Method of creating NC data for machining curved surfaces

Details Method of creating NC data for machining curved surfaces Method of creating NC data for machining curved surfaces

1988-12-12

1991-04-16

Smith, Jerry

Boots, shoes, and leggings

36447429, 36447425, G05B 1942, G06F 1546

Patent

active

050088068

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
This invention relates to a method of creating NC data for machining curved surfaces. More particularly, the invention relates to a method of creating NC data for machining a curved surface having a cutting boundary surface in the depth direction.
2. Background Art
In the numerically controlled machining of a three-dimensional mold or the like, a curved surface is defined by a plurality of section curves, a point sequence is generated on the curved surface from data such as that indicative of the section curves, data relating to the generated point sequence on the curved surface are stored on an NC tape, and machining of the curved surface is executed by commands from the NC tape.
When a curved surface is defined from data (section curve data) on a mold design drawing and the entire region of the generated curved surface is machined, there are cases where a neighboring surface is cut into or where, conversely, an excessively large vacant cutting path is generated, leading to waste in terms of machining.
Consequently, a method has been developed for use when machining a curved surface 101, as shown in FIG. 6. The method includes designating a cutting boundary 105 in the depth direction in a plane 104 located at a height Z.sub.H from an X-Y plane, outputting a machining point sequence P.sub.i (i=1, 2, ...) up to the cutting boundary, thereby creating NC data, and subsequently creating NC data in the same manner upon performing a pick-feed. It should be noted that whether the point sequence P.sub.i has reached the cutting boundary 105 is determined based on whether the Z coordinate of the point sequence P.sub.i has become less than Z.sub.H.
When a curved surface 101' is machined, as shown in FIG. 7, there are times when it is desired to prevent cut-in by adopting a curved surface 104' as a cutting boundary surface in the cutting direction. For example, there are cases where a TV frame is cut on the curved surface of a cathode ray tube. In cases such as these, machining in accordance with the prior art is difficult.


SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a method of creating NC data for machining curved surfaces in which any curved surface is adopted as a cutting boundary surface in the depth direction.
The present invention relates to an NC data creation method for machining a curved surface having a cutting boundary surface in the depth direction.
Data specifying a three-dimensional curved surface and a curved surface of a cutting boundary in the depth direction are inputted. When the three-dimensional curved surface is defined by a set of a plurality of point-sequence paths, a point sequence Q(i,j) of a tool nose corresponding to a point sequence A(i,j) is determined. Next, there is determined a projected point sequence B'(i,j) obtained by projecting the point sequence Q(i,j) of the tool nose onto a reference plane, as well as a projected point sequence C(i,j) obtained by projecting the first-mentioned projected point sequence onto the curved surface of the cutting boundary. Thereafter, a check is performed to see whether a line segment connecting the point sequence Q(i,j) of the tool nose and a line segment connecting the projected point sequence C(i,j) on the curved surface of the cutting boundary intersect. If they do intersect, NC data up to the point of intersection P(i,j) are created. NC data are subsequently created in the same manner upon performing a pick-feed.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view for describing the general features of the present invention;
FIG. 2 is a block diagram of an NC data creating apparatus according to the present invention;
FIG. 3 is a flowchart of processing according to the invention.
FIG. 4 is a view for describing point-sequence paths on a curved surface;
FIG. 5 is a view showing the relationship among a point-sequence path, the center of a tool and the tool nose;
FIG. 6 is a view for describing an example of the prior art; and
FIG. 7 is a view for describing that mach

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