JP3517738B2 - Simple thermal displacement compensation method for machine tools - Google Patents

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 conventional thermal displacement correction method for machine tools described above, as an approximate expression, for example,
As shown in “Paragraph 0026”, the amount of heat generation displacement per unit time
Qn is expressed by Qn = A ・ [f (Bn)] ^a・ Cn ^b and exponentiation coefficients: a, b. It is complicated and easy to approximate the approximation formula 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 type addition. In such differential type addition, an error is added and the error of 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 3 points using the displacement fixed end (Fz) at one end where the displacement of the Z-axis stroke is fixed 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) shall be an exponential decay formula that decays exponentially from the initial displacement δ mi at the cooling time constant τ c with time t when the corresponding operation is stopped. Is characterized by.

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 δ mi decays exponentially with cooling time constant τ c with time t. The exponential decay formula is used, and the thermal displacement measuring means of the spindle is the front end face of the spindle. The displacement δs in the z-axis direction is measured by a position measuring means (10) such as a pick tester.
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,
The x- and y-axis thermal displacement measuring means 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 main shaft position of the main shaft front end face by each displacement amount δ (δx, δy, δz, δs) is the slope correction process ( S51), the z-axis correction amount Cz is calculated by using the displacement amount δz as the stroke (ST
z) is proportionally distributed using a linear gradient, and the displacement δs
To ensure the correction, while the correction amounts Cx and Cy on the x and y axes are the linear displacements of the displacements (δx, δy) between the corresponding strokes (STx, STy). The operating thermal environment condition in which the gradient is proportionally distributed to secure the compensation and the thermal displacement compensation pretreatment step is performed is characterized in that the spindle is unloaded in the ambient atmosphere temperature.

A simple thermal displacement correction method for a machine tool according to claim 2 of the present invention is an operation for performing a thermal displacement correction pretreatment step.
If the spindle environment (1a) / cutting tool (1c) has a specified amount of thermal environment ,
It is in a loaded state, and the magnitude of the load is determined by the spindle motor (1d), etc.
Can be measured under the load of
You can also

A machine tool according to claim 3 of the present invention is simplified.
Easy thermal displacement correction method isOperation to perform thermal displacement correction pretreatment process
Thermal environment is spindle main body (1a) ·Cutting tools (1c) ・ Processed products
(7) A certain amount of cooler that cools the vicinity of the processing part consisting of etc.
It is possible to circulate the coolant and equip it with a coolant device.
come.

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) generally uses two constants, a characteristic coefficient K and a time constant τh,
It is characterized by being easily expressed as (t) = K ・ V ・ [1-exp (-t / τh)].

In the thermal displacement compensation pretreatment step of the simple thermal displacement compensation method for machine tools of the present invention, the cooling function is an exponential damping equation, g (t) = δ mi · exp (-t / τc), Here, it is characterized by being easily represented by two constants, a time constant τ c and an initial displacement amount δ mi .

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, and then Δt = Tm
Is reached, in the displacement sampling process (S2),
Using the displacement calculation means, last sampling time: t _i-1
In _from each displacement amount [delta] _i-1, using the average velocity data set DS (V _i) value including the movement frequency has changed during the time you read from the control memory (M31) interval Tm = t _i -t _i-1 determines whether heat generation state transition or cooling state transition, 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]), control memory ( M
31) and displayable by the display means provided in the operation unit. Then, in the displacement amount correction time reaching step (S4), Δt = Tc
When the displacement amount correction step (S5) is reached, the data set DS (δ) closest to the current time is set to the control memory (M3
1), and in the gradient correction process (S51), using the correction amount calculation means, the correction amount C for each axis is calculated and secured, and stored in the correction memory (M51) of the control means, and the machining control process (W1)
According to the movement command from, the correction amount C of the correction memory (M51)
It is also possible to read out 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 represented by two constants, c and the initial displacement δ mi , the time constant τ c is such that 1/2 of the initial displacement δ mi is δ1 = δ mi / 2 and the time t1 corresponding to δ1 is secured. , Τc = 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 representing 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
Axis compensation : Cz = ─ z ( δ z / STz) + δ s is the displacement δz
Is proportionally distributed between strokes (STz) using a linear gradient,
And the displacement amount δs is added uniformly to secure the correction, while the correction amounts Cx and Cy on the x and y axes are : Cx = ─ ( δ x / STx) [x + (STx
/ 2)], and Cy = ─ ( δ y / STy) [y -STy] are the displacements (δx, δy), and the corresponding strokes (STx, STy).
Since a linear gradient is used to proportionally distribute and secure the correction,
Correction between strokes is possible, the correction amount C is calculated linearly, the calculation method is simple, and the value stored in the correction memory (M51) is the correction value at both ends between each axis stroke. It has a good effect just to store the value.

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 machine tools, and Fig. 3 shows the Z-axis cooling displacement measurement results. 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 of moving member (2c, 3c, 4c)
(Vx, Vy, Vz) and its operating time (t), and the spindle front end face caused by heat and cooling heat displacement due to these operating thermal environment conditions.
The position correction main process for constantly correcting the spindle position in (1b)
A simple thermal displacement correction method for a machine tool that is performed by the control means (5) together with the cutting process, and the heat generation function f that represents each displacement amount δ (δx, δy, δz, δs) used in the position correction main process. In order to predetermine (t) and the cooling function g (t), the thermal displacement compensation pretreatment process is performed by using thermal displacement measuring means, and in the machine tool, the main axis (s) axis is the z axis. , The heat generation function f (t) is such that the ultimate displacement δm is the heat generation time constant τ
Let h be the first-order lag expression that reaches saturation with time t, and the amount of displacement reached δm is the corresponding proportional coefficient K
(kx, ky, kz, ks) and average speed V (Vx, V
y, Vz, Vs), while each cooling function g
(t) is the initial displacement δ m when the corresponding operation is stopped.
An exponential decay method is used in which the cooling time constant τc decays exponentially from i with time t. On the other hand, the z-axis thermal displacement measuring means determines the stroke (STz) of the rotatable feed member (4b) by fixing the displacement in the z-axis direction by using the measuring means (10). Displacement free end (Ez)
z), the z-axis carriage (4
a) At the end, measure the displacement amount δz by the position measuring means,
The x- and y-axis thermal displacement measuring means 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 amount δ (δx, δy, δz, δs) is as shown in FIG.
(S51), the z-axis correction amount Cz is proportionally distributed between the strokes (STz) using a linear gradient, and the displacement amount δs is uniformly added to ensure the correction. , On the other hand, x and y
The correction amounts Cx and Cy of the axes are the displacements (δx, δy), respectively.
Is proportionally distributed by using a linear gradient between the corresponding strokes (STx, STy) to ensure the correction, and in particular, the operating thermal environment condition for performing the thermal displacement correction pretreatment step is Is characterized by no 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-
exp (-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 ultimate displacement δm is δ1 = δm / 2, and the time corresponding to δ1 is Secure t1, τh =
The time constant τh can be easily obtained by t1 / 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 δm is changed to the initial displacement δ mi at the end of the z-axis moving base (4a) corresponding to the free end (Ez) of displacement. Then, the attenuation 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 ), the time constant τc of the cooling function is obtained by connecting the measurement points with a smooth curve,
It is possible to easily obtain the time constant τc by setting ½ of δ mi to δ1 = δ mi / 2, securing the time t1 corresponding to δ1, and τc = t1 / In2 = t1 / 0.693.

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), and their respective characteristic coefficients 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. ,
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), having the operating portion (5a) It is possible to display on the display means and then the displacement amount correction time reaching process
At (S4), when Δt = Tc (eg, every 3 minutes) is reached,
In the displacement correction step (S5), the data set DS (δ) closest to the current time is read from the control memory (M31), and in the gradient correction step (S51), the correction amount calculation means is used to correct each axis. The calculated amounts Cx, Cy, Cz are stored in the correction memory (M51) of the control means, and the correction amounts Cx, Cy, Cz of the correction memory (M51) are stored according to the movement command from the machining control process (W1). Is read out, and the position of each axis moving device (2, 3, 4) is corrected via the interface (W2).

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 read from the control memory (M31)
Using the average velocity data set DS (V _i ) including the movement frequency changed between = t _{i and} t _i-1 , the previous displacement amount: δ _i-1 and the current average velocity data: V _i are calculated. Compare and judge the following cases. 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 Time interval between the origin of and the time t _i-1 : M
_i-1 is given by M _i-1 = -τh · In [1- δ _i-1 / (K · V _i )], and T _i = M _i-1 + Tm, so the current point: P _i At, 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) , and the thus Current point: At P _i ′, transition 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) X axis correction amount Cx = ─ ( δ x / STx) [x + (STx / 2)] , the middle of X axis stroke length: STx is taken as the origin, and the STx
Displacement fixed end (Fx) and displacement free end (Ex)
Since the displacement amount δx is generated at the displacement free end (Ex), the correction amount Cx (x) of the X axis is Cx (-STx / 2) = 0, and Cx (STx / 2) =-δx is given, and correction is ensured by proportional distribution using a linear gradient between the stroke lengths (STx). (B) Y-axis correction amount Cy = ─ ( δ y / STy) [y-STy] , Y-axis stroke length: Displacement free end that is one end of STy
(Ey) is the origin, the other end is the fixed displacement end (Fy), and the displacement amount −δy is generated at the free displacement end (Ey).
The axial correction amount Cy (y) is Cy (STy) = at both ends of the STy.
0 and Cy (0) = δy are given, and the correction is ensured by proportional distribution using a linear gradient between the stroke lengths (STy). (C) Z-axis correction amount Cz = ─ z ( δ z / STz) + δ s ,
Z-axis stroke length: Displacement fixed end (Fz), which is one end of STz, is the origin, and the other end is the displacement free end (Ez).
At (Ez), the displacement amount δz is generated and the displacement amount −δs of the spindle front end face (1b) is generated at the origin.
The correction amount Cz (z) in the z-axis direction is proportional to the displacement amount δz between the strokes (STz) using a linear gradient, and the displacement amount δs is uniformly added to ensure the correction. Cz (0) = δs,
Then, Cz (STz) = Δs−Δz, and 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,
The relative error can be reduced and measurement can be performed easily, and the measurement and analysis do not take time.

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 correction, so correction between strokes is possible, and the correction amount C can be calculated using 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
In analytical solution of the function number, the calculation of the displacement of the current sampling time is easily performed, is not performed differentially adding, with a small Ku effectively the sum 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: Cy
, And (C) is an explanatory view of a rough correction amount calculation means of 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) ) δ mi Initial displacement τ Time constant (subscript h belongs to heat generation state, and c belongs to cooling state) e Error f (t) heat generation function (subscript x, y, z belongs 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: share Rotation speed s Spindle 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 belongs to each axis) K 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)

Claims (3)

(57) [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 machine tools that performs the position correction main process together with the cutting process by means of the control means (5) .The heat generation function f represents each displacement amount 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. And each exothermic function : f (t) = δ m · [1- exp (-t / τ h)] is the first-order lag of the ultimate displacement δ m reaching saturation with time t at the exothermic time constant τ h . The ultimate displacement δm = K · V
Has a corresponding proportionality coefficient K (kx, ky, kz, ks) and is proportional to the average velocity V (Vx, Vy, Vz, Vs) including the moving frequency, while Cooling function : g (t) = δ mi ・ exp (-t / τ c) decays exponentially from initial displacement δ mi with cooling time constant τ c with time t when the corresponding operation is stopped The exponential decay type is adopted, and the thermal displacement measuring means of the spindle is
The displacement amount δs in the z-axis direction is measured by the position measuring means (10), while the z-axis thermal displacement measuring means determines the stroke (STz) of the rotatable feed member (4b). At the position corresponding to the displacement free end (Ez) at the displacement fixed end (Fz) at one end where the displacement is fixed and the freely displaceable free end (Ez) at the other end, the displacement amount δz is The x- and y-axis thermal displacement measuring means measure the thermal displacement of the x-axis and y-axis in the vicinity of the corresponding side circumferential corner of the front end face of the spindle at the displacement free ends (Ex, Ey) of each stroke (STx, STy). displacement (.delta.x, .delta.y) respectively measured by said position measuring means, the displacement amount δ (δ x, δ y, δ z, δ s) pair
Response to該到we displacement δ m = K · V, the tau h, and tau c
Set, in said position correcting main steps, time of each displacement the free ends: t of the
Whether each displacement δ is in the heat generation state at a predetermined sampling time
The predetermined heat generation function and
Using fine cooling function, by the displacement amount calculation means corresponding to the V
Sequentially, the time of each axis : Complement corresponding to the displacement amount δ ( δ x, δ y, δ z) of t
In the positive amount C (Cx, Cy, Cz) , the correction amount of z axis : Cz = ─ z (
δ z / STz) + δ s is the amount of displacement δ z
A linear gradient is used between them to proportionally distribute, and the displacement amount δs is uniformly added to secure the correction, while the correction amount for the x and y axes is :
Cx = ─ ( δ x / STx) [x + (STx / 2)], and Cy = ─ ( δ y / STy) [y-STy] are
δx, δy) is proportionally distributed between the corresponding strokes (STx, STy) using a linear gradient to ensure compensation, and the thermal displacement compensation pretreatment step is performed under the ambient ambient temperature conditions. And a simple thermal displacement correction method for a machine tool, wherein the spindle is unloaded. 2. A rotation average speed (Vs) of the main spindle body (1a ), three- dimensional each
A moving member (2c, 3c, 4b) that moves on the axial feed member (2b, 3b, 4b)
Feed average speed of c) (Vx, Vy, Vz ) and its operating time (t), further this
Due to these actuation thermal environment conditions, heating and cooling thermal displacement
The position for constantly correcting the spindle position of the spindle front end face (1b)
The location correction main step, the cutting step, the control means (5)
A simple thermal displacement correction method for a machine tool, in which each displacement amount δ used in the main position correction process is expressed.
Thermal function f (t) and to determine cooling function g (t) in advance, the thermal variations
Perform the position correction pretreatment process using thermal displacement measuring means.
In the machine tool, the main axis (s) axis is the z axis.
Then, each exothermic function : f (t) = δ m · [1-exp (-t / τ h)] reaches
The displacement δ m reaches saturation with time t at the heat generation time constant τ h.
To, the expression of the first order delay,該到we displacement δ m = K · V
Is the characteristic coefficient K (kx, ky, kz, ks) which is the corresponding proportional coefficient.
Has, proportional to the average speed including the movement frequency V (Vx, Vy, Vz, Vs)
And Rukoto, while each the cooling function: g (t) = δ mi · exp (-t / τ c) , the corresponding work
At the stop time of movement, from the initial displacement amount [delta] mi exponentially
It decays with time t in a cooling time constant tau c, and exponential decay equation
And the thermal displacement measuring means of the spindle is
The z-axis direction of the displacement [delta] s, measured by the position measuring means (10)
And, on the other hand, the thermal displacement measuring means of the z-axis, the Ri rotatable said transmission member (4b)
Stroke (STz) is determined and displacement in the z- axis direction is fixed
Displacement fixed end (Fz) at one end and displaceable displacement end at the other end
In reason end (Ez), the position corresponding to the displacement free end (Ez)
In, the amount of displacement [delta] z measured by said position measuring means, and the thermal displacement measuring means of x and y-axis, corresponding to the main shaft the front end surface
That near side peripheral corner portion, the free displacement of each stroke (STx, STy)
End (Ex, Ey), the amount of displacement (δ x, δ y) of the respectively measured the position
And measure each displacement δ ( δ x, δ y, δ z, δ s) .
Response to該到we displacement δ m = K · V, the tau h, and tau c
Set, in said position correcting main steps, time of each displacement the free ends: t of the
Whether each displacement δ is in the heat generation state at a predetermined sampling time
The predetermined heat generation function and
Using fine cooling function, by the displacement amount calculation means corresponding to the V
Sequentially, the time of each axis : Complement corresponding to the displacement amount δ ( δ x, δ y, δ z) of t
For positive amount C (Cx, Cy, Cz) , z- axis correction amount: Cz = ─ z (
δ z / STz) + δ s is the displacement δ z of the stroke (STz)
Proportionally distributed with a linear gradient between, and the displacement amount [delta] s
Correction is ensured by adding uniformly , while correction amount on the x and y axes:
Cx = ─ ( δ x / STx) [x + (STx / 2)], and Cy = ─ ( δ y / STy) [y-STy] are the displacement amounts (
straight [delta] x, a [delta] y), each corresponding said stroke (STx, STy) between
The linear thermal gradient is used to proportionally distribute and secure the correction, and the thermal displacement correction pretreatment process is performed under the operating thermal environment condition of the spindle.
Check that the main body (1a) and cutting tool (1c) are in a prescribed load condition.
Wherein, the simple thermal displacement of a machine tool correction method. 3. An operating thermal environment article for performing a thermal displacement correction pretreatment process.
The problem is that a certain amount of coolant liquid that cools the processing area
Recycled use, equipped with a coolant device, claim 1 or
The simple thermal displacement correction method for a machine tool according to claim 2.