JPH0732247A - Thermal displacement correction in center work - Google Patents

Abstract

PURPOSE:To provide a method to precisely correct a cylindricity failure and a precision failure in the X and Y directions at the time of machining a center work due to thermal displacement on the side of a spindle stock and on the side of a tailstock. CONSTITUTION:A thermal displacement amount in the X direction and a thermal displacement amount in the Z axial direction of standard positions of a cylindrical part 6 of a center 6 on the side of a tailstock separated from a cylindrical part 1a of a spindle stock by a specified distance are respectively measured by tracers 11a, 11b of a sensor 11 installed on a cutting tool post 7, and from difference of the thermal displacement amounts on the spindle stock side and the tailstock side and a distance between the standard positions, a thermal displacement rate for a unit Z axial dimension is found. Thereafter, by adding or subtracting the measured thermal displacement amount on the spindle stock side or the tailstock side to or from a value found by way of multiplying a distance from the standard position of a cutting tool by this thermal displacement rate and finding thermal displacement correction values in the X direction and the Z direction corresponding to a Z axial moving destination of the cutting tool, correction is continuously carried out synchronously with cutting feed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of correcting a machining accuracy error due to thermal displacement during cutting of a center work.

[0002]

2. Description of the Related Art Conventionally, when cutting a relatively long work on a lathe with an outer diameter, the cutting is performed with the tip supported by a tailing center. When such a center work is continuously operated for a long time, the thermal displacement of the headstock side due to the heat generation of the rotating part such as the main bearing, the temperature change of the pressure oil of the hydraulic tailstock, the heat generation of the center bearing part, etc. Due to the thermal displacement on the side of the platform, the processing size changes and a taper occurs. As a device for automatically correcting thermal displacement during machining of this center work, Japanese Patent Publication No. Sho 49-151
There is No. 1 prior art.

As shown in FIG. 8, when this workpiece W is gripped by a chuck F and a work W whose tip is supported by a center K is continuously machined, the center O of the spindle S is displaced by -ΔX and moved to O '. At this time, if the center K of the tailstock has no thermal displacement, the center of rotation of the work is inclined by Δθ and is tapered. Therefore, the moving distance L in the Z-axis direction of the cutting tool during cutting
The correction in the X-axis direction is -ΔX × {L / (Lo + L ₁ )} according to the above. However, L
₁ = Work length, Lo = Gap between work end and spindle side thermal displacement measurement position.

[0004]

Although the technique of Japanese Patent Publication No. Sho 49-1511 described in the prior art makes a correction on the assumption that there is no thermal displacement on the tailstock side, the hydraulic core is often used for continuous machining. The tailstock also undergoes thermal displacement on the tailstock side due to the temperature change of the pressure oil. Therefore, there is a problem that the correction amount is different from the actual state and the taper remains and the dimensional correction is not perfect. The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a thermal displacement correction method for a center work in which thermal displacement on the tailstock side is taken into consideration. To do.

[0005]

In order to achieve the above object, a method for correcting thermal displacement in a center work according to the present invention is Z
The thermal displacements in the X-axis direction and / or Z-axis direction of the headstock side reference position and the tailstock side reference position, which are separated by a predetermined distance in the axial direction, are measured by sensors mounted on the tool post, respectively, and the headstock side and tailstock side are adjusted. From the difference in the thermal displacement amount on the table side and the predetermined distance, a unit Z
The thermal displacement rate per shaft dimension is calculated, and the thermal displacement rate is calculated as Z
X corresponding to the Z-axis movement destination of the blade during machining by adding or subtracting the thermal displacement amount on the headstock side or tailstock side to a value obtained by multiplying the distance from the reference position during axis movement Direction and / or Z direction thermal displacement correction values are obtained and continuously corrected in synchronization with the cutting feed.

[0006]

[Function] The initial values of the headstock side reference position and the tailstock side reference position in the X-axis direction and / or the Z-axis direction are measured and stored, and the current values after continuous machining for a predetermined time are measured. , The thermal displacement amount which is the difference is calculated, the thermal displacement correction value in the X-axis direction and / or the Z-axis direction corresponding to the destination Z-axis position of the cutting tool during cutting is calculated, and the command value is added to correct the thermal displacement correction. I do.

[0007]

Embodiments will be described below with reference to the drawings. In the NC lathe of FIG. 1, a spindle 2 is rotatably supported by a spindle headstock 1 fixed on the left side of a bed installed on the floor, and a chuck 3 is concentrically fitted to the tip of the spindle 2. Two sets of Z-axis direction guides are provided on the bed, and the tailstock 4 is movably placed on one of the Z-axis guides. A tailstock shaft 5 is supported on the tailstock 4 so as to be movable in the axial direction. The tailstock shaft 5 is driven by a hydraulic cylinder piston member (not shown), and a center 6 is detachably fitted to the tip thereof. Further, a tool rest 7 is mounted on the saddle 9 which is movably mounted on the other Z-axis guide of the bed so as to be movable in the X-axis, and the tool rest 7 is mounted on the tool rest 7 around the central axis of rotation in the Z-axis direction. A turret 8 is provided so that it can be swivelly indexed.

As shown in FIG. 2, the saddle 9 is moved and positioned by a Z-axis servomotor 10 fixed to the bed via a ball screw 12, and a position detector 10a is fixed to the Z-axis servomotor 10. Further, the tool rest 17 is attached to the saddle 9 by the X-axis servomotor 13 and the ball screw 1
The position detector 13a is attached to the X-axis servomotor 13 by being moved and positioned through the position 4 of FIG. The Z-axis guide of the bed may be a pair of tailstock 4 and saddle 9. Tool mounting stations are provided on the turret 8 at equal intervals on the outer periphery, and an in-machine measuring sensor 11 is removably mounted on one of the tool mounting stations. The sensor 11 has a headstock side measuring contact needle 11a and a tailstock side measuring stylus 11b. The headstock 1 is provided with a cylindrical portion 1a for measuring thermal displacement concentrically with the spindle 2, and also in the center 6. The thermal displacement measuring cylindrical portion 6a is provided concentrically with respect to the center axis.

In the NC device 16, as shown in the block diagram of FIG. 2, a manual operation control section 18 for judging a manual input signal from the operation panel 17, an NC program input means 19 for paper tape, floppy disk, communication, etc. The NC program interpreting section 20 for judging the automatic input signal from the CPU, the axis movement control section 21 for driving the X-axis servo motor 13 and the Z-axis servo motor 10 according to the command values are built in, and the above is almost different from the conventional one. There is no place.

Further, the NC device 16 incorporates an execution data generating section 22, a thermal displacement amount storage section 23, and a thermal displacement correction development value storage section 24 according to the present invention. The execution data generation unit 22 obtains the thermal displacement amount by reading the X-axis and Z-axis coordinate values at the time when the stylus 11a, 11b of the sensor 11 abuts on the cylindrical portions 1a, 6a and the signal is turned ON. A portion for obtaining a thermal displacement correction value corresponding to the Z-axis movement destination of the tool T during outer diameter machining from the thermal displacement amount, a portion for storing the measured thermal displacement amount, a thermal displacement amount storage portion, and a thermal displacement correction development value storage The section 24 is a section for collectively storing thermal displacement correction values corresponding to the Z-axis movement destination of the blade T.

Next, the operation of this embodiment will be described.
First, with respect to the setting of the initial value of the X-direction thermal displacement, which is the basis of the calculation of the thermal displacement in the X-direction, according to the flowchart of FIG.
Will be described with reference to. In step S1, it is confirmed that the machine body temperature is almost constant, and in step S2, the operation panel 17 or the NC program input means 19 instructs the execution data generator 22 to set an initial value in the X direction on the headstock 1 side. In the setting state, in step S3, the X-direction thermal displacement measurement reference position of the headstock cylindrical portion 1a is measured manually or automatically by the stylus 11a of the sensor 11. Then, in step S4, the coordinate values Xxs1 and Zxs1 at the time when the stylus 11a comes into contact with the cylindrical portion 1a and the signal is turned on are stored in the thermal displacement amount storage unit 23 as initial values in the X-direction on the headstock side.

Next, in step S5, the execution data generating section 22 is instructed to set the initial value in the X-axis direction on the tailstock 4 side to be set, and in step S6, the sensor 11 is set.
The X-direction thermal displacement measurement reference position of the cylindrical portion 6a of the center 6 is measured by the stylus 11b. Then, in step S7, the coordinate values Xxc1 and Zxc1 at the time when the stylus 11b comes into contact with the cylindrical portion 6a and the signal is turned ON are stored in the thermal displacement amount storage unit 23 as initial values on the tailstock side. Finish setting.

Next, the setting of the current value of the X-direction thermal displacement at the time when the cutting of the center work W is continuously performed for a predetermined time after the setting of the initial value will be described with reference to the flowchart of FIG. In step S8, the execution data generation unit 22 is instructed to set the present value in the X-axis direction on the headstock side to be in the setting state, and in step S9, the headstock 1 cylindrical portion 1a.
The X-direction thermal displacement measurement reference position of is measured. Then, in step S10, the thermal displacement amount storage unit 23 sets the coordinate values Xxs2, Zxs2 at the time when the stylus 11a comes into contact with the cylindrical portion 1a and the signal is turned on, as the present thermal displacement value in the X-direction on the headstock side.
Save to.

Next, in step S11, the execution data generating section 22 is instructed to set the current value in the X-axis direction on the tailstock side to be set, and in step S12, the sensor 1 is set.
The X-direction thermal displacement measurement reference position of the cylindrical portion 6a of the center 6 is measured with the first stylus 11b. Then, in step S13, the coordinate values Xxc2 and Zxc2 at the time when the stylus 11b comes into contact with the cylindrical portion 6a and the signal is turned on are stored in the thermal displacement amount storage unit 23, and the setting of the current value is completed.

Next, correction of thermal displacement in the X direction will be described with reference to the flowchart of FIG. 5 and with reference to FIG. In step S14, when the operation data generation unit 22 is instructed to correct the X-direction thermal displacement from the operation panel 17 or the NC program input unit 19 to enter the correction state, the thermal displacement storage unit 23.
The initial value and the current value on the spindle side and tailstock side are called, and in step S15, it is confirmed whether or not the X-direction thermal displacement correction is necessary. If YES, in step S16, the execution data generation unit 22 From the Z-axis movement command of the blade T, the X-direction thermal displacement correction value dx for the next movement destination coordinate (Z) is continuously calculated by the following formula 1.

[0016]

[Equation 1] However, dxc = Xxc2-Xxc1. dxs = Xxs2-
XXs1. Next, in step S17, the obtained dx is set as the destination X.
The thermal displacement in the X direction is corrected by adding the axial command value and controlling the axial movement.

Next, the operation of correcting the thermal displacement in the Z direction will be described. This Z-direction thermal displacement correction is almost the same as the above-mentioned X-direction thermal displacement correction, and therefore, a brief description will be made focusing on different points while avoiding duplication of description. As shown in FIG. 7A, the initial values Xzs1 and Zzzs1 of the Z-direction thermal displacement measurement reference position of the end face 1b of the cylindrical portion on the headstock 1 side by the stylus 11a.
And the current values Xzs2 and Zzzs2 after being operated for a predetermined time are measured and stored, and an initial value Xzc1 of the Z-axis thermal displacement measurement reference position of the end face 6b of the cylindrical portion 6b of the center 6 on the tailstock 4 side is measured by the stylus 11b. , Zzc1 and current values Xzc2 and Zzc2 after a predetermined time of operation are measured and stored. Then, the Z-direction thermal displacement correction value dz for the next movement destination coordinate (Z) is continuously calculated from the Z-axis movement command of the blade T by the following equation 2.

[0018]

[Equation 2] However, dxc = Zzz2-Zzz1. Dzs = Zzzs2-
Zzzs1. The dz thus obtained is added to the destination Z-axis command value to perform axis control to correct the thermal displacement in the Z direction. By simultaneously performing the X-direction thermal displacement correction and the Z-direction thermal displacement correction, not only the thermal displacement of the headstock 1 and the tailstock 4 but also the ball screws 12, 1
4. It is possible to perform highly accurate thermal displacement correction including thermal displacement of the tool rest 7, the saddle 9, the bed and the like.

Further, the calculation of dx and dz is not performed during the Z movement (during cutting) of the cutting tool T, but every time the execution data generating unit 22 updates the current value, it is collectively calculated at a predetermined pitch over the entire length of the Z axis. It is also possible to store this in the thermal displacement correction development value storage unit 24, sequentially read the thermal displacement correction values corresponding to the coordinate values of the moving destination of the blade T, and perform the thermal displacement correction at a higher speed. .

Further, the X-direction displacement correction and the Z-direction thermal displacement correction are not limited to being performed at the same time, and when the center work is relatively short or the dimensional accuracy in the Z-axis direction is relatively rough, the X-direction thermal correction is performed. It is possible to use only displacement correction,
In the case of a center work in which the dimensional accuracy in the X-axis direction is relatively rough and the dimensional accuracy in the Z-axis direction is severe, it is possible to perform only the Z-direction thermal displacement correction.

[0021]

Since the present invention is configured as described above, it has the following effects. The amount of thermal displacement in the X-axis direction and / or Z-axis direction on the headstock side and / or tailstock side is measured by a sensor attached to the tool rest, and the thermal displacement correction corresponding to the Z-axis position of the destination of the tool during machining is measured. Since the thermal displacement is corrected by calculating the amount, it is possible to collectively correct not only the headstock, tailstock but also other thermal displacements such as a ball screw, and not only the taper correction but also the heat in the X and Z directions. It is possible to accurately correct the dimensional error due to the displacement.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an NC lathe according to an embodiment.

FIG. 2 is a configuration diagram of a thermal displacement correction device in a center work.

FIG. 3 is a flowchart of an X-direction thermal displacement initial value setting operation.

FIG. 4 is a flowchart of an X-direction thermal displacement current value setting operation.

FIG. 5 is a flowchart of an X-direction thermal displacement correction operation.

FIG. 6A is an explanatory view of an X-direction thermal displacement measuring operation,
(B) is a graph showing the relationship between the Z-axis coordinate value and the X-direction thermal displacement correction value.

FIG. 7A is an explanatory diagram of a Z-axis thermal displacement measurement operation, and FIG.
FIG. 6 is a graph showing the relationship between Z-axis coordinate values and Z-direction thermal displacement correction values.

FIG. 8 is an explanatory diagram of a conventional method for correcting thermal displacement in center work.

[Explanation of symbols]

1 spindle head 2 spindle 3 chuck 4 tailstock 6 center 7 turret 8 turret 10 Z-axis servomotors 10a, 13a detector 11 sensor 11a, 11b stylus 13 X-axis servomotor 22 execution data generator 23 thermal displacement storage Part 26 thermal displacement correction expansion storage part

Claims (1)

[Claims] 1. A thermal displacement amount in the X-axis direction and / or Z-axis direction between a headstock side reference position and a tailstock side reference position separated by a predetermined distance in the Z axis direction is measured by a sensor attached to a tool post, respectively. The thermal displacement rate per unit Z-axis dimension is calculated from the difference in the thermal displacement amounts on the headstock side and tailstock side and the predetermined distance, and the thermal displacement rate is the distance from the reference position when the blade is moved on the Z-axis. X-direction and / or Z-direction thermal displacement correction value corresponding to the Z-axis movement destination of the cutting tool during machining by adding or subtracting the thermal displacement amount on the headstock side or tailstock side to the value obtained by multiplying And a thermal displacement correction method for a center work, which is characterized by continuously calculating in synchronism with cutting feed.