JP2007164411A - Machining path data generation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently generate a tool path allowing for highly precise machining. <P>SOLUTION: Based on a Z-map model of a product shape in an unmachined area of a workpiece and a predetermined inclination angle value, the unmachined area is divided into a contour machining area 11 of large inclination and a shape following machining area 12 of small inclination. In the contour machining area 11, a contour tool path is generated. In the shape following machining area 12, a shape tool path including a portion for tool move with varying cutting depth is generated with a pitch adjusted according to machining conditions and Z-axial shape variation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to a machining path data generation method for generating a tool path for machining an unmachined area of a workpiece with a tool of an NC machine tool based on three-dimensional shape model data.

    In NC (numerical control) cutting, a cutting tool such as a ball end mill is moved along a predetermined tool path on the processing surface of a workpiece (metal material). In this cutting process, the cutting amount of the cutting tool is moved in a contour line with a constant cutting amount in the Z-axis direction, and then the cutting amount is changed in the same contour line by changing the cutting amount, and the cutting amount is stepped at a predetermined pitch in the Z-axis direction. Contour line processing that changes continuously is widely adopted. However, in this contour processing, the interval between adjacent tool paths is widened in a portion where the slope of the product-shaped slope is gentle compared to a portion where the slope is steep, and machining accuracy is lowered.

To solve this problem, a technique is known that, in contour machining, in a machining region where the interval between tool paths is wide, a tool path is added to the widened portion to avoid a reduction in machining accuracy. (See Patent Document 1).
Japanese Patent Laid-Open No. 11-3110

    However, the interval between adjacent contour tool paths is not constant over the entire circumference, and when the product shape is complicated, it becomes narrower or wider from the middle and variously changes. Therefore, it is difficult to arrange the tool path at an appropriate interval, length, and number so as to follow the existing contour tool path to the part where the distance has changed.

    Therefore, an object of the present invention is to efficiently generate a tool path capable of performing highly accurate machining even in an unmachined region where the inclination of the product shape changes in a complicated manner.

    In order to solve such a problem, the present invention divides an unprocessed region into a contour processing region and a processing region along the shape based on the inclination angle of the corresponding product shape, and an appropriate amount according to the inclination angle. The tool path can be generated.

The invention according to claim 1 is a machining path data generation method for generating a tool path for machining an unmachined region of a workpiece with a tool of an NC machine tool based on three-dimensional shape model data,
Based on the Z map model indicated by the height information in the Z-axis direction of the product shape in the unprocessed area and a predetermined inclination angle determination value, the unprocessed area is processed along the contour process area having a large inclination and the shape having a small inclination. Divided into areas,
In the contour line machining area, a contour tool path is generated at a pitch in the Z-axis direction according to the machining conditions,
In the machining area along the shape, a tool path along the shape for moving the tool while changing the cutting amount is generated at a pitch corresponding to the machining conditions.

    Therefore, according to the present invention, a portion having a large inclination in the unmachined region is classified as a contour processing region and a portion having a gentle inclination is classified as a machining region along the shape. Therefore, an appropriate tool path with high machining accuracy corresponding to the inclination is obtained. Can be generated in a short time. Here, the unmachined area includes a so-called uncut area that could not be cut by the pre-machining in addition to a part that has not yet been machined to the workpiece, and the present invention provides a tool path in the uncut area. It is particularly effective for the generation of

The invention according to claim 2 is the invention according to claim 1,
The adjacent grids are extracted from the group of grids arranged along the outermost periphery of the product shape Z map model of the unprocessed region at an inclination angle equal to or greater than the inclination angle determination value, and this extraction processing is sequentially arranged inside one grid. The grid group is advanced from the outside to the inside, and based on the extracted grid, the unprocessed region is divided into the contour processing region and the shape-altered processing region.

    Therefore, instead of determining the inclination angle between all adjacent grids, the inclination angle between adjacent grids in the circumferential direction of the unprocessed region is determined, and this determination operation proceeds in order from the outside to the inside. Therefore, it is advantageous in dividing into a contour processing region having a large inclination and a processing region along a shape having a small inclination in a short time.

    In particular, this method generates multiple closed tool paths that are offset inward by a predetermined distance sequentially from the outermost periphery of the unprocessed region and extend along the entire length in the circumferential direction with respect to the machining along the shape. Suitable for cases in which processing along the shape proceeds. That is, when the inclination angle is determined between grids adjacent to each other in the circumferential direction of the unprocessed area, the inclination angle is gentle, which means that the portion moves the tool in the circumferential direction described above. This means that the processing region along the shape can be appropriately classified without determining the inclination angles between all the adjacent grids.

    On the other hand, as described above, when the inclination angle of the grid groups arranged in the circumferential direction is determined, contour lines between the grid groups arranged in the circumferential direction that are adjacent to each other in the horizontal direction (parallel to the XY plane), for example. Even if the grid has a region suitable for processing, the inclination angle is determined to be small. Therefore, when a grid determined to have a small tilt angle is included in the set of grids determined to have a large tilt angle, the tilt angle is determined between the grid and a grid adjacent to the outside or the inside of the grid. To correct it.

The invention according to claim 3 is the invention according to claim 1 or claim 2,
In the machining area along the shape, a plurality of tools arranged at intervals inside and outside, having at least a tool path that goes around the outermost periphery of the area and a tool path that goes around the inside along the tool path. The path is set and machining is performed by sequentially shifting the tool from the outer tool path to the inner tool path.
After setting the inner and outer tool path generation lines on the Z = 0 two-dimensional plane onto which the machining area along the shape is projected, both lines are projected onto the corresponding product shape model from the two-dimensional plane, and the product The tool path is generated by correcting the position of the line on the two-dimensional plane so that the interval between the internal and external projection lines on the shape model falls within a predetermined range over the entire circumference.

    Therefore, since the interval of the tool path is set on the two-dimensional plane, it is advantageous for generating the tool path in a short time, and when the interval set on the two-dimensional plane is projected onto the three-dimensional product shape model When it becomes wider than planned, it is corrected with a two-dimensional plane so that it becomes an appropriate interval, so that a tool path along the shape with high machining accuracy can be generated.

    According to the first aspect of the present invention, based on the Z map model of the product shape in the unmachined area of the workpiece and the predetermined inclination angle determination value, the unmachined area is divided into a contour line machining area and a machining area along the shape. And since the tool path | route suitable for the process of this divided | segmented each area | region was produced | generated, the appropriate tool path | route with high machining precision can be produced | generated in a short time.

    According to the invention according to claim 2, the work of extracting adjacent grids with an inclination equal to or greater than the inclination angle determination value from the Z map grid of the unprocessed area is performed along the outermost periphery of the unprocessed area. Starting from a grid group arranged all around, the work is sequentially shifted to the grid group arranged inward one grid at a time. Based on the extracted grid, the unprocessed area is converted into the contour line processed area and the shape. Since it is divided into the along machining area, it is advantageous to divide the unmachined area into the contour machining area and the shape machining area in a short time.

    According to the invention according to claim 3, after setting the inner and outer tool path generation lines in the Z = 0 two-dimensional plane on which the machining area along the shape is projected, the two-dimensional plane corresponds to the both products from the two-dimensional plane. Projecting on the shape model and correcting the position of the line on the two-dimensional plane so that the interval between the inner and outer projection lines on the product shape model is within a predetermined range over the entire circumference. This is advantageous in generating a tool path along a high shape in a short time.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings.

    For example, when a die is manufactured by NC cutting of a workpiece, the tool diameter is basically reduced starting from a tool having a large tool diameter. This is because, when finishing the entire product, the tool path pitch can be increased by finishing the whole with a tool with as large a diameter as possible, and machining efficiency is improved. The cutting efficiency is increased by cutting the cut portion with a small diameter tool. However, even in that case, if the remaining uncut area in the pre-processing cannot be extracted easily and accurately, the tool paths of each diameter will overlap or the tool path may be lost, making the processing unstable. At the same time, it is disadvantageous for improving the processing efficiency.

    Therefore, first, a method for extracting an uncut region (unworked region of a workpiece) by pre-machining will be described in the case of using a ball end mill as a tool, and then a tool path generation method for the uncut region will be described. The extraction of the uncut region and the generation of the tool path are performed using a CAD / CAM system.

<Extraction of uncut area (unprocessed area)>
-Generation of tool path plane A of product shape polyhedron model-
FIG. 1 shows a final product shape polyhedron model P. As shown in FIG. 2, the tool path for the polyhedron model P is determined by the polyhedron model P and the shape data T of the ball end mill 1 used in post-processing. Surface A is generated. That is, by obtaining a sweep shape when the reverse shape of the ball end mill 1 is slid while keeping its center always on the surface of the polyhedron model P, the top surface of the sweep shape is subjected to reverse offset processing. The tool path plane A is obtained in the Z map model format. This point will be specifically described below.

    As shown in FIG. 3, the surface shape of the polyhedron model P is converted into polyhedron approximate data P2 which is roughly thinned (thinning length is within 10 mm). The polyhedral approximate data P2 is a set surface of a large number of triangles 2 having a very small size. Next, a sweep shape is obtained when the ball end mill 1 is slid while keeping its center always on the surface of the polyhedron model P composed of the polyhedron approximate data P2, and the top surface of the sweep shape is reverse offset. The tool path plane A is generated in the Z map model format by processing.

    That is, as shown in FIG. 4, spheres corresponding to the radius r of the ball end mill 1 are arranged on the XY orthogonal coordinates at the vertexes of the triangle 2, and the spheres are connected by a cylindrical shape having a radius r ( A unit region in which a triangular plate having a thickness twice as large as the radius r is set in a region surrounded by each sphere and the cylindrical shape (unit region is arranged on the side connecting the vertices) Exist for the number of triangles). The sphere, cylinder, and triangular plate are shown in FIG. Next, an orthogonal lattice (a lattice having a unit length of about 0.02 mm) is prepared on the XY plane, and the uppermost point 4 in the Z-axis direction of the unit region is obtained for each lattice point. As a result, the tool path surface A is generated from the polyhedral approximate data P2 in the Z map model format shown in FIG. When an end mill other than the ball end mill 1 is used, an appropriate figure corresponding to the end mill shape may be arranged in place of the sphere, cylindrical diameter, and triangular plate.

-Generation of tool radius road surface B of workpiece shape model-
Next, the tool path plane B for the workpiece shape model W is generated in the Z map model format from the workpiece shape model W including the machining residue and the shape data T of the ball end mill 1. The tool path surfaces A and B are generated based on orthogonal lattices at the same resolution and the same position on the XY plane. This will be specifically described below.

    The right side of FIG. 7 shows a polyhedral model W having a work shape as a Z map model, and the point group covering the surface is arranged in a lattice shape parallel to the X axis and the Y axis. Therefore, as shown on the left side of FIG. 7, these point groups are sequentially traced along the X axis (or Y axis) to obtain a polygonal path 5 that reciprocates in the X axis (or Y axis) direction.

    Next, as shown in FIG. 8, the reverse shape of the ball end mill 1 is moved along the broken line path, and the sweep shape is defined. FIG. 9 shows the state in the same manner as FIG. 2 (case in which the tool path surface A is generated). As shown in FIG. 10, the upper end of the sweep shape has a shape in which spheres and cylinders are alternately connected. When a tool other than the ball end mill 1 is used, a figure constituting the upper end of the sweep shape corresponding to the tool shape may be used instead of the sphere and the cylindrical shape. Thereafter, an orthogonal lattice (the same lattice as that used for generating the tool path surface A) is prepared on the XY plane, and the uppermost point 6 in the Z-axis direction of the sweep shape is obtained for each lattice point. As a result, the tool path plane B is generated in the Z map model format shown in FIG.

-Determination of uncut area-
Since the tool path planes A and B have the same Z-axis direction and are generated based on orthogonal grids having the same resolution and the same position on the XY plane, they can overlap each other as shown in FIG. it can. Since a part of the tool path surface B is generated based on a portion left uncut by the previous machining, a portion that protrudes on the tool path surface A, that is, an uncut region 7 is generated. Therefore, the height of the point group constituting the tool path planes A and B is compared for each lattice of the orthogonal grid on which the Z map is based, and the tool path plane B is higher than the tool path plane A. Select the lattice group that exists in. Then, a point group of the tool path surface A corresponding to this lattice group is selected, and a polygon including them is set as an uncut region line.

<Generation of tool path>
Description will be made along the flow shown in FIGS. 13 and 14. Input parameters are read in step S1 after the start shown in FIG. The input parameters are the above-mentioned uncut region line, the product shape Z map model, the inclination angle determination value, and the tool path generation conditions (tool diameter, path pitch, tolerance (machining accuracy), etc.).

-Uncut area classification-
In the subsequent step S2, the uncut region is divided into a contour processing region and a shape processing region based on the grid angle of the Z map and the tilt angle determination value. Specifically, as schematically shown beside Steps S1 and S2 in FIG. 13, a grid 9 of the Z map in the uncut region line 8 is extracted. As shown at the left end of FIG. 15, the angle of the outer peripheral line connecting the grids existing in the outermost periphery in the uncut region is checked in the circumferential direction. In other words, grids (indicated by black circles) adjacent in the circumferential direction with an inclination equal to or greater than the inclination angle determination value are extracted. This grid extraction operation is performed over the entire circumference of the perimeter line, and is performed on all grids by performing the same operation on the lines extending in the circumferential direction by sequentially offset one grid at a time (see FIG. (See 15 central view).

    In the grid extraction operation, even if the grid exists in a region where the tilt angle is large, for example, it is determined that the tilt angle is small between grids adjacent in the horizontal direction. That is, as shown in the center of FIG. 15, a white circle grid surrounded by black circle grids (a grid determined to have a small inclination angle) appears at the upper side of the uncut region. Therefore, for the small inclination angle grid surrounded by the large inclination angle grid group, as shown on the right side of FIG. 15, the inclination angle is re-determined between the grid and the grid adjacent to the outside or the inside thereof.

    Then, based on the determination of the inclination angle, the uncut region is divided into a contour processing area (black circle grid side) 11 having a large inclination angle and a machining area along a shape having a small inclination angle (white circle grid side) 12. .

    Thus, in classifying the uncut region, it is not necessary to determine the inclination angle between all adjacent grids, and the contour processing region 11 with a large inclination and the machining region 12 with a small inclination along the shape are formed in a short time. It becomes advantageous in dividing. In addition, when there is a small inclination angle grid surrounded by the large inclination angle grid group, since the determination direction of the inclination angle is changed and rechecked, extraction omission can be avoided.

-Generation of tool path along shape (trajectory along shape)-
As shown in FIG. 13, in a subsequent step 3, a two-dimensional area line 13 is obtained by projecting an uncut area (processed area along the shape) line on a two-dimensional plane with Z = 0. Next, in this two-dimensional plane, an offset line 14 obtained by offsetting the two-dimensional region line 13 inward by a predetermined pitch is obtained (step S4). Then, the two-dimensional area line 13 and the offset line 14 are projected onto the corresponding curved surface portion of the product shape model (step S5). The projection lines are denoted by reference numerals 13a and 14a.

    The pitch interval of the projection lines 13a and 14a to the product shape model is obtained over the entire circumference, and when the pitch interval is larger than the predetermined pitch, the pitch interval is corrected (step S6). That is, the part where the pitch interval of the offset line 14 is large is moved outward in the two-dimensional plane so that the pitch interval of the projection lines 13a and 14a becomes a predetermined pitch.

    Similarly, the offset line 15 is obtained inside the offset line 14, projected onto the product shape model, and the work for correcting the pitch interval is sequentially advanced inward, and the obtained tool path 16 along the shape is used as NC data. Writing out (step S7).

    As described above, since the interval of the tool path is set on the two-dimensional plane, it is advantageous for generating the tool path in a short time, and the interval set on the two-dimensional plane is projected onto the three-dimensional product shape model. When it becomes wider than planned, the tool path 16 along the shape with high machining accuracy can be generated because it is corrected with a two-dimensional plane so as to have an appropriate interval.

-Generation of contour tool path (contour trajectory)-
On the other hand, in generating the contour tool path, as shown in FIG. 14, first, the Z map grid of the contour line machining region is connected by the X-axis direction line and the Y-axis direction line of the XY orthogonal coordinates (step S8). Next, this contour line processing region is sliced with a Z plane (plane perpendicular to the Z axis) of a predetermined pitch to obtain the intersection point with the X axis line and the Y axis line (step S9). Next, a contour path is obtained by connecting the intersections (step S10), and the contour tool path 17 is written as NC data (step S11).

    As described above, according to the above-described embodiment, a portion having a large slope in the uncut region is segmented as a contour processing region and a portion having a gentle slope is classified as a machining region along the shape. Therefore, machining accuracy according to the slope is high. An appropriate tool path can be generated in a short time.

It is a figure which shows an example of the polyhedron model of a product shape. It is explanatory drawing which shows a mode that the tool path surface corresponding to a product shape is obtained. It is a figure which shows the polyhedron approximation data of a product shape model. It is explanatory drawing which shows a mode that Z map is obtained from polyhedral approximate data. It is a figure which shows the example of a combination of the figure according to the tool shape for obtaining Z map. It is a figure which shows the tool path surface of a product shape in a Z map model format. It is a figure explaining the method of obtaining the broken line path | route for producing | generating a tool path surface from the Z map model of a workpiece | work shape. It is explanatory drawing which shows a mode that a tool path surface (sweep shape) is obtained from a broken line path. It is explanatory drawing which shows a mode that the tool path surface corresponding to a workpiece | work shape is obtained. It is a figure which shows the upper end of sweep shape. It is a figure which shows the tool path surface of a workpiece | work shape in a Z map model format. It is a figure which shows the uncut part area | region which overlaps the tool path surface of each product shape and workpiece | work shape. It is a figure which shows the flow of tool path | route production | generation. It is a figure which shows the flow of contour line tool path generation. It is a figure explaining the method of classifying the uncut region.

Explanation of symbols

P Product shape polyhedron model P2 Polyhedron approximation data A Product shape tool path surface W Work shape polyhedron model B Work shape tool path surface 1 Cutting tool 2 Triangle (patch)
7 Uncut area (unprocessed area)
8 Unremoved area line 9 Grid 11 Contour line machining area 12 Machining area along shape 13 Two-dimensional area line 13a Projection line 14 Offset line 14a Projection line 15 Offset line 16 Tool path along shape 17 Contour line tool path

Claims (3)

A machining path data generation method for generating a tool path for machining an unmachined area of a workpiece with a tool of an NC machine tool based on three-dimensional shape model data,
Based on the Z map model indicated by the height information in the Z-axis direction of the product shape in the unprocessed area and a predetermined inclination angle determination value, the unprocessed area is processed along the contour process area having a large inclination and the shape having a small inclination. Divided into areas,
In the contour line machining area, a contour tool path is generated at a pitch in the Z-axis direction according to the machining conditions,
A machining path data generation method characterized in that, in the machining area along the shape, a tool path along the shape for moving the tool while changing the cutting amount is generated at a pitch according to machining conditions. In claim 1,
The adjacent grids are extracted from the group of grids arranged along the outermost periphery of the product shape Z map model of the unprocessed area at an inclination angle equal to or greater than the inclination angle determination value, and this extraction process is sequentially arranged inside one grid. A machining path data generation method characterized by proceeding from the outside to the inside with respect to the grid group, and dividing the unmachined area into the contour line machining area and the shape along the shape based on the extracted grid . In claim 1 or claim 2,
In the machining area along the shape, a plurality of tools arranged at intervals inside and outside, having at least a tool path that goes around the outermost periphery of the area and a tool path that goes around the inside along the tool path. The path is set and machining is performed by sequentially shifting the tool from the outer tool path to the inner tool path.
After setting the inner and outer tool path generation lines on the Z = 0 two-dimensional plane onto which the machining area along the shape is projected, both lines are projected onto the corresponding product shape model from the two-dimensional plane, and the product Machining path data for generating a tool path by correcting the position of the line on the two-dimensional plane so that the interval between the internal and external projection lines on the shape model falls within a predetermined range over the entire circumference. Generation method.

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