A method for precision machining of parameter coordinates of five-axis composite CNC machine tools

Abstract

The invention provides a method for precision machining parameter coordinates of a five-axis composite numerical control machine tool, and the steps are as follows: establishing a model of a five-axis composite numerical control machine tool, the machine tool can realize the conversion from a horizontal-swing head turntable five-axis numerical control machine tool to a vertical-swing head turntable five-axis numerical control machine tool; selecting the form of the five-axis composite machine tool according to the characteristics of an involute helical surface; deriving the parameter coordinates of the five-axis composite numerical control machine tool according to the coincidence of a tool axis direction vector with a unit normal vector of the involute helical surface, and the relative motion relationship between a tool axis position vector and a position vector of the involute helical surface; constructing an interface for five-axis free milling of an involute helical surface; the method can realize precision machining of parameter coordinates of a five-axis composite numerical control machine tool for an involute helical surface, and improve stability.

Description

Technical Field

[0001] The invention relates to the field of five-axis CNC machine tool coordinate analysis, and in particular to a five-axis composite CNC machine tool parameter coordinate precision machining method. Background Art

[0002] The five-axis compound CNC machine tool is composed of three translation axes and two rotary axes. Different types of five-axis compound CNC machine tools can be formed through different combinations of translation axes and rotary axes. In the prior art, the processing method for the parameter coordinates of the five-axis compound CNC machine tool generally processes the surface model in three-dimensional software and derives the relevant parameter coordinates and processing paths.

[0003] In the current three-dimensional software for precision machining of parameter coordinates of five-axis composite CNC machine tools, since a certain degree of error will be generated during three-dimensional modeling of complex surfaces, the obtained parameter coordinates will have a large deviation from the actual situation, the accuracy will be reduced, and it is easy to cause the machine tool to vibrate during the machining process. The present invention is aimed at a five-axis composite CNC machine tool, and proposes a method for precision machining of parameter coordinates of a five-axis composite CNC machine tool, which can obtain precise parameter coordinates of a five-axis composite CNC machine tool, so that the accuracy of the machined surface is improved. Summary of the invention

[0004] The purpose of the present invention is to provide a five-axis composite CNC machine tool parameter coordinate precision machining method, which can realize the compensation of the five-axis tool length and the position vector of the workpiece in the machine tool coordinate system in the CNC machining program. In addition, the method can improve the machining accuracy of the five-axis composite CNC machine tool.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A five-axis composite CNC machine tool parameter coordinate precision machining method, the method comprising the following steps:

[0007] Step 1: Establish a three-dimensional model of the five-axis compound CNC machine tool and analyze the structural characteristics of the machine tool through the coordinate system consolidated by each axis;

[0008] Step 2: According to the involute helical surface equation of the gear to be processed, select the type of the five-axis compound CNC machine tool and determine whether the five-axis compound CNC machine tool is vertical or horizontal;

[0009] Step 3: Use a photoelectric edge finder to measure the distance from the tool tip to the A-axis rotation center of the five-axis CNC machine tool through the rotation and translation of the swing head;

[0010] Step 4: Based on the steps 2 and 3, under the initial coordinates of the CNC machine tool, the relationship between the direction vector of the tool axis and the unit normal vector of the involute helical surface is constructed to obtain the rotation amount of the rotation axis of the five-axis compound machine tool; based on the relative motion relationship between the position vector of the tool axis and the position vector of the involute helical surface, the displacement amount of the linear axis of the five-axis compound machine tool is obtained;

[0011] Step 5: Based on the above steps, substitute the involute helical surface equation into the displacement equations of the linear axis and rotary axis of the five-axis compound machine tool, determine the relationship between the involute helical surface parameter coordinates u, θ and the displacement of each axis, and develop the five-axis free milling involute helical surface interface based on the QT platform.

[0012] In the step one, the five-axis compound CNC machine tool established is a compound machine tool of a horizontal-swing head turntable five-axis CNC machine tool and a vertical-swing head turntable five-axis CNC machine tool; in actual operation, the five-axis compound machine tool uses the horizontal-swing head turntable five-axis CNC machine tool as the default state. If a vertical-swing head turntable five-axis CNC machine tool is needed, it is only necessary to rotate the swing head counterclockwise 90° around the A-axis fixedly connected to the tool coordinate system to achieve the conversion from the horizontal-swing head turntable five-axis CNC machine tool to the vertical-swing head turntable five-axis CNC machine tool.

[0013] In the step 2, without considering the three-dimensional model of the involute helical surface, the characteristics of the equation of the involute helical surface to be processed are analyzed, thereby performing preliminary processing on the five-axis compound CNC machine tool, selecting the form of the five-axis compound CNC machine tool, and determining whether the five-axis compound machine tool is a vertical-swing head turntable five-axis CNC machine tool or a horizontal-swing head turntable five-axis CNC machine tool.

[0014] In the step three, a photoelectric edge finder is used. After the pendulum head rotates 90° clockwise around the A-axis fixed to the tool coordinate system, it moves downward along the z-axis until the tool head contacts the workpiece. The distance from the tool tip to the A-axis rotation center of the five-axis compound CNC machine tool to be measured is the pendulum length: pendulum length = relative coordinate system z value + measuring ball radius.

[0015] In the step four, according to the form of the five-axis compound CNC machine tool selected in step two, horizontal or vertical, and combined with the pendulum length measured in step three, the tool axis vector and the normal vector of any point on the involute spiral surface should coincide, and the relative motion relationship between the tool axis position vector and the involute spiral surface position vector is used to derive the coordinate displacement calculation formula of each axis of the involute spiral on the five-axis compound CNC machine tool.

[0016] In the step five, the displacement expression of the involute helix obtained in step four under the five-axis compound CNC machine tool is analyzed, and an interface for five-axis free milling of the involute helix surface is constructed in QT. The interface is clear and takes the form of the five-axis compound CNC machine tool, the parameters of the helical surface to be processed, the tool swing length, and the direction of the two rotating axes as input; and the displacement of each rotating axis and the linear axis as output.

[0017] Step 1: Establish a three-dimensional model of the five-axis compound CNC machine tool, and analyze the structural characteristics of the machine tool through the coordinate system of each axis; on the five-axis compound CNC machine tool, establish the workpiece coordinate system (X w ,Y w ,Z w ), tool coordinate system (X t ,Y t ,Z t ), and the machining coordinate system (X m ,Y m ,Z m ), wherein the rotation axis C is fixedly connected and coincident with the z-axis of the workpiece coordinate system, the rotation axis A is fixedly connected and coincident with the x-axis of the tool coordinate system, and the initial positions of the workpiece coordinate system and the machining coordinate system coincide;

[0018] Step 2: According to the equation of the involute helical surface to be processed, select the form of the five-axis compound CNC machine tool and determine whether the five-axis compound CNC machine tool is vertical or horizontal;

[0019] Step 3: Use the photoelectric edge finder to measure the distance from the tool tip of the five-axis CNC machine tool to the A-axis rotation center through the rotation and translation of the pendulum head; under the vertical definition of the machine tool, the pendulum head rotates 90° around the A-axis to the A0 position, and the relative coordinates are cleared at this time. The handwheel block is used to make the edge finder probe (the probe ball radius is defined as r) move a distance a along the z-axis direction until it just touches the upper surface of the workpiece. At this time, the pendulum length calculation formula is obtained:

[0020] L=a+r (1)

[0021] Step 4: Based on the steps 2 and 3, under the initial coordinates of the CNC machine tool, the relationship between the direction vector of the tool axis and the unit normal vector of the involute helical surface is constructed to obtain the displacement of the rotation axis of the five-axis compound machine tool; based on the relative motion relationship between the position vector of the tool axis and the position vector of the involute helical surface, the displacement of the linear axis of the five-axis compound machine tool is obtained;

[0022] The equation of the involute helicoid to be processed F(u,θ) is as follows:

[0023]

[0024] According to the given involute helical surface equation, the unit normal vector of a point on the involute helical surface is solved. By utilizing the coincidence of the normal vector on the tool and the tool axis vector, and the relative motion relationship between the tool axis position vector and the involute helical surface position vector, the displacement of the rotary axis and the linear axis of the five-axis compound machine tool is obtained.

[0025] The turntable rotates forward θ around the fixed axis C C In the case of, let the unit normal vector of a point on the surface F(u,θ) be Then the transformation equation of the unit normal vector of a point on the surface in the workpiece coordinate system is as follows:

[0026]

[0027] Rotate the tool coordinate system in the opposite direction around the fixed axis A by θ A In the case of , the unit vector of the tool axis is Then the transformation equation of the tool axis unit vector in the workpiece coordinate system is as follows:

[0028]

[0029] Rotate the turntable θ A The surface normal unit vector after the angle is related to the swing head swing θ C The angle tool axis vector coincides, and the equation is obtained:

[0030] [n x1 n y1 n z1 ] T =[u x1 u y1 u z1 ] T (5)

[0031] Similarly, according to the relative motion relationship between the tool axis position vector and the involute helical surface position vector, the workpiece coordinate system is stationary, and the tool coordinate origin is stationary in the X, Y, and Z axis directions. According to the relative motion between the two, the actual moving distance of each axis in the X, Y, and Z directions in the machine tool coordinate system [s x s y s z ] can be obtained:

[0032]

[0033] The calculation results are as follows:

[0034]

[0035] Step 5: Based on the above steps, substitute the involute helical surface equation into the displacement equation of the linear axis and rotary axis of the five-axis compound machine tool, determine the relationship between the parameter coordinates of the involute helical surface and the displacement of each axis, and develop the interface of the five-axis free milling involute helical surface based on the platform.

[0036] It can be seen from the above invention technical scheme that this method can not only realize the precision machining of the five-axis composite CNC machine tool parameter coordinates, but also realize the compensation of the five-axis tool length and the position vector of the workpiece in the machine tool coordinate system in the CNC machining program. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the parameter coordinate precision machining analysis of the five-axis composite CNC machine tool of the present invention;

[0038] Figure 2 It is a schematic diagram of a swing head-turntable five-axis compound CNC machine tool of the present invention;

[0039] Figure 3 It is a schematic diagram of pendulum length measurement of the five-axis compound CNC machine tool of the present invention;

[0040] Figure 4 It is a schematic diagram of the involute helix of the present invention;

[0041] Figure 5 This is the interface result diagram of the five-axis free milling of the involute helical surface of the present invention. DETAILED DESCRIPTION

[0042] In view of this, the present invention provides a method for precision machining of parameter coordinates of a five-axis composite CNC machine tool. The method establishes a five-axis composite CNC machine tool, which has two machine tool forms: a horizontal-swing head turntable five-axis CNC machine tool and a vertical-swing head turntable five-axis CNC machine tool, derives the parameter coordinate transformation of the involute helical surface under the machine tool, and constructs an interface for five-axis free milling of the involute helical surface.

[0043] The objective of the present invention is achieved through the following technical solutions:

[0044] A five-axis composite CNC machine tool parameter coordinate precision machining method, the method comprising the following steps

[0045] Step 1: Take the five-axis compound CNC machine tool as the research object, establish a three-dimensional model of the five-axis compound CNC machine tool, and analyze the structural characteristics of the machine tool through the coordinate system consolidated by each axis. On the five-axis compound CNC machine tool, establish the workpiece coordinate system (X w ,Y w ,Z w ), tool coordinate system (X t ,Y t ,Z t ), and the machining coordinate system (Xm ,Y m ,Z m ), wherein the rotation axis C is fixedly connected and coincident with the z-axis of the workpiece coordinate system, the rotation axis A is fixedly connected and coincident with the x-axis of the tool coordinate system, and the initial positions of the workpiece coordinate system and the machining coordinate system coincide;

[0046] Step 2: According to the equation of the involute helicoid, it is preliminarily processed to select the form of the five-axis compound CNC machine tool, that is, to determine whether the five-axis compound machine tool is a vertical-swing head-turntable five-axis CNC machine tool or a horizontal-swing head-turntable five-axis CNC machine tool.

[0047] Step 3: Before deriving the calculation formula for the coordinate displacement of each axis on the five-axis composite CNC machine tool, it is necessary to measure the tool pendulum length L. Under the vertical definition of the machine tool, the pendulum head rotates 90° around the A axis to the A0 position, and the relative coordinates are cleared at this time. The handwheel block is used to make the edge finder probe (the radius of the probe ball is defined as r) move a distance a along the z-axis direction until it just touches the upper surface of the workpiece. At this time, the pendulum length calculation formula is obtained:

[0048] L=a+r (1)

[0049] Step 4: Taking the horizontal-swing head rotary table five-axis CNC machine tool in the five-axis compound CNC machine tool as an example, derive the calculation formula for the coordinate displacement of each axis on the five-axis compound CNC machine tool. When using the horizontal-swing head rotary table CNC machine tool for processing, during the processing process, the tool axis vector and the normal vector of any point on the processing surface should coincide, and the displacement of the rotation axis of the five-axis compound machine tool is obtained; then, based on the relative motion relationship between the tool axis position vector and the involute helical surface position vector, the displacement of the linear axis of the five-axis compound machine tool is obtained.

[0050] The equation of the involute helicoid to be processed F(u,θ) is as follows:

[0051]

[0052] According to the given involute helical surface equation, the unit normal vector of a point on the involute helical surface is solved. By utilizing the coincidence of the normal vector on the tool and the tool axis vector, and the relative motion relationship between the tool axis position vector and the involute helical surface position vector, the displacement of the rotary axis and the linear axis of the five-axis compound machine tool is obtained.

[0053] The turntable rotates forward θ around the fixed axis C C In the case of, let the unit normal vector of a point on the surface F(u,θ) be Then the transformation equation of the unit normal vector of a point on the surface in the workpiece coordinate system is as follows:

[0054]

[0055] Rotate the tool coordinate system in the opposite direction around the fixed axis A by θ AIn the case of , the unit vector of the tool axis is Then the transformation equation of the tool axis unit vector in the workpiece coordinate system is as follows:

[0056]

[0057] Rotate the turntable θ A The surface normal unit vector after the angle is related to the swing head swing θ C The angle tool axis vector coincides, and the equation is obtained:

[0058] [n x1 n y1 n z1 ] T =[u x1 u y1 u z1 ] T (5)

[0059] Similarly, according to the relative motion relationship between the tool axis position vector and the involute helical surface position vector, the workpiece coordinate system is stationary, and the tool coordinate origin is stationary in the X, Y, and Z axis directions. According to the relative motion between the two, the actual moving distance of each axis in the X, Y, and Z directions in the machine tool coordinate system [s x s y s z ] can be obtained:

[0060]

[0061] The calculation results are as follows:

[0062]

[0063] Step 5, according to the calculation result of the coordinate axis of the five-axis composite CNC machine tool for the involute helical surface described in step 4, it is characterized in that the specific steps of step 5 are: design and develop the interface of the five-axis free milling of the involute helical surface, perform preliminary processing on the five-axis composite CNC machine tool according to the requirements of the involute helical surface, judge the form of the five-axis composite CNC machine tool, whether it is a vertical swing head-turntable five-axis CNC machine tool or a horizontal swing head-turntable five-axis CNC machine tool, and after the preliminary processing is completed, proceed to the next step; according to the requirements of the involute helical surface processing, select the rotation direction of the fixed axis C and the fixed axis A, counterclockwise rotation is positive (select "+"), and clockwise rotation is negative (select "-"). In the application interface, the form of the five-axis composite CNC machine tool, the parameters of the helical surface to be processed, the tool swing length, and the direction of the two rotating axes are used as input quantities, and the displacement of each rotating axis and the linear axis is used as output quantity.

[0064] The beneficial effects of the present invention are as follows: in a five-axis compound CNC machine tool, the machine tool includes a horizontal-swing head rotary table machine tool and a vertical-swing head rotary table machine tool; and without considering a three-dimensional model, the mathematical theoretical equation of the involute helical surface is used to deduce the displacement of each axis in the five-axis compound machine tool; and an interface for five-axis free milling of the involute helical surface is constructed.

Claims

1. A five-axis composite CNC machine tool parameter coordinate precision machining method, characterized in that: The following steps are involved: Step 1: Establish a three-dimensional model of the five-axis compound CNC machine tool and analyze the structural characteristics of the machine tool through the coordinate system consolidated by each axis; Step 2: According to the involute helical surface equation of the gear to be processed, select the type of the five-axis compound CNC machine tool and determine whether the five-axis compound CNC machine tool is vertical or horizontal; Step 3: Use a photoelectric edge finder to measure the distance from the tool tip to the A-axis rotation center of the five-axis CNC machine tool through the rotation and translation of the swing head; Step 4: Based on the steps 2 and 3, under the initial coordinates of the CNC machine tool, the relationship between the direction vector of the tool axis and the unit normal vector of the involute helical surface is constructed to obtain the rotation amount of the rotation axis of the five-axis compound machine tool; based on the relative motion relationship between the position vector of the tool axis and the position vector of the involute helical surface, the displacement amount of the linear axis of the five-axis compound machine tool is obtained; Step 5: Based on the above steps, substitute the involute helicoid equation into the displacement equation of the linear axis and the rotary axis of the five-axis compound machine tool, determine the relationship between the involute helicoid parameter coordinates u, θ and the displacement of each axis, and develop a five-axis free milling involute helicoid interface based on the QT platform; In the step 1, the five-axis compound CNC machine tool established is a compound machine tool of a horizontal-swing head turntable five-axis CNC machine tool and a vertical-swing head turntable five-axis CNC machine tool; in actual operation, the five-axis compound machine tool uses the horizontal-swing head turntable five-axis CNC machine tool as the default state. If a vertical -Swing head turntable five-axis CNC machine tool, it is only necessary to rotate the swing head 90° counterclockwise around the A axis fixed to the tool coordinate system to realize the conversion from the horizontal-swing head turntable five-axis CNC machine tool to the vertical-swing head turntable five-axis CNC machine tool; in the step 2, without considering the three-dimensional model of the involute helical surface, the characteristics of the involute helical surface equation to be processed are analyzed, thereby preliminarily processing the five-axis compound CNC machine tool, selecting the form of the five-axis compound CNC machine tool, and determining whether the five-axis compound machine tool is a vertical-swing head turntable five-axis CNC machine tool or a horizontal-swing head turntable five-axis CNC machine tool. Control machine tool; in the step three, use the photoelectric edge finder, after the pendulum head rotates 90° clockwise around the A-axis fixed to the tool coordinate system, it moves downward along the z-axis until the tool head contacts the workpiece, then the distance from the tool tip to the A-axis rotation center of the five-axis compound CNC machine tool to be measured is the pendulum length: pendulum length = relative coordinate system z value + measuring ball radius; in the step four, according to the form of the five-axis compound CNC machine tool selected in step two, horizontal or vertical, and combined with the pendulum length measured in step three, the tool axis vector and the normal vector of any point on the involute spiral surface should coincide, and the tool The relative motion relationship between the axis position vector and the involute helical surface position vector is used to derive the calculation formula for the coordinate displacement of each axis of the involute helix on the five-axis compound CNC machine tool; in the step five, the displacement expression of the involute helix obtained in step four on the five-axis compound CNC machine tool is analyzed, and an interface for five-axis free milling of the involute helical surface is constructed in QT. The interface is clear and takes the form of the five-axis compound CNC machine tool, the parameters of the helical surface to be processed, the tool swing length, and the directions of the two rotating axes as input; and the displacement of each rotating axis and the linear axis as output.

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