A rapid detection method for critical linearity errors of linear axes in CNC machine tools

Abstract

This invention provides a rapid detection method for critical linear errors of linear axes in CNC machine tools. The method is used to solve for critical linear errors of linear axes in CNC machine tools, including positioning errors and straightness errors. Based on the measurement function of a ballbar, this method ignores angular errors and does not consider the influence of other errors. Detection is performed under two designed circular trajectories. The critical linear errors are expressed and fitted using polynomials, and the coefficients are solved using the least squares method. This method can effectively and quickly obtain the positioning and straightness errors of the linear axis, which is of great significance for improving machine tool accuracy and increasing production efficiency.

Description

Technical Field

[0001] This invention relates to the field of CNC machine tool error detection technology, specifically to a rapid detection method for critical linearity errors of linear axes in CNC machine tools. Background Technology

[0002] The linearity error of a machine tool's linear axis includes positioning error and straightness error, which are significant errors affecting the machine tool's accuracy. Traditionally, laser interferometers are used as measuring tools; however, laser interferometers require a certain level of skill and expertise from the operator, are time-consuming, and are expensive. Summary of the Invention

[0003] This invention is made to solve the above-mentioned problems, and aims to provide a rapid detection method for critical linearity errors of linear axes in CNC machine tools.

[0004] This invention provides a rapid detection method for critical linear errors of linear axes in CNC machine tools, used to solve for critical linear errors of linear axes in CNC machine tools, including positioning errors and straightness errors, and has the following characteristics: The method includes the following steps:

[0005] Step 1: Perform a circle test using a ballbar. On the XOY plane of the ballbar, with the center O of the ballbar as the reference point, use... , Let X and Y represent the error components in the circular trajectory, respectively. Then, according to the spatial error model, ignoring the errors at each rotation angle, we obtain... , The relationship with the critical linear error is as follows:

[0006] (1)

[0007] In equation (1), This represents the positioning error along the X-axis in the X direction. This represents the straightness error in the X and Y directions; both are functions of x. This represents the positioning error in the Y-axis direction. This represents the straightness error in the Y-axis and X-direction; both are functions of y. , , , Both represent the relative change relative to the center O.

[0008] The error term in equation (1) is expressed as a high-order position-dependent polynomial function. To ensure accuracy, the order is generally not less than 5. When the order is 5, the polynomial function is:

[0009] (2)

[0010] In equation (2), a i b i c i d i (i=1,2,3,4,5) are undetermined coefficients.

[0011] Step 2: Select circular trajectories 1 and 2, both with radius R, in the XOY plane as the detection path of the ballbar. The centers of circular trajectories 1 and 2 are denoted as O1 and O2, respectively. The projection length of the line connecting O1 and O2 onto the X and Y axes is equal and equal to 'e'. When the ballbar performs a circular test, the change in bar length corresponding to any point on the circular trajectory is recorded as... If the coordinates are (X, Y), then:

[0012]

[0013] For circular trajectory 1, it is set that a total of n data points are collected during the movement of the ballbar along circular trajectory 1, and the elongation value is recorded. The X and Y coordinates corresponding to each collection point are as follows: , Let the operation matrix , C and C are obtained from the following formulas:

[0014]

[0015]

[0016]

[0017] Similar to circular trajectory 1, for circular trajectory 2, it is set that a total of n data points are collected during the movement of the ballbar along circular trajectory 2, and the elongation value is recorded. The X and Y coordinates corresponding to each collection point are as follows: , Let the operation matrix , They are obtained from the following formulas respectively:

[0018]

[0019]

[0020] Combine ∆R1, ∆R2, and Q1, Q2 using the following formula:

[0021]

[0022]

[0023] And from equations (1), (2), and (3), we get:

[0024] .

[0025] According to the least squares method, the value of C is obtained by the following formula:

[0026]

[0027] Substituting C into equation (2), we get , , , This is the critical linear error of the straight axis.

[0028] The role and effect of invention

[0029] The rapid detection method for critical linearity errors of CNC machine tool linear axes according to the present invention uses a ballbar, which is relatively simple to operate and more inexpensive. Based on the measurement function of the ballbar, this method ignores angular errors and disregards the influence of other errors, performing detection under two designed circular trajectories. The critical linearity error is expressed and fitted using a polynomial, and the coefficients are solved using the least squares method. This method can effectively and quickly obtain the positioning error and straightness error of the linear axis, which is of great significance for improving machine tool accuracy and increasing production efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the ball bar circle test in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of two circular trajectories in an embodiment of the present invention. Detailed Implementation

[0032] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments are described in detail with reference to the accompanying drawings.

[0033] Example

[0034] This embodiment provides a rapid detection method for critical linear errors of linear axes in CNC machine tools. The method is used to solve for critical linear errors of linear axes in CNC machine tools, including positioning errors and straightness errors. Based on the measurement function of a ballbar, this method ignores angular errors and disregards the influence of other errors. It designs two circular trajectory detection paths, expresses and fits the linear errors using a polynomial, and uses the least squares method to solve for the coefficients, quickly obtaining the critical linear errors of the linear axis. The steps of this method are described in detail below.

[0035] Step 1: Perform a circle test using a ball bar.

[0036] Figure 1This is a schematic diagram of a ball bar test for circularity.

[0037] like Figure 1 As shown, in Figure 1 On the XOY plane of the ballbar, with the ball center O of the ballbar as the reference point, the following is used: , These represent the error components in the X and Y directions on the circular trajectory, respectively. According to the spatial error model, ignoring the errors at each rotation angle, we obtain... , The relationship with the critical linear error is shown in equation (1):

[0038] (1)

[0039] In equation (1), This represents the positioning error along the X-axis in the X direction. This represents the straightness error in the X and Y directions; both are functions of x. This represents the positioning error in the Y-axis direction. This represents the straightness error in the Y-axis and X-direction; both are functions of y. , , , Both represent the relative change relative to the center O.

[0040] The error term in equation (1) is expressed as a high-order position-dependent polynomial function. To ensure accuracy, the order is generally not less than 5. When the order is 5, the polynomial function is equation (2):

[0041] (2)

[0042] In equation (2), a i b i c i d i (i=1,2,3,4,5) are undetermined coefficients.

[0043] Step 2: Select circular trajectories 1 and 2 with radius R in the XOY plane as the detection paths of the ballbar instrument.

[0044] Figure 2 It is a schematic diagram of two circular trajectories.

[0045] like Figure 2 As shown, the centers of circular trajectory 1 and circular trajectory 2 are denoted as O1 and O2, respectively. The projection length of the line connecting O1 and O2 on the X-axis and Y-axis is equal and is e.

[0046] When the ball-and-stick instrument performs a circular test, the change in rod length corresponding to any point on the circular trajectory is recorded as follows: Let the coordinates be (X, Y), then we get equation (3):

[0047]

[0048] For circular trajectory 1, it is set that a total of n data points are collected during the movement of the ballbar along circular trajectory 1, and the elongation value is recorded. The X and Y coordinates corresponding to each collection point are as follows: , Let the operation matrix , C and C are obtained from the following formulas:

[0049]

[0050]

[0051]

[0052] Similar to circular trajectory 1, for circular trajectory 2, it is set that a total of n data points are collected during the movement of the ballbar along circular trajectory 2, and the elongation value is recorded. The X and Y coordinates corresponding to each collection point are as follows: , Let the operation matrix , They are obtained from the following formulas respectively:

[0053]

[0054]

[0055] Next, a polynomial fitting is performed, and ∆R1, ∆R2, Q1, and Q2 are combined according to the following formula:

[0056]

[0057]

[0058] Furthermore, from equations (1), (2), and (3), we obtain:

[0059]

[0060] According to the least squares method, the value of C is obtained by the following formula:

[0061]

[0062] Substituting C into equation (2), we get , , , This refers to the critical linear error of the straight axis.

[0063] This method is also applicable to the identification of critical linearity errors in the Y and Z axes of machine tools.

[0064] The role and effect of the embodiments

[0065] The rapid detection method for critical linear errors of CNC machine tool linear axes described in this embodiment utilizes a ballbar, which is relatively simple to operate and less expensive. Based on the ballbar's measurement capabilities, this method ignores angular errors and disregards the influence of other errors, performing detection along two designed circular trajectories. The critical linear errors are expressed and fitted using polynomials, and the coefficients are solved using the least squares method. This method effectively and quickly obtains the positioning and straightness errors of the linear axis, which is of great significance for improving machine tool accuracy and increasing production efficiency.

[0066] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A fast detection method of key linear errors of a linear axis of a numerical control machine tool, for solving key linear errors of a linear axis of a numerical control machine tool, the linear errors including positioning errors and straightness errors, characterized in that, Comprising the following steps: Step 1, using a ball bar to perform circle test, on the XOY plane of the ball bar, taking the ball center O of the ball bar as a reference point, using 、 respectively represent the error components of X, Y directions on the circle track, and then according to the spatial error model, ignoring each angle error, the relationship formula of 、 and the key linear error is obtained. （1） In formula (1), represents a positioning error in the X-axis X direction, represents a straightness error in the X-axis Y direction, both of which are functions of x, represents a positioning error in the Y-axis Y direction, represents a straightness error in the Y-axis X direction, both of which are functions of y, , , , all represent relative change amounts with the center O as a reference, The error term in formula (1) is expressed as a polynomial function of high-order position correlation, and the order is not less than 5 to ensure accuracy, and when the order is 5, the polynomial function is: （2） In formula (2), a i , b i , c i , d i (i = 1, 2, 3, 4, 5) are undetermined coefficients; Step 2, selecting a circular trajectory 1 and a circular trajectory 2 with a radius R as the detection path of the ball instrument in the XOY plane, the centers of the circular trajectory 1 and the circular trajectory 2 are respectively denoted as O1 and O2, and the projection length of the line connecting O1 and O2 on the X axis and the Y axis is equal and e, When the club tester makes a circle test, the change of the club length at any point on the circle is recorded as , the coordinates are recorded as (X, Y), and the following equation is obtained: ， For the circular trajectory 1, n data are collected during the movement of the ball instrument along the circular trajectory 1, and the elongation value is recorded as , the X and Y axis coordinates corresponding to each collection point are respectively , , and the operation matrix , , C is obtained by the following formula respectively. ， ， ， The same as the circular trajectory 1, for the circular trajectory 2, n data are collected during the movement of the ball instrument along the circular trajectory 2, and the elongation value is recorded as , the X and Y axis coordinates of each collection point are respectively , , and the operation matrix , is obtained by the following formula respectively. ， ， ∆R1, ∆R2, Q1 and Q2 are combined as follows: ， ， And from formula (1), (2), (3): ， According to the least square method, the value of C is obtained by the following formula: ， Substitute C into equation (2), we get , , , , which is the key linear error of the straight line shaft.

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