JP4082598B2 - Method and apparatus for correcting thermal displacement of numerically controlled machine tool - Google Patents

Description

  The present invention relates to a thermal displacement correction method and apparatus for a numerically controlled machine tool.

  In order to prevent machining defects due to thermal displacement of machine tools, it is important how to realize high-precision cutting. Care should be taken to maintain accuracy in machine manufacture. Even in the installation operation of the machine, in order to maintain accuracy, it is necessary to spend money on environmental facilities such as foundations, building structures, air-conditioning equipment, restrictions on the access of people and things, and so on.

Therefore, Japanese Unexamined Patent Publication No. 11-320331, obtained in advance the correspondence between the travel distance and the thermal displacement amount of the moving part, such as a table of a machine tool or head, to monitor the travel distance of the moving part, before SL corresponding There is shown a thermal displacement correction method for a machine tool that estimates the amount of thermal displacement from the relationship and corrects the moving part based on the estimated amount.

Further, Japanese Unexamined Patent Publication No. 11-320332, obtained in advance the correspondence between the rolling distance and thermal displacement of the spindle of a machine tool, to monitor the rolling distance of the main shaft, the thermal displacement amount from the previous SL relationship A thermal displacement correction method for a machine tool that estimates and corrects the spindle based on the estimation is shown.
JP 11-320331 A JP-A-11-320332

  However, due to differences in conditions such as the environment in which the machine tool is used, the spindle speed, and the feed rate, the measured temperature and the predicted machining accuracy are difficult to match.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal displacement correction method and apparatus for a numerically controlled machine tool that can perform high-accuracy machining by performing optimum correction according to the machining environment for poor accuracy due to thermal displacement. It is said.

  Examples of means for solving the problems in the present invention are as follows.

(1) A plurality of temperature sensors (S) are provided at predetermined positions of the machine tool (10),
Place the reference work (19) on the table (21),
The reference workpiece (19) is processed by the numerical controller (13) controlled by the tool (17) mounted on the spindle (15),
For each machining of the plurality of reference workpieces (19), the temperature change at a predetermined position of the machine tool (10) is measured by the temperature sensor (S), and the machining of the plurality of reference workpieces (19) is performed. The dimension of the predetermined position of each workpiece | work (19) after that is measured, and the correspondence of the dimension of the some workpiece | work (19) for reference | standard measured in this way and the temperature of the predetermined position of a machine tool (10) is calculated | required. Stored in advance in the temperature measurement correction system,
During actual machining of the workpiece (19), the temperature at a predetermined position of the machine tool (10) is monitored by the temperature sensor (S), and a plurality of reference workpieces (19) stored in the temperature measurement correction system are stored. Based on the correspondence between the dimensions and the temperature at a predetermined position of the machine tool (10), the actual workpiece (19) is machined,
Further, after machining the actual workpiece (19), the dimensional error of the actual workpiece (19) is measured, and the dimensional error is input to the numerical control device (13) to input the tool (17) and the table (21). A method comprising correcting a relative position.

(2) An input device 18 for inputting a dimensional error of the workpiece (19 ) actually processed is connected to the numerical control device (13), and the input device (18) is used for actual processing. The method as described above, wherein the dimensional error of the work (19) performed is input to the numerical controller (13).

( 3 ) The correction coefficient is calculated from the dimensional error after processing of the actual workpiece (19) and the temperature at the time of processing, and is transmitted to the temperature measurement correction system (Q). A method as described above, characterized in that the relative position of the tool (17) and the table (21) is corrected on the basis of it.

( 4 ) A tool in which a plurality of temperature sensors (S) are provided at predetermined positions of the machine tool (10), the workpiece (19) is installed on the table (21), and the workpiece (19) is mounted on the spindle (15). In a thermal displacement correction device for a numerically controlled machine tool that is controlled and processed by a numerical controller (13) according to (17),
Each of the respective processing of a plurality of workpieces (19) for the reference, the temperature change in the predetermined position of the machine tool (10) is measured by the temperature sensor (S), and a predetermined position of each workpiece (19) after processing the dimensions were measured, and relationship between the temperature of a predetermined position of the dimensions and the machine tool (10) of the workpiece for a plurality of reference (19) is determined, stored in advance in the temperature measurement correction system (Q) And
In actual machining of the workpiece (19), on the one hand, the temperature sensor (S) monitors the temperature at a predetermined position of the machine tool (10), and on the other hand, a plurality of reference values stored in the temperature measurement correction system. The actual workpiece (19) is machined based on the correspondence between the dimensions of the workpiece (19) and the temperature at a predetermined position of the machine tool (10) .
Further, after machining the actual workpiece (19), the dimensional error of the actual workpiece (19) is measured, and the dimensional error is input to the numerical control device (13) to input the tool (17) and the table (21). A thermal displacement correction device for a numerically controlled machine tool, wherein the relative position is corrected.

(5) An input device 18 for inputting a dimensional error of the workpiece (19 ) actually processed is connected to the numerical control device (13), and the input device (18) is used for actual processing. The above-described thermal displacement correction device for a numerically controlled machine tool, wherein the dimensional error of the workpiece (19) is input to the numerical controller (13).

( 6 ) The correction coefficient is calculated from the dimensional error after machining of the actual workpiece (19) and the temperature at the time of machining, and transmitted to the temperature measurement correction system (Q). The thermal displacement correction device for a numerically controlled machine tool as described above , wherein the relative positions of the tool (17) and the table (21) are corrected based on the correction.

ADVANTAGE OF THE INVENTION According to this invention, the precision defect by a thermal displacement can be suppressed and the highly accurate process according to the process environment can be performed.

  A typical example of a tool is a blade. In addition to the blade, a processing tool used for a machine tool may be used as a tool.

In the embodiment shown below, five temperature sensors for measuring the temperature change are provided in the machine tool, but the number may be more or less. You may correct | amend using all of several temperature sensors , and you may correct | amend using some.

  When measuring the dimensions of a predetermined position of the workpiece, it is preferable to measure the height, width, and depth, but one or two of these may be measured. You may measure the dimension of the other site | part of a workpiece | work.

The correspondence between the dimension at a predetermined position of the workpiece and the temperature can be obtained from the ratio between the dimension and the temperature. However, this correspondence may be obtained from an arbitrary function between dimensions and temperature.

  The dimensional error may be measured manually by an operator or automatically.

The correction factor can be obtained from the ratio between the dimensional error and the temperature. However, the correction factor may be obtained from an arbitrary function between the dimensional error and the temperature.

  As the relative position, it is preferable to use a displacement amount of the distance between the tool and the table as in the embodiment described below, but the distance between the tool and the table may be used.

  The feedback is preferably performed by calculating a correction coefficient from the dimensional error and the temperature, and replacing the correction coefficient and the corresponding relationship.

  In the embodiment described below, the machine tool, the temperature measurement correction system, the numerical control device, and the input device are separately configured, but some or all of them may be integrally configured. For example, the input device may be incorporated in the numerical control device, or the temperature measurement correction system may be provided in the numerical control device and attached integrally to the machine tool.

  According to the present invention, the dimensional error of the actually machined workpiece can be rewritten to the correspondence most suitable for the environment and machining conditions by feeding back to the correspondence between the temperature and the displacement determined in advance. A possible thermal displacement correction method and apparatus (having a learning function) can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a conceptual diagram showing an example of a thermal displacement correction method and apparatus for a numerically controlled machine tool according to the present invention.

  A thermal displacement correction apparatus 1 for a numerically controlled machine tool includes a machine tool 10. The machine tool 10 includes a base 11 on which a column 12 is formed in the vertical direction.

  A table 21 that is movable in a predetermined direction is disposed on the base 11.

  The table 21 is driven by a table driving mechanism having a servo motor 24. A work 19 is placed on the table 21.

  A spindle head (head) 14 is arranged in the column 12 so as to be movable in the vertical direction. The moving mechanism includes a servo motor 34 and is configured similarly to the moving mechanism of the table 21.

  A spindle 15 having a blade 17 as a tool of the present invention is disposed on the spindle head 14 so as to be rotatable at high speed. The main shaft 15 is driven by a main shaft drive motor 16.

A plurality of sensors S are attached to the machine tool 10. The sensor S is composed of a total of five sensors S1 to S5 in FIG. The sensors S1 to S5 transmit the measured temperature to a temperature measurement correction system Q described later. The sensor S1 measures the temperature near the main shaft 15. The sensor S2 measures the temperature near the spindle drive motor 16. Sensor S3 measures the temperature of column 12. Sensor S4 measures the temperature of the table drive mechanism. The sensor S5 measures the temperature of the table 21.

  The column 12 is connected to a temperature measurement correction system Q. The temperature measurement correction system Q includes a storage unit, and the storage unit stores a correspondence between the relative positions of the blade 17 and the table 21 and the temperature. The temperature measurement correction system Q outputs a correction value to the numerical controller 13 based on the correspondence between the temperature measured by the sensors S1 to S5 and the inside (A in the figure).

  A numerical controller 13 is connected to the column 12 via a temperature measurement correction system Q. The numerical controller 13 controls the moving mechanism of the spindle head 14, the spindle drive motor 16, the table 21, and the like.

The numerical controller 13 is connected to an input device 18 for inputting the dimensional error described above . Using the input device 18, the dimensional error of the workpiece 19 actually processed is input to the numerical control device 13.

  Next, an actual measurement example will be described.

  First, a plurality of reference workpieces 19 are machined. Here, the temperature change for each processing of each workpiece 19 is detected by the temperature sensors S1 to S5.

The dimension of each predetermined position of the reference workpiece 19 after machining is measured. In FIG. 1, the height W of the workpiece 19 is shown. In addition to measuring the height W of the workpiece 19, the width and depth are also measured.

  From the measured dimensions, a displacement amount (actual displacement) of the relative position between the blade 17 and the table 21 is obtained.

  2 to 4 show the measurement results according to the embodiment of the present invention.

  FIG. 2 is an embodiment of the present invention, and shows the relationship between the displacement amount, the correction value, and the number of workpieces about the X axis. FIG. 3 is an embodiment of the present invention, and shows the relationship between the displacement amount, the correction value, and the number of workpieces about the Y axis. FIG. 4 is an embodiment of the present invention, and shows the relationship between the amount of displacement, the correction value, and the number of workpieces about the Z axis. In each figure, the vertical axis represents the axial displacement (/ μm), and the horizontal axis represents the number of executions of the machining program, that is, the number of workpieces (/ piece).

  Each value in the figure is as follows.

Actual displacement: Displacement amount of the relative position of the blade 17 and the table 21 (value before correction)
Correction value: Displacement amount of the relative position calculated by multiplying the correspondence of the temperature measured by the temperature sensor (theoretical value)
Axial displacement; displacement amount of the relative position of the blade 17 and the table 21 (value after correction)
It can be seen that the actual displacement, that is, the amount of displacement of the relative positions of the blade 17 and the table 21 before correction increases as the number of workpieces increases.

  A correspondence relationship (not shown) between the actual displacement and the temperature at the time of measurement is obtained in advance. The correspondence is obtained from the ratio between the actual displacement and the temperature.

 When the actual workpiece 19 is processed, the temperature at a predetermined position of the machine tool 10 is monitored by the temperature sensors S1 to S5, and the actual workpiece 19 is processed based on the correspondence between the dimension and the temperature obtained from the reference workpiece. .

  Specifically, based on the displacement (correction value) of the relative position calculated by multiplying the correspondence with the temperature, the displacement of the relative position between the blade 17 and the table 21 is corrected, and the actual workpiece 19 is machined. .

  The dimension error of each workpiece 19 after machining is measured. Measurement is performed manually by the operator. The measurement may be automatically performed using an arbitrary device.

  Dimension error is fed back to the correspondence.

  Specifically, a dimensional error is input from the input device 18 to the numerical control device 13 (FIG. 1B), and the numerical control device 13 calculates a correction coefficient from the dimensional error and the temperature and transmits it to the temperature measurement correction system Q ( FIG. 1C). The correction factor in the temperature measurement correction system Q is replaced with a correspondence. The temperature measurement correction system Q corrects the relative positions of the tool 17 and the table 21 based on the replaced correction coefficient. The correction factor is obtained from the ratio between the dimensional error and the temperature.

  After the dimension error is fed back to the correspondence, the next workpiece 19 is processed.

  In this way, the workpiece 19 is sequentially processed.

  A displacement amount of the relative position of the tool 17 and the table 21 obtained by measuring the dimension of the workpiece 19 after processing is shown as an axial displacement. The axial displacement is almost zero, and the relative positions of the tool 17 and the table 21 hardly change. That is, the dimensional error is fed back to the correspondence relationship obtained in advance, and is an optimum value for the installation environment and processing conditions of the machine, and it can be seen that highly accurate thermal displacement correction is performed.

  Next, a comparative example of the present invention will be described.

  The measurement result by the comparative example of this invention is shown by FIGS.

  FIG. 5 is a comparative example of the present invention, and shows the relationship between the displacement amount, the correction value, and the number of workpieces about the X axis. FIG. 3 is a comparative example of the present invention, and shows the relationship between the displacement amount, the correction value, and the number of workpieces about the Y axis. FIG. 4 is a comparative example of the present invention, and shows the relationship between the amount of displacement, the correction value, and the number of workpieces about the Z axis. In each figure, the vertical axis represents the axial displacement (/ μm), and the horizontal axis represents the number of executions of the machining program, that is, the number of workpieces (/ piece).

  In the comparative example, the correspondence (not shown) between the actual displacement and the temperature at the time of measurement is obtained in advance, and the actual workpiece 19 is machined based on the correspondence, but the dimensional error is fed back to the correspondence. It has not been.

  As can be seen from the graph, the correction value calculated from the temperature does not necessarily match the actual displacement. This is because a dimensional error is not fed back to the correction value. The result of actual machining using this correction value is shown as the axial displacement. It can be seen that the axial displacement does not converge to 0, and high-precision machining cannot be performed.

It is a conceptual diagram which shows an example of the thermal displacement correction apparatus of the numerical control machine tool by this invention. It is an Example of this invention, and shows the relationship between the displacement amount about X-axis, a correction value, and the number of workpieces. It is an Example of this invention, and shows the relationship between the displacement amount about a Y-axis, a correction value, and the number of workpieces. It is an Example of this invention and shows the relationship between the displacement amount about the Z-axis, the correction value, and the number of workpieces. It is a comparative example of the present invention, and shows the relationship between the amount of displacement and the correction value about the X axis and the number of workpieces. It is a comparative example of the present invention, and shows the relationship between the displacement amount, correction value and the number of workpieces about the Y axis. It is a comparative example of the present invention, and shows the relationship between the amount of displacement, the correction value and the number of workpieces about the Z axis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal displacement correction apparatus 10 of a numerically controlled machine tool Machine tool 11 Base 12 Column 13 Numerical control apparatus 14 Spindle head (head)
15 Spindle 16 Spindle drive motor 17 Cutting tool 18 Input device 19 Work 21 Table 24 Servo motor 34 Servo motor Q Temperature measurement correction system S1, S2, S3, S4, S5 Sensor

Claims (6)

A plurality of temperature sensors (S) are provided at predetermined positions of the machine tool (10),
Place the reference work (19) on the table (21),
The reference workpiece (19) is processed by the numerical controller (13) controlled by the tool (17) mounted on the spindle (15),
For each machining of the plurality of reference workpieces (19), the temperature change at a predetermined position of the machine tool (10) is measured by the temperature sensor (S), and the machining of the plurality of reference workpieces (19) is performed. The dimension of the predetermined position of each workpiece | work (19) after that is measured, and the correspondence of the dimension of the some workpiece | work (19) for reference | standard measured in this way and the temperature of the predetermined position of a machine tool (10) is calculated | required. Stored in advance in the temperature measurement correction system,
During actual machining of the workpiece (19), the temperature at a predetermined position of the machine tool (10) is monitored by the temperature sensor (S), and a plurality of reference workpieces (19) stored in the temperature measurement correction system are stored. Based on the correspondence between the dimensions and the temperature at a predetermined position of the machine tool (10), the actual workpiece (19) is machined,
Further, after machining the actual workpiece (19), the dimensional error of the actual workpiece (19) is measured, and the dimensional error is input to the numerical control device (13) to input the tool (17) and the table (21). A method comprising correcting a relative position.   An input device 18 for inputting a dimensional error of the workpiece (19) actually processed is connected to the numerical control device (13), and the workpiece actually processed using the input device (18). The method according to claim 1, characterized in that the dimensional error of (19) is input to a numerical controller (13).  A correction coefficient is calculated from the dimensional error after processing of the actual workpiece (19) and the temperature at the time of processing and is sent to the temperature measurement correction system (Q). The method according to claim 1 or 2, characterized in that the relative positions of (17) and the table (21) are corrected. A plurality of temperature sensors (S) are provided at predetermined positions of the machine tool (10), the work (19) is placed on the table (21), and the work (19) is mounted on the spindle (15). In a thermal displacement correction device for a numerically controlled machine tool controlled and processed by a numerical controller (13)
For each processing of the plurality of reference workpieces (19), the temperature change at a predetermined position of the machine tool (10) is measured by the temperature sensor (S), and the predetermined position of each workpiece (19) after processing is measured. And the correspondence between the dimensions of the plurality of reference workpieces (19) and the temperature at a predetermined position of the machine tool (10) is obtained and stored in advance in the temperature measurement correction system (Q). And
In actual machining of the workpiece (19), on the one hand, the temperature sensor (S) monitors the temperature at a predetermined position of the machine tool (10), and on the other hand, a plurality of reference values stored in the temperature measurement correction system. The actual workpiece (19) is machined based on the correspondence between the dimensions of the workpiece (19) and the temperature at a predetermined position of the machine tool (10).
Further, after machining the actual workpiece (19), the dimensional error of the actual workpiece (19) is measured, and the dimensional error is input to the numerical control device (13) to input the tool (17) and the table (21). A thermal displacement correction device for a numerically controlled machine tool, wherein the relative position is corrected.  An input device 18 for inputting a dimensional error of the workpiece (19) actually processed is connected to the numerical control device (13), and the workpiece actually processed using the input device (18). The thermal displacement correction device for a numerically controlled machine tool according to claim 4, wherein the dimensional error of (19) is input to the numerical controller (13).  A correction coefficient is calculated from the dimensional error after processing of the actual workpiece (19) and the temperature at the time of processing and is sent to the temperature measurement correction system (Q). The thermal displacement correction device for a numerically controlled machine tool according to claim 4 or 5, wherein the relative positions of (17) and the table (21) are corrected.

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