JPH11254273A - Thermal displacement correcting method for feed screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a difference in an entire stroke region by measuring the true value of the total length of a feed screw and distances from machine original points in both ends of the feed screw, obtaining a difference from the true value and deciding an original shifting amount and a pitch error correcting value. SOLUTION: For the moving amount L of a table, a distance to a measuring point O1 slightly away from a machine original point O is L1 , and a distance to a measuring point O2 from the machine original point O is L2 . On the other hand, the difference of the measuring point O1 is -ΔE1 , and the difference of the measuring point O2 is +ΔE2 . Distances to two points, i.e., the measuring point O1 slightly away from the machine original point O and the measuring point O2 from the machine original point close to a stroke end, a difference ±ΔE between the table feeding amount of the true value E and an actual feeding amount is obtained, and an original point shifting amount and a pitch error correcting amount are decided. Thus, a difference in an entire stroke region is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to correction of thermal displacement of a machine tool for correcting an error due to thermal displacement of a feed screw, and more particularly, to measuring distances between two ends of a feed screw from a machine origin to obtain an entire stroke. Is accurately corrected.

[0002]

2. Description of the Related Art Conventionally, a method disclosed in Japanese Patent Application Laid-Open No. 57-114341 has been provided as a method for correcting a thermal displacement of a feed screw in a machine tool.

[0003] JP-A-57-114341 discloses that
The feed amount of the pulse motor is corrected and controlled based on a deviation value between the feed amount of the pulse motor and the reference length of the reference member. When one of the reference members is made to coincide with the origin of the apparatus, the reference length is the position of the other reference member from the processing origin.

However, as described above, when one of the reference members is made to coincide with the origin of the apparatus, the reference length becomes the position from the processing origin of the other reference member, and is determined from the mechanical origin of one end of the feed screw. Is measured, the origin shift amount and the pitch error correction value are determined, and error correction is performed. Therefore, there is a problem that the error correction over the entire stroke cannot be performed accurately and uniformly.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the problem of a correction error in the above-mentioned conventional feed screw thermal displacement correction device, and can correct an error over the entire stroke accurately and uniformly. It is another object of the present invention to provide a lead screw thermal displacement compensating device.

[0006]

According to a first aspect of the present invention, there is provided a method of correcting a thermal displacement of a feed screw, comprising: determining a true value of a total length of the feed screw; Is measured to determine an error from a true value, and an origin shift amount and a pitch error correction value are determined from the error to perform error correction over the entire stroke.

[0007]

According to the first aspect of the present invention, the true value of the total length of the feed screw and the distance from the mechanical origin of the two points at both ends of the feed screw are measured to determine the error from the true value. The origin shift amount and the pitch error correction value are determined from the above error. Thereby, error correction over the entire stroke of the feed screw is performed. Thus, there can be provided a lead screw thermal displacement correction device capable of accurately correcting an error over the entire stroke.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments shown in the drawings will be described. FIG. 1 is a front view of a lead screw thermal displacement correcting apparatus for carrying out the lead screw thermal displacement correcting method of the present invention, and FIG. 2 is a function diagram of the lead screw thermal displacement correcting method of the present invention.

A method for correcting thermal displacement of a lead screw according to the present invention will be described with reference to the embodiments shown in FIGS. First, FIG.
, A table 10 which is one of the moving bodies of the machine tool
Is screwed with a feed screw 12.
The table 10 is moved left and right by the forward and reverse rotations of. At one end of the feed screw 12, a tension bearing 14 is supported. A fixed-side bearing 16 is supported at the other end. Feed screw 1 on the fixed side bearing 16 side
2 is connected to a pulse motor PM. The pulse motor PM controls the feed of the table 10 by a predetermined amount in a designated direction in response to a feed command from the NC control device 20. At this time, if the feed screw 12 is thermally displaced, an error occurs in the amount of movement of the table 10 with respect to the rotation of the pulse motor PM because the length is different from the true length.

The present invention corrects an error in the amount of movement of the table 10. In the table 10, the measurement points (O1) slightly distant from the mechanical origin (O) and the measurement points (O2) slightly before the stroke end (O3) are detected by the position detection sensors S1 and S2 when the table 10 passes. Is detected. The position detection sensors S1 and S2 are composed of limit switches, proximity switches, and the like fixed to the fixed side of the machine main body.
Detected at each of the measurement points (O1) and (O2), a detection signal is sent to the NC controller 20.

FIG. 2 shows the relationship between the movement amount L of the table 10 and each of the measurement points (O1) and (O2).
The movement amount L of the table 10 is defined as follows: (L1) is the distance from the mechanical origin (O) to the measurement point (O1), and (L2) is the distance from the mechanical origin (O) to the measurement point (O2). I do. On the other hand, the error ± ΔE from the true value (E) with respect to the movement amount L of the table 10 is represented by the vertical axis, the error at the measurement point (O1) is −ΔE1, and the error at the measurement point (O2) is + ΔE2 as an error curve E ′.

The error curve E 'represents the distance between two points from the machine origin (O) slightly away from the machine origin (O) and the measurement point (O2) near the stroke end from the machine origin (O). It is obtained by measuring and obtaining an error ± ΔE between the true value (E) and the actual feed amount with respect to the table feed amount, and determines the origin shift amount and the pinch error correction value. As a result, the error can be corrected over the entire stroke.

The configuration of the embodiment for executing the feed screw thermal displacement correcting method of the present invention is as described above. Next, a method for correcting the thermal displacement of the feed screw will be described. First, normal pitch error correction is performed using a laser measuring device or the like. Immediately after the error correction, the distance (L1) from the mechanical origin (O) of the moving body 10 to each measurement point (O1), measurement point (O2),
The measurement of (L2) is performed by the position detection sensors S1 and S2. This is stored as a true value (E).

Next, after or during processing, the moving body 10
Each measurement point (O1) and measurement point (O
The distances (L1 ') and (L2') to 2) are measured by the position detection sensors S1 and S2. This is measured value (E ')
As shown in FIG. Here, (L2′−L2) − (L
1′−L1) / (L2−L1) = ΔL2−ΔL1 / L2
From −L1, ΔL2−ΔL1 / L2−L1 = extension between detection sensors / true distance between detection sensors, and the gradient of the measured value (E ′) is obtained. ΔE = ΔL1− (ΔL
2−ΔL1 / L2−L1) × L1, and the coordinate correction amount at the mechanical origin (O) can be obtained.

The method of correcting thermal displacement of a lead screw according to the present invention measures the true value of the total length of the lead screw and the distance from the mechanical origin of two points at both ends of the lead screw, and calculates the error from the true value. Ask. The origin shift amount and the pitch error correction value are determined from the above error. Thereby, error correction over the entire stroke of the feed screw is performed. Thus, error correction over the entire stroke can be performed with high accuracy.

The present invention is, of course, not limited to the above-described embodiment, and it is needless to say that the design can be freely changed within the scope of the present invention.

[0017]

According to the first aspect, the distance from the mechanical origin of each of the two ends of the feed screw is measured, the error from the true value is determined, and the origin shift amount and the pitch error correction value are determined.
Since the error correction can be performed over the entire stroke of the feed screw, it is possible to perform the error correction over the entire stroke, and it is possible to provide a feed screw thermal displacement correction device that performs the error correction.

[Brief description of the drawings]

FIG. 1 is a front view of a lead screw thermal displacement correcting device for implementing a lead screw thermal displacement correcting method of the present invention.

FIG. 2 is an action diagram of the thermal displacement correction method of the present invention.

[Explanation of symbols]

10 Table 12 Feed screw 14 Tension bearing 16 Fixed bearing 20 NC controller L Movement amount of table L1 Distance from mechanical origin to measurement point L2 Distance from mechanical origin to measurement point L1 ', L2' Actual measured distance E True value E 'Error value O Mechanical origin O1, O2 Measurement point O3 Stroke end PM Pulse motor S1, S2 Position detection sensor

Claims (1)

[Claims] A true value of the total length of the feed screw and a distance from two mechanical ends of the feed screw from the mechanical origin are determined to determine an error from the true value. A method for correcting thermal displacement of a lead screw, comprising determining an error correction value and correcting the error over the entire stroke.