JP3030762B2 - Curved surface processing method by NC machine tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molds, aviation parts,
The present invention relates to a method of machining a curved surface such as an impeller with an NC machine tool, and more particularly to a technical field of machining the curved surface with a side edge of a tool instead of a tip of the tool.

[0002]

[Background of technology] As for mold products, high-mix low-volume production has progressed.
There is a situation where mold manufacturers are demanding shorter delivery times and higher precision.However, in conventional mold processing, since the tip of a ball end mill or the like is machined with a spherical tool, point contact is difficult. Since machining is continuous and work efficiency is low, and a mountain-shaped uncut portion is left between adjacent tool trajectories, a troublesome operation such as a manual removal by an expert is required. Therefore, if processing is performed along the shape on the side surface of the tool instead of on the tip of the tool, the processing efficiency is further improved, and almost no manual work is required, so that the shape accuracy can be expected to increase. In order to machine using the side surface of such a tool, the tool axis is controlled at an arbitrary position and angle by 5-axis control machining in which two axes of rotation are controlled in addition to orthogonal axes of X, Y, and Z axes. You need to develop a way to do it.

[0003]

2. Description of the Related Art With respect to the above-mentioned technology relating to 5-axis control machining,
There is an example in which a 5-axis NC machining center is cut using a ball end mill in the production of parts such as propellers for aircraft, although it is not a die processing. However, if the example of such aeronautical parts is applied to the object of the present invention as it is, the following problems occur.

(A) A CAD / CAM which can use the same CAD as that of the parent company or its graphic data must be purchased, and software for side edge machining adapted to the CAD / CAM of the subsidiary must be developed. On the other hand, the purchase of the CAD / CAM and the development of the dedicated software are very expensive in terms of cost, and greatly impose costs on affiliated companies, such as small and medium-sized enterprises, which have poor financial resources.

(B) The expression of the surface of the CAD of the parent company,
When the expression of the curved surface of CAD / CAM of the subsidiary is different, a complicated conversion process of developing or purchasing conversion software and matching the curved surface expression is required.

(C) The five-axis control machine tool has a table operating system in which the tool is fixed and the table operates, a tool operating system in which the table is fixed and the tool operates, and a rotating shaft. 2
There are three types of independent operation systems in which the axes operate on independent coordinate systems, and the conventional side edge machining software can be applied to only one of them, so that it can be applied only to a limited number of machine tools.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to perform side edge machining by the above-described five-axis control machining. In this case, (a) a commercially available personal computer can be used without using expensive CAD / CAM. (B) The ability to directly create the parent data of the subsidiary company without the need for conversion of the curved surface of the graphic data of the parent company without the need for conversion.
Readable by a personal computer, simplifying the process,
(C) The present invention is intended to be applicable to the case where the subsidiary machine tool is of a table operation type, a tool operation type, or an independent operation type, and to have versatility.

[0008]

When the solution of the present invention, in order to solve the problems will be described in accordance with FIG. 1 shown in the flowchart, first, the parent Society
NURBS necessary for performing side edge machining of tools owned by companies
Curves, B-spline surfaces and Be'zier surfaces
At least one of the surface data (parent data)
After importing, the parent data owned by the subsidiary, etc.
To a computer without the ability to create
Switch. The means is the N used in the parent data.
For any one of a URBS surface, a B-spline surface, and a Be'zier surface, the characteristics of the surface are captured,
Patch this.

The NURBS surface is expressed by the following expression.
expressed.P_{i, j}: Of control pointCoordinate position W_{i, j}: Control point P_{i, j}K: order in u direction 1: order in v direction N_{i, k}: B-spline basis function M in u direction_{j, l}: B-spline basis function in v direction u-direction B-spline basis function: N_{i, 1}(U) = 1x_i≦ u <x_{i + 1}  0 Other casesk-1: order x_i: Knot (x_i≤x_{i + 1}) N + 1: number of control points v-direction B-spline basis function: M_{j, 1}(V) = 1 y_j≦ v <y_{j + 1}  0 Other cases1-1: order yj: knot (y_j≤y_{j + 1}) M + 1: number of control points

[0010] This NURBS surface (see FIG. 2) expression
When focusing on the characteristics, the coordinate position of the control point and the
Various characteristics on the curved surface can be obtained by the weight and knot vector
Between the number and order of knot vectors and the number of control points
Is the relationship of (number of knot vectors = order + number of control points)
Because there isDegree and control point of read parent data
From the number, the coordinate position of the control point, the weight of the control point,
NURBS surface expression formula composed of knot vectors
Automatically selected,Necessary for determining the processing position etc. on the curved surface
The minimum amount of information is one unit and this is called patching
(See FIG. 3).

(B) The B-spline surface is represented by the following expression. P _{i, j} : coordinate position of control point k: order in u direction 1: order in v direction N _{i, k} : B-spline basis function in u direction M _{j, l} : B-spline basis function in v direction The B-spline basis function is equivalent to the NURBS surface.

When attention is paid to the characteristics of the B-spline surface expression, various characteristics on the surface are obtained by the coordinate position of the control point and the knot vector, and the number of knot vectors and the order and the number of control points are obtained. Has the relationship of (number of knot vectors = order + number of control points), so the parent data
From the order of the data and the number of control points, the coordinate position of the control point,
B-spline surface composed of knot vectors
The expression is automatically selected, and the minimum amount of information necessary for determining the processing position on the curved surface is patched.

(C) The Be'zier curved surface expression is shown as follows. P _{i, j:} coordinates B ⁿ _i of the control points (u): u direction of Bernstein basis functions B ^m _j (v): v direction of Bernstein basis function u direction Bernstein basis _{^{function: B n i (u) =}} ( ^{_{n i) u i (1-}} u) n-i (0 ≦ u ≦ 1) n: degree v direction Bernstein basis ^{_{functions: B m j (v) =}} (m j) v j (1-v) m-j (0 ≦ v ≦ 1) m: order

In the case of the Be'zier surface expression,
Since various characteristics on the curved surface can be obtained only by the coordinate position of the control point, the number of control points and the value of the control point which the read parent data has
From Be'z which consists only of the coordinate position of the control point
The ier curved surface expression is automatically selected, and the minimum amount of information necessary for determining the processing position on the curved surface is patched.

By making it possible to process the above three types of curved surfaces, most of the parent data can be handled, so that the present invention eliminates the need for software conversion. By converting a huge amount of parent data into a patch and reading the minimum amount of information required to determine a processing position on a curved surface, etc. Become. Of course, the present invention can be applied to a computer having a memory capacity larger than that of a personal computer.

Next, parameter values in the u-direction and the v-direction corresponding to the processing position of the curved surface are set on the curved surface. Here, the parameter values refer to the values of u and v of the B-spine line basis function. In the case of a NURBS surface as shown in FIG. 2, an arbitrary point is determined by the value, and the processing described later is performed at the arbitrary point. The coordinate position and vector calculation will be performed. Therefore, the parameter value is set so that the curved surface processing can be performed with appropriate accuracy when the processing coordinate position and vector are calculated at that position.
The setting method is arbitrary. For example, t = 0, 0.1, 0.2, 0.3,.
A parameter value can be set by defining an increment value (a value of 0.1) such as 1.0. Here, the increment value is
The difference between the parameter value at a certain point and the parameter value at the next point. Whether or not this parameter value setting is appropriate is determined in a tolerance check process described later, and if it is too coarse and inappropriate, the setting is performed again. By setting this parameter value,
The processing position of the curved surface can be set arbitrarily.

In the above-mentioned parameter setting values, first, a normal vector is obtained, and then the coordinate position of the tool axis and the tangent vector are calculated in consideration of the tool radius and the uncut amount.

Then, NC data is calculated from the position coordinates of the tool axis and the tangent vector in consideration of the specifications of each machine tool. Here, the NC data refers to all data of a tool, a table, and the like necessary for machining a curved surface with an NC machine tool, and specifically refers to a position of a tool, a tilt angle of a tool shaft, a rotation speed, a feed speed, and the like. . In the calculation of the data, the NC data applicable to the following three operation modes is calculated. In other words, there are two types of operating methods of the rotary axis of a machine tool such as a machining center: a case where the table moves on both axes, a case where the tool side moves on both axes, and a case where both axes move on independent coordinate systems . If the work
Measure the rotation angle of the rotation axis of the table on which
And then calculate the rotation angle of the remaining rotation axis.
Measure the rotation angle of the rotating shaft on which the tool is mounted.
And then calculate the rotation angle of the remaining rotation axis.
To determine the rotation angle of the rotation axis from any one
Become. Because the table on which the work is mounted
Of the rotating shaft or the table on which the tool is mounted
The direction of the rotation vector of the axis is the rotation of the rotation axis of the other table.
Because it changes by rolling, so as not to be affected by it,
In the case of
First find the rotation angle of the rotation axis at the point position.
The rotation angle of the rotation axis at the home position where the tool is attached
Is calculated first, and then the rotation angle of the remaining rotation axis is calculated.
It is. Therefore, since the calculation can be performed by the above three operation methods, the NC data can be calculated by properly using three types of calculation methods according to the specifications of the machine tool.
By controlling the rotation axis, for example, cutting by a side blade of a ball end mill can be performed.

When the calculation of the NC data is completed, the distance between the product shape data and the tool path is calculated, and a tolerance check is performed to determine whether or not the value is within an allowable range. If the value exceeds the allowable value, the increment value is divided for the set parameter value, and the process returns to the parameter setting stage. At this time, 1 /
If the increment division value is set in advance, such as 2, 1/3, etc., the process from setting the above parameters, calculating the tool axis and vector, calculating the NC data, and checking the tolerance is a parameter. The division is automatically repeated until the data value becomes appropriate.

In the above tolerance check, the conventional linear approximation method is not performed, and the present invention directly determines the distance between the shape data of the product and the tool trajectory, and determines whether the distance is within a predetermined set value. Determine whether or not. That is, the conventional tolerance check adopts a method of approximating the shape data of a product to a virtual straight line and finding the distance between the straight line and the tool path (see FIG. 5). However, there is a disadvantage that the accuracy is insufficient. Therefore, the present invention has made it possible to capture a curved surface in a fixed unit by performing the patching of the curved surface, and to perform the calculation. Therefore, even the shape data of the secondary and cubic curved surfaces can be obtained.
The distance between the tool and the tool trajectory was determined directly (see FIG. 4). As a result, a dramatic improvement in accuracy was achieved.

If the tolerance check is satisfied, the coordinate position of the tool, the inclination angle of the tool axis, the number of revolutions, the feed speed, etc.
Create parent data of subsidiaries etc. as C data
Write to a computer without the ability .

When the parameter value of the surface reaches the end point, the NC data of one patch is created.
By returning to the original curved surface patching process and repeating the same process again, NC data for finally performing the entire curved surface processing is created. Based on the data, a machine tool such as a machining center is operated to cut or grind a curved surface of a mold or the like.

[0023]

[Embodiment 1] When the parent data is cubic and the number of control points is 4, using the NURBS surface expression, the coordinates of the control points
The position , the weight of the control point, and the knot vector were input as follows. u direction knot vector = (− 3, −2, −1,0,1,1)
2,3,4) v-direction knot vector = (− 3, −2, −1,0,1,
2,3,4)

Next, parameter values were set, and the parameters in the u direction = 0.1 and the parameters in the v direction = 0.0.

Next, a tool axis and a vector are calculated. Tool tip coordinates = (-15.76736,48.05774, -41.85425) u-direction tangent vector = (0.76318, -0.57477, -0.29525) v-direction tangent vector = (-0.35685, 0.14735, -0.92246) The normal vector = (-0.57578, -0.81229, 0.09298).

Further, the calculation of NC data was carried out, and it was found that X = -0.395 mm Y = -272.884 mm Z = -679.670 mm A = -8.473 deg B = 201.148 deg F = 304.929 mm / min.

A tolerance check was performed, and the tolerance passed the tolerance check with a set value of 0.003 mm and an error of 0.000043 mm.

The NC data is written, a 5-axis machining center is operated, and a curved surface of a mold is cut.
A curved surface with excellent shape accuracy was obtained.

[0029]

Embodiment 2 Using a B-spline surface, if the parent data is 3
Next, when the number of control points is 4, the coordinate position of the control point
And knot vectors were input as follows. u direction knot vector = (− 3, −2, −1,0,1,1)
2,3,4) v-direction knot vector = (− 3, −2, −1,0,1,
2,3,4)

Next, parameter values were set, and the parameter in the u direction was set to 0.1 and the parameter in the v direction was set to 0.0.

Next, the tool axis and vector are calculated, and the tool tip coordinates = (-14.23038, 46.90280, -42.46132) u-direction tangent vector = (0.76147, -0.57091, -0.30694) v-direction tangent vector = (-0.36942, 0.15305, -0.91656) The normal vector = (-0.57244, -0.81445, 0.09472).

Further, the calculation of the NC data was carried out, and X = -2.674 mm Y = -274.460 mm Z = -678.704 mm A = -8.803 deg B = 201.952 deg F = 302.596 mm / min

A tolerance check was performed, and the tolerance was passed with a set value of 0.003 mm and an error of 0.000044 mm.

The NC data is written, and a 5-axis machining center is operated to perform a curved surface cutting of a mold.
A curved surface with excellent shape accuracy was obtained.

[0035]

Embodiment 3 Using a Be'zier surface expression, a parent data
When the data is tertiary, the coordinate position of the control point is input as follows. P _0,0 = (-31.77782,50.46471, -102.75177) P _1,0 = (-30.89381,49.72947, -102.94402) P _2,0 = (-29.97342,48.99528, -103.12974) P _3,0 = (-29.01616 , 48.26717, -103.28368) P _0,1 = (-31.77782,50.46471, -102.75177) P _1,1 = (-30.89381,49.72947, -102.94402) P _2,1 = (-29.97342,48.99528, -103.12974) P _{3 , 1} = (-29.01616,48.20717, -103.28368) P _0,2 = (2.68199,34.76349, -37.23965) P _1,2 = (3.82687,33.13141, -38.31958) P _2,2 = (4.777308,31.51519, -39.43960 ) P _3,2 = (5.54964,29.89190, -40.66449) P _0,3 = (2.68199,34.76349, -37.23965) P _1,3 = (3.82687,33.13141, -38,31958) P _2,3 = (4.77305, 31.51519, -39.43960) P _3,3 = (5.54964, 29.86190, -40.66449)

Next, parameter values were set, and the parameter in the u direction was set to 0.1 and the parameter in the v direction was set to 0.0.

Next, the tool axis and vector are calculated, and the tool tip coordinates = (-0.95379,34.27499, -50.16925) u-direction tangent vector = (0.43145, -0.74542, -0.50811) v-direction tangent vector = (-0.46565, 0.23586, -0.85295) The normal vector = (-0.75687, -0.6559, 0.24574).

Further, the calculation of NC data was carried out, and it was found that X = -23.202 mm Y = -293.831 mm Z = -665.242 mm A = -13.642 deg B = 208.631 deg F = 427.558 mm / min.

A tolerance check was performed, and the tolerance was passed with a set value of 0.003 mm and an error of 0.000119 mm.

The NC data is written and a 5-axis machining center is operated to perform a curved surface cutting of a mold.
A curved surface with excellent shape accuracy was obtained.

[0041]

The present invention according to the above configuration has the following effects. (A) Since it is possible to perform side edge machining on a curved surface of a mold by 5-axis control, automation is possible, and manual work is almost eliminated, so that shape accuracy is improved. Excellent curved surface processing for aviation parts, propellers, etc. (B) since the also can be read in the personal computer to patch the parent data, parent regardless of the conventional expensive CAD / CAM
A commercially available personal computer having no data creation capability can be used, and the cost can be reduced. (C) Even if there is a difference in the curved surface expression from the parent data, N
Since three expressions such as a URBS curved surface expression can be used, in most cases, it is not necessary to convert the parent data by software, and the process can be simplified. (D) Since it can cope with the difference in the operation system of the machine tool, it can be used for general purposes.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the means of the present invention.

FIG. 2 is a schematic diagram illustrating a NURBS curved surface.

FIG. 3 is a schematic diagram illustrating patching of a curved surface according to the present invention.

FIG. 4 is a schematic view showing a tolerance checking method according to the present invention.

FIG. 5 is a schematic diagram showing a conventional tolerance check method.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05B 19 / 418,19 / 4097

Claims (2)

(57) [Claims] (1) A side edge machining is performed by a computer of a parent company or the like having a capability of expressing a curved surface shape as at least one of a NURBS curved surface, a B-spline curved surface, and a Be'zier curved surface. Create surface data (parent data) representing the surface shape of the object to be processed in a curved surface expression, and (2) read the parent data into a computer having no ability to generate parent data of a subsidiary or the like, and (α) When the parent data is composed of the coordinate position of the control point, the weight of the control point, and the knot vector, (a) N in the following surface expression formulas (a) to (c)
URBS surface expression is automatically selected. (Β) When the parent data is composed of the coordinate position of the control point and the knot vector,
(B) A B-spline surface expression is automatically selected from the surface expression of (c). (Γ) When the parent data is composed only of the coordinate positions of the control points, (C) Be'zier surface expression is automatically selected from the surface expressions (a) to (c), and (a) NURBS surface expression nm nm ΣNi, k (u) Mj, l (v) Wi, jPi, ji = 0 j = 0 S (u, v) = nm Σ {Ni, k (u) Mj, l (v) Wi, ji = 0 j = 0 Pi, j: coordinate position of control point Wi, j: weight of control point Pi, j k: order in u direction l: order in v direction Ni, k: B-spline basis function in u direction Mj, l: B-spline basis function in v direction u direction B-spline basis function: Ni, 1 (u) = 1 xi≤u <xi + 1 0 In other cases (u-xi) Ni, k-1 (u) (xi + k-u) Ni + 1, k -1 (u) Ni, k = + xi + k-1-xi xi + k-xi + 1 k-1: order xi: (Xi ≦ xi + 1) n + 1: number of control points v-direction B-spline basis function: Mj, 1 (v) = 1 yj ≦ v <yj + 1 0 otherwise (v−yj) Mj, l -1 (v) (yj + l-v) Mj + 1, l-1 (v) Mj, l = + yj + l-1-yjyj + l-yl + 1 1-1: order yj: knot ( yj ≦ yj + 1) m + 1: number of control points (b) B-spline surface expression nm S (u, v) = ΣΣNi, k (u) Mj, l (v) Pi, ji = 0 j = 0 Pi, j: coordinate position of control point k: order in u direction l: order in v direction Ni, k: B-spline basis function in u direction Mj, l: B-spline basis function in v direction (c) Be'zier surface expression nm S (u, v) = ΣΣBni (u) Bmj (v) Pi, ji = 0 j = 0 Pi, j: coordinate position of control point Bni (u): Bernstein basis function in u direction Bmj (v): Bernstein basis function in the v-direction Bernstein in the u-direction in basis function: Bni (u) = (ni) ui (1-u) ni (0 ≦ u ≦ 1) n! (Ni) = (ni)! i! n: degree v-direction Bernstein basis function: Bmj (v) = (mj) vj (1-v) mj (0 ≦ v ≦ 1) m! (Mj) = (m−j)! j! m: Degree Determines one patch required for determining a machining position of a curved surface according to the selected curved surface expression, and (3) calculates the individual machining positions and vectors of the curved surface. Setting the parameter values of u and v in (c), (4) calculating the tool coordinate position and the inclination vector at the above parameter values in consideration of the tool radius and the uncut amount, (5) Based on the tool coordinate position and the inclination vector, NC data including the position of the tool, the inclination angle of the tool axis, the number of revolutions, the feed speed, and the like are calculated, and (6) the product shape data and the tool path are calculated. A tolerance check is performed to determine whether or not the distance is within the allowable range. If the distance is not within the allowable range, the parameter value is reset, (7) the NC data is written, and (8) the parameter is written. Whether the data value has completed one patch After one patch has been determined, if one patch has not been completed, reset the parameter values.If completed, proceed to the next patch process, and machine the workpiece with the side edge of the tool. 5
A curved surface machining method using an axis-controlled NC machine tool. 2. In the calculation of NC data, when the table is operated with two operating axes of the rotary axis of the machine tool, first calculate the rotation angle of the rotary axis of the table on which the work is mounted. If the tool side moves on both axes, the rotation angle of the remaining rotation axis is determined, and then the rotation angle of the remaining rotation axis is determined. When moving in independent coordinate systems, three types are set in advance by a method of obtaining a rotation angle from an arbitrary one, and NC is set according to each calculation method.
The method of claim 5, wherein the data is calculated by a five-axis control NC machine tool.