JP3383862B2 - Method and apparatus for generating tool path for NC machining - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to NC machining for producing a safe and reliable tool path in consideration of interference / collision at high speed in machining by cutting, grinding, electrical machining by electric discharge, etc. TECHNICAL FIELD The present invention relates to a tool path generation method and device for a tool.

[0002]

2. Description of the Related Art As a conventional tool path generation method in curved surface processing, for example, the following method is known in the generation of a tool path for NC processing in die manufacturing.

As a first method, as shown in FIG. 17, a tool center point is provided on a die surface 2 to be machined by the tool 1,
The intersection of the reversal tool shape 3 arranged at a certain interval and the perpendicular line on each grid point of the XY plane is obtained, and the Z-map point 4 having the maximum Z value of each grid point is set as an offset point, and that point of the tool There is a method in which the center point is used or the offset surface 5 is further generated from the offset point, and the tool path is generated using the offset surface 5 as the center point of the tool 1.

As a second method, as shown in FIG. 18, an offset polyhedron 7 is generated from an offset point 6 offset by the tool radius in the normal direction of the die surface 2 to be processed,
A method is known in which an intersection line 8 between the offset polyhedron 7 and the cross section to which the tool 1 is to be moved is obtained and a tool path is generated with the intersection line 8 as the center point of the tool 1.

[0005]

However, in the first method, since the tool path is expressed as the maximum Z value on the grid point, that is, the data of the Z-map point 4,
As shown in FIG. 19, the point of the shape portion 9 in which the die surface 2 to be processed is overhung cannot be obtained. Further, in order to generate the offset point (Z-map point 4) and the offset surface 5 for performing precision machining, it is necessary to reduce the arrangement interval of the reversing tool 3 and the grid interval in the XY plane, and therefore, the computer. There is a problem that a large amount of memory is required and the calculation processing time increases.

Further, in the second method, since the offset polyhedron 7 which is the center of the tool in the normal direction of the mold surface 2 is to be generated, depending on the shape of the mold surface 2, as shown in FIG. Since the offset polyhedron 7 may overlap or interfere with the die surface 2, it is difficult to generate a reliable tool path, and in order to generate an offset polyhedron for performing precision machining, There is a problem that a large number of small memories must be generated, a large amount of memory is required in the computer, and the calculation processing time increases, as in the first method.

The present invention has been made in view of the above points, is not affected by the shape of an object to be machined, can cope with interference and collision, and can also be developed into simultaneous 5-axis control machining, and further, high speed. An object of the present invention is to provide a tool path generation method and an apparatus for NC machining which can be calculated.

[0008]

In order to solve the above problems, a tool path generation method for NC machining according to claim 1 sets machining plane information and tool shape information, and An inclusion sphere model is generated by including the machining surface with an inclusion sphere having a specified radius based on the information, and for a specified machining line, the distance between the center of the inclusion sphere and the tool on the machining line is set. Based on this, the tool path is calculated so that the inclusion sphere and the tip of the tool come into contact with each other. Further, a tool path generation method for NC machining according to claim 2, in the configuration of claim 1, in each tool position on the calculated tool path, each inclusion sphere of the inclusion sphere model, the tool and the tool Interference between the machining surface and the tool and a member moving together with the tool is detected based on a distance between the tool and a member moving together, and the tool path is corrected so as to avoid the interference. .

According to a third aspect of the present invention, there is provided an NC machining tool path generation device for generating an inclusion sphere model by including the machining surface with an inclusion sphere having a designated radius on the basis of information on the machining surface. Part and a designated machining line, a tool for calculating a tool path based on the distance between the center of the inclusion sphere and the tool on the machining line such that the inclusion sphere and the tip of the tool are in contact with each other. And a route calculation unit. Also, claim 4
A tool path generation device for NC machining according to claim 3,
In the configuration, the tool path calculation unit further, based on the distance between each included sphere of the included sphere model and the tool and a member that moves together with the tool at each calculated tool position on the tool path. It is characterized in that interference between the machining surface and the tool and a member that moves together with the tool is detected, and the tool path is corrected so as to avoid the interference.

Here, the processed surface includes a curved surface, a flat surface, and the like, and the sphere includes an ellipsoid . In addition, the tool has a cylindrical shape like a flat end mill,
A ball end mill whose tip is spherical, a radius end mill whose tip outer peripheral corner is R,
There is a spheroidal end mill such as an elliptical end mill.

[0011]

With this configuration, according to the invention of claim 1 or 3, since the machined surface is modeled by including it as a sphere, the sphere can be represented by a center point and a radius. , The tool path can be easily calculated based on the distance between the center of the inclusion sphere on the machining line and the tool, and according to the invention of claim 2 or 4, each tool position on the tool path In, in, based on the distance between each inclusion sphere of the inclusion sphere model and the tool and the member that moves with the tool, it is possible to easily detect the interference between the tool and the member that moves with the tool and the machining surface. Can be modified.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

First, the basic principle of the present invention will be described with reference to FIGS.

Since the sphere can be represented by the center point and the radius, as shown in FIG. 1, the surface of the workpiece (the mold curved surface 11) on which the machining tool 10 moves is included in the inclusion sphere S for modeling. By doing so, the tool path (position) is the inclusion sphere S
Distance between center points of radius SR and tool 10 (sphere with radius CR) D ₁
It can be easily calculated by Further, the interference at the time of processing can be easily obtained by calculating the distance D ₂ between the inclusion sphere S and the tool 10 and the holder 12 (cylinder).

Next, the calculation principle of the present invention will be described with reference to FIG. 2 by taking the case of generating a tool path for machining as an example.
Note that FIG. 2 shows a cross section including the machining direction and the Z-axis, and SP ₁ , SP ₂ , and SP _{3 in} the figure represent machining surfaces (mold curved surface 1
1) the center point of the inclusion spheres S ₁ , S ₂ and S ₃ including SR, SR ₁ is the radius of the inclusion sphere S ₁ (amount of uncut portion), CR ₁ is the radius of the tool 10,
A line segment L ₁ represents a tangent line of the inclusion spheres S ₁ and S ₂ , and points A and B represent contact points.

The tool path may be obtained by finding the center position CP ₁ of the tool 10. Since the tool 10 moves on the inclusion sphere S, first, the vector V of the tangent line L ₁ tangent to the spheres S ₁ and S ₂ is obtained. Ask for ₁ . This than L ₁ // L _2, perpendicular vector V ₂ of _{V 1 = SP 2 -SP 1 V} 1 also when the V ₃ to the vertical vector of cross, with _{V 2 = V 1 × V 3} ( cross product) I want it. As a result, the center point CP ₁ of the tool is obtained by CP ₁ = SP ₁ + (V ₂ · (SR ₁ + CR ₁ )). If this is sequentially performed in the machining direction as S ₁ , S ₂ , S _3, ..., A tool path having a predetermined uncut amount can be generated.

A specific embodiment of the present invention will be described below with reference to FIGS. 3 to 16. In this example,
NC for generating tool paths for curved surface machining in die manufacturing
In the machining tool path generation device, a normal simultaneous three-axis control machining without tool attitude control is performed, and a case where a machining tool uses a ball end mill whose tip shape becomes a sphere during rotation will be described as an example.

As shown in FIG. 3, the tool path generating apparatus 13 according to the present embodiment is a processing object (mold curved surface) processed by a tool.
The inclusion sphere model generation unit 14 that includes and models the surface of the workpiece by a sphere having a specified radius based on the surface information of the object, and the position and orientation of the tool that moves on the inclusion sphere using the generated inclusion sphere. That is, based on the tool path calculation unit 15 for calculating the path and the calculated tool path,
It is roughly configured by an interference detection avoidance calculation unit 16 which detects interference between a tool, a holder, a spindle head and the like, a workpiece and a jig for fixing the same, and calculates the avoidance position and posture if there is interference. Then, in the tool path generation device 13, an external data input section 17 for inputting information of the die surface from the outside such as a CAD system and a post processing section 18 for converting the generated tool path into machine data corresponding to the processing machine used. Are connected.

As shown in FIG. 4, the curved surface inclusion sphere model generation unit 14 includes a curved surface element calculation unit 19 and a surface element center position calculation unit 20.
, The inclusion sphere radius calculation unit 21, and the inclusion sphere radius determination unit 22
And a curved surface surface element division calculation unit 23, and a curved surface inclusion sphere model is generated by the following procedure.

That is, as shown in FIG. 5, the mold curved surface 11 input from the CAD system or the like as external data by the external data input unit 17 includes some basic elements, that is, surface elements U _m (or curved surface segments). (Sometimes called)
The curved surface area calculation unit 19 first calculates this surface element U _m .

Next, as shown in FIG. 6, an inclusion sphere S _m is generated for each calculated surface element U _m . The inclusion sphere S _m calculates the center position of each surface element U _m by the surface element center position calculation unit 20, considers a sphere including the four end points of the surface element U _m with this center position as the center point SP _m , and includes the inclusion sphere. The radius calculation unit 21 calculates the radius value SR _m .

Then, in the included sphere radius determination section 22, the calculated radius value SR _{m of the} sphere is compared with the previously input uncut amount (maintenance amount) in the main processing, and the radius value SR _m is cut. If it is smaller than the remaining amount, the radius value is changed to the uncut amount and the process ends. If the radius value SR _m is larger than the uncut amount, the curved surface surface element division calculation unit 23 determines the inclusion sphere.
The surface element U _{m included} in S _m is further divided as shown in FIG.
Similar to the above, the process of obtaining the center position and the radius value of the containing sphere for each divided surface element u is repeated until the radius value becomes smaller than the uncut amount, and an included sphere having the uncut amount as the radius is generated.

By the above processing, the mold curved surface to be processed is
It is possible to generate a curved surface inclusion sphere model by including all the spheres with the uncut amount of spheres.

As shown in FIG. 8, the tool path calculation unit 15
It includes an inclusion sphere extraction unit 24, an inclusion sphere sorting unit 25, a tool center position calculation unit 26, and an undercut detection unit 27, and calculates the tool path in the following procedure.

First, as shown in FIG. 9, the inclusion sphere extracting unit 24 looks at the mold curved surface 2 to be processed on the XY plane, determines a processing line on the plane, and determines from the previously generated curved inclusion sphere model. The curved surface inclusion sphere model related to this processing line is extracted.

Then, the included spherical body sorting unit 25 arranges the extracted curved surface spherical body models in the processing direction.
As a result, the curved surface inclusion sphere models required for tool path generation are arranged in order in the machining direction.

Next, the tool center position calculator 26 calculates the tool path moving on the curved surface sphere model, that is, the center position of the tool. An example of calculation for obtaining the center position of the tool will be described below.

As shown in FIG. 10, the curved surface inclusion sphere model is updated as a new inclusion sphere S'having a radius which is a value obtained by adding the radius CR of the tool 10 to the radius SR of the inclusion sphere S. As shown in FIG. 11, the new inclusion sphere S ′ (S ₁ ′,
S ₂ ′, S ₃ ′ ...) is cut by a cross section including the machining line and the Z axis,
The center point and radius of the circle C (C ₁ , C ₂ , C ₃ ...) Appearing on the cross section are calculated. The center point of the circle C is a point obtained by dropping the center point of the inclusion sphere perpendicular to the cross section, and the radius is obtained from the distance obtained by dropping it vertically and the radius value of the inclusion sphere S ′. As shown in FIG. 12, the arc from the contact points of the circles C ₁ , C ₂ , and C ₃ obtained is the center path of the tool 10, but the tool path required for NC machining is a position command, so the arc is It has to be approximated and there is a lot of data. Therefore, as shown in FIG. 13, contact points P ₁ , P ₂ , P ₃ , P ₄ are obtained from the tangents of circles C ₁ , C ₂ , C ₃ , and these contact points P ₁ , P ₂ , P ₃ , P ₄ are If the center position of the tool 10 is used, the data will be much smaller than when the arc is approximated.
The calculation for obtaining this contact point can also be performed by simpler calculation than the information on the center point and radius of the circle.

After the center position of the tool 10 is obtained, the undercut detection unit 27 checks whether there is an undercut (overcutting) on the peripheral die surface at that position.
This is as shown in Fig. 14, at the determined tool position,
It suffices to extract the curved surface containing spheres (see the shaded area in the drawing) related to the tool 10 and obtain the distance between the center points of these curved surface containing spheres and the tool 10. Then, the calculated distance between the center points is
If it is larger than the sum of the radius values of both the tool 10 and the curved surface-containing sphere, it is determined that there is no undercut, and the processing ends.
If it is smaller, it is determined that there is an undercut for the curved surface containing sphere, and the center position of the tool 10 is moved in the Z-axis positive direction until the undercut disappears.

By the above processing, it is possible to generate a tool path (position) with a constant amount of uncut portion and no undercut (overcut).

As shown in FIG. 15, the interference detection avoidance calculation unit 16 includes a finite cylinder generation unit 28, an interference inclusion sphere extraction unit 29, an interference inclusion sphere determination unit 30, an interference amount calculation unit 31, and an interference avoidance unit. A member provided with a calculation unit 32 and a surface element division calculation unit 33, and a member that moves together with a tool such as a tool and a holder, a spindle head, and a member that is mounted on a mold curved surface such as a mold curved surface and a mounting jig. The detection and avoidance of the interference is performed by the following procedure.

As shown in FIG. 16, the finite cylinder generating unit 28 defines the base end, the holder, and the spindle head of the tool 10 by finite cylinders T ₁ , T ₂ , and T ₃ , respectively.

Next, the interference inclusion sphere extraction unit 29 generates the inclusion sphere S including the mold curved surface 11 and the mounting jig (not shown) in a predetermined plane element unit, or the curved surface inclusion sphere model generation. The inclusion sphere S ₁ that intersects or is in contact with the defined finite cylinders T ₁ , T ₂ , T ₃ is extracted from the curved inclusion sphere model generated in the part 14 (FIG. 16 shows the finite cylinder T ₁ and the inclusion sphere S ₁ Indicates when and intersect). This calculation, as shown in FIG., The central axis TA of the center point SP ₁ of inclusion sphere S ₁ finite cylinder T ₁
Find the distance of ₁ . If there is no included sphere that intersects or is in contact with the finite cylinder, it is determined that there is no interference, and the processing ends.

If there is an inclusion sphere that intersects or is in contact with the finite cylinder, the interference inclusion sphere determination unit 30 determines that there is a possibility of interference, and the surface element division calculation unit 23 extracts it to detect the interference site. The surface element included in the included sphere S ₁ is divided to generate a sphere including the divided surface element,
Extract the inclusion sphere that intersects or touches the finite cylinder.
This process is repeated until the radius of the containing sphere reaches the specified interference determination distance to determine the interference site.

When the interference portion is determined, the interference amount calculating unit 31 calculates the amount of interference and moves the tool path (position) in the Z-axis positive direction to a position where it does not interfere. The amount of interference can be easily obtained by calculating the distance between the sphere and the cylinder.

As can be seen from the above, by including the mold curved surface in the spherical model, the machined surface can be expressed without being influenced by the shape, and thus the tool path can be generated without any problem.

Further, since the calculation in each process can be performed only by the four arithmetic operations (addition, subtraction, multiplication, division), it is possible to perform high speed from the generation of the tool path to the detection and avoidance of the interference.

Since the interference is detected and avoided at the same time when the tool path is generated, the generated tool path is safe and reliable.

The radius value of the curved surface inclusion sphere model can be arbitrarily set, and it is possible to handle from rough machining to finish machining in die machining.

Further, in the present embodiment, as an example, the case of performing the three-axis control is described, but the present invention generates the inclusion sphere including the processed object so that the center point is on the surface of the processed object. By doing so, the surface information (surface normal, etc.) of the processed object can be added to the information of the included sphere, and effective information when controlling the attitude of the tool can be obtained, so simultaneous 5-axis control is easy. Can correspond to.

[0041]

As described in detail above, according to the tool path generating method and apparatus for NC machining of the present invention, a curved surface to be machined such as a metal mold is represented by a spherical body, and therefore, a machined object. Can be expressed regardless of the shape, and the tool path can be generated without any problem. Moreover, since the tool path is calculated from the included sphere, it is possible to generate the tool path of the complex curved surface. Since the tool path (position) and interference are calculated by calculating the distance from the center point of the modeled sphere,
The calculation method is simple and high-speed calculation is possible. Furthermore, by generating a sphere containing the curved surface to be processed so that the center point is on the surface of the curved surface, it is possible to add the surface information (surface normal etc.) of the processed object to the information of the containing sphere. Since it is possible to obtain effective information when controlling the attitude of the tool, it is possible to easily cope with 5-axis control.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the basic principle of the present invention by taking a case of generating a tool path for machining as an example.

FIG. 2 is an explanatory diagram showing the calculation principle of the present invention by taking as an example the case of generating a tool path for machining.

FIG. 3 is a block diagram showing a configuration of a tool path generation device according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a curved surface inclusion sphere model generation unit of the apparatus of FIG.

FIG. 5 is a diagram showing a surface element that constitutes a curved surface of a mold according to an embodiment of the present invention.

FIG. 6 is a diagram showing an inclusion sphere generated for each surface element of FIG.

FIG. 7 is a diagram showing a state where the surface element of FIG. 5 is further divided.

8 is a block diagram showing a configuration of a tool path calculation unit of the apparatus shown in FIG.

FIG. 9 is a diagram showing a curved surface inclusion sphere model relating to a processing line when the mold curved surface is viewed on the XY plane.

FIG. 10 is a diagram showing an inclusion sphere for obtaining a tool center position of a curved inclusion sphere.

11 is a diagram showing a circle that appears in a cross section when the inclusion sphere of FIG. 10 is cut in a cross section including the Z axis.

FIG. 12 is a diagram showing a tool center path formed by the circular arcs of the circle of FIG. 11;

13 is a diagram showing a tool center path by a tangent line of the circle of FIG.

FIG. 14 is a diagram showing a curved surface sphere model related to a tool at a processing point.

15 is a block diagram showing a configuration of an interference detection avoidance calculation unit of the apparatus of FIG.

FIG. 16 is a view showing a mold surface that interferes with a finite cylinder showing a tool, a holder, and a spindle head, and an inclusion sphere of a mounting jig.

FIG. 17 is a diagram showing a conventional tool path generation method by a reverse offset Z-map method.

FIG. 18 is a diagram showing a conventional tool path generation method by a polyhedral approximation method.

FIG. 19 is a diagram showing a case where the mold surface has an overhang-shaped portion in the tool path generation method shown in FIG. 17;

20 is a diagram showing a case where the offset polyhedrons interfere with each other in the tool path generation method shown in FIG.

[Explanation of symbols]

10 Tool 11 Mold curved surface 13 Tool path generation device 14 Included sphere model generation section (15 Tool path calculation section 16 Interference detection avoidance calculation section S Included spheres T ₁ , T ₂ , T ₃ Cylinder

Continued front page    (72) Inventor Rokuro Kimura               Aichi Prefecture Aichi District Nagakute Town               Address 1 Toyota Central Research Institute Co., Ltd.                (56) References JP-A-6-83422 (JP, A)

Claims (4)

(57) [Claims] 1. Information of a machining surface and shape information of a tool are set, and based on the information of the machining surface, an inclusion sphere model is generated by including the machining surface by an inclusion sphere having a specified radius and is specified. For the machining line, a tool path is calculated based on the distance between the centers of the inclusion sphere and the tool on the machining line such that the inclusion sphere and the tip of the tool are in contact with each other. A characteristic tool path generation method for NC machining. 2. At each tool position on the calculated tool path
The inclusion spheres of the inclusion sphere model, the tools and
Based on the distance between the
Between the processing surface and the tool and the member that moves with the tool
The tool path is detected to detect interference and avoid it.
For NC processing according to claim 1, characterized in that
Tool path generation method. 3. An inclusive sphere model generation unit for generating an inclusive sphere model by including the processed surface by an inclusive sphere having a specified radius based on information on the processed surface, and a specified processing line on the processed line. The inclusion sphere and the tool based on the distance between the center of the inclusion sphere and the center of the tool.
A tool path generation device for NC machining, comprising: a tool path calculation section that calculates a tool path so that the tool path is in contact with the tip of the tool path. 4. The tool path calculation unit further calculates
For each tool position on the tool path,
Move with each tool and each of the included spheres
Based on the distance to the member, the machined surface and the tool
And interference with members that move with the tool are detected, and
Characterized in that the tool path is modified to avoid interference
A tool path generation device for NC machining according to claim 3.
Place