JP2707781B2 - 3D shape processing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a three-dimensional shape processing method, and more particularly, to a method of automatically obtaining a processing order, a tool movement path, and the like from three-dimensional shape data. The present invention relates to a three-dimensional shape processing method in a mold CAD / CAM system.

[Prior art] Conventionally, for example, APT (A
2. Description of the Related Art There is known an APT system that performs geometric processing such as calculating tool movement path data from tool movement described in a language called utomecally programmed tools language.

EXAPT (Extended Subs), which expands the above APT system to process processing conditions such as processing speed
et APT) systems are known.

[Problems to be Solved by the Invention] In the above-described APT system and EXAPT system, when creating a program, it is necessary for a human to directly define the movement of a tool.

However, there is a problem that it is very troublesome for a person to define the movement of a tool for machining a three-dimensional shape having a free-form surface such as a mold.

Accordingly, an object of the present invention is to provide a three-dimensional shape processing method that can automatically obtain a tool path or the like simply by giving three-dimensional shape data.

Means for Solving the Problems According to a first aspect of the present invention, a three-dimensional shape defined on a three-axis orthogonal coordinate system of X, Y, and Z is cut by a tool whose central axis is parallel to the Z-axis. In the three-dimensional shape processing method to be performed, for each surface constituting the three-dimensional shape, assuming a minimum rectangular parallelepiped region including each surface and having sides parallel to the X, Y, Z axes, the positions of these minimum rectangular parallelepiped regions An initial order determining step of determining the initial order of each surface from the relationship, and focusing on two adjacent surfaces, and determining a priority order between the two surfaces from the inclination of the two surfaces with respect to the Z axis at a boundary portion where the two surfaces are adjacent. Three-dimensional shape processing, comprising: a priority order determining step; and a cutting order determining step of correcting the initial order based on the priority order, and determining the order of each surface after the correction as the order of cutting each surface. Provide a way.

In the above configuration, the initial order determining step arranges the minimum rectangular parallelepiped areas in descending order of their minimum Z-axis coordinate values, and arranges the minimum rectangular parallelepiped areas having equal minimum Z-axis coordinate values in descending order of their maximum Z-axis coordinate values. And arranging the surfaces corresponding to the order of the minimum rectangular parallelepiped regions that have been arranged, and determining the order as the initial order.

Further, the priority order determining step is a state in which one of the two adjacent surfaces is on the side where the Z-axis value increases from the boundary between the two surfaces and is close to being somewhat parallel to the Z-axis;
And determining that the one surface has a higher priority than the other surface when the other surface of the two surfaces is close to being somewhat perpendicular to the Z axis;
One of the surfaces is on the side where the Z-axis value decreases from the boundary between the two surfaces and is close to being somewhat parallel to the Z-axis, and the other surface of the two surfaces is somewhat to the Z-axis. Determining that the other surface has a higher priority than the one surface when the state is close to vertical.

[Operation] In the three-dimensional processing method of the present invention according to the first aspect,
When a three-dimensional shape is given, the optimal order for processing each surface constituting the three-dimensional shape is automatically determined by a two-stage process of determining the initial order and correcting the order.

In the three-dimensional processing method of the present invention according to the second aspect,
The optimal cutting direction and feed direction when the cutting reference coordinate plane cuts the XY plane with a tool whose central axis is parallel to the Z axis,
It is automatically determined from information on a point on the loop of the plane and a minimum rectangular parallelepiped region including the plane.

Therefore, it is possible to automatically obtain the path of the tool simply by giving the three-dimensional shape data.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples shown in the drawings. Note that the present invention is not limited by this.

In this embodiment, as shown in FIG. 6, a mold (51) having a three-dimensional shape defined on a three-axis orthogonal coordinate system of X, Y, and Z is used. The three-dimensional shape processing method of the present invention is applied to a mold CAM system for cutting using a simple ball end mill (50).

FIG. 1 is a flowchart showing the flow of processing according to the present invention.

In step (1), the three-dimensional shape of the mold is input as a wire frame model. This allows, for example, data of a wireframe model created by a human being to be read using a CAD system via a floppy disk.

In step (2), the wire frame model is converted into a B-Reps. (Boundary Representation) model, and a surface number n is generated. This processing can be performed using a conventionally known conversion method.

In step (3), a curved surface f (n) is generated for each surface number n of the B-Reps. Model. In addition, those curved surfaces f
The minimum rectangular parallelepiped region including (n) (hereinafter referred to as a box)
B (n) information is generated. This processing can be performed using a conventionally known generation method. FIG. 7 shows one curved surface f (n) and a box B (n). Box B (n) contains the minimum values Xmin, Ym of the X, Y and Z axes, respectively.
Point Pmin with in and Zmin and maximum values Xmax, Ymax and Z
and a point Pmax having max.

In step (4), each surface f
The order of cutting (n) is initially determined. That is, each curved surface f (n) is assigned an order O (n). The process of determining the initial order will be described later with reference to FIG.

In step (5), the initial order O (n) is corrected to obtain an optimal order O (n). The processing of the order correction will be described later with reference to FIG.

In step (6), a curved surface f (n) is extracted according to the corrected order O (n).

In step (7), a cutting reference coordinate plane, a cutting direction, and a feed direction are determined as a cutting method for the extracted curved surface f (n). The processing for determining the cutting method will be described later with reference to FIG.

In step (8), an intersection between the straight line perpendicular to the cutting reference coordinate plane and the plane is calculated, and a tool path is obtained as a series of points.

In step (9), it is checked whether the curve f (n) to be taken out still exists, and if there is, the program returns to step (6) to take out. If not, the process ends.

As described above, the tool paths for all the curved surfaces f (n) can be obtained. Therefore, after all, the human only needs to input the three-dimensional shape of the mold.

FIG. 2 is a flowchart showing the flow of the process for determining the initial order in step (4).

In step (11), the minimum Z-axis coordinate value Zmin and the maximum Z-axis value of each box B (n) are obtained from the box information of each curved surface f (n).
The axis coordinate value Zmax and the corresponding surface number n are extracted.

In step (12), Zmin, Zmax and the surface number n are rearranged in descending order of the minimum Z-axis coordinate value Zmin.

In step (13), it is checked whether there is a part having the same minimum Z-axis coordinate value Zmin in the rearrangement result. If not, the process ends. If there is, go to the next step (14).

In step (14), Zmi in the same part of the minimum Z-axis coordinate value Zmin in the descending order of the maximum Z-axis coordinate value Zmax.
Rearrange n, Zmax and surface number n.

As described above, the initial order O (n) of each phase f (n) is determined.

For example, as shown in FIG. 8, a curved surface f having a surface number n = 1
(L) and a curved surface f (2) having a surface number n = 2, and a box B including the curved surfaces f (1) and f (2)
Assuming that the minimum Z-axis coordinate values Zmin of (1) and B (2) are equal, the surface f
(2) Order O (2) = 1, Curved Surface f (1) Order O (1)
= 2 is the initial order.

Next, FIG. 3 is a flowchart showing a flow of the order correction processing of the step (5).

The general flow of the processing is as follows: when focusing on a certain surface, the priority is checked for the surface of interest and the surface that is later in the order than the surface in question. The correction is repeatedly performed.

In step (16), the pointer i is set to 1. The pointer i points to the curved surface f (n) in the order O (n) = i as the curved surface of interest. Therefore, the first surface of interest is a surface of order O (n) = 1. In the following, a curved surface f (n) in order O (n) = _i is represented by fi.

In step (17), it is determined whether i is smaller than the number of surfaces, that is, whether the surface of interest reaches the last surface. If it has arrived, there is no more curved surface to be compared, and the process ends. If not, go to the next step (18).

In step (18), the flag break indicating whether the order has been corrected is turned OFF (indicating that no correction has been performed).
Initialize to The pointer j is set to i + 1. The point j indicates a curved surface to be compared with the curved surface f (n) in order O (n) = j. Thus, the surface of the first comparison, will point the curved surface f _{i + 1} of the next sequential face f _i to the target. In the following, a curved surface f (n) in order O (n) = j
_Is represented by f _j .

In step (19), it is determined whether the pointer j is smaller than the number of faces, that is, whether the face to be compared reaches the last face. When it reaches, to update the surface of interest,
Proceed to step (24). If not, the process proceeds to step (20) for comparison.

In step (20), the priority order between the two faces f _j to be compared with the face f _{i of} interest is determined. This priority determination process will be described later with reference to FIG.

In step (21), it is checked whether or not the order is required to be corrected in step (20). If correction is necessary, the process proceeds to step (23). If correction is unnecessary, the process proceeds to step (22).

In step (22), the pointer j is incremented. That is, the curved surface f _j to be compared is shifted to the next curved surface. Then, the process returns to the step (19).

In step (23), the order is corrected. That is,
As shown in FIG. 9, the surface f _i, ie, the surface f
(A) by the take-out, the order (i + 1) ~ order to move j faces the (b) ~f (m) Previous one of storing the curved surface f to a the order of curved surface f _j (a) . Then, the flag break is set to ON (indicating that correction has been made).

In step (24), the value of flag break is checked, and if flag break = ON, the process returns to step (17),
If the flag break = OFF, proceed to step (25).

In step (25), and increments the pointer i, and advances the curved f _i of interest to the curved surface of the next order. Then, the process returns to the step (17).

As described above, the order O (n) of each curved surface f (n) is corrected, and the optimal order is determined.

For example, in FIG. 10, the curved surfaces f (a), f (b), f
In (c), since the Zmin and Zmax of the respective boxes are equal, the cutting order at the stage where the initial order is determined is not always appropriate, but the order of the above-mentioned order correction becomes the optimum order.

Next, FIG. 4 is a flowchart showing the flow of the priority order determination process in the step (20).

In step (26), calculates the curved f _i of interest, the average normal vectors N _i to compare curved f _j, the inner product I _i of the unit vector U _z of N _j and Z-axis direction, the I _j.

In step (27), a check is made from I _i <0 and I _j > 0. When this condition is satisfied, as in case-1 shown in FIG. 11 (a), the surface f _i of interest is a surface on which cutting is not performed (downward surface), and the surface f _j to be compared performs cutting. Plane. Surfaces that are not cut are removed later in the sequence. Therefore, the process proceeds to step (32) in which it is determined that correction is necessary. On the other hand, when this condition is not satisfied, the process proceeds to step (28) to check another condition.

In step (28), a check is made from I _i > 0 and I _j > 0. When this condition is not met, to compare surface f _j is a surface that does not perform cutting (downward surface). In this case, since the surface on which cutting is not performed is in the later order, the process proceeds to step (33) which does not require correction. On the other hand, when this condition is met, we check for other conditions,
Proceed to step (29).

In step (29), the normal vector N _i, N _j from the surface f _i, f _j
Of each of the cutting reference coordinate planes P _Li and P _Lj are determined. The cutting reference coordinate plane is any one of the XY plane, the YZ plane, and the ZX plane.

In step (30), the relationship between the two surfaces is as shown in FIG.
It is shown in (c). It is determined whether it is case-2 or case-3. First, by checking the cutting reference coordinate planes P _Li , P _Li , a rough check is made as to whether or not case 2 or case 3 will be obtained. As shown in FIG. 11 (b), in case-2,
Face f _i, f _j are adjacent, cutting reference coordinate plane PL _i is in the X-Y plane, the cutting reference coordinate plane PL _j is Y-Z plane or Z-X plane. As shown in FIG. 11 (c), when the Case-3, the plane f _i, f _j are adjacent, cutting reference coordinate plane PL _i is Y-
In Z plane or Z-X plane, the cutting reference coordinate plane PL _j is X-
This is the Y plane. If these conditions are not satisfied, case-
Neither is 2, case-3. So, step (31)
Proceed to.

If these conditions are satisfied, there is a possibility that either case-2 or case-3 will occur. Therefore, the ridge line e between the faces f _i and f _j
And the calculations shown in FIGS. 12 (a) and 12 (b) are performed.
If there is no edge line between the faces f _i and f _j , the case-
2, Case-3 does not occur.

FIG. 12 (a) shows the case-edge of FIG.
And shows a vector for determining calculate how a state of 2 or Case-3, the midpoint of P _m are ridgeline e, T _m is the tangent vector of the ridge line e at the midpoint P _m, U _z is A unit vector in the Z-axis direction, G _x is a vector obtained by normalizing T _m × U _z (a cross product vector of T _m and U _z ), and S _i and S _j are surfaces f _{i at the} midpoint P _m and
This is a vector obtained by normalizing a tangent vector in a direction crossing each edge of f _j .

FIG. 12 (b) shows S _k on a coordinate plane consisting of U _z and G _x.
The figure shows the calculation of the angle θ _k between the vector obtained by projecting (k = i, i) and U _z (that is, the angle between the plane f _k and the U _z axis around the ridge line e). The condition for the case-2 or case-3 shown in FIG. 11 is determined as follows.

case-2 condition -Δθ <cosθ _i <Δθ and 1−Δθ <cosθ _j <1 case-3 condition -1 <cosθ _i <-1 + Δθ and -Δθ <cosθ _j <Δθ where Δθ is 0 <Δθ < {Z} / Z constant The above or when satisfying cose-2 or case
It is determined to be −3. If not satisfied, it is determined that it is not case-2 or case-3. And step (31)
Proceed to.

In step (31), if the result of the determination in step (30) is case-2 or case-3, the process proceeds to step (32); otherwise, the process proceeds to step (33).

 In step (32), the value to be returned is set to “necessary for modification”.

In step (33), the value to be returned is set to "unnecessary to modify".

Next, FIG. 5 is a flowchart showing the flow of the processing for determining the cutting method in the step (7).

In step (34), an average normal vector of the extracted surface is calculated.

In step (35), a cutting reference coordinate plane of the plane is determined based on the normal vector.

In step (36), it is checked whether the cutting reference coordinate plane is an XY plane, and if it is an XY plane, the process proceeds to step (40).
Otherwise, go to step (37).

In step (37), it is checked whether the cutting reference coordinate plane is a YZ plane, and if it is a ZY plane, the process proceeds to step (39).
Otherwise, go to step (38).

In step (38), the cutting direction is set to X-up (X-axis increasing direction) and the feed direction is set to Z-down (Z-axis decreasing direction).

In step (39), the cutting direction is set to Y-up (Y-axis increasing direction) and the feed direction is set to Z-down.

In step (40), a point Pmax having the maximum Z value and a point Pmin having the minimum Z axis on the loop of the surface are calculated.

In step (41), the center point of the box area in the X-Y plane as shown in FIG. 13 (X _c, Y _c) and a length L _x in the X-axis direction, the length in the Y-axis direction L _y Is calculated. Then, the cutting direction and the feed direction are determined according to the following conditions.

(A) Pmin and Pmax and when Z value is the same (A) L and X-Stay up-feed direction of the cutting direction when _x ≧ L _y a cutting direction when the Y-Stay up-(b) L _x <L _y Y- up-feed direction if the Z value of the X-up (b) Pmin and Pmax are different Pmax = [Xm, Ym, Zm] as, (a) cutting direction when L _x ≧ L _y: in Xm ≦ Xc X-up Xm> Xc in X-down feeding direction: cutting direction when Ym ≦ Yc in Y-up Ym> Y-down ( i) in Yc L _x <L _y: Y- in Ym ≦ Yc in Y-up Ym> Yc down Feed direction: Xm ≦ Xc, X-up Xm> Xc, X-down As described above, the cutting reference coordinate plane, the cutting direction, and the feed direction are determined as the method of cutting the extracted surface.

Next, FIG. 14 is a block diagram of an example of a three-dimensional shape processing apparatus for performing the three-dimensional shape processing method of the present invention.

This three-dimensional shape processing device (100) includes a CPU (101),
Memory (102), interface (103), tool (10
4), tool arm (105) and work stage (106)
And a console (107) and a disk (108).

[Effects of the Invention] According to the three-dimensional shape processing method of the present invention, when a target three-dimensional shape is given, the cutting order for all surfaces constituting the shape is automatically determined, and the cutting method for each surface is determined. Is automatically determined, and the tool path is automatically calculated.

For this reason, compared to the conventional method, it is possible to promote the automation in the preparation work for machining and to shorten the time until the tool path calculation.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the flow of processing of a three-dimensional shape processing method according to one embodiment of the present invention, FIG. 2 is a flowchart of processing for determining an initial order, FIG. 3 is a flowchart of processing for order correction, and FIG. Is a flowchart of a priority order determination process, FIG. 5 is a flowchart of a cutting method determination process,
FIG. 6 is an explanatory view showing the relationship between the coordinate system, the mold, and the tool.
FIG. 8 is an explanatory diagram showing the relationship between planes and boxes, FIG. 8 is an explanatory diagram showing an example of initial order determination, FIG. 9 is an explanatory diagram showing order correction, FIG. 10 is an explanatory diagram showing a plurality of surfaces, FIG. Fig. 11 (a)
(B) and (c) are boundary condition diagrams for priority order determination,
FIG. 13 is a conceptual diagram for explaining a boundary condition determination calculation, FIG. 13 is an explanatory diagram of a box area for explaining a cutting method determination, and FIG. 14 is a three-dimensional shape for implementing a three-dimensional shape processing method of the present invention. It is a block diagram of an example of a processing device. In the figure, 100 is a three-dimensional shape processing apparatus, 50 is a ball end mill, 51 is a mold, f (n) is a surface, and B (n) is a box. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

(57) [Claims] 1. A three-dimensional shape processing method for cutting a three-dimensional shape defined on an X, Y, Z three-axis orthogonal coordinate system with a tool having a central axis parallel to the Z-axis. For each surface, an initial order determination step of assuming a minimum rectangular parallelepiped region that includes each surface and whose sides are parallel to the X, Y, and Z axes, and determines an initial order of each surface from a positional relationship between the minimum rectangular parallelepiped regions. Focusing on two adjacent surfaces, 2 is obtained from the inclination of the two surfaces with respect to the Z axis at the boundary portion where the two surfaces are adjacent.
A priority order determining step of determining a priority order between the surfaces, and a cutting order determining step of correcting the initial order based on the priority order and determining the order of the corrected surfaces as the order of cutting the respective surfaces. A three-dimensional shape processing method characterized by the following. 2. The initial order determining step arranges the minimum rectangular parallelepiped areas in the order of larger minimum Z-axis coordinate values, and arranges the minimum rectangular parallelepiped areas having the same minimum Z-axis coordinate value in the order of larger maximum Z-axis coordinate values. The three-dimensional shape processing method according to claim 1, further comprising: arranging surfaces corresponding to the order of the minimum cuboid regions that have been arranged, and determining the order as an initial order. 3. The method according to claim 2, wherein said priority order determining step comprises the steps of:
One of the surfaces is on the side where the Z-axis value increases from the boundary between the two surfaces and is close to being somewhat parallel to the Z-axis, and the other surface of the two surfaces is somewhat to the Z-axis. Determining that the one surface has a higher priority than the other surface when the state is close to vertical; and that one of the two adjacent surfaces has a Z-axis value higher than the boundary between the two surfaces. When the other surface of the two surfaces is close to being somewhat perpendicular to the Z axis, and the other surface is in a state close to being somewhat parallel to the Z axis and present on the decreasing side, the other surface is 3. The method according to claim 1, further comprising the step of determining that the priority is higher than one of the surfaces.