A post-processing method of a five-axis double swing angle machine tool based on a C-axis

Abstract

The application discloses a post-processing method of a five-axis double-swing-angle machine tool based on a C shaft, and comprises the following steps: determining a conversion matrix from a tool coordinate system to a workpiece coordinate system according to the positions and vector directions of tools and workpieces corresponding to the machine tool; constructing a kinematic model of the corresponding form machine tool according to the coordinate conversion matrix; solving the moving distances of each motion axis of the machine tool under the conditions of with or without RTCP compensation according to the kinematic model; determining the swing angle of the fifth axis according to the included angle between the vector of the tool swing length in the tool position file and the corresponding projection; calculating the rotation angle of the C shaft according to the value of the fifth-axis swing angle; and calculating the fifth-axis swing direction of the first tool contact point in the machining track according to the rotation angles of the fifth axis and the C shaft and in combination with the kinematic model. Through the technical scheme, the problem of large stroke of the C shaft caused by the fact that the fifth axis of the existing machine tool only swings in a single direction is solved, the machining efficiency of the machine tool is improved, and the service life of the swing angle milling head is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of machine tool control, and in particular to a post-processing method of a five-axis double-swing-angle machine tool based on a C-axis. BACKGROUND

[0002] Five-axis machine tools have the advantages of high degree of freedom and high precision, and have obvious advantages in machining curved surface parts, so five-axis machine tools are widely used in aerospace, mold, marine, automobile and other industrial fields. However, compared with traditional three-axis machine tools, five-axis machine tools increase two rotational degrees of freedom, thereby increasing the complexity of the machine tool structure and the analysis difficulty of the post-processing calculation of the machine tool machining.

[0003] Five-axis machine tools with different kinematic chains need to match post-processors with different functional requirements. The traditional five-axis double-swing-angle machine tool is in the form of XYZAC or XYZBC motion, which has two rotating axes A (B) and C and three linear axes X, Y and Z. In recent years, research institutes have conducted a lot of research on the post-processing solution of five-axis machine tools, and the development of post-processors based on kinematic analysis has become mature. However, all current post-processing solution methods are based on a constructed kinematic model of the machine tool, and the model is only a linear or nonlinear equation set, and the solution result does not consider the actual working conditions of the machine tool. Sometimes there are the following disadvantages:

[0004] Firstly, the calculated value of the fifth axis of the machine tool is often positive. Taking the XYZBC motion form as an example, if the value of the fifth axis (B-axis) of the machine tool is positive, it will cause the swing angle head to swing only in one direction during machining, thereby affecting the service life.

[0005] In addition, since the B-axis only swings in one direction, it will cause the C-axis to rotate at a large angle during machining, thereby affecting the machining efficiency and the service life of the swing angle milling head. SUMMARY

[0006] In view of the above problems, the present application provides a post-processing method of a five-axis double-swing-angle machine tool based on a C-axis, which constructs a kinematic model of the machine tool cutter and workpiece, calculates the swing angle of the fifth axis and the C-axis, and further calculates the machining trajectory, thereby solving the problem of large C-axis travel caused by the fifth axis of the machine tool swinging only in one direction in the existing post-processing calculation of the machine tool, improving the machining efficiency of the machine tool, and prolonging the service life of the swing angle milling head.

[0007] To achieve the above purpose, the present application provides a post-processing method of a five-axis double-swing-angle machine tool based on a C-axis, comprising:

[0008] According to the position and vector direction of the tool and the workpiece corresponding to the form of the machine tool, a conversion matrix of the tool coordinate system to the workpiece coordinate system is determined;

[0009] According to the coordinate conversion matrix, a kinematic model of the corresponding form machine tool is constructed;

[0010] According to the kinematic model, the movement distances of each movement axis of the machine tool under the conditions of no RTCP compensation and RTCP compensation are solved;

[0011] According to the included angle between the vector of the tool swing length in the tool position file and the corresponding projection, the swing angle of the fifth axis is determined;

[0012] According to the value of the swing angle of the fifth axis, the rotation angle of the C-axis is calculated;

[0013] According to the rotation angles of the fifth axis and the C-axis, the swing direction of the fifth axis of the first tool contact point in the machining track is calculated in combination with the kinematic model.

[0014] In the above technical solution, preferably, according to the position and vector direction of the tool and the workpiece corresponding to the form of the machine tool, the conversion matrix of the tool coordinate system to the workpiece coordinate system is determined, and the specific process includes:

[0015] Set (P x , P y , P z , U x , U y , U z ) as the position and vector direction of the tool position file CLS;

[0016] According to the transformation relationship between each adjacent coordinate system, the conversion matrix of the tool coordinate system to the workpiece coordinate system is determined as:

[0017] [u w 0] T = w T t [u t 0] T

[0018] [p w 0] T = w T t [p t 0] T

[0019] Wherein, u w , u t , p w , p t are the initial vector direction of the workpiece, the initial vector direction of the tool, the initial position coordinate of the workpiece, and the initial position coordinate of the tool, respectively.w T t is a coordinate transformation matrix from the tool end to the workpiece end.

[0020] In the above technical solution, preferably, the corresponding form machine tool kinematics model is constructed according to the coordinate transformation matrix, and the specific process comprises:

[0021] The coordinate transformation matrix is multiplied to obtain the kinematics model of the five-axis linkage machine tool:

[0022]

[0023] Wherein, LT is the tool swing length, the tool swing length is the distance from the fifth axis rotation center to the tool tip point, LBC is the Z direction distance from the fifth axis rotation center to the C axis rotation center, α is the swing angle of the fifth axis, β is the swing angle of the C axis, L x is the linear distance of the machine tool X axis movement, L y is the linear distance of the machine tool Y axis movement, L z is the linear distance of the machine tool Z axis movement.

[0024] In the above technical solution, preferably, the movement distance of each movement axis of the machine tool under the conditions of no RTCP compensation and RTCP compensation is solved according to the kinematics model, and the specific process comprises:

[0025] The kinematics model is solved simultaneously to obtain the solution of each movement axis of the machine tool under the condition of no RTCP compensation:

[0026]

[0027] Under the condition of RTCP compensation, because the numerical control system inside the machine tool has compensated the X, Y and Z axes, the solution of each axis of the machine tool is:

[0028]

[0029] Wherein, if the value of α is positive, the swing angle of the fifth axis of the machine tool is positive.

[0030] In the above technical solution, preferably, the swing angle of the fifth axis is determined according to the included angle between the vector of the tool swing length in the tool position file and the corresponding projection, and the specific process comprises:

[0031] The projection of the tool position file vector of the machined workpiece in the machine tool XY direction is set as LW, and the vector of the tool swing length is set as (U xLT , U yLT , U zLT );

[0032] In the initial state of the machine tool, the fifth axis swings α°, and the tool swing length vector (UxLT , U yLT , U zLT ) is (LTsinα, 0, LTcosα), swing the fifth axis by -α°, then the tool swing vector (U xLT , U yLT , U zLT ) is (-LTsinα, 0, LTcosα);

[0033] Set the angle between U xLT and LW as λ, the calculation method of λ is:

[0034] When U x is positive, U xLT is positive, the angle λ between U xLT and LW is

[0035] When U x is positive, U xLT is negative, the angle λ between U xLT and LW is

[0036] When U x is negative, U xLT is positive, the angle λ between U xLT and LW is

[0037] When U x is negative, U xLT is negative, the angle λ between U xLT and LW is

[0038] Wherein, U x is obtained from the tool position vector file, and the swing direction of the fifth axis is determined according to the size of λ.

[0039] In the above technical solution, preferably, the rotation angle of the C-axis is calculated according to the value of the swing angle of the fifth axis, and the specific process comprises:

[0040] When U x is positive, U y is positive, and α is negative,

[0041] When U x is positive, U y is positive, and α is positive,

[0042] When U x is positive, U yis negative, and the value of a is negative,

[0043] When U x is positive, and the value of a is positive, y is negative, and the value of a is negative,

[0044] When U x is negative, and the value of a is positive, y is positive, and the value of a is negative,

[0045] When U x is negative, and the value of a is positive, y is positive, and the value of a is negative,

[0046] In the above technical solution, preferably, the fifth axis swing direction of the first tool contact point in the machining trajectory is calculated according to the rotation angles of the fifth axis and the C axis, in combination with the kinematics model, and the specific process comprises:

[0047] According to the swing angle a of the fifth axis and the swing angle β of the C axis, in combination with the kinematics model, the movement distance of each axis of the machine tool is calculated:

[0048]

[0049] Wherein, after the fifth axis swing direction of the first tool contact point is determined, the tool contact points of the subsequent machining trajectory are consistent with the fifth axis swing direction of the first tool contact point.

[0050] Compared with the prior art, the beneficial effects of the present application are: by constructing a kinematics model of the tool and the workpiece of the machine tool, the swing angles of the fifth axis and the C axis are calculated, and the machining trajectory is further calculated, which solves the problem of large C axis stroke caused by the single direction swing of the fifth axis of the machine tool in the existing machine tool post-processing calculation, improves the machining efficiency of the machine tool, and prolongs the service life of the swing angle milling head. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The flowchart of the post-processing method of the five-axis double-swing-angle machine tool based on the C axis disclosed by an embodiment of the present application is shown. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] The present invention will now be described in further detail with reference to the accompanying drawings:

[0054] like Figure 1 As shown, a post-processing method for a C-axis-based five-axis dual-swivel machine tool according to the present invention includes:

[0055] Based on the position and vector direction of the tool and workpiece corresponding to the machine tool type, determine the transformation matrix from the tool coordinate system to the workpiece coordinate system;

[0056] Construct a kinematic model of the corresponding machine tool based on the coordinate transformation matrix;

[0057] The movement distance of each motion axis of the machine tool is obtained by solving the kinematic model under the conditions of no RTCP compensation and with RTCP compensation.

[0058] The swing angle of the fifth axis is determined based on the angle between the vector of the tool swing length and the corresponding projection in the tool position file;

[0059] Calculate the rotation angle of the C-axis based on the value of the fifth axis swing angle;

[0060] Based on the rotation angles of the fifth axis and the C axis, the swing direction of the fifth axis at the first tool contact point in the machining trajectory is calculated using a kinematic model.

[0061] In this embodiment, by constructing a kinematic model of the machine tool's cutting tool and workpiece, the swing angles of the fifth axis and C-axis are calculated, and the machining trajectory is further calculated. This solves the problem of excessive C-axis travel caused by the fifth axis of the machine tool swinging only in one direction due to the existing post-processing calculation of the machine tool, thereby improving the machining efficiency of the machine tool and extending the service life of the swing milling head.

[0062] Specifically, the five-axis double-swivel type machine tool includes XYZAC or XYZBC motion forms. This embodiment takes the XYZBC type machine tool as an example to specifically explain the post-processing method of the five-axis machine tool.

[0063] In the above embodiments, preferably, the transformation matrix from the tool coordinate system to the workpiece coordinate system is determined according to the position and vector direction of the tool and workpiece corresponding to the machine tool type. The specific process includes:

[0064] Setting (P)x , P y , P z , U x , U y , U z ) is the position and vector direction of the tool position file CLS;

[0065] According to the transformation relationship between each adjacent coordinate system, the conversion matrix of the tool coordinate system to the workpiece coordinate system is determined as:

[0066] [u w 0] T = w T t [u t 0] T

[0067] [p w 0] T = w T t [p t 0] T

[0068] Wherein, u w , u t , p w , p t are the initial vector direction of the workpiece, the initial vector direction of the tool, the initial position coordinate of the workpiece, and the initial position coordinate of the tool, respectively; w T t is the coordinate transformation matrix from the tool end to the workpiece end.

[0069] In the above embodiment, preferably, a kinematic model of the corresponding form machine tool is constructed according to the coordinate conversion matrix, and the specific process includes:

[0070] The coordinate conversion matrix is multiplied to obtain the kinematic model of the five-axis linkage machine tool:

[0071]

[0072] Wherein, LT is the tool swing length, which is the distance from the fifth axis rotation center to the tool tip point, LBC is the Z direction distance from the fifth axis rotation center to the C axis rotation center, α is the swing angle of the fifth axis, β is the swing angle of the C axis, L x is the linear distance of the machine tool X axis movement, L y is the linear distance of the machine tool Y axis movement, and L z is the linear distance of the machine tool Z axis movement.

[0073] In the above embodiment, preferably, the kinematic model is solved to obtain the movement distance of each movement axis of the machine tool without RTCP compensation and with RTCP compensation, and the specific process comprises:

[0074] The kinematic model is solved to obtain the solution of each movement axis of the machine tool without RTCP compensation as follows:

[0075]

[0076] With RTCP compensation, the machine tool is compensated for the X, Y and Z axes by the numerical control system inside the machine tool, and the solution of each axis of the machine tool is as follows:

[0077]

[0078] Wherein, the value of α is the inverse cosine function, according to the function property, the domain is [-1, 1], the value range is [0, π], since α is the swing angle of B axis, the value of α calculated by inverse function is positive, which is reflected to the machine tool, that is, the swing angle of B axis is positive, that is, the swing angle of B axis cannot be negative if it is simply solved according to the kinematic model.

[0079] In combination with the above embodiment, preferably, the present application determines the swing angle of the fifth axis according to the included angle between the vector of tool swing length in the tool position file and the corresponding projection, and the specific process comprises:

[0080] The projection of the tool position file vector of the machined workpiece in the machine tool XY direction is set as LW, and the vector of tool swing length is set as (U xLT , U yLT , U zLT ), in the implementation process, when calculating the tool swing length vector, the swing length LT needs to be set as 1;

[0081] In the initial state of the machine tool, the fifth axis swings α°, and the tool swing length vector (U xLT , U yLT , U zLT ) is (LTsinα, 0, LTcosα), and the fifth axis swings-α°, and the tool swing length vector (U xLT , U yLT , U zLT ) is (-LTsinα, 0, LTcosα);

[0082] The included angle between U xLT and LW is set as λ, and the calculation method of λ is as follows:

[0083] When U x is positive and U xLT is positive, the included angle λ between U xLT and LW is

[0084] When U x is positive, U xLT is negative, U xLT is positive, the angle λ between U

[0085] When U x is negative, U xLT is positive, U xLT is positive, the angle λ between U

[0086] When U x is negative, U xLT is negative, U xLT is positive, the angle λ between U

[0087] Wherein, U x is obtained from the tool position vector file, and the swing direction of the fifth axis is determined according to the size of λ. The judgment basis for the swing of the B axis in the positive direction or the negative direction is the size of the λ angle. The absolute value of the λ angle is determined when the B axis swings α° and -α°, respectively. The case of the smaller absolute value of the λ angle is taken as the swing angle of the B axis.

[0088] In the above embodiment, preferably, the rotation angle of the C axis is calculated according to the value of the swing angle of the fifth axis, and the specific process includes:

[0089] When U x is positive, U y is positive, and α is negative,

[0090] When U x is positive, U y is positive, and α is positive,

[0091] When U x is positive, U y is negative, and α is negative,

[0092] When U x is positive, U y is negative, and α is positive,

[0093] When U x is negative, U y is positive, and α is negative,

[0094] When U xU is negative, U y U is positive, U

[0095] U is negative, U x U is negative, U y U is negative, U

[0096] U is negative, U x U is negative, U y U is negative, U

[0097] In the above embodiment, preferably, according to the rotation angle of the fifth axis and the C axis, the fifth axis swing direction of the first tool contact point in the machining track is calculated in combination with the kinematics model, and the specific process comprises:

[0098] According to the swing angle of the fifth axis and the swing angle of the C axis, the movement distance of each axis of the machine tool is calculated in combination with the kinematics model:

[0099]

[0100] It should be noted that when all tool contact points in a tool path are calculated, if there are both positive and negative values of U, it will cause a large range of swing of the B axis during machining, which may cause global interference during machining, thereby damaging the workpiece or the machine tool. Therefore, after the fifth axis (B axis) swing direction of the first tool contact point is determined, the tool contact points of the subsequent machining track are consistent with the B axis swing direction of the first tool contact point.

[0101] According to the post-processing method of the five-axis double-swing-angle machine tool based on the C axis disclosed in the above embodiment, in the implementation process, taking the XYZBC machine tool as an example, the CLS file of a tool contact point is (-20.8999, -34.1056, 15.0000, -0.4940321, -0.8061871, 0.3255682), wherein U x , U y , U z are -0.4940321, -0.8061871, and 0.3255682, respectively. According to the above calculation method, the value of the B axis is -71.036, and the value of the C axis is 58.484. If the traditional algorithm is used, the value of the B axis is positive 71.036, and the value of the C axis calculated is -121.516. It can be seen that the stroke of the C axis will be shortened by using the method proposed in the present application.

[0102] In addition, the post-processing solution of the XYZAC machine tool is similar to the calculation method of XYZBC above, and in the implementation process, the following formula is used for calculation:

[0103]

[0104] wherein γ is the swing angle of the A-axis of the machine tool.

[0105] The above only is the preferred embodiment of the present application, and is not used to limit the present application, for the person skilled in the art, the present application can have various changes and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A post-processing method of a C-axis-based five-axis double-angle machine tool, characterized by, The method comprises the following steps: According to the position and vector direction of the tool and the workpiece corresponding to the form of the machine tool, a conversion matrix of the tool coordinate system to the workpiece coordinate system is determined; According to the coordinate conversion matrix, a kinematics model of the corresponding form of machine tool is constructed; According to the kinematics model, the moving distances of each motion axis of the machine tool under the conditions of no RTCP compensation and RTCP compensation are solved; According to the angle between the vector of tool swing length in the tool position file and the corresponding projection, the swing angle of the fifth axis is determined, and the specific process comprises: setting the projection of the tool position file vector of the machined workpiece in the machine tool XY direction as LW, and setting the vector of the tool swing length as (U xLT , U yLT , U zLT ); In the initial state of the machine tool, the tool swing length vector when the fifth axis swings α° is set as (LTsinα, 0, LTcosα), and the tool swing length vector when the fifth axis swings -α° is set as (-LTsinα, 0, LTcosα); Set U xLT The angle between the LW is λ, and the corresponding angle λ is calculated in the case of the fifth axis swing α ° and the fifth axis swing - α ° respectively. The absolute values of the λ angles in the two cases are judged, and the swing angle of the fifth axis corresponding to the case with the smaller absolute value of the λ angle is taken as the swing angle of the fifth axis, and the swing direction of the fifth axis is determined accordingly; According to the value of the swing angle of the fifth axis, the rotation angle of the C-axis is calculated; According to the rotation angles of the fifth axis and the C-axis, the fifth-axis swing direction of the first tool contact point in the machining trajectory is calculated in combination with the kinematics model, wherein after the fifth-axis swing direction of the first tool contact point is determined, the fifth-axis swing directions of the subsequent tool contact points in the same tool path trajectory are consistent with the fifth-axis swing direction of the first tool contact point.

2. The post-processing method of a C-axis-based five-axis dual swing angle machine tool according to claim 1, characterized in that, The method comprises the following steps: Set (P x , P y , P z , U x , U y , U z ) as the position and vector direction of the tool position file CLS; According to the transformation relationship between each adjacent coordinate system, the conversion matrix of the tool coordinate system to the workpiece coordinate system is determined as follows: [u w 0] T = w T t [u t 0] T [p w 0] T = w T t [p t 0] T wherein u w , u t , p w , p t are the initial vector direction of the workpiece, the initial vector direction of the tool, the initial position coordinates of the workpiece, and the initial position coordinates of the tool, respectively; w T t is the coordinate transformation matrix from the tool end to the workpiece end.

3. The post-processing method of a C-axis-based five-axis dual swing angle machine tool according to claim 2, characterized in that, The method comprises the following steps: The coordinate conversion matrix is multiplied to obtain the kinematics model of the five-axis linkage machine tool: Wherein, LT is a tool swing length, the tool swing length is a distance from the fifth axis rotation center to the tool tip point, LBC is a Z direction distance from the fifth axis rotation center to the C axis rotation center, a is a swing angle of the fifth axis, β is a swing angle of the C axis, L x is a linear distance of machine tool X axis movement, L y is a linear distance of machine tool Y axis movement, L z is a linear distance of machine tool Z axis movement.

4. The post-processing method of a C-axis-based five-axis dual swing angle machine tool according to claim 3, characterized in that, The method comprises the following steps: The kinematics model is solved to obtain the solutions of each motion axis of the machine tool under the condition of no RTCP compensation as follows: Under the condition of RTCP compensation, the numerical control system inside the machine tool has compensated the X, Y and Z axes, so the solutions of each axis of the machine tool are as follows: Wherein, if the value of α is positive, the swing angles of the fifth axis of the machine tool are all positive.

5. The post-processing method of a C-axis-based five-axis dual swing angle machine tool according to claim 4, characterized in that, The method comprises the following steps: The projection of the tool position file vector of the machining workpiece in the machine tool XY direction is set as LW, and the vector of the tool swing length is set as (U xLT , U yLT , U zLT ); In the initial state of the machine tool, the fifth axis is swung by α°, then the tool swing length vector (U xLT , U yLT , U zLT ) is (LTsinα, 0, LTcosα), the fifth axis is swung by -α°, then the tool swing length vector (U xLT , U yLT , U zLT ) is (-LTsinα, 0, LTcosα); Set U xLT The angle between the LW is λ, and the calculation method of λ is: When U x is positive, U xLT is positive, U xLT the angle λ between L and LW is When U x takes a positive value, U xLT takes a negative value, U xLT the angle λ between L and LW is When U x is negative, U xLT is positive, U xLT the angle λ between L and W is When U x is negative, U xLT is negative, U xLT the angle λ between L and LW is wherein U x The swing direction of the fifth axis is determined according to the size of λ obtained from the tool position vector file.

6. The post-processing method of a C-axis-based five-axis dual swing angle machine tool according to claim 5, characterized in that, The method comprises the following steps: When U x is positive, U y is positive, and a is negative, When U x is positive, U y is positive, and a is positive, When U x is positive, U y is negative, and a is negative, When U x is positive, U y is negative, and a is positive, When U x is negative, U y is positive, and a is negative, When U x is negative, U y is positive, and a is positive, When U x is negative, U y is negative, and a is negative, When U x is negative, U y is negative and a is positive, 7. The post-processing method of a C-axis-based five-axis dual swing angle machine tool according to claim 6, characterized in that, The method comprises the following steps: According to the swing angle α of the fifth axis and the swing angle β of the C-axis, the moving distances of each axis of the machine tool are calculated in combination with the kinematics model: Wherein, after the fifth-axis swing direction of the first tool contact point is determined, the fifth-axis swing directions of the subsequent tool contact points in the machining trajectory are consistent with the fifth-axis swing direction of the first tool contact point.

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