JPS61272805A - Numerical control method - Google Patents

Abstract

PURPOSE:To simplify the processing by perceiving that it is sufficient if a tool locus is obtained as locus scanning on an offset curved surface at certain intervals with respect to curved surface working and obtaining the intersection between a plane parallel with a main spindle and a curved surface to be worked and processing it in the plane. CONSTITUTION:An intersection 52 between an offset surface 2 and a cutting plane 51 parallel with the Z axis is obtained as a two-dimensional curve on the U and V parameter space of the cutting plane 51, and groups of intersections between intersections 53 and 55 and straight lines Li which are formed at certain intervals in the cutting plane and are parallel with the Z axis are obtained in the U and V parameter space of the cutting plane 51, and a point Pi where the Z value is largest is selected if plural intersections exist with respect to each line Li, and these point group are connected to generate curves 54 and 56, and they are outputted as the tool locus to perform the numerical control of three-dimensional curved surface working. In this system, the interference of the tool with the curved survace to be worked is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a numerical control method for machining a three-dimensional curved surface.

[Background of the invention]

Conventionally, when machining a three-dimensional curved surface expressed by two parameters U and V, the tip of the tool is first set as shown in Fig. 12 in order to output the locus of the center of the tool in the tool path for curved surface machining. Approximate it with a hemisphere, create a curved surface 2 in which the processed surface 1 is offset in the normal direction of the curved surface by the radius r of the sphere, and find a curve group 11 with a constant curved surface parameter U or ■ on the offset curved surface 2. , a method is known in which the center of the tool is moved along a group of curves.

Here, offsetting a curved surface means generating a new curved surface in which all points on the curved surface are aligned in the normal direction of the curved surface.

However, with this method, as shown in Figure 13, when viewed from the main axis direction (generally, in the coordinate system of a machine tool, the Z axis is the main axis direction, henceforth referred to as the Z-axis direction), it becomes a shadow. When machining a curved surface with a divided area or a curved surface with a portion with a radius of curvature smaller than the tool diameter, as shown in Fig. 14,
The offset curved surfaces are 4 and 8, and the hatched areas 6 and 10 are erroneously machined, resulting in interference of the tool with the machining curved surface (
There was a problem in which scratches (cutting) occurred.

An example of a numerical control method for three-dimensional curved surface machining is described in detail in Japanese Patent Laid-Open No. 57-166606, in which characteristic lines of a curved surface are input, and numerical values for curved surface machining are calculated based on the curve. A control method is known, but since the tool path uses a point on the machining curved surface created by moving the characteristic line offset in the normal direction of the curved surface, the same method as described above is used. A problem occurs.

[Purpose of the invention]

The purpose of the present invention is to
An object of the present invention is to provide a numerical control method that prevents tool interference with a machined curved surface.

[Summary of the invention]

In the case of the above-mentioned curved surface, the reason why cutting into the machined surface occurs is because the offset curved surface is a function that has multiple Z values for a certain coordinate (xty), and basically As shown by the shaded area 12.13 in FIG. 15, the problem can be solved by extracting only the part that is visible when the offset curved surface is viewed from the large Z-axis direction and processing that part.

However, it is mathematically very difficult to extract only the above-mentioned parts of a curved surface in a general three-dimensional space.
In the present invention, we focused on the fact that in machining a single curved surface, the tool trajectory can be found as a trajectory that scans an offset curved surface at certain intervals, and as shown below, we find the intersection line between a plane parallel to the main axis and the machined curved surface. , the processing was simplified by performing the processing within a plane.

First, as shown in FIG. 16, the offset surface 2 and the Z
Intersection line 52j- with cutting plane 51 parallel to the axis, cutting plane 5
1 as a two-dimensional curve on the U, V parameter space,
Next, as shown in FIGS. 17 and 18, on the U and V parameter space of the cut plane 51, intersect @53, 55.

Make sure to create the spacing within the cutting plane. Find a group of intersections with the straight line group L1 parallel to the Z axis, and if there are multiple intersections for 6 straight lines 1sL+, select a point Pt with a large z value and connect these groups of fish to form a curve. 54 and 56 are created and output as a tool trajectory to perform numerical control of three-dimensional curved surface machining.

This method enables a numerical control method that prevents the tool from interfering with the curved surface to be machined.

[Embodiments of the invention]

Next, an outline of the numerical system of the present invention is shown in Figures 1 to 10.
This will be explained according to the diagram. FIG. 1 shows a processing flow, and FIGS. 2 to 10 are explanatory diagrams of each block.

■ Create an offset curved surface by offsetting the machined surface by the tool diameter in the normal direction of the curved surface. (Fig. 2) ■ Cutting plane that includes the machined surface and is parallel to the Z axis, sM.

S2. ...S, is created at user-specified intervals.

(Fig. t43) The following steps ①~ are performed for each cut surface 8IeS2e...S.

(2) Find the line of intersection between the offset plane and the cut plane S1 as a curve in the U and V parameter space on the cut plane. (4th
(Figures or Figures F46) ① For each line of intersection obtained in ②, divide the line of intersection so that when expressed in the form v=f(u), V is uniquely determined with respect to U. (Figure 7.

(Fig. 8) ■ Create a straight line group Ct t C2g . . . C1 that covers the intersection line group and is parallel to the Z axis within the cutting plane. The two-axis descendant line is created as a U=constant straight line on the cutting surface, and the interval between the straight lines is determined by the machining accuracy specified by the user.

(2) For the group of intersection lines obtained in (2) and the group of two-axis child line lines obtained in (2), find the intersections of all the lines that intersect, and classify them for each two-axis child line.

■ Select the point with the maximum Z value for each two-axis child line. (The above ■■■ 9th 9th, 10th) Connect the selected fish schools and create a tool motion command sequence.

Each item will be explained below.

[1] Calculating the intersection line between the offset plane and the cut plane Various methods have been proposed for calculating the intersection line, so here we explain that the intersection line can be found as a curve that takes values in the surface parameter space. do.

The cut plane is S(U, V), and the offset plane is S'((σt,
vt). 8. S' is U respectively.

It can be written as a vector-valued function that takes values in three-dimensional space, with V, u/, and v/ as parameters.

That is, S (U, V) = (S, (U, V), SF (U
, V), S, (U, V))3'(u', v
')=(S',(u', v勺, S'y(
u', v'), 8'-(u'-V')).

The intersection line is the solution of the simultaneous equations 8 (u, V) = 8'(u',V'). Since this formula has three equations, four uncalculated numbers, and one degree of freedom, we can introduce the parameter t and solve the intersection m using Newton's method in the form below. can.

u=f1 (t), v=f(t)...Parameter expression on S=f3(t), v'=f4(t)...S'
Above (DA-y me-fi expression [Effects of the invention]) According to the present invention, numerical values of curved surfaces with a radius of curvature smaller than the tool diameter, three-dimensional curved surfaces with shadow parts when viewed from the main axis direction of the machine tool, etc. In controlled eggplant processing, Al is added to the workpiece.
It is possible to prevent immersion.

[Brief explanation of the drawing]

1 to 10 are detailed explanatory diagrams of a numerical control system according to an embodiment of the present invention. Figures 13 and 14 are explanatory diagrams of the points between the lines in the conventional method.
FIGS. 15 to 18 are explanatory diagrams of the numerical control system. 1... Curved surface to be processed, 2... Offcent curved surface, 30
゜33.34...The intersection line between the offset curved surface and the cutting plane, 31.32...The intersection line between the cutting plane and the surface to be machined, Fig. 1'1fJZ Fig. 3 Fig. ll Fig. 1'Z Figure 13 Part 14 II Figure 15

Claims (1)

[Scope of Claims] 1. A graphic processing device comprising means for storing data of a curved surface represented by two parameters, and means for processing the curved surface using numerical data, the method comprising: Find a first curved surface that is offset by the tool diameter in the direction, find the intersection line of the first curved surface with a plane parallel to the main axis of the machine tool, and intersect the line group parallel to the main axis created in the plane with the first curved surface. Find a group of intersections with the line, and if there are multiple intersections for one straight line, select the intersection with a large directional component of the principal axis, and then generate a tool path passing through those intersections to A numerical control method characterized by processing.