JP3292454B2 - Machine tool thermal displacement calculator and storage medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool thermal displacement calculating apparatus which is mounted on a machine tool and calculates the amount of thermal displacement generated by the machine tool, and a storage medium for realizing the apparatus.

[0002]

2. Description of the Related Art Conventionally, processing means for cutting or drilling a work or assembling parts on a substrate, and driving means for changing the relative position between the processing means and a workpiece such as a work or a substrate. There is a machine tool having: Generally, in a machine tool that performs machining such as cutting, a holding mechanism for holding a tool such as a drill or a tap, a spindle drive mechanism for rotating and driving the tool held by the tool, and a feed of the tool in the X-axis direction -Axis feed mechanism for feeding the tool, Y-axis feed mechanism for feeding the tool in the Y-axis direction, Z-axis feed mechanism for feeding the tool in the Z-axis direction, a control device for controlling these feed mechanisms, etc. It has.

As an example, there is a machine tool 10 shown in FIGS. As shown in FIG. 13, the machine tool 10 includes a table 14 for placing a workpiece W (see FIG. 1) inside a splash guard 12 for preventing scattering of cutting chips, such as a drill or a tap. An ATC magazine 16 for tool change, a machine tool main body (hereinafter also simply referred to as a main body) 20, and the like are arranged. In addition, the splash guard 12 is provided with an operation panel 22, a work exchange port 24 for entering and exiting the work W and maintenance, an inspection hatch 26 mainly for maintenance, and the like.

As shown in FIG. 14, a main body 20 has a main shaft 2 for holding a tool T (FIG. 1) such as a drill or a tap.
8, a spindle motor 30 for rotating and driving the spindle 28, and a nut portion 3 containing a large number of steel balls and fixed to the spindle side.
2, a ball screw mechanism 36 including a ball screw 34 inserted into the nut portion 32, a Z-axis motor 38 for rotating and driving the ball screw 34, a guide rail 40 disposed parallel to the ball screw 34, the guide rail 40 and the main shaft 28.
It has a slide 42 and the like connecting the side.

In the main body 20, a Z-axis feed mechanism for feeding in the Z-axis direction is constituted by the ball screw mechanism 36 and the Z-axis motor 38. The ball screw 34 is rotated by the Z-axis motor 38 to rotate the main shaft 28. The movement in the Z-axis direction is performed. Further, the table 14 shown in FIG. 13 can be moved in the X-axis and Y-axis directions, and together with the movement of the main shaft 28 in the Z-axis direction, the relative position of the workpiece W and the tool T in the X, Y, and Z-axis directions. Can be changed.

[0006] In such a machine tool, for example, frictional heat is generated by driving the ball screw mechanism 36, and the ball screw 34 may be extended. Also, other mechanisms generate heat. Such heat generation causes thermal displacement in the machine tool. If this thermal displacement occurs, for example, in the Z-axis direction, errors occur in the depth of the groove formed in the workpiece W, the height of the step, and the like. If the tolerance is sufficiently larger than the amount of thermal displacement, the processing error due to such thermal displacement does not cause much problem, but if not, the thermal displacement needs to be corrected. Therefore, a thermal displacement calculating device for calculating the thermal displacement of the machine tool is provided, and in controlling the driving means according to a predetermined machining program, the driving means is controlled while performing a correction according to the thermal displacement. (For example, JP-A-62-88548).

[0007]

However, in the conventional machine tool thermal displacement calculating apparatus, the thermal displacement is calculated while the machine tool is being driven, so that a system for executing the processing is used. Had to be constantly running. For this reason, the load involved in the calculation process was large. Therefore, the applicant of the present application has noticed that when the temperature is increased by continuing to drive the machine tool, the amount of heat generation and the amount of heat radiation eventually become balanced (the amount of thermal displacement at this time is referred to as the amount of saturated thermal displacement). Then, it was proposed to calculate the amount of thermal displacement as follows. That is, during the operation of the machine tool, the thermal displacement is calculated based on the saturated thermal displacement and the driving time of the machine tool, and when the thermal displacement becomes substantially equal to the saturated thermal displacement, the thermal displacement is thereafter calculated. Is substituted for the value of the saturated thermal displacement (Japanese Patent Application No. 8-298866).
issue). In this case, given the exact saturated thermal displacement,
The amount of thermal displacement at each time can be accurately calculated, and the load involved in the calculation process can be reduced.

[0008] Further, the applicant of the present invention, when given the value of the saturated thermal displacement (for example, L), the thermal displacement l when the machine tool is driven for t time, l = L · ｛1 -Exp (-γt)｝, or after driving the machine tool until the thermal displacement reaches the saturated thermal displacement L, and then calculating the thermal displacement 1 when the time t has elapsed after stopping the driving. , L = L · exp (−γt) (where γ is a constant specific to the machine tool).

However, the amount of thermal displacement actually generated in a machine tool changes according to the characteristics of each machine tool and the use environment. Further, the characteristics of the machine tool may change with time. For this reason, if the parameters such as L and γ are fixed uniformly and the thermal displacement of the machine tool is calculated, it is difficult to calculate an accurate thermal displacement according to the characteristics of each machine tool. . SUMMARY OF THE INVENTION It is an object of the present invention to provide a machine tool thermal displacement calculating device capable of calculating an accurate thermal displacement according to the characteristics of each machine tool and the use environment.

[0010]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the invention according to claim 1 comprises a processing means for processing a workpiece, and the processing means and the workpiece. A machine tool having a drive means for changing the relative position of the machine tool, the machine tool thermal displacement calculating apparatus for calculating the machine tool thermal displacement, wherein the drive state for detecting the machine tool drive state Detecting means; displacement calculating means for calculating the thermal displacement of the machine tool based on the driving state detected by the driving state detecting means; and measured value detecting means for detecting the measured value of the thermal displacement of the machine tool And, comparing the thermal displacement calculated by the displacement calculating means with the measured value of the thermal displacement detected by the measured value detecting means, and calculating a correction value for the thermal displacement calculated by the displacement calculating means. Correction value calculating means for calculating, Correction value storage means for storing the correction value calculated by the positive value calculation means; and displacement amount correction for correcting the thermal displacement amount calculated by the displacement amount calculation means using the correction value stored in the correction value storage means. Means.

According to the present invention, the displacement calculating means calculates the thermal displacement of the machine tool based on the driving state detected by the driving state detecting means. The actually measured value detecting means detects the actually measured value of the thermal displacement of the machine tool, and the correction value calculating means calculates the actual value of the thermal displacement calculated by the displacement calculating means and the actually measured value of the thermal displacement detected by the actually measured value detecting means. Compare with
A correction value for the thermal displacement calculated by the displacement calculator is calculated. Then, the correction value storage means stores the correction value calculated by the correction value calculation means, and the displacement amount correction means uses the correction value stored in the correction value storage means to calculate the thermal displacement calculated by the displacement amount calculation means. Correct the amount.

As described above, in the present invention, the measured value of the thermal displacement of the machine tool is detected by the measured value detecting means, and the thermal displacement calculated by the displacement calculating means is corrected based on the measured value. . For this reason, an accurate amount of thermal displacement can be calculated according to the characteristics of each machine tool and the use environment. Moreover, in the present invention, instead of using the actual measured value of the thermal displacement as it is, a correction value is calculated from the actual measured value, and the thermal displacement calculated by the displacement calculating means is corrected using the corrected value. I have. For this reason, once the actual measurement value is detected, an accurate thermal displacement amount can be calculated using the correction value calculated from the actual measurement value, and it is necessary to detect the actual measurement value every time the thermal displacement amount is calculated. There is no.

The applicant of the present application has proposed a method of detecting an actual measurement value as follows.
For example, it has been proposed to detect that the processing means has relatively moved to a predetermined position with respect to the workpiece by a contact-type sensor or the like, and to measure the thermal displacement based on the driving amount of the driving means at that time. However, in this case, actual processing cannot be performed unless the processing of the workpiece by the processing means is interrupted once. Therefore, if the thermal displacement amount is obtained only by actual measurement, the working efficiency of the machine tool will be reduced. In the present invention, it is not necessary to detect an actual measurement value each time the amount of thermal displacement is calculated as described above, so that the working efficiency of the machine tool is not reduced and the above-described method is performed according to the characteristics of each machine tool. It is possible to accurately calculate the amount of thermal displacement.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the correction value calculating means is configured to determine the thermal displacement calculated by the displacement calculating means and the thermal displacement detected by the actually measured value detecting means. The ratio of the displacement to the measured value is calculated as a correction value, and the displacement correction means corrects the thermal displacement calculated by the displacement calculation means by multiplying or dividing the correction value. And

According to the present invention, the ratio between the thermal displacement calculated by the displacement calculating means (hereinafter also referred to as a calculated value) and the measured value detected by the measured value detecting means is calculated as a correction value, and the correction value is multiplied. Alternatively, the above thermal displacement is corrected by dividing. When the absolute value of the calculated value and the measured value is extremely large, the absolute value of the difference between the two tends to increase. Therefore, when the difference between the calculated value and the actually measured value is calculated as a correction value, it becomes difficult to use the same correction value when the displacement amount calculating means calculates a small thermal displacement amount.

On the other hand, in the present invention, the ratio between the calculated value and the actually measured value is calculated as a correction value, and the thermal displacement calculated by the displacement calculating means is multiplied or divided. For this reason, when the displacement amount calculating means calculates a small thermal displacement amount, a small amount of correction can be performed according to the small thermal displacement amount. Therefore, in the present invention, in addition to the effect of the first aspect of the present invention, it is possible to calculate an accurate thermal displacement even when the absolute value of a calculated value and a measured value that are the basis for calculating a correction value is extremely large. There is an effect that can be performed.

According to a third aspect of the present invention, in addition to the configuration of the first aspect, the correction value calculating means detects the thermal displacement calculated by the displacement calculating means and the thermal displacement detected by the actually measured value detecting means. The difference between the actual displacement value and the measured value is calculated as a correction value, and the displacement correction means corrects the thermal displacement calculated by the displacement calculation means by adding or subtracting the correction value. And

According to the present invention, the difference between the thermal displacement amount (calculated value) calculated by the displacement amount calculating means and the actual measured value detected by the actual measured value detecting means is calculated as a correction value, and the correction value is added or subtracted. This corrects the thermal displacement. If the absolute values of the calculated value and the actually measured value are extremely small, a slight measurement error will be reflected in the value of the ratio between the two. Therefore, when the ratio between the calculated value and the actually measured value is calculated as a correction value, and the value is multiplied or divided by the thermal displacement calculated by the displacement calculating means, the displacement calculating means calculates a large thermal displacement. Sometimes, a measurement error or the like may be multiplied or divided by the calculated value and greatly reflected.

On the other hand, in the present invention, the difference between the calculated value and the actually measured value is calculated as a correction value, and is added to or subtracted from the thermal displacement calculated by the displacement calculating means. Therefore, regardless of the absolute value of the thermal displacement calculated by the displacement calculating means,
The same amount of correction can always be made. Therefore, in the present invention, in addition to the effect of the invention described in claim 1, it is possible to calculate an accurate amount of thermal displacement even when the absolute value of the calculated value serving as the basis for calculating the correction value and the measured value is extremely small. There is an effect that can be performed.

According to a fourth aspect of the present invention, in addition to any one of the first to third aspects, the measured value detecting means may be configured such that when the processing means relatively moves to a predetermined position with respect to the workpiece, Processing means detecting means for detecting the processing means; processing means moving means for controlling the driving means to relatively move the processing means to a position detected by the processing means detecting means; By means of transportation
The driving amount of the driving means required to relatively move the processing means to a position detected by the processing means detecting means, and the driving amount required when no thermal displacement occurs in the machine tool Are compared with each other, and the actual measurement value is detected based on the comparison result.

In the actually measured value detecting means of the present invention, the processing means is relatively moved by the processing means moving means to a position detected by the processing means detecting means, and then the driving means required for the relative movement is driven. The amount is compared with the drive amount required when no thermal displacement occurs in the machine tool, and an actual measured value of the thermal displacement of the machine tool is detected based on the comparison result. For this reason, it is possible to automatically and easily detect an accurate measured value of the thermal displacement of the machine tool. Further, in the present invention, the processing means detecting means can be a simple one such as a contact type sensor, and the processing means moving means can have a common configuration with the driving means. Therefore, in the present invention, in addition to the effect of the invention according to any one of claims 1 to 3, it is possible to reduce the manufacturing cost by simplifying the configuration of the apparatus, and to calculate the parameters more accurately and easily. There is an effect that it can be done.

According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect, the actually measured value detecting means detects the actually measured value a predetermined time after the start of driving of the machine tool.
The correction value calculation means calculates the correction value, and updates the correction value stored in the correction value storage means.

In the present invention, the measured value detecting means detects the measured value after a predetermined time from the start of driving of the machine tool. Then, the correction value calculation means calculates the correction value each time,
The correction value stored in the correction value storage means is updated. Therefore, each time the machine tool is started, the correction value can be automatically updated based on the actually measured value. Therefore,
According to the present invention, in addition to the effect of the invention described in claim 4, there is an effect that a more accurate amount of thermal displacement can be more easily calculated according to a change in a characteristic of a machine tool or a use environment. Further, if the configuration of the present invention is employed, it is possible to calculate a sufficiently accurate thermal displacement amount by performing the detection of the actual measurement value only once after the predetermined time from the start of driving. Therefore, the working efficiency of the machine tool can be further improved.

According to a sixth aspect of the present invention, in addition to the configuration according to any one of the first to fifth aspects, an adjustment value determined corresponding to a condition affecting the thermal displacement amount is corrected by the displacement amount correction. The apparatus further comprises a displacement adjusting means for adding or subtracting to or from the thermal displacement corrected by the means to obtain the thermal displacement of the machine tool.

The thermal displacement of the machine tool is affected by various conditions in addition to the moving distance and the driving time. For example, when the temperature is relatively low in the morning or the like, the temperature rise of the machine tool becomes gentle, and the error between the calculated thermal displacement and the actual thermal displacement may become nonnegligible. Therefore, in the present invention, the displacement amount adjusting means adds or subtracts an adjustment value determined corresponding to a condition affecting the thermal displacement amount to or from the thermal displacement amount corrected by the displacement amount correcting means, and It is the amount of thermal displacement of the machine. For this reason, in the present invention, in addition to the effect of the invention described in any one of the first to fifth aspects, there is an effect that the amount of thermal displacement of the machine tool can be calculated more accurately. Note that the adjustment value may be input by an operator using an adjustment input unit such as an operation panel, or an adjustment value determined by a preset procedure may be obtained on the thermal displacement amount calculation device side.

According to a seventh aspect of the present invention, in addition to the configuration of the sixth aspect, the adjustment value is determined according to time, and the displacement amount adjusting means selects the adjustment value based on time. It is characterized by using. With this configuration, the error between the calculated amount of thermal displacement and the actual amount of thermal displacement can be automatically and better eliminated automatically in accordance with, for example, the time zone of the day (morning, noon, night, etc.). Can be. Therefore, in the present invention, in addition to the effect of the invention described in claim 6, there is an effect that an accurate amount of thermal displacement can always be calculated regardless of time.

According to an eighth aspect of the present invention, in addition to the configuration of the sixth aspect, the adjustment value is determined in accordance with the environmental temperature of the machine tool, and the displacement amount adjusting means is based on the environmental temperature. And selecting and using the adjustment value. With this configuration, an error between the calculated amount of thermal displacement and the actual amount of thermal displacement can be automatically and better eliminated according to the temperature of the place where the machine tool is installed, that is, the environmental temperature. it can. Therefore, in the present invention, in addition to the effect of the invention described in claim 5, there is an effect that an accurate amount of thermal displacement can always be calculated regardless of the environmental temperature.

[0028] The invention according to claim 9 is used for a machine tool provided with processing means for processing a workpiece, and driving means for changing a relative position between the processing means and the workpiece. A storage medium storing a computer program for calculating a thermal displacement amount of the machine tool, and an actual measurement value detection process of detecting an actual measured value of the thermal displacement amount of the machine tool;
A drive state detection process for detecting a drive state of the machine tool, a displacement amount calculation process for calculating a thermal displacement amount of the machine tool based on the drive state detected by the drive state detection process, and a displacement amount calculation process A correction value for calculating a correction value for the thermal displacement amount calculated by the displacement amount calculation process by comparing the thermal displacement amount calculated by the above with the actual measurement value of the thermal displacement amount detected by the actual value detection process. A calculating process, a correction value storing process of storing the correction value calculated by the correction value calculating process in a predetermined storage unit, and the displacement amount calculating process using the correction value stored in the predetermined storage unit. And a computer program for executing a displacement amount correction process for correcting the calculated thermal displacement amount.

Since the storage medium of the present invention is configured as described above, if the control means such as a computer connected to the machine tool executes the computer program stored in the present invention, the actual measurement according to claim 1 is executed. Value detection means, drive state detection means, displacement amount calculation means, correction value calculation means, correction value storage means, actual measurement value detection processing, drive state detection processing, displacement amount calculation processing, correction value calculation corresponding to the displacement amount correction means Processing, correction value storage processing, and displacement amount correction processing can be executed. Therefore, when the control means executes the computer program stored in the present invention, the first aspect of the present invention is provided.
An effect similar to that of the described invention is obtained. Further, the program of each processing stored in the present invention may include:
If a requirement limited to the invention described in 6, 7, or 8 is added, when the requirement is executed, the corresponding claim 2, 3, or
The same effect as the invention described in 4, 5, 6, 7, or 8 is obtained.

[0030]

Embodiments of the present invention will now be described in detail with reference to the drawings.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The mechanical configuration of a machine tool according to this embodiment is as follows.
1 except that the following detector 49 was provided.
3 and FIG. 14, the description of the mechanical configuration of the machine tool 10 will be omitted by using them.

FIG. 1 is a schematic diagram showing the structure of the detector 49. As shown in FIG. 1, the detector 49 is fixed to one corner of the table 14 and generates a contact signal when the tool T held on the main shaft 28 contacts. Further, the detector 49 is configured so that the position on the Z axis can be changed so that measurement can be performed at an optimum position according to the workpiece W.
When the position is changed, data relating to the position on the Z axis stored in the CPU 72 or the like described later is updated.

FIG. 2 shows a machine tool 10 as a first embodiment.
FIG. 2 is a block diagram illustrating a configuration of a control system. As shown in FIG. 2, the control system is a main shaft control system 50 for controlling the rotation of the main shaft 28, a Z-axis control system 60 for controlling the Z-axis position of the main shaft 28, and the center of this control system. The microcomputer unit 70, the operation panel 22, the detector 49, the X-axis control system (not shown) for controlling the X-axis position of the table 14 and the table 1
4 includes a Y-axis control system (not shown) for controlling the Y-axis position.

The spindle control system 50 includes a spindle motor 30 and a spindle servo amplifier 5 for supplying power to the spindle motor 30.
2, and an axis control circuit 54 for controlling the power supplied to the spindle servo amplifier 52. The axis control circuit 54 controls the operation of the spindle servo amplifier 52 in accordance with an instruction from the CPU 72 of the microcomputer unit 70. Z axis control system 60
Are a Z-axis motor 38, a Z-axis servo amplifier 62 for supplying power to the Z-axis motor 38, and a Z-axis servo amplifier 62.
An axis control circuit 64 for controlling the supply power of
The axis control circuit 64 controls the operation of the Z-axis servo amplifier 62 according to an instruction from the CPU 72 of the microcomputer unit 70. Further, an X-axis control system and a Y-axis control system (not shown) have substantially the same configuration as the main axis control system 50 and the Z-axis control system 60.

The microcomputer unit 70 is composed of a one-chip type CPU 72, a RAM 74, a clock 76, etc., having a built-in ROM and an input / output port for storing a control program and the like, and is configured as a well-known microcomputer. The microcomputer unit 70 (strictly, the CPU 72) controls the spindle control system 50, the Z-axis control system 60, and the like in accordance with a machining program corresponding to the machining to be performed on the workpiece W, and performs a predetermined machining on the workpiece W. is there. Further, the microcomputer unit 70 is connected to the operation panel 22 and the detector 49, and the microcomputer unit 70 is connected to the operation panel 22 or the detector 4.
9 to control the display of images and characters on the liquid crystal display of the operation panel 22 by sending a signal to the operation panel 22, control the blinking of LEDs, and the like.

The RAM 74 is a work area for the CPU 72 as is well known.
A pitch error correction table having the configuration shown in FIG. 3 is provided above. This pitch error correction table is a table for correcting a driving error of the ball screw mechanism 36, for example.

Ball screw mechanism 36 responsible for Z-axis movement
Is the amount of rotation of the ball screw 34 and the amount of movement of the nut 32 due to manufacturing tolerances (ie, the amount of movement of the main shaft 28 in the Z-axis direction).
It is necessary to correct the error since it cannot be avoided. Therefore, an appropriate number of correction points are set (if the length of the ball screw 34 is 500 mm and correction is performed every 20 mm, the number of correction points is 25). An error between the calculated value and the actually measured value is obtained, and a rotation amount (pitch) of the ball screw 34 corresponding to the error is written in a pitch error correction table, and the ball screw 34 is rotated forward or backward by the pitch for each correction point. By doing so, the Z-axis position of the main shaft 28 is accurately adjusted. X axis and Y
The same is true for the axis.

The clock 76 is a so-called electronic clock.
The date can be calculated and the data can be sent to the CPU 72. It should be noted that the CPU 72 has a predetermined cycle,
A built-in counter for incrementing the count value every 1000 seconds is provided, and by using the counter, an elapsed time such as a required time from the start to the end of a certain processing can be measured.

When the machine tool 10 is driven, thermal displacement occurs in the Z-axis direction due to expansion of the ball screw 34 and the like. Thus, the CPU 72 executes the following processing in order to execute the machining program while correcting the thermal displacement. FIG. 4 is a flowchart illustrating a main routine of a process executed by CPU 72. In addition,
The CPU 72 executes this process as an interrupt process at a predetermined timing after the power is turned on, and calculates a thermal displacement amount generated by executing a machining program or the like.

As shown in FIG. 4, when the CPU 72 starts the process, first, in S1 (S represents a step: the same applies hereinafter), the CPU 72 calculates a thermal displacement amount based on the driving state of the machine tool 10. A displacement amount calculation process is performed, and the process proceeds to S3. In S3, it is determined whether or not the thermal displacement calculated in the thermal displacement calculating process in S1 needs to be corrected based on the actually measured value. If it is not necessary (S3: NO), the process returns to S3.
The process proceeds to 1 and the calculation of the thermal displacement is continued. If the correction based on the actually measured value is necessary (S3: YES), the process proceeds to S5 to S9 described below to detect the actually measured value of the thermal displacement amount and change various parameters used in S1. Then, the process proceeds to S1.

Here, the process of calculating the amount of thermal displacement in S1 will be described. FIG. 5 is a flowchart illustrating the details of the thermal displacement amount calculation processing in S1. In this routine, first, S1
At 1, processing is performed for assuming that the moving distance during power-off is 0. As will be described later, when the amount of thermal displacement has been calculated in the past and its influence still remains, it is necessary to calculate the amount of thermal displacement of the machine tool 10 in consideration of the effect. Further, such a thermal displacement amount is generated by the machine tool 10 during a break time in a factory or the like.
May remain even after the power is turned off.
Therefore, in S11, the moving distance of the main shaft 28 in the Z-axis direction while the power is turned off is set to 0.

In the following S12, it is determined based on the output of the clock 76 whether or not a predetermined sampling time (an interval of a minutes) has been reached. If it is not the sampling time (S12: NO), the process stands by, and if it is the sampling time (S12: YES), the process proceeds to S13. In S13, the driving state of the machine tool 10 is detected from the execution state of the machining program and the like, and the movement distance of the main shaft 28 in the Z-axis direction during the sampling time is calculated based on the detected driving state. Then, the process proceeds to S14, and the maximum displacement L as the saturated thermal displacement is calculated as follows.

When the temperature is increased by continuing to drive the machine tool 10, the heat generation and the heat radiation eventually balance. The thermal displacement at this time is the maximum displacement L. When the machine tool 10 is continuously driven in a constant state, the maximum displacement L
Has a correspondence shown in FIG. 6 with respect to the average moving distance of the spindle 28 per unit time. As shown in FIG. 6, the maximum displacement L increases as the average moving distance increases.
This correspondence is represented by a line graph in which the slope becomes gentler when the average moving distance is equal to or more than a predetermined value. This is because when the main shaft 28 moves at a high speed, the heat radiation increases due to the air cooling effect, and the thermal displacement is suppressed. In S14, the moving distance calculated in S13 is converted into an average moving distance per unit time (here, mm / min),
The corresponding maximum displacement L is calculated with reference to the map of FIG. The map in FIG. 6 may be stored in the CPU 72 in the form of a mathematical expression or a data table.

In S15, the thermal displacement 1 between the sampling times is calculated as follows. As illustrated in FIG. 7, when the maximum displacement is _L1a , the machine tool 10
The thermal displacement l during driving is asymptote ₁ to the straight line l = L1a.
Draw 02. Furthermore, after the thermal displacement amount l has reached the maximum displacement amount L _1a (time point t = 8hour 7), the machine tool 10
Is stopped, the thermal displacement l draws an asymptote 104 with respect to the straight line l = 0. Here, asymptote 102 is a _{l = L 1a · {1-} exp (-γt)} ...... (1), asymptote 104 is a _{l = L 1a · exp (-γt} ) ...... (2) , Respectively. Here, γ is a constant unique to the machine tool 10, and the units of t and l are respectively hour and μm.
It is. Therefore, from this equation, the thermal displacement l _1a a minute after the start of driving of the machine tool 10 is given by l _1a = L _1a · {1-exp (−γ · a / 60)}. Also, the thermal displacement l after a minute after the machine tool 10 stops
_-1a is expressed as follows: l _-1a = L _1a · exp (−γ · a / 60) In S15, the thermal displacement 1 during the sampling time is calculated mainly using Expression (1). Further, the following S16
Then, after adding the thermal displacement amount 1 within the holding time described later to calculate the total thermal displacement amount as follows, the above-described S3 (FIG. 4)
Move to.

In this embodiment, the case where the thermal displacement 1 is calculated based on the moving distance during the sampling time (S13 to S13).
S15) It is considered that the thermal displacement l subsequently decreases according to the equation (2). That is, as exemplified by the curve 201 in FIG. 8A, the value l _1a-1 of the thermal displacement amount l _{1a at} the time 1a calculated based on the moving distance from the time 0 to the time 1a is as described above. _L1a-1 = L1a ₁ {1-exp (-γ ・ a / 60)}. Here, _L1a is the maximum displacement calculated at the sampling time of time 1a. Then, the value l _1a-2 of the thermal displacement l _{1a at} the time 2a is calculated from the equation (2) as follows: l _1a-2 = l _1a-1 · exp (−γ · a / 60) Thermal displacement l _{1a at} time 4a
The values l _1a-3 and l _1a-4 are as follows: l _1a-3 = l _1a-1 · exp (−γ · 2a / 60) l _1a-4 = l _1a-1 · exp (−γ · 3a / 60) ). Similarly, if the maximum displacement L _2a is calculated based on the movement distance from time 1a to time 2a,
The corresponding thermal displacement l _2a is shown by curve 202 in FIG.
And the values l _2a-1 , l _2a-2 , and l _{2a-3 at} the times 2a, 3a, and 4a are respectively: l _2a-1 = L _2a · ｛1-exp (−γ · A / 60)｝ l _2a-2 = l _2a-1 · exp (-γ · a / 60) l _2a-3 = l _2a-1 · exp (-γ · 2a / 60) In S16, the total thermal displacement is calculated by adding the values of the thermal displacements l _1a , l _2a ,... Calculated at this time at that time. For example, time 1a, 2
Based on the movement distances between the sampling times of a, 3a, 4a, 5a,..., curves 201, 20 in FIG.
Assuming that the thermal displacement 1 illustrated in 2, 203, 204, 205,... Has been calculated, the total thermal displacement calculated in S16 changes as illustrated by the curve 200 in FIG.

The thermal displacement l calculated at each time is
As described above, the value decreases with the lapse of time.
It is possible to neglect the influence of the thermal displacement 1 over a predetermined time (for example, 120 minutes) after calculation on the total thermal displacement. Therefore, the CPU 72 stores the predetermined time in the ROM as the holding time, and calculates the total thermal displacement by performing the above addition only on the thermal displacement 1 calculated within the holding time. Therefore, the number of thermal displacements l that must be added in the process of S16 is 120
/ A + 1 is suppressed to a natural number or less, and the load related to the calculation process can be reduced. Therefore, it is possible to simplify the software configuration and the like related to the processing and improve the processing speed.

The CPU 72 associates the thermal displacement 1 calculated at each time with the calculated time at the RAM.
74, and the stored contents are stored in the power supply O.
It is also held between the FFs by a backup power supply (not shown). For this reason, the power is once turned off and turned on again.
In step S11, the moving distance during power-off is regarded as 0 (therefore, the thermal displacement 1 is also 0) in step S11, and in step S16,
Then, the total thermal displacement can be calculated by adding the influence of the thermal displacement 1 calculated during the previous power-on period, which has not passed the holding time since the calculation, and calculating the total thermal displacement. .

Returning to FIG. 4, when it is determined in S3 that correction based on the actually measured value is necessary, the flow shifts to S5 to execute the next actually measured value detection process. The case where it is determined in S3 that the correction based on the actually measured value is necessary includes the case where a predetermined time has elapsed from the start of driving of the machine tool 10 and the case where the operator determines the dimensional error of the processed workpiece W by using a caliper or the like. In some cases, measurement is performed, and a dimensional error or the like is input from the operation panel 22 as an actual measurement value of the thermal displacement amount. In the following description, the former case will be described first as an example, and the latter case will be described later.
The predetermined time is a drive time until a sufficiently measurable thermal displacement occurs in the machine tool 10, and is assumed to be a minute (for example, 30 minutes) in the following description.

When the process proceeds to S5 after a minute has elapsed from the start of driving, in the actually measured value detection process in S5, the Z-axis control system 60, the X-axis control system, and the Y-axis control system are driven and The held tool T is brought into contact with the detector 49. CPU72
Is calculated when the drive signal of the Z-axis control system 60 required until the contact signal is received from the detector 49 and the contact is confirmed is calculated, and the thermal displacement is not generated in the machine tool 10. The calculated driving amount is compared with the calculated driving amount. Then, based on the comparison result, the actual measurement value (Z-axis direction) of the thermal displacement amount of the machine tool 10 is detected.

After the detection of the actually measured value, the correction value calculation processing of S7 is executed. In this process, the total amount of thermal displacement calculated in S1 (hereinafter referred to as a calculated value) is compared with the actually measured value detected in S5, and a correction value for the calculated value is calculated. In subsequent S9, based on the correction value calculated in S7, S1
Is changed and stored in a predetermined area of the RAM 74 (parameter change processing).

Here, the processing in S7 and S9 includes a mode in which the difference between the calculated value and the actually measured value is used as a correction value, and a mode in which the ratio between the two is used as a correction value. A desired form can be selected by setting the panel 22. In FIGS. 9A and 9B, the change in the calculated value of the thermal displacement amount 1 when the correction based on the actually measured value is not performed is represented by a solid line, and is represented by a time t0 (a minute after the start of driving of the machine tool 10). The measured value detected by is indicated by ■.

When utilizing the difference between the calculated value and the actually measured value,
As illustrated in FIG. 9A, a difference Δl obtained by subtracting the calculated value from the actually measured value is calculated as a correction value (S7), and the above Δl is added to the equations (1) and (2) used in S15, respectively. (S9). By executing the processing of S5 to S9 and shifting to S1 again, the total thermal displacement calculated in the processing of S1 can be corrected as shown by the dotted line in FIG.

When using the ratio between the calculated value and the actually measured value,
As illustrated in FIG. 9B, the measured value l2 and the calculated value l1
Is calculated as the correction value (S7).
In Equations (1) and (2) used in Equation 5,
The processing of multiplying by l1 is performed (S9). By executing the processing of S5 to S9 and shifting to S1 again, the total thermal displacement calculated in the processing of S1 can be corrected as shown by the dotted line in FIG. 9B. The case where the difference between the calculated value and the measured value is used as the correction value and the case where the ratio between the two is used have the following advantages, respectively. You can choose. As described below, it is advantageous to use the difference when the absolute value of the calculated value and the measured value is small, and to use the ratio when the absolute value of both is large. Therefore, when the absolute value of the calculated value or the actual measurement value is small, a mode in which the difference between the two is used as the correction value is automatically selected, and when the absolute value is large, a mode in which the ratio of the two is used as the correction value is automatically selected. May be configured.
Furthermore, other forms that are not differences or ratios may be employed.

If the absolute values of the calculated value and the actually measured value are extremely small, a slight measurement error will be reflected in the value of the ratio between the two. For this reason, when the ratio between the calculated value and the actually measured value is calculated as a correction value, and the value is multiplied or divided by the total thermal displacement calculated in S1, the total thermal displacement that is large in S1 except at time t0 When the displacement amount is calculated, there is a possibility that a measurement error or the like is multiplied or divided by the calculated value and largely reflected. On the other hand, if the difference between the calculated value and the actually measured value is used as the correction value as shown in FIG. 9A, the same amount is always obtained regardless of the absolute value of the total thermal displacement calculated in S1. Corrections can be made. Therefore, in this case, even when the absolute value of the calculated value serving as the basis for calculating the correction value and the actual measurement value is extremely small, it is possible to calculate the accurate amount of thermal displacement.

When the absolute value of the calculated value and the measured value is extremely large, the absolute value of the difference between the two tends to increase. For this reason, when the difference between the calculated value and the actually measured value is used as a correction value, it is difficult to use the same correction value when a small total thermal displacement is calculated in S1 at a time other than the time t0. . For example, the corrected thermal displacement may be negative. On the other hand, if the ratio between the calculated value and the actually measured value is used as a correction value as shown in FIG. 9B, when a small total thermal displacement is calculated in S1, a small correction corresponding thereto is performed. It can be carried out. Therefore, in this case, even when the absolute value of the calculated value serving as the basis for calculating the correction value and the measured value is extremely large, the accurate thermal displacement amount can be calculated.

When an actual measured value of the thermal displacement amount such as a dimensional error is input from the operation panel 22 and an affirmative judgment is made in S3, the input value is read in S5 (actual measured value detection processing). Then, in subsequent S7 and S9, the same processing as described above is performed between the read actual measurement value and the calculated value.

As described above, the microcomputer section 70 of the present embodiment detects the actual measured value of the thermal displacement of the machine tool 10 (S5), and calculates the total heat calculated in the thermal displacement calculating process (S1). The displacement is corrected based on the measured value (S7,
S9). For this reason, an accurate amount of thermal displacement can be calculated according to the characteristics of each machine tool and the use environment.

Further, in this embodiment, instead of using the actual measured value of the thermal displacement as it is, a correction value is calculated from the measured value, and the total thermal displacement calculated in S1 is calculated using the corrected value. Has been corrected. For this reason, if the actual measurement value is detected once after a predetermined time (for example, after a minute) from the start of driving of the machine tool 10, a sufficiently accurate thermal displacement amount is thereafter calculated using the correction value calculated from the actual measurement value. Can be calculated.
That is, when the actual measurement value of the thermal displacement amount is detected by using the detector 49 as in the present embodiment, the processing on the work W must be temporarily interrupted at the time of the detection. Is performed only once, and the working efficiency of the machine tool 10 can be improved satisfactorily. Further, in this embodiment, every time the machine tool 10 is started, the correction based on the actually measured value can be automatically performed.
A more accurate thermal displacement can be calculated more easily according to the change of the characteristics and the use environment.

In the above embodiment, the main shaft 28 is used as the machining means, and the ball screw mechanism 36 and the Z-axis control system 60, X
The axis control system and the Y-axis control system are the driving means and the processing means moving means, the detector 49 is the processing means detecting means, the RAM 74 is a predetermined storage means, the CPU 72 is the driving state detecting means, the displacement calculating means, and the actually measured value. It corresponds to a detection unit, a correction value calculation unit, a correction value storage unit, and a displacement amount correction unit.
6 is the displacement amount calculating means, S5 is the actually measured value detecting means, S7
Is processing corresponding to the correction value calculation means, and S9 is processing corresponding to the correction value storage means and the displacement amount correction means.

Next, a second embodiment of the present invention will be described. FIG. 10 is a block diagram illustrating a configuration of a control system of the machine tool 10 according to the second embodiment. Note that the machine tool 1 of the present embodiment
The mechanical configuration of the control system 0 is the same as that of the first embodiment, and the configuration of the control system differs in the following points. That is, as shown in FIG. 10, the microcomputer unit 70 includes an interface (I / F) 78 in addition to the above-described configuration, and is connected to the personal computer 80 via the interface 78. The personal computer 80 includes a one-chip type CPU 82 having a ROM for storing a control program and the like, an input / output port, and the like.
It comprises an M84, a clock 86, an interface (I / F) 88 connected to the microcomputer unit 70, and the like, and is configured as a known microcomputer. Further, a keyboard 91 and a CRT 92 are also connected to the personal computer 80.

In this control system, the microcomputer unit 70 controls the machine tool 10 based on a machining program, and the microcomputer unit 70 sends the computer 80 a necessary amount of total thermal displacement, such as the travel distance of the spindle 28. Data, detector 4
9, the actual measured value of the amount of thermal displacement detected through the operation panel 22
The actual measured value and the like of the input thermal displacement are transmitted via.
Also, the personal computer 80 executes the following processing to
Is calculated, and the calculated total thermal displacement is transmitted to the microcomputer unit 70. Then, the microcomputer unit 7
0 executes the machining program while performing correction based on the transmitted total thermal displacement.

The personal computer 80 (strictly speaking, the CPU 82)
Almost the same processing as that of FIG. 4 described above is executed.
The thermal displacement amount calculation process 1 and the actually measured value detection process in S5 are executed by transmitting and receiving the data, the drive command, and the like to and from the microcomputer unit 70, instead of controlling the Z-axis control system 60 and the like. For example, the thermal displacement amount calculation processing in S1 is as shown in FIG. Note that this thermal displacement amount calculation processing is almost the same as the thermal displacement amount calculation processing shown in FIG. 5, and therefore only different parts will be described.

In S13a executed instead of S13,
The CPU 82 does not calculate the moving distance by itself, but reads the moving distance transmitted from the microcomputer unit 70. Also,
In S16a executed in place of S16, after calculating the total thermal displacement in the same manner as in S16, the total thermal displacement is transmitted to the microcomputer unit 70. Other processes are the same as those in the first embodiment, and the detailed description is omitted by using the reference numerals used in FIG. 5 as they are. The personal computer 80 also executes the actual measurement value detection process in S5 by the same transmission and reception.

In the present embodiment thus configured, the first
Functions and effects substantially similar to those of the embodiment are obtained. In this embodiment, the CPU 82 also calculates the thermal displacement l calculated at each time.
Is stored in the table of the RAM 84 in association with the calculated time, but the stored content does not necessarily need to be backed up. This means that the power of the machine tool 10 is turned off.
If the power of the personal computer 80 is kept on even after F,
This is because the stored contents do not disappear. In the present embodiment, the machine tool 1 connected via the interface 88
If 0 is changed, the total thermal displacement for a plurality of machine tools 10 can be calculated by one personal computer 80.

As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the gist of the present invention. . For example, in the above embodiment, the spindle 28
Of the machine tool 10 in the Z-axis direction is calculated from the Z-axis moving distance.
Thermal displacement occurs in 8 itself. Therefore, the rotation amount of the spindle motor 30 is calculated as a moving distance, and Z is calculated from the moving distance.
The axial thermal displacement may be calculated. In addition, the aforementioned total thermal displacement calculated by the processing of FIG. 5 or FIG.
The thermal displacement in the Z-axis direction of the entire machine tool 10 may be calculated by adding the thermal displacement calculated from the rotation of the main shaft 28. In this case, the amount of thermal displacement in the Z-axis direction can be calculated more accurately. Further, the present invention may be applied to a mechanism for moving the work W.

Further, the thermal displacement of the machine tool 10 is affected by various conditions, such as the moving distance of the main shaft 28 and the driving time. For example, when the air temperature is relatively low in the morning or the like, the temperature rise of the machine tool 10 becomes gentle, and the error between the calculated total thermal displacement and the actual thermal displacement may not be negligible. Thus, for example, S16 in FIG. 5 may be changed as shown in FIG. 12 so that various adjustments can be made.

That is, in S61, the total thermal displacement is calculated as in S16. In subsequent S62, the CPU 72
It is determined whether it is necessary to adjust the total thermal displacement calculated in S61. This necessity determination is made as follows: (1) an adjustment value is input via the operation panel 22; (2) an adjustment value is set corresponding to the time; and (3) an adjustment value corresponding to the environmental temperature. Is required depending on whether or not a condition such as a need to be used is satisfied. If the condition is satisfied, adjustment is necessary (S6
2: YES), and an adjustment value is added to or subtracted from the total thermal displacement amount in S63 for adjustment. On the other hand, no adjustment is required (S6
(2: NO), the process proceeds to S3 (FIG. 4) while maintaining the total thermal displacement calculated in S61.

In this case, for example, if the adjustment value is determined in accordance with the time, according to the time period of the day (morning, noon, night, etc.),
An error between the calculated total thermal displacement and the actual thermal displacement can be automatically and better eliminated. Therefore, an accurate total thermal displacement amount can always be calculated regardless of the time. If the adjustment value is determined according to the environmental temperature of the machine tool 10, the calculated total thermal displacement and the actual thermal displacement are calculated according to the temperature at the place where the machine tool 10 is installed, that is, the environmental temperature. Can be automatically and better eliminated. Therefore, it is possible to always calculate the accurate total thermal displacement regardless of the environmental temperature. Note that S1 in FIG.
5, a similar effect is obtained even if S15 or S16a in FIG. 11 is changed in this way.

In each of the above embodiments, the tool T is brought into contact with the detector 49 to detect that the main shaft 28 has moved to a predetermined position, and based on the drive amount of the Z-axis control system 60 at that time, the heat is detected. Although the actual measured value of the displacement amount is detected, various other configurations can be adopted as the actual measured value detecting means. For example, the main shaft 28 can be detected by the detector 4 without using the tool T.
9 may be directly contacted, or only one of the reading of the input value from the operation panel 22 or the detection of the actually measured value by the detector 49 may be performed. An actual measured value of the displacement may be detected.
However, if the configuration using the detector 49 of the above embodiment is adopted, a simple configuration in which the detector 49 is simply added,
An accurate measured value of the thermal displacement of the machine tool 10 can be automatically and easily detected. Therefore, the configuration of the apparatus can be simplified, the manufacturing cost can be reduced, and the parameters can be calculated more accurately and easily.

Further, there are various other possible timings for shifting to the processing of S5 to S9 and performing the actual measurement of the thermal displacement amount by the detector 49. For example, the shift may be repeated every predetermined time, or the shift may be made when the operation panel 22 is operated according to a predetermined procedure, and the actual measurement by the detector 49 may be performed. Various forms of the thermal displacement amount calculation process are conceivable. For example, the thermal displacement amount may be calculated by a process that does not use the maximum displacement amount L.

Further, in each of the above embodiments, a program for executing the processing of FIG. 4, FIG. 5, FIG. 11, or FIG. 12 is stored in the ROM of the CPU 72 or 82. Discs and CD-Rs
Needless to say, it may be stored in a storage medium such as OM. In this case, an arbitrary control means such as a general computer can execute the above processing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a detector of a machine tool according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of a control system of the machine tool according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating a configuration of a pitch error correction table of the machine tool.

FIG. 4 is a flowchart illustrating a main routine of a process executed by a CPU of the machine tool.

FIG. 5 is a flowchart illustrating a thermal displacement amount calculation process in the process.

FIG. 6 is an explanatory diagram showing a configuration of a map used for calculating a maximum displacement amount.

FIG. 7 is an explanatory diagram exemplifying a temporal change of a thermal displacement amount corresponding to a maximum displacement amount.

FIG. 8 is an explanatory diagram illustrating a process of calculating a total thermal displacement amount from a thermal displacement amount.

FIG. 9 is an explanatory diagram exemplifying correction of a thermal displacement amount based on an actually measured value.

FIG. 10 is a block diagram illustrating a configuration of a control system of a machine tool according to a second embodiment.

FIG. 11 is a flowchart showing a thermal displacement amount calculation process executed by a personal computer connected to the machine tool.

FIG. 12 is a flowchart illustrating still another form of the thermal displacement amount calculation process.

FIG. 13 is an explanatory diagram illustrating a configuration of a machine tool according to an embodiment and a conventional example.

FIG. 14 is an explanatory diagram illustrating a configuration of a machine tool according to an embodiment and a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Machine tool 14 ... Table 16 ... ATC magazine 20 ... Main body 28 ... Spindle 30 ... Spindle motor 36 ... Ball screw mechanism 38 ... Z-axis motor 49 ... Detector 60 ... Z-axis control system 70 ... Microcomputer part 72, 82 ... CPU 7
4, 84 RAM 76, 86 Clock 80 PC

Claims (9)

(57) [Claims] 1. A machine tool having machining means for machining a workpiece and driving means for changing a relative position between the machining means and the workpiece, wherein a thermal displacement amount of the machine tool is provided. A drive state detection means for detecting a drive state of the machine tool, and a thermal displacement amount of the machine tool based on the drive state detected by the drive state detection means. A displacement amount calculating means for calculating the actual displacement value of the machine tool, an actual measurement value detecting means for detecting an actual measurement value of the thermal displacement amount of the machine tool, a thermal displacement amount calculated by the displacement amount calculating means, Compare with the actual value of thermal displacement,
Correction value calculating means for calculating a correction value for the thermal displacement amount calculated by the displacement amount calculating means, correction value storing means for storing the correction value calculated by the correction value calculating means, and stored in the correction value storing means And a displacement correcting means for correcting the thermal displacement calculated by the displacement calculating means using the corrected value. 2. The correction value calculation means calculates a ratio between the thermal displacement calculated by the displacement calculation means and an actual measured value of the thermal displacement detected by the measured value detection means as a correction value. 2. The thermal displacement calculating device for a machine tool according to claim 1, wherein the displacement correcting means corrects the thermal displacement calculated by the displacement calculating means by multiplying or dividing the correction value. . 3. The correction value calculation means calculates a difference between the thermal displacement calculated by the displacement calculation means and an actual measured value of the thermal displacement detected by the measured value detection means as a correction value. 2. The thermal displacement calculating device for a machine tool according to claim 1, wherein the displacement correcting means corrects the thermal displacement calculated by the displacement calculating means by adding or subtracting the correction value. . 4. A processing means detecting means for detecting the processing means when the processing means relatively moves to a predetermined position with respect to the workpiece, and controlling the driving means, And a processing means moving means for relatively moving the processing means to a position detected by the processing means detection means. The processing means moving means relatively moves the processing means to a position detected by the processing means detection means. The driving amount of the driving means required to perform the driving is compared with the driving amount required when no thermal displacement occurs in the machine tool, and the actual measurement value is detected based on the comparison result. The apparatus for calculating a thermal displacement of a machine tool according to any one of claims 1 to 3, wherein: 5. The measured value detecting means detects the measured value a predetermined time after the start of driving of the machine tool, and each time the correction value calculating means calculates the correction value,
The apparatus according to claim 4, wherein the correction value stored in the correction value storage means is updated. 6. The thermal displacement amount of the machine tool by adding or subtracting an adjustment value determined corresponding to the condition affecting the thermal displacement amount to or from the thermal displacement amount corrected by the displacement amount correcting means. The thermal displacement calculating device for a machine tool according to any one of claims 1 to 5, further comprising a displacement adjusting means. 7. The machine tool according to claim 6, wherein the adjustment value is determined according to time, and the displacement amount adjusting means selects and uses the adjustment value based on time. Thermal displacement calculator. 8. The adjustment value is determined according to the environmental temperature of the machine tool, and the displacement adjusting means selects and uses the adjustment value based on the environmental temperature. The apparatus for calculating a thermal displacement of a machine tool according to claim 6. 9. A machine tool provided with machining means for machining a workpiece and driving means for changing a relative position between the machining means and the workpiece, wherein A storage medium storing a computer program for calculating a thermal displacement amount, wherein a measured value detection process for detecting a measured value of a thermal displacement amount of a machine tool, and a drive state detection process for detecting a drive state of the machine tool A displacement amount calculating process for calculating a thermal displacement amount of the machine tool based on the driving state detected by the driving state detecting process; a thermal displacement amount calculated by the displacement amount calculating process; A correction value calculation process for comparing a measured value of the thermal displacement amount detected by the process and calculating a correction value for the thermal displacement amount calculated by the displacement amount calculation process; Correction value storing processing for storing the corrected correction value in predetermined storage means, and displacement amount correction for correcting the thermal displacement amount calculated by the displacement amount calculation processing using the correction value stored in the predetermined storage means. A storage medium storing a process and a computer program for executing the following.