JPH11338527A - Method and device for controlling machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the positional precision without using a sensor to the utmost by dividing a physical phenomenon which affects the positional precision of a machine tool into elements which are dominant to phenomena of constituent elements and numerically modeling them, and simulating deformation behavior of the machine tool sequentially and performing correction control. SOLUTION: The heat absorption quantity of a main shaft device is calculated by a coolant heat absorption quantity arithmetic part 25a, a lubricating oil heat absorption quantity arithmetic part 25b, and a main-shaft heat radiation quantity arithmetic part 25c, the heating value of the main shaft device 11 is calculated by a main-shaft heating value arithmetic part 27a and a main-shaft driving motor heating value arithmetic part 27b, and a main-shaft temperature arithmetic part 29 integrates them to calculate the temperature of the main shaft. The temperature of the main shaft is outputted to the coolant heat absorption quantity arithmetic part 25a, lubricating oil heat absorption quantity arithmetic part 25b, and main-shaft heat radiation quantity arithmetic part 25c and used for next arithmetic. Further, the temperature of this main shaft is outputted to a main-shaft thermal displacement arithmetic correction part 31 to find the thermal displacement quantity of the main shaft and a correction value which is outputted to an NC device 17 to feed the main shaft in a Z-axial direction so as to cancel the thermal displacement quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a machine tool, and more particularly to a method and an apparatus for controlling a machine tool for performing correction control so as to cancel a position error caused by deformation of a predetermined portion of the machine tool.

[0002]

2. Description of the Related Art In recent years, machine tools have been required to have higher and higher accuracy, while machine tools have been operated at higher speeds in order to increase machining efficiency. It is known that when the speed of a machine tool is increased, a main shaft generates heat mainly in a bearing portion to cause thermal deformation and extend in an axial direction. Conventionally, various control methods or control devices have been proposed in order to eliminate such errors based on the thermal displacement of the spindle.

[0003] First, as a method of controlling a machine tool, operation of a working portion of the machine tool according to a predetermined operation procedure, for example, rotation speed and feed of a spindle, feed of an XY table, on / off of a lubricating oil and coolant supply device. Using various sensors such as a control method, a milit switch, and a position detector, the position and state of the working part of the machine tool are detected,
There is a method of performing feedback control so that they have a predetermined value.

As a method of controlling according to a predetermined operation procedure, there is a control method disclosed in Japanese Patent Application Laid-Open No. 9-70739. In this control method, after the displacement based on the thermal deformation of the spindle is actually measured in advance for each spindle rotation speed using time as a variable, the spindle thermal displacement data is stored as a recording table so as to cancel the displacement of the spindle during processing. The feed of the spindle is corrected.

As feedback control using a sensor, the temperature in the X, Y, and Z directions is detected from the head and column of a spindle disclosed in Japanese Patent Application Laid-Open No. 58-132441 to deal with the thermal displacement of the spindle. There is a thermal displacement compensator that outputs a compensation value to an NC device and controls it.

[0006] Japanese Patent Application Laid-Open No. 7-75937 discloses that
A machine tool using a neural network and a control method thereof are disclosed. The machine tool and the control method of this publication have a learning function using a neural network, but determine the amount of thermal deformation of each part of the machine tool based on temperature information from a temperature sensor, and correct each axis. It can be said that it is a kind of feedback control using the above-mentioned sensor in that it is performed.

[0007]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. Hei 9-70739
According to the control method disclosed in Japanese Patent Application Laid-Open Publication No. H10-260, the spindle thermal displacement can be dynamically corrected with a simple configuration. However, since the spindle temperature also changes according to the temperature of the lubricating oil for the bearing of the spindle, the on / off state of the coolant for cutting, the temperature thereof, and the ambient environmental temperature where the machine tool is installed, it is disclosed in the publication. However, even if the spindle displacement data measured in advance is stored as a table, the behavior of the spindle cannot be reproduced from the spindle rotation speed and time. Furthermore, since the pattern of the change in the spindle rotational speed varies depending on the target cutting process and is complicated, the behavior of each part of the complex machine tool cannot be stored as a storage table.

In the control device or control method disclosed in Japanese Patent Application Laid-Open No. 58-132441 and Japanese Patent Application Laid-Open No. 7-75937, a temperature sensor is required as an indispensable element, which increases the manufacturing cost of a machine tool. Further, depending on the target to be detected, it may be difficult or impossible to mount the sensor, and it is not possible to detect the displacement of every part of the machine tool.

In view of the problems of the prior art, the present invention provides
It is an object of the present invention to provide a control method and apparatus for obtaining a correction value for canceling a position error of a control target due to deformation of a machine tool without using a sensor as much as possible and improving a position accuracy of the machine tool.

A further object of the present invention is to provide a control method and apparatus for outputting a correction value for canceling the thermal displacement of the spindle due to a temperature change of the spindle to improve the positional accuracy of the machine tool.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a control method for correcting a position error of a machine tool, wherein a physical phenomenon that affects the position accuracy of the machine tool is determined for each component element of the machine tool. And numerically model each of them, sequentially simulate the deformation behavior of the machine tool by combining the numerically modeled element units, and obtain a correction value for canceling the position error due to the deformation of the machine tool,
A gist of the present invention is a control method of a machine tool that performs correction control using the obtained correction value.

Further, the present invention relates to a method of controlling a machine tool for correcting a position error caused by thermal deformation of a main shaft of a machine tool, wherein a component around the main shaft of the machine tool, heat generation, heat absorption and heat generated by the operation of the component. A control algorithm for controlling physical phenomena such as deformation and its components is divided into basic element units to form a numerical model, and the element units that act between the numerically modeled element units are input and output. Combine and calculate the amount of heat absorbed and generated around the spindle in relation to each other, determine the spindle temperature or the amount of heat accumulated in the spindle from the heat balance around the spindle, and calculate the heat of the spindle from the determined spindle temperature or spindle heat storage. Simulation for obtaining the amount of displacement is performed sequentially,
A gist is a control method of a machine tool for obtaining a correction value for canceling a position error from the thermal displacement of the spindle obtained by the simulation, and performing correction control using the obtained correction value.

Further, according to the present invention, in a control device for a machine tool for correcting a position error due to thermal deformation of a main shaft of a machine tool, among the components arranged around the main shaft, a heat absorbing source and a heat absorbing source are provided for the main shaft. Heat absorption amount calculating means for calculating the amount of heat absorbed by the heat dissipating element and the heat absorption control element, and calorific value calculation for calculating the amount of heat generated by the heat generating element serving as a heat source with respect to the main shaft among the components arranged around the main shaft. A spindle temperature / spindle heat storage amount calculating means for calculating a spindle temperature or a heat amount accumulated in the spindle from the heat absorption amount and the heat generation amount calculated by the heat absorption amount calculation means and the heat generation amount calculation means; The spindle temperature or the spindle heat storage amount calculated by the spindle heat storage amount calculation means is fed back to the heat absorption amount calculation means to sequentially simulate, thereby obtaining a continuous thermal displacement amount of the spindle, and obtaining the calculated heat. Position quantity, and a correction means to perform correction control by generating a correction value for canceling a position error from comprising a machine tool controller is provided.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a machine tool according to an embodiment of the present invention; The deformation behavior is sequentially simulated with time, and a correction value for canceling the position error of the control target due to the deformation of the machine tool is output to the NC device to control the axis feed.

Components that affect the positional accuracy of the machine tool include, for example, a spindle, a spindle device, a bed, a column,
A work table, a tool, a work itself, and the like can be given. Physical phenomena that transform these components include:
Thermal deformation of the main shaft, thermal deformation of a column or bed of the machine tool, elastic deformation of the machine tool due to load fluctuation, and the like are included. Numerical models are assumed for each of the elements that divide such physical phenomena. For example, considering the thermal deformation of the main shaft, heat generated by rotation of the main shaft, heat generated by the main shaft drive motor, heat absorption by coolant, heat absorption by lubricating oil, and natural heat radiation of the main shaft govern physical phenomena that thermally deform the main shaft as a component. It can be considered as an element unit. By linking the numerically modeled element units, the deformation behavior of the machine tool, for example, the thermal deformation of the spindle, the elastic deformation of the machine tool due to the movement of the load or the cutting load, is sequentially simulated with time. In the case of the elastic displacement of the machine tool, the amounts of deformation of the spindle device, bed, column, work table, tool, and work are obtained, and the relative position error between the tool and the work is sequentially simulated.

Next, a correction value for canceling the position error caused by the deformation of the machine tool is obtained. For example, when the main shaft extends 0.01 mm from the orientation of the main shaft length due to thermal deformation, the correction value is a value that reduces the feed of the main shaft in the Z-axis direction by 0.01 mm. This correction value is output to the NC device of the machine tool to perform machine tool correction control. In the case of elastic deformation of the machine tool, a relative position error between the workpiece and the tool tip position is determined in the X, Y, and Z axis directions, and correction values for canceling the respective position errors are X, Y, and Z. Output about the axis,
Perform correction control.

The first embodiment of the present invention will be described in more detail with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a machine tool provided with a spindle thermal displacement correction control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a spindle thermal displacement correction control device. In the following embodiments, a spindle is assumed as a predetermined portion of a machine tool that affects the positional accuracy of the machine tool, and a spindle temperature change as a phenomenon of deforming the spindle is established by establishing a heat balance model around the spindle. A description will be given as an example of a case in which the position error in the Z-axis direction of a main spindle as a control object due to thermal deformation of the main spindle is corrected by sequentially simulating the deformation behavior of the main spindle with time obtained by analysis.

First, in FIG. 1, a machine tool is provided on a bed 10, an XY table 13 which is provided on the bed 10 so as to be movable in the XY-axis directions, and on which a work (not shown) is mounted. Column (not shown), a spindle device 11 supported on the column movably in the Z-axis direction perpendicular to the XY axis, and the XY table
An X and Y axis feeder 15a for feeding in the axial direction and a Z axis feeder 15b for feeding the spindle device 11 in the Z axis direction are provided as main components.

The main shaft device 11 comprises a main shaft 11c rotatably supported by a housing 11a via a bearing 11b, and a so-called built-in main shaft motor 11d housed in the housing 11a and driving the main shaft 11c to rotate. It is provided as. A tool holder 11f on which a tool 11g is mounted is attached to a tapered hole formed at the tip of the main shaft 11c. A coolant supply passage 11e is formed through the main shaft 11c, the tool holder 11f, and the tool 11g, and coolant is supplied from the coolant supply device 19 toward the cutting edge at the tip of the tool.

The lubricating oil is supplied from the lubricating oil cooling / supplying device 21 to the bearing 11b supporting the main shaft 11c through the lubricating oil supply line 21a and an oil passage (not shown) formed in the housing 11a. The oil is recovered via the oil passage (not shown) and the lubricating oil recovery pipe 21b. A lubricating oil temperature sensor 21c is provided in the lubricating oil collecting line 21b.
Is disposed, and the temperature of the lubricating oil recovered from the spindle device 11 is detected. Further, a mechanical temperature sensor 21d attached to a predetermined portion of the machine tool is connected to the lubricating oil cooling supply device 21. In FIG. 1, for convenience of illustration,
Although the mechanical temperature sensor 21d is attached to the bed 10, the mechanical temperature sensor 21d may be attached to another part of the machine tool where the temperature change is small.

The X / Y-axis feeder 15a and the Z-axis feeder 15b are feeders known to those skilled in the art and include a servomotor for axis feed, an amplifier, and the like as main components. The X / Y axis feed device 15a and the Z axis feed device 15b are controlled by an NC device 17 as an axis feed control device. The spindle drive motor 11d is also the NC device 1.
7 is controlled. Although not shown in detail, N
The C device 17 can be provided with an input device for inputting data relating to the shape and material of the workpiece processed by the machine tool. The NC device 17 is connected to a spindle thermal displacement correction control device 23 described later in detail.

Next, the spindle thermal displacement correction control device 23 according to the embodiment of the present invention will be described with reference to FIG. The main shaft thermal displacement correction control device 23 includes a heat absorption amount calculation unit 25 and a heat generation amount calculation unit 2.
7, a spindle temperature calculating section 29 and a spindle thermal displacement calculating and correcting section 31. Although not shown in detail, the spindle thermal deformation prediction and correction device 23 includes a central processing element (CPU), a storage device such as a ROM and a RAM, an input / output interface, and a bidirectional bus connecting these components as hardware components. Can be configured. The storage device is
It may include a hard disk device, a magneto-optical disk device, or the like.

As will be described later in detail, the spindle thermal displacement correction control device 23 determines the amount of heat absorbed by a component that becomes a heat absorbing source with respect to the main shaft among the components of the machine tool disposed around the main shaft 11c. The heat absorption amount calculation unit 25 calculates the heat generation amount of a component serving as a heat source with respect to the spindle by the heat generation amount calculation unit 27, and the calculated heat absorption and heat amount is integrated in the spindle temperature calculation unit 29, The temperature of the main shaft 11c is calculated from the heat balance, and based on the calculated temperature, the main shaft thermal displacement correction unit 31 calculates the thermal displacement of the main shaft 11c.
In order to offset the thermal displacement, a correction value relating to the feed of the main shaft 11C in the Z-axis direction is output to the NC device 17 to remove the position error due to the thermal displacement of the main shaft 11c, thereby improving the processing accuracy. It is.

The heat absorption amount calculating section 25 is supplied to a coolant heat absorption amount calculating section 25a for calculating the heat absorption based on the cooling of the main shaft by the coolant flowing through the coolant passage 11e formed in the main shaft 11c, and the bearing 11b. A lubricating oil heat absorption amount calculating unit 25b that calculates the amount of heat absorbed by cooling by the lubricating oil, and a spindle heat radiation amount calculating unit 25c that calculates the amount of heat that the spindle device 11 dissipates to the surroundings can be provided.

The calorific value calculating section 27 is based on the main shaft calorific value calculating section 27a for mainly calculating the calorific value of the bearing 11b by the rotation of the main shaft 11c, and the copper loss of the main shaft drive motor 11d for driving the main shaft 11c to rotate. A spindle drive motor calorific value calculator 27b for calculating the calorific value.

In each of the coolant heat absorption amount calculation unit 25a, the lubricating oil heat absorption amount calculation unit 25b, and the spindle heat dissipation amount calculation unit 25c, the heat absorption amount in the spindle device 11 is calculated, and the spindle heat generation amount calculation unit 27a and the spindle drive motor heat generation amount. The calorific value of the spindle device 11 is computed by the computing unit 27b,
This is integrated in the spindle temperature calculating section 29 to calculate the temperature of the spindle 11c by setting up a heat balance. Spindle temperature calculator 29
Then, the temperature of the main shaft 11c calculated by the above is output to each of the coolant heat absorption amount calculation unit 25a, the lubricating oil heat absorption amount calculation unit 25b, and the spindle heat radiation amount calculation unit 25c, and is used as the basis for the next calculation. Further, the temperature of the spindle 11c is output to the spindle thermal displacement calculation / correction unit 31, and the thermal displacement of the spindle 11c is determined based on the temperature of the spindle 11c. The spindle 11c is moved in the Z-axis direction so as to cancel the thermal displacement. The correction value is output to the NC device 17 to send the correction value to the NC device 17.

Hereinafter, a method of calculating the spindle temperature according to this embodiment will be described with reference to FIGS. First, FIG.
, The main spindle temperature prediction and calculation main routine will be described. This main routine can be started, for example, when the main power of the machine tool is turned on. After activation of the main routine, first, an initialization subroutine is called (step S10), and variables are initialized.

Referring to FIG. 4, in the present embodiment,
In the initialization subroutine, in step S23, the ambient temperature _Ta is determined by referring to a previously registered annual temperature table from the date when the main power is turned on (when the power is turned on). That is, the ambient temperature T _a is determined by the date of the function F (date). Next, in step S24, the main power supply is turned off.
The time t during which the main power is off
₀ is calculated, to calculate the heat radiation in the main power OFF from the spindle temperature T _sp during main power OFF stored, spindle temperature when the main power supply ON is determined, and a new spindle temperature T _sp. This is obtained by the following integration.

(Equation 1) Here, C is the specific heat of the main shaft 11c, M is the mass of the main shaft 11c, τ _c is a time constant, and a ₃ and γ _d are constants. Of course previously installed a temperature sensor 33 to determine the ambient temperature T _a, may be used as the initial value of the ambient temperature T _a with the readings of the temperature sensor 33. Note that the temperature sensor 33 is not an essential component.

Further, in step S25, a cool run
Heat absorption Q_c, Lubricating oil heat absorption Q_o, Spindle heat dissipation Q_d, main
Shaft heating Q_sp, Spindle drive motor heating value Q_m0 is read in
I will. Coolant heat absorption Q_c, Lubricating oil heat absorption Q_o, main
Shaft heat dissipation Q_d, Spindle heat value Q _sp, Spindle motor heat generation
Q_mCan be expressed in watts (W), but
The dimension may be made non-dimensional based on the representative value.

Next, at step S12, a spindle temperature calculation subroutine is called. Referring to FIG. 5, in step S26, the spindle temperature T _sp, each of the coolant heat absorption amount Q _c, lubricating oil heat absorption amount Q _o, spindle radiation amount Q _d, spindle calorific value Q _sp, the spindle drive motor calorific value Q _m Is multiplied by constants a _{1 to} a ₅ as weights to obtain a predetermined time constant τ
_The value obtained by multiplying the product by _c and multiplying the reciprocal of the product of the specific heat C of the main shaft 11c by the mass M is added to the previous value of the main shaft temperature _Tsp . Here, the time constant τ _c is determined corresponding to the actual time interval at which the main shaft temperature prediction calculation main routine is executed. The specific heat C of the main shaft 11c can be determined from the material of the main shaft 11c.

[0031] When the spindle temperature computation subroutine first time is performed, the coolant endothermic quantity Q _c, lubricating oil heat absorption amount Q _o, spindle radiation amount Q _d, spindle calorific value Q _sp, the spindle drive motor calorific value Q _m Has been input, the spindle temperature T _sp calculated in step S26 becomes the spindle temperature T _sp calculated in step S24.

After execution of the spindle temperature calculation subroutine, in steps S14 to S22 of the main routine, a coolant heat absorption calculation subroutine, a lubricating oil heat absorption calculation subroutine, a spindle heat dissipation calculation subroutine, a spindle heat generation calculation subroutine, and a motor heat generation calculation Subroutines are executed sequentially.

In FIG. 6, a coolant temperature T _c (γ _c is a constant) obtained as _a function of the ambient temperature Ta and a preset coolant flow rate FR _c are read (steps S28 and S30). Then, the coolant endothermic quantity Q _c is calculated by multiplying the coolant temperature T _c and the spindle temperature T _sp to the difference in the constant alpha _c and the flow rate FR _c of. Here, the constant α _c is
It is a constant corresponding to the heat transfer coefficient of the coolant flowing through the coolant passage 11e of the main shaft 11c.

[0034] In FIG. 7, with the lubricating oil heat absorption amount calculation subroutine, first, numerical modeling the cooling control of the lubricating oil cooling supply device 21, reading of the machine temperature and (temperature sensor 21d is assumed to be equal to the ambient temperature T _a may be used), the difference between the recovered lubricating oil temperature determined by the spindle temperature T _sp (reading of the temperature sensor 21c) is multiplied by the proportional constant k to calculate the lubricating oil temperature T _o (step S32). Then read the lubricating oil flow rate FR _o that is set in advance (step S3
4). Although the temperature sensor 21c is an essential sensor, this temperature sensor is not a temperature sensor provided for controlling the amount of thermal displacement of the main shaft, but is originally provided as a component attached to the lubricating oil cooling supply device 21. Sensor.

[0035] Then, in step S36, the lubricating oil temperature T _o and the spindle temperature T constant on the difference between the _sp alpha _o and flow FR _o
The lubricating oil heat absorption amount Q _o is calculated by multiplying the. Here, the constant α _o is determined by the oil passage in the housing 11a and the main shaft 11c.
Is a constant corresponding to the total heat transfer coefficient of the lubricating oil flowing through the bearing 11b.

[0036] In the spindle heat radiation amount calculation subroutine in FIG. 8, first, the temperature difference between the ambient temperature Ta and the spindle temperature T _sp delta
Seeking T _sp (step S38), then the temperature difference [Delta] T _sp
Is multiplied by a constant γ _d to obtain the heat radiation amount of the main shaft. Constant γ
_d is a value corresponding to a heat transfer coefficient of heat transferred from the main shaft 11c to the outside air through the housing 11a. For example, convection heat transfer from the main shaft 11c to the housing 11a in the housing 11a, heat radiation, the housing 11a , Convection heat transfer from the housing 11a to the outside air, and heat radiation.

Referring to FIG. 9, in the spindle heat generation amount calculation subroutine, first, in step S42, the rotation speed rpm of the spindle 11c is read from the NC device 17 as a variable RPM, and in step S44, the feed shaft servomotor in the NC device 17 is read. deceleration torque from the torque command of the servo control unit of use, frictional torque, the actual cutting load torque t _c obtained by subtracting the vertical axis of gravity holding torque determined and loaded as variables T _c. In step S46, a value P representing the load applied to the bearing 11b is calculated by multiplying the actual cutting load torque _Tc by a constant l.

In step S48, the spindle heat generation amount _Qsp is calculated as a function of the load P and the rotation speed RPM.
In the present embodiment, the heating value _Qsp of the main shaft is mainly the main shaft 1
Considering the heat generated by the bearing 11b that rotationally supports the bearing 1c, the amount of heat generated by the bearing 11b is represented by b of the load P of the bearing 11b.
It is assumed that it is proportional to the sum of the product of the _first power and the rotational speed RPM and the b ₂ power of the rotational speed RPM. Proportional constants γ ₁ , γ ₂
Can be obtained as appropriate by experiments. For example, the rotational speed RPM and the load P are stored as parameters in the storage device of the control device as parameters in relation to the proportional constants γ ₁ , γ ₂ and the indices b ₁ , b _2. Can be.

In FIG. 10, in the motor heating value calculation subroutine, in step S50, the spindle drive motor 1
Drive current i _m which is supplied to 1d is loaded as a variable I _m outputted from the NC device 17. Motor heating value Q
_m is obtained by multiplying the motor loss constant ε to the square of the drive current I _m (step S52). The motor loss constant ε is
It can be stored as a constant of the motor to be used.

When the subroutine for calculating the amount of heat absorbed by the coolant, the subroutine for calculating the amount of heat absorbed by the lubricating oil, the subroutine for calculating the amount of heat released from the spindle, the subroutine for calculating the amount of heat generated by the spindle, and the subroutine for calculating the amount of heat generated by the motor are sequentially executed in steps S14 to S22. , spindle temperature computation subroutine returned to (step S12), the coolant heat absorption amount Q _c obtained as described above, the lubricating oil heat absorption amount Q _o,
Spindle radiation amount Q _d, spindle calorific value Q _sp, new spindle temperature T _sp is obtained based on the spindle drive motor calorific value Q _m. The obtained spindle temperature T _sp is calculated by the coolant heat absorption amount calculation unit 25a,
Returning to the lubricating oil heat absorption amount calculation unit 25b and the spindle heat radiation amount calculation unit 25c and sequentially performing simulation, the spindle 11c
Is continuously determined.

As will be understood by those skilled in the art, according to the above-described method of calculating the spindle temperature, the spindle temperature is continuously calculated from the start to the stop of the machine tool, including during the rotation and the stop of the spindle. It is possible to do.

The spindle temperature T _sp is output to the spindle thermal displacement calculation and correction section 31 as described above. In the spindle thermal displacement calculation correcting section 31, the thermal displacement of the spindle 11c is obtained based on the spindle temperature _Tsp . The actual thermal displacement can be obtained by experiment using the spindle temperature _Tsp as a parameter, and the data can be stored in a storage device as a storage table. Alternatively, it may be represented by a value proportional to a temperature change. The spindle thermal displacement calculation and correction unit 31 outputs a correction value for canceling out the obtained thermal displacement to the NC device 17, and the NC device 17 outputs a command to the Z-axis feed device based on the correction value. As shown in FIG. 2, the feature of this embodiment is that a correction value for canceling the spindle thermal displacement is calculated from the spindle temperature or the spindle heat storage obtained by the simulation, and the obtained spindle temperature or the spindle heat storage is used for coolant absorption. The following simulation is also performed by returning to the calorie computing unit 25a, the lubricating oil heat absorption computing unit 25b, and the spindle heat radiation computing unit 25c to obtain a new spindle temperature or spindle heat storage, and correction is performed by repeating this cycle sequentially. It is raising the eligibility of control.

Although one embodiment of the present invention has been described with reference to the accompanying drawings, it is needless to say that the present invention is not limited to this embodiment but can be variously modified and improved. For example, in the above-described embodiment, the spindle device 11 includes the built-in spindle drive motor 11d, but the present invention is not limited to such a spindle device, and a spindle drive motor is provided outside the housing 11a. It may be.

In the above description, the heat absorption amount calculation unit 25 includes the coolant heat absorption amount calculation unit 25a and the lubricating oil heat absorption amount calculation unit 25.
b and the spindle heat radiation amount calculation unit 25c, but this is merely an example, and the present invention is not limited to this configuration. Even if it is other than coolant, lubricating oil, and natural heat radiation, if there is an element having a heat absorption or cooling effect that affects the thermal displacement of the main shaft 11c, in order to remove the influence on the processing accuracy due to the element, It can be included in the heat absorption amount calculation unit 25. In the present embodiment, the spindle device that supplies the coolant to the processing area by a so-called through spindle type supply method is used as an example.
However, in the case of a spindle device having no coolant passage penetrating through the spindle 11c, it is considered that the cooling effect of the coolant on the spindle 11c is small, so that the heat absorption amount calculating unit 25a may not be provided.

In the above-described embodiment, in the coolant heat absorption amount calculation subroutine, the heat absorption by the coolant is represented by the product of the temperature difference between the spindle and the coolant, the coolant flow rate, and the heat transfer coefficient. It is not limited to this. For example, the temperature difference between the main shaft and the coolant and the coolant flow rate may be used as parameters to determine the heat absorption effect of the coolant in advance by experiment, and the data may be stored in a storage device in the form of a storage table.

Similarly, in the embodiment described above, in the lubricating oil heat absorption amount calculation subroutine, the amount of heat absorbed by the lubricating oil is represented by the product of the temperature difference between the main shaft and the lubricating oil, the flow rate of the lubricating oil, and the heat transfer coefficient. However, the present invention is not limited to this. For example, with the temperature difference between the main shaft and the lubricating oil and the lubricating oil flow rate as parameters, the heat absorption effect of the lubricating oil is obtained by an experiment in advance,
The data may be stored in a storage device in the form of a storage table.

Further, in the above-described embodiment, in the spindle heat radiation amount calculation subroutine, the amount of heat dissipated from the housing of the spindle device is represented by the product of the spindle, the ambient temperature, and the heat transmission rate. It is not limited to. For example, the amount of heat dissipated from the spindle device may be obtained in advance by experiment using the temperature difference between the spindle and the ambient temperature as a parameter, and the data may be stored in a storage device in the form of a storage table.

In the description of the above-described embodiment, the heat generation amount calculation unit 27 includes the spindle heat generation amount calculation unit 27a and the spindle drive motor heat generation amount calculation unit 27b. However, this is merely an example, and It goes without saying that the invention is not limited to this configuration. For example, as described above, the housing 11
In the case where a drive motor for the main shaft 11c is provided outside of “a”, the main shaft drive motor calorific value calculation unit 27b may not be provided. Further, when there is another factor that raises the temperature of the main shaft 11c, the heat generation amount calculation unit 27 can be configured to calculate the heat generation amount.

In the above-described embodiment, in the main spindle heat generation amount calculation subroutine, the heat generation amount in the bearing 11b is
b has been described as a function of the load and the rotation speed, the present invention is not limited to this, for example, the main shaft 11b
The amount of heat generated by the bearing 11b may be obtained in advance by experiment using the rotation speed of the motor as a parameter and stored in the storage device in the form of a storage table.

In the above-described embodiment, the spindle temperature calculator 29
The spindle temperature T _sp was obtained and the heat generation amount of the spindle was obtained based on the spindle temperature T _sp . However, instead of the spindle temperature calculation unit 29, the amount of heat accumulated in the spindle is calculated by an algorithm similar to the algorithm shown in FIG. A spindle heat storage amount calculation unit (not shown) may be used. Then, the amount of thermal deformation of the spindle may be determined based on the spindle heat storage amount calculated by the spindle heat storage amount calculation unit.

Further, in the embodiment described above, the Z of the main shaft 11c is
The case where the correction value is output for the feed control in the axial direction has been described, but the present invention is not limited to this. For example, by setting up a heat balance model for thermal deformation of a column or a bed in a machine tool, and simulating the behavior of the machine tool by numerical analysis, a correction value is output for feed control in the XYZ axis directions. It can also be configured.

Further, physical phenomena affecting the positional accuracy of the machine tool include not only thermal deformation but also deformation of a column or a bed of the machine tool due to movement of a load or movement of a load due to movement of an XY table or work cutting. Outputs correction values for feed control in the X, Y, and Z directions by setting up a dynamic numerical model and simulating the behavior of a machine tool numerically with respect to deformation of a workpiece caused by cutting load. It can also be configured to do so.

Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
The physical phenomena affecting the positional accuracy of the machine tool are described with reference to FIGS. 1 and 12, as the movement of the work table or the movement of the load due to the cutting of the work or the deformation of the column or bed of the machine tool due to the load fluctuation, and the cutting. A description will be given of an example in which a mechanical numerical model is set up and a behavior of a machine tool is simulated numerically by considering deformation of a workpiece due to a processing load.

In FIG. 11, the machine tool 51 is a bed 5
3, a column 55 supported reciprocally in the X-axis direction (a direction perpendicular to the paper surface), and a spindle head 57 supported reciprocally movable in the Y-axis direction (vertical direction) on the column 55.
And a work table 59 supported on the bed 53 so as to be able to reciprocate in the Z-axis direction (direction perpendicular to the XY axes). The work fixture 6 is provided on the upper surface of the work table 59.
The work W is attached to the work W via a spindle 1, and a tool 57 a is attached to the main shaft protruding from the tip of the spindle head 57 so as to face the work W.

Referring to FIG. 12, a mechanical deformation calculation / correction control device 63 corresponding to the spindle thermal displacement correction control device 23 in the first embodiment includes a bed deformation calculation unit 63a.
Table deformation calculator 63b, column deformation calculator 63
c, spindle head deformation calculating section 63d, fixture deformation calculating section 6
3e, work deformation amount calculation unit 63f, tool deformation amount calculation unit 6
3g and spindle / workpiece relative position calculation / correction unit 63h
As a major component.

Data indicating the workpiece material, tool type, machining conditions, and the like are input to the cutting force calculation unit 65 via an input interface (not shown) such as a keyboard. The cutting force calculator 65 calculates the cutting force applied to the work W and the tool 57a for cutting the work W. This data is sent to the machine deformation amount calculation correction control device 63 together with the X, Y, and Z axis position coordinate data from the NC device 67.

The bed deformation calculating section 63a calculates the deformation of the bed 53 from the mass of the work W and the X, Y, and Z axis position coordinate data. In the table deformation amount calculation unit 63b,
The amount of deformation of the work table 59 is calculated from the mass of the work W and the cutting force applied to the work W. The column deformation calculating section 63c calculates the deformation of the column 55 due to the cutting force transmitted to the column 55 via the tool 57a and the spindle head 57. In the spindle head deformation amount calculation unit 63d, the tool 5
The amount of deformation of the spindle head 57 due to the cutting force transmitted to the spindle head 57 via 7a is calculated. Fixture deformation amount calculation unit 63
In e, the amount of deformation of the work fixture 61 due to the cutting force transmitted to the work fixture 61 via the work W is calculated. The work deformation amount calculation unit 63f calculates the deformation amount of the work W due to the cutting force applied to the work W. The tool deformation amount calculation unit 63g calculates the deformation amount of the tool 57a due to the cutting force applied to the tool 57a.

Bed deformation calculator 63a, table deformation calculator 63b, column deformation calculator 63c, spindle head deformation calculator 63d, fixture deformation calculator 63e, work deformation calculator 63f, tool deformation The respective deformation amounts calculated by each of the calculation units 63g are combined and sent to the spindle / work relative position calculation correction unit 63h, where the relative position between the spindle and the work W is calculated, and the relative position between the spindle and the work W is calculated based on the input machining conditions. A correction value for canceling the position error is calculated. The correction value is sent to the NC device 67, and the feeding device 69 is controlled based on the correction value.

As will be understood from the description of the above-described embodiment, the main feature of the present invention is that a machine tool that affects the precision of feed control in the X, Y, and Z axis directions, which is the control target of the machine tool, A numerical analysis model is set up for a phenomenon that deforms a predetermined part of the machine, for example, a thermal deformation phenomenon of the spindle as in the above-described embodiment, or a thermal deformation of a column or a bed in a machine tool, and a deformation of a machine tool due to a load variation. Then, the deformation behavior is sequentially simulated with time, and a correction value for canceling the position error of the control target due to the deformation of the machine tool is output to the NC device to perform the axis feed correction control.

[0060]

According to the present invention, a correction value for offsetting a position error of a control target due to deformation of a machine tool is obtained without using a sensor as much as possible, and correction control is performed, thereby improving the position accuracy of the machine tool. Is done. Further, according to the present invention, the positional accuracy of the machine tool can be improved by obtaining the thermal displacement of the spindle due to the temperature change of the spindle by successive calculation, outputting a correction value for canceling the thermal displacement, and performing the correction control.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a machine tool to which a method for controlling a machine tool according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram of a spindle thermal displacement correction control device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a main routine for calculating a spindle temperature.

FIG. 4 is a flowchart of an initialization subroutine.

FIG. 5 is a flowchart of a spindle temperature calculation subroutine.

FIG. 6 is a flowchart of a coolant heat absorption amount calculation subroutine.

FIG. 7 is a flowchart of a spindle heat radiation amount subroutine.

FIG. 8 is a flowchart of a lubricating oil heat absorption calculation subroutine.

FIG. 9 is a flowchart of a spindle heat generation amount calculation subroutine.

FIG. 10 is a flowchart of a spindle drive motor heat generation amount calculation subroutine.

FIG. 11 is a view showing a configuration of a machine tool to which a method for controlling a machine tool according to a second embodiment of the present invention is applied.

FIG. 12 is a block diagram of a mechanical deformation correction control device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Bed 11 ... Spindle device 11a ... Housing 11b ... Bearing 11c ... Spindle 11d ... Spindle drive motor 13 ... XY table 15a ... Z-axis feeder 15b ... XY-axis feeder 17 ... NC device 19 ... Coolant supply device 21 ... Lubricating oil Cooling and supply unit 23: Spindle thermal displacement correction control unit

Claims (3)

[Claims] 1. A control method for correcting a position error of a machine tool, comprising: dividing a physical phenomenon affecting a position accuracy of the machine tool into element units governing the phenomenon with respect to constituent elements of the machine tool; Combine the numerically modeled element units to sequentially simulate the deformation behavior of the machine tool, obtain a correction value for canceling the position error due to the deformation of the machine tool, and perform correction control using the obtained correction value Machine tool control method. 2. A method of controlling a machine tool for correcting a position error caused by thermal deformation of a main shaft of a machine tool, comprising: a component around the main shaft of the machine tool; and a physics such as heat generation, heat absorption, and thermal deformation generated by the operation of the component. The control algorithm for controlling the phenomena and its components is divided into basic element units to form a numerical model, and the element units that operate between the numerically modeled element units are connected by input and output, and Calculate the amount of heat absorbed and the amount of heat generated around the main spindle in relation to the above, find the spindle temperature or the amount of heat accumulated in the spindle from the heat balance around the spindle, and find the thermal displacement of the spindle from the obtained spindle temperature or the spindle heat storage A machine tool that sequentially performs a simulation, obtains a correction value for canceling a position error from the thermal displacement amount of the spindle obtained by the simulation, and performs correction control using the obtained correction value. Control method. 3. A control device for a machine tool for correcting a position error caused by thermal deformation of a main shaft of a machine tool, wherein, among components arranged around the main shaft, a heat radiation element serving as a heat absorption source for the main shaft and heat absorption control. Heat absorption amount calculating means for calculating an amount of heat absorbed by the element; heat generation amount calculating means for calculating a heat generation amount by a heating element serving as a heat source with respect to the main shaft among constituent elements arranged around the main shaft; A spindle temperature / spindle heat storage amount calculating means for calculating a spindle temperature or a heat amount accumulated in the spindle from the heat absorption amount and the calorific value calculated by the calculating means and the calorific value calculating means; and a spindle temperature / spindle heat storage amount calculating means. The calculated spindle temperature or spindle heat storage amount is fed back to the heat absorption amount calculating means and sequentially simulated to obtain a continuous thermal displacement amount of the spindle, and a position error is calculated from the obtained thermal displacement amount. Control device for a machine tool comprising a correction unit to perform correction control of the correction value for canceling is generated, the.