JPH0565083B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for simultaneously and highly accurately measuring the straightness of an object to be measured, the straightness of a moving guide surface, and the amount of pitch during movement. [Prior Art] The present invention relates to an improvement of Japanese Patent Application No. 57-167561 "Straightness Measuring Method" which has already been proposed by the present applicant and others. In recent years, with the increasing demand for higher precision in machine tools, the straightness control of guide surfaces (sliding surfaces) has become one of the important issues, and it is desired to make its measurement easier. Conventional methods for measuring straightness include using a reference bar such as Straight Edge, a piano wire as a reference straight line, or using an autocollimator. A system-based method has also been developed. However, all of these methods require a considerable amount of preparation and skill for measurement work, are inefficient, and are susceptible to adverse effects from various noises, etc., making them difficult to put to practical use in the field. Many problems remain. Therefore, as a new method for measuring straightness that can solve these problems, three displacement detectors are moved along the object to be measured, and the straightness and displacement of the object to be measured are sequentially calculated from the measured values by these displacement detectors. A method for simultaneously measuring the straightness of the moving guide surface of the detector is reported in Japanese Patent Application No. 167561/1983. As shown in Figure 1, which shows the principle, this is because the distance between the detector mount 3 (using a knife mount, for example) that moves along the measurement object 1 on the guide surface 2 and the measurement object 1 is Three displacement detectors A, B, and C that measure This is a method in which the measured values of three displacement detectors A, B, and C are obtained for each moving distance l, and the straightness of the object to be measured 1 and the straightness of the guide surface 2 are calculated separately from these measured values. . In other words, the measurement target 1 at the measurement start position
and the straightness of the guide surface 2 are Y ₀ and X ₀ respectively,
Let the straightness at the Kth measurement position be Y _K and
If X _K , then the straightness curves of the object to be measured 1 and the guide surface 2, respectively indicated by Y and ). Here, the displacement detector A at the Kth measurement position,
The measured values at B and C are D _KA , D _KB , D _KC (K=0, 1,
2,...), the following equations (1), (2), and (3) hold true. D _KA −Y _K −X _K =D _OA …(1) D _KB −Y _K+1 −X _K −l・θ _K =D _OB −Y ₁ −X ₀ …(2) D _KC −Y _{K +2} −X _K −2l・θ _K = D _OC −Y ₂ −X ₀ ...(3) However, θ _K is the detector mounting base 3 as shown in the figure.
pitching amount. By transforming equations (2) and (3) into 2×(2)−(3), the following equation (4) is obtained. _{2D KB −D KC = _ _ _}
By substituting Y _K+1 and Y _K+2 obtained by , into equation (4), the following equation (5) is obtained. _{X K + 2 = 2 . _ _ _} Obtained from equation 5) and equation (1)
The following equations (6) and (7) are obtained by Y _K+2 . Y _K+2 ＝−X _K+2 ＋D _K+2A ……(6) θ _K+2 ＝−X _K+2 −Y _K+3 ＋D _K+2B ＋X ₀ ＋Y ₁ /l ……(7) However , (4) to (7), the measured values D _OA , D _OB , and D _OC of each displacement detector A, B, and C at the measurement start position were set to 0. In this way, using the measured values D _KA , D _KB , and D _KC of the displacement detectors A, B, and C at the positions of K=0, 1, 2, and so on, the above equations (5), (6), and ( 7) From equation 1, straightness curve Y of measurement object 1, straightness curve X of guide surface 2
And the pitching θ of the detector mount 3 can be calculated. However, in the above calculation method, X ₀ , X ₁ ,
Y ₁ and Y ₂ are values that cannot be obtained from the recurrence formulas of equations (5) and (6), and in order to obtain the straightness curves X and Y, these values must be estimated by some method. or its influence must be removed.
As a method for this purpose, the following method is proposed in Japanese Patent Application No. 167561/1983. That is, in equation (5), X ₁ = α, 2Y ₁ −Y ₂
=β, X ₀ =γ, the following equation (8) holds true. X _K = K・(α−γ)+K(K−1)/2 ・(β+γ)+C _K ……(8) (K=2, 3,…) X _K : Straightness error at Kth position (True value) C _K : Straightness error at the Kth position (calculated value) Also, assuming that α=β=γ=0 _, (5)
This is the value of X _K determined by the formula. Here, if we consider the straightness error as ``the deviation from the virtual straight line that minimizes the root mean square value of the error at each measurement point,'' then we can use the least squares method to calculate the square mean of X _K. α such that the value is minimized,
Find β and γ and use these α, β, γ and C _K to
X _K can be found using equation (8). and
Find Y _K from X _K and equation (6). According to the conventional technology as described above, the measurement object 1
The straightness of the moving guide surface 2, the straightness of the moving guide surface 2, and the amount of vertical wobbling during movement can be determined simultaneously. [Problem to be solved by the invention] However, as can be seen from the above equation (8), the component proportional to K ² included in the straightness shape of the moving guide surface,
That is, for a component that can be expressed as X _K =b·K ² , the coefficient b is included in (β−γ) in equation (8) and evaluated, making it impossible to correctly determine the component. This will be explained with reference to FIG. 2 and Table 1. Note that the component proportional to K, that is, X _K =
For the component that can be expressed as a・K, (α
−γ). However, since this method considers the straightness error as a deviation from a certain virtual straight line, this does not affect the evaluation of the straightness shape. Now, FIG. 2 shows the simulated data and calculation results, and Table 1 shows the input data and calculation results at that time. In addition, the marks in FIG. 2 are simulated data, and the marks ○ indicate the calculation results in Table 1.

[Means for solving problems]

The means to achieve this objective are as follows. (i) Either the detector mount or the object to be measured moves along the guide surface, and the three detectors for measuring the distance from the object to be measured are moved to the detector mount, which moves along the guide surface. (ii) With the three detectors placed on the detector mount, measure the amount of separation from a sufficiently straight reference object, and then Calculate the amount C (≡D _A + D _C -2・D _B ) determined by the mounting state of the detector from the measured values D _A , D _B , and D _C of the three detected amounts A, B, and C, and calculate ( iii) moving the detector mount or the object to be measured every interval l and obtaining the measured value each time;
The measured values at the measurement start position are D _O,A , D _O,B ,
Let D _O,C be the values at the Kth measurement position, and let the values at the Kth measurement position be D _K,A , D _K,B , and D _K,C , and from the measured values and the above value C, a _K = D _K,A + D _K, Obtain the value _C −2・D _K,B /2−C, and average value of a _K for K=0, 1, 2,...N=
_N 〓 ^K=1 ak/(N+1), (iv) These measured values D _K,A , D _K,B , D _K,C (K=0,
1, 2, ...), the straightness shape of the guide surface X _K (K=0, 1,
2,...) and the straightness shape of the object to be measured Y _K (K=
0, 1, 2, ...), and (v) For example, by the least squares method, find the curve Y _K = to which the shape of the object to be measured Y _K most likely fits.
Find a′・K ² +b′・K+c′, (vi) Y _K ′=Y _K −(a′−)・K ² ……(9) Find the straightness shape Y _{K ′} of ^the object to _be measured and the straightness shape X _K ′ of the guide surface as follows: [Examples] Examples of the present invention will be described below. As can be seen from Figure 1, the Kth, (K+1)
The following relationships hold between the shapes of the object to be measured Y _K , Y _K+1 , Y _K+2 at the (K+2)th and (K+2)th measurement positions and the measured values at each detector. Y _K −2・Y _K+1 +Y _K+2 =D _K,A −2・D _K,B +D _K,C −2・C ……(11) On the other hand, Y _K =a _K・K ² +b _K・If K+C _K , the following relationship holds true. Y _K −2・Y _K+1 +Y _K+2 =2・a _K ...(12) From equations (11) and (12), the shape of the object to be measured Y _K (K=0,
The coefficient a _K of the component proportional to K ² in 1, 2, ...) is a _K = D _K,A +D _K,C -2.D _K,B /2-C (3). Obtained at measurement positions of K=0, 1, 2,...
a The average value of _K is a component proportional to K ² over the entire measurement range. If only the shape component proportional to K ² is considered, the straightness shape Y _K of the object to be measured obtained according to the steps of equations (1) to (8) will be determined by the fact that the shape of the guide surface is equal to the true shape of the object to be measured. This component a′・K ² is subtracted from the calculation result according to the steps of equations (1) to (8), and the true component・K obtained by the procedure of the present invention is All you have to do is add ² . Similarly, the true guide surface straightness shape can be found using equation (10). [Effects of the Invention] As explained above, according to the present invention, even when the straightness shape error of the movable guide surface includes a component proportional to K ² , the influence can be corrected and the measurement target can be corrected. The straightness of an object, the straightness of a moving guide surface, and the amount of vertical wobbling during movement can be simultaneously measured with high precision. In addition, it is only necessary to install three detectors for measurement, and it can be easily applied to actual equipment, and the measurement work is simple and does not require any skill.

[Brief explanation of the drawing]

Figure 1 is a principle diagram of the straightness measurement method, Figure 2
The figure shows a straightness curve showing simulated data and calculation results.
It is a graph of X _K , Y _K , and pitching θ _K . In the drawings, 1 is an object to be measured, 2 is a guide surface, 3 is a detector mounting base, and A, B, and C are displacement detectors.

Claims (1)

[Claims] 1. Either the detector mount or the object to be measured moves along a guide surface, and the detector mount is provided with three detectors for measuring the distance to the object to be measured. The three detectors are installed at equal intervals l in the movement direction, and the measured values of the three detectors at the measurement start position are respectively
D _OA , D _OB , D _OC , the detector mounting base or the object to be measured is moved every interval l to obtain the measured value of the detector each time, and the measured value at the Kth measurement position is respectively Let D _KA , D _KB , and D _KC be the guide surface straightness error at the measurement start position as X ₀ , that at the first position as X ₁ , and the straightness error of the object to be measured at the first position as Y ₁ , that in the second position
Let Y _{2 be} the straightness of _the guide surface at the _{K + 2nd position .}
-D _KC + 2Y _{1 -Y 2 +} Find X ₀ , X ₁ and
The straightness X _K , (K=0, 1, 2,...) of the guide surface is estimated and calculated by correcting it with the values related to Y ₁ and Y ₂ , and the straightness of the measurement target at this position is calculated. Calculate the degree Y _K+2 by Y _K+2 = −X _K+2 +D _K+2A , and with the three detectors mounted on the detector mount, make sure that the standard is sufficiently straight. Measure the amount of separation from the object, and then measure A, B,
From the measured values D _A , D _B , D _C at C3 detectors, C=
Find the value D _A +D _C -2・D _B , and calculate the above K=0, 1,
2. Measured value with the detector at the measurement position of...
From D _K,A , D _K,B , D _K,C and the above value C, we obtain the value a _K = D _K,A + D _K,C −2・D _K,B /2−C, and K = Average value of a _K for 0, 1, 2,... = _N 〓 ^K=1
Find a _K / (N+1) and find the curve to which the straightness shape of the measured object Y _K (K=0, 1, 2,...) calculated above most likely applies: Y _K = a′・K ² +b′・_K +c ′ is determined and measured as Y _K ′=Y _K −(a′−)・K ² X _K ′=X _K +(a′−)・K ² using the coefficient a′ of the curve and the above value. A straightness shape measuring method characterized by determining the straightness shape Y _K ′ of an object and the straightness shape X _K ′ of a guide surface.