JP2015104765A - Machine tool and processing control method of machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machine tool which can continue the high-accuracy processing of a workpiece even if an abnormality of a temperature sensor is detected, and a processing control method of the machine tool.SOLUTION: A numerical value control device 50 calculates an estimated temperature Tip of one temperature sensor STi on the basis of measured temperatures Tjd, Tkd of other two temperature sensors STj, STk. By this constitution, even if an abnormality of one temperature sensor STi caused by a failure or the like is detected, a position of each drive shaft of a machine tool 1 based on thermal displacement can be corrected. Therefore, the high-accuracy processing of a workpiece W can be continued, and the deterioration of the processing accuracy of the workpiece W and the lowering of productivity can be prevented.

Description

  The present invention relates to a machine tool including a control device that controls machining of a workpiece based on measured temperatures at a plurality of locations in a machine tool structure, and a machining control method for the machine tool.

  A machine tool control device processes a workpiece by controlling the position of each drive shaft. The structure of a machine tool may be thermally deformed due to heat generation due to internal factors such as machining with a tool or rotation of a motor, and heat transfer due to external factors such as room temperature fluctuations in the installation environment. The thermal deformation of the machine tool structure may cause a reduction in machining accuracy. For this reason, the machine tool control device corrects the position of each drive shaft based on the thermal displacement obtained from the measured temperatures of the temperature sensors installed at a plurality of locations in the structure of the machine tool. Processing is in progress.

  In the above-described machine tool, when the temperature sensor becomes abnormal due to a failure or the like, the correction accuracy of the position of each drive shaft based on the thermal displacement is adversely affected. For this reason, for example, in Patent Documents 1 and 2, the temperature of one temperature sensor is estimated from the temperature of one other temperature sensor, and one temperature sensor is calculated based on the difference between the measured temperature of one temperature sensor and the estimated temperature. There is described a machine tool that detects an abnormality of the above and prohibits the correction of the position of each drive shaft based on the thermal displacement when the abnormality is detected.

JP 2008-142844 A JP 2008-149415 A

  In the conventional machine tools described in Patent Documents 1 and 2, when abnormality of the temperature sensor is detected, correction of the position of each drive shaft based on thermal displacement is prohibited, so if the machining of the workpiece is continued as it is Machining accuracy deteriorates. For this reason, it is necessary to stop the machining of the workpiece until the abnormal temperature sensor is replaced with a normal temperature sensor, and there is a problem that the production efficiency of the workpiece is lowered.

  The present invention has been made in view of the above problems, and provides a machine tool capable of continuing high-precision machining of a workpiece even when a temperature sensor abnormality is detected, and a machining control method in the machine tool. Objective.

(Machine Tools)
(Claim 1) A machine tool of the present invention includes a plurality of temperature sensors capable of measuring temperatures at a plurality of locations, and a control device for controlling machining of a workpiece based on measured temperatures of the plurality of temperature sensors, The control device includes an estimated temperature calculation means for calculating a temperature at a location that can be measured by one of the temperature sensors as an estimated temperature based on measured temperatures of the other plurality of temperature sensors, and the one temperature sensor. Based on the measured temperature of the two temperature sensors and the estimated temperature, the calculation method updating means for updating the calculation method in the estimated temperature calculation means, and when the one temperature sensor is determined to be abnormal, updated before the determination Machining control means for controlling machining of the workpiece instead of the estimated temperature of the one temperature sensor calculated based on the calculated calculation method instead of the measured temperature of the one temperature sensor.

  As a result, the estimated temperature of one temperature sensor is calculated based on the measured temperatures of a plurality of other temperature sensors, so even if an abnormality due to a failure of one temperature sensor is detected, a machine tool based on thermal displacement The position of each drive shaft can be corrected. Therefore, highly accurate machining of the workpiece can be continued, and deterioration of workpiece machining accuracy and productivity can be prevented.

  (Claim 2) The calculation method updating means may update the calculation method based on a temperature change rate of at least one of a measured temperature and an estimated temperature of the one temperature sensor. Thereby, since the calculation method is sequentially updated based on the temperature change rate of one temperature sensor, the accuracy of the estimated temperature when one temperature sensor becomes abnormal due to a failure or the like can be improved.

  (Claim 3) The calculation method updating means may update the calculation method based on a temperature change rate of measured temperatures of the plurality of temperature sensors. Thereby, since the calculation method is sequentially updated based on the temperature change rates of the plurality of temperature sensors, the accuracy of the estimated temperature when one temperature sensor becomes abnormal due to a failure or the like can be improved.

  (Claim 4) The calculation method update means may determine a coefficient pattern representing a coefficient of a temperature estimation formula used in the calculation method based on the temperature change rate. As a result, the coefficient pattern representing the coefficient of the temperature estimation formula is determined based on the temperature change rate of one temperature sensor or a plurality of temperature sensors. Therefore, the accuracy of the estimated temperature of one temperature sensor obtained by the temperature estimation formula is increased. Can be increased.

  (Claim 5) The coefficient pattern is divided into a case where the rate of change in temperature rises above a certain rate of change, a case where it falls below the constant rate of change, or a case where it changes below the constant rate of change. It should be set. Thereby, since the coefficient pattern representing the coefficient of the temperature estimation formula is classified according to the temperature change rate of one temperature sensor or a plurality of temperature sensors, the accuracy of the coefficient of the temperature estimation formula can be improved.

  (Claim 6) The calculation method updating means may optimize the coefficient of the temperature estimation formula. Since the coefficient of the temperature estimation formula is optimized, the accuracy of the estimated temperature of one temperature sensor obtained by the temperature estimation formula can be further increased.

(Machining control method for machine tools)
(Claim 7) A machining control method in a machine tool for machining a workpiece on the basis of measured temperatures of a plurality of temperature sensors capable of measuring temperatures at a plurality of locations, respectively, wherein one temperature sensor can be measured. An estimated temperature calculation step of calculating the temperature of a certain point as an estimated temperature based on the measured temperatures of the other temperature sensors, and the estimated temperature based on the measured temperature of the one temperature sensor and the estimated temperature. A calculation method updating step for updating a calculation method in the calculation means, and an estimated temperature of the one temperature sensor calculated based on the calculation method updated before the determination when it is determined that the one temperature sensor is abnormal And a machining control step for controlling machining of the workpiece instead of the temperature measured by the one temperature sensor.
Thereby, there exists an effect similar to the effect of the said machine tool.

It is a side view showing the whole machine tool composition concerning an embodiment of the invention. It is a block diagram which shows the numerical control apparatus of the machine tool of FIG. It is a flowchart for demonstrating the abnormality determination processing operation | movement of the numerical control apparatus of FIG. 3 is a flowchart for explaining a temperature estimation formula update processing operation of the numerical controller of FIG. 2. 3 is a flowchart for explaining a calculation processing operation of an estimated temperature after an abnormality of the numerical control device of FIG. 2. It is a figure which shows when the measurement temperature of one temperature sensor rises more than a fixed raise rate of change. It is a figure which shows when the measurement temperature of one temperature sensor falls below a fixed fall change rate. It is a figure which shows when the measurement temperature of one temperature sensor changes with time between a fixed rising change rate and falling change rate. It is a figure which shows when the measurement temperature of two temperature sensors rises more than a fixed raise change rate. It is a figure which shows when the measurement temperature of two temperature sensors falls below a fixed fall change rate. It is a figure which shows when the measurement temperature of two temperature sensors changes with time between a fixed rise change rate and fall change rate.

(Schematic configuration of machine tool)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of a machine tool according to the invention will be described with reference to the drawings. As a machine tool, a three-axis machining center will be described as an example. That is, the machine tool is a machine tool having three rectilinear axes (X, Y, Z axes) orthogonal to each other as drive axes.

As shown in FIG. 1, the machine tool 1 includes a bed 2, a column 10, a saddle 20, a rotary spindle 30, a table 40, a numerical controller 50, and the like. The workpiece W is a workpiece to be processed by the machine tool 1.
The bed 2 is installed on the floor surface, and a pair of rails 3 extending on the upper surface in the X-axis direction (horizontal direction) and a pair of rails extending in the Z-axis direction (horizontal direction) orthogonal to the X-axis direction. 4 is provided.

The column 10 is engaged with a pair of rails 3 so as to be movable in the X-axis direction with respect to the bed 2 by an unillustrated X-axis motor. A pair of rails 5 extending in the X-axis direction and the Y-axis direction (vertical direction) orthogonal to the Z-axis direction are provided on the front side surface of the column 10.
The saddle 20 is engaged with a pair of rails 5 so as to be movable in the Y-axis direction with respect to the column 10 by an unillustrated Y-axis motor.

The rotation main shaft 30 is provided so as to be rotatable around an axis by a main shaft motor (not shown) accommodated in the saddle 20. The rotary tool 31 is fixed to the tip of the rotary spindle 30 and rotates with the rotation of the rotary spindle 30. Further, the rotary tool 31 moves in the X-axis direction and the Y-axis direction with respect to the bed 2 as the column 10 and the saddle 20 move. The rotating tool 31 is, for example, a ball end mill, an end mill, a drill, or a tap.
The table 40 is engaged with a pair of rails 4 so as to be movable in the Z-axis direction with respect to the bed 2 by an unillustrated Z-axis motor. The workpiece W is magnetically attracted to the upper surface of the table 40.

The numerical control device 50 drives and controls the column 10, the saddle 20, the rotation spindle, and the motors of the table 40 based on the numerical control data, and performs processing by moving the rotary tool 31 relative to the workpiece W. .
A temperature sensor STi, STj, STk, etc. such as a thermistor is attached to each part of the structure of the machine tool 1 in order to perform thermal displacement correction based on the measured temperature of each part or an estimated temperature described later. It is worn. 1 ≦ i ≦ n, i ≠ j ≠ k, n: the total number of temperature sensors. Each temperature sensor STi, STj, STk... Measures temperature at each installed location and outputs a signal corresponding to the measured temperature to the numerical controller 50. In addition, in FIG. 1, the example of the sticking state of temperature sensor STi, STj, STk ... in the bed 2 and the column 10 is shown.

(Configuration of numerical controller)
As shown in FIG. 2, the numerical control device 50 includes a sensor signal input unit 51, an abnormality determination unit 52, an estimated temperature calculation unit 53, a calculation method update unit 54, a processing control unit 55, and a warning unit 56. Storage unit 57 and the like. Furthermore, the calculation method update unit 54 includes a temperature change rate calculation unit 61, a pattern determination unit 62, an optimization calculation unit 63, an update unit 64, and the like.

  Here, the sensor signal input unit 51, abnormality determination unit 52, estimated temperature calculation unit 53, calculation method update unit 54, processing control unit 55, warning unit 56, storage unit 57, temperature change rate calculation unit 61, pattern determination unit 62 The optimization calculation unit 63 and the updating unit 64 can be configured by individual hardware, or can be configured by software.

  The sensor signal input unit 51 inputs detection signals from the temperature sensors STi, STj, STk,... At a predetermined sampling time set in advance and stored in the storage unit 57, and the machine tool is input to the storage unit 57. , And a time t are stored in association with each measured temperature Tid, Tjd, Tkd...

  Abnormality determination unit 52 determines whether each temperature sensor STi, STj, STk... Is operating normally or abnormally. That is, for example, when the difference between the measured temperature Tid of the temperature sensor STi and the estimated temperature Tip described later varies within a preset range, the abnormality determination unit 52 operates normally. And when it fluctuates beyond the set range, it is determined that the temperature sensor STi is operating abnormally. When the detection signal from the temperature sensor STi varies within a preset range, it is determined that the temperature sensor STi is operating normally. When the detection signal varies beyond the set range, the temperature sensor STi Is determined to be operating abnormally.

  The estimated temperature calculation unit 53 converts the temperature at a location where one temperature sensor can be measured among the temperature sensors STi, STj, STk,... To the measurement temperatures of the other plural (two in this example) temperature sensors. Based on this, it is calculated as an estimated temperature and stored in the storage unit 57 as a temperature change rate in association with the time t. The combination of the other two temperature sensors with respect to one temperature sensor is determined in advance and stored in the storage unit 57 according to the same location or the location where the heat source is at substantially the same temperature by experiments or the like. For example, as shown in the following equation (1), the estimated temperature Tip of one temperature sensor STi is represented by the measured temperatures Tjd and Tkd of the two temperature sensors STj and STk. The coefficients α and β in the following equation (1) will be described later.

  The calculation method updating unit 54 calculates the temperature in the estimated temperature calculation unit 53 based on the temperature change rate of the measured temperature when one temperature sensor is normal, and the temperature change rate of the estimated temperature when one temperature sensor is abnormal. Update method. As a result, when one temperature sensor is normal, the calculation method is sequentially updated based on the rate of temperature change of one temperature sensor, so the estimated temperature when one temperature sensor becomes abnormal due to a failure or the like is calculated. Accuracy can be increased. In addition, when one temperature sensor is abnormal, it is sequentially updated based on the temperature change rate of the two temperature sensors, so that the accuracy of the estimated temperature when one temperature sensor becomes abnormal due to a failure or the like can be improved. it can.

  The calculation method update in the calculation method updating unit 54 is performed for all temperature sensors STj, STk,. In the following, for convenience of explanation, one temperature sensor is STi, and the other two temperature sensors are STj and STk. A case where one temperature sensor STi is normal and a case where it is abnormal will be described separately.

First, a case where one temperature sensor STi is normal will be described.
The temperature change rate calculation unit 61 is a predetermined update measurement time set in advance and stored in the storage unit 57, for example, a measurement time from a time point measured immediately before the start of calculation to a time point before a predetermined time. The rate of change γi of the measured temperature Tid per fixed time of STi is calculated. For example, as shown in FIGS. 6A to 6C, when the measurement temperature T is taken on the vertical axis and the time t is taken on the horizontal axis, the measurement temperature Tid per fixed time of one temperature sensor STi in the update measurement times t1 to t2 is calculated. The change rate γi is expressed by the following equation (2).

  The pattern determination unit 62 uses the coefficients α and β used in the temperature estimation formula of Equation (1) based on the rate of change γi of the measured temperature Tid per fixed time of one temperature sensor STi calculated by the temperature change rate calculation unit 61. Is determined. Thereby, the precision of the estimated temperature Tip of one temperature sensor STi calculated | required by temperature estimation formula (Formula (1)) can be improved.

  As the coefficient pattern, for example, as shown in FIG. 6A, when the rate of change γi of one temperature sensor STi increases at a certain increase rate of change γa, the following equation (1) 3) and (4) (referred to as an increase coefficient pattern), as shown in FIG. 6B, when the rate of decrease is below a certain decrease rate of change −γb, the following equations (5) and (5) ( 6) (referred to as a descending coefficient pattern), and as shown in FIG. 6C, when it changes with time between a constant ascending rate of change γa and a descending rate of change -γb, the following equation (7 ), (8) (referred to as a steady coefficient pattern). Thereby, the precision of the coefficients α and β of the temperature estimation formula (formula (1)) can be increased. In addition, A1 to F1 of each of the formulas (3) to (8) are inclinations when graphed, and A2 to F2 are Tid-intercepts when graphed.

  The optimization calculation unit 63 optimizes the temperature estimation formula (formula (1)), for example, coefficients α and β that minimize the formula of the least square method expressed by the following formula (9), that is, pattern determination The coefficients α and β of the coefficient pattern determined by the unit 62 are obtained. Thereby, the precision of the estimated temperature Tip of one temperature sensor STi calculated | required by temperature estimation formula (Formula (1)) can be improved further.

  The update unit 64 updates the temperature estimation formula by applying the coefficients α and β calculated by the optimization calculation unit 63 to the temperature estimation formula (Formula (1)). The update unit 64 stores the temperature estimation formula (formula (1)) in the storage unit 57 for each of the three coefficient patterns.

Next, a case where one temperature sensor STi is abnormal will be described.
The temperature change rate calculating unit 61 changes the measured temperatures Tjd and Tkd per fixed time of the other two temperature sensors STj and STk described above at a predetermined update measurement time set in advance and stored in the storage unit 57. The rates γj and γk are calculated. For example, as shown in FIGS. 7A to 7C, when the measurement temperature T is taken on the vertical axis and the time t is taken on the horizontal axis, the rate of change γj of the measurement temperatures Tjd and Tkd per certain time in the update measurement times t1 to t2. γk is expressed by the following equations (10) and (11).

  The pattern determination unit 62 calculates the temperature estimation formula (formula (1)) based on the rate of change γj and γk of the measured temperatures Tjd and Tkd per fixed time of the two temperature sensors STj and STk calculated by the temperature change rate calculation unit 61. ) Is used to determine the coefficient pattern representing the coefficients α and β. Thereby, the precision of the estimated temperature Tip of one temperature sensor STi calculated | required by temperature estimation formula (Formula (1)) can be improved.

  As the coefficient pattern, for example, as shown in FIG. 7A, when the change rates γj and γk of the temperature sensors STj and STk increase at a certain increase change rate γa, a linear function of the change rates γj and γk is used. When the following equations (12) and (13) (referred to as an increase coefficient pattern) are used and the rate of decrease is less than a constant decrease rate of change -γb as shown in FIG. 7B, the following is a linear function of the change rates γj and γk. Equations (14) and (15) (referred to as a descending coefficient pattern), and as shown in FIG. 7C, when the time-varying change occurs between a constant increase rate γa and a decrease rate of change −γb, the change rates γj and γk The following equations (16) and (17) (referred to as steady coefficient patterns) which are linear functions are used.

  The rate of change γj, γk of the temperature sensors STj, STk rises when one rises, and the other falls when one falls. The reason why the change rate γj of the temperature sensor STj and the change rate γk of the temperature sensor STk exhibit the same change tendency is that the structure of the machine tool 1 does not undergo a rapid temperature change. Thereby, the precision of the coefficients α and β of the temperature estimation formula (formula (1)) can be increased. Note that G1 to L1 in each of the equations (12) to (17) are inclinations when graphed, and G2 to L2 are Tjd and Tkd-intercept when graphed.

  The optimization calculation unit 63 optimizes the temperature estimation formula (formula (1)), for example, coefficients α and β that minimize the formula of the least square method represented by the following formula (18), that is, pattern determination The coefficients α and β of the coefficient pattern determined by the unit 62 are obtained. Thereby, the precision of the estimated temperature Tip of one temperature sensor STi calculated | required by temperature estimation formula (Formula (1)) can be improved further.

The update unit 64 updates the temperature estimation formula by applying the coefficients α and β calculated by the optimization calculation unit 63 to the temperature estimation formula (Formula (1)). The update unit 64 stores the temperature estimation formula (formula (1)) in the storage unit 57 for each of the three coefficient patterns.
In the above description, the coefficients α and β calculated based on the measured temperatures Tjd and Tkd of the other two temperature sensors STj and STk are applied to the temperature estimation equation (Equation (1)) to obtain the temperature estimation equation. Although updated, the coefficients α and β calculated based on the average value (Tjd + Tkd) / 2 of the measured temperatures Tjd and Tkd of the other two temperature sensors STj and STk are expressed in the temperature estimation formula (formula (1)). The temperature estimation formula may be applied and updated. Alternatively, the coefficients α and β calculated based on the measured temperature Tip of one temperature sensor STi may be applied to the temperature estimation formula (formula (1)) to update the temperature estimation formula.

  When the determination result from the abnormality determination unit 52 is normal, the machining control unit 55 outputs the position command of the rotary tool 31 described in the numerical control data to each temperature sensor STi, STj, The thermal displacement is corrected based on the measured temperatures Tid, Tjd, Tkd,. Based on the correction position command of the rotary tool 31, the column 10, the saddle 20, the rotary spindle, the shaft motors of the table 40 and the like are driven and controlled.

  Further, when the determination result from the abnormality determination unit 52 indicates that one temperature sensor STi is abnormal, the machining control unit 55 updates the position command of the rotary tool 31 described in the numerical control data immediately before the determination. Estimated temperature Tip of one temperature sensor STi according to the temperature estimation formula (formula (1)) and measured temperatures Tjd, Tkd... Of other temperature sensors STj, STk. Based on this, the thermal displacement is corrected. Based on the correction position command of the rotary tool 31, the column 10, the saddle 20, the rotary spindle, the shaft motors of the table 40 and the like are driven and controlled.

Thereafter, when the rate of change γi of the estimated temperature Tip of one temperature sensor STi changes, one temperature sensor based on the temperature estimation formula (Equation (1)) updated and stored with the coefficient pattern corresponding to the change. The thermal displacement is corrected based on the estimated temperature Tip of STi and the measured temperatures Tjd, Tkd... Of other temperature sensors STj, STk. Based on the correction position command of the rotary tool 31, the column 10, the saddle 20, the rotary spindle, the shaft motors of the table 40, and the like are driven and controlled.
The warning unit 56 warns with a display or a sound for specifying the temperature sensor STi in order to make the operator recognize the temperature sensor STi for which the determination result from the abnormality determination unit 52 is abnormal.

  The storage unit 57 stores measured temperatures Tid, Tjd, Tkd... Based on detection signals from the respective temperature sensors STi, STj, STk..., Estimated temperatures Tip calculated by the respective temperature sensors STi, STj, STk. , Tjp, Tkp,..., Predetermined sampling time when the detection signals from the temperature sensors STi, STj, STk,... Are input, and the other two temperature sensors STj, STk with respect to one temperature sensor STi. The combination is stored.

  Further, a temperature estimation formula (equation (1)) for each coefficient pattern for calculating the estimated temperature Tip of one temperature sensor STi, and a change rate γi of the measured temperature Tid per fixed time of one temperature sensor STi are calculated. Expression (equation (2)), a predetermined update measurement time when calculating the change rate γi, and coefficients α and β based on the change rate γi of the measured temperature Tid per fixed time of the temperature sensor STi. A coefficient pattern (expressions (3) to (8)) and a temperature estimation expression (expression (1)) for optimizing the least square method (expression (9)) are stored.

  Further, arithmetic expressions (formulas (10) and (11)) for calculating the change rates γj and γk of the measured temperatures Tjd and Tkd per fixed time of the two temperature sensors STj and STk, and the change rates γj and γk. Is a coefficient pattern (expressions (12) to (12)) that represents coefficients α and β based on a predetermined measurement time for updating and a rate of change γj and γk of the measured temperature Tjd and Tkd per fixed time of the temperature sensors STj and STk. 17)), a least squares equation (equation (18)) for optimizing the temperature estimation equation (equation (1)) and the like are stored.

(Operation of numerical controller)
The abnormality determination processing operation, temperature estimation formula update processing operation, and estimated temperature calculation processing operation after abnormality will be described with reference to the flowcharts of FIGS. 3 to 5. For convenience of explanation, one temperature sensor STi and two temperature sensors STj and STk combined with the temperature sensor STi will be described.

  First, the abnormality determination process will be described with reference to FIG. As shown in FIG. 3, the temperature is measured by each temperature sensor STi, STj, STk (step S1). Specifically, the sensor signal input unit 51 reads a sampling time from the storage unit 57, inputs a detection signal from each temperature sensor STi, STj, STk for each sampling time, and each measured temperature Tid, Tjd, Tkd The time t is associated and stored in the storage unit 57 as a temperature change rate.

  Then, as shown in FIG. 3, the estimated temperature Tip of the temperature sensor STi is calculated based on the temperature estimation formula (formula (1)) (step S2). Specifically, the estimated temperature calculation unit 53 reads the measured temperatures Tjd and Tkd of the two temperature sensors STj and STk corresponding to one temperature sensor STi from the storage unit 57, and the two temperature sensors STj and STk of the read temperature sensors STj and STk. The estimated temperatures Tip of one temperature sensor STi are obtained by substituting the measured temperatures Tjd and Tkd into the temperature estimation formula (formula (1)) updated immediately before.

  Next, as shown in FIG. 3, it is determined whether or not an abnormality has occurred in one temperature sensor STi (step S3). Specifically, the abnormality determination unit 52 determines whether or not the measured temperature Tid of one temperature sensor STi varies within the allowable error ΔT of the estimated temperature Tip (Tip−ΔT ≧ Tid ≧ Tip + ΔT). . When the measured temperature Tid of one temperature sensor STi fluctuates within the range of the allowable error ΔT of the estimated temperature Tip, no abnormality occurs in the temperature sensor STi, and it is determined that the temperature sensor STi is normal. (Step S4).

  On the other hand, in step S3, when the measured temperature Tid of one temperature sensor STi fluctuates beyond the allowable error ΔT of the estimated temperature Tip, an abnormality has occurred in the temperature sensor STi. (Step S5). Then, as shown in FIG. 3, a warning is given that one temperature sensor STi has failed (step S6). Specifically, the warning unit 56 gives a warning with a display or a sound for specifying the temperature sensor STi so that the operator can recognize the temperature sensor STi where the abnormality has occurred.

  Next, the temperature estimation formula update process will be described with reference to FIG. As shown in FIG. 4, when one temperature sensor STi is normal, machining control is performed based on the measured temperatures Tid, Tjd, Tkd of the temperature sensors STi, STj, STk (step S11). Specifically, the machining control unit 55 reads the measured temperatures Tid, Tjd, Tkd of the temperature sensors STi, STj, STk from the storage unit 57, and reads the position command of the rotary tool 31 described in the numerical control data. The thermal displacement is corrected based on the measured temperatures Tid, Tjd, Tkd of the temperature sensors STi, STj, STk. Based on the correction position command of the rotary tool 31, the column 10, the saddle 20, the rotary spindle, the shaft motors of the table 40 and the like are driven and controlled.

  Then, as shown in FIG. 4, the rate of change γi of the measured temperature Tid per fixed time of one temperature sensor STi is calculated (step S12). Specifically, the temperature change rate calculation unit 61 reads the measurement temperature Tid of one temperature sensor STi at the sampling times t1 to t2 from the storage unit 57, and calculates the change rate γi of the measurement temperature Tid per fixed time by an equation ( It is obtained by equation (2)).

  Next, as shown in FIG. 4, the coefficients α and β used in the temperature estimation formula (formula (1)) are expressed based on the obtained change rate γi of the measured temperature Tid per fixed time of one temperature sensor STi. A coefficient pattern is determined (step S13). Specifically, the pattern determination unit 62 determines whether the rate of change γi of one temperature sensor STi increases at a certain rate of change γa or below, or falls at a rate of constant rate of minus γb or below, or a constant rate of change of increase. It is determined whether it changes with time between γa and the decrease rate of change −γb, and according to the determination result, expressions (3) and (4) that are increase coefficient patterns from the storage unit 57, or expression (5) that is a decrease coefficient pattern , (6), or equations (7) and (8) which are steady coefficient patterns are determined and read out.

  Next, as shown in FIG. 4, the temperature estimation formula (formula (1)) is optimized based on the determined coefficient pattern (step S14). Specifically, the optimization calculation unit 63 applies the determined ascending coefficient pattern, descending coefficient pattern, or stationary coefficient pattern to the least square method expression (Expression (9)), and the least square method expression (Expression (9) )) To minimize the coefficients α and β.

Next, as shown in FIG. 4, the temperature estimation formula (formula (1)) is updated based on the obtained coefficients α and β (step S15). Specifically, the update unit 64 corresponds to the coefficient pattern determined this time among the temperature estimation formulas (expression (1)) of the increase coefficient pattern, the decrease coefficient pattern, and the steady coefficient pattern stored in the storage unit 57. The temperature estimation formula (formula (1)) is updated by applying the obtained coefficients α and β to the temperature estimation formula (formula (1)).
Then, as shown in FIG. 4, it is determined whether or not machining control is to be continued (step S16). If machining control is to be continued, the process returns to step S11 and the above processing is repeated, and machining control is not to be continued. End all processing.

  Next, calculation processing of the estimated temperature after abnormality will be described with reference to FIG. As shown in FIG. 5, when one temperature sensor STi is abnormal, an abnormality has occurred based on the measured temperatures Tjd and Tkd of the two temperature sensors STj and STk and the temperature estimation formula (formula (1)). The estimated temperature Tip of the temperature sensor STi is calculated (step S21).

  Specifically, the estimated temperature calculation unit 53 reads the measured temperatures Tjd and Tkd of the two temperature sensors STj and STk corresponding to one temperature sensor STi from the storage unit 57, and the two temperature sensors STj and STk of the read temperature sensors STj and STk. An estimated temperature Tip of one temperature sensor STi is obtained by substituting the measured temperatures Tjd and Tkd into the temperature estimation formula (formula (1)). As the temperature estimation formula (formula (1)), the formula updated immediately before one temperature sensor STi becomes abnormal is used, and thereafter the rate of change of the measured temperatures Tjd and Tkd of the two temperature sensors STj and STk. An expression corresponding to the coefficient pattern determined by γj and γk is used.

Then, as shown in FIG. 5, the numerical control data is described based on the estimated temperature Tip of one temperature sensor STi and the measured temperatures Tjd and Tkd of two temperature sensors STj and STk by the same process as the process of step S11. The position command of the rotary tool 31 thus corrected is subjected to thermal displacement correction to control the machining of the workpiece W (step S22).
Then, as shown in FIG. 5, the rate of change γj, γk of the measured temperatures Tjd, Tkd of the two temperature sensors STj, STk is calculated by the same process as the process of step S12 (step S23).

Next, as shown in FIG. 5, the temperature estimation formula (formula (1)) is selected from the storage unit 57 based on the obtained change rates γj and γk of the measured temperatures Tjd and Tkd of the two temperature sensors STj and STk. (Step S24). That is, since the storage unit 57 stores the equations (3) to (8) of the rising coefficient pattern, the falling coefficient pattern, and the steady coefficient pattern, the coefficient pattern corresponding to the obtained temperature change rate is stored after the abnormality. Select an expression.
Then, as shown in FIG. 5, it is determined whether or not machining control is to be continued (step S25). If machining control is to be continued, the process returns to step S21 and the above processing is repeated, and machining control is not to be continued. End all processing.

  As described above, according to the present embodiment, the estimated temperature Tip of one temperature sensor STi is calculated based on the measured temperatures Tjd and Tkd of the other two temperature sensors STj and STk. Even when an abnormality due to a failure of STi or the like is detected, the position of each drive shaft of the machine tool 1 based on the thermal displacement can be corrected. Therefore, highly accurate machining of the workpiece W can be continued, and deterioration of the machining accuracy and productivity of the workpiece W can be prevented.

(Other)
In the above-described embodiment, the coefficient pattern representing the coefficients α and β used in the temperature estimation formula is a function of the rate of change of the temperature sensor. However, the rate of change of the temperature sensor increases at a certain rate of change γa or more. The constants may be constants αup, βup, αdown, βdown when descending at a constant rate of change γb or more, and constants αc, βc otherwise. Also, constants α and β that do not depend on the rate of change of the temperature sensor may be used.

Moreover, although the temperature of the location which can be measured by one temperature sensor STi is calculated as the estimated temperature based on the measured temperatures of the other two temperature sensors STj and STk, it is based on the measured temperatures of three or more temperature sensors. Thus, the estimated temperature may be calculated.
Further, the machine tool 1 has been described by taking a three-axis machining center as an example. On the other hand, the machine tool 1 may be, for example, a 5-axis machining center having a rotation axis (A, B axis). Even in such a configuration, the same effect can be obtained.

  1: machine tool, 50: numerical control device, 51: sensor signal input unit, 52: abnormality determination unit, 53: estimated temperature calculation unit, 54: calculation method update unit, 55: machining control unit, 56: warning unit, 57 : Storage unit, 61: temperature change rate calculation unit, 62: pattern determination unit, 63: optimization calculation unit, 64: update unit, W: workpiece, STi, STj, STk ...: temperature sensor

Claims (7)

A plurality of temperature sensors each capable of measuring the temperature at a plurality of locations;
A control device for controlling the processing of the workpiece based on the measured temperatures of the plurality of temperature sensors;
With
The controller is
Estimated temperature calculation means for calculating the temperature at a location where one of the temperature sensors can be measured as an estimated temperature based on the measured temperatures of the other plurality of temperature sensors;
A calculation method updating means for updating a calculation method in the estimated temperature calculation means based on the measured temperature of the one temperature sensor and the estimated temperature;
When it is determined that the one temperature sensor is abnormal, the estimated temperature of the one temperature sensor calculated based on the calculation method updated before the determination is replaced with the measured temperature of the one temperature sensor. Machining control means for controlling machining of the workpiece;
A machine tool.   The machine tool according to claim 1, wherein the calculation method update unit updates the calculation method based on a temperature change rate of at least one of a measured temperature and an estimated temperature of the one temperature sensor.   The machine tool according to claim 1, wherein the calculation method update unit updates the calculation method based on a temperature change rate of measured temperatures of the plurality of temperature sensors.   The machine tool according to claim 2 or 3, wherein the calculation method updating means determines a coefficient pattern representing a coefficient of a temperature estimation formula used in the calculation method based on the temperature change rate.   The coefficient pattern is set separately when the temperature change rate rises above a certain change rate, falls below the certain change rate, or transitions below the certain change rate, The machine tool according to claim 4.   The machine tool according to claim 4 or 5, wherein the calculation method updating means optimizes a coefficient of the temperature estimation formula. A machining control method in a machine tool for machining a workpiece based on measured temperatures of a plurality of temperature sensors capable of measuring temperatures at a plurality of locations,
An estimated temperature calculation step of calculating the temperature at a location where one of the temperature sensors can be measured as an estimated temperature based on the measured temperatures of the other plurality of temperature sensors;
A calculation method updating step of updating a calculation method in the estimated temperature calculation means based on the measured temperature of the one temperature sensor and the estimated temperature;
When it is determined that the one temperature sensor is abnormal, the estimated temperature of the one temperature sensor calculated based on the calculation method updated before the determination is replaced with the measured temperature of the one temperature sensor. A machining control process for controlling the machining of the workpiece;
A machining control method in a machine tool, comprising:

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