A workpiece pretreatment method for improving the turning accuracy of curved surface components

Abstract

The present invention discloses a workpiece pretreatment method for improving the turning accuracy of curved surface components. First, the key issues affecting the component processing accuracy are determined based on the turning process of the curved surface component. Secondly, the cutting edge profile curve of the tool used is constructed. Then, an analytical model describing the time-varying cutting contact state of the tool is established to determine the cutting position area where large cutting edge contact length, overlapping cutting contact point movement area, and chip "slide-stop-slide" phenomenon occur. Finally, based on this, the curved surface component material is partially removed, thereby completing the pretreatment operation of the curved surface component. The present invention solves the problems of continuous strip chips, increased cutting edge contact length, overlapping cutting contact point movement area, and chip "slide-stop-slide" that occur during the turning process of curved surface components. It effectively improves the service life of the tool and the processing accuracy of the component. At the same time, it does not require any auxiliary devices, saves production costs, and avoids interference problems that may occur when using auxiliary devices for chip breaking.

Description

Technical Field

[0001] The present invention belongs to the technical field of turning processing of curved surface components, and in particular relates to a workpiece pretreatment method for improving the turning processing accuracy of curved surface components. Background Art

[0002] Currently, high-performance components, such as aviation structural parts, engine cases, and blisks, are widely used in aerospace, defense, and military industries. These components are often made from difficult-to-machine materials such as high-temperature alloys, high-strength steels, and titanium alloys. The machining process results in high material removal, intense mechanical and thermal reactions in the contact area, rapid tool wear, high system vibration, and difficulty in chip breaking. These issues significantly restrict the forming accuracy, surface quality, and cutting efficiency of these high-performance components.

[0003] During the turning process of difficult-to-machine materials, the problem of poor chip breaking is particularly prominent. The strip-shaped chips generated by turning have high temperature and fast flow rate. They are entrained or entangled on the tool, workpiece and machine tool parts, which will not only damage the machined surface, but also worsen the heat dissipation conditions in the cutting area and aggravate tool wear. For this reason, chip breaker chip breaking, ultrasonic vibration chip breaking and high-pressure cooling chip breaking are often used in actual processing to accelerate the breaking of strip-shaped chips. Invention patent CN115156576A provides an adjustable chip breaking and cooling turning tool. The additional device is installed on the turning tool arbor. During turning, the servo motor drives the chip breaker to perform the chip breaking operation through the transmission mechanism; Invention patent CN115673864A provides a chip breaking method for ultrasonic cutting of honeycomb cores, which uses the ultrasonic cutting effect of the tool's return stroke to achieve timely cutting of large-area flaky chips; Invention patent CN115178760A provides a turret high-pressure water outlet device for chip breaking cutting, which solves the chip breaking problem of turning while improving the service life of the water outlet device. Unlike the above-mentioned scheme, the device and method provided by invention patent CN111390205A mainly act on the workpiece to be processed, using an added high-energy laser beam module to vaporize the material of shaft parts, and then form grooves on the surface of the workpiece. When the tool cuts to the pre-processing position of the workpiece, chip fracture can be automatically achieved.

[0004] The current technical solution mainly solves the chip breaking problem of difficult-to-machine materials by adding auxiliary devices to the turning system. However, the additional devices not only increase production costs, but also reduce the movement space of the tool, making it easy for interference to occur during the cutting process, and damaging the workpiece or the auxiliary devices. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a workpiece pretreatment method for improving the turning accuracy of curved components, aiming to solve problems such as chip breaking during turning of curved components without adding auxiliary devices, and to achieve high-precision processing of curved components made of difficult-to-process materials.

[0006] The technical solution of the present invention:

[0007] A workpiece pretreatment method for improving the turning accuracy of curved surface components comprises the following steps:

[0008] Step 1: Analyze the problems to be solved during the turning process of curved surface components. Since the cutting point of the tool rotates around the workpiece contour, the turning state of the curved surface component is posture-related, and the tool-workpiece contact area also changes during this process. Among them, the starting point of the contact area PF i The moving trajectory is [PF1,PF2,…,PF n ], contact area end point PE i The moving trajectory is [PE1,PE2,…,PE n ], there is an overlapping area between the two contact areas, and the tool wear problem is most serious in this overlapping area; define PF i With PE i The straight-line distance between the two edges is the cutting edge contact length, which varies with the tool posture. In addition, the cutting force and thermal load increase significantly in the long cutting edge action area, which also aggravates the tool wear problem. In the low-speed cutting area of ​​the curved surface component, the chip exhibits a "slide-stop-slide" phenomenon as it slides along the rake face, resulting in a violent periodic fluctuation in the cutting force. This not only deteriorates the machining quality of the curved surface component, but also impacts the tool and accelerates the damage of the turning tool cutting edge. The above analysis shows that in addition to the chip breaking problem, the turning process of the curved surface component also encounters the problems of large cutting edge contact length, overlapping cutting contact point movement areas, and chip "slide-stop-slide". These problems need to be properly solved through workpiece pretreatment methods.

[0009] Step 2: Parametric characterization of the tool cutting edge; using an optical microscope to obtain the two-dimensional coordinates of the main cutting edge, the secondary cutting edge, and the part of the profile value points on the tool tip arc edge, and using a cubic non-uniform rational B-spline to construct the tool cutting edge profile curve passing through the above profile value points;

[0010] Step 3: Time-varying contact state analysis related to tool posture; First, adjust the initial posture of the tool. In the XOY coordinate plane, the tool tip arc is tangent to the upper end face of the curved flange, and the angle between the tool main cutting edge and the Y axis is The straight-line distance D between the center of the turning tool tip arc and the center of rotation of the curved surface component is R+r-dep; wherein, the X-axis is located in the plane where the lower end face of the curved surface component flange is located, the Y-axis coincides with the axis of rotation of the curved surface component, the origin of the coordinate system O coincides with the center of rotation of the curved surface component, the radius of the turning tool tip arc is represented by r, the outer contour diameter of the surface to be machined is represented by R, and the cutting depth is represented by dep; then, the tool contact area is determined based on the relative position between the curved surface component and the turning tool cutting edge contour, wherein the intersection of the tool main cutting edge and the surface to be machined is the starting point of the contact area, where the tool main groove wear is prone to occur, and the intersection of the tool secondary cutting edge and the machined surface is the end point of the contact area, where the tool secondary groove wear is prone to occur, and the straight-line distance between the above two points is defined as the cutting edge contact length; finally, the tool motion trajectory is discretized, and the tool contact state at each discrete tool position point is traversed and calculated to understand the change law of the tool contact area and contact length during the turning process of the curved surface component;

[0011] Step 4: Based on the cutting test results of the material to be processed, the influence of cutting speed on the chip "slide-stop-slide" phenomenon is evaluated, and the critical cutting speed for the above phenomenon to occur is determined as V min ;

[0012] Step 5: Define the angle between the line connecting the center of rotation of the curved surface component and the center of the arc edge of the tool and the X axis as the rotation angle θ i , during the turning process of curved components, the rotation angle θ i The range of variation is [θ1,θ n ]; According to the tool contact state analysis method described in step 2, the corresponding corner area when the cutting edge contact length increases is determined to be [θ1,θ2]; During the processing of curved surface components, the moving area of ​​the starting point of the contact area on the cutting edge overlaps with the moving area of ​​the end point of the contact area on the cutting edge. According to the tool contact state analysis method described in step 2, the corresponding corner area when the contact point moving area overlaps is determined to be [θ3,θ n ]; According to the cutting test results of the material to be processed, the critical cutting speed when the "slip-stop-slip" phenomenon occurs is determined to be V min , that is, the turning speed of the curved component is higher than V min When the “slip-stop-slip” phenomenon disappears, under the cutting condition of constant speed Sp, the angle region corresponding to the phenomenon of the curved surface component is determined to be [θ4,θ n ]; According to the above calculation results, the turning tool used in the current process stage is used to complete the pre-removal operation of part of the material on the curved surface component; Among them, the corner area [θ1,θ2] and [θ4,θ n ] is completely removed from the curved surface component, and the material removal depth is Rdep; three grooves are prefabricated in the corner area [θ2,θ3], and the corresponding corner intervals are and The material removal depth of the groove structure is Rdep; two grooves are prefabricated in the corner area [θ3,θ4], and the corresponding corner intervals are and The material removal depth of the groove structure is Rdep;

[0013] Step 6. After completing the pre-processing operation of the curved surface component, unload the curved surface component and let it stand; then replace the cutting tool, adjust the cutting parameters and re-clamp the curved surface component, and finally complete the allowance removal operation in the precision machining stage of the curved surface component according to the processing requirements.

[0014] Beneficial effects of the present invention: The present invention is aimed at the turning process of curved surface components, establishes an analytical model for describing the time-varying cutting contact state of the tool, determines the cutting position area where large cutting edge contact length, overlapping cutting contact point moving area and chip "slide-stop-slide" phenomenon occur, and partially removes the curved surface component material accordingly. This not only solves the turning chip breaking problem that occurs in the subsequent process stage, but also solves the problems of increased cutting edge contact length, overlapping cutting contact point moving area and chip "slide-stop-slide", effectively improving the service life of the turning tool and the processing accuracy of the curved surface components. At the same time, no additional devices are required, saving production costs and avoiding interference problems that may occur when using additional devices for chip breaking. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the turning process of curved components.

[0016] Figure 2 It is the cutting edge profile of the turning tool.

[0017] Figure 3 This is a diagram of the tool contact point changes during the turning process of curved surface components.

[0018] Figure 4 This is a graph showing the change in tool contact length during the turning process of curved components.

[0019] Figure 5 (a) is a schematic diagram of the structure of the curved surface component after pretreatment;

[0020] Figure 5 (b) is a diagram showing the outer diameter changes at different corner positions of the curved surface component after pretreatment. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the accompanying drawings and in conjunction with specific embodiments:

[0022] Taking the turning process of a pure iron curved component with a flange as an example, after the current process stage, the inner diameter of the curved component is 120.3mm, the outer diameter of the curved component is 122.8mm, the flange length is 20mm, and the thickness is 10mm. The turning tool insert model used in the subsequent process stage is DCGT11T302-KC5010, the cutting depth is 0.05mm, the tool feed is 0.1mm / r, and the spindle speed is Sp = 900rpm. To improve the turning accuracy of the curved component, a workpiece pretreatment method is proposed, which specifically includes the following steps:

[0023] Step 1: Analyze the problems to be solved during the turning process of curved surface components. Since the cutting point of the tool rotates around the workpiece contour, the turning state of the curved surface component is posture-related, and the tool-workpiece contact area also changes during this process. Figure 1 As shown, the contact area starting point PF i The moving trajectory is [PF1,PF2,…,PF n ], contact area end point PE i The moving trajectory is [PE1,PE2,…,PE n ], there is a position overlap between the two contact areas, and the tool wear problem is most serious in this overlapping area; define PF i With PE i The straight-line distance between the two edges is the cutting edge contact length, which varies with the tool posture. In addition, the cutting force and thermal load increase significantly in the long cutting edge action area, which also aggravates the tool wear problem. In the low-speed cutting area of ​​the curved surface component, the chip exhibits a "slide-stop-slide" phenomenon as it slides along the rake face, resulting in a violent periodic fluctuation in the cutting force during the cutting process. This not only deteriorates the machining quality of the curved surface component, but also impacts the tool and accelerates the damage of the turning tool cutting edge. The above analysis shows that in addition to the chip breaking problem, the turning process of the curved surface component also presents the problem of large cutting edge contact length, overlapping of the cutting contact point movement area, and chip "slide-stop-slide" problem. These problems need to be properly solved through workpiece pretreatment methods.

[0024] Step 2: Parametric characterization of the tool cutting edge; use an optical microscope to obtain the two-dimensional coordinates of the main cutting edge, secondary cutting edge and some of the profile points on the tool tip arc edge, and use cubic non-uniform rational B-spline to construct the tool cutting edge profile curve passing through the above profile points. The specific results are as follows Figure 2 As shown;

[0025] Step 3: Analysis of the time-varying contact state associated with tool position. First, adjust the tool's initial position. In the XOY coordinate plane, the tool tip arc is tangent to the upper end face of the curved flange. The angle between the tool's main cutting edge and the Y axis is 12.5°. The straight-line distance between the center of the tool tip arc and the center of rotation of the curved component is D = R + r - dep. In this example, the X axis lies in the plane of the lower end face of the curved component flange, the Y axis coincides with the axis of rotation of the curved component, and the coordinate system origin O coincides with the center of rotation of the curved component. The tool tip arc radius r = 0.2 mm, the outer contour radius of the machined surface is R = 122.8 mm, and the cutting depth dep = 0. 05mm, from which D = 122.95mm can be calculated; secondly, the tool contact area is determined based on the relative position between the curved surface component and the turning tool cutting edge contour. The intersection of the tool's main cutting edge and the surface to be machined is the starting point of the contact area, where the tool's main groove wear is prone to occur; the intersection of the tool's secondary cutting edge and the machined surface is the end point of the contact area, where the tool's secondary groove wear is prone to occur. The straight-line distance between the above two points is defined as the cutting edge contact length; finally, the tool motion trajectory is discretized, and the tool contact state at each discrete tool position is traversed and calculated to understand the changing pattern of the tool contact area and contact length during the turning process of the curved surface component; Figure 3 This is the tool contact point change diagram during the turning process of curved surface components. Figure 4 This is the tool contact length variation diagram during the turning process of curved surface components;

[0026] Step 4: Based on the cutting test results of the material to be processed, the influence of cutting speed on the chip "slide-stop-slide" phenomenon is evaluated, and the critical cutting speed for the above phenomenon to occur is determined as V min =60m / min;

[0027] Step 5: Complete the pre-processing operation of the curved surface component based on the analysis results; define the angle between the line between the rotation center of the curved surface component and the center of the tool arc edge and the X axis as the rotation angle θ i , calculate the corresponding corner area when the cutting edge contact length increases, the cutting contact point movement area overlaps, and the "slide-stop-slide" phenomenon occurs; among them, the corresponding corner area when the large cutting edge contact length problem occurs is [θ1,θ2], and the corresponding corner area when the cutting contact point movement process overlaps is [θ3,θ n ], the corresponding turning angle area when the “slip-stop-slip” phenomenon occurs is [θ4,θ n ]; In this example, θ1 = 4.67°, θ2 = 10°, θ3 = 62°, θ4 = 80.04°, θ n =90°; then, the turning tool used in the current process stage is used to complete the pre-removal operation of part of the material on the curved surface component. The geometric structure diagram of the curved surface component after pre-processing is shown as follows Figure 5As shown in (a); the materials of the curved components corresponding to the corner areas [4.67°, 10°] and [80.04°, 90°] are all removed, and the material removal depth is Rdep = 0.35 mm; three grooves are prefabricated in the corner area [10°, 62°], and the corresponding corner intervals are and Two grooves are prefabricated in the corner area [62°, 80.04°], and the corresponding corner intervals are and In this instance,

[0028] The outer diameter of the curved surface component at different corner positions after pretreatment is as follows: Figure 5 (b)

[0029] Step 6. After completing the pre-processing operation of the curved surface component, unload the curved surface component and let it stand; then replace the cutting tool, adjust the cutting parameters and re-clamp the curved surface component, and finally complete the allowance removal operation in the precision machining stage of the curved surface component according to the processing requirements.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A workpiece pretreatment method for improving the turning accuracy of curved surface components, characterized in that: The following steps are involved: Step 1: Parametric characterization of the tool cutting edge; Obtain the two-dimensional coordinates of the main cutting edge, the secondary cutting edge, and the part of the profile value points on the tool nose arc edge, and use cubic non-uniform rational B-spline to construct the tool cutting edge profile curve passing through the above profile value points; Step 2: Analysis of time-varying contact state related to tool posture; First, adjust the initial position of the tool. In the XOY coordinate plane, the tool tip arc is tangent to the upper end face of the curved component flange. The flange thickness is T, and the angle between the tool main cutting edge and the Y axis is The straight-line distance D between the arc center of the turning tool tip and the rotation center of the curved component is R+r-dep; wherein, the X-axis is located in the plane where the lower end face of the curved component flange is located, the Y-axis coincides with the rotation axis of the curved component, the origin of the coordinate system O coincides with the rotation center of the curved component, the arc radius of the turning tool tip is represented by r, the outer contour diameter of the surface to be machined is represented by R, and the cutting depth is represented by dep; then, the tool contact area is determined based on the relative position between the curved component and the contour of the turning tool cutting edge, wherein the intersection of the tool main cutting edge and the surface to be machined is the starting point of the contact area, where the tool main groove wear is prone to occur, and the intersection of the tool secondary cutting edge and the machined surface is the end point of the contact area, where the tool secondary groove wear is prone to occur, and the straight-line distance between the starting point and the end point of the contact area is defined as the cutting edge contact length; finally, the tool motion trajectory is discretized, and the cutting contact state of the tool at each discrete tool position is traversed and calculated to understand the change law of the tool contact area and the cutting edge contact length during the turning process of the curved component; Step 3: Based on the cutting test results of the material to be processed, the influence of cutting speed on the chip "slide-stop-slide" phenomenon is evaluated, and the critical cutting speed for the above phenomenon to occur is determined as V min ; Step 4: Complete the pre-processing operation of the curved surface component according to the analysis results; The angle θ is defined as the angle between the line connecting the center of rotation of the curved surface component and the center of the arc edge of the tool and the X axis. i , during the turning process of curved components, the rotation angle θ i The range of variation is [θ1,θ n ]; According to the tool contact state analysis method described in step 2, the corresponding corner area when the cutting edge contact length increases is determined to be [θ1,θ2]; During the processing of curved surface components, the moving area of ​​the starting point of the contact area on the cutting edge overlaps with the moving area of ​​the end point of the contact area on the cutting edge. According to the tool contact state analysis method described in step 2, the corresponding corner area when the contact point moving area overlaps is determined to be [θ3,θ n ]; According to the cutting test results of the material to be processed, the critical cutting speed when the "slip-stop-slip" phenomenon occurs is determined to be V min , that is, the turning speed of the curved component is higher than V min The "slip-stop-slip" phenomenon disappears when the cutting speed is constant at Sp. The corresponding angle region of the curved surface component where this phenomenon occurs is determined to be [θ4,θ n ]; According to the above calculation results, the turning tool used in the current process stage is used to complete the pre-removal operation of part of the material on the curved surface component; Among them, the corner area [θ1,θ2] and [θ4,θ n ] is completely removed from the curved surface component, and the material removal depth is Rdep; three grooves are prefabricated in the corner area [θ2,θ3], and the corresponding corner intervals are and The material removal depth of the groove structure is Rdep; two grooves are prefabricated in the corner area [θ3,θ4], and the corresponding corner intervals are and The material removal depth of the groove structure is Rdep; Step 5. After completing the pre-processing operation of the curved surface component, unload the curved surface component and let it stand; then replace the cutting tool, adjust the cutting parameters and re-clamp the curved surface component, and finally complete the allowance removal operation in the precision machining stage of the curved surface component according to the processing requirements.

2. The workpiece pretreatment method for improving the turning accuracy of curved surface components according to claim 1 is characterized in that: The coordinates of the profile points of the cutting edge profile are obtained by measuring with an optical microscope.

3. The workpiece pretreatment method for improving the turning accuracy of curved surface components according to claim 1 is characterized in that: Angle The range of change is 3°~30°.

4. The workpiece pretreatment method for improving the turning accuracy of curved surface components according to claim 1, characterized in that: The calculation formula of the angle θ1 is arcsin(T / R).

5. The workpiece pretreatment method for improving the turning accuracy of curved surface components according to claim 1, characterized in that: Angle θ n is 90°.

6. The workpiece pretreatment method for improving the turning accuracy of curved surface components according to claim 1, characterized in that: The calculation formula of angle θ4 is arccos{1000·V min / [Sp·π·(R-dep)]}.

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