JPS6377637A - Numerically controlled machine tool - Google Patents

Abstract

PURPOSE:To improve machining accuracy by constituting a speed control means which compares measured profile data with ideal profile data to calculate the error and corrects the ideal profile data by the error to obtain implementation data. CONSTITUTION:A speed control means adds the speed control signal in response to the command speed of a control shaft to the speed control signal in response to the follow-up error between a main spindle and the control shaft of a tool feed shaft, thus the follow-up performance to the speed component of profile data is improved. However, the profile data have the secondary or higher differential components, the follow-up performance to these components is not improved, thus the profile of a work actually machined with ideal profile data is measured, ideal profile data corrected by the deviation with the ideal profile data are used as implementation profile data, and the actual machining is performed with these data. Accordingly, correction of the profile data is automatically performed by a numerically controlled device 30, thus high-accuracy machining is performed efficiently.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a numerically controlled machine tool for machining non-perfect circular workpieces (hereinafter also simply referred to as "workpieces") such as cams.

[Prior art]

Conventionally, a method is known in which a numerical control device controls the feed of a grinding wheel in a direction perpendicular to the spindle axis in synchronization with the rotation of the spindle to grind a workpiece such as a cam. In order to synchronously control the feed of the grinding wheel, it is necessary to provide profile data to the numerical control device. This profile data gives the amount of movement of the grinding wheel for each unit rotation angle of the main shaft so that the grinding wheel is reciprocated along the finished shape of the workpiece, that is, it is moved to create a profile. On the other hand, in order to grind a workpiece, in addition to the profile data, machining cycle data for controlling machining cycles such as feed, cutting, and retraction of the grinding wheel is required. The workpiece is machined by numerically controlling the rotation of the spindle and the feed of the grinding wheel based on this machining cycle data and profile data.In particular, the ability to follow the command values of the spindle and tool feed axis during profile creation movement is particularly important. The quality of the process is an important issue in terms of processing accuracy.

[Problems to be solved by the invention]

By the way, increasing the gain of the servo system may be considered to reduce the tracking delay error, but this method has the disadvantage that control becomes unstable. In addition, the workpiece is once machined using ideal profile data determined from the finished shape of the workpiece, and the profile of the workpiece is manually measured by the worker using a cam measuring device, etc., and the ideal profile V1 fill data is obtained. The current work is to find the deviation of the ideal profile data, correct it to the ideal profile data, and find the actual profile data. However, the follow-up delay varies depending on the profile of the workpiece and the temperature condition of the servo system and changes over time. Therefore, in order to improve machining accuracy,
Although it is necessary to frequently correct the profile data, there is a problem in that the work efficiency is extremely low because the correction is done manually by the operator. The present invention has been developed to solve the above-mentioned problems, and its purpose is to efficiently correct profile data and improve processing accuracy.

[Means for resolving the point of view]

The structure of the invention for solving the above problems is that the spindle and the tool feed axis are used as control axes, and the tool is moved to create a profile along the finished shape of the non-perfect circular workpiece based on profile data. Numerical value i1 for machining the workpiece
In the i-controlled machine tool, a speed control means adds a second speed control signal corresponding to a command speed of the control axis to a first speed control signal corresponding to a tracking error of the control axis, and the non-perfect circular workpiece. an ideal profile data storage means for storing ideal profile data determined from the finished shape of the main shaft; and detecting the current value of the spindle and the current value of the tool feed axis;
a profile measuring means for obtaining measurement profile data indicating the relationship between the position of the tool feed axis with respect to the position of the main shaft of the mantle; a measurement command means for instructing when to start driving the profile measuring means; error calculating means for calculating an error by comparing the measured profile data and the ideal profile data;
and data correction means for correcting the ideal profile data by the error calculated by the error calculation means to obtain execution profile data.

[Effect]

The speed control means improves the ability to follow the speed component of the profile data. However, since the profile data has differential components of second or higher order, the followability to these components is not improved. Therefore, the profile of the workpiece actually machined using the ideal profile data is measured and compared with the ideal profile data. The data obtained by correcting the ideal profile data by the deviation is used as the execution profile data, and the actual machining is performed using this data. For example, when measurement is commanded by the measurement command means during idle operation based on ideal profile data or when spark-out machining is actually being performed on a workpiece, the profile measurement means uses the current value of the spindle. Detects the current value of the tool feed axis and obtains measurement profile data. This measurement profile data indicates the actual machined shape when the workpiece is machined. The measured profile data is compared with ideal profile data determined from the finished shape of the workpiece by the error calculation means, and the error is calculated. Next, the ideal data is corrected by the error by the data correction means, and execution profile data to be used in actual processing is obtained.

【Example】

The present invention will be described below based on specific examples. FIG. 1 is a configuration diagram showing a numerically controlled grinding machine. Reference numeral 10 denotes a bed of a numerically controlled grinding machine, and a table 11 is disposed on the bed 10 so as to be slidable in the Z-axis direction parallel to the spindle axis. A headstock 12 having a main spindle 13 mounted thereon is disposed on the table 11, and the main spindle 13 is rotated by a servo motor 14. Further, a tailstock 5 is placed on the right end of the table 11, and the center 16 of the tailstock 15 and the main shaft 13 are
A workpiece W consisting of a cam is held between the center 17 and the center 17 of the cam. The workpiece W fits into a positioning pin 18 protruding from the spindle 3, and the rotational phase of the workpiece W matches the rotational phase of the spindle 130. A tool stand 20 that can move forward and backward along a tool feed axis (X M ) is guided behind the bed 10, and a grinding wheel G that is rotationally driven by a motor 21 is supported on the tool stand 20. This tool stand 20 is connected to a servo motor 23 via a feed screw of a circuit, and is moved forward and backward by forward and reverse rotation of the servo motor 23. As shown in FIG. 13, the drive units 40 and 41 are circuits that input command pulses from the numerical control device 30 to drive the servo motors 23 and 14, respectively. As shown in FIG. 13, the drive unit 40 includes a deviation counter 401 that inputs the fj7 order pulse from the numerical control device 30 and a feedback pulse from the pulse generator 52, a DA converter 402 that converts the output from D to A, and a DA converter 402 that converts the output to speed. In addition to a normal servo system consisting of an amplifier 403 that calculates and amplifies the output of the generator 53 and applies a driving voltage to the servo motor, the amplifier 403 converts the output into a voltage according to the frequency of the command pulse and sends the voltage signal to the amplifier 403. An FV converter 404 is provided which adds to the input. This FV converter 404 adds a velocity number 43 proportional to the velocity component of the profile data, and there is a tracking delay related to the velocity component. ill+ to be hazy. Drive unit 4
The same applies to 1. The numerical control device 30 is a device that mainly numerically controls the rotation of the servo motors 23 and 14 to control the grinding process of the workpiece W. The numerical control device 30 includes a tape reader 42 for inputting ideal profile data, machining cycle data, etc., a keyboard 43 for inputting control data, etc., a CR7 display device 44 for displaying various information, and various controls 48.
A control panel 45 that outputs signals is connected. As shown in FIG. 2, the numerical control device 30 mainly includes a main CPU 31 for controlling the grinding machine, a ROM 33 that stores a control program, a RAM 32 that stores input data, and an input/output interface 34. The RAM 32 has an NC data area 321 for storing NC data and an ideal profile data area 32 for storing ideal profile data determined from the finished shape of the workpiece W.
2 and an execution profile data area 323 for storing corrected execution profile data, and a phase error distribution tα area 328 for storing phase errors according to the rotational speed of the spindle and the ideal profile data number. In addition, a feed mode setting area 324 for setting various modes, a workpiece mode setting area 325, and a spark-out mode setting area Ffc
32B, phase 84 difference 1m ('fj mode setting area 32
7 is provided. Number i; lI please! A device 3 is the other servo motor 23.
14 drive system, drive CPU 36 and RAM 35
and a pulse distribution circuit 37 are provided. The RAM 35 is a device that inputs positioning data for the grinding wheel G from the main CPU 31. DriveCPtJ
36 is a device that numerically controls the main spindle 13 and the tool feed axis, performs calculations such as slow-up, slow-down, and interpolation I11 of the target point, and outputs positioning data of the interpolation point at regular intervals.The pulse distribution circuit 37 This circuit outputs a movement command pulse to each drive unit 40, 41 after pulse distribution. Further, as one element of the profile measuring means, a sampling device 38 and a RAM for storing sampling data are provided.
39 are provided. The sampling device [38 has counters 381, 382 for counting the feedback pulses output from the pulse generators 52 and 50. These counters 381 and 382 are reset by inputting a reset signal from the main CPU 31, and by inputting measurement start No. 11 from the main CPU 31, the tool feed axis (X axis) and the main axis (
Start counting the feedback pulses on the C-axis). In addition, the sampling device ff138 has an address counter 383 that is reset by a reset signal from the main CPU 31 and updated every sampling, and when a measurement start signal is input, the values of the counters 381 and 382 are updated at regular intervals. It is output to the address of the RAM 39 indicated by the counter 383. Next, the effect will be explained. NC data including phase error measurement cycle data and machining cycle data is stored in the RAM 32, and the data structure is shown in FIG. 8 for the phase error measurement cycle data and FIG. 9 for the machining cycle data. Control panel 45
When the button 451 is pressed, the flag in the phase error correction ff mode setting area 327 is reset, and phase error measurement cycle data based on ideal profile data is activated. Furthermore, when the button 452 on the control panel 45 is pressed, the machining cycle data is activated. These NC data are CP
It is decoded by U31 according to the procedure shown in the flowchart of FIG. In step 100, one block of NC data is read out, and in the next step 102, it is determined whether or not the data has ended. In the case of data end, this program is terminated. If it is not the data end, the process moves to step 104 and subsequent steps, and the code of the instruction word is determined. Step 104
If it is determined that the instruction word is a G code, the CPU processing moves to step 106 to determine a more detailed instruction code. In steps 106-120,
Mode setting is performed according to the instruction code. Step 1
If it is determined to be a GOI code in step 06, proceed to step 10.
At step 8, a flag is set in the feed mode setting area 324, and the feed mode is set to the grinding feed mode. Similarly, when the GO4 code is determined in step 110, a flag is set in the spark-out mode setting area 326 in step 112, and the feed mode is set to spark-out mode. Further, when it is determined in step 114 that the code is a G50 code, a flag is set in the phase error compensation mode setting area 327, and the control mode is set to a phase error compensation mode in which offset is performed by the phase error. Further, when it is determined in step 120 that the code is G51, the flag in the workpiece mode setting area 325 is reset in step 121, and the workpiece mode is set to the normal mode. When the above mode setting is completed, the processing of the CPU moves to step 122, and processing according to the NC data and the set mode is performed. If it is determined in step 122 that the code is 652, a reset signal is output to the sampling device 38 in step 123, and sampling conditions and the like are set. If it is determined in step 124 that the code is 053, a measurement start signal is output to the sampling device 38 in step 126. Further, when it is determined that the code is 655 in step 128, sampling data is read from the RAM 39 in step 130, measurement profile data is calculated from the data, error calculation is performed by comparison with ideal profile data, and correction calculation is performed. Execution profile data is then created. Next, if it is determined in step 132 that the readout block has an X code, the process proceeds to step 134, where it is determined whether the mode setting is cam mode and grinding feed mode (hereinafter referred to as "cam/grinding mode"). When in the cam/grind mode, pulse distribution for cam generation is performed in step 140. On the other hand, when not in the cam/grinding mode, pulse distribution is performed in step 136 which is not synchronized with the normal rotation of the main shaft. (a) Phase error measurement process When the button 451 on the control panel 45 is pressed, the phase error measurement cycle data shown in FIG. 8 is decoded block by block according to the flowchart in FIG. First, the G51 code of block Nll0 sets the workpiece mode to cam mode, and the ideal profile data to be used is designated by number P1234. The 81200G52 code of the next block performs initial settings for sampling, and the G53 code of the next block N130 outputs a measurement start signal to the sampling device 38. In addition, the depth of cut is zero due to the dwell code of the GO4 code, and the rotation speed of the spindle is 1 Orpm (SIO code).
Only the profile creation movement of is processed by the procedure illustrated in FIG. The ideal profile data is the unit rotation angle of the main axis is 0.
．． The movement of the tool feed axis every 5 degrees is expressed in the number of pulses and is made into a table, which is referenced as D(+) by the read address I of the ideal profile data. First, step 3
00, the state of the phase error compensation mode setting area 327 is checked, but at the time of phase error measurement processing, the flag is reset and it is not the phase error compensation mode, so the process moves to step 302 and the read address I and offset address are Both IOs are initialized to 1. The offset address 10 is used to compensate for phase errors and corresponds to the control start address for one cycle. Next, in step 304, a pulse distribution completion signal is input from the drive CPL 136, and it is determined whether the pulse distribution in the previous cycle has been completed.If it is determined that the pulse distribution has been completed, the process moves to step 306, and the ideal profile data D(+ ) is read out, and in step 308, the positioning data (travel height and speed) of the grinding wheel G for each unit rotation angle of the spindle is determined by the drive C.
It is output to the RAM 35 for passing to the PU 36. Next, in step 310, it is determined whether the read address I is equal to or greater than the end address I)4AX of the ideal profile data. I≧l) When IAX, the read address I is set to the initial value 1 in step 312 to return to the top of the table; otherwise, the read address I is updated by 1 in step 314. Next, in step 316, it is determined whether the read address I is equal to the offset address IO, and if they are equal, it means that the control of one rotation of the spindle has been completed, and the process moves to step 318, where the number of revolutions of the spindle is If it is determined that the rotation has been completed the specified number of times (two times in the NC data of FIG. 8), this program is terminated, and if it is determined that the specified number of rotations have not been completed, the program proceeds to step 304. The next rotation cycle is then controlled. In this way, the grinding wheel G performs dry grinding or spark-out machining using only the profile generating motion, but during this process, the sampling device 38 records the current value of the main axis and the current value of the tool feed axis at fixed time intervals. The sampled data is stored in the RAM 39. That is, the sampling device 38 executes the process shown in FIG. 5 at the designated sampling period. The value of the counter 382 in step 400 and the value of the counter 381 in step 402 are shown in the RAM 3 by the value I of the address counter 383.
9 Noah)'Res MC(1>,!:MX(1)
l: Stored and stored in the address counter 38 in step 404.
30 value I is updated by 1. Such processing is repeated at the sampling period while the main shaft rotates once, and sampling data is obtained. Next, using the G55 code of block N140, error calculation is performed according to the flowchart of FIG. The sampling data obtained by the sampling device 38 are current values at regular time intervals on both the C-axis and the X-axis, as shown in FIG. In step 500, the C
The sampling data of the axis is captured and the corresponding time is calculated by γ for each unit rotation angle of the C axis, and the current value of X1lII for that time is obtained by interpolating the sampling data of the X axis. X corresponding to each unit rotation angle of
The current value of the axis is determined. That is, sampling data is converted to measurement profile data. Next, in step 502, as shown in FIG. 11, the C-axis value θI when the X-axis takes the maximum value is determined from the ideal profile data.
In step 504, the value θM of the C-axis when the X-axis takes the maximum value is determined from the measurement profile data. Next, in step 506, the phase error Δθ is calculated as θM−θI, and the phase error Δθ is stored in correspondence with the ideal profile data number and the rotational speed of the spindle. Further, in step 510, as shown in FIG. 14, the error of the measured profile data with respect to the ideal profile data is
As shown in the partial enlargement, the phase error Δθ and the position error ΔX are calculated separately. Then, in step 512, the position error ΔX(θ) at each phase is determined, and the corrected execution profile data is calculated by subtracting the error ΔX(θ) from the ideal profile data, and the data is stored in the execution profile data area 323. and is controlled according to this execution profile data during actual machining. In this way, the phase error corresponding to one ideal profile data and one spindle rotation speed is measured using the NC data of blocks N120 to N140, but similar measurements can be made by changing the spindle rotation speed and ideal profile data. By doing this, the phase error table shown in FIG. 10 is created in the phase error storage area 328. (b) Phase error and position error? When the +ti compensated button 452 of the machining control panel 45 is pressed, the machining cycle data shown in FIG. 9 is decoded block by block according to the flowchart of FIG. First, the 051 code of block N0IO sets the workpiece mode to cam mode and specifies the execution profile data to be used with number r'1234. 8020 of next block
050 code indicates phase error? A flag is set in the tn if mode setting area 327, and the control mode performs phase error compensation (fl) on the execution profile data to determine the machining side σ.
Phase error for B? rIif mode. The GOI code of the next block No. 30 sets the grinding feed mode, and the presence of the X code causes the cam grinding process to be performed by X-0,1. The F code represents the amount of grinding per rotation of the spindle, and the R code represents the grinding speed per rotation of the spindle. The S code represents the rotation speed of the spindle. In the NC data shown in FIG. 9, since the specified numerical values of the P code and the R code are equal, it is instructed to continuously cut at a constant speed with respect to the rotation of the main shaft. Phase error and position error? +n (rX cam creation is executed according to the flowchart in Fig. 7. First, in step 200, the cutting amount per unit rotation angle of 0.5° of the spindle is calculated as the number of pulses from the given F code. Then, in step 202, the phase error table shown in FIG. 10 is searched based on the execution profile data number and the rotational speed of the spindle, and the corresponding phase error is read out.Phase error Δθ
Since this is caused by a tracking delay of the main shaft, the phase error can be compensated for by sequentially outputting execution profile data that precedes the command angle of the main shaft by Δθ in the main shaft rotation angle. Therefore, an address where execution profile data is stored that precedes the origin of the command angle of the main axis by Δθ, that is, an offset address IO is calculated. Next, in step 204, the initial value of the read address ■ is set to the offset address IO. Next, in step 206, drive C
A pulse distribution completion signal is input from the PU 36, and it is determined whether the pulse distribution in the previous cycle has been completed. If it is determined that the pulse distribution has been completed, the process moves to step 20B, and the execution profile data row (1) is read out. At step 210, spindle 1
It is determined whether the cut per revolution is completed. This determination is made using numerical data specified by the F code. In this case, the determination is made based on whether or not a cut of 0.1 mm has been made. If the depth of cut per rotation of the spindle is not completed, in step 212, the depth of cut per unit angle is added to the execution profile data row (]) that has been read out, and i[t data is generated, and in step 214 Then, positioning data that is a combination of the movement amount data and speed data is output. Further, when the cutting per rotation of the spindle is completed, in step 213, the read execution profile data D(1) is directly used as the movement amount data. Next, in step 216, it is determined whether the read address I is greater than or equal to the end address 1□8 of the execution profile data. When ≧l+4All, the read address I is set to the initial value 1 in order to return to the top of the table in step 218, and when it is 1, the read address 1 is updated by 1 in step 220. Next, in step 222, it is determined whether the read address I is equal to the offset address IO, and if they are equal, it means that control of one rotation of the spindle has been completed, and the process moves to step 224, where the full depth of cut is completed. It is determined whether or not. This determination is made based on numerical data specified by the X code. If the full depth of cut has not been completed, the process moves to step 206 to proceed to the next control cycle. On the other hand, when the full depth of cut is completed, the cam grinding process instructed in block NO30 is completed. Next, spark-out processing is performed by the dwell code of the GO4 code of block N040 in the procedure shown in FIG. This flowchart is generally the same as the flowchart of FIG. 7, except that no cutting is performed and that the dwell process is stopped when the spindle has rotated a specified number of times. That is, step 3
00, the contents of the phase compensation mode setting area 327 are checked, but since the flag is set and the phase compensation mode is set, the initial stage for the phase error compensation processing in steps 322 and 324, which is similar to steps 202 and 204, is checked. After the settings are made, steps 304 and subsequent steps are executed. Further, this process differs only in the control during phase error measurement, the fact that the data used is execution profile data, and the initial settings of the read address I and offset address 0. That is, the corresponding phase error Δθ is searched from the phase error table according to the execution profile data and the rotational speed of the spindle, and the execution profile data that precedes the command angle of the spindle by the phase error Δθ is sequentially output for a predetermined cycle. As a result, spark-out machining with phase error compensation is performed for only a predetermined cycle. The above execution profile data has been corrected for the position error, and the phase error is compensated for by offsetting the read address during pulse distribution processing, so in the end, the total error is compensated for by both (H machining is executed In the above embodiment, the sampling device 38 samples the current values of the C-axis and the X-axis at regular intervals, but the counter 382 for measuring the current value of the C-axis is It is configured to output a timing signal every time it rotates by an angle, and this timing signal is used as a sampling signal to
The current values of the axes may also be sampled. In this case, for each unit rotation angle of the C-axis, the corresponding
Current values of the axes, ie measurement profile data, can be obtained immediately. Also, the phase error 〇 is determined by the phase difference of the maximum value of the X axis, but as shown in FIG. 11, the rotation angle θ1. Difference a between θ2 and rotation angle θ. , θ4 may be calculated using the average value. In addition, in error compensation, the error is decomposed into phase error and position error components, and error compensation is performed according to each component, but as shown in area B in Figure 14, only the position error of the same phase The ideal profile data may also be corrected. Alternatively, only the phase error may be compensated. FIG. 15 is a diagram showing the error when the speed control means is not provided, FIG. 16 is a diagram showing the error when the speed control means is provided, and FIG. 17 is a diagram showing the error when the speed control means is provided. FIG. 4 is a diagram showing errors when processing is performed using execution profile data that has been corrected. As is clear from this,
It can be seen that the errors are gradually improved. Effects of the Invention The present invention provides a speed control means that adds a second speed control signal corresponding to the commanded speed of the control axis to a speed control signal of ml corresponding to the tracking error of the control axis, and Detects the current value of the spindle and the current value of the tool feed axis, measures measured broil data that shows the relationship between the position of the tool feed axis with respect to the actual spindle position, and compares that data with the ideal profile data. In this system, the error is measured, and the ideal profile data is corrected according to the error, and control is performed using the execution profile data obtained. Therefore, the responsiveness to the speed component is improved by the speed control means, and error measurement and profile data correction are automatically performed by the numerical control device.
This has the effect of efficiently performing highly accurate machining.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a numerically controlled grinding machine according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of the numerical control device. FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are flowcharts each showing the processing procedure of the CPU. FIG. 8 is a configuration diagram of phase error measurement cycle data. FIG. 9 is a diagram showing the structure of the added bait/cycle data. FIG. 10 is a configuration diagram of a phase error table. FIG. 11 is an explanatory diagram showing a method of calculating a phase error. FIG. 12 is an explanatory diagram showing a method for obtaining measurement profile data from sampling data. 1st
Figure 3 is a block diagram showing the detailed configuration of the drive circuit. FIG. 14 is an explanatory diagram showing a method of calculating the error of measured profile data with respect to ideal profile data. FIG. 15, FIG. 16, and FIG. 17 are characteristic diagrams showing the measured errors, respectively. 10--Bed 11-Table 13--Main shaft 14.23-Servo motor 15-Tailstock 20゛-
Tool stand 30''...Numerical control device 50.52...
Pulse generator 51.53...Speed generator G''...-Grinding wheel W/Workpiece Patent applicant Toyoda Koki Co., Ltd. Representative Patent attorney Osamu Fujitani Figure 8 Figure 9 Figure 10 Figure 12 Figure C of Cq
Figure 14 Ward Ward

Claims (1)

[Claims] Numerical control for machining a non-circular workpiece based on profile data for making a profile-generating motion of the tool along the finished shape of the non-circular workpiece, using the spindle and the tool feed axis as control axes. In a machine tool, a speed control means for adding a second speed control signal corresponding to a command speed of the control axis to a first speed control signal corresponding to a tracking error of the control axis; and finishing of the non-perfect circular workpiece. ideal profile data storage means for storing ideal profile data determined from a shape; and detecting the current value of the spindle and the current value of the tool feed axis to determine the position of the tool feed axis relative to the actual position of the spindle. A profile measurement means for obtaining measurement profile data showing a relationship; a measurement command means for instructing when to start driving the profile measurement means; and a comparison between the measurement profile data measured by the profile measurement means and the ideal profile data. A numerically controlled machine tool comprising: an error calculation means for calculating an error; and a data correction means for correcting the ideal profile data by the error calculated by the error calculation means to obtain execution profile data.