JP2003245844A - Simple method of correcting heat displacement in machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method of correcting heat displacement in a machine tool by representing heat displacement occurring in the machine tool by a simple exothermic function and a cooling function and measuring the heat displacement beforehand to make a positional correction. <P>SOLUTION: This simple method of correcting heat displacement in a machine tool performs a main position correcting process and a cut processing process by a control means (5). The main position correcting process constantly corrects an average rotational speed (Vs) of a main spindle body (1a), respective average feed speeds (Vx, Vy and Vz) of moving members (2c, 3c and 4c) moving on feeding members (2b, 3b and 4b) in respective three-dimensional axial directions and the operating time thereof (t), and the position of the main spindle of the front end face (1b) thereof due to exothermic and heat-cooling displacement caused by the environmental condition exposed to such operating heat. The method is characterized by performing a pre- treatment process for the correction of heat displacement by the use of a heat- displacement measuring means in order to predetermine an exothermic function (t) and a cooling function g (t) beforehand which represent a displacement quantity δ, respectively, to be used for the main position correcting process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple thermal displacement correction method for a machine tool, in which the thermal displacement of a machine tool is represented by a simple heat generation function and a cooling function, the thermal displacement is measured in advance and the position is corrected.

[0002]

2. Description of the Related Art There are various conventional thermal displacement compensation methods for machine tools. For example, there is Japanese Patent No. 3154946 entitled "Compensation Method for Thermal Displacement of Machine Tools". In a machine tool to be used, an approximation formula for obtaining the correction amount for thermal displacement from the average movement speed, movement frequency, and movement position of the feed axis, and an approximation for obtaining the position correction amount for the command position from the correction amount obtained by the approximation formula The equation is stored in advance in the numerical controller, the position of the feed axis is monitored, the average movement speed and movement frequency of the feed axis are obtained from the monitored feed axis position, and the command position for the feed axis is calculated from the above approximate equation. There is a thermal displacement correction method in which the position correction amount is calculated and the commanded position is corrected by the position correction amount and output.

[0003]

In the thermal displacement correction method for a machine tool of the prior art, as an approximate expression, for example, as shown in "paragraph 0026", the amount of heat generation displacement per unit time is
Qn is represented by Qn = A ・ [f (Bn)] ^a・ Cn ^b and exponentiation coefficients: a, b. It is complicated and easy to approximate the approximate expression with measured values. It was difficult and time-consuming.

In the conventional thermal displacement correction method for machine tools, the thermal displacement correction method is, for example, in the case of the movement axis correction amount, as shown in "paragraph 0026".
n is corrected by adding δn = δn-1 + Qn -qn and the differential form. In such differential form addition, an error is added and the error in the correction amount may be large in the position calculation. There was a problem.

In the above-mentioned conventional thermal displacement correction method for machine tools, the thermal displacement measuring method is, for example, in the case of measuring the thermal displacement of the Z-axis, as shown in "paragraph 0019", the Z-axis is -50 mm,- 1
Displacement measuring instruments S1, S2, S3 that measure displacement at 50 mm and -300 mm positions
Is measured at three points using the displacement of the Z-axis stroke (Fz) at one end and the freely displaceable free end (Ez) at the other end. However, there are problems in that there are many measurement points, the measurement takes time, and the analysis takes time accordingly.

[0006]

In order to solve the above problems, a simple thermal displacement correction method for a machine tool of the present invention uses a heat generation function f (t) representing each displacement amount δ. Ultimate displacement δm
Is a first-order lag equation that reaches saturation with time t at a heat generation time constant τh, and the amount of displacement δm reached is proportional to the average velocity V including the movement frequency, which has a corresponding proportionality coefficient K On the other hand, each cooling function g (t) is defined as an exponential decay formula that decays exponentially from the initial displacement δm with a cooling time constant τc at time t when the corresponding operation is stopped. Characterize.

According to the simple thermal displacement correction method for a machine tool of the present invention, the heat generation function and the cooling function are easily expressed by a first-order lag equation and an exponential decay equation which are respectively defined by simple two constants, and therefore the displacement amount calculating means In the analytical solution of the function,
It is characterized in that each displacement amount δ is calculated.

According to the simple thermal displacement correction method for a machine tool of the present invention, in the thermal displacement correction pretreatment step, the thermal displacement measuring means of each axis has a freely movable displacement end at one end of the stroke (ST).
The feature is that the displacement amount δ representing the maximum displacement corresponding to (E) is measured.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A simple thermal displacement correction method for a machine tool according to claim 1 of the present invention is a rotary average speed (Vs) of a main spindle body (1a), three-dimensional (x, y, z axes). The feed average speed (Vx, Vy, Vz) of the moving member (2c, 3c, 4c) that moves on the feeding member (2b, 3b, 4b) consisting of axial ball screws, etc., and its operating time (t), A position correction main process for constantly correcting the spindle position of the spindle front end face (1b) due to heat and cooling heat displacement caused by operating thermal environment conditions is performed by the control means (5) along with the cutting process. A simple thermal displacement correction method for predetermining a heat generation function f (t) and a cooling function g (t) respectively representing displacement amounts δ (δx, δy, δz, δs) used in the position correction main process. Therefore, the thermal displacement correction pretreatment process is performed by using the thermal displacement measuring means, and the main axis (s) of the machine tool
The z-axis is used, and each exothermic function f (t) is a first-order lag equation in which the ultimate displacement δm reaches saturation with time t at the exothermic time constant τh, and the ultimate displacement δm is the corresponding proportional coefficient. It has a certain characteristic coefficient K (kx, ky, kz, ks) and is proportional to the average velocity V (Vx, Vy, Vz, Vs) including the moving frequency, while each cooling function g (t) is , When the corresponding operation is stopped, the initial displacement amount δm exponentially decays with cooling time constant τc with time t, and the exponential decay formula is used, and the thermal displacement measuring means of the spindle is The displacement δs in the z-axis direction is measured by a position measuring means (10) such as a pick tester, while z
The thermal displacement measuring means of the shaft determines the stroke (STz) of the rotatable feed member, and the displacement fixed end (Fz) at one end that fixes the displacement in the z-axis direction and the freely displaceable displacement at the other end. Edge (E
z), the z-axis carriage (4
a) At the end, measure the displacement amount δz by the position measuring means,
Then, the thermal displacement measuring means for the x and y axes measure the amount of displacement (δx, δy) at the displacement free end (Ex, Ey) of each stroke (STx, STy) in the vicinity of the corresponding side circumferential corner of the spindle front end face. ) Are respectively measured by the position measuring means, and in the position correction main process,
The correction amount C of the spindle position of the spindle front end face by each displacement δ (δx, δy, δz, δs) uses the gradient correction process (S51), and the z-axis correction amount Cz is the displacement amount δz. The stroke (STz) is proportionally distributed using a linear gradient, and the displacement amount δs is uniformly added to secure the correction, while the x and y axis correction amounts Cx, Cy
Is an operation for proportionally securing each displacement amount (δx, δy) between the corresponding strokes (STx, STy) by using a linear gradient, and in particular performing the thermal displacement correction pretreatment step. The thermal environment is characterized in that the spindle is unloaded in the ambient atmosphere temperature.

In a simple thermal displacement correction method for a machine tool according to claim 2 of the present invention, the operating thermal environmental conditions for performing the thermal displacement correction pretreatment step are the main spindle body (1a), cutting tool (1c), and workpiece.
(7) A simple thermal displacement correction method for a machine tool according to claim 1, characterized in that a predetermined amount of coolant liquid for cooling the vicinity of the machined part, including (7), is circulated and equipped with a coolant device.

In the simple thermal displacement correction method for a machine tool according to claim 3 of the present invention, the operating thermal environment condition for performing the thermal displacement correction pretreatment process is such that the spindle body (1a) and the cutting tool (1c) have a predetermined amount. The load condition of the machine tool, and the magnitude of the load can be measured by the load of the spindle motor (1d) or the like.

In the thermal displacement correction pretreatment step of the simple thermal displacement correction method for machine tools of the present invention, the stroke (ST) used for the thermal displacement measuring means of each axis is determined, and the displacement in each axial direction is rotatably fixed. The fixed displacement end (F) at one end can be secured by fixing the ring member to the feed member and sandwiching the ring member with the bearing member.

In the thermal displacement correction preprocessing step of the simple thermal displacement correction method for machine tools of the present invention, the heat generation function is a first-order lag equation, f (t) = δm [1-exp (-t / τh )], Where it is easily determined by two constants, the time constant τh and the ultimate displacement δm, and it is demonstrated that the ultimate displacement δm is almost proportional to the average velocity (V). f (t) is generally expressed as f (t) = K ・ V ・ [1-exp (-t / τh)] using two constants, characteristic coefficient K and time constant τh. Characterize.

In the thermal displacement correction pretreatment step of the simple thermal displacement correction method for machine tools of the present invention, the cooling function is an exponential damping formula, g (t) = δm · exp (-t / τc), where And is easily represented by two constants, a time constant τc and an initial displacement δm.

In the simple thermal displacement correction method for a machine tool according to the present invention, the position correction main process starts as a program when the power of the machine tool is turned on (S0). First, in the initial setting process (S1), each displacement amount δ is calculated. Displacement correction process for selecting and setting the sampling time (Tm) that is calculated and stored in the control memory (M31) of the control means and displayed at a predetermined sampling time (Tm) interval, and position correction of each axis. The correction time (Tc> Tm) as the time interval for executing (S5) is selected and set. Next, when Δt = Tm is reached in the displacement amount sampling time reaching process (S2), the displacement amount sampling process (S2) In the previous sampling time: t _{i-1 ,} each displacement amount δ _i-1 was read from the control memory (M31) between the time intervals Tm = t _i -t _i-1 using the displacement calculation means. average speed using the data set DS (V _i) value containing the altered movement frequency, heat generation state It determines whether line or cooled state transition, current sampling time: each displacement amount [delta] _i of t _i is calculated secured, and the displacement amount [delta]
_i is the data set DS (δ), and the control memory (M31)
When it reaches Δt = Tc in the displacement amount correction time reaching step (S4), it is displayed in the displacement amount correction time reaching step (S4). The data set DS (δ) is read from the control memory (M31), and in the gradient correction step (S51), the correction amount calculation means is used to calculate and secure the correction amount C for each axis, and the correction memory (M51 It is also possible to read the correction amount C of the correction memory (M51) according to the movement command from the machining control process (W1) and correct the position of each axis moving device via the interface (W2). .

In the simple thermal displacement correction method for a machine tool of the present invention, the initial setting step (S1) of the main position correction step measures the stop time of the machine tool before the power is turned on (S0), and the last final sampling time is measured. It is also possible to include a step of calculating the elapsed time until the power is turned on this time.

The simple thermal displacement correction method for a machine tool according to the present invention uses a first-order lag equation and an exponential damping equation which are respectively determined by simple two constants as the heat generation function and the cooling function in the thermal displacement correction pretreatment process. However, surprisingly, in the main position correction process, the maximum displacement amount is suppressed to about 10 μm or less during each axis stroke.

In the thermal displacement correction pretreatment step of the simple thermal displacement correction method for machine tools of the present invention, the heat generation function is the time constant τ
Since it is expressed by two constants, h and ultimate displacement δm, the ultimate displacement δm that reaches equilibrium is easily determined, and the time constant τh is ½ of the ultimate displacement δm δ1 = δm / 2 and secure the time t1 corresponding to δ1, τh = t1 / In2 = t1 / 0.
By using 693, the time constant τh can be easily obtained.

In the thermal displacement correction pretreatment step of the simple thermal displacement correction method for machine tools of the present invention, the cooling function has a time constant τ.
Since it is expressed by two constants, c and initial displacement δm, the time constant τc is such that 1/2 of the initial displacement δm is δ1 = δm / 2, and the time t1 corresponding to δ1 is secured. = t1 / In2 = t1 / 0.
By using 693, the time constant τc can be easily obtained.

In the thermal displacement correction pretreatment process of the simple thermal displacement correction method for machine tools of the present invention, the thermal displacement measuring means of each axis (x, y, z) is a displacement capable of displacing one end of the stroke (ST). Since the displacement amount δ that represents the maximum displacement corresponding to the free end (E) is measured, the displacement amount is large, the relative error is small, and the measurement is easy, and the measurement and analysis do not take time. .

In the position correction main process of the simple thermal displacement correction method for machine tools of the present invention, the gradient correction process (S51) is used, z
The correction amount Cz of the axis is proportional to the displacement amount δz by using the linear gradient between the strokes (STz), and the displacement amount δs is uniformly added to secure the correction amount. On the other hand, the correction amount of the x and y axes is corrected. Cx and Cy are
Each displacement amount (δx, δy) is calculated by the corresponding stroke.
Since a linear gradient is proportionally distributed between (STx, STy) to secure the correction, it is possible to correct between each stroke, and the correction amount C is calculated linearly. The value that stores the quantity C in the correction memory (M51) has only the effect of storing the correction values at both ends of each axis stroke.

In the position correction main process of the simple thermal displacement correction method for a machine tool of the present invention, the heat generation function and the cooling function are easily expressed by the first-order lag equation and exponential decay equation which are determined by simple two constants, respectively. , Displacement sampling process (S2)
The displacement amount calculation means easily calculates the displacement amount δ _i at the current sampling time: t _i by the analytical solution method of the function, and differential addition is not performed. Have.

A simple thermal displacement correction method for a machine tool of the present invention is a machine tool equipped with a coolant device, and
It can be used in response to various operating thermal environment conditions such as machine tools where the cutting tool is under a certain amount of load.

The simple thermal displacement correction method for a machine tool according to the present invention is applied to a machine tool having a moving device on each one-dimensional or two-dimensional axis, and the simple thermal displacement correction method is applied to each corresponding equipment axis. It should be possible.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings of the embodiment of the present invention, FIG.
(A) is a schematic explanatory block diagram showing a thermal displacement measuring means used in a thermal displacement correction pretreatment step in a simple thermal displacement correcting method for a machine tool showing an embodiment of the present invention, and (B).
Shows the relationship between the displacement amount δ, the displacement fixed end F, and the displacement free end E on the coordinate axes of the schematic explanatory diagram. FIG. 2 shows the Z-axis heat displacement measurement in the simple thermal displacement correction method for a machine tool, and FIG. 3 shows the Z-axis cooling displacement measurement result. Fig. 4 shows (A) in a simple thermal displacement correction method for machine tools.
Is the X-axis heat displacement measurement amount, and (B) is the Z-axis heat displacement measurement amount, and in FIG. 5, (A) is the main spindle heat displacement measurement amount, and (B) is the cooling displacement measurement amount. FIG. 6 shows a position correction main process in a simple thermal displacement correction method for a machine tool. FIG. 7 is an explanatory view of a schematic displacement amount calculating means used in the displacement amount sampling process of the position correction main process, and FIG. 8 shows a gradient correction process of the position correction main process. (A) shows an X-axis correction amount: Cx, (B) is a schematic correction amount calculation means explanatory diagram of Y-axis correction amount: Cy, and (C) is Z-axis correction amount: Cz. Figure 9 shows the results of comparative displacement measurement with and without compensation in the simple thermal displacement compensation method for machine tools.
(A) is a Y-axis measurement value, and (B) is a Z-axis measurement value.

An embodiment of the present invention will be described below. A simple thermal displacement correction method for a machine tool according to claim 1 is as follows.
As shown in Fig. 3, the rotation average speed (Vs) of the spindle body (1a), 3D
(x, y, z axes) Feeding member (2
(b, 3b, 4b) Moving average speed (V) of moving member (2c, 3c, 4c)
x, Vy, Vz) and its operating time (t), and the spindle front end face (1
This is a simple thermal displacement correction method for a machine tool that performs the position correction main process for constantly correcting the spindle position in b) by the control means (5) together with the cutting process. To predetermine the heat generation function f (t) and the cooling function g (t) that represent the quantities δ (δx, δy, δz, δs), perform the thermal displacement correction pretreatment step using the thermal displacement measuring means. In the machine tool, the main axis (s) is the z-axis, and each heat generation function f (t) has an ultimate displacement δm of a heat generation time constant τh
Is a first-order lag equation that reaches saturation with time t, and the ultimate displacement δm is the characteristic coefficient K (k
x, ky, kz, ks) and average velocity V (Vx, Vy, V
z, Vs), while each cooling function g (t)
Is an exponential damping formula that decays exponentially from the initial displacement δm with a cooling time constant τc at time t when the corresponding operation is stopped, and the thermal displacement measuring means of the spindle is the front end face of the spindle. The displacement amount δs in the z-axis direction is measured by the position measuring means (10) such as a pick tester, while the z-axis thermal displacement measuring means determines the stroke (STz) of the rotatable feed member (4b). , the displacement fixed end (Fz) at one end where the displacement in the z-axis direction is fixed, and the free displacement end (Ez) at the other end
, The z-axis movable table (4a) corresponding to the free end of displacement (Ez)
At the end, the displacement amount δz is measured by the position measuring means, and the x and y axis thermal displacement measuring means measure the stroke displacement (STx, STy) in the vicinity of the corresponding side circumferential corner of the spindle front end face. At the displacement free end (Ex, Ey), the displacement amount (δx, δy) is measured by the position measuring means, and in the position correction main process, the displacement amount δ (δx, δy, δz, δs) As shown in Fig. 8, the correction amount C of the spindle position on the front end face of the spindle is
51), the correction amount Cz of the z-axis is proportionally distributed by using the linear gradient between the strokes (STz) and the displacement amount δz is uniformly added to secure the correction amount. On the other hand, the correction amounts Cx and Cy on the x and y axes are respectively the displacement amounts (δx, δy)
The linear gradient is proportionally distributed between the corresponding strokes (STx, STy) to ensure the correction, and especially the operating thermal environment condition for performing the thermal displacement correction pretreatment step is It is characterized by being a load.

In the simple thermal displacement correction method for machine tools according to claim 1 of the embodiment of the present invention, the result of the Z-axis heat displacement measurement is shown in FIG. ) Feed average speed: Vz = 10m / min, Stroke length: STz = 500mm While performing reciprocal movement, the displacement free end (Ez)
At the end of the z-axis moving table (4a) corresponding to, the increase of the displacement amount δz was measured by the position measuring means (10) as a function of the elapsed time (t). The exothermic function of δz = fz (t) is fz (t) = δmz ・ [1- e
xp (-t / τh _z )], the time constant τh of the exothermic function is such that the measurement points are connected by a smooth curve and 1/2 of the displacement δm reached is δ
Set 1 = δm / 2, secure time t1 corresponding to δ1, and set τh = t1
The time constant τh can be easily obtained by /In2=t1/0.693. A pick tester is used as the position measuring means, and the displacement amount δz is accurately measured by a contact (pick): 10 μ
Measured in m / scale. Further, the temperature of the feed member (4b) corresponding to the reached displacement amount δm is measured by the contact type thermometer (11) (thermocouple digital thermometer: 0.1 ° C decomposition display temperature) and the free end of displacement (Ez) is measured. Inside: Monitored at about 100 mm, temperature change was about 14 ℃.

In the simple thermal displacement correction method for machine tools according to claim 1 of the embodiment of the present invention, the result of the Z-axis cooling displacement amount measurement is, as shown in FIG. After reaching the amount δm, the reciprocating feed operation of the moving member (4c) is stopped, and the displacement amount δm is set as the initial displacement amount at the end of the z-axis moving base (4a) corresponding to the free end (Ez) of displacement. The damping of the displacement amount δz was measured by the position measuring means (10) as a function of the elapsed time (t). The cooling function of δz = gz (t) is gz
(t) = δmz · exp (-t / τc _z ), and the time constant τc of the cooling function is such that the measurement points are connected by a smooth curve and the initial displacement δ
One half of m is δ1 = δm / 2, and the time t1 corresponding to δ1 is secured, and τc = t1 / In2 = t1 / 0.693 makes it easy to obtain the time constant τc.
Can be asked.

In the simple thermal displacement correction method for a machine tool according to claim 1 of the embodiment of the present invention, the average velocity V (= Vx, Vy, Vz, Vs as various measurement conditions obtained in this way is obtained. )
For each exothermic function f (t) and cooling function g (t), the respective characteristic coefficient K (= kx, ky, kz, ks) and time constant τ
Examples of measurement results of (= τh, τc) are shown in Figs. 4 and 5. As can be seen from these measurement results, especially the exothermic function f (t)
, The corresponding average velocity for a particular axis
Even if (V) is changed, the time constant τ agrees within the error e = 10%, and the characteristic coefficient (k) also agrees within the error e = 14%. Therefore, the ultimate displacement δm is It was proved that it is almost proportional to the average speed (V). Therefore, the exothermic function f (t) can be generally expressed as f (t) = K.V. [1-exp (-t / .tau.h)].

In the simple thermal displacement correction method for a machine tool according to claim 1 of the embodiment of the present invention, the position correction main process starts as a program when the machine tool is turned on (S0) as shown in FIG. First, in the initial setting step (S1), each displacement amount δ (δx, δy, δz, δs) is calculated at a predetermined sampling time (Tm) interval and the control memory (M31) of the control means (5) is calculated. Selective setting of the sampling time (Tm) to be stored and displayed in and the position correction of each axis, displacement amount correction process (S
5) The correction time (Tc) is selected and set as the time interval to execute, and when Δt = Tm (for example, every 30 seconds) is reached in the displacement sampling time reaching step (S2), the displacement sampling is performed. in step (S2), using the displacement amount calculation means, the last sample time: at t _i-1, the displacement amount _{δ i-1 (δx, δy} , δz, δs) from read out from the control memory (M31) Determine the heating state transition (CASE I) or cooling state transition (CASE II) by using the average velocity data set DS (V _i ) value including the movement frequency that changed during the time interval Tm = t _i -t _i-1. and the current sampling time: each displacement amount [delta] _i of t _i is calculated secured, and the displacement amount [delta] _i as a data set DS ([delta]), and stores該制in control memory (M31), the operation unit (5a) It can be displayed by the display means provided in the next step
At (S4), when Δt = Tc (eg, every 3 minutes) is reached,
In the displacement amount correction step (S5), the data set DS (δ) closest to the current time is read from the control memory (M31),
In the gradient correction step (S51), using the correction amount calculation means,
The correction amounts Cx, Cy, Cz for each axis are calculated and stored in the correction memory (M51) of the control means, and the correction amount Cx of the correction memory (M51) is stored according to the movement command from the machining control process (W1). , Cy, Cz are read out, and each axis moving device is read through the interface (W2).
It is characterized by correcting the position of (2,3,4).

In the simple thermal displacement correction method for a machine tool according to claim 1 of the embodiment of the present invention, the displacement amount calculation means used in the displacement amount sampling step (S2) in the position correction main step is shown in FIG. Thus, each displacement δ (δx, δy, δ
z, corresponding to .delta.s), t-[delta] current point on the plane: The current sampling time P _i: each displacement amount [delta] _i of t _i in order to calculate secured, the last sample time: at t _i-1 Point: At P _i-1 , the time interval Tm = t read from the control memory (M31)
_{Using the} average velocity data set DS (V _i ) value including the movement frequency changed between _i -t _i-1 , the previous displacement amount: δ _i-1 and this average velocity data: V _i are compared. The following cases are judged. When CASE I: V _i > δ _i-1 / K, the heat generation state shifts. Therefore, the exothermic function passing through the point: P _i-1 and the current point: P _i is f (t) = K ・ V _i・ [1- exp (-t / τh)], and this time axis: t The time interval between the origin and the time t _i-1 : M _i-1 is M _i-1
= -τh ・ In [1- δ _i-1 / (K ・ V _i )] given by T
_{Since i} = M _i-1 + Tm, therefore, at the current point: P _i , we move to δ _i = f (T _i ) = f (M _i-1 + Tm). When CASE II: V _i ≤ δ _i-1 / K, the cooling state is entered. Therefore, the point: the [delta] _i-1 of the P _i-1, attenuated by a corresponding cooling time constant .tau.c, cooling function, g (t) = δ
_i-1 · exp (-t / τc), so at the current point: P _i ′, we move to δ _i = g (Tm) = δ _i-1 · exp (-Tm / τc). In this way, the current sampling time: t
Each displacement of [delta] _i of _i is calculated secured, and the displacement amount [delta] _i as a data set DS ([delta]),該制stored in your memory (M31), and can be displayed on the display means having the operating portion (5a) To do.

In the simple thermal displacement correction method for machine tools according to claim 1 of the embodiment of the present invention, the correction amount calculation means used in the gradient correction step (S51) of the main position correction step is as shown in FIG. , (A) In the case of the correction amount Cx of the X axis, the middle of the X axis stroke length: STx is the origin, and both ends of the STx are the displacement fixed end (Fx) and the displacement free end (Ex). A displacement amount δx is generated at the free end (Ex), so the correction amount Cx (x) on the X-axis
Is Cx (-STx / 2) = 0, and Cx (S
Tx / 2) =-δx is given, and correction is ensured by proportional distribution using a linear gradient between the stroke lengths (STx). (B) In the case of the Y-axis correction amount Cy, the origin is the displacement free end (Ey), which is one end of the Y-axis stroke length: STy, and the other end is the displacement fixed end (Fy). Ey), displacement-
Since δy is generated, the Y-axis correction amount Cy (y) gives Cy (STy) = 0 and Cy (0) = δy at both ends of the STy, and the linear gradient between the stroke lengths (STy). Proportional distribution is used to secure the correction. (C) In the case of the Z-axis correction amount Cz, the displacement fixed end (Fz), which is one end of the Z-axis stroke length: STz, is the origin, and the other end is the displacement free end (Ez). Ez), the amount of displacement δ
When z occurs, the displacement amount of the spindle front end face (1b) -δs becomes
Since it occurs at the origin, the correction amount Cz (z) in the z-axis direction
Since the displacement amount δz is proportionally distributed between the strokes (STz) using a linear gradient, and the displacement amount δs is uniformly added to secure the correction, Cz (0) = δs, and Cz ( STz) = δs-δz
Therefore, the correction can be secured by using the linear gradient during the stroke (STz). The values stored in the correction memory (M51) for these correction amounts Cx, Cy, Cz are linear gradient corrections that connect the correction values at both ends between each axis stroke, so it is only necessary to store the correction values at both ends. To do.

In the simple thermal displacement correction method for a machine tool according to claim 1 of the embodiment of the present invention, the displacement amount measurement results are as shown in FIG. In the Y-axis measurement result, the maximum displacement without correction was 16 μm, but with correction, the maximum displacement could be suppressed to 2 μm or less, and Fig. 9
As shown in (B), in the comparison displacement amount Z-axis measurement result with and without correction, the maximum displacement amount without correction was 32 μm.
It can be suppressed to 10 μm or less, and by using this simple thermal displacement correction method, the maximum displacement can be suppressed to about 10 μm or less.

[0034]

The present invention is carried out in the form as described above and has the effects as described below.

The method for correcting thermal displacement of a machine tool according to the present invention is surprising in spite of using a first-order lag equation and an exponential damping equation that are determined by simple two constants as a heat generation function and a cooling function, respectively. In the position correction main process, it has the effect of suppressing the maximum displacement amount to about 10 μm or less over each axis stroke.

In the simple thermal displacement correction method for a machine tool of the present invention, in the thermal displacement measuring means, the displacement amount of each axis is the displacement amount δ representing the maximum displacement corresponding to the freely displaceable free end of one end of the stroke. Since it is measured, the displacement value is large,
It has the effect of making relative error small and making it easy to measure, and not requiring time for measurement and analysis.

In the simple thermal displacement correction method for the machine tool of the present invention, the correction amount Cz of the z axis is the displacement amount δ in the gradient correction step.
z is proportionally distributed between strokes (STz) by using a linear gradient, and the displacement amount δs is uniformly added to secure the correction, while the correction amounts Cx and Cy for the x and y axes are the respective displacement amounts. (δ
x, δy) is proportionally distributed between the corresponding strokes (STx, STy) using a linear gradient to ensure the correction, so that the correction between the strokes is possible and the correction amount C can be calculated by linear correction. Therefore, the calculation method is simple, and the value to store the correction amount C in the correction memory has only the effect of storing the correction values at both ends of each axis stroke.

In the simple thermal displacement correction method for a machine tool of the present invention, the heat generation function and the cooling function are easily expressed by the first-order lag equation and the exponential decay equation which are determined by simple two constants, respectively. Displacement amount calculation means of
By the analytical solution of the function, each displacement amount at the current sampling time is easily calculated, and since differential addition is not performed, it has the effect of reducing the addition error.

A simple thermal displacement correction method for a machine tool according to the present invention is a machine tool equipped with a coolant device, and
It can be used in response to various operating thermal environment conditions such as machine tools where the cutting tool is under a certain amount of load.

[Brief description of drawings]

FIG. 1 is a schematic explanatory block diagram showing a thermal displacement measuring means used in a thermal displacement correction pretreatment step in a simple thermal displacement correction method for a machine tool showing an embodiment of the present invention; and (B). Is the displacement amount δ on the coordinate axes of the schematic explanatory diagram,
The relationship between the displacement fixed end F and the displacement free end E.

FIG. 2 shows Z-axis heat displacement measurement in a simple thermal displacement correction method for a machine tool showing an embodiment of the present invention.

FIG. 3 shows Z-axis cooling displacement measurement in a simple thermal displacement correction method for machine tools, showing an embodiment of the present invention.

FIG. 4 is a simplified thermal displacement correction method for a machine tool showing an embodiment of the present invention, (A) is an X-axis heat displacement measurement amount, and (B) is a Z-axis heat displacement measurement amount.

5A and 5B show a spindle heat generation displacement measurement amount and a cooling displacement measurement amount in a simple thermal displacement correction method for a machine tool showing an embodiment of the present invention.

FIG. 6 is a position correction main process in a simple thermal displacement correction method for a machine tool showing an embodiment of the present invention.

FIG. 7 is an explanatory diagram of a schematic displacement amount calculating means used in a displacement amount sampling process of a position correction main process in a simple thermal displacement correction method for a machine tool, showing an embodiment of the present invention.

FIG. 8 shows a gradient correction process of a position correction main process in a simple thermal displacement correction method for a machine tool showing an embodiment of the present invention. (A) is an X-axis correction amount: Cx, (B) is a Y-axis Correction amount: C
y, and (C) are schematic diagrams of the Z-axis correction amount: Cz.

9A and 9B show comparative displacement amount measurement results with and without correction in a simple thermal displacement correction method for a machine tool showing an embodiment of the present invention, where A is a Y-axis measurement value and B is a Z value. Axis measurement.

[Explanation of symbols]

1 spindle rotation device 1a spindle body 1b spindle front end surface 1c cutting tool 1d spindle motor 2 X-axis moving device 2d X-axis motor 3 Y-axis moving device 3a Y-axis moving table 3b Y-axis feed member 3c Y-axis moving member 3d Y-axis motor 3e Y-axis displacement fixing member 4 Z-axis moving device 4a Z-axis moving table 4b Z-axis feed member 4c Z-axis moving member 4d Z-axis motor 4e Z-axis displacement fixing member 5 Control means 5a Operation part 6 Jig 7 Workpiece 8 stand 10 Position measuring means 11 Temperature measuring means δ Displacement (subscripts x, y, z belong to each axis, and s belongs to the main axis) δm Reachable displacement (subscripts x, y, z belong to each axis, and s belongs to the main axis) ) τ time constant (subscript h belongs to heating state, and c belongs to cooling state) e error f (t) heating function (subscripts x, y, z belong to each axis, and s belongs to main axis) g (t) cooling Function (subscripts x, y, z belong to each axis, and s belongs to the main axis) rpm Average rotation speed: rotations per minute s Axis t Time C Correction amount (Subscript x, y, z belongs to each axis) DS Data set E Displacement free end (Subscript x, y, z belongs to each axis) F Displacement fixed end (Subscript x, y, z z characteristic coefficient (= δm / V) (subscript x, y, z is each axis, and
ST stroke (suffixes x, y, z belong to each axis) Tc compensation time Tm sampling time V average speed (subscripts x, y, z are feed speeds of each axis, and s is rotation of the spindle) Belongs to speed)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3C001 KA05 KB02 KB04 TA04 TB01                       TB05 TB09 TB10 TC05 TC09                       TD03 TD07                 3C029 BB02                 5H269 AB01 BB01 BB03 CC02 CC18                       DD01 EE05 EE07 EE11 EE14                       FF06 GG06 NN04 NN07 NN16                       PP17

Claims (3)

[Claims] 1. A moving member (2c, 3c, 4) that moves on a rotation average speed (Vs) of a main spindle body (1a) and a feed member (2b, 3b, 4b) in each three-dimensional axial direction.
The average feed rate (Vx, Vy, Vz) and its operating time (t) in c), and the spindle position of the spindle front end face (1b) due to heat and cooling heat displacement due to these operating thermal environment conditions are constantly corrected. This is a simple thermal displacement correction method for a machine tool that performs the position correction main process together with the cutting process by the control means (5) .The heat generation function f represents each displacement δ used in the position correction main process. In order to predetermine (t) and the cooling function g (t), the thermal displacement correction pretreatment process is performed using the thermal displacement measuring means, and in the machine tool, the main axis (s) axis is the z axis. In each heat generation function f (t), the reached displacement amount δm is the heat generation time constant τh
Is a first-order lag equation that reaches saturation with time t, and the ultimate displacement δm is the characteristic coefficient K (k
x, ky, kz, ks) and average velocity V (Vx, Vy, V
z, Vs), while each cooling function g (t) is
When the corresponding operation is stopped, the exponential decay of the initial displacement amount δm with the cooling time constant τc is performed with time t, and the exponential decay formula is used. Axial displacement δs is measured by the position measuring means (10)
On the other hand, the z-axis thermal displacement measuring means defines the stroke (STz) of the rotatable feed member (4b) and the displacement fixed end (Fz) at one end that fixes the displacement in the z-axis direction. , At the other end of displacement free end (Ez)
At the position corresponding to (Ez), the displacement amount δz is measured by the position measuring means, and the thermal displacement measuring means of the x and y axes measure the strokes near the corresponding side circumferential corners of the front end face of the spindle. S
Tx, STy) at the displacement free ends (Ex, Ey), the displacements (δx, δy) are measured by the position measuring means, and the displacements δ (δx, δy, δz, The correction amount C of the spindle position on the front end face of the spindle according to δs) is calculated by the gradient correction step (S5
1), the correction amount Cz of the z-axis is proportionally distributed by using a linear gradient between the strokes (STz), and the displacement amount δs is uniformly added to secure the correction amount Cz. On the other hand, the correction amounts Cx and Cy on the x and y axes are respectively the displacement amounts (δx, δy)
The linear gradient is proportionally distributed between the corresponding strokes (STx, STy) to ensure the correction, and especially the operating thermal environment condition for performing the thermal displacement correction pretreatment step is A simple thermal displacement correction method for machine tools characterized by being a load. 2. The machine tool according to claim 1, wherein the working thermal environment conditions for performing the thermal displacement correction pretreatment step are such that a predetermined amount of coolant liquid for cooling the vicinity of the processing portion is circulated and equipped with a coolant device. Simple thermal displacement correction method. 3. The simple machine tool according to claim 1 or 2, wherein the working thermal environment condition in which the thermal displacement correction pretreatment step is performed is that the spindle body (1a) and the cutting tool (1c) are loaded with a predetermined amount. Thermal displacement compensation method.