Boots – shoes – and leggings
Patent
1992-03-16
1994-04-19
Nguyen, Long T.
Boots, shoes, and leggings
36447418, 318572, G05B 1918
Patent
active
053052285
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tool axis direction calculation method used in an automatic programming apparatus for creating NC data (machining program) for cutting a sculptured surface of a metal mold, and more specifically, to a tool axis direction calculation method of determining a direction vector of a tool axis in a side cut carried out by a 5-axes numerically controlled machine tool.
2. Description of the Related Art
Automatic programming apparatuses for creating NC data for cutting a sculptured surface of a metal mold are provided with a software for creating various NC data, and this software can simultaneously determine offset data for a tool.
Also, 5-axes numerically controlled machine tools having B- and C-axes for inclining a tool axis in addition to the usual X-, Y- and Z-axes, are available and can cut a side of a workpiece by using a flat end mill.
When making this side cut, a direction vector of a tool axis is generally determined by the following calculation method:
(a) determining dividing points corresponding to the upper and lower surfaces of a curved surface to be cut;
(b) determining respective normal vectors at these dividing points;
(c) determining points obtained by offsetting the radius of a tool to the directions of the respective normal vectors; and
(d) creating a vector by connecting these points and using the thus created vector as the direction vector of the tool axis.
Nevertheless, this method has the following drawbacks:
First, the direction of the normal vector of the upper surface of a curved surface to be cut does not always coincide with the direction of the normal vector of the lower surface thereof, and thus the direction vector of a tool axis may not be parallel to the generating line of the curved surface and may be twisted.
Second, the tool axis may not be on the line segment (generating line of the curved surface) obtained by connecting the points corresponding to the upper and lower surfaces, respectively, of the curved surface to be cut. More specifically, the tool axis is on the generating line only when the normal vector of the upper surface is equal to the normal vector of the lower surface.
As a result, a sculptured surface to be determined is different from an actual machined surface, i.e., a workpiece is bittin or partially not cut.
SUMMARY OF THE INVENTION
Taking the above into consideration, an object of the present invention is to provide a tool axis direction calculation method of determining the direction vector of a tool axis by which a machining surface can be made closer to a generating line.
To attain the above object, according to the present invention, there is provided a tool axis direction calculation method of determining a direction vector of the tool axis when a side is cut by a 5-axes numerically controlled machine tool, which comprises the steps of determining a first normal vector at a first dividing point of the upper surface of a curved surface, determining a second normal vector at a second dividing point of the lower surface of said curved surface, determining an intermediate vector having a direction between said first normal vector and said second normal vector and a size equal to the radius of a tool, determining a first offset point from said first dividing point and said intermediate vector, determining a second offset point from said second dividing point and said intermediate vector, and determining a vector connecting said first offset point and said second offset point as said direction vector of said tool axis.
When a normal vector of an upper surface is different from a normal vector of a lower surface, the direction vector of a tool axis does not coincide with a generating line. Therefore, an intermediate vector located between the normal vector of the upper surface and the normal vector of the lower surface is determined, and the direction vector of the tool axis is determined from the intermediate vector, whereby a direction vector of the tool axis is deter
REFERENCES:
patent: 4559601 (1985-12-01), Kishi et al.
patent: 4559606 (1985-12-01), Jezo et al.
patent: 5070464 (1991-12-01), Seki et al.
Hanaoka Osamu
Seki Masaki
Fanuc Ltd.
Garland Steven R.
Nguyen Long T.
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