JPH08108345A - Cutting route preparing method and cutting simulation method for tool for nc machine tool - Google Patents

Abstract

PURPOSE: To shorten the computing time by setting a large grid interval at the time of rough machining without apprehension that the required shape is excessively cut. CONSTITUTION: The maximum value of the (z) coordinate value of the surface of a required shape is obtained per a unit square area of each grid, and the two-dimensional arrangement SH having this maximum value as an element is prepared (process 11). The minimum value of the (z) coordinate value of the surface of the shape of the tool tip is obtained per a unit square area of each grid, and the two-dimensional arrangement HL having this minimum value as an element is prepared (process 12). The lower limit (z) coordinate value of the center of the tool tip, which can pass the tool without excessively cutting the required shape at all points within a unit square area of each grid is obtained on the basis of these two-dimensional arrangement SH and HL, and the two-dimensional arrangement LI having this lower limit (z) coordinate value as an element is prepared as the cutting limit surface. The tool route (p) is prepared on the basis of this cutting limit surface LL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an NC machine tool such as an NC milling machine or a machining center, and particularly to a method for creating a cutting path and a cutting simulation method for a tool when cutting an irregular or complicated three-dimensional shape. It is about.

[0002]

2. Description of the Related Art Conventionally, an irregular or complicated three-dimensional shape that is difficult to fit as normal CAD data (for example, free-form surface shape, living thing shape, fractal shape, etc.)
If the required shape is used and the required shape is cut using an NC machine tool, the required shape, the shape of the work material, and the tip shape of the tool are all grid points as a method for easily creating the cutting path of the tool. A method of creating a cutting path of a tool (hereinafter abbreviated as a tool path) and realizing a cutting simulation is proposed by expressing the height at a two-dimensional array and performing interference calculation for each grid point. (Japanese Patent Application No. 2-32947
No. 3, "Tool Control Method for NC Machine Tools", T. Saito,
T.Takahashi: "NC Machining with G-bufferMethod", Pro
c.SIGGRAPH'91, pp.207-216, etc.).

[Creation of Tool Path] In order to obtain the tool path by this conventional method, first, the z axis of the x, y, z coordinate system is taken as the rotation axis of the tool, and a square grid is set on the x, y coordinates. Then, a two-dimensional array S (x, y) having z coordinate values (z coordinate values of the uppermost surface when a plurality of surfaces overlap) of the required shape at each grid point as elements is created. Also, for the tool tip shape, a two-dimensional array H (i, j) having z coordinate values at each grid point as elements is created. Where H
(I, j) is x when the tool tip center is the coordinate origin.
= Z coordinate value of the tool tip shape surface at the position of i = y, j = j (however, the lattice interval is a unit length of x, y, z).

At this time, the condition of the lower limit z coordinate value z _I of the tool tip center for not cutting the required shape is that all points (i, j) on the tool tip surface are required shapes as shown in FIG. It is located higher, that is, z _I + H (i, j) ≧ S (x + i, y + j) (1). Therefore, the cutting limit surface is obtained by the following equation (2).

[0005]

[Equation 1]

As a result, the point L on the cutting limit surface
_I (x, y) is read out in some order, and the tool path p is obtained from the scanning tool path or the contour tool path as described later. [Cutting Simulation] Regarding the cutting simulation, a two-dimensional array R (x, y) having z-coordinate values of the shape before cutting at each grid point as an element, a two-dimensional array H (i, j) of tool tip shapes, From the tool path p and the two-dimensional array F (x, which has the z coordinate value of the shape after cutting at each grid point as an element
y) is created.

First, the tool path p is approximated as a grid point sequence on the grid. When the work piece is cut by passing the tool tip center through one point (x _p , y _p , z _p ) among them, a two-dimensional array W (x _p , of the surface shape of the work material at that time) y _p)
Then, as shown in FIG. 11, the shape of the work material in the cut portion changes as follows. W (x _p + i, y _p + j): = z _p + H (i, j) (3) where i ² + j ² ≦ r ² and r is the tool radius. The symbol: = indicates that the variable on the left side is updated by cutting.

In reality, the portion where the surface of the work material is below the tool is not cut and the shape does not change. After all, the change in the shape of the work material is as follows. W (x _p + i, y _p + j): = min (W (x _p + i, y _p + j), z _p + H (i, j)) (4) where i ² + j ² ≦ r ² , r is the tool radius. Here, min ((expression), (expression)) is an operation that takes the minimum value of (expression) and (expression). When the initial value of W (x, y) is R (x, y) and this process is executed for all points in the grid point sequence of the tool path p, finally W
(X, y) matches the two-dimensional array F (x, y) of the shape after cutting. Note that the execution order of the processing for obtaining F (x, y) does not depend on the order of the grid point sequence of the tool path p.

[Creation of Tool Path] Furthermore, by combining the above methods, it is possible to create a tool path that avoids the collision between the work-free material and the non-blade portion of the upper part of the tool. For that purpose, a two-dimensional array U having z coordinate values of the tool upper shape (see FIG. 12) at each grid point as an element
Create (i, j). In FIG. 12, 1-1
Indicates a blade portion of the tool, and 1-2 indicates a portion without a blade on the upper portion of the tool. Here, the array U (i, j) is the z coordinate value of the tool upper surface at the position of x = i, y = j when the tool tip center is the coordinate origin. At this time, the condition of the z coordinate value z _C of the tool tip center so as not to collide with the work material is that all points (i, j) on the upper surface of the tool are located above the pre-cut shape, that is, z _C + U (i, j) ≧ R (x + i, y + j) (5). Therefore, the collision limit surface is obtained by the following equation (6).

[0010]

[Equation 2]

On the composite limit surface obtained by comparing the collision limit surface L _C (x, y) and the shaving limit surface L _I (x, y) for each grid point and taking the upper point. The tool path p that avoids the collision can be obtained by scanning the point of P in some way. Thus, each shape is z
By expressing the coordinate values (z values) in a two-dimensional array, it is possible to perform tool path creation and cutting simulation by a unified and simple method regardless of the shape and the type of tool.

[0012]

However, when the above-mentioned conventional technique is used, the following two problems occur. [Problem 1] It takes much time to create a tool path for rough machining using a thick tool and to perform a cutting simulation. This is because the amount of calculation in the case of performing the interference calculation for each grid point is proportional to the product of the number of grid points of the work material and the number of grid points of the tool tip shape. Therefore, changing the tool requires a calculation time proportional to the square of the tool diameter. However, the calculation of rough machining, which normally would not be required to have high calculation accuracy, requires more calculation time than finishing, which becomes a bottleneck in reducing the overall processing time.

Considering only rough machining, the calculation time can be shortened by increasing the grid interval and reducing the number of grid points.
However, since the height at the reduced grid point is ignored, there is a risk of cutting the required shape at this portion. Further, in the subsequent finishing process, since the accuracy is required, the lattice spacing must be reduced. At this time, it is necessary to use the simulated shape of the work material after rough machining as the shape before finish machining. However, if the lattice spacing is reduced, data will be lost and correct simulation cannot be performed during finish machining.

[Problem 2] In the cutting simulation, only the cutting conditions at the grid points are evaluated,
Any error between grid points will be ignored.
The present invention has been made to solve such a problem, and an object thereof is to reduce the calculation time by increasing the lattice spacing during rough machining without fear of cutting the required shape. It is possible to provide a method of creating a cutting path of a tool of an NC machine tool which is possible. In addition, when using the simulated shape of the work material after rough machining as the shape before finish machining, it is possible to perform a correct simulation during finish machining even if the grid spacing is small, and to accurately determine the error range. An object of the present invention is to provide a tool cutting simulation method of an NC machine tool capable of performing the above.

[0015]

In order to achieve such an object, the first invention (the invention according to claim 1) is x,
Taking the z axis of the y, z coordinate system as the rotation axis of the tool, a square grid is set on the x, y coordinates, and the maximum z coordinate value of the required shape surface is obtained for each unit square area of each grid. A two-dimensional array S _H having the maximum value as an element is created, the minimum value of the z coordinate value of the tool tip shape surface is obtained for each unit square area of each lattice, and the two-dimensional array H having this minimum value as the element _L is created, and from this created two-dimensional array S _H and H _L , the lower limit z coordinate of the tool tip center that allows the tool to pass through without cutting the required shape at all points in the unit square area of each grid A two-dimensional array L whose value is obtained and whose lower limit z coordinate value is an element
_It is assumed that _I is created as the cut-in limit surface, and the cutting path p of the tool is created from the created cut-in limit surface L _I.

The second invention (the invention according to claim 2)
Takes the z-axis of the x, y, z coordinate system as the axis of rotation of the tool,
A square grid is set on the x and y coordinates, the minimum and maximum values of the z coordinate value of the tool tip shape surface are calculated for each unit square area of each grid, and the minimum and maximum values are the two-dimensional elements. The arrays H _L and H _H are created, and the created two-dimensional arrays H _L and H _H and the pre-cutting shape that is the surface of the work material before cutting, which is obtained for each unit square area of each lattice, can be taken. From the two-dimensional arrays R _L and R _H having the lower limit value and the upper limit value of the z coordinate value as components and the cutting path p of the tool, it is the surface of the work material after cutting for each unit square area of each lattice. obtains the lower limit and the upper limit of the z coordinate value is cutting after the shape can take, is obtained so as to create a two-dimensional array F _L and F _H to components of the lower and upper limits.

The third invention (the invention according to claim 3)
Takes the z-axis of the x, y, z coordinate system as the axis of rotation of the tool,
A square grid is set on the x and y coordinates, and the maximum z coordinate value of the required shape surface is obtained for each unit square area of each grid.
A two-dimensional array S _H having this maximum value as an element is created, and z of the tool tip shape surface is prepared for each unit square area of each grid.
The minimum value of the coordinate values is obtained, a two-dimensional array H _L having this minimum value as an element is created, and the created two-dimensional arrays S _H and H _L
From, the lower limit z-coordinate value of the tool tip center that allows the tool to pass without cutting the required shape at all points in the unit square area of each grid is obtained, and a two-dimensional array having this lower limit z-coordinate value as an element While making L _I as a shaving limit surface,
Each unit square area of the grid for determining the minimum value of the z coordinate values of the tool upper shape is not part of the blade of the tool upper part to create a two-dimensional array U _L to the minimum value as an element, and this creation 2 From the dimensional array U _L and the two-dimensional array R _H having the upper limit of the z coordinate value that can be taken by the pre-cutting shape that is the surface of the work material before cutting, which is obtained for each unit square area of each grid, as a constituent element , The lower limit z coordinate value of the tool tip center that allows the tool to pass without collision between the work material and the tool upper portion at all points in each unit square area of each lattice, and this lower limit z coordinate value is used as an element. The two-dimensional array L _C is created as the collision limit surface, and the cutting path p of the tool is created from the collision limit surface L _C and the cut-in limit surface L _I.

[0018]

Therefore, according to the present invention, in the first invention,
A two-dimensional array S _H having the maximum value of the z coordinate value in the unit square area of each grid of the required shape surface as an element, and the minimum value of the z coordinate value in the unit square area of each grid of the tool tip shape surface as the element The cutting limit surface L _I is created from the two-dimensional array H _L and the cutting path p of the tool is created from the created cutting limit surface L _I.

According to the second aspect of the invention, the two-dimensional arrays H _L and H _H having the minimum and maximum values of the z-coordinate value in the unit square area of each grid on the surface of the tool tip shape and each grid of the shape before cutting are used. Two-dimensional arrays R _L and R whose constituent elements are the lower limit value and the upper limit value that can be taken by the z coordinate value in the unit square area of
And _H, and a cutting path p of the tool, the two-dimensional array F _L and F _H to components lower limit and the upper limit value z-coordinate values can take on the unit square area of each grid of cutting after the shape is created It

Further, in the third invention, the two-dimensional array S _H having the maximum value of the z coordinate value in the unit square area of each lattice of the surface of the required shape and the unit square area of each lattice of the tool tip shape surface are used. While the milling limit surface L _I is created from the two-dimensional array H _L having the minimum z coordinate value as the element, the minimum z coordinate value in the unit square area of each grid of the tool upper shape from the two-dimensional array U _L whose elements, the two-dimensional array R _H to constitute the upper limit value element z-coordinate values can take on the unit square area of the grid of the cutting front shape, the collision limitation surface L _C The cutting path p of the tool is created from the created collision limit surface L _C and the cut-in limit surface L _I.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings. In the following description, an NC milling machine or a machining center with three-axis control of x, y, and z that cuts from the upper side (the positive direction of the z-axis) with the rotation axis of the tool as the z-axis direction will be described as an example. Further, as shown in FIG. 2, in the two-dimensional array having the values in each square region as elements, the element with the subscript (a, b) is the grid point (a,
Let b) correspond to a square area having the minimum values of x and y, that is, a ≦ x <a + 1 and b ≦ y <b + 1. That is, a square grid is set on the x and y coordinates, and the unit square area of the grid point (a, b) is changed to the square area (a, b).
And

[Creation of Tool Path: First Invention] FIG. 1 shows a processing flow of the method for creating a tool path as an embodiment of the first invention. In this embodiment, first, in process 11,
For each unit square area of each lattice, the z coordinate value of the surface of the required shape (when multiple surfaces are vertically overlapped, the z
The minimum value and the maximum value of the coordinate value) are obtained, and two-dimensional arrays S _L (x, y) and S _H (x, y) having the minimum value and the maximum value as elements are created.

Now, suppose that a two-dimensional array S (x, y) having z coordinate values of the surface of the required shape at one point (for example, a center point) in each unit square area as an element is considered.
(X, y) is a z-buffer used when a parallel projection image is generated by CG (computer graphics) (a distance from the viewpoint to the target object surface is stored for each pixel 2
It is nothing but a dimensional array). Therefore, the array S (x,
The method (z buffer method, ray tracing method, etc.) widely used in CG can be applied to the creation of y). In the present embodiment, not only one point in each unit square area but also the minimum value and the maximum value for all points are necessary, and for example, the following method is used to obtain these values.

The first method is to take a plurality of sample points regularly or irregularly in a unit square area, and calculate the z coordinate value at each of these sample points using a general CG method. The minimum value and the maximum value of the z coordinate value at the sample points inside the unit square area are obtained. In this case, since the shape change between sample points cannot be dealt with, the minimum value and the maximum value are not exact, but if the number of sample points is sufficiently large, the accuracy required for many objects can be obtained. .

The second method is to apply the cross scan line method as the CG method. When an image is generated by the cross scan line method, as shown in FIG. 3, the pixel is considered as a unit square area, and all pixels projected in each unit square area of the object configured as a combination of polygonal surfaces. The visible surface is calculated as a polygonal region, and the luminance of each region is weighted by the area of the polygon and added up to obtain the luminance of each pixel. When cutting with an NC machine tool, instead of calculating the brightness and area, calculate z values at the vertices of all internal polygonal areas for each unit square area, and calculate the minimum and maximum values. Then, it agrees with the minimum and maximum values at all points within the unit square area. The example of FIG. 3 corresponds to cutting a rectangular parallelepiped placed obliquely, but in the case of the unit square area shown in FIG. 3, the z value at the point indicated by the black circle is obtained, and the minimum value among them is calculated. Find the maximum value. Assuming that the projection is from the z-axis positive direction, in this example, the innermost point A corresponds to the minimum value, and the closest point B corresponds to the maximum value.

Next, in process 12, a two-dimensional array H _L (i, j), H _H (i, j) of the tool tip shape is created. In general, the shape of the tool tip is a simple shape such as a flat surface, a spherical surface, or a conical surface, so that it can be easily obtained from the distance between the center point (rotation axis) and the four corners of each unit square area. As an example, a two-dimensional array H _L (i, j), H _H (i, j) for a ball end mill with r = 3 is shown in FIG.
It is shown in (c). When the z coordinate value of the center of the tool tip is 0, the z coordinate value h at a point away from the center by a distance d (see FIG. 4A) is calculated by the following equation (7).

[0027]

(Equation 3)

For example, H _L (0,1), H _H (0,1)
To obtain (portions marked with double circles in FIGS. 4B and 4C), (0,1), (0,2), (1,1), (1,
In the unit square area having 2 corners as 2 corners, the distance of the point closest to the tool center is d = 1 (coordinate value (0, 1)), and the distance of the farthest point is d = √5. Therefore, the minimum value and the maximum value of the z coordinate value are as follows. In addition, + ∞ is
It means that the corresponding point is outside the tool shape.

[0029]

[Equation 4]

Next, in process 13, the two-dimensional array L _I (x, y) of the shaving limit surface is calculated. Sequence L _I in this case (x, y) calculation method of the "request form S (x, y) shown in the conventional technique as a tool tip shape H (i, j) sequences from L _I (x, y) Calculation method ”. However, in this embodiment, in order to ensure that no incorporated scraping request shape at all points in the unit square area, as indicated by a thick line shape in Figure 5, two-dimensional array S _H of the maximum z value as the required shape The two-dimensional array H _L (i, j) having the minimum z value is used as (x, y) as the tool tip shape. Therefore, the array L _I (x, y) is obtained by the following equation.

[0031]

(Equation 5)

Finally, in order to obtain the tool path p, a tool path creating process 14 is performed. In this processing 14,
The tool path p is obtained using the following usage. (1) Scanning tool path This is a method of moving the tool with a constant x or y coordinate.
It is obtained by sequentially reading the elements of the array L _I (x, y) in the vertical or horizontal direction. (2) Contour line tool path This is a method of moving the tool on a horizontal plane (z coordinate is constant). The path is obtained by tracing the point having this z coordinate on the array L _I (x, y).

[Cutting Simulation: Second Invention] FIG.
The processing flow of the cutting simulation method is shown as an embodiment of the second invention. First, for each of the pre-cutting shape and the tool tip shape, a two-dimensional array having the minimum and maximum z coordinate values in each unit square area as elements is prepared. For the two-dimensional array H _L (i, j) and H _H (i, j) of the tool tip shape, the above-described processing 12 (FIG. 1) is performed.
Refer to) to create.

The two-dimensional arrays R _L (x, y) and R _H (x, y) of the shape before cutting are obtained from the initial shape of the work material in the case of the first step of cutting (roughing etc.). . That is, for each unit square area of each lattice, the lower limit value and the upper limit value (range) of the z coordinate value that the pre-cutting shape, which is the surface of the work material before cutting, can take, and the lower limit value and the upper limit value are configured. Two-dimensional arrays R _L (x, y) and R _{H as} elements
(X, y) is obtained. For the second and subsequent processes (finishing, etc.), perform a cutting simulation of the previous process,
The resulting two-dimensional array of post-cut shapes is used.

Then, in the process 21, the two-dimensional arrays H _L (i, j) and H _H (i, j) of the tool tip shape,
Two-dimensional array R _L (x, y) and R of the shape before cutting
_The post-cutting shape is calculated from _H (x, y) and the tool path p. The calculation of the post-cutting shape in the process 21 is performed as follows. First, the tool path p is superposed on the grid on the x and y planes, grid points on p, intersections of p and straight lines forming the grid,
And a point sequence Q = {Q ₁ ,
Q ₂ , Q ₃ , ...}.

FIG. 7 shows an example of the relationship between the tool path p and the point sequence Q. Now, when the tool center passes through each point of the point sequence Q, the two-dimensional array of the minimum and maximum z-coordinate values in each unit square area of the work material surface shape at each time point is set to W. Let _L (x, y) and _WH (x, y). When the tool center passes near the grid point A = (x _A , y _A ),
The points of the point sequence Q included in the range of x _A -1 <x <x _A +1 and y _A -1 <y <y _A +1 (areas shown by dots in FIG. 8) are Q _a and Q _{a + 1.} , Q _{a + 2} , ... Q _b ,
First, these points and two adjacent points, namely Q _a-1 ,
Q _a , Q _{a + 1} , ... Q _b , Q _{b + 1} combined (b−a +
3) _Find the minimum value z _qmin of the z coordinate among the points. For example, in the case of the grid point A in FIG. 8, z _qmin is the minimum value among the five white circles. At this time, the lower and upper limits of the shape of the work material after the tool center passes near the grid point A are as follows.

[0037]

(Equation 6)

In particular, when the tool center passes over the grid point A, in addition to the above processing, the upper limit of the shape of the work material is as follows. _{W H (x A + i,} y A + j): = min (W H (x A + i, y A + j), z + H H (i, j)) ··· (14) ^{However, i 2 + j 2 ≦ r} 2 , R is the tool radius. The initial values of W _L (x, y) and W _H (x, y) are respectively R
_{When L} (x, y) and R _H (x, y) are set and this processing is executed for all points in the grid point sequence of the tool path, finally W _L (x, y), W _H (x, y) is a two-dimensional array F _L of the cutting after the shape of obtaining (x, y), to match the F _H (x, y).

When the above processing is performed in the order along the tool path p, the cutting amount and the load applied to the tool are calculated from the change amounts of W _L (x, y) and W _H (x, y) at each point. You can ask. On the other hand, for the purpose of obtaining the final post-cutting shape, the point sequence q may be processed in any order. Two-dimensional array F _L of the cutting after the shape (x, y), F
_H (x, y) is a two-dimensional array S _L (x requested shape,
By comparing with y) and _SH (x, y), it can be used to check the uncut amount and the cut amount.
In this case, uncut amount or narrowing cutting amount of each unit square area, the lower limit _{value: D L (x, y)} = F L (x, y) -S H (x,
y) Upper limit value: D _H (x, y) = F _H (x, y) −S _L (x,
y) can be suppressed. Here, D _L (x, y) and D _H (x, y) represent the uncut amount when positive and the cut amount when negative.

Two-dimensional array F _L (x, y) of the shape after cutting,
F _H (x, y) is a two-dimensional array R of the shape before cutting in the next process
It can be used as _L (x, y) and R _H (x, y). If there is no change in the lattice spacing between steps, each two-dimensional array can be used as it is. When the lattice spacing is changed, the minimum z value _RL (x, y) of each unit square area in the subsequent process is checked for the corresponding position with the lattice in the previous process, and all the unit square regions with overlap are checked. Minimum z value F
It is obtained by calculating the minimum value of _L (x, y). Similarly for the maximum z value R _H (x, y) in the subsequent process, the maximum z value F _H (x, y) in the corresponding region in the previous process
Is calculated as the maximum value of. As a result, a correct simulation can be performed even if the lattice spacing is large during rough machining and the lattice spacing is small during finishing machining.

[Creation of Tool Path: Third Invention] FIG. 9 shows a processing flow of the method for creating a tool path as an embodiment of the third invention. In this embodiment, in process 31, a two-dimensional array U _L (i, j) of the tool upper shape is obtained. The array U _L (i, j) is created in this process 31 by the same method as the process 12 shown in FIG. In process 32, the two-dimensional array L _C (x, y) of the collision limit surface is calculated. This process 32
The array L _C (x, y) in Fig. 2 is created by the "pre-cutting shape R (x, y) and tool upper shape U (x, y)" shown in the conventional method.
From the sequence L _C (x, y) ”. However, in order to ensure that the pre-cut shape and the upper part of the tool do not collide at all points of the unit square area, the two-dimensional array R _H (x, y) of the upper limit z value is set as the upper part shape of the tool as the pre-cut shape. Two-dimensional array U _L (x, y) of minimum z values
Are used respectively. Therefore, the array L _C (x, y)
Is given by the following equation.

[0042]

(Equation 7)

The two-dimensional array R _H (x,
For y), if the cutting simulation is performed for the pre-cutting step, the result can be used. Tool path creation process 3 for calculating a tool path p for avoiding a collision
Regarding No. 3, it is the same as the conventional method. That is,
Cutting limit surface L _I (x, y) and collision limit surface L _C (x,
y) is compared for each grid point, and the upper point is taken to create the two-dimensional array L _H (x, y) of the composite limit surface. In the process 14 shown in FIG. 1, the array L _I (x,
A similar tool path p can be created by using the array L _H (x, y) instead of y).

[0044]

As is apparent from the above description, according to the present invention, in the first invention, a two-dimensional array having the maximum value of the z coordinate value in the unit square area of each lattice of the surface of the required shape as an element. Two-dimensional array H _{L having} S _H and the minimum z-coordinate value in the unit square area of each grid on the tool tip shape surface
Then, the cutting limit surface L _I is created, and the cutting path p of the tool is created from the created cutting limit surface L _I , and the required shape is obtained at all points in the unit square area of each grid. As a guarantee of avoiding shaving, it is possible to shorten the calculation time when creating the cutting path p of the tool by increasing the lattice spacing during rough machining without fear of shaving the required shape. .

In the second invention, the two-dimensional arrays H _L and H _H having the minimum and maximum z coordinate values in the unit square area of each grid on the surface of the tool tip shape, and each grid of the shape before cutting are used. Two-dimensional arrays R _L and R whose constituent elements are the lower limit value and the upper limit value that can be taken by the z coordinate value in the unit square area of
And _H, and a cutting path p of the tool, the two-dimensional array F _L and F _H to components lower limit and the upper limit value z-coordinate values can take on the unit square area of each grid of cutting after the shape is created And the grid spacing is increased during rough machining,
Even if the lattice spacing is reduced during finishing, a correct simulation can be performed during finishing.

That is, since the lower limit value and the upper limit value of the z coordinate value in the unit square area of each lattice at the time of rough machining are known, the z coordinate in the unit square area of each new lattice at the time of finishing machining is known. It is possible to know the lower limit value and the upper limit value that the value can take, and it becomes possible to perform a correct simulation during finishing. Further, in the second invention, the cutting shape is simulated as the upper limit value and the lower limit value of the post-cutting shape of the work material within the unit square area of each lattice, and the error range can be accurately obtained during the cutting simulation. Becomes

In the third invention, the two-dimensional array S _H having the maximum value of the z coordinate value in the unit square area of each grid on the surface of the required shape and the unit square area of each grid on the tool tip shape surface are used. While the cutting limit surface L _I is created from the two-dimensional array H _L having the minimum z-coordinate value as an element, the minimum z-coordinate value in the unit square area of each grid of the tool upper shape is set as an element. The collision limit plane L _C is created from the two-dimensional array U _L and the two-dimensional array R _H having the upper limit of the z-coordinate value in the unit square area of each grid of the precut shape as a constituent element. , The collision limit surface L _C and the cut-in limit surface L created
The cutting path p of the tool is created from _I and _I as a guarantee of avoiding cutting into the required shape at all points within the unit square area of each grid, and within the unit square area of each grid. In order to guarantee the avoidance of collision between the upper part of the tool and the work material, the calculation time for creating the cutting path p of the tool with a large grid interval during rough machining without fear of cutting the required shape Can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of processing of a tool path creating method as an embodiment of the present invention (first invention).

FIG. 2 is a diagram illustrating a relationship between a subscript of a two-dimensional array and a square area.

FIG. 3 is a diagram illustrating a cross scan line method.

FIG. 4 is a diagram illustrating a method of calculating a two-dimensional array of tool tip shapes.

FIG. 5 is a diagram illustrating a method of calculating a shaving limit surface using a maximum z value and a minimum z value.

FIG. 6 is a diagram showing a processing flow of a cutting simulation method as an embodiment of the present invention (second invention).

FIG. 7 is a diagram showing a relationship between a tool path p and a point sequence q.

FIG. 8 is a diagram for explaining points to be subjected to post-cutting shape calculation.

FIG. 9 is a diagram showing a flow of processing of the tool path creating method as an embodiment of the present invention (third invention).

FIG. 10 is a diagram illustrating a conventional method for calculating a shaving limit surface.

FIG. 11 is a diagram illustrating a conventional post-cutting shape calculation.

FIG. 12 is a diagram illustrating a tool upper shape.

[Explanation of symbols]

11 ... Two-dimensional array creation process of required shape, 12 ... Two-dimensional array creation process of tool tip shape, 13 ... Two-dimensional array creation process of cutting limit surface, 14 ... Tool path creation process, 2
1 ... Post-cutting shape calculation processing, 31 ... Creation processing of two-dimensional array of tool upper shape, 32 ... Creation processing of two-dimensional array of collision limit surface, 33 ... Creation of tool path for collision avoidance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G05B 19/4068

Claims (3)

[Claims] 1. A cutting path creating method for creating a cutting path of a tool when a required shape is cut using an NC machine tool, wherein az axis of an x, y, z coordinate system is taken as a rotary axis of the tool. , X, y
A first process in which a square grid is set on the coordinates, the maximum z coordinate value of the required shape surface is obtained for each unit square area of each grid, and a two-dimensional array S _H having this maximum value as an element is created. And the z of the tool tip shape surface for each unit square area of each grid.
A second processing step of obtaining a minimum coordinate value and creating a two-dimensional array H _L having this minimum value as an element; a two-dimensional array S _H created by the first processing step; From the two-dimensional array H _L created by the processing step, the lower limit z coordinate value of the tool tip center that allows the tool to pass without carving the required shape at all points in the unit square area of each grid, A third two-dimensional array L _I having this lower limit z coordinate value as an element is created as a shaving limit surface.
And the shaving limit surface L created by this third processing step.
_A method for creating a cutting path for a tool of an NC machine tool, characterized in that a cutting path p for a tool is created from _I. 2. A cutting simulation method for obtaining a post-cutting shape from a cutting path of a tool for cutting a required shape using an NC machine tool without actually cutting the cutting path, wherein x, y, z coordinates are provided. Taking the z axis of the system as the rotation axis of the tool, x, y
A square lattice is set on the coordinates, the minimum and maximum z coordinate values of the tool tip shape surface are obtained for each unit square area of each lattice, and the two-dimensional array H _L having these minimum and maximum values as elements And a first processing step of creating H _H , and a lower limit value and an upper limit value of a z-coordinate value that can be obtained by the pre-cutting shape that is the work material surface before cutting, which is obtained for each unit square area of each lattice. From the two-dimensional arrays R _L and R _H having the following elements, the cutting path p of the tool, and the two-dimensional arrays H _L and H _H created in the first processing step, obtains the lower limit and the upper limit of the z coordinate value is cutting after the shape is a workpiece surface can take after cutting for each area, two-dimensional array as a component of the lower limit and the upper limit F _L and F _H And a second processing step for producing the NC. Cutting simulation method of the work machine tool. 3. A cutting path creating method for creating a cutting path of a tool when a required shape is cut using an NC machine tool, wherein az axis of an x, y, z coordinate system is taken as a rotary axis of the tool. , X, y
A first process in which a square grid is set on the coordinates, the maximum z coordinate value of the required shape surface is obtained for each unit square area of each grid, and a two-dimensional array S _H having this maximum value as an element is created. And the z of the tool tip shape surface for each unit square area of each grid.
A second processing step of obtaining a minimum coordinate value and creating a two-dimensional array H _L having this minimum value as an element; a two-dimensional array S _H created by the first processing step; From the two-dimensional array H _L created by the processing step, the lower limit z coordinate value of the tool tip center that allows the tool to pass without carving the required shape at all points in the unit square area of each grid, A third two-dimensional array L _I having this lower limit z coordinate value as an element is created as a shaving limit surface.
Creating and processing steps, the determining the minimum value of the z coordinate values of the tool upper shapes are blade-free portion of the tool upper per unit square area of each grid, a two-dimensional array U _L to the minimum the elements of And a two-dimensional array having the upper limit of the z coordinate value that can be taken by the pre-cutting shape that is the surface of the work material before cutting, which is obtained for each unit square region of each grid, as a constituent element. From R _H and the two-dimensional array U _L created by the fourth processing step, the work material passes through the tool at all points within the unit square area of each grid without collision between the work material and the tool upper part. A lower limit z-coordinate value of the tool tip center that can be obtained, and a fifth processing step of creating a two-dimensional array L _C having the lower limit z-coordinate value as an element as a collision limit surface. The collision limit plane L _C created and the third processing step Carved limit surface L
_A method for creating a cutting path for a tool of an NC machine tool, characterized in that a cutting path p for a tool is created from _I and.