Displacement correction device and displacement correction method for machine tool

Abstract

To accurately correct an accuracy change of a machine tool and improve machining accuracy even when a floor is deformed due to a temperature change of an installation environment of the machine tool.SOLUTION: A displacement correction device 10 includes: a temperature information acquisition section 11 which acquires temperature information from a temperature sensor 2; a floor information acquisition section 12 which acquires floor information using a temperature sensor 3 for measuring a temperature of a floor F on which a machining center 1 is installed; a displacement amount arithmetic section 13 which inputs the temperature information acquired by the temperature information acquisition section 11 and the floor information acquired by the floor information acquisition section 12 and calculates displacement estimation amount of the machining center 1 from a preset displacement estimation formula; and a correction section 14 which corrects a shaft command value on the basis of the displacement estimation amount calculated by the displacement amount arithmetic section 13.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an apparatus and method for correcting displacement caused by temperature changes in a machine tool.

Background Art

[0002] In a machine tool, thermal displacement occurs in each member of the machine tool due to temperature changes in the installation environment or heat generation in movable parts, reducing machining accuracy. As measures to prevent this, there are a method of estimating and correcting thermal displacement from temperature information of the machine body, or a method of directly measuring and correcting deformation of the machine body. As a prior art of the former, Patent Document 1 discloses a method of installing a temperature sensor on a machine tool main body and correcting the thermal displacement of the spindle from the temperature change obtained from the temperature sensor. Further, as a prior art of the latter, Patent Document 2 discloses a method of installing inclination angle detectors at the upper and lower ends of a column of a machining center, directly measuring the thermal deformation (inclination angle) generated in the column of the machine, and estimating and correcting the displacement of the cutting edge based on the measurement result.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the one hand, thermal deformation due to temperature changes in the installation environment occurs not only in the machine tool but also in the floor on which the machine tool is installed. When the floor deforms, deformation also occurs in the bed and table of the machine tool, and the accuracy of the machine also changes. Therefore, in order to accurately correct the change in machining accuracy caused by temperature changes in the installation environment, it is necessary to take into account the state of the floor. However, in the invention of Patent Document 1, the thermal displacement of the spindle is estimated based on the temperature information measured by the temperature sensor installed in the machine, and the displacement of the cutting edge is corrected. In the invention of Patent Document 2, the thermal displacement of the column is estimated from the difference in inclination measured by the inclination angle detectors installed at the upper and lower parts of the column, and the displacement of the cutting edge is corrected. That is, since these conventional technologies do not consider the influence on the machine tool due to the deformation of the floor, they cannot correct the change in the accuracy of the machine tool due to the deformation of the floor.

[0005] Therefore, an object of the present disclosure is to provide a displacement correction device and a displacement correction method for a machine tool that can accurately correct a change in the accuracy of the machine tool and improve the machining accuracy even when the floor deforms due to a temperature change in the installation environment of the machine tool.

Means for Solving the Problems

[0006] In order to achieve the above object, a first configuration of the present disclosure is a displacement correction device for a machine tool that estimates the displacement of the machine tool based on temperature information from a temperature sensor installed in the machine tool and corrects an axis command value, a temperature information acquisition unit that acquires the temperature information from the temperature sensor; a floor information acquisition unit that acquires floor information using a floor state sensor that measures the state of the surface or inside of the floor on which the machine tool is installed; a displacement amount calculation unit that calculates a displacement estimation amount of the machine tool from a preset displacement estimation formula using the temperature information acquired by the temperature information acquisition unit and the floor information acquired by the floor information acquisition unit as inputs; and a correction unit that corrects the axis command value based on the displacement estimation amount calculated by the displacement amount calculation unit. Another aspect of the first configuration is that, in the above configuration, the floor state sensor measures, as the floor information, any one of the temperature of the floor on which the machine tool is installed, the displacement of the floor, and the inclination of the floor. Another aspect of the first configuration is that, in the above configuration, there is a displacement information acquisition unit that acquires the displacement of the machine tool, an information recording unit that records the floor information, the temperature information, and the displacement information acquired by the displacement information acquisition unit, and a displacement formula calculation unit that calculates a displacement estimation formula using, as inputs, the floor information, the temperature information, and the displacement information recorded by the information recording unit. The displacement amount calculation unit calculates the displacement estimation amount based on the displacement estimation formula calculated by the displacement formula calculation unit. To achieve the above object, a second configuration of the present disclosure is a displacement correction method for a machine tool that estimates the displacement of the machine tool based on temperature information from a temperature sensor installed in the machine tool and corrects the axis command value, a temperature information acquisition step of acquiring the temperature information from the temperature sensor, a floor information acquisition step of acquiring floor information using a floor state sensor that measures the state of the surface or inside of the floor on which the machine tool is installed, a displacement amount calculation step of calculating a displacement estimation amount of the machine tool from a preset displacement estimation formula using, as inputs, the temperature information acquired in the temperature information acquisition step and the floor information acquired in the floor information acquisition step, and a correction step of correcting the axis command value based on the displacement estimation amount calculated in the displacement amount calculation step.

Advantages of the Invention

[0007] According to the present disclosure, even when the floor is deformed due to a temperature change in the installation environment of the machine tool, it is possible to accurately correct the accuracy change of the machine tool and improve the machining accuracy. In addition, since the equipment to be installed is only simple equipment such as a temperature sensor, the installation cost and running cost can be reduced. In particular, according to another aspect of the present disclosure, since the displacement estimation formula is calculated according to the machine tool and the environment in which the machine tool is installed, it is possible to perform correction according to the environment in which the machine tool is installed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [Form 1] FIG. 1 is a configuration diagram showing an example in which the displacement correction device according to the first configuration is applied to a machining center. A temperature sensor 2 is attached to the body of the machining center 1. Further, a temperature sensor 3 is attached to the surface of the floor F on which the machining center 1 is installed. The displacement correction device 10 is provided in the control device of the machining center 1. The displacement correction device 10 includes a temperature information acquisition unit 11, a floor information acquisition unit 12, a displacement amount calculation unit 13, and a correction unit 14. The temperature information acquisition unit 11 is connected to the temperature sensor 2 and acquires the temperature information measured by the temperature sensor 2 (temperature information acquisition step). The floor information acquisition unit 12 is connected to the temperature sensor 3 and acquires the temperature information measured by the temperature sensor 3 (floor information acquisition step). Instead of the temperature sensor 3, a sensor that can quantitatively measure the state of the floor F, such as a displacement meter or an inclinometer, may be used.

[0010] The displacement amount calculation unit 13 takes the temperature information sent from the temperature information acquisition unit 11 and the floor information acquisition unit 12 as inputs, calculates a displacement estimation amount based on a predetermined displacement estimation formula, and outputs the calculated displacement estimation amount to the correction unit 14 (displacement amount calculation step). The displacement estimation formula is set for each axis. In the case of a three-axis machining center, the displacement estimation formulas for the X-axis, Y-axis, and Z-axis are set respectively. In the correction unit 14, a displacement correction amount for correcting the axis command value is calculated based on the input displacement estimated value, and correction is executed by performing axis movement according to the displacement correction amount (correction step).

[0011] Next, the method for calculating the displacement estimated value in the displacement amount calculation unit 13 will be described. The displacement estimation formula for calculating the accuracy change of the cutting edge of the machining center 1 is expressed as the following formula (1).

[0012]

Equation

[0013] The cutting edge accuracy change ΔZ in formula (1) is the sum of the function f for estimating the displacement of the machine body at the temperature T of the floor F f and the function g for estimating the displacement of the machine body at the temperature T m of the machine body. Note that the information obtained from the temperature sensor 3 is not limited to the temperature information of the floor F as used in formula (1). For example, information that can be directly measured and indirectly estimated and quantified for the deformation of the floor F, such as the inclination of the floor F by an inclinometer or the displacement of the floor F by a displacement meter, may be used. The function f regarding the displacement of the machine due to the temperature change of the floor F and the function g regarding the displacement of the machine due to the temperature change of the machine are each expressed by a first-order lag system formula as shown in the following formulas (2) and (3).

[0014]

Equation

[0015] The displacement correction device 10 of the above-described embodiment 1 includes a temperature information acquisition unit 11 that acquires temperature information from the temperature sensor 2, a floor information acquisition unit 12 that acquires floor information using a temperature sensor 3 (an example of a floor state sensor) that measures the temperature of the floor F on which the machining center 1 is installed, a displacement amount calculation unit 13 that calculates the estimated displacement amount of the machining center 1 from a preset displacement estimation formula using the temperature information acquired by the temperature information acquisition unit 11 and the floor information acquired by the floor information acquisition unit 12 as inputs, and a correction unit 14 that corrects the axis command value based on the estimated displacement amount calculated by the displacement amount calculation unit 13. According to this configuration, even when the floor F is deformed due to a temperature change in the installation environment of the machining center 1, the change in the accuracy of the machining center 1 can be accurately corrected, and the machining accuracy can be improved. In addition, since the devices to be installed are only simple temperature sensors 2 and 3, the installation cost and running cost can be reduced.

[0016] [Embodiment 2] FIG. 2 is a configuration diagram showing another form of the displacement correction device. The same components as those in FIG. 1 are denoted by the same reference numerals, and redundant descriptions are omitted. This displacement correction device 10A is different from Embodiment 1 in that it includes an information recording unit 15, a displacement information acquisition unit 16, and a displacement formula calculation unit 17, respectively. The temperature information measured by the temperature sensor 2 and the temperature sensor 3 is sent to the displacement amount calculation unit 13 in the same manner as in the above-described Embodiment 1. At the same time, the temperature information is associated with the time information and recorded in the information recording unit 15. Further, displacement change information measured by in-machine measuring equipment (not shown) is measured by the displacement information acquisition unit 16 and associated with the time information and recorded in the information recording unit 15. The various information recorded in the information recording unit 15 is output to the displacement formula calculation unit 17. Based on the output information, the displacement formula calculation unit 17 calculates a displacement estimation formula and outputs it to the displacement amount calculation unit 13. The displacement change information measured by the displacement information acquisition unit 16 is information that quantifies the accuracy change of the machine. For example, it is the measurement information when measuring the tool length with a touch sensor using a reference tool. Also, information obtained outside the machining center 1 such as the measurement result of the workpiece dimensions when machining the workpiece may be used.

[0017] The displacement estimation formula can calculate a displacement estimation formula with improved displacement estimation accuracy by using the past temperature information recorded in the information recording unit 15 and the measurement information by the measuring instrument. For example, from the difference between the measurement information of the accuracy change measured using the in-machine measuring instrument and the estimated displacement amount by the displacement estimation formula at that time, α or β that minimizes the value of the following formula (4) is determined using the least squares method. Thereby, a displacement estimation formula based on the actual accuracy change can be calculated.

[0018]

Number

[0019] For calculating the displacement estimation formula, methods other than the least squares method shown in the embodiment may be used. For example, there are a method using a genetic algorithm with the displacement estimation coefficient and the time constant as inputs, and a method of determining α or β using a neural network with the temperature information and the measurement data of the displacement as inputs and calculating the displacement estimation formula.

[0020] Also in the displacement correction device 10A of the above-described form 2, by including the temperature information acquisition unit 11, the floor information acquisition unit 12, the displacement amount calculation unit 13, and the correction unit 14, even when deformation occurs in the floor F due to a temperature change in the installation environment of the machining center 1, the accuracy change of the machining center 1 can be accurately corrected and the machining accuracy can be improved. In particular, here, there are a displacement information acquisition unit 16 that acquires the displacement of the machining center 1, floor information, temperature information, and an information recording unit 15 that records the floor information, temperature information, and displacement information acquired by the displacement information acquisition unit 16, and a displacement formula calculation unit 17 that calculates a displacement estimation formula using the floor information, temperature information, and displacement information recorded by the information recording unit 15 as inputs. The displacement amount calculation unit 13 calculates a displacement estimation amount based on the displacement estimation formula calculated by the displacement formula calculation unit 17. In this way, by calculating the displacement estimation formula according to the environment in which the machining center 1 is installed, it is possible to perform correction according to the environment in which the machining center 1 is installed.

[0021] In the above-described Forms 1 and 2, the displacement correction device is provided in the control device, but the displacement correction device may be provided separately from the control device. In the above-described Forms 1 and 2, the temperature of the floor obtained from the temperature sensor is acquired as the floor information, but as described above, either the displacement of the floor or the inclination of the floor may be used as the floor information. Also, a plurality of the floor temperature, floor displacement, and floor inclination may be used as the floor information. In the above-described Forms 1 and 2, the machining center is described as an example of the machine tool, but the present disclosure is not limited to the machining center and is applicable to other machine tools in general.

Explanation of Reference Numerals

[0022] 1... Machining center, 2, 3... Temperature sensors, 10, 10A... Displacement correction devices, 11... Temperature information acquisition unit, 12... Floor information acquisition unit, 13... Displacement amount calculation unit, 14... Correction unit, 15... Information recording unit, 16... Displacement information acquisition unit, 17... Displacement formula calculation unit, F... Floor.

Claims

1. A displacement correction device for a machine tool that estimates the displacement of the machine tool based on temperature information from a temperature sensor installed in the machine tool and corrects the axis command value, comprising: a temperature information acquisition unit that acquires the temperature information from the temperature sensor; a floor information acquisition unit that acquires floor information using a floor condition sensor that measures the state of the surface or inside of the floor on which the machine tool is installed; a displacement amount calculation unit that calculates the estimated displacement amount of the machine tool from a preset displacement estimation formula using the temperature information acquired by the temperature information acquisition unit and the floor information acquired by the floor information acquisition unit as inputs; a correction unit that corrects the axis command value based on the estimated displacement amount calculated by the displacement amount calculation unit; A displacement correction device for a machine tool, characterized by comprising the above.

2. The displacement correction device for a machine tool according to claim 1, wherein the floor condition sensor measures any one of the temperature of the floor on which the machine tool is installed, the displacement of the floor, and the inclination of the floor as the floor information.

3. a displacement information acquisition unit that acquires the displacement of the machine tool; an information recording unit that records the floor information, the temperature information, and the displacement information acquired by the displacement information acquisition unit; a displacement formula calculation unit that calculates a displacement estimation formula using the floor information, the temperature information, and the displacement information recorded by the information recording unit as inputs, and The displacement amount calculation unit calculates the estimated displacement amount based on the displacement estimation formula calculated by the displacement formula calculation unit. The displacement correction device for a machine tool according to claim 1 or 2, characterized by this.

4. A displacement correction method for a machine tool that estimates the displacement of the machine tool based on temperature information from a temperature sensor installed in the machine tool and corrects the axis command value, comprising: a temperature information acquisition step of acquiring the temperature information from the temperature sensor; a floor information acquisition step of acquiring floor information using a floor condition sensor that measures the state of the surface or inside of the floor on which the machine tool is installed; a displacement amount calculation step of calculating the estimated displacement amount of the machine tool from a preset displacement estimation formula using the temperature information acquired in the temperature information acquisition step and the floor information acquired in the floor information acquisition step as inputs; a correction step of correcting the axis command value based on the estimated displacement amount calculated in the displacement amount calculation step; A displacement correction method for a machine tool, characterized by executing the above.

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