Integral box bottom mirror image milling program generation method and system

Abstract

The invention provides an integral box bottom mirror image milling program generation method and system. The integral box bottom mirror image milling program generation method comprises the steps of 1, compiling a profile scanning path according to pattern / model input; step 2, compiling a profile scanning path; 3, generating a profile scanning numerical control program; 4, obtaining an actual programming entity; step 5, extracting processing features; step 6, dividing a rough machining area; 7, planning an initial rough machining path; 8, a finish machining area is divided; step 9, planning an initial finish machining path; step 10, generating a milling processing path; and step 11, generating a machining numerical control program. According to the integral box bottom mirror image milling program generation method, the integral box bottom mirror image milling tool path generation steps and method are stipulated, the normalization of integral box bottom mirror image milling program generation is improved, and the machining efficiency and quality of an integral box bottom are further improved; and the bearing capacity and reliability of the carrier rocket are met.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical control machining, and in particular to a method and system for generating a mirror milling machining program for an integral box bottom. Background Art

[0002] The bottom of the box is an important component of the rocket tank. It is a typical large-size, thin-walled, curved and complex part. The design surface of the bottom of the box is the surface of revolution of the first quadrant curve segment of the ellipse around the minor axis. It is often designed as a grid structure to balance strength and transportation capacity by controlling the wall thickness. The weld heat affected zone designed on the overall bottom of the box is characterized by annular steps, circular steps, square steps or anisotropic steps. The wall thickness is thicker and the structure is more complex. Generally, the overall bottom of the box is required to be processed from a roughcast of nearly 10mm in thickness to 2-5mm. Deformation is inevitable during the CNC milling process, which can easily cause overcutting and scrapping of parts, posing a huge challenge to CNC program compilation.

[0003] A search of the prior art literature revealed that there has been no research on the method for generating a processing program for the mirror milling of the overall bottom of the box. The Chinese invention patent authorization number CN105772812B, named as a five-axis mirror milling CNC processing method for the overall formed bottom of the box, proposed an advanced and reliable five-axis mirror milling processing method for the overall formed bottom of the box, realizing the processing of the overall formed bottom with equal wall thickness, controllable deformation, and high precision, but no research has been conducted on the method for generating a processing program for the milling process; the Chinese invention patent authorization number CN115156844B, named as a processing method for the overall formed bottom of the fuel tank of a carrier rocket, proposed a processing process from the overall bottom blank to the finished product, solving the problem of processing the bottom parts of the box, but no research has been conducted on the method for generating a processing program for the milling process; the Chinese invention patent publication number CN115729169A, named as a tool path planning method and system for the mirror milling of the overall bottom of the box, proposed a tool path planning method for the mirror milling of the overall bottom of the box, but it is not specific and has not formed a system. From the above, it can be seen that there is no method for generating a processing program for the milling process of the overall formed bottom of the fuel tank of a carrier rocket.

[0004] Therefore, there is an urgent need for a method for generating a milling processing program for the integrally formed bottom of a launch vehicle fuel tank to improve the efficiency and quality of CNC program compilation and realize efficient and high-quality processing of the integrally formed bottom of a launch vehicle fuel tank. Summary of the invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a method and system for generating a mirror image milling program for an integral box bottom.

[0006] The method for generating a mirror image milling program for an integral box bottom provided by the present invention comprises: Step 1: Obtain the inner surface by extracting it from the theoretical model or drawing it according to the inner surface equation; Step 2: Use the inner surface in step 1 as the auxiliary programming surface to compile the surface scanning path; Step 3: Generate a surface scanning NC program through software post-processing according to the surface scanning path, and bring the surface scanning NC program into the software for simulation. If the simulation result fails, return to step 2 to recompile the surface scanning path. If the simulation result passes, go to step 4; Step 4: On the mirror milling device, call the surface scanning NC program in step 3 to scan the inner surface, obtain the surface point cloud data, and fit the point cloud data in the software to form an actual programming entity; Step 5: Extract all thickening / thinning area transition lines on the actual programming entity, and project them onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as machining features; Step 6: The process of milling the box bottom wall thickness from the blank thickness to the thickened area wall thickness is called rough machining. The rough machining area is divided to ensure that the tool centers of the two milling paths do not overlap; Step 7: Perform initial rough machining path planning on the auxiliary programming surface, and perform trajectory planning one by one according to the divided areas; Step 8: The process of milling the thickness of the bottom wall of the box from the thickened area to the thinned area is called finishing. The finishing area needs to be divided to ensure that the tool centers of the two milling paths do not overlap; Step 9: Perform initial finishing path planning on the auxiliary programming surface, and perform trajectory planning one by one according to the divided areas; Step 10: Generate a milling processing path according to the milling paths planned in steps 8 and 9; Step 11: Based on the milling processing path generated in step 10, generate a machining NC program through software post-processing.

[0007] Preferably, in step 1, the inner surface is obtained by extracting it from a theoretical model or drawing it according to the inner surface equation, and the inner surface envelops the range of mirror milling processing, and the theoretical inner surface is offset or thickened according to the theoretical wall thickness of the thinning area, and the formed surface is used as an auxiliary programming surface.

[0008] Preferably, in step 2, a surface scanning path is planned on the auxiliary programming surface, the positive direction of the Z axis of the programming coordinate system is set upward, the origin of the coordinate system is the rotation center of the auxiliary programming surface, the origin of the Z direction is located on the upper surface of the physical tooling, and the inner surface is divided into four parts for scanning. The programming range of each scanned surface covers one-quarter of the auxiliary programming surface, extending 20mm on all sides. The direction of the scanning path starts from the milling lower contour line, and one of the intersections of the lower contour line and the contour line is used as the starting point, and the upper contour line is gradually approached in a reciprocating manner. The scanning track spacing is 50mm to 60mm, and the scanning programs of the remaining three quadrants are formed by the program of the first quadrant, which is arrayed 90° around the Z axis one by one.

[0009] Preferably, in step 3, a surface scanning dedicated post-processor generated by UG NX POST BUILDER software is used to perform post-processing on the four scanning paths respectively to obtain four surface scanning NC programs; In step 11, all machining program groups are post-processed respectively using the mirror milling post-processor generated by UG NX POST BUILDER software to obtain all CNC machining programs.

[0010] Preferably, in step 4, in Geomagic Design software, the actual programming entity is formed by fitting the scanned surface point cloud data file; the point cloud file is processed by noise elimination, sampling, smoothing, triangulation and surface fitting operations, and after the surface is generated, the body deviation function is used to confirm whether the generated surface meets the subsequent processing requirements. If not, it is returned for modification until the requirements are met and the solid model is exported. The solid model is a three-dimensional model format file readable by UG software, including model space coordinate information.

[0011] Preferably, in step 5, all the thickening / thinning zone transition lines are extracted from the theoretical model and projected onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as processing features; the upper and lower boundaries are truncated according to the process requirements, the small end is offset upward by 5mm to 10mm according to the truncation requirements to extract the contour, and the large end is offset downward by 5mm to 10mm according to the truncation requirements to extract the contour, and are projected onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as the upper and lower boundaries, respectively.

[0012] Preferably, in step 6, the process of milling the thickness of the box bottom wall from the blank thickness to the wall thickness of the thickened area is called rough machining. During rough machining, the single milling depth does not exceed 3mm, and multiple milling is performed according to the allowance. On the auxiliary programming surface, the rough machining area is divided according to the upper and lower boundaries, and the division is performed according to the latitude direction and the cutting time of a single area does not exceed 2h; the boundary between two adjacent areas maintains a spacing of 50%+0.6mm to 100%-0.6mm tool diameter; In step 7, the initial rough machining path planning is performed on the auxiliary programming surface, and the trajectory planning is performed one by one according to the divided areas. The rough machining program consists of two programs: the feed operation and the milling operation. In the program group view, the two operations constitute a program group. The feed operation in the program group is located before the milling operation. The milling path length of the feed operation is 50mm~100mm, along the meridian direction, and the end point is the starting point of the milling path. During rough machining, the feed and retract positions are set in the +Y direction.

[0013] Preferably, in step 8, the process of milling the thickness of the box bottom wall from the thickness of the thickened area to the thickness of the thinned area is called finishing. During finishing, the single milling depth does not exceed 2 mm, and multiple milling is performed according to the allowance. When the final milling reaches the theoretical wall thickness, the milling depth does not exceed 1 mm; the area is divided according to the rule that the cutting time of a single area does not exceed 2 hours, and there is no thickening / thinning transition line in the area; the thickening / thinning transition line is offset outward in the area with the thickening / thinning transition line, and the offset is 50% of the contour milling tool diameter + 50% to 75% of the profile milling tool diameter; In step 9, the initial finishing path planning is performed on the auxiliary programming surface, and the trajectory planning is performed one by one according to the divided areas; the surface finishing of the area without thickening / thinning transition lines is consistent with the planned initial roughing path; the surface finishing of the area with thickening / thinning transition lines, the finishing program consists of a feed operation and one or more milling operations. In the program group view, all operations constitute a program group. The feed operation in the program group is located before the milling operation, and the positions between the milling operations are arranged according to the rule that the end point of the previous program is the starting point of the next program.

[0014] Preferably, in step 7 and step 9, the milling operation uses a variable contour milling operation method, the trajectory adopts a reciprocating tool path, the path is planned along the latitude direction, and the spacing between the starting point and the end point of a single tool track is 65% to 90% of the tool diameter; the tool center at the upper and lower boundaries of milling is on the boundary line, the step distance between adjacent paths is 65% to 90% of the tool diameter, the tool paths do not overlap or cross, and the tool path does not have two or more advances / retracts; When the number of intervals of the machining tool path is an even number, the tool cutting feed direction is consistent with the direction of the tool cutting feed end point; conversely, when the number of intervals of the machining tool path is an odd number, the tool cutting feed direction is opposite to the direction of the tool cutting feed end point.

[0015] The system for generating a program for the mirror image milling of an integral case bottom provided by the present invention adopts the method for generating a program for the mirror image milling of an integral case bottom.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention improves the standardization of the generation of the overall box bottom mirror milling processing program through the overall box bottom mirror milling surface scanning program compilation method, the overall box bottom mirror milling rough and fine processing tool path planning method and specific settings, and the overall box bottom mirror milling processing program generation process, further improves the processing efficiency and quality of the overall box bottom, and meets the carrying capacity and reliability of the launch vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 Generate a flow chart for the CNC program for the mirror milling of the overall bottom of the box of the present invention; Figure 2 It is a schematic diagram of the auxiliary programming surface of the present invention; Figure 3 A schematic diagram of the scanning profile programming range of the present invention; Figure 4 It is a schematic diagram of the profile scanning path planning of the present invention; Figure 5 It is a schematic diagram of the upper and lower contours of the auxiliary programming inner surface of the present invention; Figure 6 It is a schematic diagram of the rough processing area division method of the present invention; Figure 7 It is a schematic diagram of the rough machining program tool path of the present invention; Figure 8a and Figure 8b It is a schematic diagram of the method for planning the milling boundary and contour cutter gauge line at the thickening feature of the present invention; Fig. 9 A schematic diagram of the contour milling feed tool path planning of the present invention; Fig.10a and Fig.10b A schematic diagram of the number of intervals between machining tool paths and the direction of feed of the tool in the present invention; Figure 11a~Figure 11c This is a schematic diagram of a typical application scenario of the number of intervals between machining tool paths and the rule of feed direction of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0019] Example Figure 1The present invention provides a method for generating a NC program for the mirror milling of the entire bottom of a box, comprising the following steps: Step 1: Obtain the inner surface by extracting it from the theoretical model or drawing it according to the inner surface equation; Step 2: Use the inner surface in step 1 as the auxiliary programming surface to compile the surface scanning path; Step 3: Generate a surface scanning NC program through software post-processing according to the surface scanning path, and bring the surface scanning NC program into the software for simulation. If the simulation result fails, return to step 2 to recompile the surface scanning path. If the simulation result passes, go to step 4; Step 4: On the mirror milling device, call the surface scanning NC program in step 3 to scan the inner surface, obtain the surface point cloud data, and fit the point cloud data in the software to form an actual programming entity; Step 5: Extract all thickening / thinning area transition lines on the actual programming entity, and project them onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as machining features; Step 6: The process of milling the box bottom wall thickness from the blank thickness to the thickened area wall thickness is called rough machining. The rough machining area is divided to ensure that the tool centers of the two milling paths do not overlap; Step 7: Perform initial rough machining path planning on the auxiliary programming surface, and perform trajectory planning one by one according to the divided areas; Step 8: The process of milling the thickness of the bottom wall of the box from the thickened area to the thinned area is called finishing. The finishing area needs to be divided to ensure that the tool centers of the two milling paths do not overlap; Step 9: Perform initial finishing path planning on the auxiliary programming surface, and perform trajectory planning one by one according to the divided areas; Step 10: Generate a milling processing path according to the milling paths planned in steps 8 and 9; Step 11: Based on the milling processing path generated in step 10, generate a machining NC program through software post-processing.

[0020] Figure 2 In step 1, the inner surface is obtained by extracting it from the theoretical model or drawing it according to the inner surface equation. The inner surface should envelop the range of the mirror milling process, and the theoretical inner surface is offset or thickened according to the theoretical wall thickness of the thinning area, and the formed curved surface is used as the auxiliary programming surface.

[0021] Figure 3 This is a schematic diagram of the scanning profile programming range of the present invention, Figure 4The schematic diagram of the surface scanning path planning of the present invention. In step 2, the surface scanning path is planned on the auxiliary programming surface, the positive direction of the programming coordinate system Z axis is set upward, the origin of the coordinate system is the rotation center of the auxiliary programming surface, the origin of the Z direction is located on the upper surface of the physical tooling, and the inner surface is divided into four parts for scanning. The programming range of each scanned surface should cover one quarter of the auxiliary programming surface. According to the requirements of the scanning surface software image processing, the four sides should extend more than 20mm each, which is conducive to the software to sew the area. The direction of the scanning path starts from the milling lower contour line, and one of the intersections of the lower contour line and the contour line is used as the starting point. The upper contour line is gradually approached in a reciprocating way. The scanning track spacing is 50mm to 60mm, and the scanning programs of the remaining three quadrants are formed by the program of the first quadrant around the Z axis one by one at 90°.

[0022] Furthermore, in step 3, a surface scanning dedicated post-processor generated by UG NX POST BUILDER software is used to post-process the four scanning paths respectively to obtain four surface scanning NC programs.

[0023] Furthermore, in step 4, in Geomagic Design software, the actual programming entity is formed by fitting the scanned surface point cloud data file. After the surface is generated, the "body deviation" function can be used to confirm whether the generated surface meets the subsequent processing requirements. If not, it is returned for modification until the requirements are met and the solid model is exported. The solid model is a 3D model format file that can be read by UG software and contains model space coordinate information.

[0024] Figure 5 The figure is a schematic diagram of the upper and lower contours of the auxiliary programming inner surface of the present invention. In step 5, all thickening / thinning zone transition lines are extracted from the theoretical model and projected onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as processing features. According to the upper and lower boundaries of the truncation required by the process, in order to leave trimming margins for subsequent welding, according to the welding process requirements, the upper end (small end) is offset upward according to the truncation requirements to extract the contour, and the lower end (large end) is offset downward according to the truncation requirements to extract the contour, and projected onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as the upper and lower boundaries, respectively.

[0025] Figure 6It is a schematic diagram of the rough machining area division method of the present invention. In step 6, the process of milling the bottom wall thickness of the box from the blank thickness to the thickening area wall thickness is called rough machining. The single milling depth during rough machining does not exceed 3mm, and multiple milling can be performed according to the allowance. On the auxiliary programming surface, the rough machining area is divided according to the upper and lower boundaries, and is divided according to the latitude direction and the cutting time of a single area does not exceed 2h. In order to prevent repeated tool passing, resulting in unstable thickness measurement, the center of the machining tool needs not to be covered by the previous machining area. When the two tool paths are separated by 50% of the tool diameter, the tool center is just not covered by the previous machining area. When the two tool paths are separated by 100% of the tool diameter, the two tool paths are just not overlapped, and there is no uncut area. In addition, considering that the bottom teeth of the machining tool have their own R0.3mm fillet, the interval between the two tool paths will bring in the fillet radius for corresponding adjustment, and the boundaries of the two adjacent areas maintain a spacing of 50%+0.6mm to 100%-0.6mm tool diameter. (Consider the processing of rounded corner tools to ensure that the center of the tool is not covered or overlapped, and there is no residue during processing. 65% ensures stable thickness measurement, and 90% ensures that the cutting width is as large as possible while processing without residue.) Figure 7 The figure is a schematic diagram of the tool path of the rough machining program of the present invention. In step 7, the initial rough machining path planning is performed on the auxiliary programming surface, and the trajectory planning is performed one by one according to the divided areas. The rough machining program generally consists of two programs, the feed operation and the milling operation. In the program group view, the two operations constitute a program group, and the feed operation is located before the milling operation in the program group. The milling path length of the feed operation is 50mm to 100mm, generally along the meridian direction, and the end point is the starting point of the milling path. The feed and retract positions during rough machining are generally set in the +Y direction.

[0026] Figure 8a and Figure 8b It is a schematic diagram of the method for planning the milling boundary and contour cutter gauge line at the thickening feature of the present invention, Fig. 9 It is a schematic diagram of the contour milling feed tool path planning of the present invention. In step 8, the process of milling the thickness of the box bottom wall from the thickness of the thickened area to the thickness of the thinned area is called finishing. The single milling depth during finishing does not exceed 2mm. Multiple milling can be performed according to the allowance. When the final milling reaches the theoretical wall thickness, the milling depth does not exceed 1mm. According to the rule that the cutting time of a single area does not exceed 2h, there are areas without thickening / thinning transition lines. In areas with thickening / thinning transition lines, the thickening / thinning transition lines should be offset outward, and the offset is generally 50% of the contour milling tool diameter + 50% to 75% of the profile milling tool diameter. Among them, =50%~75% of the cutter diameter for profile milling, =65%~90% of the cutter diameter for profile milling, =50% of the contour milling tool diameter.

[0027] Furthermore, the initial finishing path planning is performed on the auxiliary programming surface, and the trajectory planning is performed one by one according to the divided areas. The finishing of the regional profile without thickening / thinning transition lines is consistent with the planned initial roughing path. For the finishing of the regional profile with thickening / thinning transition lines, the finishing program generally consists of a feed operation and one or more milling operations. In the program group view, all operations constitute a program group. The feed operation in the program group is located before the milling operation. The position between the milling operations should be arranged according to the rule that the end point of the previous program is the starting point of the next program.

[0028] Fig. 9 The figure is a schematic diagram of the tool path planning for the profile milling feed of the present invention. In step 8, the thickening / thinning transition profile finishing is generally planned along the contour line obtained by offsetting the contour outward by 50% of the tool diameter. The feed of the profile finishing can be planned using part of the contour line, and the path length of the feed operation is 50mm to 100mm, and the end point is the starting point of the milling path.

[0029] Furthermore, in step 7 and step 9, the feed operation and parameter settings are set according to Table 1, wherein the position and size of the sphere in parameter 6 should be able to envelop the auxiliary programming surface.

[0030] Table 1 Feed operation setting parameters

[0031] Furthermore, in step 7 and step 9, the milling operation uses the "variable contour milling" operation method, the trajectory adopts a reciprocating tool path, the path is planned along the latitude direction, and the spacing between the start and end of a single tool path is 65% to 90% of the tool diameter. The tool center at the upper and lower boundaries of milling should be just on the boundary line, the step distance between adjacent paths is 65% to 90% of the tool diameter, and overlapping and crossing between tool paths are not allowed. At the same time, the tool path is not allowed to have two or more advances / retracts. The parameters are set according to Table 2.

[0032] Table 2 Milling operation parameter setting table

[0033] Fig.10a and Fig.10b This is a schematic diagram of the number of intervals between machining tool paths and the direction of feed of the present invention. Figure 11a~Figure 11c The figure is a typical application diagram of the machining tool path interval number and feed direction rule of the present invention. In step 7 and step 9, the milling operation and tool path planning have the following rule: when the machining tool path interval number is an even number, the tool cutting feed direction is consistent with the tool cutting feed end point direction; conversely, when the machining tool path interval number is an odd number, the tool cutting feed direction is opposite to the tool cutting feed end point direction.

[0034] Furthermore, in step 10, the actual programming entity generated in step 4 is selected as the "component" of all the above operations to generate a milling process path.

[0035] Furthermore, in step 11, all machining program groups are post-processed respectively using the mirror milling post-processor generated by UG NX POST BUILDER software to obtain all CNC machining programs.

[0036] A method for generating a mirror image milling processing program for an integral box bottom proposed in the present invention stipulates the steps and methods for generating a tool path for the mirror image milling processing of the integral box bottom, improves the standardization of the generation of the mirror image milling processing program for the integral box bottom, further improves the processing efficiency and quality of the integral box bottom, and meets the carrying capacity and reliability of the launch vehicle.

[0037] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0038] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for generating a mirror image milling program for an integral box bottom, characterized in that: include: Step 1: Obtain the inner surface by extracting it from the theoretical model or drawing it according to the inner surface equation; Step 2: Use the inner surface in step 1 as the auxiliary programming surface to compile the surface scanning path; Step 3: Generate a surface scanning NC program through software post-processing according to the surface scanning path, and bring the surface scanning NC program into the software for simulation. If the simulation result fails, return to step 2 to recompile the surface scanning path. If the simulation result passes, go to step 4; Step 4: On the mirror milling device, call the surface scanning NC program in step 3 to scan the inner surface, obtain the surface point cloud data, and fit the point cloud data in the software to form an actual programming entity; Step 5: Extract all thickening / thinning area transition lines on the actual programming entity, and project them onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as machining features; Step 6: The process of milling the box bottom wall thickness from the blank thickness to the thickened area wall thickness is called rough machining. The rough machining area is divided to ensure that the tool centers of the two milling paths do not overlap; Step 7: Perform initial rough machining path planning on the auxiliary programming surface, and perform trajectory planning one by one according to the divided areas; Step 8: The process of milling the thickness of the box bottom wall from the thickened area to the thinned area is called finishing. The finishing area needs to be divided to ensure that the tool centers of the two milling paths do not overlap; Step 9: Perform initial finishing path planning on the auxiliary programming surface, and perform trajectory planning one by one according to the divided areas; Step 10: Generate a milling processing path according to the milling paths planned in steps 8 and 9; Step 11: Based on the milling processing path generated in step 10, generate a machining NC program through software post-processing.

2. The method for generating a mirror image milling program for an integral box bottom according to claim 1, characterized in that: In step 1, the inner surface is obtained by extracting it from the theoretical model or drawing it according to the inner surface equation. The inner surface envelops the range of mirror milling processing, and the theoretical inner surface is offset or thickened according to the theoretical wall thickness of the thinning area. The formed surface is used as an auxiliary programming surface.

3. The method for generating a mirror image milling program for an integral box bottom according to claim 2, characterized in that: In step 2, plan the surface scanning path on the auxiliary programming surface, set the programming coordinate system Z axis positive direction upward, the coordinate system origin is the auxiliary programming surface rotation center, the Z direction origin is located on the upper surface of the physical tooling, the inner surface is divided into four parts for scanning, each scanning surface programming range covers a quarter of the auxiliary programming surface, and extends 20mm on all sides. The direction of the scanning path starts from the milling lower contour line, and one of the intersections of the lower contour line and the contour line is used as the starting point, and gradually approaches the upper contour line in a reciprocating manner. The scanning track spacing is 50mm to 60mm, and the scanning programs of the remaining three quadrants are formed by the program of the first quadrant around the Z axis in an array of 90°.

4. The method for generating a mirror image milling program for an integral box bottom according to claim 3, characterized in that: In step 3, the surface scanning dedicated post-processor generated by UG NX POST BUILDER software is used to post-process the four scanning paths respectively to obtain four surface scanning NC programs; In step 11, all machining program groups are post-processed respectively using the mirror milling post-processor generated by UG NX POST BUILDER software to obtain all CNC machining programs.

5. The method for generating a mirror image milling program for an integral box bottom according to claim 4, characterized in that: In step 4, in Geomagic Design software, the actual programming entity is formed according to the scanned surface point cloud data file; the point cloud file is processed by noise elimination, sampling, smoothing, triangulation and surface fitting operations. After the surface is generated, the body deviation function is used to confirm whether the generated surface meets the subsequent processing requirements. If not, it is returned for modification until the requirements are met and the solid model is exported. The solid model is a three-dimensional model format file that can be read by UG software and contains model space coordinate information.

6. The method for generating a mirror image milling program for an integral box bottom according to claim 5, characterized in that: In step 5, all thickening / thinning zone transition lines are extracted from the theoretical model and projected onto the auxiliary programming surface along the normal vector of the auxiliary programming surface as machining features; According to the upper and lower boundaries of the truncation process requirements, the small end is offset upward by 5mm to 10mm according to the truncation requirements to extract the contour, and the large end is offset downward by 5mm to 10mm according to the truncation requirements to extract the contour, and the normal vector of the auxiliary programming surface is projected onto the auxiliary programming surface as the upper and lower boundaries respectively.

7. The method for generating a mirror image milling program for an integral box bottom according to claim 6, characterized in that: In step 6, the process of milling the thickness of the box bottom wall from the blank thickness to the wall thickness of the thickened area is called rough machining. The single milling depth during rough machining does not exceed 3mm, and multiple milling is performed according to the allowance. On the auxiliary programming surface, the rough machining area is divided according to the upper and lower boundaries, and the division is carried out according to the latitude direction and the cutting time of a single area does not exceed 2h; the boundary between two adjacent areas maintains a spacing of 50%+0.6mm to 100%-0.6mm tool diameter; In step 7, the initial rough machining path planning is performed on the auxiliary programming surface, and the trajectory planning is performed one by one according to the divided areas. The rough machining program consists of two programs: the feed operation and the milling operation. In the program group view, the two operations constitute a program group. The feed operation in the program group is located before the milling operation. The milling path length of the feed operation is 50mm~100mm, along the meridian direction, and the end point is the starting point of the milling path. During rough machining, the feed and retract positions are set in the +Y direction.

8. The method for generating a mirror image milling program for an integral box bottom according to claim 7, characterized in that: In step 8, the process of milling the thickness of the box bottom wall from the thickened area to the thinned area is called finishing. The single milling depth during finishing does not exceed 2mm. Multiple milling is performed according to the allowance. The final milling depth does not exceed 1mm when the theoretical wall thickness is reached. The area is divided according to the rule that the cutting time of a single area does not exceed 2h. There is no thickening / thinning transition line in the area; the thickening / thinning transition line is offset outward in the area with a thickening / thinning transition line, and the offset is 50% of the contour milling tool diameter + 50% to 75% of the profile milling tool diameter. In step 9, the initial finishing path planning is performed on the auxiliary programming surface, and the trajectory planning is performed one by one according to the divided areas; the surface finishing of the area without thickening / thinning transition lines is consistent with the planned initial roughing path; the surface finishing of the area with thickening / thinning transition lines, the finishing program consists of a feed operation and one or more milling operations. In the program group view, all operations constitute a program group. The feed operation in the program group is located before the milling operation, and the positions between the milling operations are arranged according to the rule that the end point of the previous program is the starting point of the next program.

9. The method for generating a mirror image milling program for an integral box bottom according to claim 8, characterized in that: In step 7 and step 9, the milling operation uses a variable contour milling operation method, the trajectory adopts a reciprocating tool path, the path is planned along the latitude direction, and the spacing between the start and end points of a single tool path is 65% to 90% of the tool diameter; the tool center at the upper and lower boundaries of milling is on the boundary line, the step distance between adjacent paths is 65% to 90% of the tool diameter, the tool paths do not overlap or cross, and the tool path does not have two or more advances / retracts; When the number of intervals of the machining tool path is an even number, the tool cutting feed direction is consistent with the direction of the tool cutting feed end point; conversely, when the number of intervals of the machining tool path is an odd number, the tool cutting feed direction is opposite to the direction of the tool cutting feed end point.

10. A system for generating a program for the mirror milling of an integral bottom of a box, characterized in that: A method for generating a program for the mirror milling of an integral box bottom as described in any one of claims 1 to 9 is adopted.

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