JPS60107512A - Measuring method of straightness - Google Patents

Abstract

PURPOSE:To measure straightness accurately by arranging three detectors which measure the distance from an object of measurement on a detector mount base at equal intervals, and processing detected values as specified and calculates the straightness and longitudinal undulation extent of a movement guide surface separately. CONSTITUTION:Three detectors A, B, and C obtain detected values D0A, D0B, and D0C and move at intervals (l) to obtain measured values Dk+iA, Kk+iB, and Dk+iC at the (k+i)th position. When a guide surface straightness error at a measurement start position is denoted as X0 and the straightness error of the object of measurement at the 1st position is represented as Y1, YK+2=2.Yk+1+ DKA-2.DKB+DKC-2.Y1+Y2. The values of YK+2 calculated by K=0, 1, 2... are corrected with numerals relative to X1, Y1, and Y2 found so that the mean of square of the straightness error is minimum. The longitudinal undulation extent at this position and the straightness of the guide surface are calculated and substituted in said equation, and then YK=K.alpha'-K(K-1)/2.beta'+C'K (K=2, 3, 4...), where alpha'=Y1, beta'=2Y1-Y2, and C'K is YK when alpha'=beta'=0.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of a method that can simultaneously measure the straightness of an object to be measured, the straightness of a moving guide surface, and the amount of pitching (pitting amount) during movement. With the increasing demand for higher precision in the guideway (sliding surface)
One of the important issues is controlling the straightness of the machine and understanding the straightness shape of the workpiece. Conventional methods for measuring straightness include using a reference bar such as Straight Esso, a piano wire as a reference straight line, or using an autocollimator. Methods using systems have also been developed.

However, all of these methods require a considerable amount of preparation and skill for the measurement work, and have the drawbacks of being inefficient and susceptible to negative effects from various noises, etc.
Many problems remain in terms of practical application in the field.

As a new method for measuring straightness that can solve these problems, we move displacement detectors (3) along the object to be measured, and sequentially calculate the straightness and displacement of the object from the measured values by these displacement detectors. The present inventors have reported a method for simultaneously measuring the straightness of the moving guide surface of the detector. (
(Japanese Patent Application No. 57-167561 r Straightness Measuring Method) As shown in the diagram showing the principle, this method is based on a detector mount 3 (for example, a cutter mount) that moves on a guide surface 2 along a measuring object 1. ), three displacement detectors A and B are used to measure the distance to the object to be measured 1.

ct, the detector mounts 3 are placed in parallel at a fixed distance l in the direction of movement, and the detector mounts 3 are moved in the direction of the arrow in the figure to remove three displacement detectors A for every moving distance l; In this method, the measured values of B and C are obtained, and the straightness of the object to be measured 1 and the straightness of the guide surface 2 are separated and calculated from these measured values one after another.

That is, the straightness errors of the measurement object 1 and the guide surface 2 at the measurement start position are YO and X, respectively.

If the straightness error at the K-th measurement position is YK I XK, then the straightness curves of the measurement object 1 and the guide surface 2, respectively indicated by Y and X in FIG. 1, are obtained. (For simplicity, each section is approximated by a straight line in the figure.) The measurement value from each displacement detector is a superimposition of Y, X, and the amount of pitching (pitting amount) during movement. However, by processing the 611j constant values of the three displacement detectors A, B, and C using the method shown in % Application No. 57-167561, it is possible to separate and extract Y and X at the same time. .

An outline of the calculation processing method will be explained below. The measured values of displacement detectors A, B, and C at the Kth measurement position are DKA r
DK, B + DKO (K” Or 1 + 2 +
), then the following equations (1), (2), (
3) holds true.

DKA-YK-XK=DOA・--” (1)
DKB YK+I XK l”θ=DOB Y+ −
--(2) DKO-YK+2-XK-2°t@0K=D
00-Y, Curve --- (3) However, θ is the pitching amount of the detector mount 3 at the second measurement position. Also,
In FIG. 1, = Yo = o, and xi and yi are quantities evaluated as differences from Xo and Yo, respectively.

From formulas (1), (2), f3), (4) and (5), although the details are omitted.

Equation (6) is obtained.

XK+2 ”' 2・XK+1− XK−2・DK+I
A +DK+2A+ 2 ・DKB-Q<(3+';h
Ys Yt '・' (4) YK+2 =XK+2 +
DK+2A ・・・・・・・・・(5)XK+2 Y
K+3 + DK+2 Bθ +2−− 'Mountain゛−−−
- (6) However, displacement detectors A and B at the measurement start position.

The measured value of C DOA r DOB , Doa was set to O.

Displacement detector A at positions K=0, 1, 2,...
,B.

Using the measured value of C DKA + DKB + DKO,
(4) above.

From equations (5) and (6), the straightness curve of guide surface 2
, the straightness curve Y of the measurement object 1 and the pitching θ of the detector mount 3 can be calculated.

However, the values on the right side of X, Y, are values that cannot be fitted from the recurrence formulas of equations (4) and (5), and the straightness curve X,
In order to reduce Y, it is necessary to estimate these values by some method or remove their influence. As a method for this purpose, Japanese Patent Application No. 57-167561 proposes the method described below. In formula (4), = α, 2Y
When + Yt = β, the following equation (7) holds true.

(K = 2.3, 4...) CK: Aya Q value obtained from equation (4) assuming α = β - If we consider it as a deviation from the virtual straight line that minimizes the value, we can find α, β that minimizes the root mean square value of
XK can be calculated using equation (7). x
YK can be calculated from K and equation (5).

As explained above, according to the method of Japanese Patent Application No. 57-167561, the straightness shape of the object to be measured 1, the straightness shape of the movement guide surface 2, and the amount of vertical wobbling during movement of the detector mount 3 can be calculated. Both can be measured at the same time in one measurement. As can be seen from the calculation procedure, this method has the following characteristics.

(2) No matter how the object to be measured 1 moves, if it moves as a rigid body, the accurate straightness shape of the object can be determined.

(Evaluation is performed by transferring the movement of the measurement object to the straightness shape of the moving guide surface and the vertical sway when the detector mount is moved. Therefore,
At this time, the straightness of the moving guide surface and the vertical sway of the detector mounting base were not real. ) In view of the above-mentioned prior art (Japanese Patent Application No. 57-167561), it is an object of the present invention to provide a method capable of accurately measuring the straightness of a moving guide surface. The configuration of the present invention that achieves this objective is as follows:
Either the detector mount or the object to be measured moves along a guide surface, and three detectors for measuring the distance to the object are placed at equal intervals in the moving direction! The measured values of the three detectors at the measurement start position are respectively DOA+DOB+I)oo, and the detector mounting joint or the object to be measured is spaced at the distance ! the measured values of the detector are obtained each time, and the measured values at the first measuring position are DKA, DKB, and DK, respectively.
O, and the measured value at the +i-th position is DK+lA
, DK+lB, D[4iQ, the guide surface straightness error at the measurement start position, and that at the first position as Xl
, the straightness error of the object to be measured at the first position is Y8.2
The straightness error YK+2 of the object to be measured at the +2nd position is defined as YK+2=
2 ・YK+z -YK +DKA -2-DKB+
Calculated by DKO-2・Yt +Yt, I(=O,
],,2. The value of YK+2 calculated for . is estimated and calculated, and +2 is calculated for the straightness XK+2 of the movement guide surface at this position and the amount of vertical wobbling θ in the longitudinal direction due to the movement, respectively, by XK+2''-YK+2+DK+2A.

A straightness measuring method according to an embodiment of the present invention will be described below.

When formulas (1), (2), and (3) are rearranged for YK, we get (8) and (9).

α0) formula is obtained.

YK+2""2'YK+I YK+DKA 2'DKB
+DKOz・y1+y,...(a)XK+2" -Y
K+2 + DK+2A ”°°゛°“°(91(8)
If we set Y, =α', zy, y, ==β' in the equation, the following equation (II) holds true.

(K = 2.3, 4...) CIK: Y calculated from equation (8) assuming α' = βl-o
f) Value Here, α' and β' can be determined using the same procedure as described above, and YK can be determined from Equation 60 using α', β', and α'K.

The method described above has the following features compared to the method proposed in Japanese Patent Application No. 57-167561.

(2) No matter how the object 1 to be measured moves, if it moves as a rigid body, the accurate straightness shape of the moving guide surface can be determined.

(The movement of the object to be measured is evaluated by transferring it to the straightness shape of the object to be measured and the vertical sway when the detector mount is moved. (The amount of pitching is not the real value.) As explained above, according to the method of the present invention.

No matter how the object to be measured moves during measurement using the method shown in the figure, if it moves as a rigid body, the accurate straightness shape of the moving guide surface can be determined. The method of the present invention is extremely effective when applied to measuring the straightness shape of a moving guide surface under such conditions. Note that when the object to be measured is stationary, it is of course possible to accurately determine the straightness and shape of the object to be measured and the moving guide surface by the method of Japanese Patent Application No. 57-167561 or by the method of the present invention. be.

[Brief explanation of the drawing]

The figure is an explanatory diagram for explaining the method of the present invention. In the drawing, 1 is the object to be measured, 2 is the information surface, 3 is the detector mounting base. A, B, and C are displacement detectors.

Claims (1)

[Scope of Claims] Three detectors for measuring the distance to the object to be measured are installed on the detector mount, in which one of the detector mount and the object to be measured moves along a guide surface. Equally spaced in the direction of movement! The measurement values of the three detectors at the measurement start position are set as DOA + DOB + 'DOO, respectively, and the detector attachment point or the object to be measured is set at the interval ! The measured value of the detector is obtained each time, and the measured value at the Kth measuring position is DKA +DKB+.
I) ico, and the measured value at +i-th position sequentially is D
K+I A + DK+ f B r DK+ i 0
In addition, to account for the guide surface straightness error at the measurement start position,
The straightness error of the measuring object at the first position is Xl, the straightness error of the measuring object at the first position is Yl, the straightness error of the measuring object at the second position is Y2, and the straightness of the measuring object at the second position is degree error YK+2, YK+2=24x+x-YK+DKA-2・DKn+D
Calculated by xo-2YI+Y2, = 0.1.2・
Xl and Yl are obtained by calculating the value of YK+2 calculated for ... so that the root mean square value of the straightness error is minimized.
, Y2 to estimate and calculate the straightness of the object to be measured, and add +2 to the straightness XK+2 of the movement guide surface at this position and the vertical sway θ in the front-rear direction due to the movement, respectively XK+2= A straightness measuring method characterized by calculating by YK+2+DK+2A.