JPH01162903A - Generating method for nc data for composite curved surface - Google Patents

Abstract

PURPOSE:To improve the machining accuracy of a working curved surface consisting of a composite curved surface by obtaining a tool locus so as to ensure the approximately even working area and working load of the working curved surface and carrying out the machining along said tool locus. CONSTITUTION:The offset curved surfaces alpha and beta are defined as the coordinate planes. Then the tool loci L and L1 are set in the direction of the axis of the curve coordinates U or V in parallel with the other coordinate axis and with a fixed space secured between both loci with one of both coordinates U and V set on both surfaces alpha and beta defined as a parameter. Thus the machining is possible along the working curved surface and the cutting areas due to both loci L and L1 are unified. Then the machining accuracy is improved even with a composite curved surface.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for creating NC data for machining a composite curved surface that is a composite of a plurality of curved surfaces.

[Prior art]

A conventional method for machining a workpiece having a compound curved surface using a vertical NC machine tool will be described with reference to FIGS. 6, 7, and 8. The machining curved surface of a workpiece composed of a compound curved surface is offset according to the tool dimensions (for example, the radius of a ball end mill), and the offset curved surface α is the moving curved surface of the tool center M when machining the machining curved surface. β is calculated. The movement locus of the tool T on the offset curved surfaces α and β is determined as follows. In the rectangular coordinate system shown in FIGS. 6 and 7, an offset curved surface is cut parallel to the X axis at a constant interval ΔY in the Y axis direction, as shown by curves C1, C2, C3, C4°C5, for example. As shown in Figure 8, the tool trajectory is determined from the outline of the cut surface. The workpiece is then machined by moving the tool center M along this tool trajectory.

[Problems to be solved by the invention]

However, since the tool trajectory is determined at regular intervals, in areas where the rate of change in the area of the machined curved surface with respect to the constant interval direction is large, for example, in sloped areas as shown in area S shown in Fig. There is a problem that processing serum and processing load increase, and processing accuracy decreases. The present invention has been made in order to solve the above problems, and its purpose is to find a tool trajectory that makes the machining area and machining load of a machining curved surface approximately uniform;
The purpose is to improve the machining accuracy of a machining curved surface composed of a compound curved surface by machining along the tool trajectory.

[Means to solve the problem]

The structure of the invention for solving the above problem is that, in a method for creating NC data for machining a machining curved surface composed of a small number of curved surfaces, the tool center position is moved by offsetting the machining curved surface according to the tool dimensions. The offset curved surface to be offset is determined, and in one specific offset curved surface selected from the offset curved surfaces, the specific offset curved surface is used as a coordinate curved surface, and one curve coordinate among the curve coordinates taken on the specific offset curved surface is determined. The curved portion of the curve that occurs when the coordinates of the other curves are fixed and changed until it intersects with another offset curved surface is one movement locus of the tool, and the fixed curved coordinates are sequentially changed, and the curved line coordinates are sequentially changed. It is characterized in that NC data is created using the generated curved portion as the movement locus of the tool.

[Effect]

An offset curved surface where the tool center should be located is determined from a machining curved surface composed of a compound curved surface. Next, among the offset curved surfaces, a specific offset curved surface (drive surface) that is currently attracting attention is set in order to obtain the movement locus of the tool. A specific offset curved surface expressed in Cartesian coordinates can be expressed by converting it into curved coordinates, but the curve coordinates are set so that the specific offset-soto curved surface is a coordinate surface expressed by two curved coordinates. be able to. That is, any point on a specific offset curved surface can be expressed by two curve coordinates taken on the specific offset curved surface. In that case, if one curve coordinate is fixed and the other curve coordinates are made variable, a curve parallel to the coordinate axes of the other curve coordinates (parallel on the curved surface coordinates) can be obtained. Then, by sequentially changing the fixed curve coordinates as parameters, a group of curves parallel to the coordinate axes of other curve coordinates is obtained. Then, so that the tool is moved along the curves,
NC data regarding tool positioning is created. Therefore, the machined curved surface corresponding to the above-mentioned specific offset curved surface is moved at regular intervals in the direction of the other curved coordinate axes, and
Machining will be performed along a curve parallel to one curve coordinate axis. Therefore, cutting along the machined curved surface is possible, and uniform processing is performed, so that the processing accuracy of the compound curved surface is improved.

【Example】

The present invention will be described below based on specific examples. FIG. 3 shows an NC data creation device for realizing the method of the present invention. This NC data creation device is composed of a normal computer system, and a C
It mainly includes a RAM 2 that stores PUI and various data, a ROM 3 that stores NC data creation programs, etc., and an external storage device 4 that stores data that defines various machining surfaces. Other devices include a display device 7 for displaying various information, a keyboard 8 for inputting various operations, a tape puncher 10 for outputting created NC data, and a printer 9 for outputting an NC data list.
is connected to the CPU via interface 5 or interface 6.
Connected to I. Next, the processing procedure of this apparatus will be explained according to the flowchart of FIG. 4 and the explanatory diagram of FIG. 5. Machining curved surface A and machining curved surface B are divided into many minute regions called pa-sochi, and these curved surfaces are expressed by the orthogonal coordinates of nine points around the patch using x, y, and z, and the data of the orthogonal coordinates is remembered by the group. In step 100, the offset/) curved surfaces α and β of the machined curved surfaces A and B are determined. These offset curved surfaces α and β are processed curved surfaces A, as shown in FIGS. 5(a) and 5(b). so that the tool tip surface E of the tool T can move along the direction B.
This is a curved surface on which the tool center M of the tool T moves. In the case of a ball end mill, the center of the ball is the tool center M. Tool tip surface E and machining curved surface A. The normal n of the machining curved surfaces A and B at the contact point P with B is:
It passes through the center position M of the ball, and the distance between the contact point P and the tool center M is equal to the radius r of the ball. Therefore, the curved surfaces created by moving arbitrary points on the processed curved surfaces A and B by the radius r of the ball in the direction of the normal line n become the offset curved surfaces α and β. Next, in step 102, in order to obtain the movement locus of the tool center M of the tool T, a specific offset curved surface (drive curved surface) β, which is one offset curved surface of interest, is selected. The specific offset curved surface β is divided into many regions called patches, and one patch R is divided into regions called patches.
), it is defined by the position coordinates of nine points. That is, the curve coordinates (u,
v), (-1,-1), (-1,O),
(-1,1), (0,-1>, (0,0), (
0゜1), (1,-1), (1,0), (1,1
) are given as data. Then, the position vector P(u, v) at any point (U, V) on the patch can be found by simultaneously using the above equations. In this way, a biquadratic surface interpolation formula is obtained. Next, in step 104, among the curve coordinates u and V, the curve coordinate U is the initial value U. Fixed. Then, in step 106, as shown in FIG. 5(C), a curve on the specific offset curved surface β parallel to the curve coordinate axis V is obtained, and the curve is taken as one tool trajectory. Next, in step 108, as shown in FIGS. 5(c) and 5(d), the curve obtained in step 106 is converted into a series of points, and the coordinate values of that point in the x, y, z coordinate system are determined. It will be done. Then, as shown in FIG. 5(e), if the above point sequence exists below (-Z axis direction) than the other offset curved surface α, the curve L1 on the offset curved surface α is converted into a point sequence. and adopted as the tool path. Next, in step 110, the points on the curved line are sequentially approximated by a straight line, tolerance is determined, and unnecessary points are thinned out. Next, in step 112, NC data for linear interpolation between each point is created based on the point sequence data obtained in step 110. Next, the process moves to step 114, where it is determined whether the curve coordinate U is equal to the final value (in the example of FIG. 5(C), one revolution along the curve coordinate axis), and if it is not equal to the final value, Then, the process moves to step 116, where the curved line mu is increased and updated by a constant width ΔU. Then, the process returns to step 106, and the calculation processing of the tool path is repeated in sequence until the curved line [u becomes final in step 114. And step 1
When it is determined in step 14 that the curved line 28u is final, this program is terminated. In this way, tool trajectories as shown in FIG. 1 are sequentially determined. In the above embodiment, a plurality of tool trajectories parallel to the curve coordinate axis V were obtained at regular intervals in the direction of the curve coordinate axis U using the curve coordinate U as a parameter, but as shown in Fig. 2, the curve coordinate U was used as a parameter. A plurality of tool trajectories parallel to the curved coordinate axis 11 may be obtained at regular intervals in the direction of the curved coordinate axis V. Further, by using a compound command, the point sequence with the lower Z value may be adopted as the tool path. Furthermore, as shown in FIGS. 1 and 2, if cutting is performed using both machining trajectories, the accuracy of the machined surface will be improved. [Effects of the Invention] The present invention uses an offset curved surface as a coordinate plane, and uses one of the curved coordinates provided on the offset curved surface as a parameter and is parallel to other curved coordinate axes at regular intervals in the direction of the curved coordinate square. Since the tool trajectory is set, machining can be performed along the machining curved surface, and the cutting area can be made uniform with one tool trajectory. Therefore, machining accuracy is improved even in the case of a compound curved surface.

[Brief explanation of the drawing]

FIGS. 1 and 2 show an NC according to a specific embodiment of the present invention.
An explanatory diagram showing a data creation method. FIG. 3 is a block diagram showing the configuration of a device for realizing the NC data creation method. FIG. 4 is a flowchart showing the processing procedure of the device. FIG. 5 is an explanatory diagram showing a method of creating NC data. FIG. 6, FIG. 7, and FIG. 8 are explanatory diagrams showing how to take a machining trajectory according to the conventional method. T Tool M-Tool center E Tool tip surface P Contact r
Ball radius A, B Machining surface α, β-offset surface n ゛ Normal line U, V Curve coordinates 01 to C5
, L, LL Tool trajectory Fig. 1 Fig. 2 Fig. 4 Fig. 5 (a) (b) Fig. 7 Fig. 8

Claims (1)

[Claims] In a method for creating NC data for machining a machining curved surface composed of a plurality of curved surfaces, the machining curved surface is offset according to tool dimensions to determine an offset curved surface on which the tool center position should be moved. , In one specific offset curved surface selected from the offset curved surfaces, the specific offset curved surface is used as a coordinate curved surface, and among the curve coordinates taken on the specific offset curved surface, one curve coordinate is fixed and the other curve coordinates are The curved portion until the curved line that occurs when changing intersects with another offset curved surface is one movement locus of the tool, and the fixed curved coordinates are sequentially changed, and the curved portions that are sequentially generated in the same manner are defined as the tool. NC of a complex curved surface is characterized by creating NC data as a movement trajectory of
Data creation method.