A method for milling large-diameter conical parts with uniform wall thickness

Abstract

The present application discloses a method for milling the wall thickness of a large-diameter conical part mesh. The method comprises the following steps: S1: fixing the part to be machined with a fixture; S2: measuring the outer surface of the part to be machined to obtain the deviation value of the outer surface position relative to the theoretical position, i.e., the surface measurement parameter points; S3: performing rotational modeling according to the theoretical outer shape of the part to be machined to obtain a theoretical part, segmenting the theoretical part by longitude and latitude curves and longitude and latitude and longitude point sets to obtain a coordinate point cloud set; S4: importing the surface measurement parameter points into the point cloud set to obtain a point cloud deviation set, and reverse modeling and reconstructing the point cloud deviation set to obtain a parameterized real-time surface; S5: projecting the mesh boundary of the design model onto the real-time surface and performing mesh CNC parameter replication to obtain a machined surface with mesh characteristics; and S6: milling the outer surface of the part to be machined according to the machined surface. The method can adapt to the irregular deformation characteristics of the surface and meet the requirements of mesh and wall thickness milling of conical bottom parts.

Description

Technical Field

[0001] The present application relates to the technical field of conical part milling methods, and in particular to a method for milling large-diameter conical parts with grid-like wall thickness. Background Art

[0002] A conical part has a 45-degree cone surface, a large end diameter of about 4600mm, a small end diameter of 2000mm, a height of 1200mm, a maximum thickness of 20mm, and a mesh thickness of 4mm. It is a typical weak-rigidity thin-walled product. Figure 1 As shown. The existing processing technology is "turning uniform thinning + milling mesh opening". After the turning and thinning process, the product's hoisting, flipping, clamping, and internal stress release will cause irregular deformation of the surface, making mesh uniform thickness milling extremely difficult. At the same time, the clamping stiffness problem in the milling process directly determines the accuracy of the milling mesh. At present, due to factors such as its structural characteristics and process flow, uniform thickness milling of large-diameter conical parts is extremely difficult.

[0003] There are two main existing methods for milling the wall thickness of large-diameter conical bottom parts: 1. Surface assurance method; 2. Grid adjustment method;

[0004] Prior Art 1: Because the residual thickness of the mesh is formed by both the inner surface and the machined profile, milling accuracy is determined by the deviation of the inner surface. Therefore, profile assurance methods are used to reduce profile deviation and achieve milling accuracy. Commonly used measures include clamping, using a monolithic jig or suction cups to hold the profile in place. However, the profile assurance effect during clamping is often poor, with problems such as loose contact with the jig and insufficient suction force making it difficult to achieve milling accuracy.

[0005] Existing technology 2: The mesh adjustment method involves milling a single mesh individually while taking into account surface deviations. Often, if the surface deviation of a single mesh is less than the thickness tolerance, milling the single mesh can meet the required wall thickness tolerance. However, this method has significant limitations on mesh size; the surface deviation of larger meshes often exceeds the thickness tolerance. Furthermore, single-mesh milling is extremely inefficient and does not meet part processing requirements. Summary of the Invention

[0006] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, provide a method for equal wall thickness milling of large-diameter conical part grids, design a conical double-point discrete support shape-preserving method, and based on this, design a parametric sampling compensation grid milling method, which can realize equal wall thickness milling of large-diameter conical grids.

[0007] The technical solution of the present invention is:

[0008] A method for milling a large-diameter tapered part mesh with a constant wall thickness, comprising:

[0009] S1: Use a fixture to fix the tapered part to be processed;

[0010] S2: Establish a workpiece coordinate system, measure the outer surface of the part to be processed, and obtain the deviation value of the outer surface position relative to the theoretical position, that is, the surface measurement parameter point;

[0011] S3: Perform rotational modeling according to the theoretical shape of the part to be processed to obtain a theoretical part, establish the same workpiece coordinate system as in step S2, perform longitude and latitude curve segmentation and longitude and latitude point set segmentation on the outer surface of the theoretical part, and obtain a coordinate point cloud set;

[0012] S4: Importing the measured parameter points of the profile into the point cloud set to obtain a point cloud deviation set, and reversely modeling and reconstructing the point cloud deviation set to obtain a parameterized real-time profile;

[0013] S5: Projecting the mesh boundary of the design model onto the real-time surface and copying the mesh CNC parameters to obtain a machining surface with mesh features;

[0014] S6: Mill the outer surface of the part to be processed according to the processing surface.

[0015] The fixture includes a base, a large end support ring, a small end support ring, and a reinforcing rod. The large end support ring has a larger outer diameter than the small end support ring. The large end support ring and the small end support ring are coaxially arranged and positioned below the small end support ring. The base supports the large end support ring, and the reinforcing rod supports the small end support ring. The small diameter end of the tapered part to be processed is fixed to the small end support ring via multiple first clamping devices, and the large diameter end of the tapered part to be processed is fixed to the large end support ring via multiple second clamping devices.

[0016] The first clamping device includes a first adapter plate, a pressing screw and a pressing pad. The first adapter plate is fixed to the small end support ring by a fastening screw. The pressing screw is threadedly connected to the first adapter plate. The axis of the pressing screw is parallel to the outer busbar of the small end support ring. The pressing screw and the first adapter plate can be adjusted along their own axis directions. The pressing pad is fixedly connected to the pressing screw thread to increase the pressing contact area of ​​the conical part. The pressing pad is connected to the limiting block. The limiting block is located on the side of the part to be processed away from the small end support ring.

[0017] The second clamping device includes a second adapter plate, an adjusting screw, and an adjusting block. The second adapter plate is fixed to the base by a fastening screw. The adjusting screw is threadedly connected to the second adapter plate. The adjusting screw can be adjusted horizontally on the second adapter plate. The adjusting block is fixedly connected to the large end support ring. The adjusting block is slidingly connected to the base along the radial direction of the base. The adjusting block provides a tightening force on the large end support ring. A long hole is opened on the adjusting block. The fixing screw passes through the long hole and is threadedly connected to the base. After adjustment, the adjusting block is fixed to the base using the fixing screw.

[0018] First, use the second clamping device to tighten the large end support ring, and then use the second clamping device at the upper end to press the product downward at an angle. The lower it is pressed, the tighter the part to be processed becomes until the part to be processed is stably fixed.

[0019] The clamp is connected with a tool lifting ring.

[0020] The parts to be processed are parts that have been processed by lathe.

[0021] In step S6, the milling process is layered milling.

[0022] The step S6 comprises:

[0023] S61: After performing the first layer of milling, measuring the thickness of the part to be processed, obtaining the difference between the thickness of the part to be processed and the theoretical thickness after milling, and obtaining the tolerance value;

[0024] S62: When the tolerance value is not greater than the design tolerance, the second layer milling process is directly performed; when the tolerance value is greater than the design tolerance, steps S2-S5 are repeated until the milling remaining thickness meets the design requirements, and the processing is completed.

[0025] The Z axis of the workpiece coordinate system is parallel to the axis of the part to be machined. When measuring the deviation value in step S2, the measurement margin is evenly distributed at least 50 measurement points in the X and Z directions.

[0026] In summary, this application has at least the following beneficial technical effects:

[0027] The grid milling of large-diameter conical bottom parts is affected by factors such as surface deviation and clamping stiffness. There are problems such as difficulty in ensuring wall thickness accuracy and irregular deformation during milling. To address this, this patent designs a conical double-point discrete support shape-preserving method, and based on this, designs a parametric sampling compensation grid milling method, which can adapt to the irregular deformation characteristics of the surface and meet the wall thickness milling requirements of the conical bottom part grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of a tapered part in the background technology of this application;

[0029] Figure 2 Schematic diagram of the structure of the clamp in the embodiment of the present application;

[0030] Figure 3 This is a schematic structural diagram of the first pressing device in an embodiment of the present application;

[0031] Figure 4 This is a schematic structural diagram of the second pressing device in an embodiment of the present application;

[0032] Figure 5Schematic diagram of the process of the parameterized sampling compensation grid milling method in an embodiment of the present application;

[0033] Figure 6 Schematic diagram of the XZ direction during the profile measurement process in an embodiment of the present application;

[0034] Figure 7 This is a schematic diagram of the longitude and latitude curve segmentation, longitude and latitude point set segmentation, and modeling and reconstruction in the embodiment of this application;

[0035] Figure 8 This is a schematic diagram of projecting the mesh boundary of the design model onto the real-time surface in an embodiment of the present application, and the direction of the arrow in the figure is the projection direction.

[0036] Description of reference numerals: 1. Parts to be processed;

[0037] 2. Clamp; 21. Base; 22. Small end support ring; 23. Large end support ring; 24. Reinforcement support rod; 25. Tool lifting ring;

[0038] 3. First pressing device; 31. First adapter plate; 32. Pressing screw; 33. Pressing pad; 34. Limiting block; 35. Pad;

[0039] 4. Second pressing device; 41. Second adapter plate; 42. Adjusting screw; 43. Adjusting block; 44. Long hole; 45. Fixing screw. DETAILED DESCRIPTION

[0040] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] The embodiment of the present application discloses a method for milling a large diameter tapered part grid with equal wall thickness, such as Figure 1 As shown, the following steps are included:

[0042] S1: Fixing the tapered workpiece 1 with a fixture 2. Specifically: a tapered double-point discrete support shape-preserving method.

[0043] The part 1 to be processed is a part that has been processed by lathe.

[0044] When clamping the part 1 to be processed, use Figure 2The fixture 2 shown is used for clamping and shape preservation. The fixture 2 includes a base 21, a large end support ring 23, a small end support ring 22, and a reinforcing strut 24. The large end support ring 23 has a larger outer diameter than the small end support ring 22. The large end support ring 23 is coaxial with the small end support ring 22 and is located below the small end support ring 22. The base 21 is used to support the large end support ring 23, and the reinforcing strut 24 is used to support the small end support ring 22. The small diameter end of the tapered workpiece 1 to be machined is fixed to the small end support ring 22 by multiple first clamping devices 3, and the large diameter end of the tapered workpiece 1 to be machined is fixed to the large end support ring 23 by multiple second clamping devices.

[0045] like Figure 3 As shown, the first clamping device 3 includes a first adapter plate 31, a pressing screw 32, and a pressing pad 33. The first adapter plate 31 is fixed to the small end support ring 22 by a fastening screw. The pressing screw 32 is threadedly connected to the first adapter plate 31. The axis of the pressing screw 32 is parallel to the outer busbar of the small end support ring 22. The pressing screw 32 and the first adapter plate 31 can be adjusted along their own axis. The pressing pad 33 is threadedly fixedly connected to the pressing screw 32 to increase the contact area of ​​the tapered part. The pressing pad 33 is connected to a limit block 34. The limit block 34 is located on the side of the workpiece 1 to be processed away from the small end support ring 22. The outer side of the small end support ring 22 is detachably connected to a pad by bolts. The small end support ring 22 is an integral structure with a fixed size. If the size is not suitable, the pad of different thickness can be replaced.

[0046] like Figure 4 As shown, the second clamping device 4 includes a second adapter plate 41, an adjusting screw 42 and an adjusting block 43. The second adapter plate 41 is fixed to the base 21 by a fastening screw. The adjusting screw 42 is threadedly connected to the second adapter plate 41. The adjusting screw 42 can be adjusted horizontally on the second adapter plate 41. The adjusting block 43 is fixedly connected to the large end support ring 23. The large end support ring 23 is arranged in blocks. The adjusting block 43 is slidably connected to the base 21 along the radial direction of the base 21. The adjusting block 43 provides a tightening force on the large end support ring 23. A long hole 44 is opened on the adjusting block 43. The fixing screw 45 passes through the long hole 44 and is threadedly connected to the base 21. After adjustment, the adjusting block 43 is fixed to the base 21 using the fixing screw 45.

[0047] To facilitate the determination of the center of rotation, the milling fixture 2 is designed with a circular base. The center of rotation during milling is the center of the base 21. The remaining clamping devices and support rings are designed based on the rotation center of the base 21. To ensure the overall structural rigidity of the fixture, the fixture is designed with reinforcing struts 24 staggered horizontally and vertically. Furthermore, local support rings are designed at the large and small ends of the fixture. The profiles of the large end support ring 23 and the small end support ring 22 are consistent with the internal profile of the part, achieving a double-point discrete shape retention effect.

[0048] To ensure reliable product positioning and prevent displacement during processing, six evenly spaced clamping devices are designed on the small end of the fixture. These clamping devices are secured to the small end support ring 22 using screws. Manual downward pressure is applied along the taper generatrix using a screw connection. Combined with the self-locking properties of the tapered contact surface, this ensures secure product clamping. To avoid interference caused by protruding screws, all connection holes are countersunk. Four lifting rings 25 are provided to facilitate lifting the fixture.

[0049] After step S1 is completed, parameterized sampling compensation grid milling is performed.

[0050] The conical double-point discrete support shape-preserving method has a certain adjustment effect on the inner surface deviation, but it still cannot meet the requirements of constant wall thickness milling. Therefore, this patent designs a parametric sampling compensation grid milling method based on the above clamping characteristics. Its process is as follows: Figure 7 The parametric sampling compensation mesh milling method mainly consists of three steps: surface measurement, shape parameter modeling, and mesh feature parameter programming.

[0051] Parametric sampling compensation grid milling method, specifically including:

[0052] S2: Establish a workpiece coordinate system, with the Z axis of the workpiece coordinate system parallel to the axis of the part 1 to be processed, measure the outer surface of the part 1 to be processed, and obtain the deviation value of the outer surface position relative to the theoretical position, that is, the surface measurement parameter point.

[0053] Specifically, the surface measurement mainly uses the measurement program with a table to record the deviation of the top surface of the grid, such as Figure 8 As shown in the figure, since the surface deviations of different cone-bottom parts are different, the measurement margins are also different. The initial measurement margins are evenly distributed at 50 measurement points in the X and Z directions, and the deviation is recorded as Hij, where i represents the i-th starting measurement point of x and j represents the j-th starting measurement point of z. According to this measurement, i*j deviation values ​​should be obtained, that is, i*j surface measurement parameter points.

[0054] S3: Perform rotational modeling according to the theoretical shape of the part 1 to be processed to obtain a theoretical part, establish the same workpiece coordinate system as in step S2, perform longitude and latitude curve segmentation and longitude and latitude point set segmentation on the outer surface of the theoretical part, and obtain a coordinate point cloud set.

[0055] Specifically, the parametric modeling of the contour surface mainly includes the transformation from theoretical contour features to parametric contour characteristics that can be adjusted based on the measurement points. First, rotational modeling is performed according to the theoretical contour, and the longitude and latitude curves and longitude and latitude point sets are segmented based on the i and j margins to obtain a coordinate point cloud set. At the same time, in order to ensure the rapid real-time update of the contour surface based on the measurement results, the point cloud of the smallest unit needs to be individually parameterized with the deviation value, with the initial value Hij = 0. The parametric contour surface is then reconstructed by reverse modeling using the longitude and latitude points. As shown in Table 1:

[0056] Table 1 Point cloud deviation set

[0057] NAME FORMULA VALUE UNITS TYPE COMMENT H11 8 8 mm Number H12 8 8 mm Number H13 8 8 mm Number H14 8 8 mm Number H15 8 8 mm Number H16 8 8 mm Number H17 8 8 mm Number H18 8 8 mm Number H19 8 8 mm Number H1A 8 8 mm Number H21 8 8 mm Number H22 8 8 mm Number H23 8 8 mm Number

[0058] S4: Import the surface measurement parameter points into the point cloud set to obtain the point cloud deviation set, and reversely model and reconstruct the point cloud deviation set to obtain the parameterized real-time surface.

[0059] Specifically, as shown in the table above, the surface measurement parameter points are imported into the point cloud set to obtain the point cloud deviation set, and the point cloud deviation set is reversely modeled and reconstructed to obtain the parameterized real-time surface.

[0060] S5: After projecting the mesh boundary of the design model onto the real-time surface and copying the mesh CNC parameters, a machining surface with mesh features is obtained.

[0061] Specifically, mesh feature parameter programming projects the mesh boundary of the design model onto a new parametric surface and copies the mesh CNC parameters, so that the CNC program can be updated in real time according to the parametric surface.

[0062] S6: performing layered milling processing on the outer surface of the part 1 to be processed according to the processing profile, including the following steps:

[0063] S61: After performing the first layer milling, measuring the thickness of the part 1 to be machined, obtaining the difference between the thickness of the part 1 to be machined and the theoretical thickness after milling, and obtaining the tolerance value;

[0064] S62: When the tolerance value is not greater than the design tolerance, the second layer milling process is directly performed; when the tolerance value is greater than the design tolerance, steps S2-S5 are repeated until the milling remaining thickness meets the design requirements, and the processing is completed.

[0065] Although the present invention is disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A method for milling large-diameter tapered parts with equal wall thickness, characterized by: include S1: Using a fixture (2) to fix the tapered part to be processed (1); The clamp (2) comprises a base (21), a large end support ring (23), a small end support ring (22), and a reinforcing support rod (24); the outer diameter of the large end support ring (23) is larger than that of the small end support ring (22); the large end support ring (23) and the small end support ring (22) are coaxially arranged, and the large end support ring (23) is located below the small end support ring (22); the base (21) is used to support the large end support ring (23); the reinforcing support rod (24) is used to support the small end support ring (22); the small diameter end of the conical part to be processed (1) is fixed to the small end support ring (22) by a plurality of first clamping devices (3); and the large diameter end of the conical part to be processed (1) is fixed to the large end support ring (23) by a plurality of second clamping devices (4); S2: Establishing a workpiece coordinate system, measuring the outer surface of the part to be processed (1), and obtaining the deviation value of the outer surface position relative to the theoretical position, i.e., the surface measurement parameter point; S3: Performing rotation modeling according to the theoretical shape of the part to be processed (1) to obtain a theoretical part, establishing the same workpiece coordinate system as in step S2, performing longitude and latitude curve segmentation and longitude and latitude point set segmentation on the outer surface of the theoretical part, and obtaining a coordinate point cloud set; S4: Importing the measured parameter points of the profile into the point cloud set to obtain a point cloud deviation set, and reversely modeling and reconstructing the point cloud deviation set to obtain a parameterized real-time profile; S5: Projecting the mesh boundary of the design model onto the real-time surface and copying the mesh CNC parameters to obtain a machining surface with mesh features; S6: milling the outer surface of the part to be processed (1) according to the processing profile; Step S6 includes: S61: After performing the first layer of milling, measuring the thickness of the part to be processed (1), obtaining the difference between the thickness of the part to be processed (1) and the theoretical thickness after milling, and obtaining the tolerance value; S62: When the tolerance value is not greater than the design tolerance, the second layer milling process is directly performed; when the tolerance value is greater than the design tolerance, steps S2-S5 are repeated until the milling remaining thickness meets the design requirements, and the processing is completed.

2. A method for milling a large-diameter tapered part grid with equal wall thickness according to claim 1, characterized in that: The fixture (2) fixes the small diameter end and the large diameter end of the tapered part to be processed (1) to perform double-point discrete support and shape preservation.

3. The method for milling a large-diameter tapered part grid with equal wall thickness according to claim 1, characterized in that: The first pressing device (3) comprises a first adapter plate (31), a pressing screw (32) and a pressing pad (33); the first adapter plate (31) is fixed to the small end support ring (22) by a fastening screw; the pressing screw (32) passes through and is threadedly connected to the first adapter plate (31); the axis of the pressing screw (32) is parallel to the outer busbar of the small end support ring (22); the pressing pad (33) is connected to the end of the pressing screw (32) to increase the pressing contact area of ​​the conical part; the pressing pad (33) is connected to a limiting block (34); the limiting block (34) is located on the side of the part to be processed (1) away from the small end support ring (22).

4. The method for milling a large-diameter tapered part grid with uniform wall thickness according to claim 1, characterized in that: The second pressing device (4) includes a second adapter plate (41), an adjusting screw (42), and an adjusting block (43). The second adapter plate (41) is fixed to the base (21) by a fastening screw. The adjusting screw (42) is threadedly connected to the second adapter plate (41). The adjusting screw (42) can be adjusted horizontally on the second adapter plate (41). The adjusting block (43) is fixedly connected to the large end support ring (23). The adjusting block (43) is slidably connected to the base (21) along the radial direction of the base (21). The adjusting block (43) provides a tightening force acting on the large end support ring (23). A long hole (44) is provided on the adjusting block (43). The fixing screw (45) passes through the long hole (44) and is threadedly connected to the base (21). After adjustment, the fixing screw (45) is used to fix the adjusting block (43) to the base (21).

5. The method for milling a large-diameter tapered part grid with uniform wall thickness according to claim 1, characterized in that: The clamp (2) is connected to a tool lifting ring (25).

6. The method for milling a large-diameter tapered part grid with uniform wall thickness according to claim 1, characterized in that: The part to be processed (1) is a part that has been processed by lathe.

7. The method for milling a large-diameter tapered part grid with uniform wall thickness according to claim 1, characterized in that: In step S6, the milling process is layered milling.

8. The method for milling a large-diameter tapered part grid with uniform wall thickness according to claim 1, characterized in that: The Z axis of the workpiece coordinate system is parallel to the axis of the part to be processed (1). When measuring the deviation value in step S2, the measurement margin is evenly distributed at least 50 measurement points in the X and Z directions.

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