A lathe straight groove machining method based on double-c-axis cooperative motion

Abstract

The application provides a straight slot processing method based on double-C-axis cooperative motion of a lathe, and solves the problems of multiple clamping, low precision and dependence on special milling equipment in straight slot processing of large rotary components. A side milling head device is installed on a numerical control vertical lathe, a workpiece chuck rotation shaft is used as a first rotation shaft C1, and a milling head swing shaft is used as a second rotation shaft C2; a coordinate transformation relationship between a machine tool coordinate system and a workpiece coordinate system is established, a cooperative motion law of the C1 shaft and the C2 shaft is determined, a tool tip forms a linear motion track in a workpiece reference coordinate system; combined with rough processing layering and track planning of multiple finishing modifications, a numerical control program containing C1, C2 and feeding shaft linkage control is generated after post-processing. The application can complete high-precision processing of the straight slot in the large rotary component on the same equipment, reduces workpiece transfer and repeated clamping, reduces equipment cost, and is suitable for processing of the key groove or positioning groove of a magnetic yoke section of a pumped storage unit.

Description

Technical Field

[0001] This invention relates to the fields of machining and CNC machining technology, and in particular to a method for controlling the coordinated motion of two C-axis axes on a lathe for machining straight groove structures inside large rotating components. Background Technology

[0002] The magnetic yoke is a key component of the generator in a pumped-storage hydroelectric power unit, and its structure is typically a large annular rotating component. Multiple high-precision keyways or locating slots need to be machined on the inner side of the yoke for mounting magnetic poles or related structural components. These slot structures generally extend axially or in a specific direction and are distributed in a localized area around the circumference, requiring extremely high positional accuracy, straightness, and dimensional precision.

[0003] In existing technologies, the machining of large annular rotating components typically employs a multi-stage process: first, the rotating structure is turned on a large CNC vertical lathe; then, the workpiece is hoisted and transferred to a large milling machine or boring machine for milling the inner keyway structure. This traditional process has the following drawbacks: First, the processing flow is complex and the production efficiency is low; the workpiece needs to be hoisted, transferred and re-clamped multiple times between different equipment, which takes a long time and makes it difficult to meet the needs of batch or high-efficiency production.

[0004] Secondly, due to the large size and heavy weight of the workpiece, it is difficult to ensure that the positioning reference is completely consistent each time it is re-clamped, which makes it difficult to stably control key indicators such as the radial position, centripetal angle and straightness of the sidewall of the groove structure within the design requirements.

[0005] Third, while existing milling-turning lathes with powered turrets can perform some milling functions, their powered tools are mounted on the turret structure, resulting in limited overall rigidity and cutting capabilities, making it difficult to meet the requirements for machining deep grooves in large components. Large milling-turning machining centers, on the other hand, have complex structures, high purchase costs, and are limited by machine tool workspace, restricting their application when machining magnetic yoke sections with diameters of several meters.

[0006] Fourth, conventional CNC vertical lathes lack motion control methods that enable the tool tip to form a linear trajectory in the workpiece reference system, making it impossible to directly complete the machining of the straight groove structure inside the rotating component.

[0007] If straight slot milling can be achieved on the basis of existing CNC vertical lathes through reasonable motion axis configuration and coordinated control, the utilization rate of equipment will be significantly improved and the processing cost will be reduced. Therefore, how to utilize existing large lathe equipment to achieve high-precision and high-efficiency machining of straight slot structures of large rotating components by improving motion control methods, reducing workpiece transfer and repeated clamping, and reducing dependence on special milling equipment has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the problems of complex and inefficient machining processes for large rotating components in existing technologies; positioning errors caused by repeated clamping affecting machining accuracy; strong dependence on large-scale dedicated milling equipment, resulting in high equipment costs; and the difficulty of directly machining straight groove structures on existing CNC vertical lathes, this invention proposes a lathe straight groove machining method based on dual C-axis cooperative motion. The method includes: Step 1: Conduct a machining feasibility analysis based on the workpiece geometry and tool parameters to determine the tool swing range and the movement range of the lathe rotary axis and the milling head swing axis; Step 2: Install a side milling head device on the CNC vertical lathe, using the workpiece chuck rotation axis as the first rotation axis C1 and the milling head swing axis as the second rotation axis C2. Align the milling head rotation center with the machine tool spindle center to ensure that the actual tool swing length meets the preset tool swing length. Step 3: Establish the geometric relationship between the tool path and the machine tool motion axis, determine the cooperative motion relationship between the first rotary axis C1 and the second rotary axis C2, so that the tool tip forms a linear motion trajectory in the workpiece reference coordinate system; Step 4: Establish a 3D model of the workpiece, and design a tool path that combines roughing and finishing based on the characteristics of the groove structure; according to the designed tool path, set the tool axis to be perpendicular to the bottom plane of the groove, and lock the Y-axis movement so that the tool path is generated only in the XZ plane, thereby generating tool path data; Step 5: Construct a dual C-axis CNC post-processing model, convert the generated toolpath data into multi-axis linkage control instructions that can be executed by the machine tool, and generate a CNC machining program that includes linkage control of the first rotary axis C1, the second rotary axis C2, and the feed axis. Step 6: Execute the CNC machining program to enable the tool to complete the machining of the straight groove structure of the workpiece under the coordinated motion control of the dual C-axis.

[0009] Furthermore, step one specifically involves: The tool swing range is calculated based on the workpiece's radius of gyration, groove width, groove depth, milling cutter diameter, and total tool length. The calculation method is as follows:

[0010] in, R The workpiece's radius of rotation; H For the depth of the groove; W The width of the slot; This is the minimum allowable swing angle of the milling head; k D is the tool overhang stiffness coefficient; D is the milling cutter diameter; The range of C-axis rotation angle of the lathe is calculated based on the distance of the infeed plane. The calculation method is as follows:

[0011]

[0012] in, This represents the minimum rotation angle of the lathe's C-axis. This represents the maximum rotation angle of the lathe's C-axis. This is the distance in the infeed plane; For safe plane distance; The length of the tool swing arm.

[0013] Furthermore, in step two, The rotation axes of the first rotary axis C1 and the second rotary axis C2 are both parallel to the Z-axis direction of the machine tool.

[0014] Furthermore, in step three, The geometric relationship between the tool path and the machine tool motion axes is established, and the cooperative motion relationship between the first rotary axis C1 and the second rotary axis C2 is determined as follows: Establish the coordinate transformation relationship from the machine tool fixed coordinate system to the slot coordinate system that rotates with the workpiece:

[0015] The mapping relationship between the tool tip coordinates in the rotating slot coordinate system and the tool tool coordinate system is as follows:

[0016]

[0017] in, , Let be the coordinates of the tool tip in the groove coordinate system that rotates with the workpiece; , The coordinates of the tool tip in the machine tool's fixed coordinate system are given.

[0018] Furthermore, in step four, Roughing involves gradually removing material from the tank using a layered cutting method, and stopping roughing before the remaining machining allowance on the tank sidewalls and bottom reaches the preset minimum machining allowance.

[0019] Furthermore, in step four, The finishing process involves trimming the sidewalls of the groove according to a preset allowance sequence to gradually approach the target size.

[0020] Furthermore, the preset margin sequence is 0.5mm, 0.2mm, 0.1mm, 0.05mm and 0mm.

[0021] Furthermore, in step four, During the machining process, the machine tool's rotary axis is first positioned at a safe plane angle, and then the tool is lowered along the Z-axis to perform cutting.

[0022] Furthermore, in step four, The toolpath is a straight line trajectory along the sidewall of the groove in the programming coordinate system.

[0023] Furthermore, step five specifically involves: The starting point coordinates, ending point coordinates, and tool axis direction vector of the tool tip trajectory are extracted from the tool path. The tool trajectory in the programming coordinate system is transformed to the machine tool coordinate system, and a geometric mapping relationship between the tool trajectory and the machine tool rotation axis is established. The tool tip spatial trajectory is decomposed into the C1 axis rotation angle, C2 axis swing angle, and X-axis and Z-axis feed rates. A CNC machining program containing the linkage control of the C1 axis, C2 axis, X-axis, and Z-axis is generated by the G01 linear interpolation command.

[0024] The beneficial effects of this invention are: To address the problems of low machining efficiency and heavy reliance on specialized milling equipment in the machining of large annular groove structures in existing technologies, this invention proposes a lathe straight groove machining method based on dual C-axis coordinated motion, which has the following improvements: 1. This invention installs a side-mounted milling head device on a CNC vertical lathe, using the workpiece chuck rotation axis as the first rotation axis C1 and the milling head swing axis as the second rotation axis C2, establishing a coordinated motion relationship between the two C-axises. This allows the tool tip to form a linear motion trajectory in the workpiece reference coordinate system, thereby completing turning and milling operations on the same machine. This method reduces workpiece transfer and repeated clamping between different machines, simplifies the machining process, and significantly improves machining efficiency.

[0025] 2. This invention establishes a coordinate transformation relationship between the machine tool's fixed coordinate system and the slot coordinate system that rotates with the workpiece, converting the curved trajectory of the tool tip in the machine tool coordinate system into a straight trajectory in the workpiece coordinate system, thus avoiding positioning errors caused by repeated clamping. Simultaneously, by combining roughing and finishing in trajectory planning, the dimensional accuracy and surface quality of the slot sidewall are effectively controlled.

[0026] 3. This invention only requires the addition of a side milling head device to an existing CNC vertical lathe. By reasonably controlling the motion relationship of the two C-axis, straight groove machining can be achieved. There is no need to purchase a large turning and milling machining center or a special milling machine, which makes full use of existing equipment resources and greatly reduces equipment investment costs.

[0027] 4. This invention constructs a dual C-axis CNC post-processing model, which can convert tool path data into a CNC machining program that includes the linkage control of the C1 axis, C2 axis and feed axis, enabling the CNC vertical lathe to process complex groove structures such as straight grooves and keyways, thus expanding the process range of the CNC vertical lathe.

[0028] 5. This invention employs a layered cutting method for roughing, quickly removing most of the material, followed by multiple small-scale finishing processes to gradually approach the target dimensions. This method reduces the impact of single-cycle cutting force fluctuations on machining stability and improves the process reliability of deep groove machining for large components. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the overall process of the method of the present invention; Figure 2 A schematic diagram of the magnetic yoke end structure of a pumped storage unit; Figure 3 This is a schematic diagram of the workpiece of the present invention being mounted on the lathe chuck; Figure 4 This is a schematic diagram of the side-mounted CNC milling head mounting structure of the present invention; Figure 5 This is a schematic diagram of the CNC machining model of the present invention; Figure 6 This is a schematic diagram of the blade tip trajectory simulation of the present invention; Figure 7 This is a schematic diagram illustrating the relationship between the machining rotation angle and displacement in this invention; Figure 8 This is a schematic diagram of the CNC machining trajectory simulation of the present invention. Detailed Implementation

[0031] 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, and 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.

[0032] Combination Figures 1-8 This invention proposes a lathe straight groove machining method based on dual C-axis cooperative motion, the method comprising: Step 1: Conduct a machining feasibility analysis based on the workpiece geometry and tool parameters to determine the tool swing range and the movement range of the lathe rotary axis and the milling head swing axis; Furthermore, step one specifically involves: The tool swing range is calculated based on the workpiece's radius of gyration, groove width, groove depth, milling cutter diameter, and total tool length. The calculation method is as follows:

[0033] in, R The workpiece's radius of rotation; H For the depth of the groove; W The width of the slot; This is the minimum allowable swing angle of the milling head; k D is the tool overhang stiffness coefficient; D is the milling cutter diameter; The range of C-axis rotation angle of the lathe is calculated based on the distance of the infeed plane. The calculation method is as follows:

[0034]

[0035] in, This represents the minimum rotation angle of the lathe's C-axis. This represents the maximum rotation angle of the lathe's C-axis. This is the distance in the infeed plane; For safe plane distance; The length of the tool swing arm.

[0036] Step one specifically involves theoretical verification and machining feasibility calculation. Before toolpath planning and actual machining, it is necessary to conduct a theoretical analysis of machining feasibility based on the workpiece geometric parameters, tool structural parameters, and machine tool motion range to determine the tool swing length, machine tool rotation angle range, and geometric characteristics of the tool tip trajectory, thereby ensuring that the machining can form the target straight groove structure.

[0037] Step one specifically includes: Step S1.1: Calculation of milling head tool geometric parameters and swing length critical values. Workpiece rotation radius. R , slot width W trench depth H Milling cutter diameter D Total length of the cutting tool L (Sum of tool length and milling head tilt length), distance from the feed plane l C-axis rotation angle of lathe θ and milling head tilt angle α .

[0038] To ensure the cutting tool can enter the slot for cutting and to guarantee cutting efficiency, the milling cutter diameter should meet the following requirements:

[0039] Based on the machining geometry, the relationship between the tool swing length and the swing angle can be established:

[0040] The milling head tilt angle is limited by the machine tool structure. If the machine tool's allowable tilt angle range is:

[0041] The theoretical range of the tool pendulum length can be obtained:

[0042] Considering the rigidity requirements of the tool overhang:

[0043] in k This is the tool overhang stiffness coefficient, typically... k =4~6, so the range of values ​​for the milling head swing length can be determined as follows:

[0044] Step S1.2: Calculation of the C-axis rotation angle range of the lathe; After determining the tool length and milling head swing range, it is necessary to calculate the rotation angle range of the lathe rotary table C-axis during machining. Since the tool needs to feed onto the safe plane outside the slot, the C-axis has two limit angles during machining: the safe plane position and the slot bottom position. The theoretical range of the lathe C-axis rotation angle can be obtained from geometric relationships:

[0045]

[0046] To evaluate the trajectory error generated when using linear interpolation, the curvature of the tool tip trajectory is analyzed. Because the C-axis rotation angle range is small during machining, the radius of curvature of the tool tip trajectory is much larger than the machining length; therefore, the geometric deviation between the tool tip trajectory and the straight line is minimal. In actual CNC machining, the G01 linear interpolation command can be used to achieve tool movement.

[0047] Step 2: Install a side milling head device on the CNC vertical lathe, using the workpiece chuck rotation axis as the first rotation axis C1 and the milling head swing axis as the second rotation axis C2. Align the milling head rotation center with the machine tool spindle center to ensure that the actual tool swing length meets the preset tool swing length. Furthermore, in step two, The rotation axes of the first rotary axis C1 and the second rotary axis C2 are both parallel to the Z-axis direction of the machine tool.

[0048] After completing the calculations in step one, a side-mounted milling head device needs to be installed on the CNC vertical lathe, and the milling system needs to be geometrically corrected to ensure that the actual motion relationship of the machine tool is consistent with the theoretical model. The milling and turning composite equipment used in this invention includes two motion axes rotating around parallel axes: the workpiece chuck rotation axis C1 and the milling head swing rotation axis C2; both of their rotation axes are in the Z-axis direction of the machine tool.

[0049] During machining, the workpiece is mounted on the machine tool chuck and rotates with axis C1, while the milling head oscillates around axis C2. By controlling the synchronous motion of the two rotating axes, the tool axis is positioned in a predetermined posture in space. After mounting the milling head, the geometric relationship between the milling head's rotation center and the machine tool spindle center needs to be corrected so that the distance from the tool's rotation center to the milling head's oscillation center meets the tool swing length parameter calculated in step one. L Through the above installation and calibration, the actual motion structure of the machine tool forms a turning and milling machining system with dual C-axis coordinated motion, providing an equipment foundation for subsequent tool path planning.

[0050] Step 3: Establish the geometric relationship between the tool path and the machine tool motion axis, determine the cooperative motion relationship between the first rotary axis C1 and the second rotary axis C2, so that the tool tip forms a linear motion trajectory in the workpiece reference coordinate system; Furthermore, in step three, The geometric relationship between the tool path and the machine tool motion axes is established, and the cooperative motion relationship between the first rotary axis C1 and the second rotary axis C2 is determined as follows: Establish the coordinate transformation relationship from the machine tool fixed coordinate system to the slot coordinate system that rotates with the workpiece:

[0051] The mapping relationship between the tool tip coordinates in the rotating slot coordinate system and the tool tool coordinate system is as follows:

[0052]

[0053] in, , Let be the coordinates of the tool tip in the groove coordinate system that rotates with the workpiece; , The coordinates of the tool tip in the machine tool's fixed coordinate system are given.

[0054] After completing the installation of the machine tool and determining the motion relationships, it is necessary to design the tool machining trajectory based on the structural characteristics of the keyway within the yoke section. Due to the large width of the keyway and the significant amount of material removal within the yoke section, this invention employs a trajectory planning method combining roughing and finishing to improve machining efficiency and ensure groove accuracy. Step three specifically includes: Establish a fixed coordinate system for the machine tool, with the lathe spindle center as the origin, the X-axis as the radial direction, and the Y-axis as the tangential direction. The bottom end of the tool is always located at the groove boundary, and its geometric constraints are as follows:

[0055]

[0056] If the total length of the cutting tool and the pendulum is L, then the coordinates of the cutting tip are:

[0057]

[0058] The above equation is the trajectory parameter equation of the tool tip in the fixed coordinate system of the machine tool.

[0059] To analyze the motion trajectory of the tool tip relative to the workpiece groove structure, it is necessary to establish a groove coordinate system that rotates with the workpiece. Let the rotation angle of the groove coordinate system relative to the machine tool coordinate system be θ. Then the relationship between the two coordinate systems is:

[0060] The mapping relationship between the tool tip coordinates in the rotating slot coordinate system and the machine tool coordinate system can be obtained as follows:

[0061]

[0062] Bring into the tip of the knife , The coordinates can be obtained as follows:

[0063] Therefore, in the slot coordinate system Since the constant is constant, the tool tip trajectory is a straight line. This proves that, in the workpiece rotation reference frame, the tool tip can form a stable straight line trajectory, thus achieving groove machining.

[0064] Step 4: Establish a 3D model of the workpiece, and design a tool path that combines roughing and finishing based on the characteristics of the groove structure; according to the designed tool path, set the tool axis to be perpendicular to the bottom plane of the groove, and lock the Y-axis movement so that the tool path is generated only in the XZ plane, thereby generating tool path data; Furthermore, in step four, Roughing involves gradually removing material from the tank using a layered cutting method, and stopping roughing before the remaining machining allowance on the tank sidewalls and bottom reaches the preset minimum machining allowance.

[0065] Furthermore, in step four, The finishing process involves trimming the sidewalls of the groove according to a preset allowance sequence to gradually approach the target size.

[0066] Furthermore, the preset margin sequence is 0.5mm, 0.2mm, 0.1mm, 0.05mm and 0mm.

[0067] Furthermore, in step four, During the machining process, the machine tool's rotary axis is first positioned at a safe plane angle, and then the tool is lowered along the Z-axis to perform cutting.

[0068] Furthermore, in step four, The toolpath is a straight line trajectory along the sidewall of the groove in the programming coordinate system.

[0069] After determining the tool path planning, a 3D model of the workpiece needs to be created in the CNC programming software and the corresponding toolpath needs to be generated. Step four specifically includes: S4.1: 3D model establishment; First, a 3D geometric model of the keyway in the magnetic yoke section is established based on the dimensions of the workpiece drawing. Key parameters such as the tool rotation center, tool swing length, and machine tool rotation axis position are defined in the model to provide a geometric basis for tool path generation.

[0070] S4.2: Tool posture constraint; During the tool path generation process, in order to ensure that the tool posture meets the machining requirements, the tool axis is set to be perpendicular to the groove bottom plane, thereby ensuring that the tool bottom surface and the groove bottom surface maintain the correct machining relationship.

[0071] S4.3: Machine tool motion constraints; In the machine tool control settings, the tool path event is constrained. By locking the Y-axis motion, the tool path is generated only in the XZ plane, thereby ensuring that the generated tool trajectory conforms to the motion structure of the milling and turning machine.

[0072] S4.4: Tool path generation; Under the above geometric constraints and machine tool motion constraints, the CNC programming software generates tool path data. This path is represented as a straight line trajectory along the sidewall of the slot in the programming coordinate system, providing basic data for subsequent CNC program generation.

[0073] Roughing trajectory design: During roughing, a large-diameter end mill is selected, and most of the material in the groove is gradually removed through a layered tool arrangement, while a certain machining allowance is left on the sidewalls and bottom of the groove, so that the groove contour gradually approaches the final dimensions. The main goal of the roughing stage is to improve material removal efficiency, and the groove space is gradually expanded through multiple tool arrangements to provide a stable machining foundation for subsequent finishing.

[0074] Finishing trajectory design: During the finishing stage, the groove sidewall is repeatedly finished by gradually reducing the machining allowance, for example, by gradually approaching the target size according to a preset allowance sequence, such as 0.5 mm, 0.2 mm, 0.1 mm, 0.05 mm, 0 mm, etc. Through multiple small-allowance cuts, the dimensional accuracy and surface quality of the groove sidewall can be effectively controlled, and the impact of cutting force fluctuations on machining stability can be reduced.

[0075] Tool feed and cutting trajectory planning: In the actual machining process, the tool is first fed in to position the machine tool's rotary axis to the corresponding machining angle, and then the tool is lowered along the machine tool's Z-axis direction so that the tool enters the machining position while maintaining a constant rotation angle.

[0076] After the initial feed is completed, cutting is then performed along the sidewall of the groove, thus achieving layer-by-layer machining of the groove structure. Corresponding toolpaths are designed for different machining allowances, and multiple toolpaths are used to gradually approach the final groove dimensions, thereby improving machining stability and ensuring the straightness of the groove sidewall.

[0077] Step 5: Construct a dual C-axis CNC post-processing model, convert the generated toolpath data into multi-axis linkage control instructions that can be executed by the machine tool, and generate a CNC machining program that includes linkage control of the first rotary axis C1, the second rotary axis C2, and the feed axis. Furthermore, step five specifically involves: The starting point coordinates, ending point coordinates, and tool axis direction vector of the tool tip trajectory are extracted from the tool path. The tool trajectory in the programming coordinate system is transformed to the machine tool coordinate system, and a geometric mapping relationship between the tool trajectory and the machine tool rotation axis is established. The tool tip spatial trajectory is decomposed into the C1 axis rotation angle, C2 axis swing angle, and X-axis and Z-axis feed rates. A CNC machining program containing the linkage control of the C1 axis, C2 axis, X-axis, and Z-axis is generated by the G01 linear interpolation command.

[0078] Because this invention employs a machining method that coordinates the rotation axis of the lathe chuck and the oscillating axis of the milling head, the post-processing program of conventional mill-turning composite equipment cannot directly convert the toolpath into corresponding CNC machining instructions. Therefore, it is necessary to construct a dual C-axis CNC post-processing model suitable for this machining method. This post-processing model is used to convert the toolpath data generated by the CNC programming software into multi-axis linkage control instructions that can be executed by the machine tool.

[0079] Step five specifically includes: S5.1: Tool Path Data Extraction; First, tool motion trajectory data is extracted from the toolpath generated by the CNC programming software, including the starting point coordinates, ending point coordinates, and tool axis direction vector of the tool tip trajectory. In the programming coordinate system, this toolpath is represented as a straight line trajectory along the groove sidewall.

[0080] S5.2: Tool Path Coordinate Transformation; Since the actual machine tool motion is achieved by the workpiece rotation axis C1, the milling head oscillation axis C2, and the X and Z feed axes, it is necessary to convert the tool path in the programming coordinate system into a motion relationship in the machine tool coordinate system. By establishing a geometric mapping relationship between the tool path and the machine tool rotation axes, the tool tip spatial trajectory is decomposed into control quantities for each motion axis of the machine tool, including: The C1 axis rotation angle is used to control the rotation of the workpiece chuck; the C2 axis oscillation angle is used to control the milling head posture; and the X and Z axis feed rates are used to control the tool feed motion.

[0081] S5.3: Dual C-axis motion mapping calculation; During the tool path conversion process, the machine tool rotation angle corresponding to the tool path is calculated based on the geometric relationship established in step S1, so that the C1 axis and the C2 axis maintain a synchronous change relationship.

[0082] This mapping calculation ensures that the tool tip maintains a linear motion trajectory in the workpiece reference coordinate system.

[0083] S5.4: Linear interpolation program generation; In the machine tool coordinate system, the actual trajectory of the tool tip is represented as an approximate curve. To simplify the machine tool control program, the starting and ending points of the tool trajectory are extracted during post-processing, and tool motion commands are generated using linear interpolation. Specifically, the G01 command is used to implement the linear feed motion of the tool from the starting point to the ending point, thereby forming a stable machining trajectory in the machine tool control system.

[0084] S5.5: CNC program output; Based on the above motion mapping relationship and interpolation method, generate a CNC machining program that includes the linkage control of C1 axis, C2 axis and X and Z axes, and output it as a G code file that can be recognized by the machine tool control system, thereby completing the automatic generation of the dual C-axis collaborative milling and turning machining program.

[0085] Step 6: Execute the CNC machining program to enable the tool to complete the machining of the straight groove structure of the workpiece under the coordinated motion control of the dual C-axis.

[0086] After the CNC machining of the keyway in the yoke section is completed, the machining results need to be inspected to verify the feasibility and machining accuracy of the machining method of the present invention.

[0087] First, the machined internal keyway is measured using laser measuring equipment or a coordinate measuring machine to check the key geometric parameters of the keyway shape, including: the flatness of the keyway bottom; the parallelism of the keyway sidewalls; the accuracy of the keyway distribution; and the centripetal force of the keyway relative to the workpiece center. By measuring the above key dimensions, the actual geometric data of the keyway after machining can be obtained.

[0088] The actual machining data obtained from the measurements were compared and analyzed with the parameters obtained from the theoretical analysis in step one to evaluate the linearity error of the machining trajectory and the geometric accuracy of the groove. The measurement results show that the groove distribution accuracy of the machined internal keyway is approximately 0.02 mm to 0.03 mm, and the flatness of the groove bottom is less than 0.02 mm. All indicators meet the machining accuracy requirements of the internal keyway in the yoke section.

[0089] Through the above-mentioned machining measurements and data comparison analysis, it was verified that the milling and turning composite machining method based on dual C-axis coordinated motion proposed in this invention can stably achieve high-precision machining of the keyway within the magnetic yoke section. Simultaneously, this method expands the application scope of CNC vertical lathes in the machining of complex groove structures, providing a new CNC machining technology solution for the machining of keyways within the magnetic yoke section of pumped storage units.

[0090] This invention proposes a lathe straight groove machining method based on dual C-axis coordinated motion, comprising the following steps: A machining feasibility analysis is conducted based on the workpiece's radius of rotation, groove structure dimensions, tool structure parameters, and machine tool motion range to determine the tool swing length parameters and the motion range of the lathe's rotary axis and the milling head swing axis; a side-mounted milling head device is installed on a CNC vertical lathe, with the workpiece chuck rotary axis serving as the first rotary axis C1 and the milling head swing axis serving as the second rotary axis C2, and both rotary axes rotating in the same direction along the machine tool's Z-axis; by establishing the geometric relationship between the tool trajectory and the machine tool motion axes, the coordinated motion relationship between the first rotary axis C1 and the second rotary axis C2 is determined, enabling the tool tip to form a linear motion trajectory in the workpiece reference coordinate system; a three-dimensional model of the workpiece is established based on the groove structure to be machined, and a tool machining trajectory is generated; the tool trajectory is converted into machine tool motion control commands through a CNC post-processing model, and a CNC machining program containing the linkage control of the first rotary axis C1, the second rotary axis C2, and the feed axis is generated; the CNC machining program is executed, enabling the tool to complete the machining of the workpiece's straight groove structure under dual C-axis coordinated motion control. The first rotary axis C1 is the workpiece chuck rotary axis, used to drive the workpiece to rotate around the machine tool spindle center; the second rotary axis C2 is the milling head oscillation rotary axis, used to adjust the milling cutter posture so that the tool axis forms a predetermined machining posture in space. By establishing a fixed coordinate system of the machine tool and a workpiece coordinate system that rotates with the workpiece, and establishing the coordinate transformation relationship between the two coordinate systems, the movement trajectory of the tool tip in the workpiece coordinate system is kept as a straight line. By calculating the parametric equation of the tool tip trajectory and establishing the synchronous change relationship between the first rotary axis C1 and the second rotary axis C2, the curved trajectory of the tool in the machine tool coordinate system is converted into a straight line trajectory in the workpiece coordinate system. The tool trajectory is planned through a combination of roughing and finishing. Roughing is carried out by gradually removing material in the groove through layered tool arrangement, and finishing is carried out by gradually approaching the target groove size through multiple small-mass cuts. During the CNC program generation process, by establishing the geometric mapping relationship between the tool trajectory and the machine tool rotary axes, the spatial trajectory of the tool tip is decomposed into the rotation angle of the first rotary axis C1, the oscillation angle of the second rotary axis C2, and the feed amount of the machine tool feed axis. The CNC machining program uses linear interpolation commands to control the tool movement from the starting machining position to the ending machining position, thereby achieving stable machining of straight groove structures.

[0091] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified in the following embodiments, conventional conditions or existing test conditions were followed.

[0092] Example To verify the feasibility of the method of the present invention, an example of keyway processing in the magnetic yoke section of a pumped storage unit is selected for illustration.

[0093] The magnetic yoke section is a large annular rotating component with a rotation radius of 1245 mm, requiring a keyway structure to be machined on its inner side. The machined keyway has a width of 108.1 mm and a depth of 11.64 mm.

[0094] The machining equipment is a large CNC vertical lathe equipped with a side-mounted CNC milling head. End mills are used for milling during the machining process, with a tool diameter of... D = 80mm, tool pendulum length L = 452.15mm.

[0095] According to the theoretical method described in step one of this invention, the tool parameters and machine tool motion range are calculated and verified to confirm that the selected tool parameters and machine tool motion range meet the keyway machining requirements, and the cooperative motion relationship between the lathe C-axis and the milling head swing axis is determined.

[0096] Subsequently, a side-mounted milling head device was installed on the machine tool, and the positional relationship between the milling head swing center and the machine tool spindle center was corrected to ensure that the tool swing length met the requirements. L = 452.15mm installation requirement, and at the same time establish the correspondence between the machine tool coordinate system and the workpiece coordinate system.

[0097] A 3D model of the magnetic yoke segment is created in the CNC programming software, and the tool path for slot machining is generated according to the method described in step three. During the machining process, rough machining is performed first, and the material in the slot is gradually removed by layered tool arrangement, while a certain machining allowance is left on the sidewall of the slot; then finish machining is performed, and the final dimensions are gradually approached by multiple small-allowance trimming operations.

[0098] After toolpath planning is completed, the tool path is converted into a CNC machining program by a post-processing program. During machining, the coordinated movement of the workpiece chuck rotation axis C1 and the milling head swing axis C2 is controlled to make the tool tip form a linear motion trajectory in the workpiece reference coordinate system, thereby realizing the machining of the keyway structure.

[0099] After machining, the keyway structure was inspected using a coordinate measuring machine. The measurement results showed that the width error was less than 0.03 mm, the flatness of the bottom of the keyway was less than 0.02 mm, and the straightness error of the sidewall was less than 0.02 mm, meeting the machining accuracy requirements of the keyway within the yoke section.

[0100] This verifies that the lathe straight groove machining method based on dual C-axis coordinated motion proposed in this invention can stably achieve high-precision machining of keyway structures of large rotating components on a CNC vertical lathe.

[0101] This invention relates to the fields of machining and CNC machining technology, and discloses a lathe straight groove machining method based on dual C-axis coordinated motion, applicable to the machining of keyways or locating grooves in large rotating components. The method involves installing a side-mounted milling head on a CNC vertical lathe, using the workpiece chuck rotation axis as the first rotation axis C1 and the milling head swing axis as the second rotation axis C2. A geometric relationship between the tool path and the machine tool motion axes is established, and the coordinated motion law of axes C1 and C2 is determined, enabling the tool tip to form a linear motion trajectory in the workpiece reference coordinate system, thereby achieving straight groove machining. During the machining process, a machining feasibility analysis is first performed based on the workpiece geometric parameters and tool parameters to determine the tool swing length and machine tool rotation angle range. Then, a three-dimensional model of the workpiece is established and a tool machining path is generated. The tool path is converted into a CNC machining program containing the linkage control of axes C1, C2, and the feed axis through CNC post-processing, achieving roughing and finishing of the groove structure. This invention enables the machining of straight groove structures in rotating components on large CNC vertical lathes, reducing repeated workpiece clamping, improving machining efficiency, and expanding the application range of CNC vertical lathes in complex groove structure machining.

[0102] The above provides a detailed description of a lathe straight groove machining method based on dual C-axis cooperative motion proposed in this invention. Specific examples have been used to illustrate the principle and implementation of this invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A lathe straight groove machining method based on dual C-axis cooperative motion, characterized in that, Includes the following steps: Step 1: Conduct a machining feasibility analysis based on the workpiece geometry and tool parameters to determine the tool swing range and the movement range of the lathe rotary axis and the milling head swing axis; Step 2: Install a side milling head device on the CNC vertical lathe, using the workpiece chuck rotation axis as the first rotation axis C1 and the milling head swing axis as the second rotation axis C2. Align the milling head rotation center with the machine tool spindle center to ensure that the actual tool swing length meets the preset tool swing length. Step 3: Establish the geometric relationship between the tool path and the machine tool motion axis, determine the cooperative motion relationship between the first rotary axis C1 and the second rotary axis C2, so that the tool tip forms a linear motion trajectory in the workpiece reference coordinate system; Step 4: Establish a 3D model of the workpiece, and design a tool path that combines roughing and finishing based on the characteristics of the groove structure; according to the designed tool path, set the tool axis to be perpendicular to the bottom plane of the groove, and lock the Y-axis movement so that the tool path is generated only in the XZ plane, thereby generating tool path data; Step 5: Construct a dual C-axis CNC post-processing model, convert the generated toolpath data into multi-axis linkage control instructions that can be executed by the machine tool, and generate a CNC machining program that includes linkage control of the first rotary axis C1, the second rotary axis C2, and the feed axis. Step 6: Execute the CNC machining program to enable the tool to complete the machining of the straight groove structure of the workpiece under the coordinated motion control of the dual C-axis.

2. The method according to claim 1, characterized in that, Step one is as follows: The tool swing range is calculated based on the workpiece's radius of gyration, groove width, groove depth, milling cutter diameter, and total tool length. The calculation method is as follows: in, R The workpiece's radius of rotation; H For the depth of the groove; W The width of the slot; This is the minimum allowable swing angle of the milling head; k D is the tool overhang stiffness coefficient; D is the milling cutter diameter; The range of C-axis rotation angle of the lathe is calculated based on the distance of the infeed plane. The calculation method is as follows: in, This represents the minimum rotation angle of the lathe's C-axis. This represents the maximum rotation angle of the lathe's C-axis. This is the distance in the infeed plane; For safe plane distance; The length of the tool swing arm.

3. The method according to claim 1, characterized in that, In step two, The rotation axes of the first rotary axis C1 and the second rotary axis C2 are both parallel to the Z-axis direction of the machine tool.

4. The method according to claim 1, characterized in that, In step three, The geometric relationship between the tool path and the machine tool motion axes is established, and the cooperative motion relationship between the first rotary axis C1 and the second rotary axis C2 is determined as follows: Establish the coordinate transformation relationship from the machine tool fixed coordinate system to the slot coordinate system that rotates with the workpiece: The mapping relationship between the tool tip coordinates in the rotating slot coordinate system and the tool tool coordinate system is as follows: in, , Let be the coordinates of the tool tip in the groove coordinate system that rotates with the workpiece; , The coordinates of the tool tip in the machine tool's fixed coordinate system are given.

5. The method according to claim 1, characterized in that, In step four, Roughing involves gradually removing material from the tank using a layered cutting method, and stopping roughing before the remaining machining allowance on the tank sidewalls and bottom reaches the preset minimum machining allowance.

6. The method according to claim 1, characterized in that, In step four, The finishing process involves trimming the sidewalls of the groove according to a preset allowance sequence to gradually approach the target size.

7. The method according to claim 6, characterized in that, The preset margin sequence is 0.5mm, 0.2mm, 0.1mm, 0.05mm and 0mm.

8. The method according to claim 1, characterized in that, In step four, During the machining process, the machine tool's rotary axis is first positioned at a safe plane angle, and then the tool is lowered along the Z-axis to perform cutting.

9. The method according to claim 1, characterized in that, In step four, The toolpath is a straight line trajectory along the sidewall of the groove in the programming coordinate system.

10. The method according to claim 1, characterized in that, Step five is as follows: The starting point coordinates, ending point coordinates, and tool axis direction vector of the tool tip trajectory are extracted from the tool path. The tool trajectory in the programming coordinate system is transformed to the machine tool coordinate system, and a geometric mapping relationship between the tool trajectory and the machine tool rotation axis is established. The tool tip spatial trajectory is decomposed into the C1 axis rotation angle, C2 axis swing angle, and X-axis and Z-axis feed rates. A CNC machining program containing the linkage control of the C1 axis, C2 axis, X-axis, and Z-axis is generated by the G01 linear interpolation command.

Images