Machining process of offshore large megawatt direct-drive fan main shaft

Abstract

The machining technology comprises the following technological steps that firstly, vertical lathe machining is conducted, a reference surface A is upward, a plane and a flange are roughly and finely turned to the drawing size through a vertical tool rest, a reference surface D and a flange on the same side are roughly turned through a side tool rest, and a technological reference is finely machined to the drawing size at a reference position B; keeping the posture A reference surface upward, positioning the workpiece by using the D reference surface, and machining a reference A flange surface threaded hole bottom hole and a pin hole bottom hole; keeping the attitude A reference surface upward, and processing a pin hole of the A reference surface, an inner cavity inclined surface and a lug by using a boring machine tool; turning over the D datum upwards, and boring and milling the pin hole, the threaded hole and the through hole to the drawing size by means of a boring machine tool; and keeping the posture D reference upward, and finely turning the D reference end to the drawing size by virtue of a boring machine tool. And through the strategy of six-sequence centralized machining, the workpiece turning-over frequency is reduced, and the transfer damage risk is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to a machining process of a large-megawatt offshore direct-drive wind turbine main shaft, and belongs to the technical field of wind power main shaft product casting machining. BACKGROUND

[0002] With the development of the wind power industry towards large-scale and high efficiency, the power of offshore direct-drive wind turbine generators is continuously improved, and higher requirements are put forward for the manufacturing process of key components. The main shaft and tower structure of large-scale offshore direct-drive wind turbine generators abroad are complex and large in size (the diameter of the main shaft is more than 6700 mm, and the height is more than 3400 mm), and new structures such as an intermediate flange surface, a complex cavity and a deep cavity hole are added. The traditional machining method faces the following difficulties: 1. Overweight workpiece: the weight of a single piece far exceeds the lifting capacity of the existing crane, and the transportation and turning over are difficult, which may lead to workpiece damage or safety accidents. Since the workpiece is heavy, it is difficult to lift and turn over, and the surface quality requirement of the workpiece is strict, and scratching and hair damage are not allowed. Therefore, the process arrangement preferably follows the process concentration principle, reduces the number of transportation and turning over between processes, and places the key processes as far back as possible to reduce the impact of process transportation and turning over on quality.

[0003] 2. Complex structure: the depth of the inner cavity is 2300 mm, and the position degree of the inclined plane and the pin hole is high (±0.2 mm), and the existing tools and accessories cannot meet the machining requirements.

[0004] 3. Process limitation: multiple reference surface machining (A / D reference), deep hole boring, high-precision pin hole matching and the like need to be considered, and the dispersion of processes may accumulate errors.

[0005] 4. Surface quality requirement: wind power components are strictly prohibited from scratching and scratching, and traditional multiple lifting and turning over may cause surface damage.

[0006] At present, there is no mature processing scheme for the same level of components in China, and only a prototype has been trial-produced abroad, and a high-efficiency and high-precision special machining process is urgently needed. SUMMARY

[0007] In view of the problems existing in the prior art, the application provides a machining process of a large-megawatt offshore direct-drive wind turbine main shaft, thereby solving the above technical problems.

[0008] In order to achieve the above purpose, the technical scheme adopted by the application is as follows: a machining process of a large-megawatt offshore direct-drive wind turbine main shaft, comprising the following process steps: Step 1: two cranes are used to jointly lift the workpiece when the workpiece is placed on the machine tool, the maximum distance between the two cranes is less than 8 meters, and the minimum distance between the end beams is greater than 2 meters. In order to ensure the safety of lifting, a bridge type special lifting tool is designed and made, and the workpiece is placed on the workbench of the machining center through the lifting tool. Step Two: First-stage machining on an vertical lathe. With datum A facing upwards, the workpiece is supported on the CNC vertical lathe by the boss plane of the middle web plate. The effective support diameter is less than 3550mm, which is the maximum diameter of the support bearing of the machine tool table. The vertical tool post rough and finish turns the plane and flange to the drawing size, the side tool post rough turns the D datum surface and the flange on the same side, and finishes one cut at datum B, but the size is less than the drawing size. Step 3: Second stage, boring machine processing Keep the first process orientation A reference surface upward, use tooling, the tooling has a maximum effective contact diameter of 3500mm with the boring machine table, the maximum diameter of the table support ring is 3400mm, the tooling weight is less than 10 tons, the workpiece is positioned with the first process D reference plane, the machining reference A flange face threaded hole through hole, the four sides are machined, and the pin hole is drilled. Step 4: Three-stage, SORALUCE milling and turning machining With the second-order orientation A facing upwards, use a boring machine fixture to machine the pin hole, inner cavity bevel, and latch on the A datum surface; Step 5: Fourth stage, boring machine processing 2, Turn the machine over so that reference point D is facing upwards, and use a boring machine fixture to bore and mill the pin holes, threaded holes, and through holes to the dimensions shown in the drawing. Step Six: Fifth Sequence: Vertical Lathe Machining II With the fourth position D datum facing upwards, use a boring machine fixture to finish machine the D datum end to the dimensions shown in the drawing.

[0009] Furthermore, in step one, the workpiece is smoothly hoisted onto the fixture, contacts the adjustable support on the fixture, and then the common center of the upper and lower outer circles is corrected to be within 2mm, the error of the four symmetrical points of the outer circle is rechecked to be less than 2mm, and then the workpiece is locked.

[0010] Furthermore, in step two, this step is the rough and finish turning stage of the workpiece. First, it is necessary to determine the machining allowance in the "Z" direction; according to the dimensions and positions on the drawing, use a height gauge to measure and the machine tool to set the tool to confirm the machining allowance of the upper and lower end faces, taking into account the allowance of each machining surface; According to the drawings, machine each part to the dimensions. When turning the inner hole Φ4490, pay attention to the risk of machining the blank body. If the blank body is machined, use the oblique infeed method to avoid damage to the tool, machine tool and workpiece. Chamfer all edges and corners. The outer dimensions of the upper part of the rough and finish machine are precision machined to the dimensions specified in the drawings. For the rough machining of the lower part, leave a 2mm finishing allowance on each side according to the dimensions required in the drawing. The lower reference plane of the reverse end is used to control dimensions.

[0011] Further, in step three, the outer circle area of the large end and the φ75 hole of the small end groove are processed to the drawing size by using a boring machine, wherein the outer circle area of the large end and the intermediate step surface hole are all processed to the drawing size, except that the φ50 and φ20 pin holes are not processed, and the small end part is processed to remove the excess, with a single side of 2mm left for finishing.

[0012] Further, the workpiece is placed on the equal height block of the tooling to correct the workpiece with the processed outer circle, correct the workpiece with the blank shape, take into account the dimensions of the inner cavity each lap, mill the large end outer circle to the size; drill and tap each screw hole on the large end surface to the size, drill and tap each screw hole on the step surface to the size, rough mill the small end outer circle groove to the size, leave a single side of 2mm for finishing, mill the 4X2XD75±0.2 hole to the size, and chamfer each hole mouth to the size.

[0013] Further, in step four, the workpiece is placed on the equal height block of the tooling to align the workpiece center with the outer circle, straighten the workpiece with the D45 hole reference hole, press the workpiece tightly, finish boring the p50H7 and p20G8 pin holes to the size, finish processing the inner cavity each lap surface and all holes on the surface to the size, and chamfer each hole mouth to the size.

[0014] Further, in step five, after turning over, the workpiece is placed on the equal height block of the tooling to correct the workpiece with the D45 hole positioning, press the workpiece tightly, drill and tap the 2X158XM42 screw hole on the D reference surface to the size, process the inner cavity boss each lap surface and all holes on the surface to the size, process the inner cavity side boss surface and screw hole to the size, rough mill the pin hole and waist-shaped hole on the step surface, leave a single side of 2mm for finishing, and chamfer each hole mouth to the size.

[0015] Further, in step six, The workpiece is placed on the equal height block of the tooling to correct the workpiece with the processed outer circle, press the workpiece tightly to finish turning the small end outer circle; finish turning the small end part outer circle size, finish processing to the drawing size according to the drawing size requirement; finish turning the 12 wide groove to the size, 8.6 deep; finish turning each processing surface chamfer to the size; In step seven, the workpiece is placed on the equal height block of the tooling to correct the workpiece with the finished turned outer circle, press the workpiece tightly, finish milling each processing surface, finish milling the outer circle side surface groove shape and inner hole to the size, finish boring the D42H6 pin hole to the size, finish milling the pin hole and waist-shaped hole on each boss surface to the size, and mill the outer circle mark hole to the size.

[0016] Further, in step one, the bridge type special lifting appliance includes two left and right cranes, lifting belts, and a special lifting plate; the lower end of the special lifting plate is connected with the workpiece A reference end face processed hole, and the other end is connected and fixed with four of the six through holes of the workpiece intermediate web.

[0017] The application has the following advantages: 1. Safe and efficient hoisting system A bridge type special lifting device is designed, and through the cooperation of double cranes and process hole positioning, the safe turning over and transfer of oversized workpieces are realized, and the risk problem of traditional single crane lifting is solved.

[0018] Segmented lifting point design is adopted: in the rough machining stage, the casting process lifting ring is used, and in the finishing stage, the web through hole is switched to avoid interference of the lifting point in the machining process.

[0019] 2. Process centralization and reference unification Through the completion of five sequence machining in the same posture (vertical machine → boring machine → turning and milling composite → second boring machine → second vertical machine → third boring machine), the number of workpiece turning over is reduced (only once), and the damage risk of transfer is reduced.

[0020] Reference surface progressive machining: the first sequence uses the middle web boss as support (Φ<3550mm), and the subsequent processes reuse the boring machine tooling (Φ3500mm), to ensure that the position error of A / D reference is ≤2mm.

[0021] 3. High-precision complex structure machining Composite tool and tooling adaptation: SORALUCE turning and milling composite machining is adopted for deep cavity bevel (2300mm), and a special accessory milling head is matched to realize one-time forming of the inner cavity shoulder surface.

[0022] Pin hole sequence precision boring: first drill the bottom hole (leave 2mm allowance), release stress, and then use SORALUCE wire precision boring to ensure that the position of the φ50H7 / φ20G8 pin hole is accurate.

[0023] 4. Turning over tooling design scheme: special lifting devices are used for inter-process hoisting, which is stable and efficient, and special lifting lugs are designed to realize air turning over by using side flanges, to ensure that the part turning over has no bumping. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall installation structure of the application; Figure 2 It is a schematic diagram of the main shaft axial structure of the application; Figure 3 It is a schematic diagram of the position structure of each end face of the application; Figure 4 It is a schematic diagram of the intermediate web structure of the application; Figure 5 It is a schematic diagram of the process one structure of the application Figure 1 ; Figure 6 It is a schematic diagram of the process one structure of the applicationFigure 2 Figure 7 Process 1 structure diagram of the present application Figure 3 Figure 8 Process 2 structure diagram of the present application Figure 1 Figure 9 Process 2 structure diagram of the present application Figure 2 Figure 10 Process 2 structure diagram of the present application Figure 3 Figure 11 Process 3 structure diagram of the present application Figure 12 Process 4 structure diagram of the present application Figure 13 Process 5 structure diagram of the present application Figure 1 Figure 14 Process 6 structure diagram of the present application Figure 13 Figure 15 Process 6 structure diagram of the present application Figure 1 Figure 16 Process 6 structure diagram of the present application Figure 15 Figure 17 Process 6 structure diagram of the present application Figure 15

[0025] In the figure: 1, workpiece, 11, intermediate web, 2, bridge type special lifting appliance, 3, machining center, 4, machine tool workbench, 5, side tool holder. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the present application is further described in detail below by means of the accompanying drawings and examples. However, it should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the scope of the present application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0028] ​​​​​​​​​​This project is mainly aimed at the Siemens latest development of 22 megawatt large offshore direct drive wind turbine main shaft and tower processing technology research, the model abroad only production prototype, domestic still no production precedent. Especially the main shaft in the past model, structure on the basis of a lot of adjustment, the increase of the middle flange, which has a plurality of inclined plane and screw hole need to be processed, and the depth of the cavity is more than 2300mm, bring difficulties to processing; Similarly, there are many complex cavity processing on the cylinder, the use of existing accessories and tools can not complete the processing; The weight of the workpiece exceeds the allowable lifting weight of the current crane, which is also a big problem.

[0029] This process method is to solve the size accuracy, shape and position accuracy and surface quality error of each end face and flange, and to complete the finish turning and ensure that each accuracy meets the requirements of the drawing by using new CK5263 numerical control vertical lathe.

[0030] Because the weight of the workpiece is in the limit of the workbench, the key is to solve the problem of reasonable design of the tool structure, to ensure that the load distribution of the rotary table meets the requirements of the machine tool, and to prevent the machine tool from not running normally or even being damaged.

[0031] This process uses existing numerical control floor boring machine, designs special tooling, selects special accessory milling head, processes each end face, flange hole and complex cavity, and pays special attention to ensuring that the position of each pin hole meets the requirements of the drawing.

[0032] For the problem of fixed shaft lifting and turning over, the workpiece is transported between the workshops in the factory by using an 80-ton trailer, the lifting point of the workpiece is selected, and the process ring of the casting can be used before rough machining. Four of the six holes in the middle web are used during the machining process, and two cranes are used to lift the workpiece in and out of the machine tool, with a minimum distance of 6.3m between the two cranes. In order to ensure the safety of lifting, a bridge type special lifting device is designed and made, as shown in Figure 1 . In this scheme, the web surface and the bottom surface are used as the main support points, and the four clamps are placed on the ground stop, and the workpiece is corrected to the center of rotation, Step two: first sequence, vertical lathe processing, A reference surface upward, the workpiece 1 is supported by the convex platform plane of the middle web 11 on the numerical control vertical lathe, the support effective diameter is less than 3550mm, which is the maximum diameter of the support bearing of the machine tool workbench 4; The side tool holder roughens and finishes the plane and flange to the drawing size, the side tool holder 5 roughens the D reference surface and the same side flange, and the B reference is finished by one knife but the size is less than the drawing size; Step three: second sequence, boring machine processing Keep the posture A reference surface up, adopt the tooling, the tooling is in effective contact with the boring machine workbench, the maximum diameter is 3500mm, the workbench support ring maximum diameter is 3400mm, the tooling self weight is less than 10 tons, the workpiece is positioned with the D reference plane of one sequence processing, the processing reference A flange surface threaded hole through hole, the four around surface processing, the pin hole bottom hole; Step four: three sequences, SORALUCE turning and milling composite processing Keep the posture A reference surface up, use the boring machine tooling, process the A reference surface pin hole and the inner cavity bevel, the bracket; Step five: four sequences, boring machine processing two, Turn over the D reference up, use the boring machine tooling, boring and milling processing pin hole, threaded hole and through hole to the drawing size; Step six: five sequences: vertical machine processing two, Keep the posture D reference up, use the boring machine tooling, finish turning the D reference end to the drawing size.

[0033] In this embodiment, in step one, the workpiece 1 is stably hoisted to the tooling, contacts the adjustable support on the tooling and falls down, and then the common center of the upper and lower two layers of the outer circle is corrected to be within 0.02mm, the symmetry 4-point error of the outer circle is less than 0.02mm, and then the workpiece 1 is locked.

[0034] In this embodiment, in step two, this step is the rough and finish turning stage of the workpiece 1, Firstly, the "Z" direction processing allowance needs to be determined; according to the drawing size mark and position, the upper and lower end surface processing allowance is confirmed by using the height gauge measurement and the machine tool tool setting method, and the allowance of each processing surface is considered; According to the drawing, each part is processed to the size, and when the reverse turning inner hole Φ4490 is processed, attention is paid to the risk of being processed to the blank body, if the blank body is processed, the oblique line feed method is used to process to avoid damage to the tool, machine tool and workpiece, and the chamfering treatment is performed at each corner; The upper end part outer dimension is roughed and finished to the drawing size according to the drawing size requirement; The lower end part outer dimension is roughed, and a 2mm finish machining allowance is left on one side according to the drawing size requirement; The lower end reference plane is reverse turned and controlled in size.

[0035] In this embodiment, in the step three, the workpiece 1 large end outer circle area and small end groove φ75 counterbore are processed to the drawing size by using the boring machine, wherein the large end outer circle area and the intermediate step surface hole are all processed to the drawing size, except that the φ50 and φ20 pin holes are not processed temporarily, the small end part area is processed to remove the allowance, and a 2mm finish machining allowance is left on one side.

[0036] Workpiece 1 is placed on the equal height block of the tool, and the workpiece is corrected with the machined outer circle, the workpiece is corrected with the blank shape, the dimensions of the inner cavity are considered, the outer circle of the large end is milled to size, the screw holes on the large end surface are drilled and tapped to size, the screw holes on the step surface are drilled and tapped to size, the outer circle groove of the small end is rough milled to size, the single side is left with 2mm finishing allowance, the 4X2XD75±0.2 counterbore is milled to size, and the hole chamfer is chamfered to size.

[0037] In this embodiment, in step four, the workpiece is placed on the equal height block of the tool, the center of the workpiece is found with the outer circle, the workpiece is straightened with the b45 hole, the workpiece is pressed, the D50H7 and D20G8 pin holes are precisely bored to size, the inner cavity of each tab surface and all holes on the surface are precisely machined to size, and the hole chamfer is chamfered to size.

[0038] In this embodiment, in step five, after turning over, the workpiece 1 is placed on the equal height block of the tool, the workpiece is positioned and corrected with the p45 hole, the workpiece is pressed, the 2X158XM42 screw holes on the D reference surface are drilled and tapped to size, the inner cavity of each tab surface and all holes on the surface are machined to size, the inner cavity side surface boss surface and screw hole are machined to size, the pin hole and waist-shaped hole on the step surface are rough milled, the single side is left with 2mm finishing allowance, and the hole chamfer is chamfered to size.

[0039] In this embodiment, in step six, The workpiece is placed on the equal height block of the tool, the outer circle is corrected with the machined outer circle, the workpiece is pressed, the small end outer circle is precisely turned, the small end outer circle size is precisely turned, the size is precisely machined to the size required by the drawing, the 12 wide groove is precisely turned to size, the depth is 8.6, and the chamfer of each machining surface is precisely turned to size; Step seven: the workpiece is placed on the equal height block of the tool, the workpiece is corrected with the precisely turned outer circle, the workpiece is pressed, each machining surface is precisely milled, the outer circle side surface groove shape and inner hole are precisely milled to size, the D42H6 pin hole is precisely bored to size, the pin hole and waist-shaped hole on each boss surface are precisely milled to size, and the outer circle mark hole is milled to size.

[0040] In step one, the bridge type special lifting appliance 2 includes two left and right cranes, lifting lines and a special lifting plate 21; the lower end of the special lifting plate 21 is connected with the reference end face of the workpiece 1A machined hole, and the other end is connected and fixed with four holes in the six through holes of the middle web plate 11 of the workpiece 1.

[0041] The present application proposes an integrated process scheme for the processing difficulty of large offshore wind power main shaft and tower, which has the following obvious advantages: 1. Safe and efficient hoisting system A bridge type special lifting appliance is designed, the safe turning and transfer of the oversized workpiece are realized through the cooperation of double cranes (the minimum distance is 6.3m) and process hole positioning, and the risk problem of traditional single crane lifting is solved.

[0042] A segmented lifting point design is adopted: the casting process lifting ring is used in the rough machining stage, and the web through hole is switched in the finish machining stage to avoid interference of the lifting points during the machining process.

[0043] 2. Process centralization and standardization The five-stage machining process (vertical lathe → boring machine → milling and turning → secondary boring machine → secondary vertical lathe → tertiary boring machine) is completed in the same posture, reducing the number of workpiece turning times (only 1 time) and lowering the risk of damage during transport.

[0044] Progressive machining of the reference surface: The first step is supported by the intermediate web boss (Φ<3550mm), and subsequent processes reuse the boring machine fixture (Φ3500mm).

[0045] 3. High-precision machining of complex structures Composite tooling and fixture adaptation: SORALUCE milling and turning composite machining is used for deep cavity inclined surfaces (2300mm), with a special attachment milling head to achieve one-time forming of the inner cavity joint surface.

[0046] Precision boring of pin holes in sequence: First, drill the pilot hole (leaving a 2mm allowance) to release stress, and then perform precision boring in Solarus to ensure the position accuracy of the φ50H7 / φ20G8 pin hole.

[0047] 4. Quality control and cost optimization The self-made standard sample and carbon fiber comparison device greatly control the measurement cost while meeting the requirements for precise dimensional control.

[0048] 5. Turnover tooling design scheme: Use special lifting tools for inter-process lifting, which is stable and efficient. The special lifting lugs are designed to achieve air turning using side flanges, ensuring that the parts are turned over without collision.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A machining process for the main shaft of a large-megawatt direct-drive offshore wind turbine, characterized in that, The process includes the following steps: Step 1: When the workpiece (1) is loaded onto and unloaded from the machine tool, two overhead cranes are used to lift it together. The maximum distance between the two overhead cranes is less than 8 meters and the minimum distance between the end beams is greater than 2 meters. In order to ensure the safety of the lifting, a special bridge-type lifting device (2) is designed and manufactured. The workpiece (1) is placed on the worktable of the machining center (3) through this lifting device. Step Two: First-stage machining on an vertical lathe. With reference surface A facing upwards, workpiece (1) is supported on the CNC vertical lathe by the boss plane of the intermediate web plate (11). The effective support diameter is less than 3550mm. This diameter is the maximum diameter of the support bearing of the machine tool worktable (4). The vertical tool holder rough and finish turns the plane and flange to the drawing size. The side tool holder (5) rough turns the D reference surface and the flange on the same side. It finishes one cut at reference B, but the size is less than the drawing size. Step 3: Second stage, boring machine processing Keep the first process orientation A reference surface upward, use tooling, the tooling has a maximum effective contact diameter of 3500mm with the boring machine table, the maximum diameter of the table support ring is 3400mm, the tooling weight is less than 15 tons, the workpiece is positioned with the first process reference plane D, the machining reference A flange face threaded hole through hole, the four sides are machined, and the pin hole is drilled. Step 4: Three-stage, SORALUCE milling and turning machining With the second-order orientation A facing upwards, use a boring machine fixture to machine the pin hole, inner cavity bevel, and latch on the A datum surface; Step 5: Fourth stage, boring machine processing 2, Turn the machine over so that reference point D is facing upwards, and use a boring machine fixture to bore and mill the pin holes, threaded holes, and through holes to the dimensions shown in the drawing. Step Six: Fifth Sequence: Vertical Lathe Machining II With the fourth position D datum facing upwards, use a boring machine fixture to finish machine the D datum end to the dimensions shown in the drawing.

2. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step one, the workpiece (1) is smoothly hoisted onto the fixture and falls into contact with the adjustable support on the fixture. Then, the common center of the upper and lower outer circles is corrected to be within 2mm. The error of the four symmetrical points of the outer circle is rechecked to be less than 2mm. Then, the workpiece (1) is locked.

3. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step two, this step is the rough and finish turning stage of workpiece (1). First, it is necessary to determine the machining allowance in the "Z" direction; according to the dimensions and positions on the drawing, use a height gauge to measure and the machine tool to set the tool to confirm the machining allowance of the upper and lower end faces, taking into account the allowance of each machining surface; According to the drawings, machine each part to the dimensions. When turning the inner hole Φ4490, pay attention to the risk of machining the blank body. If the blank body is machined, use the oblique infeed method to avoid damage to the tool, machine tool and workpiece. Chamfer all edges and corners. The outer dimensions of the upper part of the rough and finish machine are precision machined to the dimensions specified in the drawings. For the rough machining of the lower part, leave a 2mm finishing allowance on each side according to the dimensions required in the drawing. The lower reference plane of the reverse end is used to control dimensions.

4. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step three, the outer circle area of ​​the large end of the workpiece (1) and the φ75 countersunk hole at the groove of the small end are machined to the size of the drawing using a boring machine. Among them, the outer circle area of ​​the large end and the hole of the middle step are all machined to the size of the drawing. Except for the φ50 and φ20 pin holes, which are not machined for the time being, the small end part is machined to remove the excess, and a 2mm finishing allowance is left on each side.

5. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 4, characterized in that, The workpiece (1) is placed on the tooling block of equal height. The workpiece is corrected by the machined outer circle and the workpiece is corrected by the blank shape. The dimensions of each inner cavity are taken into account. The outer circle of the large end is milled to the dimension. The screw holes on the large end face are drilled and tapped to the dimension. The screw holes on each step face are drilled and tapped to the dimension. The groove of the small end outer circle is rough milled to the dimension. A 2mm finishing allowance is left on each side. The 4X2XD75±0.2 countersunk hole is milled to the dimension. The opening of each hole is chamfered to the dimension.

6. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step four, the workpiece is placed on the tooling level block, the center of the workpiece is found by the outer circle, the workpiece is straightened by the D45 hole, the workpiece is clamped, the D50H7 and D20G8 pin holes are precision bored to the size, the inner cavity of each pad surface and all holes on the surface are precision machined to the size, and the openings of each hole are chamfered to the size.

7. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step five, after flipping over, the workpiece (1) is placed on the tooling level block, the workpiece is positioned and corrected by the D45 hole, the workpiece is pressed, the screw holes on the D reference surface are drilled and tapped to the drawing size, the inner cavity bosses are machined to the dimensions of each contact surface and all holes on the surface, the inner cavity side bosses and screw holes are machined to the dimensions, the pin holes and waist-shaped holes on the step surface are rough milled, a 2mm finishing allowance is left on each side, and the openings of each hole are chamfered to the dimensions.

8. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step six, The workpiece is placed on the tooling level block, and the outer circle of the machined workpiece is checked for roundness. The small end outer circle of the workpiece is then pressed and precision machined. The outer circle of the small end is precision machined to the dimensions required by the drawing. The 12-width groove is precision machined to the dimensions and the depth is 8.

6. All machined surfaces are then chamfered to the dimensions. The workpiece is placed on the tooling level block, the workpiece is corrected by the precision-machined outer circle, the workpiece is clamped, each machined surface is precision milled, the outer circle side groove shape and inner hole are precision milled to size, the D42H6 pin hole is precision bored to size, the pin hole and waist hole on each boss surface are precision milled to size, and the outer circle marking hole is milled to size.

9. The machining process for a large-megawatt direct-drive offshore wind turbine main shaft according to claim 1, characterized in that, In step one, the bridge-type special lifting tool (2) includes two cranes on the left and right, a lifting line and a special lifting plate (21); the lower end of the special lifting plate (21) is connected to the machined hole on the reference end face of workpiece (1) A, and the other end is connected and fixed to 4 of the 6 through holes in the middle web plate (11) of workpiece (1).

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