CN114578760B - Post-treatment method for ultrasonic cutting of straight blade tip knife - Google Patents

Abstract

A post-processing method for ultrasonic cutting of straight-edge sharp tools, which involves a new type of post-processing method for tool processing. The purpose of the invention is to solve the problem that when a straight-edged sharp knife is used for ultrasonic cutting of curved surface parts, CNC programming cannot be directly performed in CAM software and there is no corresponding post-processing software to use. The invention has the following steps: S1. Use a flat-end milling cutter to perform five-axis CNC programming on the part; S2. Convert the tool position point and the tool axis vector; S3. Calculate the X, Y, Z, A, and C coordinate values of the machine; S4 , Calculate the rotation angle H of the straight blade tip knife. The invention can be used for ultrasonic cutting of various types of honeycomb core materials, solves the application problem that straight-edge sharp knives cannot process curved surface parts, broadens the application range of straight-edge sharp knives, thereby greatly improving the processing efficiency of parts.

Description

A post-processing method for ultrasonic cutting of straight-edge sharp knives

Technical field

The invention relates to the technical field of numerical control machining, and in particular to a post-processing method for ultrasonic cutting of straight-edge sharp knives.

Background technique

As a new lightweight material, honeycomb core composite materials are widely used in aerospace, rail transportation and other fields because of their extremely high specific strength and specific stiffness, excellent fatigue resistance and corrosion resistance. With the large number of applications of honeycomb core curved surface parts, higher requirements have been put forward for ultrasonic cutting of this material.

When using a straight-edged tip tool for ultrasonic cutting of honeycomb core curved surface parts, the tool performs high-frequency cutting motion and requires continuous deflection. However, existing CAM programming technology cannot directly realize this action requirement and there is no corresponding post-processing software. Although some scholars have proposed equivalent alternative programming methods and corresponding post-processing methods, after analysis, this method still has major limitations, including programming errors and tool rotation limitations, which make it impossible to process complex curved surface parts. Therefore, for The development of corresponding post-processing software for this requirement has become an important issue that needs to be solved urgently.

Contents of the invention

The purpose of the invention is to solve the problem that when a straight-edged sharp knife is used for ultrasonic cutting of curved surface parts, CNC programming cannot be directly performed in CAM software and there is no corresponding post-processing software to use.

The technical solution of the present invention is: a post-processing method for ultrasonic cutting of straight-edge sharp knives, which has the following steps:

S1. Use a flat-end milling cutter to perform five-axis CNC programming on the part and obtain the corresponding tool position file;

S2. Obtain the tool position point and tool axis vector of the flat-end milling cutter from the tool position file. Based on this, convert the tool position point and tool axis vector of the straight-edge tool to be programmed, and calculate the real-time tool surface vector of the straight-edge tool;

S3. Calculate the X, Y, Z, A, and C coordinate values of the machine based on the information of the straight edge tool;

S4. Based on the rotation matrix when the straight-edge tip knife rotates angle A and C, obtain the rotated tool surface vector, and calculate the rotation angle of the straight-edge tip knife based on the relationship between the rotated tool surface vector and the real-time tool surface vector.

Further, the bottom surface radius of the flat end mill is e;

The half-angle of the tip of the straight-edged sharp knife is θ, the half-length of the bottom edge is d, and the pendulum length of the tool is L;

In step S2, the specific calculation process for converting the tool position point and the tool axis vector is as follows:

After five-axis CNC programming of the part, the flat-end milling cutter will generate the corresponding tool position point o (x, y, z) and tool axis vector t (i, j, k) at each tool position point, so that The line connecting each two adjacent knife points can form a tangent vector, recorded as r. By cross-multiplying the cutter axis vector and the tangent vector, we can obtain the normal vector of the neutral surface of the flat-end milling cutter, that is, the cutter surface vector of the straight-edged tip cutter, which is recorded as w, and its calculation formula is: w=t×r;

The cutter axis vector t of the flat end milling cutter is the blade vector of the straight-edged tip tool. Rotate t around the tool surface vector w at the tip by rotating the angle θ, and the cutter axis vector T of the straight-edged tip cutter can be obtained, that is, T = R·t . Among them, R is the rotation matrix of the flat-end milling cutter axis vector t rotating around w, w' is the unit vector of w, and the coordinate values are (a, b, c).

Homogenize the tool axis vectors and rotation matrices of the flat-end milling cutter and the straight-edge tip tool respectively:

t＝(ijk 0) ^T and T＝(i'j'k' 0) ^T

Furthermore, by translating the center D of the bottom surface of the milling cutter by the radius e along the cutter surface vector w, the straight edge tip point E can be obtained, that is, E=D+ew'. With the help of the right-hand screw rule, the direction vector G of the tool bottom edge at point O can be obtained. Then the point E is translated by a distance d along the direction vector G to obtain the tool position point O, that is, G=T×w and O=E+dG '.

Further, in step S3, the specific calculation process of the X, Y, Z, A, and C coordinate values of the computer bed is as follows:

The present _invention takes an AC double _- swing head five-axis _{CNC machine} tool as an _example to _illustrate . The machine tool coordinate system ( _{O M} Tool coordinate system (O _T X _T Y _T Z _T ,TCS). At _{the same} time, _place the origin of the reference coordinate system at the _rotation center of _the AC _double swing head, that is, the reference coordinate system ( _{O R} ) coincide with each other. Assume that the axial distance from the tool center point O _T to the swing head rotation center O _P is L, that is, the tool swing length is L. In the initial state, TCS and WCS coincide, and the tool position point and tool axis vector of the tool in RCS can be expressed as homogeneous coordinates:

P＝(0 0 -L 1) ^T and Q＝(0 0 1 0) ^T

When the machine tool motion command is (X, Y, Z, A, C), MCS, RCS and WCS remain stationary, and the rotation center coordinate system will translate X, Y, Z in the three main vector directions respectively. At the same time, the double swing head will also drive the tool to rotate through angle A and angle C respectively around the rotation center. The available translation matrix and rotation matrix are:

When the machine tool moves, the distance between RCS and WCS is always L, so its translation matrix is:

In WCS, the tool position point and tool axis vector of the tool can be expressed by homogeneous coordinates as:

P _W = (xyz 1) ^T and Q _W = (ijk 0) ^T

It can be seen from the motion relationship that the total transformation matrix is:

(P _W , Q _W ) = T _S · R _A · R _C · T _L · (P, Q)

The motion control commands of the above various available machine tools are:

In step S4, the specific calculation process for calculating the rotation angle H of the straight-edged sharp knife is as follows:

Homogenize the starting tool face vector: w ₀ = (1000) ^T , and the tool face vector of the straight-edged tool after rotating A and C in the initial state is: w'=R _A ·R _C ·w ₀ , however, there is still a certain angle between the tool surface vector at this time and the real tool surface vector at this position. This included angle is the desired rotation angle H of the straight edge tip tool, where:

Since the H angle obtained above is a scalar quantity and does not have directionality, the right-hand spiral rule is used to determine its direction. A new direction vector F=w'×w is defined, and the positive and negative directions are determined by the positive and negative z value of this vector. Rotation judgment, that is: when F _z > 0, H > 0, the spindle rotates forward, and vice versa.

Compared with the prior art, the present invention has the following beneficial effects:

Currently, the existing post-processing methods for ultrasonic cutting of straight-edge sharp tools have major limitations, mainly including programming errors and tool rotation limitations. The reason is that there are certain problems with the straight-edge sharp tool programming method and the spindle rotation angle algorithm. The present invention systematically proposes a post-processing solution for straight-edge sharp knives. By introducing the concept of blade vector, the data conversion of existing tools in CAM software to straight-edge sharp knives is realized, and the problem that straight-edge sharp knives cannot be directly programmed is solved. Programming errors caused by equivalent substitution methods are avoided. At the same time, the posture and rotation angle of the straight-edged tool are determined in the space rectangular coordinate system, thereby realizing the ultrasonic cutting of various complex curved surfaces with the straight-edged tool.

Based on the above reasons, the present invention can be widely promoted in the field of CNC machining.

Description of drawings

Figure 1 is a post-processing flow chart of ultrasonic cutting with a straight edge tip.

Figure 2 is a three-dimensional view of feature 1.

Figure 3 is a three-dimensional view of feature 2.

Figure 4 is a diagram showing the conversion of some tool location files into NC codes.

Figure 5 is an enlarged view of the two features after processing and their partial enlargement.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.

As shown in Figures 1 to 5, a post-processing method for ultrasonic cutting of straight-edge sharp tools has the following steps:

S1. Use a flat-end milling cutter to perform five-axis CNC programming on the part and obtain the corresponding tool position file;

S2. Obtain the tool position point and tool axis vector of the flat-end milling cutter from the tool position file. Based on this, convert the tool position point and tool axis vector of the straight-edge tool to be programmed, and calculate the real-time tool surface vector of the straight-edge tool;

S3. Calculate the X, Y, Z, A, and C coordinate values of the machine based on the information of the straight edge tool;

S4. Based on the rotation matrix when the straight-edge tip knife rotates angle A and C, obtain the rotated tool surface vector, and calculate the rotation angle of the straight-edge tip knife based on the relationship between the rotated tool surface vector and the real-time tool surface vector.

The radius of the flat end mill is e;

The half-angle of the tip of the straight-edged sharp knife is θ, the half-length of the bottom edge is d, and the pendulum length of the tool is L;

In this embodiment, the bottom radius of the flat-end milling cutter is e=5mm, the tool tip half angle θ of the straight-edged tool is 11.5°, the bottom cutting edge half length d=0.9mm, and the tool pendulum length L=500mm.

In step S2, the specific calculation process for converting the tool position point and the tool axis vector is as follows:

After five-axis CNC programming of the part, the flat-end milling cutter will generate the corresponding tool position point o (x, y, z) and tool axis vector t (i, j, k) at each tool position point, so that The line connecting each two adjacent knife points can form a tangent vector, recorded as r. By cross-multiplying the cutter axis vector and the tangent vector, we can obtain the normal vector of the neutral surface of the flat-end milling cutter, that is, the cutter surface vector of the straight-edged tip cutter, which is recorded as w, and its calculation formula is: w=t×r;

The cutter axis vector t of the flat end milling cutter is the blade vector of the straight-edged tip tool. Rotate t around the tool surface vector w at the tip by rotating the angle θ, and the cutter axis vector T of the straight-edged tip cutter can be obtained, that is, T = R·t . Among them, R is the rotation matrix, w’ is the unit vector of w, and the coordinate values are (a, b, c).

Homogenize the tool axis vector and rotation matrix respectively:

t＝(ijk 0) ^T and T＝(i'j'k' 0) ^T

By translating the center D of the bottom surface of the milling cutter by the radius e along the cutter face vector w, the straight edge tip point Q can be obtained, that is, E=D+ew'. With the help of the right-hand screw rule, the direction vector G of the tool bottom edge at point O can be obtained. Then the point E is translated by a distance d along the direction vector G to obtain the tool position point O, that is, G=T×w and O=E+dG '.

In step S3, the specific calculation process of the X, Y, Z, A, and C coordinate values of the computer bed is as follows:

The present _invention takes an AC double _- swing head five-axis _{CNC machine} tool as an _example to _illustrate . The machine tool coordinate system ( _{O M} Tool coordinate system (O _T X _T Y _T Z _T ,TCS). At _{the same} time, _place the origin of the reference coordinate system at the _rotation center of _the AC _double swing head, that is, the reference coordinate system ( _{O R} ) coincide with each other. Assume that the axial distance from the tool center point O _T to the swing head rotation center O _P is L, that is, the tool swing length is L. In the initial state, TCS and WCS coincide, and the tool position point and tool axis vector of the tool in RCS can be expressed as homogeneous coordinates:

P＝(0 0 -L 1) ^T and Q＝(0 0 1 0) ^T

When the machine tool motion command is (X, Y, Z, A, C), MCS, RCS and WCS remain stationary, and the rotation center coordinate system will translate X, Y, Z in the three main vector directions respectively. At the same time, the double swing head will also drive the tool to rotate through angle A and angle C respectively around the rotation center. The available translation matrix and rotation matrix are:

and/>

When the machine tool moves, the distance between RCS and WCS is always L, so its translation matrix is:

In WCS, the tool position point and tool axis vector of the tool can be expressed by homogeneous coordinates as:

P _W = (xyz 1) ^T and Q _W = (ijk 0) ^T

It can be seen from the motion relationship that the total transformation matrix is:

(P _W , Q _W ) = T _S · R _A · R _C · T _L · (P, Q)

The motion control commands of the above various available machine tools are:

In step S4, the specific calculation process for calculating the rotation angle H of the straight-edged sharp knife is as follows:

Homogenize the starting tool surface vector: w ₀ = (1 0 0 0) ^T . The tool surface vector of the straight edge tool after rotating A and C in the initial state is: w' = R _A ·R _C ·w ₀ , however, there is still a certain angle between the tool surface vector at this time and the real tool surface vector at this position. This angle is the desired straight-edge tip tool rotation angle H, where:

Since the H angle obtained above is a scalar quantity and does not have directionality, the right-hand spiral rule is used to determine its direction. A new direction vector F=w'×w is defined, and the positive and negative directions are determined by the positive and negative z value of this vector. Rotation judgment, that is: when F _z > 0, H > 0, the spindle rotates forward, and vice versa.

By performing CNC programming and post-processing on the two features shown in Figures 2 and 3, the machine tool processing NC code shown in Figure 4 can be obtained. Figure 5 shows the two processed feature parts and their partial enlarged views. It can be seen that the entire workpiece and each feature edge are well processed, consistent with the built three-dimensional model. This specific embodiment can solve the application problem that a straight-edged sharp knife cannot process curved surface parts, thereby greatly improving the processing efficiency of the parts.

The present invention is not limited to the specific embodiments described above. Those of ordinary skill in the art should understand that in specific application scenarios, when the bottom radius e of the flat end milling cutter, the tip half angle of the straight edge tip cutter is θ, and the bottom cutting edge half length When d or the tool pendulum length L is changed, the final machine tool processing NC code can be affected, but these changes are also within the protection scope of the present invention.

Claims (2)

1. A post-processing method for ultrasonic cutting of straight-edge sharp knives, which is characterized by having the following steps: S1. Use a flat-end milling cutter to perform five-axis CNC programming on the part and obtain the corresponding tool position file; S2. Obtain the tool position point and tool axis vector of the flat-end milling cutter from the tool position file. Based on this, convert the tool position point and tool axis vector of the straight-edge tool to be programmed, and calculate the real-time tool surface vector of the straight-edge tool; S3. Calculate the X, Y, Z, A, and C coordinate values of the machine based on the information of the straight edge tool; S4. Based on the rotation matrix when the straight-edge tip knife rotates A and C, obtain the rotated tool surface vector, and calculate the rotation angle of the straight-edge tip knife based on the relationship between the rotated tool surface vector and the real-time tool surface vector; The step S2 specifically includes the following steps: The corresponding tool location point o(x,y,z) and tool axis vector t(i,j,k) generated by the flat-end milling cutter recorded in the obtained tool location file at each tool location point; The line connecting each two adjacent knife points constitutes a tangent vector, recorded as r; By cross-multiplying the cutter axis vector and the tangent vector, we can obtain the normal vector of the neutral surface of the flat-end milling cutter, that is, the cutter surface vector of the straight-edged tip cutter, which is recorded as w, and its calculation formula is: w=t×r; The cutter axis vector t of the flat end milling cutter is the blade vector of the straight-edged tip tool. Rotate t around the tool surface vector w at the tip by rotating the angle θ, and the cutter axis vector T of the straight-edged tip cutter can be obtained, that is, T = R·t , where R is the rotation matrix, w' is the unit vector of w, and the coordinate values are (a, b, c), Homogenize the tool axis vector and rotation matrix respectively: t=(ij k 0) ^T and T=(i'j'k'0) ^T ; By translating the center D of the bottom surface of the milling cutter by the radius e along the tool surface vector w, we can obtain the straight-edge tool edge point E, that is, E=D+ew'. With the help of the right-hand screw rule, we can obtain the direction vector G of the tool bottom edge at point O, Then move the point E along the direction vector G by a distance d to obtain the tool position point O, that is, G=T×w and O=E+dG'; where e is the bottom radius of the flat-end milling cutter, and θ is the The half-angle of the tip of a straight-edged knife, d is the half-length of the bottom edge; The step S3 specifically includes the following steps: Establish the machine tool coordinate system of the AC double-swing head five _- axis CNC _machine tool, denoted as O _M X _M Y _M Z _M , _MCS , the workpiece coordinate system, denoted as _O W _{is O T _ _ _ _ _ O P _ _ _ _} And in RCS, the tool position point and tool axis vector of the tool can be expressed by homogeneous coordinates: P=(0 0 -L 1) ^T and Q=(0 0 1 0) ^T ; When the machine tool motion command is (X, Y, Z, A, C), MCS, RCS and WCS remain stationary, and the rotation center coordinate system will translate X, Y, Z respectively in the three main vector directions. At the same time, The double swing head will also drive the tool to rotate through angle A and angle C respectively around the rotation center. The translation matrix and the rotation matrix when the straight-edged tip tool rotates angle A and angle C are respectively: and/> When the machine tool moves, the distance between RCS and WCS is always L, so its translation matrix is: In WCS, the tool position point and tool axis vector of the tool can be expressed by homogeneous coordinates as: P _W = (xyz 1) ^T and Q _W = (ijk 0) ^T It can be seen from the motion relationship that the total transformation matrix is: (P _W , Q _W ) = T _S · R _A · R _C · T _L · (P, Q) The motion control commands of the above various available machine tools are: In step S4, the specific calculation process for calculating the rotation angle H of the straight-edged sharp knife is as follows: Homogenize the starting tool surface vector: w ₀ = (1 0 0 0) ^T . The tool surface vector of the straight edge tool after rotating A and C in the initial state is: w' = R _A ·R _C ·w ₀ , the angle between the rotated tool surface vector and the real-time tool surface vector is the desired straight-edge tip tool rotation angle H, where: 2. The method according to claim 1, characterized in that: Use the right-hand screw rule to determine the direction of the H angle, define a new direction vector F=w'×w, and judge the positive and negative direction based on the positive or negative z value of this vector, that is: when F _z >0, H> 0, the spindle rotates forward. When F _z <0, H <0, the spindle rotates reversely.