JPS6377638A - Numerically controlled machine tool - Google Patents

Abstract

PURPOSE:To facilitate compensation of phase error and improve workability by comparing measured profile data with ideal profile data to calculate the phase error and offsetting the shaft control by the calculated phase error. CONSTITUTION:If measurement is commanded when an idle operation is being performed based on ideal profile data, for example, a profile measuring means detects the current value of a main spindle 13 and the current value of a tool feed shaft to obtain measured profile data. This indicates the actual machining shape when a work has been machined. These measured profile data are compared with the ideal profile data determined by a phase error calculating means based on the finished shape of the work to calculate the phase error. Next, shaft control is offset by an offsetting means by the phase error. Accordingly, the rotating speed of the main spindle is changed to perform an idle operation, the phase error due to the follow-up delay of the main spindle servo system can be automatically measured for each rotating speed of the main spindle, and compensation of the phase error is made easily.

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 side 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 equipment. 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]

Incidentally, there are two types of tracking delay errors: one due to the tool feed axis and the other due to the main axis. Among these, the one due to the tracking delay of the main axis appears as a phase error with respect to the profile data. In order to correct this phase error, a non-perfect circular workpiece is actually machined based on the profile data, and the phase error of the machined workpiece is measured using a cam measuring device.
The initial position of the spindle is offset by this phase error when starting the next machining. Therefore, the workpiece must be actually machined and the phase error must be determined manually using a cam measuring device, resulting in poor workability. Further, since the follow-up delay of the spindle varies depending on the rotational speed of the spindle, the above method has a problem in that the phase error cannot be completely compensated for when the machining speed differs. The present invention has been made to solve the above problems, and its purpose is to easily compensate for phase errors.

[Means for resolving the point of view]

The structure of the invention for solving the above problems is based on profile data for numerically controlling the spindle and the tool feed axis and moving the tool to create a profile along the finished shape of the non-perfect circular workpiece. In a numerically controlled machine tool for machining a workpiece, an ideal profile data storage means for recording ideal profile data determined from the finished shape of the non-circular workpiece, and a current value of the spindle and a current value of the tool feed axis. profile measuring means for detecting the value to obtain measurement profile data indicating a relationship between the position of the tool feed axis with respect to the actual position of the main spindle; and measurement command means for instructing when to start driving the profile measuring means; a phase error calculating means for calculating a phase error by comparing the measured profile data measured by the profile measuring means and the ideal profile data; and offsetting the axis control by the phase error calculated by the phase error calculating means. This is because the offset means is provided.

[Effect]

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 a phase error calculation means, and a phase error is calculated. Next, the offset means offsets the axis control by the phase error. Therefore, by changing the rotational speed of the spindle and performing idle operation or spark-out machining, it is possible to automatically measure the phase error caused by the follow-up delay of the spindle servo system for each rotational speed of the spindle. Furthermore, the phase error is automatically compensated for by offsetting the axis control of the main spindle during processing.

【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 15 is placed on the right end of the table 11, and the center 16 of the tailstock 15 and the main shaft 13
A workpiece W consisting of a cam is held between the center 17 and the center 17 of the cam. The workpiece W is fitted into a positioning pin 18 protruding from the main shaft 13, and the rotational phase of the workpiece W matches the rotational phase of the main shaft 130. A tool stand 20 that can move forward and backward along a tool feed axis (X-axis) is guided behind the bed 10, and a motor 2 is attached to the tool stand 20.
A grinding wheel G which is rotationally driven by 1 is supported. 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. Drive units 40 and 41 input command pulses from numerical controller 30 and drive servo motors 23 and 14, respectively.
This is the circuit that drives the . Each servo motor 23.
A pulse generator 52.50 and a speed generator 53.51 are connected to the drive unit 14, and their outputs are fed back to each drive unit 40.41 for speed and position feedback control. The numerical control device 30 is mainly a servo motor 23.140
This is a device for controlling the grinding of a workpiece W by numerically controlling its rotation. The numerical control device 30 includes a tape reader 42 into which profile data, machining cycle data, etc. are input.
A keyboard 43 for inputting control data and the like, a CR7 display device 44 for displaying various information, and a control panel 45 for outputting various control signals are 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. l? On AM32, there are an NC data area 321 for storing NC data and an ideal profile data area 3 for storing ideal profile data determined from the finished shape of the workpiece W.
22 and a phase error storage area 328 for storing the phase error in accordance with the rotational speed of the spindle and the ideal profile data number. In addition, a feed mode setting area 324, a workpiece mode setting area 325, a spark-out mode setting area 326, and a phase error compensation mode setting area 327 are provided for setting various modes. The numerical control device 30 is also provided with a drive CPU 36, a RAM 35, and a pulse distribution circuit 37 as a drive system for the servo motors 23, 14. The RAM 35 is a storage device U that receives positioning data for the grinding wheel G from the main CPU 31. Drive CPU36
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 of target points, and outputs positioning data of interpolation points at regular intervals.The pulse distribution circuit 37 performs pulse distribution. This circuit later outputs a movement command pulse to each drive unit 40, 41. Furthermore, a sampling device 38 and a RAM 39 for storing sampling data are included as one element of the profile measuring means.
is provided. The sampling device 38 has counters 381 and 382 for counting the feedback pulses output from the pulse generators 52 and 50. Those counters 381 and 382 are reset by inputting a reset signal from the main CPU 31, and by inputting a measurement start signal from the main CPU 31, the counters 381 and 382 are set to the tool feed N (X-axis) and the main axis (C-axis).
Start counting the feedback pulses. In addition, the sampling device 1238 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 W45
When the button 451 is pressed, the flag of the phase error compensation mode setting amount v;c327 is reset, and the phase error measurement cycle data based on the 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 process proceeds to step 1 in order to determine a more detailed instruction code. Move to 6. In steps 106-120, mode setting is performed according to the instruction code. 00 at step 106
When it is determined that the code is 1, a flag is set in the feed mode setting area 324 in step 108, 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 650, 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 the code is determined to be a G52 code in step 122, 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. If it is determined in step 128 that it is a G55 code, sampling data is read from the RAM 39 in step 130, measured profile data is calculated from the data, and a phase error is calculated from comparison with ideal profile data. 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 workpiece mode is set to cam mode by the G51 code of block N11O, and the ideal profile data to be used is specified by the number P1234. Initial settings for sampling are performed by the G52 code of N120 of the next block, and a measurement start signal is output to the sampling device 38 by the G53 code of the next block N130. Also, due to the dwell code of G04 code, the depth of cut is 0 and the spindle rotation speed 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.
．． This is a table showing the amount of movement of the tool feed axis every 5 degrees in pulse numbers, and is referenced as D(I) 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 successive address! and offset address IO are both initialized to 1. The offset address IO 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 CPU 36, and it is determined whether or not 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 (1 ) is read out, and in step 308, the positioning data (travel amount and speed) of the grinding wheel G for each unit rotation angle of the spindle is stored in the drive CP.
It is output to RAM35 for passing to U36. Next, in step 310, it is determined whether the read address I is greater than or equal to the end address l14AX of the ideal profile data. When I≧l and AX, the read address I is set to the initial value 1 in step 312 in order to return to the top of the table.
If not, the read address I is updated by 1 in step 314. Next, in step 316, it is determined whether the read address 1 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 rotation speed of the spindle is is determined and the specified number of times (twice in the NC data in Figure 8)
If it is determined that the specified number of rotations has been completed, the program is terminated, and if it is determined that the specified number of rotations have not been completed, the process moves to step 304 and the next rotation cycle is 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 data is sampled and stored in the RAM 39. That is,
The sampling device 38 executes the process shown in FIG. 5 at a 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 address counter 3830 value I in the RAM 39.
(D address! JC (1) to MX (1) !,: In the storage step 404, the value ■ of the address counter 383 is updated by 1. Such processing is performed at the sampling period while the spindle rotates once. The sampling data is obtained repeatedly.Next, the phase error is calculated by the G55 code of block N140 according to the flowchart of FIG. 6.The sampling data obtained by the sampling device 38 is As shown in the figure, this is the current value at each fixed time interval.In step 500, the sampling data of the C-axis is interpolated to calculate the corresponding time for each unit rotation angle of the C-axis, and the
The current value of the axis is determined by interpolating the sampling data of the X-axis, and the current value of the X-axis corresponding to each unit rotation angle of the C-axis is determined. That is, sampling data is converted to measurement profile data. Next, in step 502, as shown in FIG. 11, the value θI of the C-axis when the X-axis takes the maximum value is determined from the ideal profile data, and in step 5
In step 04, 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
θ is written as tα in association with the ideal profile data number and the rotational speed of the spindle. 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. Q:1) When the phase error compensated processing control panel 45 button 452 is pressed, the processing cycle data shown in FIG. 9 is decoded block by block according to the flowchart shown in FIG. First, block N010
The G51 code sets the workpiece mode to the cam mode, and the ideal profile data to be used is specified by the number P1234. Next block NO2O
050 code, phase error compensation mode setting area 3
A flag is set in 27, and the control mode is set to a phase error compensation mode in which phase error compensation is performed on ideal profile data and processing is controlled. GO of next block N030
The I code sets the grinding feed mode, and the existence of the X code causes the grinding process to be performed using a force l of 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, the specified numerical values of the F code and the R code are the same, so the command is given to continuously cut at a constant speed with respect to the rotation of the main shaft. Cam generation with phase error compensation is performed according to the flowchart in FIG. First, in step 200, the depth of cut 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 ideal blower fill data number and the rotational speed of the main shaft, and the corresponding phase error is read out. Phase error Δθ
Since this is caused by the tracking delay of the spindle, it is possible to reduce the phase error by sequentially outputting ideal profile data that precedes the spindle command angle by Δθ in the spindle rotation angle. ili ffl
Can be done. Therefore, Δθ with respect to the origin of the command angle of the spindle
The address where the ideal profile data preceding the offset is stored, ie, the offset address 10, is calculated. Next, in step 204, the initial value of the read address I is set to the offset address IO. Next, in step 206, a pulse distribution completion signal is input from the drive cpIJa 6, and it is determined whether or not 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 208, and the ideal profile data D ( 1) is read out, and in step 210 it is determined whether cutting has been completed per rotation of the spindle. This determination is made using numerical data specified by F-hood. In this case, the determination is made based on whether or not a cut with a 0.1 distribution has been made. If the depth of cut per rotation of the spindle is not completed, the depth of cut per unit angle is added to the read ideal profile data D(I) in step 212 to generate travel amount data, and in step 214, the depth of cut per unit angle is generated. Positioning data that is a combination of movement amount data and speed data is output. Furthermore, when the cutting per rotation of the spindle has been completed, in step 213, the read ideal profile data D(1) is directly used as the entire movement data. Next, in step 216, it is determined whether the read address I is greater than or equal to the end address INAX of the ideal profile data. If I≧I
When the value is 0, the read address I is updated by 1. Next, in step 222, the read address I is set to the offset address rO.
It is determined whether or not they are equal to each other, and if they are equal, it means that the control of one rotation of the main shaft has been completed, and the step 224
It is determined whether or not the entire depth of cut has been completed. 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 N030 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 phase error compensation process of steps 322 and 324 similar to steps 202 and 204 is performed. After the initial settings, steps 304 and subsequent steps are executed. Further, this process differs only in the initial setting of the read address I and the offset address 0 in the control during phase error measurement. In other words, the corresponding phase error Δθ is calculated from the phase error table according to the ideal profile data and the spindle rotation speed.
is retrieved, and ideal profile data that precedes the command angle of the spindle by a phase error Δθ is sequentially output for a predetermined cycle, thereby performing spark-out machining with phase error compensation. In the above embodiment, the sampling device 38 samples the current values of the C-axis and the X-axis at regular time intervals, but the counter 382 that measures the current value of the C-axis is The configuration is such that a timing signal is output every time the
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. Moreover, the phase error Δθ 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. Further, in the above embodiment, a numerically controlled grinding machine has been described, but the present invention can also be applied to numerically controlled lathes and other numerically controlled machine tools.

【Effect of the invention】

The present invention detects the current value of the spindle and the current value of the tool feed axis in response to a measurement start command, measures measurement broil data that indicates the relationship between the position of the tool feed axis with respect to the actual spindle position, and The phase error is measured by comparing the profile data with the ideal profile data, and the axis control is offset by the phase error during machining, making it easy to compensate for the phase error and improving work efficiency. Also, depending on the workpiece profile and spindle rotation speed,
By providing a phase error storage means that stores the phase errors automatically measured by the above means as a table, and by offsetting the axis control with the phase error according to the profile of the workpiece and the rotational speed of the spindle during machining, it is possible to Even if the rotational speed of the object or spindle changes, the phase error will be compensated appropriately.
Even more effective.

[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 configuration diagram of machining 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. 10・'Bed 11゛...Table 1.3-・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 Toyota Machinery Co., Ltd. Representative Patent attorney Osamu Ichitani To So -〇 Figure 8 Figure 9 Figure 10 Figure 12

Claims (4)

[Claims] (1) In a numerically controlled machine tool that processes a non-circular workpiece based on profile data for numerically controlling the spindle and the tool feed axis and moving the tool to create a profile along the finished shape of the non-circular workpiece. , ideal profile data storage means for storing ideal profile data determined from the finished shape of the non-perfect circular workpiece; and detecting the current value of the spindle and the current value of the tool feed axis to determine the actual value of the spindle. profile measuring means for obtaining measurement profile data indicating the relationship of the position of the tool feed axis with respect to the position; measurement command means for instructing when to start driving the profile measuring means; and the measuring profile measured by the profile measuring means. A numerically controlled machine tool comprising: a phase error calculation means for calculating a phase error by comparing data with the ideal profile data; and an offset means for offsetting axis control by the phase error calculated by the phase error calculation means. (2) the phase error calculation means has a phase error storage means for storing the phase error according to the rotational speed of the main shaft;
The numerical control according to claim 1, wherein the offset means reads out a phase error corresponding to the rotational speed of the main shaft during machining from the phase error storage means, and offsets the axis control by the phase error. Machine Tools. (3) The phase error calculation means has a phase error storage means for storing the phase error according to the shape of the non-round workpiece, and the offset means is configured to store the phase error according to the shape of the non-round workpiece during machining. 2. A numerically controlled machine tool according to claim 1, wherein a corresponding phase error is read out from said phase error storage means, and axis control is offset by the phase error. (4) The phase error calculation means has a phase error storage means for storing the phase error according to the rotation speed of the spindle and the shape of the non-circular workpiece, and the offset means is configured to rotate the spindle during machining. A numerically controlled machine according to claim 1, characterized in that a phase error corresponding to the speed and the shape of the non-circular workpiece is read out from the phase error storage means, and the axis control is offset by the phase error. machine.