition of the grinding stone is transferred onto the surface of the workpiece, this evaluation value represents the surface condition of the grinding stone.

[0007] Therefore, the calculation unit uses this evaluation value, which indirectly represents the surface condition of the grinding stone, to calculate the degree of shape damage to the grinding stone. Then, based on the calculated degree of shape damage, the determination unit determines at least one of whether repair can be performed or whether the repair conditions can be changed. Therefore, by performing repair based on the degree of shape damage of the grinding stone, which is indirectly evaluated based on the surface condition of the workpiece, it is possible to stabilize the quality of the workpiece and extend the lifespan of the grinding stone. Attached Figure Description

[0008] Figure 1 This is a top view showing an example of a grinding machine.

[0009] Figure 2 This is a functional block diagram of the trimming device.

[0010] Figure 3 This is a graph showing the shift in the grinding stone condition level relative to the number of grinding operations on the workpiece W during the first case processing in the judgment and execution sections.

[0011] Figure 4 This is a flowchart representing the first instance of processing in the decision-making section.

[0012] Figure 5 This is a graph showing the shift in the grinding stone condition level relative to the number of grinding operations on the workpiece W during the second example processing in the judgment and execution sections.

[0013] Figure 6 This is a flowchart representing the second instance of the decision-making process.

[0014] Figure 7 This is a graph showing the shift in the grinding stone condition level relative to the number of grinding operations on the workpiece W during the third case processing in the judgment and execution sections.

[0015] Figure 8 This is a flowchart representing the third instance processing in the decision-making section.

[0016] Figure 9 It is a diagram representing the workpiece.

[0017] Figure 10 This is a graph representing multiple circumferential vibration data used in the calculation of the first surface property evaluation value.

[0018] Figure 11 It is a graph representing surface roughness data.

[0019] Figure 12 It is a graph representing the amount of vibration at multiple axial locations used in the calculation of the first surface property evaluation value.

[0020] Figure 13 It is a graph representing the outer diameter data used in the calculation of the outer diameter evaluation value.

[0021] Figure 14 This is a graph representing the corrected surface roughness data used in the calculation of the third surface property evaluation value.

[0022] Figure 15 It is a graph representing multiple linear surface characteristics used in the calculation of the third surface characteristic evaluation value. Detailed Implementation

[0023] (1. Overview of the trimming device)

[0024] A dressing device is a device for dressing the grinding stone mounted on a grinding machine. A dressing device can be an assembly mounted on the grinding machine or a separate device. In this example, a dressing device is shown that is assembled on a grinding machine.

[0025] (2. Example of grinding machine 10)

[0026] Reference Figure 1 An example of a grinding machine 10 using a dressing device will be described. The grinding machine 10 is a machine tool for grinding a workpiece W and has a structure that allows the workpiece W to move relative to a grinding stone 16. The workpiece W has a central axis, and the grinding stone 16 contacts the workpiece W while the workpiece W is rotated about the central axis, thereby grinding the workpiece W.

[0027] Grinding machine 10 can be used with various structures such as cylindrical grinding machines and cam grinding machines. In this example, a cylindrical grinding machine with a grinding stone table traverse motion is used as an example for grinding machine 10. However, grinding machine 10 can also be used with a table traverse motion. In addition, although the structure for grinding machine 10 is used to grind the outer peripheral surface of workpiece W as an example, the structure for grinding the inner peripheral surface of workpiece W can also be used.

[0028] The grinding machine 10 mainly includes a machine base 11, a spindle seat 12, a tailstock 13, a traverse base 14, a grinding stone seat 15, a grinding stone 16, a dimension determining device 17, a grinding stone correction device 18, and a coolant device 19. Furthermore, the grinding machine 10 includes a detector 21 and a control device 22. In the figure, the Z-axis direction is aligned with the central axis of the workpiece W, the X-axis direction is orthogonal to the Z-axis, and the Y-axis direction is orthogonal to both the X-axis and Z-axis directions.

[0029] The base 11 is fixed to the mounting surface. The spindle seat 12 is disposed on the upper surface of the base 11 near the front side in the X-axis direction. Figure 1 (the lower side) and one end side in the Z-axis direction ( Figure 1 (Left side). The spindle seat 12 supports the workpiece W so that it can rotate about the Z-axis. The workpiece W rotates about its central axis by being driven by a motor 12a provided on the spindle seat 12. The tailstock 13 is provided on the upper surface of the machine base 11 at a position opposite to the spindle seat 12 in the Z-axis direction, that is, near the front side in the X-axis direction. Figure 1(the lower side) and the other end side in the Z-axis direction ( Figure 1 (Right side). That is, the spindle seat 12 and tailstock 13 support both ends of the workpiece W so that the workpiece W can rotate. It should be noted that when the grinding machine 10 is structured to grind the inner circumferential surface of the workpiece W, the workpiece W is supported only by the spindle seat 12.

[0030] The transverse base 14 is disposed on the upper surface of the base 11 in a manner that allows it to move along the Z-axis. The transverse base 14 is moved by a motor 14a disposed on the base 11. The grinding stone holder 15 is disposed on the upper surface of the transverse base 14 in a manner that allows it to move along the X-axis. The grinding stone holder 15 is moved by a motor 15a disposed on the transverse base 14.

[0031] The grinding stone 16 is a tool for grinding workpiece W. In this example, the grinding stone 16 uses a grinding wheel formed in the shape of a disc. The grinding stone 16 is supported by the grinding stone base 15 and is able to rotate. The grinding stone 16 is driven by a motor 16a provided on the grinding stone base 15. The grinding stone 16 has a cylindrical core and an abrasive portion configured to fix multiple abrasive grains to the outer peripheral surface of the cylindrical core by means of an adhesive material. Various materials such as resin and metal can be used as the adhesive material.

[0032] The dimension determining device 17 measures the dimension (diameter) of the workpiece W. The dimension determining device 17 is mounted on the upper surface of the machine base 11 in a manner movable along the Z-axis direction. The position of the dimension determining device 17 in the Z-axis direction is controlled by a feed mechanism 17a mounted on the machine base 11. The dimension determining device 17 includes a detection measuring contact 17b that contacts the grinding surface of the workpiece W. The detection measuring contact 17b is always in contact with the grinding surface of the workpiece W, which rotates during the grinding process.

[0033] The grinding stone correction device 18 corrects the shape of the grinding stone 16. The grinding stone correction device 18 is a device for adjusting (including dressing) the grinding stone 16. Furthermore, the grinding stone correction device 18 also has the function of measuring the size (diameter) of the grinding stone 16.

[0034] Here, "dressing" refers to a shape-reshaping operation, which involves shaping the grinding stone 16 to fit the shape of the workpiece W when the grinding stone 16 is worn due to grinding, and removing the wobble of the grinding stone 16 caused by unilateral wear. "Refurbishment" refers to a reshaping operation, which involves adjusting the protrusion of the abrasive grains or creating cutting edges for the abrasive grains. Refurbishment is an operation that corrects abrasive grain dulling, clogging, abrasive grain loss, etc., and is usually performed after dressing. However, dressing and refurbishment are sometimes performed without particular distinction, so in this specification, "dressing" is used to include the meaning of refurbishment.

[0035] The coolant device 19 supplies coolant to the grinding points of the workpiece W on the grinding stone 16. The coolant device 19 cools the recovered coolant to a specified temperature and supplies it back to the grinding points.

[0036] Detector 21 detects an evaluation value indicating the surface condition of the workpiece W after grinding. The evaluation value indicating the surface condition of the workpiece W is at least one of the following: a surface condition evaluation value indicating the surface characteristics of the workpiece W in the axial direction, and an outer diameter evaluation value related to the outer diameter at multiple axial positions. Detector 21 is used to determine whether the grinding stone 16 can be dressed, whether the dressing conditions can be changed, etc.

[0037] Detector 21 can be applied in either the type that contacts the workpiece W or the type that does not contact the workpiece W. For example, if detector 21 is in the type that contacts the workpiece W, it can be an acceleration sensor that detects the acceleration generated by relative movement relative to the workpiece W while in contact with the surface of the workpiece W. Alternatively, detector 21 can also be a displacement sensor that can detect the distance to the surface of the workpiece W based on a predetermined position. When detector 21 is a displacement sensor, it can be applied in either the type that contacts the workpiece W or the type that does not contact it.

[0038] In this example, detector 21 is used in the dimension determining device 17 as the type that contacts the workpiece W. Detector 21 is an acceleration sensor provided on the arm of the detection measuring contact 17b supporting the dimension determining device 17. As an acceleration sensor, detector 21 outputs acceleration data representing the acceleration detected when the center of the detection measuring contact 17b is in contact with the grinding surface of the rotating workpiece W. It should be noted that detector 21 can also replace the acceleration sensor as a displacement sensor that outputs displacement data representing the displacement value detected when the center of the detection measuring contact 17b is in contact with the grinding surface of the rotating workpiece W.

[0039] The control device 22 controls each drive device based on an NC program generated from motion command data, including the shape of the workpiece W, processing conditions, the shape of the grinding stone 16, and the timing of coolant supply. In other words, the control device 22 receives motion command data and generates an NC program based on that data.

[0040] The control device 22 controls each motor 12a, 14a, 15a, 16a, and the coolant device 19, etc., based on an NC program, thereby performing grinding on the workpiece W. In particular, the control device 22 performs grinding based on the diameter of the workpiece W measured by the size determination device 17 until the workpiece W reaches its finished shape. In addition, the control device 22 controls each motor 14a, 15a, 16a, and the grinding stone correction device 18, etc., when the grinding stone 16 is being corrected, thereby correcting (trimming and finishing) the grinding stone 16.

[0041] (3. Structure of the trimming device 30)

[0042] Reference Figure 2 The structure of the trimming device 30 will be described. For example... Figure 2 As shown, the trimming device 30 includes a detector 31, a calculation unit 32, a determination unit 33, and an execution unit 34. It should be noted that the calculation unit 32, the determination unit 33, and the execution unit 34 are composed of a processor, a storage device, etc., and are implemented by executing a program in the processor.

[0043] The detector 31 uses the detector 21 that constitutes the grinding machine 10. That is, the detector 31 detects an evaluation value representing the surface condition of the workpiece W being ground. The evaluation value representing the surface condition of the workpiece W is at least one evaluation value representing the surface condition evaluation value of the workpiece W in the axial direction and the outer diameter evaluation value of the outer diameter at multiple axial positions.

[0044] The calculation unit 32 calculates the degree of shape damage on the grinding stone 16 of the workpiece W, based on the evaluation value of the surface condition of the workpiece W detected by the detector 31, starting from the reference surface condition. For example, if the reference surface condition of the grinding stone 16 is a straight line parallel to the central axis of the grinding stone 16, the degree of shape damage is the degree of radial deviation from the straight line parallel to the central axis of the grinding stone 16.

[0045] The determination unit 33 determines, based on the degree of shape damage calculated by the calculation unit 32, whether or not the grinding stone 16 can be repaired, and whether or not the repair conditions can be changed. The execution unit 34 performs the repair of the grinding stone 16 based on the determination result of the determination unit 33. The execution unit 34 uses the control device 22 constituting the grinding machine 10. That is, the execution unit 34 functions as part of the control device 22, and performs the repair of the grinding stone 16 by controlling each of the motors 14a, 15a, 16a and the grinding stone correction device 18.

[0046] (4. Examples of decision-making unit 33 and execution unit 34)

[0047] Examples of the determination unit 33 and execution unit 34 constituting the dressing device 30 will be described. It should be noted that, in the following description, the degree of shape damage on the grinding stone 16, calculated by the calculation unit 32 from the reference surface state, is called the grinding stone condition level. The higher the grinding stone condition level, the greater the degree of shape damage, that is, the greater the deviation from the reference shape. Therefore, the grinding stone condition level is lowest immediately after normal dressing, and gradually increases as the workpiece W is ground.

[0048] (4-1. First example)

[0049] Reference Figure 3 as well as Figure 4 The decision unit 33 and the execution unit 34 in the first example will be explained. For example... Figure 3 As shown, the grinding stone condition level L increases with the number of grinding operations on workpiece W. The grinding stone condition level of the first workpiece W is L1(1). The grinding stone condition level of the Nth workpiece is L1(N).

[0050] In addition, Figure 3 In this system, the maximum value for the grinding stone condition level is Lmax, and the grinding stone condition level L must not exceed this maximum value Lmax. Furthermore, under normal conditions of grinding, the grinding stone condition level immediately after grinding is below the minimum threshold Lmin.

[0051] In this example, a predetermined period for repair is set. For instance, the predetermined period for repair is set as the number N of workpieces W counted from the last repair. That is, when the number of workpieces W counted from the last repair reaches N, it is determined that the predetermined period for repair has been reached.

[0052] When the number of workpieces W reaches N, a decision is made based on the grinding stone condition level L1(N) to determine whether the repair period can be postponed relative to the predetermined timeframe. Figure 3 In the process, the grinding stone condition level L1(N) did not exceed the level threshold Lth used for judgment, so the repair period was postponed relative to the predetermined period.

[0053] Subsequently, when the number of workpieces W becomes Na, the delayed grinding stone condition level L1(E) exceeds the level threshold Lth, therefore a trimming is performed. Figure 3 (T1). Moreover, after the repair, as described above, when the number of workpieces W counted from the start of the repair reaches N, it is determined whether a delay in the repair can be carried out. That is, when the total number of workpieces W reaches "Na+N", it is determined whether a delay in the repair can be carried out.

[0054] exist Figure 3 In the initial stage, the grinding stone condition level L2(N) did not exceed the level threshold Lth used for judgment, therefore the repair was postponed relative to the predetermined period. Later, when the number of workpieces W became "Na+Nb", the postponed grinding stone condition level L2(E) exceeded the level threshold Lth, therefore repair was performed. Figure 3 (T2).

[0055] That is, the number of delayed workpieces W corresponds to the grinding stone condition levels L1(N) and L2(N) at the predetermined repair period. Alternatively, the number of delayed workpieces W can be determined corresponding to the grinding stone condition levels L1(N) and L2(N) at the predetermined period.

[0056] Reference Figure 4The first example of the determination process of the determination unit 33 will be explained. First, the determination unit 33 obtains the number Np of the repaired workpieces W (S1). Next, it determines whether the obtained number Np of workpieces W has reached the number N (set number N) corresponding to the predetermined repair period (S2). If it has not reached the set number N (S2: No), it returns to S1.

[0057] On the other hand, when the set quantity N is reached (S2: Yes), the grinding stone condition level L(N) of the Nth workpiece W after finishing is obtained (S3). Next, based on the obtained grinding stone condition level L(N), it is determined whether the finishing period can be extended relative to the set predetermined period (S4). If the extension is decided, the extension amount ΔN is determined. The extension amount ΔN is determined corresponding to the grinding stone condition level L(N) of the set quantity N. For example, the extension amount ΔN can also be determined based on the difference between the grinding stone condition level L(N) of the set quantity N and the maximum value Lmax. Alternatively, the extension amount ΔN can also be determined based on the difference between the grinding stone condition level L(N) of the set quantity N and the level threshold Lth used for determination.

[0058] Next, it is determined whether the number Np of the repaired workpieces W has reached "N+ΔN" (S5). If it has not reached (S5: No), grinding of workpieces W continues until it is reached. On the other hand, if it is reached (S5: Yes), the grinding stone condition level L(Np) of the number Np of workpieces W is obtained (S6).

[0059] Next, it is determined whether the obtained grinding stone condition level L(Np) exceeds the level threshold Lth used for judgment (S7). If it does not exceed (S7: No), the process returns to S6. That is, grinding of workpiece W continues until the level threshold Lth is exceeded. Moreover, if the level threshold Lth is exceeded, it is decided to perform trimming (S8).

[0060] Here, if the determination unit 33 decides to perform repair, the execution unit 34 performs the repair of the grinding stone 16. That is, the execution unit 34 performs the repair of the grinding stone 16 when the delayed repair period has arrived.

[0061] It should be noted that, in the above explanation, when extending the dressing period, the extension amount ΔN is determined. After reaching the extension amount ΔN, the grinding stone condition level L(Np) is compared with the level threshold Lth to determine the dressing execution period. Alternatively, when extending the dressing period is determined, the obtained grinding stone condition level L(Np) can be compared with the level threshold Lth each time the workpiece W is ground to determine the dressing execution period. Alternatively, when extending the dressing period is determined, dressing can be performed when the determined extension amount ΔN is reached.

[0062] In summary, based on the calculated grinding stone condition level L (degree of shape damage), the determination unit 33 determines whether repair can be performed. Therefore, by performing repair based on the degree of shape damage of the grinding stone 16, which is indirectly evaluated using the surface condition of the workpiece W, it is possible to stabilize the quality of the workpiece W and extend the life of the grinding stone 16.

[0063] (4-2. Second example)

[0064] Reference Figure 5 as well as Figure 6 The decision unit 33 and the execution unit 34 in the second example will be explained. Figure 5 In this system, the maximum value for the grinding stone's condition level is Lmax, and the grinding stone condition level L must not exceed this maximum value. Furthermore, a range of grinding stone condition levels is defined, for example, as Lev1, Lev2, Lev3, and Lev4. The grinding stone condition level increases in the order of Lev1, Lev2, Lev3, and Lev4. Additionally, the maximum value of Lev4 is the same as Lmax.

[0065] In this example, a predetermined period for repair is set. For instance, the predetermined period for repair is set as the number N of workpieces W counted from the last repair. That is, when the number of workpieces W counted from the last repair reaches N, it is determined that the predetermined period for repair has been reached.

[0066] If the number of workpieces W reaches N, the determination unit 33 decides to perform dressing of the grinding stone 16. At this time, the dressing conditions are determined corresponding to the grinding stone condition level L(N) before the dressing is to be performed. In this example, the grinding stone condition level range to which the immediately preceding grinding stone condition level L(N) in the grinding stone condition level range Lev1, Lev2, Lev3, Lev4 belongs is determined, and the dressing conditions corresponding to the grinding stone condition level range are changed. For example, the radial cutting amount of the grinding stone 16 is changed as a dressing condition. Furthermore, the execution unit 34 performs dressing based on the changed dressing conditions.

[0067] exist Figure 5 In the above, the Nth grinding stone condition level L1(N) belongs to the grinding stone condition level range Lev2, therefore dressing is performed with the radial cutting amount corresponding to Lev2. Figure 5 The 2Nth grinding stone condition level L2(N) belongs to the grinding stone condition level range Lev4, therefore dressing is performed with the radial cutting amount corresponding to Lev4. Figure 5 (T2). As a result, the grinding stone condition level after T1 and T2 is less than the minimum threshold Lmin.

[0068] Reference Figure 6The second example of the determination process of the determination unit 33 will be explained. First, the determination unit 33 obtains the number Np of the repaired workpieces W (S11). Next, it determines whether the obtained number Np of workpieces W has reached the number N (set number N) corresponding to the predetermined repair period (S12). If it has not reached the set number N (S12: No), it returns to S11.

[0069] On the other hand, when the set quantity N is reached (S12: Yes), the grinding stone condition level L(N) of the Nth workpiece W after finishing is obtained (S13). Here, in this example, after grinding the Nth workpiece W, the finishing of the grinding stone 16 is performed. Therefore, the grinding stone condition level L(N) of the Nth workpiece W becomes the grinding stone condition level before the finishing is performed.

[0070] Next, the obtained grinding stone condition level L(N) is determined to fall within the grinding stone condition level range of Lev1, Lev2, Lev3, and Lev4 (S14). Then, the adjustment conditions corresponding to the relevant grinding stone condition level range are determined (S15). For example, if the initial setting of the adjustment conditions is Lev1, then in the case of Lev2, Lev3, or Lev4, the adjustment conditions are determined to be changed. In this example, the radial cutting amount of the grinding stone 16 is changed as the adjustment condition.

[0071] Then, the decision to perform the repair is made based on the modified repair conditions (S16). Here, if the determination unit 33 decides to perform the repair, the execution unit 34 performs the repair of the grinding stone 16. That is, the execution unit 34 performs the repair of the grinding stone 16 with conditions corresponding to the grinding stone state level L(N) before the repair is to be performed. As a result, the repair interval for the number of workpieces W until the next repair can be set to the desired number.

[0072] (4-3. The Third Case)

[0073] Reference Figure 7 as well as Figure 8 The decision unit 33 and the execution unit 34 in the third example will be explained. Figure 7 In this system, the maximum value for the grinding stone condition level is Lmax, and the grinding stone condition level L must not exceed this maximum value Lmax. Furthermore, under normal conditions of grinding, the grinding stone condition level immediately after grinding is below the minimum threshold Lmin.

[0074] In this example, a predetermined period for repair is set. For instance, the predetermined period for repair is set as the number N of workpieces W counted from the last repair. That is, when the number of workpieces W counted from the last repair reaches N, it is determined that the predetermined period for repair has been reached.

[0075] If the number of repaired workpieces W reaches N, the determination unit 33 decides to perform the repair on the grinding stone 16. Furthermore, just now... Figure 7 The grinding stone condition level L2(1) after T1 was adjusted was not less than the minimum threshold Lmin. That is, it means that the adjustment was not performed properly.

[0076] Therefore, the grinding stone state level L2(1) after the T1 adjustment is not less than the minimum threshold Lmin, so a further adjustment is performed. Figure 7 (T2). Thus, the grinding stone condition level L3(1) after the re-trimming becomes insufficient to meet the minimum threshold Lmin. Furthermore, if the number of trimmed workpieces W reaches N, then trimming is performed ( Figure 7 The grinding stone condition level L4(1) after the trimming is less than the minimum threshold Lmin, so no further trimming is performed.

[0077] Reference Figure 8 The third example of the determination process of the determination unit 33 will be explained. First, the determination unit 33 obtains the number Np of the repaired workpieces W (S21). Next, it determines whether the obtained number Np of workpieces W has reached the number N (set number N) corresponding to the predetermined repair period (S22). If it has not reached the set number N (S22: No), it returns to S21.

[0078] On the other hand, when the set quantity N is reached (S22: Yes), the determination unit 33 decides to perform the trimming (S23). In this way, the execution unit 34 performs the trimming of the grinding stone 16.

[0079] Next, the determination unit 33 obtains the grinding stone condition level L(1) after grinding (S24). That is, after grinding the workpiece W, the grinding stone condition level L(1) related to the workpiece W after grinding is obtained. Then, it is determined whether the obtained grinding stone condition level L(1) is less than the minimum threshold Lmin (S25). That is, the determination unit 33 determines whether further grinding can be performed. If it is less than the minimum threshold Lmin (S25: Yes), the determination process of the determination unit 33 ends.

[0080] On the other hand, if the minimum threshold Lmin is not exceeded (S25: No), the determination unit 33 decides to perform re-adjustment (S26). In this case, the execution unit 34 performs re-adjustment.

[0081] Here, the conditions for re-dressing can be set to be different from the conditions for normal dressing. For example, the radial cutting amount used as a condition for re-dressing can be set to be less than the radial cutting amount used for normal dressing. Alternatively, the conditions for re-dressing can be determined in relation to the grinding stone condition level L(1) after grinding. For example, the conditions for re-dressing can be determined in relation to the difference between the grinding stone condition level L(1) after grinding and the minimum threshold Lmin.

[0082] After further trimming, return to S24 for further processing. Therefore, if the grinding stone condition level L(1) after grinding is less than the minimum threshold Lmin again due to improper trimming, the trimming process is repeated.

[0083] (4-4. Others)

[0084] The determination unit 33 can also perform processing that combines the first determination process with the third determination process. Furthermore, the determination unit 33 can also perform processing that combines the second determination process with the third determination process. That is, it can determine the timing of the adjustment in the first or second determination process, and determine whether to perform further adjustments immediately following the initial adjustment in the third determination process.

[0085] (5. Evaluation value)

[0086] Next, the evaluation values ​​detected by detector 31 will be explained. As mentioned above, the evaluation values ​​are at least one of the surface property evaluation value and the outer diameter evaluation value.

[0087] (5-1. Evaluation value of the first surface property)

[0088] The first surface condition evaluation value is a value that evaluates the surface condition of workpiece W caused by chatter. Specifically, the first surface condition evaluation value is a value obtained using circumferential chatter, which represents the chatter state in the circumferential direction. More specifically, the first surface condition evaluation value uses multiple chatter amounts obtained from circumferential chatter at multiple axial positions. The calculation method of the first surface condition evaluation value is explained below.

[0089] Acceleration or displacement data detected by detector 31 is acquired in a time series manner. For example, when the contact position of the detection measuring contact 17b of the dimensional determination device 17 with the grinding surface of the workpiece W is moved in a spiral manner, time series data related to the spiral position of the rotating workpiece W at predetermined angles are acquired. That is, multiple time series data are acquired.

[0090] That is, while the workpiece W is rotating during grinding, the detection and measuring contact 17b of the dimension determining device 17 moves along the Z-axis direction, which is the axial direction of the workpiece W, via the feed mechanism 17a. In this case, the detection and measuring contact 17b of the dimension determining device 17 contacts the grinding surface of the workpiece W, and therefore the contact position between the center of the detection and measuring contact 17b and the workpiece W moves along a spiral trajectory on the grinding surface of the workpiece W. Therefore, the multiple acceleration data obtained are acceleration data detected while the detection and measuring contact 17b moves relative to the workpiece W in a spiral pattern on the grinding surface, and are data that are distinguished at predetermined angles in a spiral pattern.

[0091] For example, in Figure 9 The workpiece W shown illustrates the case of acquiring acceleration data for one full rotation of workpiece W. In this case, the data acquisition position moves spirally from circumferential position Pa, through circumferential position Pb, and back to circumferential position Pa. Multiple acceleration data points are generated by separating the acceleration data for one full rotation of workpiece W into multiple data points at predetermined angular intervals. It should be noted that by moving in a spiral manner, time-series data at different axial positions can be acquired within a short time.

[0092] Next, an FFT (High-Speed ​​Fourier Transform) is performed on multiple acceleration data obtained from detector 31 (accelerometer) in a time series to extract data related to accelerations having a rotational frequency component (specific frequency component) corresponding to the number of revolutions of grinding stone 16. Then, an inverse FFT is performed on the data related to accelerations having the extracted specific frequency component. This is converted into displacement values ​​of the detection measuring contact 17b of the size determination device 17 having specific frequency components, that is, displacement data (circumferential vibration data) related to the unevenness (surface roughness) of the grinding surface of workpiece W. It should be noted that the specific frequency component is the number of revolutions of grinding stone 16 and frequency components that are integer multiples of the number of revolutions.

[0093] This generates multiple data points on circumferential vibrations originating from the grinding stone. For example... Figure 10 As shown, multiple circumferential vibration data caused by the grinding stone are, for example, A1-A6. The obtained acceleration data are data from a spiral trajectory, therefore, as... Figure 10 As shown, the circumferential positions of the various circumferential jitter data A1-A6 are different.

[0094] Here, the workpiece W is ground while the grinding stone 16 is rotated. Therefore, the surface shape of the grinding stone 16 is transferred onto the grinding surface of the workpiece W every few rotations of the grinding stone 16. Specifically, when there are large protruding abrasive grains on the surface of the grinding stone 16, recesses are formed on the grinding surface of the workpiece W by significantly removing the portion that contacts the abrasive grains. In this case, the recesses formed on the workpiece W are formed at equal intervals in the rotational direction, and the interval between the circumferential recesses of the workpiece W coincides with the rotational period (every few rotations) of the grinding stone 16. Therefore, by extracting data related to acceleration with specific frequency components, the unevenness caused by the grinding stone on the grinding surface of the workpiece W can be extracted.

[0095] Next, using the circumferential vibration data (displacement data) on the grinding surface of workpiece W, a series of surface roughness data is generated. As described above, the generated multiple circumferential vibration data are generated at angles that are different from each other relative to the rotation axis of workpiece W. Therefore, as Figure 10 As shown, the circumferential vibration data at adjacent axial positions become the data of the positions that are offset from each other in the circumferential direction of the workpiece W.

[0096] As described above, the circumferential unevenness (surface roughness) on the grinding surface of workpiece W recurs on the grinding surface of workpiece W every rotation cycle of the grinding stone 16. Therefore, the circumferential vibration data at different angles are displayed in the circumferential direction (…). Figure 11 Move in the direction of the arrow shown. Therefore, as... Figure 11 As shown, the circumferential vibration data at different angles are formed to the same angle as the workpiece W, and a series of surface roughness data are generated in parallel along the axial direction.

[0097] Here, when segmenting circumferential vibration data (displacement data) obtained from acceleration data acquired in a spiral pattern, there is sometimes a deviation in the convexity / concaveness represented by the segmented roughness data. Therefore, when generating surface roughness data, the relative positions of each circumferential vibration data point are corrected so that the convexity / concaveness at the endpoints of each data point is continuous along the workpiece W axis (Z-axis direction). In this case, the surface roughness data, as state data, is generated by arranging the corrected circumferential vibration data points along the axial direction.

[0098] Next, as Figure 12 As shown, the generated surface roughness data is used to calculate the chatter at multiple axial locations. Here, chatter refers to the difference between the maximum and minimum values ​​of the chatter data in each circumferential direction. For example, calculating... Figure 11The data shows the circumferential vibration data A1-A6, each representing a specific vibration amount. In reality, the circumferential vibration data is divided into segments at minute angles along the circumference of the workpiece W, thus requiring the calculation of vibration amounts at more axial positions than is shown in the diagram.

[0099] Furthermore, the first surface characteristic evaluation value can be formed as at least one of the following: the average value of the vibration amount at multiple axial positions, the degree of difference of the vibration amount (variance, mean deviation, etc.), and the difference between the maximum and minimum values ​​of the vibration amount. It should be noted that the first surface characteristic evaluation value can also be any one of the average value, degree of difference, or difference of the vibration amount, or it can be a composite value obtained by combining them. It should be noted that in the above description, multiple circumferential vibration data are used to generate surface roughness data for the purpose of relating to the following content, but it is not necessary to generate surface roughness data.

[0100] (5-2. Outer Diameter Evaluation Value)

[0101] The outer diameter evaluation value is a value used to evaluate the change in the outer diameter of a workpiece (W) at an axial position. The calculation method for the outer diameter evaluation value is explained below.

[0102] Based on the signal from the dimension determining device 17, the outer diameter data of the workpiece W is obtained. First, based on the signal from the dimension determining device 17, time series data of displacement with the longitudinal axis as the outer diameter, i.e., the outer diameter data, is obtained.

[0103] Next, an FFT is performed on the obtained outer diameter data to extract specific frequency components. Specifically, components corresponding to the rotational frequency of workpiece W, i.e., 1 Hz / cycle components, are removed. Strong 1 Hz / cycle components are detected when the rotational axis of workpiece W deviates. As the outer diameter data, obtaining the axial outer diameter change of workpiece W is sufficient, therefore the 1 Hz / cycle components are removed here.

[0104] Furthermore, vibrations caused by circumferential chatter of the workpiece W were detected on the high-frequency side of the acquired outer diameter data. Circumferential chatter refers to the information contained in the circumferential chatter data in the calculation of the first surface property evaluation value. The range of the low-frequency components extracted here can be appropriately determined based on the grinding stone 16 and the rotational speed of the workpiece W, but for example, it can be set to below 50 Hz. In this way, by extracting low-frequency components other than the 1 Hz / circle component as components in a specific frequency region, the axial outer diameter variation of the workpiece W is extracted.

[0105] Next, an inverse FFT is performed on the outer diameter data containing the extracted specific frequency components. This converts the data into time-series data related to the displacement of the outer diameter with specific frequency components. For example, the generated outer diameter data is as follows: Figure 13 As shown.

[0106] Furthermore, the outer diameter evaluation value can be formed as at least one of the following: the average deviation of the outer diameter at multiple axial positions, the degree of difference in the outer diameter, or the difference between the maximum and minimum values ​​of the outer diameter. It should be noted that the outer diameter evaluation value can also be any one of the average deviation, degree of difference, or difference in the outer diameter, or it can be a composite value obtained by combining them.

[0107] (5-3. Evaluation value of second surface properties)

[0108] The second surface property evaluation value is a value used to evaluate the surface condition of workpiece W by representing the surface property of workpiece W as a planar surface property. Specifically, the second surface property evaluation value is obtained by using the planar surface property to obtain linear surface properties that represent the relationship between each circumferential position, axial position and surface property, and using representative values ​​from each linear surface property.

[0109] More specifically, modified surface roughness data, which serves as the surface surface property, is generated using the surface roughness data generated during the calculation of the first surface property evaluation value and the outer diameter data generated during the calculation of the outer diameter evaluation value. Furthermore, the modified surface roughness data is used for the second surface property evaluation value.

[0110] First, obtain the surface roughness data generated during the calculation of the first surface property evaluation value. Figure 11 As shown). Furthermore, the outer diameter data generated during the calculation of the outer diameter evaluation value is obtained (as shown). Figure 13 (As shown). Then, by synthesizing the surface roughness data and outer diameter data, a model is generated. Figure 14 The modified surface roughness data is shown below. The modified surface roughness data corresponds to the surface properties used in the second surface property evaluation value.

[0111] Next, as Figure 14 As shown, in the corrected surface roughness data, for each circumferential position θa, θb, the representation is obtained. Figure 15 The linear surface features represent the relationship between axial position and surface characteristics, as shown. Multiple linear surface features are generated for each circumferential position. Then, representative values ​​for each linear surface feature are obtained. Representative values ​​can be obtained using arithmetic mean roughness Ra, maximum height roughness Rz, ten-point average roughness, etc.

[0112] Furthermore, the second surface trait evaluation value can be formed as at least one of the average of multiple representative values, the degree of difference among multiple representative values, or the difference between the maximum and minimum values ​​among multiple representative values. It should be noted that the second surface trait evaluation value can also be any one of the average of multiple representative values, the degree of difference, or the difference, or it can be a composite value obtained by combining them.

[0113] (5-4. Evaluation value of third surface characteristics)

[0114] The third surface characteristic evaluation value is a value used to evaluate the surface condition of workpiece W by representing its surface characteristics as a planar surface. Specifically, the third surface characteristic evaluation value is a representative value of the planar surface characteristics as a whole. Representative values ​​include the arithmetic mean roughness Sa, the maximum height Sz, and the root mean square root height Sq on the surface.

[0115] If the planar surface characteristics used in the third surface characteristic evaluation value can be directly detected by detector 31, then the planar surface characteristics used in the third surface characteristic evaluation value can be formed as the detection data. Alternatively, the planar surface characteristics can also be formed as planar roughness data generated during the calculation of the first surface characteristic evaluation value, or as corrected planar roughness data generated during the calculation of the second surface characteristic evaluation value.

[0116] (6. Summary)

[0117] As described above, the dressing device 30 uses at least one evaluation value, including a surface texture evaluation value and an outer diameter evaluation value, to represent the surface condition of the workpiece W. This evaluation value represents the surface condition of the workpiece W itself. Furthermore, since the surface condition of the grinding stone 16 is transferred onto the surface of the workpiece W, this evaluation value also represents the surface condition of the grinding stone 16.

[0118] Therefore, the calculation unit 32 uses this evaluation value, which indirectly represents the surface condition of the grinding stone 16, to calculate the degree of shape damage (grind stone condition level) of the grinding stone 16. Then, based on the calculated degree of shape damage (grind stone condition level), the determination unit 33 determines at least one of whether repair can be performed or whether the conditions for repair can be changed. Therefore, by performing repair based on the degree of shape damage (grind stone condition level) of the grinding stone 16, which is indirectly evaluated using the surface condition of the workpiece W, it is possible to stabilize the quality of the workpiece W and extend the lifespan of the grinding stone 16.

Claims

1. A trimming device, wherein, have: The detector, which serves as an evaluation value representing the surface condition of a workpiece having a central axis, detects at least one of a surface characteristic evaluation value representing the surface characteristics of the workpiece in the axial direction and an outer diameter evaluation value related to the outer diameter at multiple axial positions. The calculation unit calculates the degree of shape damage on the grinding stone configured to grind the workpiece, starting from a reference surface state, based on at least one evaluation value corresponding to the surface state of the workpiece detected by the detector. The determination unit, based on the degree of shape damage, determines at least one of whether the grinding stone can be used for repair and whether the conditions for the repair can be changed. as well as The execution unit, based on the determination result of the determination unit, performs the dressing of the grinding stone. The detector includes an acceleration sensor or displacement sensor that detects the acceleration or displacement of the arm of the detection measuring contact of the detection support dimension determination device, and detects time-series data of the acceleration or displacement of the arm as the contact position of the detection measuring contact with the grinding surface of the workpiece is moved spirally, and uses the time-series data to detect the evaluation value. The reference surface condition on the grinding stone is a straight line parallel to the central axis of the grinding stone. The degree of shape damage on the grinding stone is the radial deviation from a straight line parallel to the central axis of the grinding stone.

2. The trimming device according to claim 1, wherein, The predetermined period for the repair is set when the number of times the workpiece has been ground since the last repair is performed reaches a predetermined number of times the workpiece has been ground. When the predetermined repair period is reached, the determination unit determines, based on the degree of shape damage, whether the repair period can be extended from the preset period. If the determination is to extend the repair period, it decides on the extended repair period. The actuator performs the grinding of the grinding stone when the time for the adjustment, which has been delayed from a predetermined period, has arrived.

3. The trimming device according to claim 1, wherein, The determination unit determines to change the conditions of the finishing process in accordance with the degree of shape damage before the finishing process of the grinding stone is to be performed. The execution unit performs the modification based on the modified modification conditions.

4. The trimming device according to claim 3, wherein, The actuator changes the radial cutting amount of the grinding stone as a condition for the dressing and performs the dressing.

5. The trimming device according to claim 1, wherein, The determination unit determines whether the grinding stone can be re-trimmed based on the degree of shape damage after the grinding stone has just been trimmed. The execution unit performs the re-adjustment if it determines that the determination unit will perform the re-adjustment.

6. The trimming device according to claim 2, wherein, The determination unit determines whether the grinding stone can be re-trimmed based on the degree of shape damage after the grinding stone has just been trimmed. The execution unit performs the re-adjustment if it determines that the determination unit will perform the re-adjustment.

7. The trimming device according to claim 3, wherein, The determination unit determines whether the grinding stone can be re-trimmed based on the degree of shape damage after the grinding stone has just been trimmed. The execution unit performs the re-adjustment if it determines that the determination unit will perform the re-adjustment.

8. The trimming device according to claim 4, wherein, The determination unit determines whether the grinding stone can be re-trimmed based on the degree of shape damage after the grinding stone has just been trimmed. The execution unit performs the re-adjustment if it determines that the determination unit will perform the re-adjustment.

9. The trimming device according to any one of claims 1 to 8, wherein, The detector, as a surface property evaluation value representing the surface state of the workpiece, uses multiple vibration quantities obtained from circumferential vibrations at the multiple axial positions to detect at least one of the following: the average value of the multiple vibration quantities, the degree of difference between the multiple vibration quantities, and the difference between the maximum and minimum values ​​of the multiple vibration quantities.

10. The trimming device according to any one of claims 1 to 8, wherein, The detector, as an outer diameter evaluation value representing the surface state, detects at least one of the following: the average deviation of the outer diameter at multiple axial positions, the degree of difference in the outer diameter, and the difference between the maximum and minimum values ​​of the outer diameter.

11. The trimming device according to any one of claims 1 to 8, wherein, The detector performs the following processing: Using a planar surface feature that represents the surface characteristics of the workpiece as a planar surface feature, a linear surface feature representing the relationship between the axial position and the surface characteristics is obtained for each circumferential position of the workpiece. Obtain multiple representative values ​​from each of the aforementioned linear surface properties. As a surface property evaluation value representing the surface state of the workpiece, at least one of the following is detected: the average value of the representative values, the degree of difference of the representative values, and the difference between the maximum and minimum values ​​among the representative values.

12. The trimming device according to any one of claims 1 to 8, wherein, The detector, as a surface property evaluation value representing the surface state of the workpiece, uses a planar surface property that represents the surface property as a whole to detect a representative value of the planar surface property.

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