JP2003285244A - Thermal displacement correcting method for use in nc engine lathe, and nc engine lathe using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal displacement correcting method for use in an NC engine lathe, which detects thermal displacement in the NC engine lathe through a simple configuration, with high accuracy and high reliability, and to provide the NC engine lathe using the method. <P>SOLUTION: In the NC engine lathe, a tool post is arranged so as to face a headstock, and the movement of the tool post is controlled in directions of X, Y, and Z axes. According to the NC engine lathe, a measurement referential jig is attached to the tool post, and thermal displacement sensors for detecting the thermal displacement between the measurement referential jig and a head on which the tool post is mounted, are placed at locations X<SB>1</SB>, X<SB>2</SB>in the X axis direction at a predetermined interval, at a location Y<SB>1</SB>in the Y axis direction, and at a location Z<SB>1</SB>in the Z axis direction. According to the thermal displacement correcting method, provided that detected thermal displacement values are represented by ΔX<SB>1</SB>, ΔX<SB>2</SB>, ΔY<SB>1</SB>, and ΔZ<SB>1</SB>, respectively, a distance d between the headstock and the tool post is corrected so as to assume a constant value by using a value Δd which is calculated by the following expression, Δd=ΔX<SB>1</SB>+α [α=f(ΔX<SB>1</SB>, ΔX<SB>2</SB>, ΔY<SB>1</SB>, ΔZ<SB>1</SB>)]. Further, a correction value β for the distance between the headstock and the tool post, which is obtained from a load heat variation of a tool post feeding means in the X axis direction, may be added as needed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic thermal displacement correction which automatically corrects against a thermal change with time in an NC lathe so as to keep a constant distance between a headstock on which a workpiece is chucked and a tool rest. The present invention relates to a method and an NC lathe using the same.

[0002]

2. Description of the Related Art In a machine tool such as an NC lathe, it is very important to secure the accuracy of the position of the cutting edge of a tool attached to a tool rest with respect to a workpiece to be machined. Therefore, it has been conventionally proposed to correct the change in the relative position (distance) between the spindle and the tool post due to the processing heat, the circulating heat of the coolant, the temperature change over time in the environment in which the machine is installed, and the like.

As a typical example thereof, a tool for measuring the temperature at each point of the machine, such as a tool rest, a feed device for the tool rest, a bed on which the tool rest is installed, a headstock, etc., is attached, and the temperature at each point is measured. X ₁ , X ₂ , X _3, ... And the change amount of the distance between the spindle and the tool rest is Δd, then Δd = aX ₁ + b
The distance d between the headstock and the tool rest is corrected by experimentally obtaining an approximate expression of X ₂ + cX ₃ + ... (a, b, c ... Constant). However, in such a conventional method, not only the means for accurately measuring the temperature at each point is expensive, but also the temperature change changes intricately depending on the operating condition of the machine and the usage environment, and is required experimentally. In many cases, there is a problem with the reliability of the correction formula. In particular, since it is a correction formula for the distance between the spindle and the turret with respect to the temperature change at each point, it is not practical in that the inclination of the turret with respect to the heat change is not directly considered.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable thermal displacement amount correction method capable of detecting a thermal displacement amount with high accuracy and a simple structure in an NC lathe, and an NC lathe using the same. To do.

[0005]

The invention according to claim 1 is
A tool rest is provided facing the headstock, and the tool rest is X,
In an NC lathe controlled to move in the Y and Z axis directions, a thermal displacement is detected by attaching a measurement reference jig to the tool post and detecting the amount of thermal displacement between the measurement reference jig and the bed on which the tool post is installed. The sensors are attached at two points X ₁ and X ₂ with a predetermined interval in the X-axis direction, a Y _{1 in the} Y-axis direction and a thermal displacement sensor Z _{1 in the} Z-axis direction are attached, and the detected thermal displacement amounts are respectively Letting ΔX ₁ , ΔX ₂ , ΔY ₁ , and ΔZ ₁ be the following equation, Δd = ΔX ₁ + α [α = f (ΔX ₁ , ΔX
X _2, ΔY _1, using the values obtained Δd in [Delta] Z ₁₎ tool rest inclination sought], NC lathe spindle and the tool rest of the distance d and correcting to be constant Is a method for correcting the amount of thermal displacement in.

Assuming that the correction equation Δd = ΔX ₁ + α, ΔX ₁ ,
Since the value obtained by obtaining the change amount α of the inclination of the tool post from ΔX ₂ , ΔY ₁ , and ΔZ ₁ was also used for the correction, it acts to directly correct the distance between the spindle and the tool post. Also, since the difference in the distance between the measurement reference jig attached to the tool post and the predetermined position of the bed that is not easily affected by the environment is directly detected as the amount of thermal displacement, use an eddy current type displacement sensor, etc. With a simple structure, highly accurate thermal displacement can be obtained.

According to a second aspect of the present invention, the headstock is opposed to the headstock.
A turret is provided, and the turret moves in the X, Y, and Z axis directions.
In a NC lathe that is dynamically controlled, a measurement reference jig is attached to the tool post.
The measurement reference jig and the turret are installed.
A thermal displacement sensor that detects the amount of thermal displacement between the
Set a predetermined interval in the X-axis direction, X₁, X_Two2 points
Attach Y in the Y-axis direction₁, Z along the Z axis₁Thermal displacement sensor
Sir and attach the detected thermal displacement amount to Δ
X₁, ΔX_Two, ΔY₁, ΔZ₁And the turret in the X-axis direction
The main value obtained from the amount of load load thermal displacement applied to the feeding means
If the distance correction value between the shaft and the turret is β, the following equation, Δd = ΔX
₁+ Α + β [α = f (ΔX₁, ΔX_Two, ΔY ₁, Δ
Z₁The value of Δd obtained by
To adjust the distance d between the spindle and the tool post to be constant.
The method for correcting the thermal displacement is correct.

According to the invention described in claim 2, the accuracy of the correction method according to claim 1 is further improved. The thermal load load such as the servo motor of the tool rest feeding means in the X-axis direction is corrected by the correction method. Β calculated from the amount of change was added. This is because a ball screw, which is widely used as a feed means for a tool post, usually has a spacer or the like mounted between the nuts that hold the ball and a preload is applied to the ball. The focus is on the change due to the thermal change of the ball screw and the like.

According to a third aspect of the present invention, a turret is provided facing the headstock, the turret is provided with movement control means in the X, Y, and Z-axis directions, and the turret and the turret are installed. Between X ₁ and X _{2 in} the X-axis direction to detect the thermal displacement between
A point thermal displacement sensor is provided, a Y ₁ thermal displacement sensor is provided in the Y-axis direction, a Z ₁ thermal displacement sensor is provided in the Z-axis direction, and these thermal displacement amounts ΔX ₁ , ΔX ₂ , Δ
Based on Y ₁ and ΔZ ₁ , the following equation, Δd = ΔX ₁ + α [α
= F (ΔX ₁ , ΔX ₂ , ΔY ₁ , ΔZ ₁ ) the inclination of the tool post], a means for automatically calculating the value of Δd is provided, and the tool post relative to the spindle based on this value of Δd. It is an NC lathe equipped with means for correcting the position. this is,
An NC lathe in which the correction method according to claim 1 is developed.

The invention according to claim 4 is the structure of claim 3.
In addition, heat load change of the X-axis direction feed means of the tool post
Detection of correction value β for the distance between the spindle and the turret, which is obtained from the amount
Means, and the following equation, Δd = ΔX₁+ Α + β [α = f (Δ
X₁, ΔX_Two, ΔY₁, ΔZ ₁) Of the turret required
[Slope] is used to automatically calculate Δd.
Compensate the relative position of the tool post with respect to the spindle based on the value of Δd.
It is an NC lathe equipped with a corrective means. This is claim 2.
It is an NC lathe that developed the correction method of.

According to a fifth aspect of the present invention, the thermal displacement sensor according to the third or fourth aspect is arranged so as to be measured when the tool rest reaches the origin position. By this, N
When the tool rest returns to the origin position, that is, at the reference position, the thermal displacement generated during the automatic operation of the C lathe is measured, and the value is corrected and canceled.

[0012]

1 shows an example of a thermal displacement amount correction method according to the present invention. In FIG. 1, a tool rest 3 having a turret tool 2 attached thereto faces the spindle 1 for holding a workpiece to be processed in a chuck in the front-rear X-axis direction, the left-right Z-axis direction, and the vertical Y-axis direction. Movement is controllable. Although not shown, the movement control means is rotationally controlled by a servo motor via a ball screw between the bed and the tool rest. A measurement reference jig 4 is attached to the tool rest 3. A thermal displacement sensor mounting member 5 is provided on the bed side in order to detect a change in the distance from the measurement reference jig when the tool rest comes to the origin position.
Eddy current displacement sensors X ₁ (6) and X ₂ (7) are provided to detect changes in axial distance. Similarly,
Displacement sensor Z that detects changes in distance in the Z-axis direction
₁ (8), a displacement sensor Y ₁ (9) for detecting a change in distance in the Y-axis direction is provided. These changes Δ
The relationship between the values of X ₁ , ΔX ₂ , ΔY ₁ , and ΔZ ₁ and the inclination of the tool post was experimentally obtained in advance, and α = f (ΔX ₁ , ΔX ₁
X ₂ , ΔY ₁ , ΔZ ₁ ) are obtained. Further, although not shown in the figure, there is provided means for detecting the amount of change in the load load of the servo motor loaded at a constant feed rate in the X-axis direction of the tool rest. The relationship between the change in the load of the servo motor and the change in the distance between the spindle and the tool post is β
Is experimentally sought as. From these values, the thermal displacement correction value Δd is automatically calculated by the formula Δd = ΔX ₁ + α + β.
Is incorporated into the machining program so that is calculated, and the position of the tool rest is corrected.

[0013]

According to the present invention, the measurement reference jig is attached to the tool rest, and the eddy current displacement sensor attached to the bed at the origin position of the tool rest is used to measure the position of the measurement reference jig on the tool rest. Since the configuration is such that the change in is calculated, it is possible to perform correction so that the distance between the spindle and the tool rest can be reliably kept constant at the origin position, despite the simple structure. Further, since the inclination of the tool rest and the load variation of the servo motor are used as the correction parameters, the reliability of the correction value is improved as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a thermal displacement correction method according to the present invention.

[Explanation of symbols]

1 spindle 2 turret tools 3 turrets 4 Measurement reference jig 5 Eddy current displacement sensor mounting member 6, 7 Eddy current displacement sensor mounted in the X-axis direction 8 Eddy current displacement sensor attached in the Z-axis direction 9 Eddy current displacement sensor mounted in the Y-axis direction

Claims (5)

[Claims] 1. An NC lathe in which a tool rest is provided so as to face a headstock, and the tool rest is controlled to move in the X, Y, and Z directions, and a measurement reference jig is attached to the tool rest, A thermal displacement sensor that detects the amount of thermal displacement between the jig and the bed on which the tool rest is installed is attached at two points X ₁ and X _{2 with} a predetermined interval in the X axis direction, and Y in the Y axis direction. ₁ ,
A thermal displacement sensor Z ₁ is attached in the Z-axis direction, and the detected thermal displacement amounts are ΔX ₁ , ΔX ₂ , ΔY ₁ , and ΔZ, respectively.
_{If 1} , then the following equation, Δd = ΔX ₁ + α [α = f (Δ
X ₁ , ΔX ₂ , ΔY ₁ , ΔZ ₁ ) The inclination of the turret obtained by [] is used to correct the distance d between the spindle and the turret to be constant. NC
Thermal displacement compensation method for lathes. 2. A tool rest is provided facing the headstock,
For NC lathes whose turrets are controlled to move in the X, Y and Z axes
Then, attach the measurement reference jig to the turret and
Thermal displacement between the quasi jig and the bed on which the turret is installed
Set the thermal displacement sensor that detects the amount at a predetermined interval in the X-axis direction.
Provide, X₁, X_Two2 points attached, Y in the Y-axis direction₁,
Z along the Z axis₁Attach a thermal displacement sensor that detects
The thermal displacement amount is ΔX₁, ΔX_Two, ΔY₁, ΔZ
₁And load applied to the tool post feed means in the X-axis direction
The distance correction value between the headstock and the tool post calculated from the amount of thermal displacement under load
Let β be the following equation, Δd = ΔX₁+ Α + β [α = f (ΔX
₁, ΔX_Two, ΔY₁, ΔZ ₁) Turret tilt required by
The distance between the spindle and the turret, using the value of Δd obtained in
NC rotation characterized by correction so that d becomes constant
Method for correcting the amount of thermal displacement on the board. 3. A thermal displacement amount between a tool rest and a bed on which the tool rest is installed, the tool rest facing the headstock, the tool rest being provided with movement control means in the X, Y, and Z directions. A two-point thermal displacement sensor of X ₁ and X ₂ is provided in the X-axis direction for detecting the, and a thermal displacement sensor of Y ₁ is provided in the Y-axis direction.
A thermal displacement sensor of Z ₁ is provided in the Z-axis direction, and based on these thermal displacement amounts ΔX ₁ , ΔX ₂ , ΔY ₁ , ΔZ ₁ ,
The following equation, Δd = ΔX ₁ + α [α = f (ΔX ₁ , ΔX ₂ , Δ
Inclination of the tool rest obtained by Y ₁ , ΔZ ₁ )], and Δd
The NC lathe is provided with means for automatically calculating the value of, and means for correcting the relative position of the tool rest with respect to the spindle based on the value of Δd. 4. In addition to the structure of claim 3, a means for detecting a correction value β of the distance between the spindle and the tool post, which is obtained from the load load heat change amount of the X-axis direction feed means of the tool post, is provided, Δd
= ΔX ₁ + α + β [α = f (ΔX ₁ , ΔX ₂ , ΔY ₁ ,
The inclination of the turret obtained by ΔZ ₁ )], means for automatically calculating Δd, and means for correcting the relative position of the turret with respect to the spindle based on the value of this Δd. NC lathe. 5. An NC lathe, wherein the thermal displacement sensor according to claim 3 or 4 is arranged so as to be measured when the tool rest reaches the origin position.