JPH03104536A - Machining method for rotating axis-symmetric curved surfaces - Google Patents

Abstract

PURPOSE:To obtain a specific shape accuracy by calculating an error of a tool origin setting time, the dimensional error of the tool radius and the tool locus error collectively from the shape error of the face to be worked and correcting the error factors of these working shapes. CONSTITUTION:When working is performed by calculating a tool locus by a numerical control unit 14, a work shape error is caused due to the errors of the tool origin and tool radius. The shape of the body 4 to be worked is measured by an electric displacement gage 10, the X, Y, Z coordinates of this measured value are read from the NC unit 14 and the result is input to a calculation processing unit 15. A measuring origin is provided by calculating the position of the rotary center of the body 4 to be worked from these data and input to the NC unit 14. The measurement of the shape of the working face is performed by the electric displacement gauge 10 by the section including the rotary center shaft of the face to be worked based on this measured origin. This measured result is again input to the calculation processing unit 15, the shape error is calculated from its comparison with a target work face shape, the work is completed in the case of less than a target value and correcting is performed so as to correct the error factor in the case of not satisfying.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to grinding and cutting of a surface that is symmetrical about the rotational axis,
The present invention relates to a machining method suitable for remachining with high accuracy and high efficiency.

[Conventional technology]

When machining a surface that is symmetrical about the rotational axis, the tool origin is the position where the center of the tool coincides with the rotation axis of the workpiece surface, and the coordinate system from this origin is used to numerically control the rotation center of the workpiece surface. Machining is performed by moving the tool along a relative trajectory. However, errors occurred in the machined shape due to errors in setting the tool origin and dimensional errors in the tool radius. As described in Japanese Patent Application Laid-Open No. 114445/1983, in this case, the error in setting the tool origin is taken into account, but the dimensional error in the tool radius is not taken into consideration. If the above technology is not applied, the process of correcting the relative trajectory of the tool with respect to the center of rotation of the workpiece surface (auto) is repeated several times to obtain the desired shape accuracy using the shape error of the machined shape obtained from the shape measurement number. was.

[Problem to be solved by the invention]

When machining a surface that is symmetrical about the rotational axis, the tool center point is aligned with the rotation center axis of the workpiece surface and is used as the tool origin. This error in setting the tool origin causes a relative positional error of the tool relative to the co-rotating axis l of the machined surface.

Furthermore, due to the dimensional error of the tool radius, overcutting or uncutting occurs in the normal direction of the surface to be machined.

Although the above-mentioned conventional technology takes into account the error when setting the tool origin, it does not take into account the dimensional error of the tool radius, and in order to obtain a predetermined shape accuracy, the tool trajectory is There was a problem in correcting over the entire area.

The purpose of the present invention is to eliminate errors when setting the tool origin from shape errors on the workpiece surface. It is possible to obtain a predetermined shape accuracy by calculating the tool radius dimensional error and tool trajectory error all at once and correcting these error factors in the machined shape.

[Means to solve the problem]

The above objective is achieved by the following method.

When the cross-sectional shape of a machined surface that is symmetrical to the target rotation axis is given by a certain function, the shape error at a point at an arbitrary distance from the rotation center axis of the machined surface is calculated as the error in setting the tool origin and the dimensional error in the tool radius. and expressed as a function of the distance from the rotation center axis of the workpiece surface. The shape error at a certain range of points found by measuring the machining shape is substituted into this equation, and the tool setting error and tool radius dimensional error are calculated by multiple regression analysis.

By substituting this result into the function of the shape error described above, and substituting the shape error of each point obtained by measuring the machining shape, the tool path error is determined.

After correcting these tool setting errors, tool radius dimensional errors, and tool trajectory errors, machining is performed again to obtain the target machined surface shape.

[Effect]

Error when setting the tool origin. Dimensional errors in the tool radius and errors in the tool trajectory are major causes of deterioration in shape accuracy, and it is extremely difficult to separate them individually. However, tools such as grinding wheels are affected by surface irregularities and whirling.
It is extremely difficult to accurately grasp the shape, and errors occur due to wear during processing. Furthermore, it is extremely difficult to predict the operational errors of the processing machine before processing. Therefore, calculation means are used to calculate the shape error and the difference when setting the tool origin from the measurement results of the shape after machining. Dimensional error in tool radius. The error in the tool path is determined, and based on this result, the tool origin and tool radius are corrected using the numerical control device, and the ideal tool path is drawn on the workpiece surface to perform machining again and achieve the target machined surface shape. 0 [Example] An example of the present invention will be described based on the drawings. FIG. 1 is a processing procedure using the present invention. FIG. 2 shows an embodiment of the invention. FIG. 5 shows the error in setting the tool origin and the dimensional error in the tool radius. FIG. 4 shows the relationship between each error factor and processing shape error.

In Fig. 2, 1 is the main body of the processing machine and the XY table 2
is supported so that it can move arbitrarily within the XY plane. A workpiece 4 is attached to a spin table 5 so as to rotate on its axis, and the spin table 5 is fixed to the XY table 2. 12 is a two-axis column 1 which can be used as a grinding wheel and can be moved arbitrarily in two-axis directions.
It is rotatably attached by a grindstone drive motor 8 via a grindstone 6 . 10 is a drowsiness type displacement meter and is fixed to a Z-axis column 15 via an arm 9. 5 and 6 are Y-axis direction drive motors. An X-axis direction drive motor is controlled by a numerical controller 14 to move the XY table 2 to an arbitrary position. 7 is z41! A directional driving motor is used to move the two-axis column 158 to an arbitrary position by the numerical control device 14f. Reference numeral 15 denotes a calculation processing device, which is electrically connected to the numerical control device 14.

In this configuration, after inputting the tool origin and tool radius, the grinding wheel 12 is rotated simultaneously by the grinding wheel drive motor 8, the workpiece 4 is rotated simultaneously by the spin table 3, and the XY table 2 is rotated to an arbitrary trajectory by the numerical control device It14. By moving the top, the target machined surface shape is obtained.

In the above machining method, the center of the grinding wheel 12 is made to coincide with the rotation center axis of the workpiece 4 as the origin when specifying the trajectory of the XY table 2, thereby making the tool origin. Also, as the tool radius, the grindstone radius measured outside the machine is input. However, in reality, since the tool is a grinding wheel, it is very difficult to correctly position or input these, and there are errors in setting the tool origin and tool radius. This shows the error when the workpiece 4 and the grinding wheel 12 are set at the position [1] in the figure as the trowel tool origin. Two axis directions of the tool origin at this time. The error in the Y-axis direction is zj}l, IC, and the dimensional error in the tool radius is j
iR (l in Figure 1).

Based on these input values, the tool trajectory is calculated by the numerical control device 14 (■ in Figure 1), and when machining is performed (■ in Figure 1)
), these errors cause machining shape errors. next'
The shape of the workpiece 4 is measured using the 4-gas displacement meter 108 (
■) in Figure 1), this measured value (7)X. Y. The Z coordinate is read from the numerical control device and the result is sent to the calculation processing device ljt1.
Enter 5. From these data, calculate the position of the center of rotation of the workpiece 4 +1, set the measurement origin here, and set the numerical control device 1jll! :14 (V in Figure 1). Based on this measurement origin, the shape of the machined surface is measured using an electric displacement meter 10 at a cross section including the rotation center axis of the machined surface (■ in FIG. 1). This measurement result is again calculated by the calculation processing device [4
115 is input, and the shape error is calculated from comparison with the target machined surface shape (■ in Figure 1) 0 If the shape error is less than the target value, the machining ends (■ in Figure 1) ) If this is not satisfied, perform correction processing using the following steps.

Based on the shape error obtained above, we will explain how to calculate the error factors AC and JR (in Figure 1). The ideal grinding wheel is indicated by 17. However, the error AC in setting the tool origin and the dimensional error JR in the tool radius
Therefore, the actual whetstone is at the position indicated by 19.
The surface to be machined is represented by 181 planes. When the target machined surface shape is expressed as x = f (y), the shape error Axi at the distance yl in the y-axis direction from the rotation center of the machined surface is determined by the error lC at the time of tool setting using a geometric method. It is expressed by equation (1) using the tool radius dimensional error JR.

Axi=JR(1-cosl9i)-jC
tanθi (1) where θl is y from the center of rotation of the machined surface
This is the angle between the tangent to the target machined surface 16 and the y-axis at the point of distance yi in the axial direction, and θi is expressed by equation (2) using the first derivative of f (y).

tanθi=f'(yi)
(2) Therefore, equation (1) is jXi=JR(1-JT+f'(xi)'') −
j C f'(yi) (5). Also, the relationship between the error AH in C and the shape error axl during tool setting is (
4) It is clothed according to the ceremony.

jxj=f( )'i"-j}F) f()'i)
Therefore, (!SL) Formula (5) can be found from Formula (4).

j xi +j H2f'(yi) / 2 yi=j
H(1-v'1+f'(yi)2-jcf'(yi)
(5) Vi=JRVi+jCWi
(6) Here, Vi=Noxi+jH2・f'(
yi) / 2 yivt=1-J7 "i contribution〒 Wi = f'(yi) The above lz is measured from the grinding marks left on the machined surface.

Since equation (5) only holds true when the tool trajectory is extremely accurate, not all shape measurement results are satisfied if the processing machine has low motion performance. Therefore, it is necessary to perform multiple regression analysis using equation (5) and equation (7) f only for the measurement results of a roll relatively close to the rotation center t of the workpiece, and to correct the tool trajectory for areas outside of this range. There is.

J. However, CC: constant term J, starting point J of the range for double regression analysis, end point J of the range for double regression analysis JR,l(:, obtained using formula (7)) from formula (5). By substituting the obtained equation (8) and the shape measurement results obtained above, the tool path error (yi. j xci) is calculated.
is required.

jxci=jxi+jH2f'0'i)/2yi-JR
(1-J1+f'(yi)2) 1Cf'(yi)(8
) Tool setting error j (::, jH dimensional error dR of grinding wheel radius and tool path error (yt+jx
After regressing ci) into a 10th order function, the coordinates of this curve are input from the calculation device 15 to the numerical control device 14, and the tool origin,
The target machined surface shape can be obtained by correcting the tool radius and tool trajectory (X in FIG. 1) and performing machining again (I to ■ in FIG. 1).

Finally, I will discuss the results of the actual machining.

The workpiece is stainless steel tool net SUS420. Use CBN vitrified grindstone SOO as the grinding wheel, spin table speed 50 rpm + grinding wheel rotation speed 1800
O rpm. X Y table speed 0.5til/y
In y1i1, a curved and narrow rotational axis symmetrical surface expressed by equation (9) is machined. The shape decreases when 7>R'.In the machine in which this study was conducted, the X-axis table had bank lash, so the shape accuracy deteriorated when the direction of movement of the X-axis table changed.

Machining accuracy when grinding 5 times with depth of cut 2μm is ±7μm
However, using the present invention, after performing multiple regression analysis in the range of (-pt/, R) and correcting the processing error factors,
As a result of the correction machining, a machining shape error of ±0.5 μm was obtained, and a machining time of 25 hours was obtained.

With the conventional technology, five correction processes are required to obtain a shape accuracy of ±1 μm, which takes about 52 hours.

By using the present invention, processing time can be reduced by 50%.
This makes it possible to perform even more precise machining.

〔Effect of the invention〕

According to the present invention, a workpiece can be machined with high accuracy in a short time, which is effective in shortening the machining time and improving machining accuracy.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an embodiment of the present invention, 8g2
5 is a front view of the workpiece and grinding wheel showing the error in setting the tool origin and the dimensional error of the tool radius; FIG. teeth,
FIG. 3 is a cross-sectional view showing the relationship between each error factor and processing shape error. 1... Processing machine body 2... XY table 6...
・Spin table 4... Workpiece 5... Y-axis direction drive motor 6... X-axis direction, drive motor 7... Z-axis direction drive motor 8... Grindstone drive motor 9... Arm 10... Electric displacement meter 11... 2-axis arm 12... Grinding wheel 15... 2-axis column 14... Numerical control device 15... Calculation processing device 16... Target machining shape 17 ...Ideal grinding wheel position I 1 2 times 3 Diagram 4-

Claims (1)

[Claims] 1. A numerical value that allows numerical control of the tool trajectory in a machine tool that processes surfaces that are symmetrical about the rotation axis by rotating the workpiece and moving the tool on a trajectory relative to the rotation axis of the workpiece. A control means, a shape detection means for measuring the machining shape of the workpiece, and an arithmetic means for calculating the shape error of the workpiece and the error during tool setting based on the data obtained from the detection means are provided. A method for machining curved surfaces symmetrical to a rotational axis, characterized by calculating setting errors and tool path errors all at once, correcting them by numerical control means, and performing correction machining.