Method for measuring geometric accuracy error of linear shaft of numerical control machine tool in machine and automatically compensating geometric accuracy error of linear shaft of numerical control machine tool

Abstract

The invention belongs to the field of detection of large and ultra-large numerical control machine tools, and provides a method for measuring geometric accuracy errors of linear axes of a numerical control machine tool in a machine tool and automatically compensating the geometric accuracy errors, which comprises the following steps of: mounting a tilt angle sensor on a tool rest of the machine tool, and taking a position value of an axis, namely an X axis, which causes errors of straightness of another axis, namely a Z axis as an independent variable; the X-axis position is equidistantly moved, at each fixed equidistant X position, the included angle between the cross beam guide rail and the workbench plane is measured in real time through the tilt angle sensor, the straightness error value of the vertical axis is calculated, the process is repeated, and the error value calculation result of the Z-axis is stored in the numerical control system. And establishing a piecewise function of the X-axis position value and the Z-axis error value, and taking a dependent variable, namely a Z-axis compensation value, of the piecewise function as an additional given value of the Z-axis servo motor. According to the method, the straightness error of the vertical shaft is automatically measured, the error value is automatically compensated to the numerical control system, and the aim of compensating the straightness error of the numerical control machine tool is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of large and super-large CNC machine tool detection, and specifically relates to a method for measuring the geometric accuracy error of the linear axis of a CNC machine tool in a machine and automatically compensating for it. The method is suitable for situations where the linear axes of the CNC machine tool have linear errors due to various reasons and linear accuracy compensation is required. Background Art

[0002] With my country's continuous investment in the field of extreme manufacturing, the demand for large and super-large CNC machine tools has emerged. In order to meet the requirements of large-stroke processing capabilities of large and super-large machine tools, the crossbeams of machine tools are designed to be movable, and the moving stroke of the crossbeam is used to expand the processing range of the machine tool turret to achieve the purpose of super-large processing range of the machine tool. However, when the machine tool crossbeam moves vertically, due to the geometric size errors of the mechanical transmission parts that drive the crossbeam to move, mechanical wear due to long-term movement, etc., the crossbeam guide surface is no longer horizontal with the plane of the machine tool worktable, and the crossbeam guide surface will form an angle with the plane of the machine tool worktable, thereby causing errors in the straightness of the vertical axis moving on the crossbeam, and each time the crossbeam moves to a different position, the angle between the crossbeam guide surface and the plane of the worktable may change. In order to offset the influence of the horizontal beam on the straightness accuracy of the tool holder's vertical axis caused by the non-parallelism of the worktable, the traditional method is to use a long ruler that can cover the moving range of the machine tool's horizontal axis, make the long ruler parallel to the plane of the machine tool's worktable, and manually measure the straightness error value of the vertical axis caused by the unevenness of the horizontal beam by moving the horizontal axis, and then compensate the measured error value to the CNC system. Once the beam moves a certain distance, in order to maintain the geometric accuracy of the machine tool, the error value of the machine tool's vertical axis must be manually measured again, which is time-consuming and labor-intensive. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to propose a method for measuring the geometric accuracy error of the linear axis of a CNC machine tool in a machine and automatically compensating for it. The method automatically measures the straightness error of the vertical axis and automatically compensates the measured error value to the CNC system, thereby achieving the purpose of compensating the straightness error of the CNC machine tool and enhancing the accuracy retention of the machine tool.

[0004] In order to achieve the above technical objectives, the protection scheme provided by the present invention is as follows.

[0005] The invention provides a method for measuring the geometric accuracy error of the linear axis of a numerical control machine tool in a machine and automatically compensating for it. An inclination sensor is installed on a tool holder of the machine tool, and the position value of an axis, namely an X-axis, which causes the straightness error of another axis, namely a Z-axis, is used as an independent variable. By moving the X-axis position at equal intervals, the angle between a beam guide rail and a worktable plane is measured in real time at each fixed and equal-distance X position by the inclination sensor. The straightness error value of the vertical axis is calculated by using the trigonometric function principle. The above process is repeated, and the error value calculation result of the Z-axis is stored in a numerical control system. Then, a piecewise function of the X-axis position value and the Z-axis error value is established, and the dependent variable of the piecewise function, namely a Z-axis compensation value, is used as an additional given value of a Z-axis servo motor to drive the Z-axis motor to move, thereby achieving the purpose of compensating the straightness error of the numerical control machine tool.

[0006] The method for measuring the geometric accuracy error of the linear axis of a CNC machine tool in-machine and automatically compensating for it is simple, convenient and quick to operate. The position value error of the Z-axis is measured in the machine, and then a functional relationship model between the X-axis position and the Z-axis straightness error is established. The Z-axis straightness error compensation value is converted into a motion instruction of a Z-axis servo motor, and the Z-axis servo motor is driven to move, so as to compensate for the Z-axis straightness error caused by the movement of the X-axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a schematic diagram of the compensation method of the present invention.

[0008] Figure 2 This is a flow chart of the compensation method of the present invention.

[0009] Among them: 1. Inclination sensor, 2. Machine tool turret, 3. Machine tool column, 4. Crossbeam guide, 5. Workbench. DETAILED DESCRIPTION

[0010] In order to facilitate the understanding of the present invention, the following further describes the implementation of the present invention in conjunction with the accompanying drawings and examples. An implementation of the present invention is shown in the accompanying drawings. It should be understood that this embodiment is only used to explain the present invention and is not intended to limit the present invention. The purpose of providing this embodiment is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0011] The embodiment of the present invention provides a method for measuring the geometric accuracy error of a linear axis of a CNC machine tool in a machine and automatically compensating for the same. Figure 1As shown, the method installs an inclination sensor 1 on the tool holder 2 of the machine tool, takes the position value of the axis that causes the straightness error of another axis, namely the Z-axis, as the independent variable, moves the X-axis position at equal intervals, and at each fixed and equal-distance X position, measures the angle between the crossbeam guide 4 and the plane of the worktable 5 in real time through the inclination sensor 1, calculates the straightness error value of the vertical axis, repeats the above process, stores the error value calculation result of the Z-axis in the CNC system, and then establishes a piecewise function of the X-axis position value and the Z-axis error value, and uses the dependent variable of the piecewise function, namely the Z-axis compensation value, as an additional given value of the Z-axis servo motor to drive the Z-axis motor to move, thereby achieving the purpose of compensating the straightness error of the CNC machine tool.

[0012] like Figure 2 As shown, the method specifically comprises the following steps:

[0013] (1) Divide the X-axis travel into n equally spaced regions, where n is greater than or equal to 1 and is an integer. The equal distance value is named Step;

[0014] (2) Move the X-axis to the starting point of the compensation interval and record the inclination value of the inclination sensor at this time, which is denoted as α 0 ;

[0015] (3) Move the X axis to the end point of the first compensation interval and record the inclination value of the inclination sensor relative to α 0 The difference between them is used to calculate the position error of the Z axis using formula 1, which is recorded as E 0 ;

[0016] E=tanα*Step Formula 1

[0017] (4) Repeat step (3) and record the difference between the inclination value of the inclination sensor and the inclination value of the previous inclination sensor when the X-axis moves to the starting point of each area, recorded as α n , calculate the position error value of the Z axis in each area through formula 1, denoted as E n , until the X axis reaches the end of the travel;

[0018] (5) Take the X-axis coordinate value of each area of ​​the X-axis travel as the independent variable and the corresponding Z-axis straightness error compensation value as the dependent variable, and calculate it according to the formula of the two-piece function

[0019]

[0020] Formula 2 Z comp is the current straightness compensation value of the Z axis, pos is the current machine coordinate system position value of the X-axis, Step is the equidistant interval value of the X-axis movement, P 0 is the starting point value of the first area of ​​the X-axis, P jIt is the end point position value of the last area of ​​the X axis;

[0021] (6) The calculated Z comp The value is output to the CNC system, and the CNC system drives the corresponding servo motor to complete the straightness error compensation of the corresponding axis of the CNC machine tool.

[0022] The compensation method mentioned in the present invention is not only applicable to the compensation between the X-axis and the Z-axis, but also can be used to compensate for the straightness of any linear axis that is perpendicular to each other on a CNC machine tool.

[0023] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0024] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention should be considered to belong to the protection scope of the present invention.

Claims

1. A method for measuring the geometric accuracy error of a linear axis of a CNC machine tool and automatically compensating it, characterized in that: The method installs an inclination sensor on the tool holder of the machine tool, takes the position value of the axis that causes the straightness error of another axis, namely the Z-axis, as the independent variable, moves the X-axis position at equal distances, and measures the angle between the crossbeam guide and the worktable plane in real time at each fixed and equal-distance X position through the inclination sensor, calculates the straightness error value of the vertical axis, repeats the above process, stores the error value calculation result of the Z-axis in the CNC system, and then establishes a piecewise function of the X-axis position value and the Z-axis error value, and uses the dependent variable of the piecewise function, namely the Z-axis compensation value, as an additional given value of the Z-axis servo motor to drive the Z-axis motor to move, thereby achieving the purpose of compensating the straightness error of the CNC machine tool.

2. The method for measuring the geometric accuracy error of the linear axis of a CNC machine tool and automatically compensating it according to claim 1 is characterized in that The method specifically comprises the following steps: (1) Divide the X-axis travel into n equally spaced regions, where n is greater than or equal to 1 and is an integer. The equal distance value is named Step; (2) Move the X-axis to the starting point of the compensation interval and record the inclination value of the inclination sensor at this time, which is recorded as α0; (3) Move the X-axis to the end point of the first compensation interval, record the difference between the inclination value of the inclination sensor and α0 at this time, and calculate the position error value of the Z-axis using Formula 1, which is recorded as E0; E=tanα*Step Formula 1 (4) Repeat step (3) and record the difference between the inclination value of the inclination sensor and the inclination value of the previous inclination sensor when the X-axis moves to the starting point of each area, recorded as α n , calculate the position error value of the Z axis in each area through formula 1, denoted as E n , until the X axis reaches the end of the travel; (5) Take the X-axis coordinate value of each area of ​​the X-axis travel as the independent variable and the corresponding Z-axis straightness error compensation value as the dependent variable, and calculate it according to the formula of the two-piece function Formula 2 Z comp is the current straightness compensation value of the Z axis, X pos is the current machine coordinate system position value of the X-axis, Step is the equidistant interval value of the X-axis movement, P0 is the starting position value of the first area of ​​the X-axis, P j It is the end point position value of the last area of ​​the X axis; (6) The result of Formula 2 is output to the CNC system, and the CNC system drives the corresponding servo motor to complete the straightness error compensation of the corresponding axis of the CNC machine tool.

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