JPH0622778B2 - Numerical control machine tool - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a numerically controlled machine tool for machining a non-round work piece such as a cam (hereinafter, also simply referred to as "workpiece").

[Prior art]

Conventionally, a method is known in which a numerical control device controls the feed of a grinding wheel in the direction perpendicular to the spindle axis in synchronization with the spindle rotation, and grinds a workpiece such as a cam. To control the feed of the grinding wheel synchronously, it is necessary to add profile data to the numerical controller. 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 reciprocates along the finished shape of the workpiece, that is, the profile generating movement. On the other hand, in order to grind a workpiece, in addition to the profile data, machining cycle data for controlling the machining cycle such as feed, cutting, and retreat of the grinding wheel is necessary. The workpiece is machined by numerically controlling the rotation of the spindle and the feed of the grinding wheel based on the machining cycle data and the profile data. Especially, the followability with respect to the command values of the spindle and the tool feed axis in the profile creation motion. The quality of is an important issue in terms of processing accuracy.

[Problems to be Solved by the Invention]

By the way, the following delay error is classified into a tool feed axis and a spindle. 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-round workpiece is actually machined based on the profile data, and the phase error of the machined workpiece is measured with a cam measuring device,
The initial position of the spindle is offset by this phase error when starting machining from the next machining. For this reason, it is necessary to actually process the workpiece and manually determine the phase error using the cam measuring device, resulting in poor workability. In addition, since the tracking delay of the spindle differs depending on the rotation speed of the spindle, the above method has a problem that the phase error cannot be completely compensated for when the machining speed is different. The present invention has been made to solve the above problems, and an object of the present invention is to facilitate the compensation of a phase error.

[Means for Solving the Problems] A structure of the invention for solving the above-mentioned problems is to numerically control a spindle and a tool feed shaft to move a tool to generate a profile along a finish shape of a non-round work piece. In a numerically controlled machine tool that processes non-round workpieces based on the profile data of, the ideal profile data storage means for storing the ideal profile data determined from the finished shape of the non-round workpiece and the ideal profile data Control means to control the spindle and tool feed axis to detect the current value of the tool feed axis corresponding to the position of the spindle and store it, and the phase error by comparing the data stored by the measuring means with the ideal profile data. And a offset for offsetting the ideal profile data based on the phase error calculated by the phase error calculating means. It is equipped with a means.

[Action]

For example, the measuring means detects the current value of the tool feed axis that corresponds to the current value of the spindle while performing idle operation based on the ideal profile data or when actually sparking out the workpiece. Store this data. This data is compared with the ideal profile data determined from the finished shape of the workpiece by the phase error calculation means to calculate the phase error. Next, the offset profile means offsets the ideal profile data based on the phase error. Therefore, by changing the rotation speed of the spindle and performing, for example, idle operation or spark-out machining, it is possible to automatically measure the phase error caused by the tracking delay of the spindle servo system for each rotation speed of the spindle. Moreover, during processing,
Since the ideal profile data is offset by the phase error, the processing error is automatically compensated.

【Example】

Hereinafter, the present invention will be described based on specific examples. FIG. 1 is a block diagram showing a numerical control grinding machine. Reference numeral 10 denotes a bed of a numerical control grinding machine, on which a table 11 is arranged slidably in the Z-axis direction parallel to the main axis. A headstock 12 having a main shaft 13 mounted thereon is arranged on the table 11, and the main shaft 13 is rotated by a servomotor 14. A tailstock 15 is placed on the right end of the table 11, and the center 16 and the spindle 13 of the tailstock 15 are mounted.
A workpiece W consisting of a cam is held by the center 17 of the. The workpiece W is fitted into the positioning pin 18 provided so as to project from the spindle 13, and the rotation phase of the workpiece W matches the rotation phase of the spindle 13. Behind the bed 10, a tool base 20 that can move forward and backward along a tool feed axis (X axis) is guided, and the tool base 20 has a motor 2
A grinding wheel G, which is rotatably driven by 1, is supported.
The tool base 20 is connected to a servo motor 23 via a feed screw (not shown) and is moved forward and backward by the forward and reverse rotation of the servo motor 23. The drive units 40 and 41 receive command pulses from the numerical control device 30 to drive the servomotors 23 and 14 respectively.
Is a circuit for driving. Each servo motor 23,
The pulse generators 52, 50 and the speed generators 53, 51 are coupled to the control unit 14, and the outputs of them are fed back to the drive units 40, 41 for feedback control of speed and position. The numerical controller 30 is a device that mainly controls the rotations of the servomotors 23 and 14 to control the grinding of the workpiece W. A tape reader 42 for inputting profile data, processing cycle data, etc. to the numerical controller 30.
A keyboard 43 for inputting control data and the like, a CRT 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 controller 30 mainly comprises a main CPU 31 for controlling the grinding machine, a ROM 33 storing a control program, a RAM 32 storing input data and the like, and an input / output interface 34.
On the RAM 32, an NC data area 321 for storing NC data and an ideal profile data area 32 for storing ideal profile data determined from the finish shape of the workpiece W are stored.
2 is provided with a phase error storage area 328 which stores the phase error 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, a spark out mode setting area 326, and a phase error compensation mode setting area 327 are provided. The numerical control device 30 further includes a drive CPU 36, a RAM 35, and a pulse distribution circuit 37 as a drive system for the servo motors 23 and 14. RAM35 is the main C
It is a storage device for inputting positioning data of the grinding wheel G from the PU 31. The drive CPU 36 is a device that numerically controls the 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 a fixed cycle. The pulse distribution circuit 37 is After pulse distribution, move command pulse is sent to each drive unit 4
It is a circuit for outputting to 0 and 41. Further, as one element of the profile measuring means, a sampling device 38 and a RAM 39 for storing sampling data.
Is provided. The sampling device 38 has counters 381 and 382 for counting the feedback pulses output from the pulse generators 52 and 50. The counters 381 and 382 are reset by inputting a reset signal from the main CPU 31, and a measurement start signal is input from the main CPU 31 to input a tool feed axis (X axis) and a spindle (C axis).
The counting of the feedback pulse of is started. Further, the sampling device 38 has an address counter 383 which is reset by a reset signal from the main CPU 31 and is updated at every sampling. When a measurement start signal is inputted, the values of the counters 381 and 382 are addressed at regular intervals. The data is output to the address of the RAM 39 indicated by the counter 383. Next, the operation will be described. The RAM 32 stores NC data including phase error measurement cycle data and machining cycle data. The data structure is shown in FIG. 8 for phase error measurement cycle data and in FIG. 9 for machining cycle data. Control board 45
When the button 451 is pressed, the flag in the phase error compensation mode setting area 327 is reset and the phase error measurement cycle data based on the ideal profile data is activated. When the button 452 on the control panel 45 is pressed, the machining cycle data is activated. These NC data are decoded by the CPU 31 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 judged whether or not it is a data end. In case of data end, this program is terminated. If it is not the data end, move to step 104 and below,
The code of the instruction word is determined. When it is determined in step 104 that the instruction word is the G code, the CPU processing is performed in step 10 to determine a more detailed instruction code.
Move to 6. In steps 106 to 120, the mode is set according to the instruction code. When it is determined to be the G01 code in step 106, the feed mode setting area 3 is set in step 108.
A flag is set in 24 and the feed mode is set to the grinding feed mode. Similarly, when it is determined to be the G04 code 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 the spark-out mode. When it is determined to be the G50 code in step 114, a flag is set in the phase error compensation mode setting area 327, and the control mode is set to the phase error compensation mode in which the phase error is offset by the phase error. Further, when it is determined to be the G51 code in step 120, the flag of the work mode setting area 325 is set in step 121 and the work mode is set to the cam mode. When the above mode setting is completed, the processing of the CPU shifts to step 122, and processing according to the NC data and the set mode is performed. When the G52 code is determined in step 122, a reset signal is output to the sampling device 38 in step 123, and the sampling conditions and the like are set. If it is determined to be G53 code in step 124, step
At 126, a measurement start signal is output to the sampling device 38. When it is determined to be the G55 code in step 128, the sampling data is read from the RAM 39 in step 130, the measurement profile data is calculated from the data, and the phase error is calculated from the comparison with the ideal profile data. Next, when it is determined in step 132 that there is an X code in the read block, the process proceeds to step 134 and the mode setting is cam mode and grinding feed mode (hereinafter, "cam / grinding mode").
Say. ) Or not is determined. In the cam / grinding mode, in step 140, pulse distribution for cam generation is performed. On the other hand, when the cam / grinding mode is not set, in step 136, pulse distribution is performed which is not synchronized with the normal rotation of the spindle. (a) Phase error measurement processing When the button 451 of 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 of FIG. First, the block
The workpiece mode is set to the cam mode by the G51 code of N110, and the ideal profile data used is designated by the number P1234. The G52 code of the N120 of the next block initializes the sampling, and the G53 code of the next block N130 causes the sampling device 38
A measurement start signal is output to. Further, only the profile creation motion of which the cutting amount is zero by the dwell code of the G04 code and the rotation speed of the main shaft is 10 rpm (S10 code) is processed by the procedure shown in FIG.
The ideal profile data is a table showing the amount of movement of the tool feed axis for each unit rotation angle of 0.5 ° of the spindle in the form of a pulse number.
Referenced by D (I). First, in step 300, the state of the phase error compensation mode setting area 327 is checked, but during the measurement processing of the phase error, the flag is reset and it is not in the phase error compensation mode, so the process proceeds to step 302,
Both the read address I and the offset address IO are initialized to 1. Here, the offset address IO is used for compensating the phase error and corresponds to the control start address of 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 is completed. If it is determined that the pulse distribution is completed, the process proceeds to step 306 and the ideal profile data D (I ) Is read out, and in step 308 the positioning data (movement amount and speed) of the grinding wheel G for each unit rotation angle of the spindle.
Is output to the RAM 35 for passing to the drive CPU 36. Next, at step 310, it is judged if the read address I is not less than the end address I _MAX of the ideal profile data. When I ≧ I _MAX , in step 312 the read address I is set to the initial value 1 to return to the beginning of the table,
Otherwise, the read address I is 1 in step 314.
Only updated. Next, at step 316, the read address I
Is equal to the offset address IO, and if it is equal, it means that the control of one rotation of the spindle has been completed, the process proceeds to step 318, the rotation speed of the spindle is determined, and If it is determined that the rotation has been performed only twice in the NC data of FIG. 8), this program ends, and if it is determined that the specified number of rotations has not ended, step 30
Then, the process proceeds to 4 and the control of the next rotation cycle is performed. As described above, the grinding wheel G performs the idle grinding or the spark-out processing only by the profile creating motion, and during this processing, the sampling device 38 sets the present value of the main spindle and the present value of the tool feed axis at a constant time interval. And the data is stored in the RAM 39. That is, the sampling device 38 executes the processing of FIG. 5 at the designated sampling cycle. At step 400, the value of the counter 382 and at step 402 the value of the counter 381 is stored in the addresses MC (I) and MX (I) of the RAM 39 indicated by the value I of the address counter 383, and at step 404, the value I of the address counter 383. Is updated by 1. Such processing is repeated at the sampling cycle while the main shaft makes one rotation, and sampling data is obtained. Next, the calculation of the phase error is performed according to the flowchart of FIG. 6 by the G55 code of block N140. The sampling data obtained by the sampling device 38 is C
Both the axis and the X-axis are current values at fixed time intervals as shown in FIG. In step 500, the sampling data of the C axis is interpolated to calculate the time corresponding to each unit rotation angle of the C axis, and the current value of the X axis for that time is interpolated with the sampling data of the X axis. Then, the current value of the X axis corresponding to each unit rotation angle of the C axis is calculated. That is, the sampling data is converted into measurement profile data. Next, at step 502, as shown in FIG. 11, the C-axis value θI when the X-axis takes the maximum value is obtained from the ideal profile data, and at step 504, when the X-axis takes the maximum value from the measured profile data. A value θM of the C axis of is obtained. Next, in step 506, the phase error Δθ
Is calculated by θM−θI, and the phase error Δθ is stored in association with the ideal profile data number and the rotation speed of the spindle. In this way, 1 according to the NC data of blocks N120 to N140
The phase error corresponding to one ideal profile data and the rotation speed of one spindle is measured. By performing the same measurement by changing the rotation speed of the spindle and the ideal profile data, the phase error table shown in FIG. 10 is obtained. It is created in the phase error storage area 328. (b) Processing Processing Compensating for Phase Error When the button 452 of the control panel 45 is pressed, the processing cycle data shown in FIG. 9 is decoded block by block according to the flowchart of FIG. First, block N010 G5
1 code sets the workpiece mode to CAM mode and the ideal profile data used is number P1
Specified by 234. A flag is set in the phase error compensation mode setting area 327 by the G50 code of N020 of the next block, and the control mode is set to the phase error compensation mode in which the ideal profile data is compensated for the phase error and the machining is controlled. The grinding feed mode is set by the G01 code of the next block N030, and the cam grinding process is performed by X-0.1 by the existence of the X code. The F code is the grinding amount per one rotation of the spindle, and the R code is the grinding speed per one rotation of the spindle. The S code represents the rotation speed of the spindle. In the NC data of FIG. 9, since the designated numerical values of the F code and the R code are equal, it is instructed to continuously cut at a constant speed with respect to the rotation of the spindle. The cam creation with the phase error compensated is executed according to the flowchart of FIG. First, at step 200, the cutting amount per unit rotation angle of 0.5 ° of the spindle is calculated from the given F code as the number of pulses. Then, in step 202, the 10th is calculated from the ideal profile data number and the rotation speed of the spindle.
The phase error table in the figure is searched and the corresponding phase error is read. Since the phase error Δθ is caused by the tracking delay of the spindle, Δθ is the rotation angle of the spindle relative to the command angle of the spindle.
The phase error can be compensated by sequentially outputting the ideal profile data that precedes each other. Therefore, the address at which the ideal profile data preceding the origin of the command angle of the main axis by Δθ is stored, that is, the offset address IO is calculated. Next, at step 204, the initial value of the read address I is set to the offset address IO. Then step 20
In step 6, 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 is completed. If it is determined that the pulse distribution is completed, the process proceeds to step 208 and the ideal profile data D (I) is read. Then, in step 210, it is determined whether or not the cutting per one rotation of the spindle has been completed. This judgment is made by the numerical data designated by the F code. In this case, it is determined whether or not a cut of 0.1 mm has been made. When the cutting per spindle revolution is not completed, the amount of cutting per unit angle is added to the read ideal profile data D (I) in step 212 to generate movement amount data, and in step 214, Positioning data which is a combination of movement amount data and speed data is output. When the cutting per revolution of the spindle has been completed, the read ideal profile data D (I) is directly used as the movement amount data in step 213. Next, at step 216, it is judged if the read address I is not less than the end address I _MAX of the ideal profile data. I ≧ I _MAX
If so, the read address I is set to the initial value 1 in step 218 in order to return it to the head of the table. Otherwise, the read address I is updated by 1 in step 220.
Next, at step 222, it is judged if the read address I is equal to the offset address IO, and if it is equal, it means that the control for one rotation of the spindle is completed.
In step 224, it is determined whether or not all the cuts have been completed. This determination is made based on the numerical data designated by the X code. Step 20 if all cuts have not been completed
Go to 6 and proceed to the next control cycle. On the other hand, when all the cuts have been completed, the cam grinding process commanded in block N030 is completed. Next, the spark-out process is processed by the procedure shown in FIG. 4 by the dwell code of the G04 code in block N040. This flowchart is substantially the same as the flowchart in FIG. 7, and is different in that the cutting is not performed and the dwell process is stopped when the main shaft rotates a specified number of times. That is, in step 300, the contents of the phase compensation mode setting area 327 are examined,
Since the flag is set and the phase compensation mode is set, after the initial setting for the phase error compensation processing of steps 322 and 324 similar to steps 202 and 204, step 304
The following is done: In addition, this processing is performed by the read address I and the offset address IO in the control during the phase error measurement.
The only difference is the initial setting of. That is, the corresponding phase error Δθ is searched from the phase error table according to the ideal profile data and the rotation speed of the spindle, and the ideal profile data preceding the command angle of the spindle by the phase error Δθ is sequentially output for a predetermined cycle. Thus, the spark-out processing in which the phase error is compensated is executed. In the above embodiment, the sampling device 38 samples the current values of the C-axis and the X-axis at fixed time intervals, but the counter 382 for measuring the current value of the C-axis rotates the C-axis by a unit angle. A timing signal is output each time
The current value of the axis may be sampled. In this case, for each unit rotation angle of the C axis, the corresponding X
The current value of the axis, ie the measurement profile data, can be obtained immediately. Further, the phase error Δθ is obtained by the phase difference of the maximum value on the X axis, but as shown in FIG. 11, the difference a between the rotation angles θ ₁ and θ ₂ and the rotation angle θ ₃ which make the values on the X axis the same. , Θ ₄ may be averaged. Further, although the numerical control grinder is described in the above embodiment, the present invention can be applied to a numerical control lathe and other numerical control machine tools.

【The invention's effect】

The present invention detects the current value of the spindle and the current value of the tool feed axis, measures data indicating the relationship between the actual position of the spindle and the position of the tool feed axis, and compares the data with the ideal profile data. Since the phase error is measured and the ideal profile data is offset based on the phase error at the time of machining, the phase error is easily compensated and the workability is improved. Also, depending on the profile of the workpiece and the rotation speed of the spindle,
By providing a phase error storage means for storing the phase error automatically measured by the above means in a table and offsetting the ideal profile data by the phase error according to the profile of the workpiece and the rotation speed of the spindle during machining, Even if the rotational speeds of the workpiece and the spindle change, appropriate phase error compensation is performed, which is even more effective.

[Brief description of drawings]

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 controller. FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are flowcharts showing the processing procedures 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, 13 ... Spindle, 1
4, 23 ... Servo motor, 15 ... Tailstock, 20 ...
Tool table, 30 ... Numerical control device, 50, 52 ... Pulse generator, 51, 53 ... Velocity generator, G ...
… Grinding wheel, W …… Workpiece

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Ota 1-1-1, Asahi-machi, Kariya city, Aichi Toyota Koki Co., Ltd. (56) References JP-A-59-19605 (JP, A) JP-A-61 -23213 (JP, A) JP-A-53-115986 (JP, A)

Claims (4)

[Claims] 1. A numerically controlled workpiece for machining a non-round workpiece based on profile data for numerically controlling a spindle and a tool feed shaft to cause a tool to generate a profile along a finished shape of a non-round workpiece. In the machine, ideal profile data storage means for storing ideal profile data determined from the finished shape of the non-round work piece, and the spindle and the tool feed shaft are controlled based on the ideal profile data to control the spindle. Measuring means for detecting and storing the current value of the tool feed axis corresponding to the position, and phase error calculating means for calculating the phase error by comparing the data stored by the measuring means with the ideal profile data, Offset means for offsetting the ideal profile data based on the phase error calculated by the phase error calculating means. A numerically controlled machine tool equipped. 2. The phase error calculating means has a phase error storing means for storing the phase error according to the rotation speed of the spindle, and the offset means corresponds to the rotation speed of the spindle during machining. Is read from the phase error storage means, and the ideal profile data is offset based on the phase error. The numerically controlled machine tool according to claim 1, wherein 3. The phase error calculation means has phase error storage means for storing the phase error according to the shape of the non-round work piece, and the offset means is for the non-round work piece during machining. The numerical control machine tool according to claim 1, wherein a phase error corresponding to a shape is read from the phase error storage means, and the ideal profile data is offset based on the phase error. 4. The phase error calculating means has a phase error storing means for storing the phase error in accordance with the rotational speed of the spindle and the shape of the non-round work piece, and the offset means has the phase error during machining. The phase error corresponding to the rotational speed of the spindle and the shape of the non-round work piece is read from the phase error storage means, and the ideal profile data is offset based on the phase error. The numerically controlled machine tool according to item 1.