JP4972925B2 - Temperature measurement position determination method for machine tool and temperature measurement position determination program for machine tool - Google Patents

Description

The present invention, thermal displacement in the machine tool having a function of correcting the optimum temperature Temperature measuring location method及beauty Engineering work of a machine tool for determining the measurement position on the basis of the temperature measurements of the plurality of locations of the machine body The present invention relates to a temperature measurement position determination program for a machine.

  For example, the body of a machine tool (machining center) that performs machining such as drilling and cutting on a workpiece made of a metal material is a base, a table provided on the front side of the base, and supporting the workpiece, and upward on the rear side of the base A column that extends in the direction of movement in the X (left and right) and Y (front and back) directions by an XY movement mechanism, and a spindle on which a tool is mounted on the front side of the column so as to be moved in the Z (up and down) direction The spindle head etc. which have are comprised. Some machine tool bodies of this type are provided with a cutting water circulation mechanism in order to cool the tool portion and wash away cutting waste generated during processing. The control device attached to the machine main body automatically controls the machining by controlling the X-axis and Y-axis servo motors, the Z-axis servo motors, and the main shaft motors of the XY moving mechanism based on the machining data. It has become.

  By the way, in the machine tool as described above, deformation due to thermal expansion occurs in various parts of the machine body due to various heat generation environments such as a temperature rise due to heat generation of the motor and a temperature rise of the cutting water. ) And the table (work) may change, which may cause machining errors. Therefore, in order to prevent such problems, conventionally, the following four countermeasures (a) to (d) have been mainly considered.

(A) A method of blocking heat transfer by providing a heat insulating structure such as a heat insulating cover (b) A method of preventing thermal deformation by forcibly cooling using a refrigerant (c) Directly changing the amount of thermal displacement A method of measuring and adding the correction (d) A method of estimating the amount of thermal displacement and adding the correction

  However, in the configuration in which the heat insulation structure (a) is provided, there is a problem that it is difficult to avoid thermal expansion of each part due to an increase in the ambient temperature, so that a significant effect cannot be obtained and the configuration is complicated. Further, the method of forced cooling (b) has a problem that it is too costly. Furthermore, in the method of directly measuring the amount of thermal displacement in (c), the configuration is complicated and expensive, and there is a problem that sufficient accuracy cannot be obtained.

As a method of estimating and correcting the thermal displacement amount of (d), as shown in Patent Document 1, a temperature sensor is provided at a key point of the machine tool, and the thermal displacement amount is estimated based on the detection of the temperature sensor. In some cases, the movement amount (main shaft position) of each axis is corrected so as to cancel the thermal displacement. In this method, a temperature sensor such as a thermocouple for detecting a reference temperature is provided at a portion where the temperature change is relatively small, a temperature sensor for detecting a casting temperature is provided at a portion where the temperature change is relatively large, and the temperature of the upper part of the machine is further increased. A temperature sensor for detecting the above is provided. Then, the temperature is detected by each temperature sensor at predetermined time intervals, and for each of the casting temperature and the air temperature, the temperature difference from the reference temperature of the temperature detected last time (n-1 time), the reference temperature detected this time (n time). The amount of correction for each axis is obtained by calculation using these values and the thermal time constant and thermal displacement coefficient obtained in advance through experiments.
JP 2003-94290 A

  However, in the technique disclosed in Patent Document 1, the temperature is detected at each of a part having a relatively small temperature change and a part having a relatively large temperature change. It is difficult to estimate how much thermal displacement is occurring in which axial direction with respect to each constituent part only by detecting the temperature at three locations. Therefore, in the prior art disclosed in Patent Document 1, it is difficult to estimate an accurate amount of thermal displacement, and it is still insufficient to improve machining accuracy by correction.

  Therefore, the present applicant provides temperature sensors at a plurality of temperature measurement locations (for example, 9 locations) of the machine body, and determines the amount of thermal displacement (and thus the processing point) of each part according to a predetermined relational expression from the temperature change measured by each temperature sensor. The thermal displacement correction method that calculates and corrects (displacement amount) in Japanese Patent Application No. 2005-99684 and Japanese Patent Application No. 2005-99685 has been filed earlier. The above-mentioned predetermined relational expression is such that the displacement amount δ at the machining point is a function {δ = f (X1) with the amount of temperature change (X1 to Xn) from the reference temperature at n (for example, nine) temperature measurement points as variables. , X2,... Xn)} and is theoretically required. According to this method, the amount of displacement at the machining point can be accurately estimated, and the machining accuracy can be sufficiently increased.

  However, the problem here is that the determination method has not been established as to where the temperature measurement position (position where the temperature sensor is provided) should be set. For example, even if one temperature measurement position is set for a column, the temperature changes at the top and bottom of the column. Incompatible cases will occur. Further, depending on a certain model, even if an appropriate temperature measurement position is obtained, in the case of a model having a different form, the position cannot be applied as it is.

  In this case, it is conceivable to experimentally obtain the temperature measurement position that fits the relational expression using, for example, an actual machine, but candidates for the temperature measurement position for each of a plurality of parts of the machine tool body. If a plurality of points are provided, the number of combinations becomes enormous, and many experiments must be repeated accordingly, which takes a lot of time and is very inefficient and unrealistic. . Further, the experiment itself cannot be performed at the design stage of the machine tool.

The present invention has been made in view of the above circumstances, and its purpose is correction in a machine tool having a function of estimating and correcting the amount of thermal displacement at a processing point based on temperature measurements at a plurality of locations on the machine body. The present invention provides a machine tool temperature measurement position determination method and a machine tool temperature measurement position determination program capable of easily obtaining an optimum temperature measurement position conforming to a predetermined relational expression used in the above .

  In order to achieve the above object, a temperature measurement position determining method for a machine tool according to the present invention estimates and corrects a thermal displacement amount at a machining point by a predetermined relational expression based on temperature measurements at a plurality of locations on the machine body. This is a method for determining the position where temperature measurement should be performed on a machine tool equipped with a function. The machine body is divided into multiple temperature measurement blocks, and multiple temperature measurement candidate points are set for each block. A candidate point setting step to perform, a data acquisition step for obtaining data of temperature change of each candidate point and displacement amount of the processing point for each time series accompanying a thermal state change of the machine body assumed at the time of machining, From the data of temperature change of candidate point and displacement amount of machining point, using genetic algorithm, select one measurement position for each block and set the corresponding bit as 1 And an optimum position calculating step for obtaining a temperature measurement position that is a candidate point of the temperature measurement with a small difference between the temperature change of each candidate point and the displacement amount data of the machining point, one for each block. (1) (Invention of claim 1).

The machine tool temperature measurement position determination program of the present invention is a machine tool having a function of estimating and correcting a thermal displacement amount at a machining point by a predetermined relational expression based on temperature measurement at a plurality of locations of the machine body. In order to determine the position where temperature measurement is to be performed, the computer main body is divided into a plurality of temperature measurement blocks, and a candidate point setting step for setting a plurality of temperature measurement candidate points for each block; A data acquisition step for obtaining temperature change and displacement data at each candidate point for each time series in accordance with a thermal state change of the machine body assumed in FIG. Using a genetic algorithm, one measurement position is selected for each block from the displacement data, and the individual configured with the corresponding bit as 1 is evaluated. And an optimum position calculating step for obtaining a temperature measurement position which is a candidate point of the temperature measurement with a small difference between the temperature change of each candidate point and the displacement amount data of the machining point, one for each block. It is characterized in that it is executed (the invention of claim 6 ).

  According to the above configuration, in the candidate point setting step (step), the machine body is divided into a plurality of temperature measurement blocks for each part where temperature measurement is desired, and a plurality of temperature measurement candidate points for each block. Is set. In the next data acquisition step (step), data of temperature change of each candidate point and displacement amount of the machining point for each time series accompanying the thermal state change of the machine body assumed at the time of machining is obtained. Then, in the optimum position calculating step (step), the optimum temperature measurement position satisfying a predetermined relational expression, one for each block, is obtained from the data using a genetic algorithm.

  Here, the genetic algorithm is to select only the more excellent individuals by performing natural selection and reproductive activity from the initial population, imitating the evolution process of living organisms, and the optimal solution is randomly and promptly selected. It is a technique to search for. In the present invention, using such a genetic algorithm, one optimal combination of temperature measurement positions satisfying a predetermined relational expression can be efficiently obtained for each block.

  At this time, the data acquisition step can be configured to be executed by analysis using a computer (invention of claim 2). Accordingly, necessary data can be obtained at the design stage, and an optimum temperature measurement position can be obtained. Alternatively, the data acquisition step can be executed by an experiment using an actual machine (the invention of claim 3), whereby highly reliable data can be obtained.

  Here, more specifically, as the machine body, a column having a spindle head having a table and a tool supporting the workpiece on the base is provided at the front and back, and a cutting fluid is provided on the upper surface of the base. Is configured to flow. In this case, the temperature of the upper surface portion of the base through which the cutting water having a high temperature flows increases more rapidly than the lower surface portion, and the degree of temperature change is different between before and after the base. Therefore, in the case of such a machine main body, it is preferable to set a total of four temperature measurement blocks on the upper surface side and the lower surface side, respectively, on the upper and lower sides of the base (invention of claim 4). Accordingly, it is possible to more precisely detect the temperature change degree of each component part of the machine main body, and it is possible to obtain and correct the thermal displacement amount at the processing point with sufficient certainty.

  Further, at this time, there is a circumstance in which the warp of the base due to the difference in the degree of temperature change occurs to a level that cannot be ignored as the amount of thermal displacement. In addition to the thermal expansion / contraction of each part of the machine body, the predetermined relational expression may take into account the warpage caused by the difference in temperature rise between the front and back portions of the upper surface side and the lower surface side of the base. (Invention of claim 5) According to this, it becomes possible to obtain and correct the thermal displacement amount of the machining point with sufficient certainty including the warp of the base, and as a result, the machining accuracy can be sufficiently increased.

According to the temperature measurement position determination method for a machine tool and the temperature measurement position determination program for a machine tool according to the present invention, a function for estimating and correcting a thermal displacement amount at a processing point based on temperature measurement at a plurality of locations on the machine body. In the machine tool provided, an excellent effect is obtained in that an optimum temperature measurement position that conforms to a predetermined relational expression used for correction can be easily obtained .

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, a machine tool according to the present embodiment will be described with reference to FIGS. The machine tool according to this embodiment includes a machine tool main body (machining center) 1 and a control device 15 (see FIG. 2) described later. FIG. 1 schematically shows an external configuration of a main body 1 of a machine tool. In this embodiment, the left-right direction of the main body 1 is the X-axis direction, the front-rear direction is the Y-axis direction, and the vertical direction is the Z-axis direction. Control of each axis is performed based on a three-dimensional (XYZ) coordinate system unique to the apparatus.

  As shown in FIGS. 4 and 5, the machine tool body 1 includes a base 2 installed on a floor of a factory, for example, as a component, and a workpiece W provided on the front side of the base 2 (see FIG. 4). ), A column 4 provided on the rear side of the base 2 and extending upward, and a spindle head 5 provided on the front side of the column 4. The column 4 is provided to the base 2 via a well-known XY moving mechanism 6, and both the left and right (X) are driven by driving an X-axis motor 7 and a Y-axis motor 8 (illustrated only in FIG. 2) that are servo motors. (Axis) and forward / backward (Y-axis) direction.

  The spindle head 5 is provided on the column 4 so as to be movable up and down. In the column 4, a Z-axis motor comprising a servo motor for freely moving the spindle head 5 in the vertical (Z-axis) direction. 9 (shown only in FIG. 2) and a vertically moving mechanism including a well-known ball screw mechanism (not shown) and the like are provided. The spindle head 5 is provided with a downward spindle 10 and a spindle motor 11 (illustrated only in FIG. 2), which is a servo motor for rotating the spindle 10. A tool 12 such as a drill or a tap is attached to the tip (lower end) of the main shaft 10 in a replaceable manner. Although not shown, the column 4 is also provided with a tool changer for automatically changing the tool 12.

  The base 2 is made of, for example, cast iron (casting), and the upper surface of the intermediate portion in the left-right direction is configured to be inclined downward toward the rear. A jig (not shown) for supporting the workpiece W is set on the table 3. At the time of processing, the workpiece W is arranged on the rear side on the table 3. Further, although not shown, the main body 1 of the machine tool is surrounded by a splash cover.

  Although not shown in detail, the main body 1 is provided with a cutting water circulation mechanism for cooling the tool 12 (processing point P) and for washing away the cutting waste generated during the processing. This cutting water circulation mechanism has a tank in which cutting water as cutting fluid is stored, a cutting water circulation pump 14 (shown only in FIG. 2), piping, valves, and the like. It is configured to circulate in such a manner that the cutting water is discharged toward the surface, and the cutting water is made to flow through the upper surface portion of the base 2 and returned to the tank, and the cutting waste is captured in the tank portion.

  Then, as shown in FIG. 2, a control device (NC device) 15 for controlling the main body 1 is attached to (or provided integrally with) the main body 1 of the machine tool. Yes. The control device 15 is mainly composed of a microcomputer and includes a storage device 16. The storage device 16 stores an overall control program including a thermal displacement correction program, which will be described later, and also stores various data including machining data (NC program), reference temperature data, which will be described later. It has come to be.

  The control device 15 controls the X-axis motor 7, the Y-axis motor 8, the Z-axis motor 9, and the main shaft motor 11 through a drive circuit (servo amplifier) (not shown), and at the same time, a tool changer and a cutting device. The water circulation mechanism (the cutting water circulation pump 14) is also controlled. In addition, an operation signal from the operation panel 17 is input to the control device 15.

  Thus, the control device 15 attaches a necessary tool 12 to the spindle 10 based on machining data (NC program) inputted in advance, and moves the workpiece W supported on the table 3 by the XY moving mechanism 6. The column 4 is positioned freely in the horizontal direction (X-axis and Y-axis directions), and while the spindle head 5 is moved up and down in the Z-axis direction, the tool 12 (spindle 10) is rotated to rotate the workpiece W at a predetermined position (machining). By acting on the point P), machining operations such as drilling and cutting of the workpiece W are automatically executed. At this time, the control device 15 controls the cutting water circulation mechanism (cutting water circulation pump 14) to cool the tool 12 (processing point P) portion, and to remove cutting waste generated during processing from the table 3 and the base 2 as well. It is designed to wash away from the top surface.

  Now, the control device 15 performs processing due to thermal displacement such as thermal expansion of each component of the main body 1 when performing the above-described processing operation by its software configuration (execution of thermal displacement correction program). The amount of displacement (the amount of deviation from the original machining point) at the point P is estimated, and the amount of movement (X-axis) of each axis (X-axis motor 7, Y-axis motor 8, Z-axis motor 9) so as to cancel the displacement. The target positions of the motor 7, the Y-axis motor 8, and the Z-axis motor 9) are corrected.

  For this thermal displacement correction, in the present embodiment, a total of seven temperature sensors 18 to 18 are provided at a plurality of (for example, seven) temperature measurement positions having different degrees of temperature change with respect to the respective components constituting the main body 1. 24 is provided. Temperature measurement signals from these temperature sensors 18 to 24 are input to the control device 15. At this time, as will be described in detail later, the temperature measurement positions (temperature sensors 18 to 24) are determined by the temperature measurement position determination method (temperature measurement position determination program) according to the present embodiment.

  Specifically, as shown in FIG. 1, the base 2 includes a temperature sensor 18 for measuring the temperature (TB-UF) of the upper surface of the front side (table 3 side) of the base 2, and the temperature of the bottom surface of the front side (TB-UF). A temperature sensor 19 for measuring TB-BF), a temperature sensor 20 for measuring the temperature (TB-UR) of the upper surface of the rear side (column 4 side), and a temperature sensor for measuring the temperature of the bottom surface of the rear side (TB-BR). 21 is provided. The column 4 is provided with a temperature sensor 22 for measuring the temperature (TC) of the column 4. The spindle head 5 is provided with a temperature sensor 23 for measuring the temperature (TSP) of the spindle head 5. The table 3 is provided with a temperature sensor 24 for measuring the temperature (T T) of the table 3.

  As will be described in detail later, the control device 15 stores the initial temperature measured by the temperature sensors 18 to 24 at the same time in the storage device 16 as a reference temperature (T0). At this time, in this embodiment, for example, a value measured at the completion of setting of the jig with respect to the machine tool main body 1 before the start of the machining operation is set as the reference temperature (T0). The reference temperature may be measured when the machine tool is turned on.

  Then, the control device 15 takes in the current measured temperatures (T) of the temperature sensors 18 to 24 at an arbitrary time point (the time point when the correction command signal is present in the machining data (NC program)), and takes each measured temperature ( T) is compared with each reference temperature (T0) to obtain a temperature change (ΔT) at each temperature measurement location, and based on the temperature change (ΔT), each component (base 2, table 3, column 4, The thermal displacement amount of the spindle head 5) is obtained and converted into the displacement amount in each axial direction at the machining point P, and the movement amount of each axis (position of the spindle 10) is corrected according to the converted displacement amount. It is like that. Therefore, the control device 15 functions as a displacement amount detection unit and a correction unit.

  Further, at this time, the control device 15 determines the thermal displacement amount of each constituent part by the thermal expansion / shrinkage of each constituent part and, particularly, the warp caused by the difference in temperature rise between the upper and lower surfaces of the base 2. The amount of thermal displacement of the machining point P (spindle 10) is calculated by a predetermined relational expression described later. Specifically, the displacement amount due to the longitudinal extension of the base 2, the tilt displacement amount due to the warp in the longitudinal direction of the base 2, and the displacement amount due to the longitudinal extension of the column 4, the spindle head 5 and the table 3 are respectively obtained. Thus, the thermal displacement amount of the machining point P (main shaft 10) in each axial direction, particularly in the Y-axis direction, at the machining point P is estimated from the sum of them.

  Here, the phenomenon of displacement due to heat of the main body 1 of the machine tool will be described. In the machine tool main body 1, various heat generations such as heat generation of the motors 7, 8, 9, and 11, frictional heat of the drive mechanism portion, and heat generation due to friction between the tool 12 and the workpiece W as the machining operation is performed. Depending on the environment, thermal expansion of each component occurs. At the same time, there is a circumstance that the cutting water becomes very hot, and the thermal expansion due to the temperature rise of the upper surface portion of the base 2 through which the cutting water flows increases. Such a thermal displacement of each component part causes a machining error at the machining point P, and in order to prevent this, the control device 15 determines the thermal displacement amount δ at the machining point P as described later. The movement amount (position of the main shaft 10) of each axis (here, particularly in the Y-axis direction) is corrected so as to cancel the displacement.

  In this case, thermal displacement occurs in the three axial directions of the X axis, Y axis, and Z axis. Of the thermal displacement in the X axis direction, the thermal expansion of each part is symmetrical with respect to the machining point P. Therefore, the processing point P has almost no influence on the processing accuracy. Regarding the thermal displacement in the Z-axis direction, the thermal expansion and contraction of the ball screw shaft due to the frictional heat of the ball screw mechanism for moving the spindle head 5 up and down is the largest. However, a thermal displacement correction method for correcting the thermal displacement in the Z-axis direction due to the thermal expansion and contraction of the ball screw is well known in an earlier application (for example, Japanese Patent Application Laid-Open No. 2000-135653) by the present applicant. Therefore, detailed description is omitted here.

  Therefore, in this embodiment, the thermal displacement in the Y-axis direction in which the thermal displacement of each component part is the most problematic will be described. FIG. 4 shows exaggeratedly how the components of the machine tool body 1 are thermally displaced. In FIG. 4, the letter “high” in the circle indicates a surface with a large temperature change, and the letter “low” in a circle indicates a surface with a relatively small temperature change on the opposite side. Show. Here, the direction in which the distance between the main shaft 10 and the table 3 is widened (the rear side for the main shaft 10 and the front side for the table 3) is the positive (+) direction, and the opposite direction is the negative (−) direction. explain.

  FIG. 4A shows how the base 2 extends in the Y-axis direction due to thermal expansion. This expansion displacement occurs in a direction in which both the front side (table 3 side) and the rear side (column 4 side) are separated from each other in the front-rear direction center Ob of the base 2. FIG. 4B shows a state of warping deformation of the base 2. In this case, since the thermal expansion of the upper surface side of the base 2 having a large temperature change is larger than that of the bottom surface side, the center side swells upward on the upper surface side of the base 2 (as a result, the table 3 and the spindle 10 are inclined). Such warpage deformation occurs.

  FIG. 4C shows how the column 4, the spindle head 5, and the table 3 extend in the Y-axis direction due to thermal expansion. The expansion displacement of the column 4 and the spindle head 5 occurs so that the spindle 10 is displaced forward, and the rear end side of the table 3 (work W arrangement side) is displaced rearward. The displacement due to the warp of the column 4, the spindle head 5 and the table 3 is extremely small and can be ignored.

The thermal displacement amount δ in the Y-axis direction at the processing point P (main shaft 10) is the sum of the displacement amounts in the Y-axis direction of the respective constituent parts, and can be obtained by the following equation.
Displacement amount δ = Σ (Elongation of each part + Inclination displacement due to warpage)
= (Base 2 table 3 side expansion displacement + column 4 side expansion displacement)
+ (Table 3 side tilt Y-axis conversion displacement of the base 2 + Column 4 side tilt Y-axis conversion displacement)
-(Expansion displacement of column 4 + expansion displacement of spindle head 5 + expansion displacement of table 3)
Therefore, the displacement amount δ can be calculated by obtaining (estimating) each term of the above equation. Each term is calculated by using a temperature change from the reference temperature at each temperature measurement location, a constant (partially variable) such as a linear expansion coefficient and dimensions of each part, and a parameter (correction coefficient) obtained in advance through experiments or the like. It becomes possible.

  In this case, the expansion displacement can be obtained from the difference ΔT between the measured temperature (T) at each temperature measurement location and the reference temperature (T0) at that location, and the linear expansion coefficient λ. Further, the Y-axis direction displacement of the inclination can be obtained from the sine of the inclination angle θ, and the inclination can be obtained from the difference between the expansion displacement on the side with the larger temperature change and the side with the smaller temperature change. A specific calculation example will be described below with reference to FIGS.

  FIG. 5 shows the dimensions of each part of the machine tool main body 1 used for this calculation. The total length of the base 2 in the Y-axis direction is L, the length from the Y-axis direction center Ob of the base 2 to the Y-axis direction center Ot of the table 3 is S-table, and the Y-axis direction of the base 2 is Y-axis of the column 4 The length to the direction center Oc is S-column. The height dimension of the front end of the base 2 is H-base-F, and the height dimension of the rear end is H-base-R. The height of the table 3 is H-table, and the height of the workpiece W (height from the upper surface of the table 3 to the processing point P) is H-work (a variable value).

  The height of the column 4 (including the XY moving mechanism 6) to the upper surface of the table 3 is H-column3, the height from the upper surface of the table 3 to the lower end of the main body of the column 4 is H-column2, and the height of the main body of the column 4 is The height is H-column1, the current Z-axis position of the spindle head 5 is Z-center (variable value), and the length from the center Oc of the column 4 to the front surface of the column 4 is L-column. . The length from the front surface of the column 4 to the center Os of the spindle 10 is L-SP, and the length from the center Os of the spindle 10 to the center Ot of the table 3 is L-table.

  The height of the base of the spindle head 5 is H-SP-1, the height from the bottom surface of the spindle head 5 to the Z-axis position is H-SP-2, and the height of the tool 12 is H-tool. At this time, there is a relationship of H-work + H-tool + H-SP-2 = Z-center + H-column2, where H-work and Z-center are variable values and the others are fixed values. The value of H-work can be obtained from the current Z-center value and H-tool value.

  Moreover, FIG. 6 shows the inclination angle due to the warp of each part of the machine tool main body 1 used for this calculation. Here, the Y axis direction center Ob line of the base 2 is used as a reference line, the inclination angle of the front end face of the base 2 is θ-base-F, and the inclination angle of the rear end face of the base 2 is θ-base-R. The tilt angle at the center Ot of the table 3 is θ-table, and the tilt angle at the center Oc of the column 4 is θ-column.

  Now, calculation examples will be described in the following order. In the following description, the reference temperatures measured and stored by the temperature sensors 18 to 24 are respectively TB-UF-0, TB-BF-0, TB-UR-0, TB-BR-0, It is represented by TC-0, TSP-0, and TT-0. That is, it is assumed that a subscript “−0” is added after the measured temperature (T plus subscript) of each of the temperature sensors 18 to 24.

(A) Displacement amount due to elongation of base 2 Elongation [δb1-table] due to expansion displacement on the table 3 side of the base 2 is
[Δb1-table] = λ × ΔTBF × (S-table)
It becomes. However, ΔTBF = (TB−BF) − (TB−BF−0).

Similarly, the elongation [δb1-column] due to the expansion displacement on the column 4 side of the base 2 is
[Δb1-column] = λ × ΔTUR × (S-column)
It becomes. However, ΔTUR = (TB−UR) − (TB−UR−0).

Since the displacement amount due to the elongation of the base 2 is the sum of them, [δb1-table] + [δb1-column].
(B) Inclination displacement amount due to warping of base 2 First, the displacement amount [δb2-table] at the machining point P due to the inclination of the base 2 on the table 3 side is obtained as follows.

(B-1) The inclination [θ-base-F] of the front end portion of the base 2 is obtained by the following equation.

(B-2) The inclination [θ-table] at the center Ot of the table 3 is as follows by proportional distribution.

(B-3) Since the difference in displacement amount between the center Ot of the table 3 and the machining point P is very small (about error), [δb2-table] can be approximated as follows.

  Similarly, the displacement [δb2-column] at the machining point P due to the inclination of the base 2 on the column 4 side is obtained as follows.

(B-4) The inclination [θ-base-R] of the rear end portion of the base 2 is obtained by the following equation.

(B-5) The inclination [θ-column] at the center Oc of the column 4 is as follows by proportional distribution.

(B-6) The displacement [δb2-column] at the processing point P can be approximated as follows.

  The amount of tilt displacement due to the warp of the base 2 can be obtained by [δb2-table] + [δb2-column].

(C) Displacement amount due to elongation of column 4, spindle head 5, table 3 The displacement amount [δ-other] at machining point P due to elongation of column 4, spindle head 5, table 3 can be obtained by the following equation. it can.

[Δ-other] = λ × [(ΔTSP) × (L-SP) + (ΔTC) × (L-column)
+ (ΔT T) × (L-table)]
From the above (a) to (c), the displacement amount δ in the Y-axis direction as a whole at the processing point P is:
Displacement amount δ = [δb1-table] + [δb1-column] + [δb2-table]
+ [Δb2-column]-[δ-other] (1)
It becomes.

  However, since the above is a theoretical value, it is more desirable to add some correction depending on the structure of the machine. That is, it is effective to multiply each term by a correction coefficient (parameter) as follows.

Displacement amount δ = α1 × [δb1-table] + β1 × [δb2-table] +
α2 × [δb1-column] + β2 × [δb2-column] −
γ × [δ-other] (2)
Note that the determination of the parameters α1, β1, α2, β2, and γ at this time can be optimized relatively easily by using a well-known linear programming method in mathematical engineering.

  The flowchart of FIG. 3 shows the processing procedure of the machining operation including the correction of the thermal displacement executed by the control device 15. That is, first, in step S1, for example, based on the operation of the operation panel 17 of the operator, the initial temperature of each temperature measurement location is measured by the temperature sensors 18 to 24 at the same time. At this time, for example, the temperature in the initial state when the setting of the jig with respect to the machine tool main body 1 before the machining operation is completed (before the machining operation is started) is measured. In step S2, the measured temperatures are stored as reference temperatures TB-UF-0, TB-BF-0, TB-UR-0, TB-BR-0, TC-0, TSP-0, TT-0. 16 (stored).

  In step S3, the machining program is activated, and in the next step S4, the machining program is interpreted for each block. Here, a thermal displacement correction command is inserted at an appropriate position in the machining program, and the presence or absence of a correction command signal is determined in step S5. If there is no correction command signal (No in step S5), it is determined in step S6 whether it is a program end code. If it is not a program end code (No in step S6), the process proceeds to step S7 and the machining operation is executed. When the machining operation for one block is performed, the process returns to step S4, and the next block is interpreted. If it is a program end code (Yes in step S6), the process is terminated.

  If there is a correction command signal in the block of the machining program (Yes in step S5), first, in step S8, each temperature sensor 18-24 uses the current temperature TB of each temperature measurement location. -UF, TB-BF, TB-UR, TB-BR, TC, TSP, TT are measured. In the next step S9, the temperature difference between the measured temperature and the stored reference temperature is calculated at each temperature measurement location.

  In the next step S10, the current positioning machine coordinates (including the value of Z-center) are read, and in step S11, tool length (H-tool) data is read. In step S12, the displacement amount δ and thus the correction amount of the machining point P is calculated using the above-described relational expression (the expression (1) or (2)). Next, in step S3, the position in each axial direction is shifted so as to cancel the displacement amount δ, and thus the thermal displacement is corrected. At this time, the correction in the Y-axis direction is performed as described above, and at the same time, the correction of the thermal displacement in the Z-axis direction caused mainly by the thermal expansion and contraction of the ball screw is also performed. In step S7, the machining operation is executed.

  As a result, the temperature of each component of the machine tool body 1 is measured by the plurality of temperature sensors 18 to 24, and the warp caused by the difference in temperature change between the upper and lower surfaces of the base 2 is caused. The temperature sensors 18 to 21 are provided at the positions to be considered (front and rear portions on the upper and lower surfaces, respectively). As a result, the degree of temperature change of each constituent part can be detected more precisely, and the amount of thermal displacement of each constituent part in each axial direction, particularly in the Y-axis direction, can be estimated (calculated) with sufficient certainty. Thus, the machining accuracy can be sufficiently increased by the correction.

  Now, a method for determining the optimum temperature measurement position (attachment position of the temperature sensors 18 to 24) according to the present embodiment will be described below with reference to FIGS. In the present embodiment, for example, a general-purpose personal computer is used to execute this determination method, and a temperature measurement position determination program is executed. In the present embodiment, for example, in the design stage of the machine tool (machine main body 1), an optimum temperature measurement position is determined, and a data acquisition process described later is also executed by analysis using the computer. It is supposed to be.

  In the temperature measurement position determination method according to the present embodiment, the machine body 1 is divided into a plurality of temperature measurement blocks, and a candidate point setting step (candidate points) for setting a plurality of temperature measurement candidate points for each block. Setting step) and a data acquisition step (data acquisition step) for obtaining data of temperature change of each candidate point and displacement amount of the processing point for each time series in accordance with a thermal state change of the machine body 1 assumed at the time of processing ) And data on the temperature change of each candidate point and the displacement amount of the machining point, using a genetic algorithm, one predetermined relational expression for each block (the above formula (1) or (2) And an optimum position calculation step (optimum position calculation step) for obtaining an optimum temperature measurement position satisfying the equation (1) is sequentially executed.

  The flowchart of FIG. 7 shows a processing procedure (main routine) executed by the computer according to the temperature measurement position determination program. The flowchart of FIG. 8 shows a specific processing procedure for determining the optimum temperature measurement position using the genetic algorithm in step S24.

  In FIG. 7, first, in step S21, a 3D model for analysis of the machine tool body 1 is created. At this time, analysis conditions, physical property values, boundary conditions and the like necessary for the subsequent analysis processing are also input. In the next step S22, a temperature measurement block is set, and a process for setting a plurality of candidate points for each block is executed. Here, as described above, since seven temperature measurement positions are provided in the machine tool main body 1, the block includes the front upper surface side of the base 2, the front lower surface side of the base 2, the rear upper surface side of the base 2, There are seven of the lower surface of the rear part of the base 2, the table 3, the spindle head 5, and the column 4.

  In the present embodiment, 5 to 7 candidate points, and 39 candidate points as a whole, are set in each block. Specifically, as shown in FIGS. 9 and 10, there are six points M <b> 1 to M <b> 6 (see FIGS. 10D and 10E) on the front upper surface side of the base 2, and the front lower surface side of the base 2. There are five points M7 to M11 (see FIGS. 9 and 10D), and five points M12 to M16 (see FIGS. 10A and 10E) on the rear upper surface side of the base 2, and Five points M17 to M21 (see FIG. 9 and FIG. 10A) on the rear lower surface side, and seven points M22 to M28 on the table 3 (rear upper surface side) (see FIG. 9 and FIG. 10C), The spindle head 5 (the rear upper surface side) has six points M29 to M34 (see FIGS. 9 and 10B), and the column 4 has five points M35 to M39 (see FIGS. 9 and 10A). Candidate points were set for each. In the following description, the seven blocks are referred to as A block to G block in order.

  Next, in step S23, the temperature change Δt of each candidate point (M1 to M39) for each time series and the machining point P when a predetermined temperature change is given to the machine tool body 1 by the analysis process (CAE). A process of calculating data of the displacement amount δ (referred to as temperature data) is executed. For this analysis process, software capable of performing non-stationary (non-linear) heat transfer analysis is used. In this embodiment, for example, MSC. “MSC.Marc®” from Software was used.

  Here, assuming that the temperature of the cutting water flowing on the upper surface of the base 2 gradually changes (rises), the temperature of the upper surface of the base 2 is set to room temperature (20 as shown in FIG. 11A). The temperature is gradually increased (for example, about 10 deg.) Over 6 hours from the temperature (° C.), and then allowed to cool to room temperature by being left to cool (6 hours). As shown in FIG. 11B, the temperature data includes the temperature change Δt of each candidate point (M1 to M39) and the displacement δ at the processing point P when such a temperature change of the upper surface of the base 2 is given. Is taken every 10 minutes (0 to 720 minutes).

  When the temperature data as shown in FIG. 11B is obtained in this way, in the next step S24, one optimal temperature measurement position for each block using the genetic algorithm from the temperature data. Is required. At this time, the optimum temperature measurement position is the relationship between the temperature change Δt of each candidate point in each of the blocks A to G and the displacement amount δ at the processing point P over the entire time ((( It is obtained as a combination of candidate points satisfying the expression (1) or (2)). In step S25, the determined optimum temperature measurement position is output, and the process ends.

  Now, a detailed procedure of the process of determining the optimum temperature measurement position (step S24) using the genetic algorithm will be described with reference to the flowchart of FIG. 8 and FIGS. In this process, an individual group (initial group) is first created in step S31. In the present embodiment, as shown in FIG. 12, the individual is composed of 39-bit genes corresponding to the 39 candidate points M1 to M39.

  In this case, the sixth to sixth bits of the individual correspond to the A block candidate points M1 to M6, respectively, and the seventh to eleventh bits correspond to the B block candidate point M7. It corresponds to each of ~ M11. In each of the blocks A to G, only one measurement point is selected at random, and the corresponding bit is set to 1. The other bits are 0. In FIG. 12, the boundaries between the blocks are divided by vertical bars, and the divided positions (any one of the six locations) are crossover points to be described later. The total number of individuals (number of combinations) is 6 × 5 × 5 × 5 × 7 × 6 × 5 = 157500 (type).

  In the next step S32, n, for example, 20 individuals are evaluated. For the first process (first generation), 20 random individuals are selected. For the evaluation, the data of the temperature change Δt of the candidate point where the bit is 1 is adopted, and the displacement amount is obtained by substituting it into the above relational expression, and the absolute value of the difference from the displacement amount δ in the temperature data is calculated. This was performed over the entire time (72 ways), and the reciprocal of the average value was used as the fitness. Therefore, the smaller the error, the higher the fitness.

  In step S33, it is determined whether or not it has converged. If it has not converged yet (No), the selection in step S34, the crossover in step S35, and the mutation process in step S36 are performed in order. Specifically, as shown in FIG. 13, in the process of selection (step S34), when 20 individuals are evaluated (FIG. 13 (a)), the individuals are evaluated in order of evaluation (in order of high fitness). ), Only the 1st to 10th individuals are selected, and the 11th to 20th individuals are deleted (淘汰) (FIG. 13B).

  In the next crossover (step S35), as shown in FIG. 13 (c), the first-ranked individual, the tenth-ranked individual, the second-ranked individual, the ninth-thick individual, the third-ranked individual, and the eighth-ranked individual The 4th individual and the 7th individual, the 5th individual and the 6th individual are crossed in pairs. This crossover is performed by dividing each individual into upper bits and lower bits at the crossover points and exchanging the lower bits. At this time, the crossover points are the boundaries between the blocks (vertical bars in FIG. 12). Is selected at random each time. As a result, 10 crossed individuals are obtained.

  The mutation (step S36) duplicates the above-mentioned first-ranked individuals twice, and randomly selects any one bit of these individuals to be 0, and sets any other bit in the same block. This is performed by selecting a random number to 1 (FIG. 13D). This gives two mutated individuals. Then, as shown in FIG. 13 (e), 10 individuals by crossover and 2 individuals by mutation, and 8 individuals from the first to the eighth place were left as elite preservation, Twenty individuals are left in the next generation, and the process returns to step S32 and the evaluation is repeated again.

  By repeating the above process over generations, only excellent individuals will be left, and eventually converge (the 20 individuals will have almost no difference and the fitness will match. ) And an optimum solution is obtained (Yes in step S33), and this process ends. Thereby, the optimum solution can be obtained efficiently in a short time.

  By the way, in this embodiment, it converged in about 250 generations. As a result, as the optimum temperature measurement position, the candidate point M3 (or M4) in the A block (the front upper surface side of the base 2), and the candidate point M11, C block (the base in the front lower surface side of the base 2) 2 at the rear upper surface side), candidate point M20 at the D block (base 2 rear lower surface side), candidate point M25 at the E block (Table 3), candidate point M31 at the F block (spindle head 5), G In the block (column 4), the candidate point M35 is selected (determined).

  In this case, candidate points M3 and M15 located at the substantially central portion in the left-right direction of the base 2 were selected for the front upper surface side and the rear upper surface side of the base 2, respectively. For the spindle head 5 and the column 4, candidate points M31 and M35 located substantially in the center are selected. These are almost as expected. On the other hand, on the front lower surface side and the rear lower surface side of the base 2, candidate points M11 and M20 located on the side surface portion instead of the center are selected. Also for Table 3, candidate point M25 located at the corner instead of the center was selected. Although these were unexpected, it is considered that such a result is obtained because there is almost no difference in temperature between the lower surface side of the base 2 and the table 3 between the central portion and the end portion.

  As described above, according to the present embodiment, there is provided a machine tool having a function of estimating and correcting the thermal displacement amount δ at the processing point P based on the temperature measurement at a plurality of positions of the machine body 1. A large number of candidate points M1 to M39 are set for each measurement block, temperature data Δt of each candidate point M1 to M39 for each time series and temperature data of the displacement amount of the processing point P are obtained, and genetic data is obtained from the temperature data. By using the method of the genetic algorithm, it is possible to obtain an excellent effect that one optimum temperature measurement position can be easily obtained for each block. In particular, in the present embodiment, since the temperature data acquisition process is performed by analysis using a computer, it is possible to obtain necessary temperature data at the design stage where there is no actual machine yet. It is possible to obtain a suitable temperature measurement position.

In step S34 of the present embodiment, only the 1st to 10th individuals are selected, but 10 individuals among the 1st to 20th individuals may be selected at random.
FIG. 14 shows another embodiment of the present invention. This embodiment differs from the above embodiment in a temperature measurement position determination method for determining an optimum temperature measurement position of the machine tool main body 1, and a data acquisition step (data acquisition step) for obtaining temperature data is performed on an actual machine. It is in the point made to carry out by the experiment using. Only differences from the flowchart of FIG. 7 in the above embodiment will be described below. In addition, about the structure of the machine tool main body 1, it shall be equivalent to what was demonstrated in the said embodiment, and a code | symbol is also used in common.

  The flowchart of FIG. 14 shows a processing procedure for determining the temperature measurement position. Here, instead of the processing of steps S21 to S23 in the above embodiment (flowchart of FIG. 7), the processing of steps S41 to S44 is executed. That is, first, in step S41, temperature sensors are installed at all of a plurality of candidate points (for example, 39 points M1 to M39) of the actual machine (machine tool main body 1). In step S42, a displacement measuring sensor is installed to measure the distance (in the Y-axis direction) between the main shaft 10 and the table 3, and thus the relative displacement δ. For example, an eddy current proximity sensor is used as the displacement measuring sensor.

  In the next step S43, the cutting water is heated by the heater while flowing the cutting water on the upper surface of the base 2, and the temperature is gradually raised. As in the above-described embodiment, the upper surface of the base 12 is shown in FIG. As shown in (2), the temperature is gradually raised from room temperature (20 ° C.) over 6 hours (for example, about 10 deg), and then allowed to cool (6 hours), thereby gradually returning to room temperature. . In step S44, the temperature change Δt at each candidate point (M1 to M39) detected by each temperature sensor and the displacement amount δ measured by the displacement amount measuring sensor at that time are obtained every 10 minutes (0 minute to 720 minutes). ) To obtain temperature data as shown in FIG. 11 (b).

  Thereafter, as in the above embodiment, in the next step S24, one optimal temperature measurement position is obtained for each block from the acquired temperature data using a genetic algorithm (step S24). The determined optimum temperature measurement position is output (step S25), and the process ends.

  According to such a configuration, similarly to the above embodiment, the machine tool having a function of estimating and correcting the thermal displacement amount δ at the processing point P based on the temperature measurement at a plurality of locations of the machine body 1 is provided. Then, a large number of candidate points M1 to M39 are set for each of the plurality of temperature measurement blocks, and temperature data Δt of each candidate point M1 to M39 for each time series and the displacement amount temperature data of the processing point P are obtained, By using a genetic algorithm method from the temperature data, it is possible to obtain an excellent effect that one optimal temperature measurement position can be easily obtained for each block. In addition, since the temperature data acquisition process is executed by an experiment using an actual machine, more reliable temperature data can be obtained.

  In each of the embodiments described above, seven temperature blocks are set in the machine tool body 1, but two blocks are set in the front and rear portions of the column 4, and the spindle head 5 is also set up and down two. Various modifications can be made to the setting method of the temperature measurement block, such as setting of individual blocks. Of course, the present invention can be applied to various types of machine tools, such as a so-called horizontal type having a main shaft extending in the horizontal direction. At this time, needless to say, the predetermined relational expression is set for each model of the machine tool.

  Also, as temperature measurement candidate points, a large number of 10 points or 20 points may be set in one block, and a specific method of the optimum position calculation process using a genetic algorithm will be described. However, the above embodiment only shows an example, and various modifications can be made with respect to, for example, the number of individuals to be selected and the crossover method. In addition, the present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented without departing from the scope.

The perspective view which shows one Embodiment of this invention, and shows schematically the structure of the main body of the machine tool which fractured | ruptured one part Block diagram schematically showing the electrical configuration of the machine tool The flowchart which shows the process sequence of the processing operation including correction | amendment of the thermal displacement which a control apparatus performs Right side view exaggeratingly showing the thermal displacement of each component of the machine tool body Right side view showing the dimensions of each part of the machine tool body used to estimate the displacement Right side view showing the tilt angle due to the warp of the base Flow chart showing processing procedure for determining temperature measurement position The flowchart which shows the processing content of step S24 of FIG. 7 in detail. Left side view of the machine tool body to indicate the position of the set candidate points It is for showing the position of the set candidate point. The rear view (a) of the machine tool body, the top view (b), the rear view (c) of the table, the front view (d) of the machine tool body, Top view (e) A diagram showing a temperature change given to the upper surface of the base at the time of analysis and a diagram showing the temperature data obtained by the analysis in a tabular format (b) Diagram for explaining individual in decision processing by genetic algorithm Diagram for explaining the process of evaluation, selection, crossover, and mutation FIG. 7 equivalent view showing another embodiment of the present invention

  In the drawings, 1 is a machine tool body, 2 is a base, 3 is a table, 4 is a column, 5 is a spindle head, 6 is an XY moving mechanism, 10 is a spindle, 12 is a tool, 15 is a control device (displacement amount detection means, Correction means), 18 to 24 are temperature sensors, W is a workpiece, P is a machining point, and M1 to M39 are candidate points.

Claims (6)

The machining is performed while moving the tool relative to the workpiece according to the machining data, and the thermal displacement amount of the machining point is obtained by a predetermined relational expression based on the temperature measurement at a plurality of locations of the machine body. In a machine tool having a function of correcting a relative movement amount of a tool, a method for determining a position where the temperature measurement is to be performed,
The machine body is divided into a plurality of temperature measurement blocks, a candidate point setting step for setting a plurality of temperature measurement candidate points for each block, and
A data acquisition step for obtaining data of temperature change of each candidate point and displacement amount of the machining point for each time series accompanying a thermal state change of the machine body assumed at the time of machining,
Using a genetic algorithm, one individual measurement position is selected for each block from the data on the temperature change of each candidate point and the displacement amount of the machining point, and an individual configured with 1 corresponding bit is evaluated. And an optimum position calculating step for obtaining a temperature measurement position which is a candidate point of the temperature measurement with a small difference between the temperature change of each candidate point and the displacement amount data of the machining point, one for each block. A method for determining a temperature measurement position of a machine tool, comprising:   2. The method for determining a temperature measurement position of a machine tool according to claim 1, wherein the data acquisition step is executed by analysis using a computer.   The method for determining a temperature measurement position of a machine tool according to claim 1, wherein the data acquisition step is executed by an experiment using an actual machine. The machine body includes a column having a spindle head provided with a table for supporting the workpiece and the tool on the base, and is configured to flow a cutting fluid on the upper surface of the base. Has been
4. The temperature measurement position determination method for a machine tool according to any one of claims 1 to 3, wherein a total of four temperature measurement blocks are set for the base on the upper surface side and the lower surface side respectively on the front and back sides. .   In addition to the thermal expansion / contraction of each part of the machine main body, the predetermined relational expression takes into account the warpage caused by the difference in the temperature rise between the front and back portions of the upper surface side and the lower surface side of the base. 5. The temperature measurement position determining method for a machine tool according to claim 4, wherein the temperature measurement position is determined. The machining is performed while moving the tool relative to the workpiece according to the machining data, and the thermal displacement amount of the machining point is obtained by a predetermined relational expression based on the temperature measurement at a plurality of locations of the machine body. A temperature measurement position determination program for a machine tool, which causes a computer to execute the following steps in order to determine the position where the temperature measurement is to be performed in a machine tool having a function of correcting the relative movement amount of a tool.
A candidate point setting step of dividing the machine main body into a plurality of temperature measurement blocks and setting a plurality of temperature measurement candidate points for each block.
A data acquisition step for obtaining data of temperature change of each candidate point and displacement amount of the machining point for each time series accompanying a thermal state change of the machine main body assumed at the time of machining.
Using a genetic algorithm, one individual measurement position is selected for each block from the data on the temperature change of each candidate point and the displacement amount of the machining point, and an individual configured with 1 corresponding bit is evaluated. And an optimum position calculating step for obtaining a temperature measurement position which is a candidate point of the temperature measurement with a small difference between the temperature change of each candidate point and the displacement amount data of the machining point, one for each block.

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