JP4392533B2 - Numerically controlled curved surface processing equipment - Google Patents

Description

  The present invention relates to a numerically controlled curved surface machining apparatus, and more particularly to a numerically controlled curved surface machining apparatus that improves machining surface roughness and machining surface accuracy and enables high-speed machining.

  Conventional numerically controlled NC curved surface machining is performed with polygonal line approximation, and the machining surface roughness is poor, requiring a large number of manual finishing steps. Further, as shown in FIG. 10 (b), the acceleration / deceleration at the time of positioning decreases the average feed speed, the processing time is long, and a large amount of NC data at a fine pitch is required to increase the processing surface accuracy. Was necessary.

  Thereafter, various curved surface machining methods using NC machine tools were proposed for the purpose of improving machining surface accuracy and reducing the amount of NC data. However, even in these conventional methods, the problems of the decrease in the machined surface roughness due to the broken line approximation and the decrease in the average feed rate due to acceleration / deceleration during positioning still remain.

  The present applicant has proposed a method of reading CL data from a host CAM system and creating NURBS curve NC data of a tool movement locus (see, for example, Patent Document 1). In another application, a method has been proposed in which the amount of change in the feed rate is treated as a curve when the NURBS curve NC data is created. In another application, a method of cutting a material with high accuracy and high efficiency from two tool paths is proposed.

JP 2001-92516 A (Pages 5 to 9, FIGS. 1 to 17)

  A method of deriving the format of the NURBS interpolation command and the control point vector, weight, knot value to be given thereto, and controlling the numerically controlled curved surface processing apparatus, and deriving the optimum value of the feed speed given to the NURBS interpolation command, and NC data In the method of converting to, two NURBS curves are interpolated in consideration of a break in the behavior of the tool tip.

  However, there is no analysis of whether the breakage of the tool tip is caused by an operation on the orthogonal coordinate axis of NC data or an operation on the rotary coordinate axis, and there is no means for smoothly changing the two NURBS curves.

  If the angle created by the conventional method is sent directly to the control device of the processing machine and processed by the processing machine, each axis suddenly rotates at a high speed or the tool moves to an unexpected position, resulting in tool breakage. , Processing machine breakage, cutting, and uncut material.

  An object of the present invention is to provide a means for smoothing an angle change by eliminating a sudden angle change of a rotation axis when creating NC data by NURBS interpolation based on a tool movement locus of CL data generated by a host CAM system. A numerically controlled curved surface processing apparatus is provided.

In order to achieve the above object, the present invention is a simultaneous multi-axis that is numerically controlled by an NC apparatus having a numerically controlled NURBS interpolation function and having three linear axes orthogonal to each other and two rotary axes that control the tool spindle direction. in numerically controlled curved surface machining unit including the control NC machine, the CL data consisting of the tool tip position vector data and tool spindle direction vector curved shape is calculated machining path direction in a defined work coordinate system in the host computer, Component conversion matrix and angle for converting into a standard coordinate system component for operating the NC processing machine based on the processing machine configuration including the first rotation axis, the second rotation axis, the tool axis and the master axis of the simultaneous multi-axis control NC processing machine Addition value creating means is provided. Further, the component conversion matrix / angle addition value creating means is based on component conversion means for converting the tool spindle direction vector from a workpiece coordinate system to a standard coordinate system, and the tool spindle direction vector of the converted standard coordinate system. A second angle creating means for creating a second angle that is a rotation angle around the second rotation axis of the tool spindle direction vector in the standard coordinate system, and a plurality of the machining path directions by the second angle creating means. Second angle correction means for creating a continuous angle distribution from the distribution of second angles created for control points, and the tool rotated by a second angle around a second rotation axis created by the second angle correction means Based on the spindle direction vector, a first angle creating means for creating a first angle that is a rotation angle around the first rotation axis of the tool spindle direction vector, and the machining by the first angle creating means First angle correction means for creating a continuous angle distribution from the distribution of the first angle created for a plurality of control points in the road direction, and the second angle and the first angle created by the second angle correction means Using the first angle created by the correcting means, the machine coordinate transformation matrix creating means for obtaining a matrix for converting the tool tip position vector in the workpiece coordinate system into the machine coordinate system, and using the obtained machine coordinate transformation matrix It has a machine coordinate conversion means for converting the tool tip position vector into the machine coordinate system, and a means for converting the converted machine coordinate system data into NC data. Further, the second angle correction means has both components of the second rotation axis direction and the tool axis direction of the tool spindle direction vector used for obtaining the second angle created by the second angle creation means are zero. When an identifier is set by detecting the state to be obtained, the difference value of the second angle between all adjacent control points is obtained, and when the second angle cannot be obtained by the identifier, the relevant point When another difference value is created using the difference value of the control point adjacent to the control point, and the magnitude of the created other difference value is π or more, the difference value, the difference value + π, the difference value− The smallest value is detected from among π, the difference value + 2π, and the difference value −2π to obtain a new difference value, and the difference value is added to the second angle of the adjacent control point to obtain the second angle of the control point. The first angle correction means calculates the first angle difference between all adjacent control points. A value is obtained, and when the magnitude of the difference value is greater than or equal to π, the smallest difference value is detected from the difference value, the difference value + 2π, and the difference value −2π to obtain a new difference value, and the control A difference value is added to the first angle of the adjacent control point of the point to obtain the first angle of the control point.

  The present invention also reads the tool tip position vector data calculated in the machining direction in the workpiece coordinate system whose curved surface shape is defined by the host computer, the tool spindle direction vector, and the feed speed in the workpiece coordinate system as CL data. In order to operate the NC machine based on the machine configuration of the simultaneous multi-axis control NC machine, the machine coordinate system converts the linear 3-axis position vector, rotation angle, and feed speed into the machine coordinate system. Modify or add the NURBS curve so that the rotation angle continuously changes at the connection points of a plurality of NC data interpolated by the NURBS curve with the rotation angle, and create at least one NURBS curve with continuous curvature, The knot vector of the optimal spacing of the NURBS curve based on the position vector of the three straight axes calculated in the machine coordinate system and the rotation angle The NURBS curve of the three axes of the machine coordinate system and the rotation axis is calculated using the knot vector, the NURBS curve is converted into NC data for NURBS interpolation, and the machining speed of the workpiece coordinate system is converted into the machine coordinate system. We propose a numerically controlled curved surface processing device that converts the data of the machine coordinate system into NC data by converting it into the processing speed.

  According to the present invention, not only the optimum actual machining speed and abrupt behavior change at the tool tip in the tool movement trajectory that draws a free curve, but also abrupt behavior change on the orthogonal coordinates and rotating coordinates in the machine coordinate system is mitigated. As a result, it is possible to extend the cutting tool life, avoid a sudden load change of the servo mechanism, reduce the burden on the numerically controlled curved surface processing device, improve the surface roughness, and perform curved surface processing with good surface accuracy. become. As a result, it is possible to greatly reduce the man-hours for manual finishing work in the post-process.

  Next, an embodiment of a numerically controlled curved surface processing apparatus according to the present invention will be described with reference to FIGS.

  FIG. 10 is a diagram showing a comparison between the linear interpolation processing method and the NURBS interpolation processing method.

  In numerically controlled NC curved surface machining, as shown in FIG. 10 (a), machining is performed with polygonal line approximation, the machining surface roughness is poor, and a large number of manual finishing steps are required. Further, as shown in FIG. 10 (b), the acceleration / deceleration at the time of positioning decreases the average feed speed, the processing time is long, and a large amount of NC data at a fine pitch is required to increase the processing surface accuracy. Was necessary.

  Thereafter, various curved surface machining methods using NC machine tools were proposed for the purpose of improving machining surface accuracy and reducing the amount of NC data. However, even in these conventional methods, the problems of the decrease in the machined surface roughness due to the broken line approximation and the decrease in the average feed rate due to acceleration / deceleration during positioning still remain.

  FIG. 11 is a diagram illustrating a relationship between a NURBS curve and control points.

  In order to solve these problems, an interpolation method using a NURBS curve shown in FIG. 11, that is, an irregularly spaced rationalized B-spline curve has been proposed. The NURBS curve is a type of B-spline curve, and is a curve expressed using a rational expression in which the intervals between nodes constituting the curve are not uniform. Other curves use polynomials to define curves, whereas NURBS curves are characterized by using rational expressions.

  By controlling these rational expressions, the curve can be easily deformed locally. In addition, it is possible to uniformly handle cylinders, cones, spheres, hyperbolas, ellipses, and parabolas that cannot be accurately expressed with other curves.

  In FIG. 11, the NURBS curve is defined by a control point Pi, a weight wi, and a knot vector xi. Here, k is a rank, Pi is a control point, wi is a weight, xi is a knot (xi ≦ xi + 1), [x0, x1,..., Xm] (m = n + k) is a knot vector, and t is a spline parameter. To do.

  When the spline basis function N (t) is expressed by a de Boor-Cox recursive formula, the formulas (1) and (2) are obtained. The NURBS curve P (t) to be interpolated is as shown in Equation (3).

ＮＵＲＢＳ補間指令は、以下のようなフォーマット
Ｇ０５Ｐ１００００；(高精度輪郭制御モードＯＮ)
…
Ｇ０６.２
[Ｐ＿]Ｋ＿Ｘ＿Ｙ＿Ｚ＿α＿β＿[Ｒ＿][Ｆ＿]；
Ｋ＿Ｘ＿Ｙ＿Ｚ＿α＿β＿[Ｒ＿]；
Ｋ＿Ｘ＿Ｙ＿Ｚ＿α＿β＿[Ｒ＿]；
Ｋ＿Ｘ＿Ｙ＿Ｚ＿α＿β＿[Ｒ＿]；
…
Ｋ＿Ｘ＿Ｙ＿Ｚ＿α＿β＿[Ｒ＿]；
Ｋ＿；
…
Ｋ＿；
Ｇ０１…
…
Ｇ０５Ｐ０；(高精度輪郭制御モードＯＦＦ)
で出力される。それぞれのコードは、
Ｇ０６.２：ＮＵＲＢＳ補間モードＯＮ
Ｐ：ＮＵＲＢＳ曲線の階数
Ｋ＿Ｘ＿Ｙ＿Ｚ＿α＿β＿：制御点
(α，β：回転軸指令)
Ｒ：ウエイト
Ｋ：ノット
Ｆ：速度
という意味を持つ。

NURBS interpolation command has the following format G05P10000; (High-precision contour control mode ON)
...
G06.2
[P_] K_X_Y_Z_α_β_ [R _] [F_];
K_X_Y_Z_α_β_ [R_];
K_X_Y_Z_α_β_ [R_];
K_X_Y_Z_α_β_ [R_];
...
K_X_Y_Z_α_β_ [R_];
K_;
...
K_;
G01 ...
...
G05P0; (High-precision contour control mode OFF)
Is output. Each code is
G06.2: NURBS interpolation mode ON
P: NURBS curve rank K_X_Y_Z_α_β_: control point
(α, β: rotation axis command)
R: Weight K: Knot F: Means speed.

  In the NURBS interpolation process, as shown in FIG. 10C, the curve can be processed smoothly, so that the number of manual finishing steps is small. Further, as shown in FIG. 10 (d), acceleration / deceleration at the time of positioning becomes smooth and the average feed speed increases, so that the machining time can be shortened and high-speed machining is possible. Furthermore, since the control point of NURBS interpolation can be set efficiently, it is said that there is an advantage that NC data is reduced.

  The present applicant has proposed a method of reading CL data from a host CAM system and creating NURBS curve NC data of a tool movement locus (see, for example, Patent Document 1). In another application, a method has been proposed in which the amount of change in the feed rate is treated as a curve when the NURBS curve NC data is created. In another application, a method of cutting a material with high accuracy and high efficiency from two tool paths is proposed.

  The NC post processor device corresponding to the conventional simultaneous multi-axis control NC machine has CL data consisting of a tool tip position vector and a tool spindle direction vector calculated in the machining path direction in the workpiece coordinate system defined by the CAM system, The processing machine configuration of the simultaneous multi-axis control NC machine is read and converted into linear three-axis coordinates and a rotation angle in the machine coordinate system in order to operate the NC machine.

This conversion is generally
Step 1: Read CL data consisting of a tool length, a tool tip position vector, and a tool spindle direction vector, and a processing machine configuration consisting of a first rotation axis, a second rotation axis, a tool axis, and a master axis of the processing machine. Convert tool spindle direction vector to rotation angle according to the machine configuration Step 3: Convert the tool tip position vector into the three linear axes of the machine according to the tool length and tool spindle direction vector Is executed.

Regarding rotation angle conversion in step 2, typical machine configuration 5 patterns of 5-axis control NC machine, which is a kind of simultaneous multi-axis control NC machine
(1) Basic 3 axes = X, Y, Z axis Rotary axis 2 axes = A, C axis Tool axis = Z axis
(2) Basic 3 axis = X, Y, Z axis Rotation axis 2 axis = B, C axis Tool axis = Z axis
(3) Basic 3 axis = X, Y, Z axis Rotary axis 2 axis = A, B axis Tool axis = X axis
(4) 3 basic axes = X, Y, Z axes 2 rotary axes = A, B axes
(B axis is the master axis)
Tool axis = Z axis
(5) 3 basic axes = X, Y, Z axes 2 rotary axes = A, B axes
(A axis is the master axis)
A tool axis = Z axis and an angle conversion method from a direction vector to an angle are disclosed (for example, see JP-A-7-334223 (pages 3 to 5, FIGS. 3 to 11)). In the patterns (1) to (5), the tool spindle direction vector is represented by (I, J, K) as follows.

また、ステップ１で入力する工具主軸方向ベクトルは、数式９のように、各成分の２乗和が１または一定となるよう設定されている。ここで、一定値が工具長の２乗になるよう設定されていれば、ステップ１で工具長を入力する必要は無い。換言すれば、数式９は、半径が１または一定の球面上の点を表している。

Further, the tool spindle direction vector input in step 1 is set so that the sum of squares of each component is 1 or constant as shown in Equation 9. Here, if the constant value is set to be the square of the tool length, it is not necessary to input the tool length in step 1. In other words, Formula 9 represents a point on a spherical surface having a radius of 1 or a constant.

前記ＮＵＲＢＳ補間指令のフォーマットおよびそこに与えるべき制御点ベクトル，ウエイト，ノット値を導出し、数値制御曲面加工装置を制御する方法と、ＮＵＲＢＳ補間指令に与える送り速度の最適値を導出し、ＮＣデータに変換する方法とにおいては、工具先端の挙動の折れを考慮し、２つのＮＵＲＢＳ曲線を補間している。

A method of deriving the format of the NURBS interpolation command and the control point vector, weight, knot value to be given thereto, and controlling the numerically controlled curved surface processing apparatus, and deriving the optimum value of the feed speed given to the NURBS interpolation command, and NC data In the method of converting to, two NURBS curves are interpolated in consideration of a break in the behavior of the tool tip.

  However, there is no analysis of whether the breakage of the tool tip is caused by an operation on the orthogonal coordinate axis of NC data or an operation on the rotary coordinate axis, and there is no means for smoothly changing the two NURBS curves.

  FIG. 12 is a diagram showing the relationship between the connecting parts of two NURBS curves.

  In general, the continuity between curves is calculated and evaluated from control point information at a connected portion of a NURBS curve, as shown in FIG. Two NURBS curves to be evaluated for continuity are a curve (CV1) 41 and a curve (CV2) 42.

  The control point information of this NURBS curve CV1 consists of CP1 (1) to CP1 (n) 43, and the control point information of CV2 consists of CP2 (1) to CP2 (m) 44. As for the continuity between the NURBS curves CV1 and CV2, if the final control point CP1 (n) of the NURBS curve CV1 and the first control point CP2 (1) of the NURBS curve have the same coordinates, there is no break between the curves. To be judged.

  When this condition is satisfied, if CP1 (n) and CP2 (1) are on the straight line created by CP1 (n-1) and CP2 (2), it can be determined that the continuity of the tangent is satisfied. .

  A point (EXP1) 45 on a straight line defined by CP1 (n-2) and CP1 (n-1), and a point (EXP2) 46 on a straight line defined by CP2 (2) and CP2 (3) If the point (EXP1) 45 and the point (EXP2) 46 satisfy the relationship of Equation 10, the continuity of curvature is maintained.

図１３は、数式１０等を機械座標系におけるＸＹＺの直行座標上の動作にだけ適応し、送り速度の連続性だけを考慮して導出された機械座標系回転軸の挙動を示す図である。

FIG. 13 is a diagram illustrating the behavior of the rotation axis of the machine coordinate system derived by considering only the continuity of the feed rate by applying Formula 10 and the like only to the operation on the XYZ orthogonal coordinates in the machine coordinate system.

  The trajectory 51 is an actual machining trajectory derived from the NURBS command derived in consideration of only the continuity of the orthogonal coordinate system and the feed rate. The break 52 is a break of a NURBS curve segment. The behavior 53 is the behavior of the tool on the actual machining locus 51. The distribution 54 is a feed rate distribution corresponding to the actual tool path 51. A distribution 55 is a distribution of the A-axis motion corresponding to the actual tool path 51. A distribution 56 is a distribution of the B-axis motion corresponding to the actual tool path 51.

  In this example, the tool is controlled with the reversing operation of the rotating shaft with respect to the workpiece at the cut 52.

  FIG. 14 is a diagram illustrating cutting at a position where the rotation angle changes rapidly.

  In the NC data according to the NURBS interpolation command, when the rotation axis is suddenly reversed, the stop accuracy at the specified angle is deteriorated due to a sudden load change of the servo mechanism. As shown in FIG. 14, in the machine coordinate system 61, even if the tool path is linear, when the rotation axis has a sudden reversal operation such as the distribution 55 or 56 in FIG. 13, The tool tip will move like a locus 62.

  As a result, the tool tip point 64 in the target tool posture 63 at the reversal position of the rotating shaft actually becomes a tool posture 65 and its tool tip point 66 due to a sudden change in the load of the servo mechanism, and the workpiece is cut. This leads to excessive machining on the numerically controlled curved surface processing equipment, cutting into the surface, worsening of the machined surface roughness, shortening of the cutting tool life.

  When an angle conversion method using any one of Equations 4 to 8 is implemented in a computer, the built-in function restriction provided by the computer language C ++, etc., and the numerator or denominator component 2 of Equations 4 to 8 are provided. Discontinuous angles may be created by the positive square root of the sum of products.

For example, when C ++ is used as the computer language and the atan2 function is used to obtain the arc tangent, the following restrictions apply:
(A) 0/0 arctangent is 0
(B) The answer ranges from -π radians to π radians
(C) The quadrant is determined by the sign of the numerator and denominator.

  FIG. 15 is a diagram illustrating a problem caused by 0/0 on the computer implementation.

  Due to the limitation of (A), for example, when a tool path that passes the Z-coordinate maximum position 1501 of the sphere shown in FIG. 15A and uses the normal vector of the sphere as the tool principal direction vector is input, a position 1502 shown in FIG. Both of the vector components for obtaining the angle at 0 become 0, the angle is calculated as 0, and a sharp point 1503 shown in FIG. 15C is created, resulting in a defective angle distribution 1504. Originally, a good angle distribution 1505 is a desirable result.

  FIG. 16 is a diagram illustrating a problem caused by the domain limitation of the solution on the computer implementation from −π radians to π radians.

  When the tool path 1601 for cutting a sphere in a spiral shape is input with the normal vector of the sphere shown in FIG. 16a as a tool principal axis direction vector, for example, as shown in FIG. Despite the fact that 1602 changes continuously, a failure angle distribution 1604 that changes in a sawtooth shape between −π and π as shown in FIG. 16C is created, resulting in a failure angle distribution 1604. Originally, the good angle distribution 1605 is a desirable result.

  FIG. 17 is a diagram illustrating a problem caused by vector component inversion.

  When the tool path 1701 for cutting the sphere so as to pass the maximum position in the Z coordinate of the sphere is input with the normal vector of the sphere shown in FIG. As shown in FIG. 17, the tool spindle direction vectors 1702 and 1703 sandwiching the Z maximum position of the sphere are inverted, and a defective angle distribution 1704 that changes by π in the middle as shown in FIG. 17C is created.

  Furthermore, since the square root of the sum of the squares of the two components is created as in the denominator or numerator of Equations 4 to 8, it can only be a positive number. As a result, defect angle distributions 1704 and 1705 are obtained. Originally, the good angle distribution 1706 is a desirable result.

  If the angle created by the conventional method is sent directly to the control device of the processing machine and processed by the processing machine, each axis suddenly rotates at a high speed or the tool moves to an unexpected position, resulting in tool breakage. , Processing machine breakage, cutting, and uncut material.

  Therefore, the present invention provides means for smoothing the angle change by eliminating the sudden angle change of the rotation axis when creating NC data by NURBS interpolation based on the tool movement trajectory of the CL data generated by the host CAM system. suggest.

Embodiment 1

  FIG. 1 is a block diagram showing a system configuration of Embodiment 1 of a numerically controlled curved surface machining apparatus according to the present invention. More specifically, it is a block diagram showing the configuration of the NC post processor device 1130 of the present invention.

  The CAM system 1110 operating on the host computer uses the finished shape CAD data defined by the CAD system or the like to create CL data for the multi-axis controlled curved surface processing machine 1150 and stores it in the CL data file 1120. The CAM system 1110 also stores the processing machine configuration of the processing machine 1150 in the CL data file 1120.

  The CL data includes a tool tip position vector and a tool spindle direction vector, and is created in a work coordinate system defined by the CAM system. The processing machine configuration is expressed by character symbols indicating the first rotation axis, the second rotation axis, the tool axis, and the master axis of the processing machine 1150.

  The NC post-processor 1130 includes a reading unit 1160 for reading CL data and a processing machine configuration from a CL data file 1120 created by the host CAM system 1110, a machine coordinate conversion unit 1170, an NC data conversion unit 1180, and an NC data transmission unit. 1190.

  Further, the machine coordinate conversion unit 1170 includes a component conversion matrix / angle addition value generation unit 1171, a component conversion unit 1172, a second angle generation unit 1173, a second angle correction unit 1174, and a first angle generation unit 1175. The first angle correction unit 1176, the machine coordinate transformation matrix creation unit 1177, and the machine coordinate transformation unit 1178. Each of the means 1171 to 1190 may be realized by software by a computer processing device that operates the NC post processor device 1130.

  The NC control mechanism 1140 numerically controls the numerically controlled curved surface processing machine 1150. The coordinate system for determining the tool position of the processing machine 1150 has three basic axes X, Y, and Z that are orthogonal to each other. The axes that control the tool spindle direction are two of the rotation axes A, B, and C. is there.

  Next, the operation of the NC post processor device 1130 will be described.

  The CL data / machining machine configuration reading means 1160 includes CL data consisting of a tool tip position vector (X, Y, Z) and a tool spindle direction vector (I, J, K) from the CL data file 1120, a first rotation axis, The processing machine configuration including the second rotation axis, tool axis, and master axis is read.

  The component conversion matrix / angle addition value creating means 1171 is a component conversion matrix Ma and standard coordinates for converting the tool spindle direction vector (I, J, K) into the standard coordinate system (α1, α2, α3) based on the machine configuration. An axis conversion matrix for converting the tool axis in the system to the designated tool axis, and an angle addition value Δ for changing the reference position at the time of angle calculation by the master axis are created.

  FIG. 2 is a chart showing a correspondence relationship between the processing machine configuration, the component conversion matrix Ma, the axis conversion matrix Mc, and the angle addition value Δ. For example, when the first rotation axis is the A axis, the second rotation axis is the C axis, the tool axis is the Z axis, and the master axis is not specified, the component conversion matrix Ma is (α1, α2, α3) is (K, I, −J), the axis conversion matrix is set so that the Z axis is the tool axis, and the angle addition value Δ is set to 0.

  The component conversion means 1172 converts the tool spindle direction vector (I, J, K) with the component conversion matrix Ma and converts it into the tool spindle direction vector (α1, α2, α3) of the standard coordinate system as shown in Equation 11. .

第２角度作成手段１１７３は、数式１２のように、標準座標系の工具主軸方向ベクトル(α２，α３)から逆正接を求める。計算機に実装する場合は、計算機用言語としてＣ＋＋などの言語を使用し、逆正接を求めるためにatan2関数を用いる。

The second angle creating means 1173 obtains the arc tangent from the tool principal axis direction vector (α2, α3) in the standard coordinate system as shown in Equation 12. When implemented in a computer, a language such as C ++ is used as a computer language, and an atan2 function is used to obtain an arc tangent.

図３は、第２角度作成手段１１７３で求めた角度から計算機実装上の制限事項を考慮して補正する補正手順を示すフローチャートである。

FIG. 3 is a flowchart showing a correction procedure for correcting from the angle obtained by the second angle creating means 1173 in consideration of restrictions on the implementation of the computer.

  The second angle correction means 1174 corrects the angle calculated by the second angle creation means 1173 in consideration of restrictions on computer implementation.

  In a 0/0 identification step 1310, it is determined whether both α2 and α3 are 0, and an identifier representing 0/0 is set in the angle θ1. As this identifier, a value other than the range of −π to π, which is the definition range of the angle θ1, for example, a value such as 99.0 is set.

  In a difference value creation step 1320, a difference value between adjacent angles θ1 is obtained. If the start point is an identifier representing 0/0, the next difference value is subtracted from the next angle to determine the start point angle. If the first adjacent angle is a 0/0 identifier, the previous difference value is set. If the second adjacent angle is a 0/0 identifier, the next difference value is set. Since the angle is determined in this way, the angle change does not increase due to the limitation of the built-in function.

  In the difference value correction step 1330, it is determined whether the size of the created difference value is π or more. If the difference value is π or more, the difference value, the difference value + π, the difference value −π, the difference value + 2π, Five difference values of difference value −2π are created, and the smallest value among the five values is set as the difference value.

  In the difference value addition step 1340, finally, the angle is obtained by adding the difference value to the previous angle other than the angle of the start point. In this way, the angle is set so that the change in the angle is minimized, so that the change in the angle does not increase.

  The first angle creating means 1175 is inversed according to Equation 14 from the component (α4) obtained from the angle corrected by the second angle correcting means 1174 according to Equation 13 and (α1) of the tool spindle direction vector in the standard coordinate system. Find tangent. When implemented in a computer, a language such as C ++ is used as a computer language, and an atan2 function is used to obtain an arc tangent.

第１角度補正手段１１７６は、計算機実装上の制限事項を考慮して、第１角度作成手段１１７５で求めた角度を補正する。

The first angle correction unit 1176 corrects the angle obtained by the first angle creation unit 1175 in consideration of restrictions on computer implementation.

  FIG. 4 is a flowchart showing a correction procedure for correcting from the angle obtained by the first angle creating means in consideration of restrictions on the computer implementation.

  In a difference value creation step 1410, a difference value between adjacent angles θ2 is obtained.

  In the difference value correction step 1420, it is determined whether or not the magnitude of the difference value is equal to or greater than π. If the difference value is equal to or greater than π, three difference values, that difference value, its difference value + 2π, and its difference value −2π, are created. The value with the smallest size among the three is set as the difference value.

  In the difference value addition step 1430, the angle addition value Δ is added to the second angle at the start point, and the difference value is added to the previous angle to obtain the angle. In this way, the angle is set so that the change in the angle is minimized, so that the change in the angle does not increase.

  The machine coordinate transformation matrix creating means 1177 creates machine coordinate transformation matrices Mb, M1, and M2 shown in Formula 15 from the first angle and the second angle.

  In Expression 15, Mx, My, and Mz are X, Y, and Z coordinate values of the processing machine 1150, and represent coordinate values after machine coordinate conversion. X, Y, and Z are tool tip position vectors in the workpiece coordinate system.

  The matrix Mb is a work coordinate as viewed from the origin of the machine coordinate system, which is an intersection point where the first axis rotation center line and the second axis rotation center line of the processing machine are orthogonal, with the component conversion matrix Ma as a rotation component as in Expression 16. It consists of a matrix Ms whose moving component is the position vector (Xs, Ys, Zs) of the system origin.

  The matrix M1 is a rotation matrix when rotating around the first rotation axis as shown in Expression 17, the matrix M2 is the rotation matrix when rotating around the second rotation axis as shown in Expression 18, and the matrix Mc is a standard. 13 is an axis conversion matrix used when a tool axis in a coordinate system is aligned with a tool axis specified by the processing machine configuration in FIG.

機械座標変換手段１１７８は、機械座標変換行列Ｍｂ，Ｍ１，Ｍ２を用い、数式１５に従って、ワーク座標系での工具先端位置ベクトルを機械座標系の座標値に変換する。

The machine coordinate conversion unit 1178 uses the machine coordinate conversion matrices Mb, M1, and M2 to convert the tool tip position vector in the workpiece coordinate system into coordinate values in the machine coordinate system according to Equation 15.

  The NC data conversion means 1180 converts the coordinate value and angle in the machine coordinate system into the NC data format.

  The NC data transmission means 1190 sends the converted NC data to the NC control device 1140.

  The NC control mechanism 1140 interprets the sent NC data and sends a movement command value for each axis to the processing machine 1150.

  As described above, the second angle correction unit 1174 corrects the restricted angle created by the second angle creation unit 1173, and the first angle correction unit 1176 creates the restriction angle created by the first angle creation unit 1175. Since a certain angle is corrected, favorable angle distributions 1505, 1605, and 1706 shown in FIGS. 15, 16, and 17 can be created.

  As a result, it is possible to prevent a phenomenon in which each axis suddenly rotates at a high speed or the tool moves to an unexpected place when machining with the machining machine 1150, so that the tool breakage, the machining machine breakage, the cutting, or the uncut material remains. Less processing is possible.

Embodiment 2

  FIG. 5 is a block diagram showing a system configuration of Embodiment 2 of the numerically controlled curved surface machining apparatus according to the present invention.

  The second embodiment is an embodiment in which the machine coordinate conversion means of the numerically controlled curved surface processing apparatus disclosed in Patent Document 1 is replaced with the coordinate conversion means 1170 in the post processor device 1130 of FIG.

  Since the coordinate conversion unit 1170 can avoid a sudden change in angle due to restrictions on computer implementation, even in the second embodiment, each axis suddenly rotates at a high speed, or the tool moves to a place that is not assumed. Phenomenon is prevented, and machining with less tool breakage, machine breakage, cutting, and uncut material becomes possible.

  The units 1171 to 1190 of the machine coordinate conversion unit 1170 according to the second embodiment are realized as software processing steps by a processing unit of a computer that operates the NC post processor unit 20.

  The host computer 10 stores the tool tip position vector and the spindle direction vector calculated in the machining path direction in the coordinate system (work coordinate system) in which the curved surface shape is defined in the external file 11 as CL data. The curved surface data created by the host computer 10 is divided as a number of straight lines within a certain allowable value along the tool movement path displayed in the workpiece coordinate system. The CL data 11 is created by describing the tool tip position, the tool spindle direction vector, and the workpiece coordinate system feed speed at the generated individual division points in the order of the tool movement path.

  In step 21, the created CL data 11 is taken into the NC post processor device 20 for conversion into NC data for operating the NC processing device based on the machine configuration of the numerically controlled curved surface processing device 30.

  In steps 22 to 1170, position vectors of the three linear axes and the rotation angle based on the mechanical configuration of the numerically controlled curved surface processing apparatus 30 are obtained.

  In step 22, the NC post processor device 20 instructs a tool correction No. in order to correct an error existing between the tool length and tool diameter assumed at the time of NC data creation and the actual tool length and tool diameter. It requests the NC device 33 to output correction data. The NC device 33 reads the correction data corresponding to the instructed correction No. from the correction data storage area 34 and outputs it to the NC post processor device 20. The NC post processor device 20 reads the correction data output from the NC device 33.

  In step 23, the NC post processor device 20 corrects the CL data in accordance with the direction to be corrected.

  In step 24, CL data is thinned out or added to improve the processing accuracy while reducing the amount of data.

  In step 25, the NURBS curve calculated in step 24 is divided. The path division position is obtained from the NURBS curve of the tool tip position vector and the broken line tool path. If the distance between the passing points suddenly decreases or the angle of the broken line changes suddenly, the NURBS curve is disturbed. Therefore, a portion where the interval is shortened and a portion where the angle of the broken line changes greatly are found, and the curve is divided at the path division point by using the point as the path division point of the curve, thereby improving the accuracy of the curve.

  In step 1170, as described in the first embodiment, the CL data is coordinate-transformed into the machine coordinate system.

  In step 27, a knot vector is calculated.

  In step 28, the formulas (1), (2), and (2) are calculated from the linear three-axis and rotary two-axis point sequence data converted from the workpiece coordinate system CL data to the machine coordinate system and the knot vector calculated in step 27. Create the NURBS curve of 3).

  In step 29, a blending coefficient is calculated. The chord length of the tool tip position vector in the workpiece coordinate system is calculated with higher accuracy including the point 92 thinned out in step 24, and is set as a knot vector in the workpiece coordinate system.

  In step 30, the machining speed in the machine coordinate system is calculated.

  In step 31, the control points of the three linear NURBS curves in the machine coordinate system calculated in steps 28, 29 and 30 are converted into NC data according to the format of the NURBS interpolation command.

  In step 32, the last converted NC data is transmitted as NC data from the NC post-processor 20 and is read and stored in the NC data storage area 35 of the NC controller 33.

  The NC control mechanism 36 incorporating the NURBS interpolation function of the NC control device 33 reads the NC data from the NC data storage area 35 and controls the 5-axis or 4-axis control NC machine 50 while executing the NC machining. .

  FIG. 6 is a diagram illustrating a knot vector setting method.

  As described in Patent Document 1, the knot vector of the NURBS curve in the machine coordinate system is derived by the method of obtaining the knot vector by blending the behavior of the tool tip axis and the behavior of the machine coordinate system shown in FIG.

  However, in Patent Document 1, it is considered that the segment is divided in response to a sudden bending change of the tool tip point, but the segment division and the fillet insertion method regarding the bending change on the machine coordinate side are considered. It wasn't. As a result, there is a possibility that waviness or distortion of the machined surface may occur due to the bending operation on the machine coordinate axis that cannot be found only by the behavior of the tool tip.

  On the other hand, in the second embodiment, as shown in FIGS. 7 and 8, the processing accuracy is improved so that the behavior on the machine coordinate axis can be considered.

  FIG. 7 is a diagram illustrating the behavior of the orthogonal coordinate axes in the machine coordinate system.

  The fold in this behavior can be understood as a curved motion in the XYZ space, similar to the behavior of the tool tip. However, the movement of the rotating coordinate axes is usually very difficult to understand as such a curved motion.

  FIG. 8 is a diagram illustrating a method of replacing the rotating coordinate system in the machine coordinate system with an orthogonal coordinate system.

  In the second embodiment, mapping is performed as shown in FIG. 8 to capture the behavior of the rotational coordinate axis. Usually, when the operation of the rotating shaft is expressed by paying attention only to the rotating operation, the expression method is like a globe shown in FIG. At this time, for example, the A axis and the B axis, which are rotational coordinate systems, are applied as longitude and latitude, respectively.

  In this expression method, it is very difficult to determine whether or not there is a fold in the movements of P0, P1, and P2 that are trajectories in the rotation axis direction.

  Therefore, the behavior is analyzed by mapping the locus in the direction of the rotation axis on a two-dimensional plane as shown in FIG. For example, the rotation angle of the A axis is applied to the horizontal axis, and the rotation angle of the B axis is applied to the vertical axis.

  Then, the movement of P0, P1, and P2, which are trajectories in the direction of the rotation axis, is captured similarly to the curve expressed by the normal two-dimensional plane, and the position of P1 is independent of the behavior of the orthogonal coordinate system and the behavior of the tool tip. It can be grasped that a crease occurs in

  In step 28, a NURBS curve in the machine coordinate system of each of the three orthogonal axes and the rotation angle axis is calculated. When the method shown in FIG. 8B is used, the segment division position is inserted based on the behavior in the rotary coordinate system as well as the segment division position based on the behavior of the conventional tool tip and the orthogonal axis of the machine coordinate system. become able to.

  The two-dimensionally mapped rotation angle in FIG. 8B is not limited to a range from −180.0 to 180.0, and can be expressed beyond the range. For example, if the next position after the position of 170 ° is 10 °, if the range is limited to −180.0 to 180.0, the angle is returned by 190 °, such as 170 ° → 0 ° → 10 °. There must be. On the other hand, if the next position 10 ° is expressed as 190 °, similarly to the method of expressing the globe, it is sufficient to advance by 20 ° from 170 ° to 190 °, and the moving direction can be expressed by the shortest distance.

  FIG. 9 is a diagram showing a method of inserting a fillet at a rotational coordinate angle replaced with an orthogonal coordinate system.

  If this two-dimensional mapping is used, as shown in FIG. 9, it is also possible to create it like a fillet insertion in a normal two-dimensional curve.

  It is also possible to apply the technique shown in Formula 10 and FIG. 12 to ensure continuity for the connection conditions at this time.

  Thereafter, from step 29 to step 32, an NC data command based on the NURBS curve in the machine coordinates is created and transmitted to the NC device 21.

  The NC control mechanism 223 incorporating the NURBS interpolation function of the NC control device 21 reads the NC data from the NC data storage area 222 and controls the 5-axis or 4-axis control NC machine 30 while performing the NC processing.

  When the NC data output format is provided by a general free curve, the present invention uses the same procedure to interpolate X, Deriving the values of Y and Z, the values of α and β which are the control points of the free curve of the two rotation axes, the knot vector K, the weight R, and the value of F which is the control point of the machine coordinate system feed rate free curve, It can also be applied when converting to NC data for NC machining.

  As a machine tool behavior control method, it can be applied not only to control at the machine center position but also to control at the tool tip position.

  When not only a NURBS curve but also a free curve is used as the tool movement trajectory interpolation method, an equivalent free curve and its function can be used as the rotation axis angle interpolation method.

  When performing free curve interpolation using the rotation axis angle converted to the machine coordinate system as a control point, the tool axis rotation angle that can be a control point can be changed, and the tool axis rotation angle control point can be added or thinned out flexibly. .

It is a block diagram which shows the system | strain structure of Embodiment 1 of the numerical control curved surface processing apparatus by this invention. It is a chart which shows the correspondence of processing machine composition, component conversion matrix Ma, axis conversion matrix Mc, and angle addition value delta. It is a flowchart which shows the correction | amendment procedure which correct | amends considering the restriction matter on computer mounting from the angle calculated | required by the 2nd angle preparation means. It is a flowchart which shows the correction | amendment procedure which correct | amends considering the restriction matter on computer mounting from the angle calculated | required by the 1st angle preparation means. It is a block diagram which shows the system | strain structure of Embodiment 2 of the numerical control curved surface processing apparatus by this invention. It is a figure which shows the setting method of a knot vector. It is a figure which shows the behavior of a machine coordinate system orthogonal axis. It is a figure which shows the method of replacing the rotation coordinate system in a machine coordinate system with an orthogonal coordinate system. It is a figure which shows the method of the fillet insertion of the rotation coordinate angle replaced with the orthogonal coordinate system. It is a figure which compares and shows the conventional linear interpolation processing method and the conventional NURBS interpolation processing method. It is a figure which shows the relationship between a NURBS curve and a control point. It is a figure which shows the relationship of the connection part of two NURBS curves. It is a figure which shows the behavior of the rotating shaft of a machine coordinate system derived | led-out only considering the continuity of the feed rate. It is a figure which shows the cutting in the position where a rotation angle changes rapidly. It is a figure which shows the malfunction by 0/0 on computer mounting. It is a figure which shows the malfunction by the domain restriction | limiting of a solution on computer implementation-pi radians to pi radians. It is a figure which shows the malfunction by vector component inversion.

Explanation of symbols

10 Host CAM system 11 CL data file 20 NC post processor device 21 CL data reading 22 Correction data acquisition 23 CL data correction 24 CL data thinning and addition 25 Curve division 26 Machine coordinate system conversion 27 Knot vector conversion 28 Linear three axes, rotation angle , NURBS curve calculation 29 Trajectory blending coefficient setting 30 Machine coordinate system feed speed calculation 31 NC data conversion 32 NC data transmission 33 Numerical controller 34 Correction data storage area 35 NC data storage area 36 NC control mechanism (built-in NURBS interpolation function)
1110 Host CAM system 1120 CL data file 1130 NC post processor unit 1140 NC control unit 1150 5-axis or 4-axis control NC processing machine 1160 CL data, processing machine configuration reading unit 1170 Machine coordinate conversion unit 1180 NC data conversion 1190 NC data transmission

Claims (1)

In a numerically controlled curved surface machining apparatus including a simultaneous multi-axis controlled NC machine that is numerically controlled by an NC machine having three linear axes orthogonal to each other and two rotary axes for controlling the tool spindle direction and having a numerical control NURBS interpolation function ,
The CL data consisting of the calculated tool tip position vector data and tool spindle direction vector in the processing path direction the work coordinate system curved shape is defined by the host computer, the first axis of rotation of the simultaneous multi-axis control NC machine A component conversion matrix / angle addition value creating means for converting into a standard coordinate system component for operating the NC processing machine based on a processing machine configuration including a second rotation axis, a tool axis, and a master axis,
The component transformation matrix / angle addition value creating means includes:
Component conversion means for converting the tool spindle direction vector from a workpiece coordinate system to a standard coordinate system;
Second angle creation means for creating a second angle that is a rotation angle around the second rotation axis of the tool spindle direction vector in the standard coordinate system based on the converted tool spindle direction vector of the standard coordinate system; ,
Second angle correction means for creating a continuous angle distribution from a distribution of second angles created for a plurality of control points in the machining path direction by the second angle creation means;
A first angle that is a rotation angle around the first rotation axis of the tool spindle direction vector based on the tool spindle direction vector rotated by a second angle around the second rotation axis created by the second angle correction means First angle creating means for creating
First angle correction means for creating a continuous angle distribution from a distribution of first angles created for a plurality of control points in the machining path direction by the first angle creation means;
A matrix for converting a tool tip position vector in a workpiece coordinate system into a machine coordinate system using the second angle created by the second angle correction means and the first angle created by the first angle correction means. A machine coordinate transformation matrix creation means to be obtained;
Machine coordinate conversion means for converting a tool tip position vector into a machine coordinate system using the obtained machine coordinate conversion matrix;
Means for converting the converted data of the machine coordinate system into NC data,
In the second angle correction means, the components in the second rotation axis direction and the tool axis direction of the tool spindle direction vector used for obtaining the second angle created by the second angle creation means are both zero. It is assumed that the identifier is set by detecting the state, the difference value of the second angle between all adjacent control points is obtained, and if the second angle cannot be obtained by the identifier, the control point Another difference value is created by using the difference value of the adjacent control points of the second and when the magnitude of the created another difference value is π or more, the difference value, the difference value + π, the difference value −π, The smallest difference value is detected from the difference value + 2π and the difference value −2π to obtain a new difference value, and the difference value is added to the second angle of the adjacent control point to obtain the second angle of the control point. ,
The first angle correction means obtains a difference value of the first angle between all adjacent control points. When the magnitude of the difference value is π or more, the difference value, the difference value + 2π, the difference value− The smallest value is detected from 2π to obtain a new difference value, and the first angle of the control point is obtained by adding the difference value to the first angle of the control point adjacent to the control point. Numerically controlled curved surface processing equipment.

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