A feed motion calculation method of a double-output-shaft five-axis numerical control tool grinder

Abstract

The application discloses a kind of feed movement calculation methods of double-output shaft five-axis numerical control tool grinder, specifically is: according to the characteristics of grinder mechanism and solving demand, establish unified coordinate system, including: machine tool coordinate system, processing coordinate system, workpiece coordinate system and grinding wheel coordinate system;Grinder structure parameters are set, including the offset of the origin of processing coordinate system relative to C-axis, the offset of the origin of processing coordinate system relative to B-axis grinder structure offset example, grinding wheel installation distance and grinding wheel installation direction;Considering the left and right end spindle of grinding wheel, the installation condition of inside and outside, establish general grinder feed kinematics equation;Based on the solution of grinding wheel installation transformation and grinder stroke constraint.The application proposes a kind of solving method based on machine tool actual stroke limit interval selection solution, so that solving is more universal and practical, meets machine tool actual stroke limit, has good adaptability.

Description

Technical Field

[0001] This invention belongs to the field of post-processing methods for five-axis CNC machine tools, and particularly relates to a method for calculating the feed motion of a dual-output-axis five-axis CNC tool grinder. Background Technology

[0002] A five-axis CNC tool grinder is a type of grinder used for machining cutting tools. When multiple grinding wheels are required for machining, common single-spindle grinders face limitations such as the need to change grinding wheels, affecting machining efficiency. The dual-output-axis five-axis CNC tool grinder, as a new type of grinder structure, offers greater flexibility and versatility, improving machining efficiency. Because it has two output axes, this type of grinder can have multiple grinding wheel mounting methods and also exhibits characteristics such as grinder structure offset, classifying it as a non-standard five-axis CNC machine tool. Currently, research on feed motion algorithms for standard five-axis CNC tool grinders is relatively comprehensive. However, research on feed motion algorithms for grinders with special structures, especially those with dual output axes, is still relatively weak. A universal feed motion algorithm that is easy to understand, systematic, and considers stroke constraints under actual machining conditions has not yet been developed. Summary of the Invention

[0003] To address the feed motion calculation problem caused by the characteristics of a dual-output-axis five-axis CNC tool grinder, this invention provides a method for calculating the feed motion of a dual-output-axis five-axis CNC tool grinder.

[0004] The present invention provides a method for calculating the feed motion of a dual-output-axis five-axis CNC tool grinder, comprising the following steps:

[0005] Step 1: Based on the characteristics of the grinding machine mechanism and the solution requirements, establish a unified coordinate system, including: machine tool coordinate system, machining coordinate system, workpiece coordinate system and grinding wheel coordinate system.

[0006] Machine tool coordinate system O-XYZ: This coordinate system represents the inherent properties of each motion axis of the machine tool. The direction of each axis is the same as the positive direction of motion of each axis, and the origin of the coordinate system is the farthest point of the positive direction of each axis.

[0007] Machining coordinate system O M -X M Y M Z M This coordinate system serves as the reference for describing the motion of each feed axis of the grinding machine, i.e., the coordinate reference for the grinding machine's NC program. To enhance the adaptability of the kinematic model, this paper defines the origin O. M The coordinate axis is the center point of the tool chuck end face, and its direction is the same as that of the machine tool coordinate system.

[0008] Workpiece coordinate system O W -X W Y W Z WThis coordinate system is the reference for describing the grinding motion of the grinding wheel relative to the workpiece, i.e., the coordinate reference of the grinding wheel toolpath file. Without loss of generality, this paper defines the origin O. W The center point of the cross-section at the end of the cutting edge of the tool (distance d from the tool setting point) t ).

[0009] Grinding wheel coordinate system O G -X G Y G Z G This coordinate system serves as the reference for describing the grinding wheel mounting position parameters of the double-ended spindle. To standardize the motion transformations of the double-ended spindle, this paper defines the origin O. G It is the mirror point of the left and right spindles, and the coordinate axis direction is the same as that of the machine tool coordinate system.

[0010] Step 2: Set the grinding machine structure parameters, including the grinding machine structure offset of the machining coordinate system origin relative to the C-axis, the grinding coordinate system origin relative to the B-axis, the grinding wheel installation distance, and the grinding wheel installation direction.

[0011] Offset of the origin of the machining coordinate system relative to the C-axis:

[0012] The origin of the machining coordinate system appears relative to the C-axis. M O M Y M In-plane bias, including X M Offset in the axial direction and Y M Offset in the axial direction; select the origin of the machining coordinate system relative to the C-axis in the Y direction. M The offset in the axial direction is analyzed, and this offset is defined as d. C This represents the position of the machine tool's C-axis component in the machining coordinate system Y. M Coordinates along the axis.

[0013] Grinding machine structure offset with the origin of the machining coordinate system offset relative to the B-axis:

[0014] The origin of the machining coordinate system appears relative to the B-axis X M O M Y M In-plane bias, including X M Offset in the axial direction and Y M Offset in the axial direction; select the origin of the machining coordinate system relative to the B-axis in the X direction. M We analyze the offset in the axial direction and define this offset as d. B This represents the B-axis component of the machine tool in the machining coordinate system X. M Coordinates along the axis.

[0015] Grinding wheel installation distance:

[0016] The distance between the center point of the grinding wheel's machining end face and the origin of the grinding wheel coordinate system describes the X-axis position of the initial installation position of the grinding wheel in the grinding wheel coordinate system. G The coordinates of the axes, relative to the origin O G The distance is d G .

[0017] Grinding wheel installation direction:

[0018] The direction from the machined end face to the non-machined end face describes the axis vector of the grinding wheel in the machining coordinate system; inward mounting is defined as the installation direction of the grinding wheel pointing towards the origin of the grinding wheel coordinate system, and vice versa for outward mounting; m represents the grinding wheel axis in the X-axis... M The direction vector is as follows: when the left spindle is installed inward and the right spindle is installed outward, m = 1; when the right spindle is installed inward and the left spindle is installed outward, m = -1.

[0019] Step 3: Based on Step 1 and Step 2, considering the left and right ends of the grinding wheel spindle and the inward or outward installation, establish a general grinding machine feed kinematic equation.

[0020] Use S X S Y S Z To represent the feed amounts along the X, Y, and Z axes, we first define the unified kinematics matrix for motion about the translational axes X, Y, and Z as follows:

[0021]

[0022] Use S B S C The kinematics representing the feed rates along axes B and C, and the motion about axes B and C, are as follows:

[0023]

[0024] Tool position data includes the grinding wheel axis vector and tool position coordinates in the workpiece coordinate system, represented as homogeneous column vectors: U W For (i,j,k,1) T P W (x, y, z, 1) T .

[0025] The initial axis vector and tool position coordinates of the grinding wheel in the grinding wheel coordinate system are: U G (m,0,0,0) T P G (0,0,0,1) T .

[0026] The kinematic equations are established by transforming the grinding wheel axis vector and tool position coordinates from the tool coordinate system to the workpiece coordinate system:

[0027]

[0028] In the formula:

[0029] The coordinate transformation of the grinding wheel mounting position - Z-axis motion axis represents the grinding wheel mounting distance d. G The bias and due to structural bias d B This causes an offset in the initial tool setting point position.

[0030] T XYZ The motion transformation from the Z-axis to the X-axis represents the motion of the three translational axes of the grinding machine.

[0031] The motion transformation from the X-axis to the B-axis represents the motion of the two rotary axes of the grinding machine; among them, the C-axis rotation axis has an offset d. C The B-axis rotation axis has a structural offset d B .

[0032] The motion transformation of the B-axis relative to the workpiece coordinate system represents the transformation from the machining coordinate system to the workpiece coordinate system; T... a(-θ) The motion transformation matrix represents the rotation around axis a by an angle θ, which yields the coordinate transformation matrix.

[0033] Solving the kinematic equations yields:

[0034]

[0035] Step 4: Solve based on grinding wheel mounting changes and grinding machine stroke constraints.

[0036] Extend the solution interval to [-π, π]: Let S... C The solution is divided into two intervals: interval 1 ([-π / 2, π / 2]) and interval 2 ([-π, -π / 2)∪(π / 2, π]).

[0037] Solution for rotary feed axis feed rate:

[0038] When solving for interval one, S C The expression is:

[0039] S C =marcsink, (m = ±1) (5)

[0040] When solving in interval two, S C The expression is:

[0041]

[0042] S corresponding to equation (6)B The expression is:

[0043]

[0044] The parameter b in equation (7) is selected in the following ways:

[0045]

[0046] Solving for the feed motion of the translation axis:

[0047] The rotary axis feed rate S obtained above B and S C Substituting into equation (4), we get S X S Y and S Z The solution expression is:

[0048]

[0049] The beneficial technical effects of this invention are as follows:

[0050] This invention proposes a solution method based on interval selection of solutions according to the actual travel limit of the machine tool, which makes the solution more universal and practical, meets the actual travel limit of the machine tool, and has good adaptability. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the machine tool coordinate system.

[0052] Figure 2 This is a schematic diagram of the machining coordinate system and the workpiece coordinate system.

[0053] Figure 3 This is a schematic diagram of the grinding wheel coordinate system.

[0054] Figure 4 This is a schematic diagram showing the offset of the origin of the machining coordinate system relative to the C-axis.

[0055] Figure 5 This is a schematic diagram showing the offset of the origin of the machining coordinate system relative to the B-axis.

[0056] Figure 6 This is a schematic diagram showing the installation distance and direction of the grinding wheel.

[0057] Figure 7 Diagrams showing the processing results for each scenario. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0059] The present invention provides a method for calculating the feed motion of a dual-output-axis five-axis CNC tool grinder, comprising the following steps:

[0060] Step 1: The specific structure of the dual-output-axis five-axis CNC tool grinder is as follows: Figure 1 As shown. The main difference between this grinding machine and other grinding machines is that its spindle output is divided into two ends. Its motion axes consist of two rotary axes and three translational axes. Calculating the feed motion requires solving the motion transformation equations of the grinding wheel vector and coordinate system from the grinding wheel coordinate system to the workpiece coordinate system, thereby obtaining the feed amount expression for each feed axis. To establish the mathematical model for solving this problem, a... Figures 1-4 The coordinate system shown.

[0061] Machine tool coordinate system O-XYZ: This coordinate system represents the inherent properties of each motion axis of the machine tool. The direction of each axis is the same as the positive direction of motion of that axis. For example... Figure 1 As shown.

[0062] Machining coordinate system O M -X M Y M Z M This coordinate system serves as the reference for describing the motion of each feed axis of the grinding machine, i.e., the coordinate reference for the grinding machine's NC program. To enhance the adaptability of the kinematic model, this paper defines the origin O. M The coordinate axis is the center point of the tool chuck end face, and its direction is the same as that of the machine tool coordinate system. Figure 2 As shown.

[0063] Workpiece coordinate system O W -X W Y W Z W This coordinate system is the reference for describing the grinding motion of the grinding wheel relative to the workpiece, i.e., the coordinate reference of the grinding wheel toolpath file. Without loss of generality, this paper defines the origin O. W The center point of the cross-section at the end of the cutting edge of the tool (distance d from the tool setting point) t ), origin O W Position and coordinate axis direction as follows Figure 3 As shown.

[0064] Grinding wheel coordinate system O G -X G Y G Z G This coordinate system serves as the reference for describing the grinding wheel mounting position parameters of the double-ended spindle. To standardize the motion transformations of the double-ended spindle, this paper defines the origin O. G These are the mirror images of the left and right spindles, with coordinate axes aligned with the machine tool coordinate system. Figure 4 As shown.

[0065] Step 2: Set the grinding machine structure parameters, including the grinding machine structure offset of the machining coordinate system origin relative to the C-axis, the grinding coordinate system origin relative to the B-axis, the grinding wheel installation distance, and the grinding wheel installation direction.

[0066] Offset of the origin of the machining coordinate system relative to the C-axis:

[0067] The offset of the origin of the machining coordinate system relative to the C-axis is as follows: Figure 4 As shown, this is the X-axis relative to the C-axis of the machining coordinate system origin. M O M Y M In-plane bias, including X M Offset in the axial direction and Y M Offset in the axial direction; select the origin of the machining coordinate system relative to the C-axis in the Y direction. M We analyze the offset in the axial direction and define this offset as d. C This represents the position of the machine tool's C-axis component in the machining coordinate system Y. M Coordinates along the axis.

[0068] Grinding machine structure offset with the origin of the machining coordinate system offset relative to the B-axis:

[0069] The offset of the origin of the machining coordinate system relative to the B-axis is as follows: Figure 5 As shown, this is the X-axis relative to the B-axis of the machining coordinate system origin. M O M Y M In-plane bias, including X M Offset in the axial direction and Y M Offset in the axial direction; select the origin of the machining coordinate system relative to the B-axis in the X direction. M We analyze the offset in the axial direction and define this offset as d. B This represents the B-axis component of the machine tool in the machining coordinate system X. M Coordinates along the axis.

[0070] Grinding wheel installation distance:

[0071] Grinding wheel installation distance as follows Figure 6 As shown, this represents the distance between the center point of the grinding wheel's machining end face and the origin of the grinding wheel coordinate system, describing the X-axis of the initial installation position of the grinding wheel in the grinding wheel coordinate system. G The coordinates of the axes, relative to the origin O G The distance is d G .

[0072] Grinding wheel installation direction:

[0073] Grinding wheel installation direction as follows Figure 6 As shown, this represents the direction from the machined end face to the non-machined end face, describing the axis vector of the grinding wheel in the machining coordinate system. Because grinding machines have dual output axes and the grinding wheel assembly has a complex structure, there are multiple possible grinding wheel installation directions. Inward installation is defined as the grinding wheel installation direction pointing towards the origin of the grinding wheel coordinate system, and outward installation is defined as the opposite. Let m represent the grinding wheel axis in the X...M The direction vector is as follows: when the left spindle is installed inward and the right spindle is installed outward, m = 1; when the right spindle is installed inward and the left spindle is installed outward, m = -1.

[0074] Step 3: Based on Step 1 and Step 2, considering the left and right ends of the grinding wheel spindle and the inward or outward installation, establish a general grinding machine feed kinematic equation.

[0075] Use S X S Y S Z The feed values ​​for the X, Y, and Z axes are represented by the unified kinematics matrix for motion about the translational axes X, Y, and Z:

[0076]

[0077] Use S B S C The kinematics representing the feed rates along axes B and C, and the motion about axes B and C, are as follows:

[0078]

[0079] Tool position data includes the grinding wheel axis vector and tool position coordinates in the workpiece coordinate system, represented as homogeneous column vectors: U W For (i,j,k,1) T P W (x, y, z, 1) T .

[0080] The initial axis vector and tool position coordinates of the grinding wheel in the grinding wheel coordinate system are: U G (m,0,0,0) T P G (0,0,0,1) T .

[0081] The kinematic equations are established by transforming the grinding wheel axis vector and tool position coordinates from the tool coordinate system to the workpiece coordinate system:

[0082]

[0083] In the formula:

[0084] The coordinate transformation of the grinding wheel mounting position - Z-axis motion axis represents the grinding wheel mounting distance d. G The bias and due to structural bias d B This causes an offset in the initial tool setting point position.

[0085] T XYZThe motion transformation from the Z-axis to the X-axis represents the motion of the three translational axes of the grinding machine.

[0086] The motion transformation from the X-axis to the B-axis represents the motion of the two rotary axes of the grinding machine; among them, the C-axis rotation axis has an offset d. C The B-axis rotation axis has a structural offset d B .

[0087] The motion transformation of the B-axis relative to the workpiece coordinate system represents the transformation from the machining coordinate system to the workpiece coordinate system; T... a(-θ) The motion transformation matrix represents the rotation around axis a by an angle θ, which yields the coordinate transformation matrix.

[0088] Solving the kinematic equations yields:

[0089]

[0090] The values ​​of m are shown in Table 1:

[0091] Table 1 Values ​​of grinding wheel shaft vector m

[0092]

[0093]

[0094] Step 4: Solve based on grinding wheel mounting changes and grinding machine stroke constraints.

[0095] When calculating the feed rate of the rotary axis, the solution involves inverse trigonometric function calculations. Therefore, directly solving for this will result in calculated feed rates within the range [-π / 2, π / 2]. Since this does not cover the entire travel of the C-axis, the solution range needs to be extended to [-π, π]. [The text then abruptly shifts to a different topic:] S... C The solution is divided into two intervals: interval 1 ([-π / 2, π / 2]) and interval 2 ([-π, -π / 2)∪(π / 2, π]).

[0096] When determining the feed rate of the translational feed axis, the aforementioned calculation interval needs to be changed according to the actual feed axis limitations of the machine tool. Initially, interval one is selected for calculation, but if S is only calculated within interval one... C This could cause the Z-axis to exceed its travel. Analysis of equation (4) shows that to avoid S... Z Less than S Zmin The second interval needs to be adjusted to S. C By finding the solution interval, we can obtain S with the opposite sign. Z .

[0097] Solution for rotary feed axis feed rate:

[0098] When solving for interval one, S C The expression is:

[0099] S C =marcsink, (m = ±1) (5)

[0100] When solving in interval two, S C The expression is:

[0101]

[0102] S corresponding to equation (6) B The expression is:

[0103]

[0104] The parameter b in equation (7) is selected in the following ways:

[0105]

[0106] Solving for the feed motion of the translation axis:

[0107] The rotary axis feed rate S obtained above B and S C Substituting into equation (4), we get S X S Y and S Z The solution expression is:

[0108]

[0109] Example of feed motion calculation:

[0110] Based on the domestically produced Jingli MG200 dual-output-axis five-axis tool grinder, this study takes the machining of a circular arc end mill as an example and verifies the machining using tool groove parameters. The machine tool parameters and tool position coordinates are shown in Tables 2 and 3, respectively.

[0111] Table 2 Machine Tool Parameter Table

[0112]

[0113] Table 3. Partial Tool Track of Helical Groove Cutting Tool for Circular End Mill.

[0114]

[0115]

[0116] The NC files for the four installation orientations were calculated and are shown in Tables 4 to 7.

[0117] Table 4 NC File for Right Spindle Grinding Wheel Facing Outwards Installation

[0118]

[0119] Table 5 NC File for Right Spindle Grinding Wheel Inward Mounting

[0120]

[0121] Table 6 NC File for Left Spindle Grinding Wheel Facing Outwards

[0122]

[0123]

[0124] Table 7 NC File for Left Spindle Grinding Wheel Inward Installation

[0125]

[0126] Let a, b, c, and d represent four grinding wheel mounting directions, respectively. NC files for each of the four mounting directions were subjected to machining simulation verification, and the results are as follows: Figure 7 As shown in the figure, the workpiece results obtained from the NC file machining simulation for the four mounting orientations are the same, thus verifying the correctness of the algorithm.

Claims

1. A method for calculating the feed motion of a dual-output-axis five-axis CNC tool grinder, characterized in that, Includes the following steps: Step 1: Based on the characteristics of the grinding machine mechanism and the solution requirements, establish a unified coordinate system, including: machine tool coordinate system, machining coordinate system, workpiece coordinate system and grinding wheel coordinate system; Machine tool coordinate system O-XYZ: This coordinate system represents the inherent properties of each motion axis of the machine tool. The direction of each axis is the same as the positive direction of motion of each axis. The origin of the coordinate system is the farthest point of the positive direction of each axis. Machining coordinate system O M -X M Y M Z M This coordinate system serves as the reference for describing the motion of each feed axis of the grinding machine, i.e., the coordinate reference for the grinding machine's NC program; to enhance the adaptability of the kinematic model, the origin O is defined. M The center point of the tool chuck end face is located, and the coordinate axis direction is the same as that of the machine tool coordinate system. Workpiece coordinate system O W -X W Y W Z W This coordinate system is the reference for describing the grinding motion of the grinding wheel relative to the workpiece, i.e., the coordinate reference of the grinding wheel toolpath file; the origin O is defined. W Let be the center point of the cross-section at the end of the cutting edge of the tool, and the distance from the tool setting point be d. t ; Grinding wheel coordinate system O G -X G Y G Z G This coordinate system serves as the reference for describing the grinding wheel mounting position parameters of the double-ended spindle; to unify the motion transformations of the double-ended spindle, the origin O is defined. G It is the mirror point of the left and right spindles, and the coordinate axis direction is the same as that of the machine tool coordinate system; Step 2: Set the grinding machine structure parameters, including the offset of the origin of the machining coordinate system relative to the C-axis, the offset of the origin of the machining coordinate system relative to the B-axis, the grinding wheel installation distance, and the grinding wheel installation direction; Offset of the origin of the machining coordinate system relative to the C-axis: The origin of the machining coordinate system appears relative to the C-axis in the X direction. M O M Y M In-plane bias, including X M Offset in the axial direction and Y M Offset in the axial direction; select the origin of the machining coordinate system relative to the C-axis in the Y direction. M We analyze the offset in the axial direction and define this offset as d. C This represents the position of the machine tool's C-axis component in the machining coordinate system Y. M Coordinates along the axis; Offset of the origin of the machining coordinate system relative to the B-axis: The origin of the machining coordinate system appears relative to the B-axis X M O M Y M In-plane bias, including X M Offset in the axial direction and Y M Offset in the axial direction; select the origin of the machining coordinate system relative to the B-axis in the X direction. M We analyze the offset in the axial direction and define this offset as d. B This represents the B-axis component of the machine tool in the machining coordinate system X. M Coordinates along the axis; Grinding wheel installation distance: The distance between the center point of the grinding wheel's machining end face and the origin of the grinding wheel coordinate system describes the X-axis position of the initial installation position of the grinding wheel in the grinding wheel coordinate system. G The coordinates of the axes, relative to the origin O G The distance is d G ; Grinding wheel installation direction: The direction from the machined end face to the non-machined end face describes the axis vector of the grinding wheel in the machining coordinate system; inward mounting is defined as the installation direction of the grinding wheel pointing towards the origin of the grinding wheel coordinate system, and vice versa for outward mounting; m represents the grinding wheel axis in the X-axis... M Directional vectors, i.e.: when the left spindle is installed inward and the right spindle is installed outward, m=1; when the right spindle is installed inward and the left spindle is installed outward, m=-1; Step 3: Based on Step 1 and Step 2, considering the left and right ends of the grinding wheel spindle and the inward or outward installation, establish a general grinding machine feed kinematic equation; Use S X S Y S Z The feed values ​​for the X, Y, and Z axes are represented by the unified kinematics matrix for motion about the translational axes X, Y, and Z: (1) Use S B S C The kinematics representing the feed rates along axes B and C, and the motion about axes B and C, are as follows: (2) Tool position data includes the grinding wheel axis vector and tool position coordinates in the workpiece coordinate system, represented as homogeneous column vectors: U W For (i,j,k,1) T P W (x, y, z, 1) T ; The initial axis vector and tool position coordinates of the grinding wheel in the grinding wheel coordinate system are: U G (m,0,0,0) T P G (0,0,0,1) T ; The kinematic equations are established by transforming the grinding wheel axis vector and tool position coordinates from the grinding wheel coordinate system to the workpiece coordinate system: (3) In the formula: The coordinate transformation of the grinding wheel mounting position - Z-axis motion axis represents the grinding wheel mounting distance d. G The bias and due to structural bias d B The resulting offset of the initial tool setting point position; The motion transformation from the Z-axis to the X-axis represents the motion of the three translational axes of the grinding machine. The motion transformation from the X-axis to the B-axis represents the motion of the two rotary axes of the grinding machine; among them, the C-axis rotation axis has an offset d. C The B-axis rotation axis has a structural offset d B ; The B-axis motion transformation between the workpiece coordinate system and the machining coordinate system represents the transformation from the machining coordinate system to the workpiece coordinate system with a distance of T. a(-θ) The transformation yields the coordinate transformation matrix. ;T a(-θ) The motion transformation matrix represents the rotation angle θ around the a-axis; Solving the kinematic equations yields: (4) Step 4: Solving based on grinding wheel mounting changes and grinding machine stroke constraints; Extend the solution interval to [-π, π]: Let S... C The solution is divided into two intervals: interval 1 [-π / 2, π / 2] and interval 2 [-π, -π / 2)∪(π / 2, π]. Determining the feed rate of the rotary feed axis: When solving for interval one, S C The expression is: (5) When solving in interval two, S C The expression is: (6) S corresponding to equation (6) B The expression is: (7) The parameter b in equation (7) is selected in the following ways: (8) Solving for the feed motion of the translation axis: The rotary axis feed rate S obtained above B and S C Substituting into equation (4), we get S X S Y and S Z The solution expression is: (9)。

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