Feed motion calculation method for double-output-shaft five-axis numerical control tool grinding machine

Abstract

The invention discloses a feeding motion calculation method for a double-output-shaft five-axis numerical control tool grinding machine, and the method specifically comprises the steps: building a unified coordinate system according to the mechanism characteristics and solving demands of the grinding machine, and the unified coordinate system comprises a machine tool coordinate system, a machining coordinate system, a workpiece coordinate system and a grinding wheel coordinate system; grinding machine structure parameters are set and comprise the offset of the original point of a machining coordinate system relative to the C axis, grinding machine structure offset examples of the offset of the original point of the machining coordinate system relative to the B axis, the grinding wheel installation distance and the grinding wheel installation direction; a universal grinding machine feeding kinematics equation is established by considering the inward and outward mounting conditions of main shafts at the left end and the right end of the grinding wheel; and solving based on grinding wheel installation transformation and grinding machine stroke constraint. According to the method for solving the partitioned selective solution based on the actual travel limit of the machine tool, the solution is more universal and practical, the actual travel limit of the machine tool is met, and the method has good adaptability.

Description

Technical Field

[0001] The present invention belongs to the field of post-processing methods for five-axis CNC machine tools, and in particular relates to a feed motion calculation method for a dual-output-axis five-axis CNC tool grinder. Background Art

[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-end spindle grinders face limitations such as the need to replace grinding wheels, which affects machining efficiency. As a new type of grinder structure, the dual-output-axis five-axis CNC tool grinder is more flexible and versatile, improving machining efficiency. Because it has dual output shafts, there are multiple ways to install the grinding wheel on this type of grinder. It also has features such as grinder structure offset, making it a non-standard five-axis CNC machine tool. Currently, research on the feed motion algorithm for standard five-axis CNC tool grinders is relatively sufficient. However, for grinders with special structures, especially those with dual output shaft structures, research on the feed motion algorithm is relatively weak. A universal feed motion algorithm that is easy to understand, systematic, and takes into account the stroke constraints in actual machining conditions has not yet been formed. Summary of the Invention

[0003] In order to solve the feed motion calculation problem caused by the characteristics of a dual-output-shaft five-axis CNC tool grinder, the present invention provides a feed motion calculation method for a dual-output-shaft five-axis CNC tool grinder.

[0004] A method for calculating the feed motion of a dual-output-shaft five-axis CNC tool grinder of the present invention comprises the following steps:

[0005] Step 1: According to the characteristics of the grinding machine mechanism and the solution requirements, a unified coordinate system is established, including: machine tool coordinate system, processing 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 each motion axis, and the coordinate origin is the farthest end of the positive direction of each axis.

[0007] Processing coordinate system O M -X M Y M Z M :This coordinate system is the basis for describing the motion of each grinding machine feed axis, that is, the coordinate basis of the grinding machine NC program. In order to enhance the adaptability of the kinematic model, this paper defines the origin O M It is the center point of the tool chuck end face, and the coordinate axis direction is the same as the machine tool coordinate system.

[0008] 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 for the grinding wheel tool position file. Without loss of generality, this paper defines the origin O W The center point of the cross section of the cutting edge end of the tool (the distance from the tool point is d t ).

[0009] Grinding wheel coordinate system O G -X G Y G Z G :This coordinate system is the basis for describing the parameters of the grinding wheel installation position of the double-ended spindle. In order to unify the motion transformation 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 the machine tool coordinate system.

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

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

[0012] The origin of the machining coordinate system appears X relative to the C axis M O M Y M In-plane offsets, including X M Axis offset and Y M Axis offset; select the origin of the machining coordinate system relative to the C axis in the Y M The offset in the axial direction is analyzed and defined as d C , which is expressed as the C-axis component of the machine tool in the processing coordinate system Y M Axis direction coordinates.

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

[0014] The origin of the machining coordinate system appears X relative to the B axis M O M Y M In-plane offsets, including X M Axis offset and Y M Axis offset; select the origin of the machining coordinate system relative to the B axis in the X M The offset in the axial direction is analyzed and defined as d B , which is expressed as the B-axis component of the machine tool in the processing coordinate system X M Axis direction coordinates.

[0015] Grinding wheel installation distance:

[0016] The distance between the center point of the grinding wheel end surface and the origin of the grinding wheel coordinate system describes the X coordinate of the initial installation position of the grinding wheel in the grinding wheel coordinate system. G The coordinates of the axis, 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 machined coordinate system. Inward installation is defined as the installation direction of the grinding wheel pointing to the origin of the grinding wheel coordinate system, and outward installation is defined as the installation direction of the grinding wheel pointing to the origin of the grinding wheel coordinate system. m is used to represent the axis of the grinding wheel in X M Directional vector, that is, if the left spindle is installed inward and the right spindle is installed outward, m=1; if the right spindle is installed inward and the left spindle is installed outward, m=-1.

[0019] Step 3: Based on steps 1 and 2, consider the spindles at the left and right ends of the grinding wheel and whether they are installed inward or outward, and establish a universal grinding machine feed kinematic equation.

[0020] Use S X 、S Y 、S Z To express the feed amount of X, Y, and Z axes, first define the unified kinematic matrix of motion around the translation axis X, Y, and Z axis as:

[0021]

[0022] Use S B 、S C The kinematic matrix representing the feed of the B and C axes and the motion around the rotation axes B and C is:

[0023]

[0024] The tool position data includes the grinding wheel axis vector and tool position coordinates in the workpiece coordinate system, which are expressed as homogeneous column vectors: U W is (i,j,k,1) T 、P W is (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 is (m,0,0,0) T 、P G is (0,0,0,1) T .

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

[0027]

[0028] Where:

[0029] The coordinate transformation of the grinding wheel installation position-Z axis motion axis represents the grinding wheel installation distance d G The bias and the structural bias d B The offset of the initial tool setting point position caused by the tool change.

[0030] T XYZ It is the motion transformation of the Z-axis motion axis to the X-axis motion axis, which represents the motion of the three translation axes of the grinder.

[0031] The X-axis motion axis-B-axis motion axis motion transformation represents the motion of the two rotating axes of the grinder; among them, the C-axis rotation axis has an offset d C , there is a structural offset d in the B-axis rotation axis B .

[0032] is the motion transformation of the B-axis motion axis-workpiece coordinate system, which represents the transformation from the machining coordinate system to the workpiece coordinate system; a(-θ) Represents the motion transformation matrix of the rotation θ around the a-axis, and obtains the coordinate transformation matrix

[0033] Solving the kinematic equation yields:

[0034]

[0035] Step 4: Solution based on grinding wheel installation transformation and grinding machine travel constraints.

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

[0037] Solution for the feed amount of the rotary feed axis:

[0038] When solving in interval 1, S C The expression is:

[0039] S C =marcsink, (m=±1) (5)

[0040] When solving in interval 2, S C The expression is:

[0041]

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

[0043]

[0044] The value of parameter b in formula (7) is as follows:

[0045]

[0046] Solution of the translation axis feed motion:

[0047] The rotation axis feed amount S obtained above is B and S C Substituting into formula (4), we get S X 、S Y and S Z The solution expression is:

[0048]

[0049] The beneficial technical effects of the present invention are:

[0050] The present invention proposes a solution method for partitioned interval selection based on the actual stroke limit of the machine tool, which makes the solution more universal and practical, meets the actual stroke limit of the machine tool, and has good adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the machine tool coordinate system.

[0052] Figure 2 Schematic diagram of machining coordinate system and workpiece coordinate system.

[0053] Figure 3 Schematic diagram of the grinding wheel coordinate system.

[0054] Figure 4 Schematic diagram of the offset of the origin of the machining coordinate system relative to the C-axis.

[0055] Figure 5 Schematic diagram of the offset of the origin of the machining coordinate system relative to the B-axis.

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

[0057] Figure 7 Schematic diagram of processing results in each case. DETAILED DESCRIPTION

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

[0059] A method for calculating the feed motion of a dual-output-shaft five-axis CNC tool grinder of the present invention comprises the following steps:

[0060] Step 1: The specific structure of the dual output shaft five-axis CNC tool grinder is as follows: Figure 1 As shown. The main difference between this grinder and other grinders is that the spindle output is divided into two ends. Its motion axis consists of two rotating axes and three translation axes. Feed motion calculation requires solving the motion transformation equation of the grinding wheel vector and the grinding wheel coordinate from the grinding wheel group coordinate system to the workpiece coordinate system, so as to obtain the feed amount expression of each feed axis. In order to establish the mathematical model for solution, establish Figures 1 to 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 each motion axis, such as Figure 1 shown.

[0062] Processing coordinate system O M -X M Y M Z M :This coordinate system is the basis for describing the motion of each grinding machine feed axis, that is, the coordinate basis of the grinding machine NC program. In order to enhance the adaptability of the kinematic model, this paper defines the origin O M is the center point of the tool chuck end face, and the coordinate axis direction is the same as the machine tool coordinate system, such as Figure 2 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 for the grinding wheel tool position file. Without loss of generality, this paper defines the origin O W The center point of the cross section of the cutting edge end of the tool (the distance from the tool point is d t ), origin O W Position and axis direction are as follows Figure 3 shown.

[0064] Grinding wheel coordinate system O G -X G Y G Z G :This coordinate system is the basis for describing the parameters of the grinding wheel installation position of the double-ended spindle. In order to unify the motion transformation 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 the machine tool coordinate system. Figure 4 shown.

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

[0066] Offset of the machining coordinate system origin 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, the origin of the machining coordinate system appears X relative to the C axis. M O M Y M In-plane offsets, including X M Axis offset and Y M Axis offset; select the origin of the machining coordinate system relative to the C axis in the Y M The offset in the axial direction is analyzed and defined as d C , which is expressed as the C-axis component of the machine tool in the processing coordinate system Y M Axis direction coordinates.

[0068] Grinding machine structure offset of the machining coordinate system origin 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, the origin of the machining coordinate system appears X relative to the B axis. M O M Y M In-plane offsets, including X M Axis offset and Y M Axis offset; select the origin of the machining coordinate system relative to the B axis in the X M The offset in the axial direction is analyzed and defined as d B , which is expressed as the B-axis component of the machine tool in the processing coordinate system X M Axis direction coordinates.

[0070] Grinding wheel installation distance:

[0071] Grinding wheel installation distance Figure 6 As shown in the figure, it is the distance between the center point of the grinding wheel processing end face and the origin of the grinding wheel coordinate system, which describes the X coordinate of the initial installation position of the grinding wheel in the grinding wheel coordinate system. G The coordinates of the axis, relative to the origin O G The distance is d G .

[0072] Grinding wheel installation direction:

[0073] Grinding wheel installation direction Figure 6 As shown in the figure, the direction from the machined end face to the non-machined end face describes the axis vector of the grinding wheel in the machined coordinate system. Since the grinding machine has dual output shafts and the structure of the grinding wheel group is complex, there are many situations for the installation direction of the grinding wheel. Inward installation is defined as the installation direction of the grinding wheel pointing to the origin of the grinding wheel coordinate system, and the opposite is outward installation. m is used to represent the X-axis of the grinding wheel.M Directional vector, that is, if the left spindle is installed inward and the right spindle is installed outward, m=1; if the right spindle is installed inward and the left spindle is installed outward, m=-1.

[0074] Step 3: Based on steps 1 and 2, consider the spindles at the left and right ends of the grinding wheel and whether they are installed inward or outward, and establish a universal grinding machine feed kinematic equation.

[0075] Use S X 、S Y 、S Z Represents the feed amount of X, Y, and Z axes, and defines the unified kinematic matrix of motion around the translation axis X, Y, and Z axis as:

[0076]

[0077] Use S B 、S C The kinematic matrix representing the feed of the B and C axes and the motion around the rotation axes B and C is:

[0078]

[0079] The tool position data includes the grinding wheel axis vector and tool position coordinates in the workpiece coordinate system, which are expressed as homogeneous column vectors: U W is (i,j,k,1) T 、P W is (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 is (m,0,0,0) T 、P G is (0,0,0,1) T .

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

[0082]

[0083] Where:

[0084] The coordinate transformation of the grinding wheel installation position-Z axis motion axis represents the grinding wheel installation distance d G The bias and the structural bias d B The offset of the initial tool setting point position caused by the tool change.

[0085] T XYZIt is the motion transformation of the Z-axis motion axis to the X-axis motion axis, which represents the motion of the three translation axes of the grinder.

[0086] The X-axis motion axis-B-axis motion axis motion transformation represents the motion of the two rotating axes of the grinder; among them, the C-axis rotation axis has an offset d C , there is a structural offset d in the B-axis rotation axis B .

[0087] is the motion transformation of the B-axis motion axis-workpiece coordinate system, which represents the transformation from the machining coordinate system to the workpiece coordinate system; a(-θ) Represents the motion transformation matrix of the rotation θ around the a-axis, and obtains the coordinate transformation matrix

[0088] Solving the kinematic equation yields:

[0089]

[0090] The value of m is shown in Table 1:

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

[0092]

[0093]

[0094] Step 4: Solution based on grinding wheel installation transformation and grinding machine travel constraints.

[0095] When solving the feed rate of the rotary feed axis, the solution involves the calculation of inverse trigonometric functions, so directly solving it will make the calculated value of the rotary feed rate within the range of [-π / 2, π / 2]. Because it cannot cover the full stroke of the C axis, it is necessary to expand the solution range to [-π, π]. C The solution is divided into two intervals: interval one ([-π / 2, π / 2]) and interval two ([-π, -π / 2) ∪ (π / 2, π]).

[0096] When solving the feed amount of the linear feed axis, it is necessary to change the above solution interval according to the actual feed axis limit of the machine tool. First, select interval 1 for solution. However, if S is only solved within interval 1, C , which may cause the Z axis to exceed the travel range. By analyzing formula (4), we can know that in order to avoid S Z Less than S Zmin , need to adjust interval 2 to S C The solution interval can be used to obtain S with opposite signs. Z .

[0097] Solution for the feed amount of the rotary feed axis:

[0098] When solving in interval 1, S C The expression is:

[0099] S C =marcsink, (m=±1) (5)

[0100] When solving in interval 2, S C The expression is:

[0101]

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

[0103]

[0104] The value of parameter b in formula (7) is as follows:

[0105]

[0106] Solution of the translation axis feed motion:

[0107] The rotation axis feed amount S obtained above is B and S C Substituting into formula (4), we get S X 、S Y and S Z The solution expression is:

[0108]

[0109] Feed motion calculation example:

[0110] Based on a domestically produced Jingli MG200 dual-output-spindle five-axis tool grinder, we used the machining of an arc end mill as an example and verified it using tool slot parameters. The machine parameters and tool position coordinates are shown in Tables 2 and 3, respectively.

[0111] Table 2 Machine tool parameters

[0112]

[0113] Table 3 Arc end mill spiral groove grinding wheel tool position trajectory (partial)

[0114]

[0115]

[0116] The NC files for the four installation directions are calculated and obtained, as shown in Tables 4 to 7.

[0117] Table 4 NC file for right spindle grinding wheel installation with outward

[0118]

[0119] Table 5 NC file for installing the right spindle grinding wheel inward

[0120]

[0121] Table 6 NC file for installing the left spindle grinding wheel with the grinding wheel facing outward

[0122]

[0123]

[0124] Table 7 NC file for installing the left spindle grinding wheel inward

[0125]

[0126] The four grinding wheel installation directions are represented by a, b, c, and d respectively. The NC files of the four installation directions are processed and simulated. The results are as follows: Figure 7 As shown in the figure, the workpiece results obtained from the NC file processing simulation in the four installation directions 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: The following steps are involved: Step 1: According to the characteristics of the grinding machine mechanism and the solution requirements, a unified coordinate system is established, including: machine tool coordinate system, processing 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 each motion axis, and the coordinate origin is the farthest end of the positive direction of each axis; Processing coordinate system O M -X M Y M Z M :This coordinate system is the reference for describing the motion of each grinding machine feed axis, that is, the coordinate reference of the grinding machine NC program; in order to enhance the adaptability of the kinematic model, the origin O is defined M It is the center point of the tool chuck end face, and the coordinate axis direction is the same as the machine tool coordinate system; Workpiece coordinate system O W -X W Y W Z W :This coordinate system is the basis for describing the grinding motion of the grinding wheel relative to the workpiece, that is, the coordinate basis of the grinding wheel tool position file; define the origin O W The center point of the cross section of the cutting edge end of the tool is d, and the distance from the tool point is t ; Grinding wheel coordinate system O G -X G Y G Z G :This coordinate system is the basis for describing the parameters of the grinding wheel installation position of the double-ended spindle; in order to unify the motion transformation of the double-ended spindle; define the origin O G It is the mirror point of the left and right spindles, and the coordinate axis direction is the same as the machine tool coordinate system; Step 2: Set the grinding machine structural parameters, including the offset of the machining coordinate system origin relative to the C-axis, the offset of the machining coordinate system origin relative to the B-axis, the grinding machine structural offset, the grinding wheel installation distance, and the grinding wheel installation direction; Offset of the machining coordinate system origin relative to the C axis: The origin of the machining coordinate system appears X relative to the C axis M O M Y M In-plane offsets, including X M Axis offset and Y M Axis offset; select the origin of the machining coordinate system relative to the C axis in the Y M The offset in the axial direction is analyzed and defined as d C , which is expressed as the C-axis component of the machine tool in the processing coordinate system Y M Coordinates in the axis direction; Grinding machine structure offset of the machining coordinate system origin relative to the B axis: The origin of the machining coordinate system appears X relative to the B axis M O M Y M In-plane offsets, including X M Axis offset and Y M Axis offset; select the origin of the machining coordinate system relative to the B axis in the X M The offset in the axial direction is analyzed and defined as d B , which is expressed as the B-axis component of the machine tool in the processing coordinate system X M Coordinates in the axis direction; Grinding wheel installation distance: The distance between the center point of the grinding wheel end surface and the origin of the grinding wheel coordinate system describes the X coordinate of the initial installation position of the grinding wheel in the grinding wheel coordinate system. G The coordinates of the axis, 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 machined coordinate system. Inward installation is defined as the installation direction of the grinding wheel pointing to the origin of the grinding wheel coordinate system, and outward installation is defined as the installation direction of the grinding wheel pointing to the origin of the grinding wheel coordinate system. m is used to represent the axis of the grinding wheel in X M Directional vector, that is, if the left spindle is installed inward and the right spindle is installed outward, m=1; if the right spindle is installed inward and the left spindle is installed outward, m=-1; Step 3: Based on steps 1 and 2, consider the installation of the left and right spindles of the grinding wheel and the installation facing inward or outward, and establish a universal grinding machine feed kinematic equation; Use S X 、S Y 、S Z Represents the feed amount of X, Y, and Z axes, and defines the unified kinematic matrix of motion around the translation axis X, Y, and Z axis as: Use S B 、S C The kinematic matrix representing the feed of the B and C axes and the motion around the rotation axes B and C is: The tool position data includes the grinding wheel axis vector and tool position coordinates in the workpiece coordinate system, which are expressed as homogeneous column vectors: U W is (i,j,k,1) T 、P W is (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 is (m,0,0,0) T 、P G is (0,0,0,1) T ; The kinematic equation is established by transforming the grinding wheel axis vector and the tool position coordinates from the tool coordinate system to the workpiece coordinate system: Where: The coordinate transformation of the grinding wheel installation position-Z axis motion axis represents the grinding wheel installation distance d G The bias and the structural bias d B The offset of the initial tool setting point position caused by T XYZ It is the motion transformation between the Z-axis motion axis and the X-axis motion axis, which represents the motion of the three translation axes of the grinder; The X-axis motion axis-B-axis motion axis motion transformation represents the motion of the two rotating axes of the grinder; among them, the C-axis rotation axis has an offset d C , there is a structural offset d in the B-axis rotation axis B ; is the motion transformation of the B-axis motion axis-workpiece coordinate system, which represents the transformation from the machining coordinate system to the workpiece coordinate system; a(-θ) Represents the motion transformation matrix of the rotation θ around the a-axis, and obtains the coordinate transformation matrix Solving the kinematic equations yields: Step 4: Solving the problem based on the grinding wheel installation transformation and the grinding machine travel constraint; Expand the solution interval to [-π, π]: S C The solution is divided into two intervals: interval 1 [-π / 2, π / 2] and interval 2 [-π, -π / 2)∪(π / 2, π); Solution for the feed amount of the rotary feed axis: When solving in interval 1, S C The expression is: S C =m arcsin k,(m=±1) (5) When solving in interval 2, S C The expression is: The S corresponding to formula (6) B The expression is: The value of parameter b in formula (7) is as follows: Solution of the linear axis feed motion: The rotation axis feed amount S obtained above is B and S C Substituting into formula (4), we get S X 、S Y and S Z The solution expression is:

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