Precise clamping and positioning fixture and milling method for large thin-walled hollow blade casting parts

Abstract

The invention relates to a precise clamping and positioning fixture and milling method for large thin-walled hollow blade casting parts, which belongs to the technical field of auxiliary tooling for machining large thin-walled hollow blade casting parts, and includes a base for supporting the upper structure, on which a floating pressure plate assembly, a first auxiliary support assembly, a second auxiliary support assembly, a bottom reference and a bottom auxiliary support are respectively installed by bolts, the floating pressure plate assembly and the first auxiliary support assembly are located at one end of the upper surface of the base and are arranged opposite to each other, a bottom reference and a bottom auxiliary support are installed on the base between the two, and a second auxiliary support assembly arranged opposite to the bottom reference is installed on the other end of the upper surface of the base. The invention solves the problems of difficult clamping and positioning of parts, easy deformation and vibration. The milling quality accuracy of this type of parts is guaranteed, and the consistency and machining efficiency of the products are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of auxiliary tooling for machining large thin-walled hollow blade-shaped casting parts, and in particular relates to a precise clamping and positioning fixture and a milling method for large thin-walled hollow blade-shaped casting parts. Background Art

[0002] In the milling process of large thin-walled hollow blade casting parts, it is often difficult to position the parts, the deformation is large, the vibration during the processing is severe, and the milling size of the parts is easy to exceed the tolerance, the parts are easy to deform, and the product consistency is poor due to the complex blade surface, thin wall thickness, poor rigidity, relatively large casting size tolerance of the parts, and poor consistency. Summary of the invention

[0003] The purpose of the present invention is to provide a large-scale thin-walled hollow blade casting part accurate clamping and positioning fixture and milling method, which solves the problem of difficult clamping and positioning of parts, easy deformation and vibration, ensures the milling quality accuracy of this type of parts, and improves the consistency and processing efficiency of the products.

[0004] A precise clamping and positioning fixture for large thin-walled hollow blade-shaped casting parts includes a base for supporting an upper structure, on which a floating pressure plate assembly, a first auxiliary support assembly, a second auxiliary support assembly, a bottom reference and a bottom auxiliary support are respectively installed by bolts, the floating pressure plate assembly and the first auxiliary support assembly are located at one end of the upper surface of the base and are arranged opposite each other, the bottom reference and the bottom auxiliary support are installed on the base between the two, and a second auxiliary support assembly arranged opposite the bottom reference is installed at the other end of the upper surface of the base.

[0005] The floating pressure plate assembly includes a seat I, the bottom end of which is fixedly mounted on the base by bolts, a slide groove is provided at the top of the seat I, a long slider is installed in the slide groove, the front end of the long slider is connected to a connecting rod, floating pressure plates are respectively installed at both ends of the connecting rod, and the floating pressure plate is fixed to the connecting rod by nuts, the rear end of the long slider is rotatably connected to the screw end of the lateral clamping screw, a top plate and a rear plate closed slide groove are respectively installed on the top and rear side wall of the seat I, a lateral clamping screw is threadedly connected to the rear plate, and the long slider is pushed to slide in the slide groove by rotating the lateral clamping screw, thereby pushing the floating pressure plate to clamp the blade profile.

[0006] A U-shaped seat is processed at the front end of the long slider, and through holes are opened on the two arms of the U-shaped seat. A through hole corresponding to the through hole of the U-shaped seat is opened in the middle of the connecting rod. The connecting rod is located in the U-shaped seat. The connecting rod is fixed to the U-shaped seat by passing a bolt through the through hole of the U-shaped seat and the through hole of the connecting rod and then screwing a nut on the end of the bolt.

[0007] There are two bottom datums, and the two bottom datums are arranged face to face. The cross-sectional shape of the bottom datum is L-shaped. The bottom datum is fixed on the base through a horizontal part and bolts, and the top of the vertical part of the bottom datum is processed into an arc surface to form a positioning reference point.

[0008] The bottom auxiliary support is a support screw, the screw rod part of which is screwed on the base, and the nut part forms an auxiliary support.

[0009] The first auxiliary support includes a seat II, the bottom end of which is fixed on the base by bolts, a countersunk hole is opened on the top of the seat II, the small hole of the countersunk hole is processed into a threaded hole, the cylindrical end of the top pressure plate is installed in the large hole of the countersunk hole, the top clamping screw passes through the through hole of the cylindrical end of the top pressure plate and is threadedly connected with the small hole of the countersunk hole, and a spring I is installed in the through hole at the bottom of the cylindrical end of the top pressure plate and is sleeved on the outside of the top clamping screw, a side plate I is installed on the side wall of one end of the seat II, and a side reference I is installed in the middle of the outer surface of the side plate I, the top and bottom of the side wall of the side plate I are respectively installed with auxiliary support I and auxiliary support II, a side plate II is installed on the side wall of the other end of the seat II, the top and bottom of the side plate II are respectively installed with side reference II and side reference III, and a lateral reference is installed on the side wall of the seat II at the top of the side plate II.

[0010] The planes on which the side reference I, side reference II and side reference III face the floating pressure plate are side reference points.

[0011] The second auxiliary support includes a U-shaped base and a vertical plate. The U-shaped base is fixedly installed on the base by bolts, and the vertical plate is fixedly installed on the side wall of the base by bolts. Auxiliary supports III and IV are respectively installed on the top of the U-shaped base, and auxiliary supports V and VI corresponding to auxiliary supports III and IV are respectively installed on the top of the vertical plate.

[0012] A method for using a large thin-walled hollow blade casting part to accurately clamp and position the part for milling processing comprises the following steps:

[0013] Step 1, place the blade surface of the part on the positioning fixture; then adjust the blade position of the part so that the blade surface fits with the six reference points formed by the side reference I, side reference II and side reference III, the side reference and the two bottom references to ensure that there is no gap;

[0014] Step 2, install the adjustable support into the hollow blade of the part, adjust the installation position of the adjustable support, and then use a hexagonal wrench to adjust the tightening screw, adjust the extension length of the sliding support end of the adjustable support, and use the fixed end profiling support surface and the sliding end profiling support surface of the adjustable support to support the inner wall surfaces on both sides of the blade of the part, so that the external support point of the part and the pressing point are collinear along the direction of the adjustable support and ensure that the part has no obvious deformation;

[0015] Step 3, adjust the auxiliary support II and the auxiliary support I so that the auxiliary support I and the auxiliary support II are just close to the blade surface, tighten the lateral clamping screw, so that the floating pressure plate moves axially to clamp the blade side, and ensure that the six reference points of the positioning fixture are in contact with the part without gap during the clamping process;

[0016] Step 4, tighten the top surface clamping screw so that the top surface clamping plate presses the upper part of the part blade, and during the clamping process, ensure that the six reference points of the positioning fixture are in contact with the part without gap;

[0017] Step 5, adjust the auxiliary support III of the remaining parts to cooperate with the auxiliary support V, the auxiliary support IV to cooperate with the auxiliary support VI and the bottom auxiliary support to press the parts tightly. The dial indicator can be used to control the clamping process to ensure that there is no obvious deformation of the parts during the clamping process;

[0018] Step 6: Measure the part status and analyze the data through the typical coordinate point table method. After confirming that there is no problem with the data, the coordinate system can be established according to the data for milling operation;

[0019] Step 7: After the coordinate system is determined, the blade end face, side wall contour and island inner shape of the part are milled.

[0020] The adjustable support device includes a long connecting rod, and a positioning ball I and a positioning ball II are respectively installed at both ends of the long connecting rod. The positioning ball I is also hinged to one end of the position adjustment screw I, and the positioning ball II is also hinged to one end of the position adjustment screw II. The other end of the position adjustment screw I is hingedly installed on the side wall surface of the fixed support end of the spiral support device, and the other end of the position adjustment screw II is connected to the other side wall surface of the fixed support end of the spiral support device by brazing.

[0021] The spiral support device includes a fixed support end, an end face of one end of the fixed support end is a fixed end profiling support surface, and the other end is provided with a groove, a sliding support end is installed in the groove, the end face of the sliding support end is a sliding end profiling support surface, a wedge-shaped slider is slidably installed in the sliding support end, and a spring II is installed between the sliding support end and the wedge-shaped slider, the wedge-shaped slider is connected to a driving device screwed on the fixed support end, in a working state, the wedge-shaped slider of the rotating driving device moves inward along the groove of the sliding support end, pushing the sliding end profiling support surface to move outward; in a non-working state, the reverse rotating driving device moves the wedge-shaped slider outward along the groove of the sliding support end, and at the same time, the sliding support end is retracted into the groove under the action of the spring elastic force.

[0022] The beneficial technical effects of the present invention are:

[0023] The positioning tool has the advantages of simple structure, convenient operation, accurate positioning, reduced vibration, and obvious deformation control effect. It can be widely used in the precise clamping, positioning and milling process of hollow, thin-walled, and special-shaped blade parts in aerospace engines and gas turbines. It can effectively improve the clamping and positioning accuracy of parts, reduce part deformation, and improve product qualification rate and production efficiency.

[0024] At present, this processing method has been successfully applied to the milling process of thin-walled hollow blade casting parts in a large turbofan engine project of our company, which greatly reduces the deformation of parts during the clamping process and ensures the positioning accuracy of parts during the mirror processing process. It is estimated that after the promotion of this processing method in the company, it can save the company about 600,000 yuan in part quality loss, labor hours and other costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the relative position relationship of the large thin-walled hollow blade casting parts after the parts are clamped by the accurate clamping and positioning fixture of the present invention;

[0026] Figure 2 Schematic diagram of the precise clamping and positioning fixture for large thin-walled hollow blade casting parts of the present invention;

[0027] Figure 3 A cross-sectional view of the precise clamping and positioning fixture for large thin-walled hollow blade casting parts of the present invention;

[0028] Figure 4 Working principle diagram of the floating pressure plate of the accurate clamping and positioning fixture for large thin-walled hollow blade casting parts of the present invention;

[0029] Figure 5 Schematic diagram of the installation position of the adjustable support of the present invention;

[0030] Figure 6 Schematic diagram of the cross-sectional position of the adjustable support of the present invention in the part cavity;

[0031] Figure 7 A schematic diagram of the structure of the adjustable support device of the present invention;

[0032] Figure 8 A schematic diagram of the internal structure of the spiral support device of the adjustable supporter of the present invention;

[0033] Fig. 9 The present invention selects typical dimensions on the blade profile to check the coordinate position of the parts structure diagram;

[0034] 1-base, 2-bottom reference, 3-bottom auxiliary support, 4-upright seat Ⅰ, 5-slide, 6-long slider, 7-connecting rod, 8-floating pressure plate, 9-lateral clamping screw, 10-top plate, 11-back plate, 12-upright seat Ⅱ, 13-top pressure plate, 14-spring Ⅰ, 15-auxiliary support Ⅰ, 16-auxiliary support Ⅱ, 17-side reference Ⅱ, 18-side reference Ⅲ, 19-side reference Ⅰ, 20-lateral reference, 21-U-shaped base, 22-upright plate, 23 -Auxiliary support III, 24-Auxiliary support IV, 25-Auxiliary support V, 26-Auxiliary support VI, 27-Long connecting rod, 28-Positioning ball I, 29-Positioning ball II, 30-Position adjusting screw I, 31-Position adjusting screw II, 32-Fixed support end, 33-Fixed end contoured support surface, 34-Sliding support end, 35-Wedge-shaped slider, 36-Spring II, 37-Top surface clamping screw, 38-Adjustable support, 39-Sliding end contoured support surface, 40-Tension screw. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0036] like Figures 2 to 4 As shown, a precise clamping and positioning fixture for large thin-walled hollow blade casting parts includes a base 1 for supporting an upper structure, on which a floating pressure plate assembly, a first auxiliary support assembly, a second auxiliary support assembly, a bottom datum 2 and a bottom auxiliary support 3 are respectively installed by bolts, the floating pressure plate assembly and the first auxiliary support assembly are located at one end of the upper surface of the base 1 and are arranged opposite to each other, the bottom datum and the bottom auxiliary support 3 are installed on the base 1 between the two, and a second auxiliary support assembly arranged opposite to the bottom datum 2 is installed on the other end of the upper surface of the base 1.

[0037] The floating pressure plate assembly includes a stand I4, the bottom end of which is fixedly mounted on the base 1 by bolts, a slide groove 5 is provided on the top of the stand I4, a long slider 6 is installed in the slide groove 5, the front end of the long slider 6 is connected to the connecting rod 7, floating pressure plates 8 are respectively installed at both ends of the connecting rod 7, the floating pressure plate 8 can rotate freely on the connecting rod 7, and the floating pressure plate 8 is installed on the connecting rod 7 by a nut, the rear end of the long slider 6 is rotatably connected to the screw end of the lateral clamping screw 9, a top plate 10 and a rear plate 11 are respectively installed on the top and rear side wall of the stand I4 to close the slide groove 5, the rear plate 11 is threadedly connected with the lateral clamping screw 9, and the long slider 6 is pushed to slide in the slide groove 5 by rotating the lateral clamping screw 9, thereby pushing the floating pressure plate 8 to clamp the blade profile.

[0038] A U-shaped seat is processed at the front end of the long slider 6, and through holes are opened on the two arms of the U-shaped seat. A through hole corresponding to the through hole of the U-shaped seat is opened in the middle of the connecting rod 7. The connecting rod 7 is located in the U-shaped seat. The connecting rod 7 is fixed to the U-shaped seat by passing a bolt through the through hole of the U-shaped seat and the through hole of the connecting rod 7 and then screwing a nut on the end of the bolt. A through hole that cooperates with the front end ball of the lateral clamping screw 9 is opened at the rear end of the long slider 6, so that the ball part of the lateral clamping screw 9 can rotate in the through hole.

[0039] There are two bottom datums 2, and the two bottom datums 2 are arranged face to face. The cross-sectional shape of the bottom datum 2 is L-shaped. The bottom datum 2 is fixed on the base 1 through a horizontal part and bolts. The top of the vertical part of the bottom datum 2 is processed into an arc surface to form a positioning reference point.

[0040] The bottom auxiliary support 3 is a support screw, the screw rod portion of which is screwed onto the base 1 , and the nut portion forms an auxiliary support.

[0041] The first auxiliary support includes a stand II 12, the bottom end of which is fixedly mounted on the base 1 by bolts, a countersunk hole is provided on the top of the stand II 12, the small hole of the countersunk hole is processed into a threaded hole, the cylindrical end of the top pressure plate 13 is installed in the large hole of the countersunk hole, the top clamping screw 37 passes through the through hole of the cylindrical end of the top pressure plate 13 and is threadedly connected with the small hole of the countersunk hole, and a spring I 14 is installed in the through hole at the bottom of the cylindrical end of the top pressure plate 13 and is sleeved on the outside of the top clamping screw 37. By tightening the top clamping screw 37, the parts can be pre-tightened in the vertical direction, and by loosening the top clamping screw The top pressure plate 13 with screw 37 rises under the elastic force of spring Ⅰ14 to facilitate the disassembly of parts. A nylon pad is installed on the lower surface of the front end of the top pressure plate 13, a side plate Ⅰ is installed on the side wall of one end of the stand Ⅱ12, and a side reference Ⅰ19 is installed in the middle of the outer surface of the side plate Ⅰ, and auxiliary supports Ⅰ15 and auxiliary supports Ⅱ16 are installed on the top and bottom of the side wall of side plate Ⅰ respectively. A side plate Ⅱ is installed on the side wall of the other end of the stand Ⅱ12, and side references Ⅱ17 and Ⅲ18 are installed on the top and bottom of side plate Ⅱ respectively. A lateral reference 20 is installed on the side wall of the stand Ⅱ12 at the top of side plate Ⅱ.

[0042] The planes on which the side reference I 19 , the side reference II 17 and the side reference III 18 face the floating plate 8 are the side reference points.

[0043] The second auxiliary support includes a U-shaped base 21 and a vertical plate 22. The U-shaped base 21 is fixedly installed on the base 1 by bolts, and the vertical plate 22 is fixedly installed on the side wall of the base 1 by bolts. Auxiliary supports III 23 and IV 24 are respectively installed on the top of the U-shaped base 21, and auxiliary supports V 25 and VI 26 corresponding to auxiliary supports III 23 and IV 24 are respectively installed on the top of the vertical plate 22.

[0044] A method for using a large thin-walled hollow blade casting part to accurately clamp and position the part for milling processing comprises the following steps:

[0045] Step 1: Follow the instructions in the attached Figure 1 Place the blade surface of the part on the positioning fixture according to the position and direction of the blade surface; then adjust the blade position of the part so that the blade surface is aligned with the attached Figure 2 The six reference points formed by the side reference Ⅰ19, the side reference Ⅱ17, the side reference Ⅲ18, the side reference 20 and the two bottom references 2 are fitted together to ensure no gap;

[0046] Step 2: Follow the instructions in the attached Figure 5 and attached Figure 6 As shown, the adjustable support 38 is installed in the hollow blade of the part. The structural diagram of the adjustable support 38 is shown in the attached Figure 7 and attached Figure 8 ; Adjust the installation position of the adjustable support 38, then use a hexagonal wrench to adjust the tightening screw, adjust the extension length of the sliding support end 34 of the adjustable support 38, and use the fixed end profiling support surface 33 and the sliding end profiling support surface 39 of the adjustable support to support the inner wall surfaces on both sides of the part blade profile, so that the external support point and the pressing point of the part are collinear along the direction of the adjustable support 38 and ensure that the part has no obvious deformation;

[0047] The specific structure of the adjustable support 38 is as follows: the adjustable support 38 includes a long connecting rod 27, and the two ends of the long connecting rod 27 are respectively installed with a positioning ball I 28 and a positioning ball II 29, the positioning ball I 28 is also hinged to one end of the position adjustment screw I 30, and the positioning ball II 29 is also hinged to one end of the position adjustment screw II 31, and the other end of the position adjustment screw I 30 is hingedly installed on the side wall surface of the fixed support end 32 of the spiral support device, and the other end of the position adjustment screw II 31 is brazed with the fixed support end 32 of the spiral support device. The other side wall surface of the support end 32 is connected as a whole, and the side wall surface of the fixed support end 32 hinged by the position adjustment screw rod Ⅰ30 is vertically arranged with the side wall surface of the fixed support end brazed by the position adjustment screw rod Ⅱ31; in this embodiment, the adjustment screw rod Ⅰ30 and the adjustment screw rod Ⅱ31 have the same structure, both of which are composed of two screw rods and a screw sleeve, and the two screw rods are screwed together by the screw sleeve, and the threads at both ends of the screw sleeve have opposite rotation directions, and the two screw rods are brought closer or separated by rotating the screw sleeve, thereby adjusting the length of the adjustment screw rod Ⅰ30 and the adjustment screw rod Ⅱ31;

[0048] The spiral support device includes a fixed support end 32, the end surface of one end of the fixed support end 32 is a fixed end profiling support surface 33, and the other end is provided with a groove, a sliding support end 34 is installed in the groove, the end surface of the sliding support end 34 is a sliding end profiling support surface 39, a wedge-shaped slider 35 is slidably installed in the sliding support end 34, and a spring II 36 is installed between the sliding support end 34 and the wedge-shaped slider 35, the wedge-shaped slider 35 is connected to a driving device screwed on the fixed support end 32, in this embodiment, the driving device is a tensioning screw 40, in the working state, the wedge-shaped slider 35 of the rotating driving device moves inward along the groove of the sliding support end 34, pushing the sliding end profiling support surface to move outward; in the non-working state, the reverse rotating driving device moves the wedge-shaped slider 35 outward along the groove of the sliding support end 34, and at the same time, the sliding support end 34 is retracted into the groove under the action of the elastic force of the spring II 36;

[0049] Step 3, adjust the auxiliary support II 16 and the auxiliary support I 15 so that the auxiliary support I 15 and the auxiliary support II 16 are just close to the blade surface, tighten the lateral clamping screw 9, so that the floating pressure plate 8 moves axially to clamp the blade side surface, and ensure that the six reference points of the positioning fixture are in contact with the part without gap during the clamping process;

[0050] Step 4, tighten the top surface clamping screw 37 so that the top surface clamping plate 13 presses the upper part of the blade profile of the part. During the clamping process, ensure that the six reference points of the positioning fixture are in contact with the part without gap;

[0051] Step 5, adjust the auxiliary support III 23 of the remaining parts to cooperate with the auxiliary support V 25, the auxiliary support IV 24 to cooperate with the auxiliary support VI 26 and the bottom auxiliary support 3 to press the parts tightly. The dial indicator can be used to control the clamping process to ensure that there is no obvious deformation of the parts during the clamping process;

[0052] Step 6: Follow the instructions in the attached Fig. 9 As shown in the simplified diagram of the part structure, first select a theoretical straight line on the upper part of the blade to preliminarily determine the angular zero point, and then select typical dimensions along the X-axis, Y-axis and Z-axis directions on the part to verify the coordinate position:

[0053] Step 6.1, use a dial indicator to check the thickness dimension T0 in the X-axis direction. If the actual measured dimension T1 is different from the theoretical value T0, adjust the X-direction machining coordinate system so that the allowance distribution along the X+ and X-coordinate directions is relatively uniform;

[0054] Step 6.2, use a dial indicator to check the thickness dimension S0 in the Y-axis direction. If the actual measured dimension S1 is different from the theoretical value S0, adjust the Y-direction machining coordinate system so that the allowance distribution along the Y+ and Y- coordinate directions is relatively uniform;

[0055] Step 6.3, use a dial indicator to check the thickness dimension H0 in the Z-axis direction. If the actual measured dimension H1 is different from the theoretical value H0, adjust the Z-axis machining coordinate system. The offset of the Z-axis original coordinate origin Z0 along the Z+ direction is: ΔZ = (H1-H0) / 2. After the coordinate offset, the machining coordinate system can make the margin distribution along the Z circumferential direction relatively uniform;

[0056] Step 7: After determining the coordinate system, the part is milled. There are three types of processing parts for this part, and the milling strategies for the three parts are:

[0057] Step 7.1: Processing the blade end surface: Use The milling cutter processes the blade end face, and the cutting thickness of each layer is no more than 1mm, which can effectively reduce the cutting force and vibration;

[0058] Step 7.2: Machining the sidewall profile: Use The milling cutter processes the side wall profile, and the cutting thickness of each layer is no more than 0.5mm, which can effectively reduce cutting force and vibration;

[0059] Step 7.3: Processing the inner shape of the island

[0060] Step 7.3.1: Drill with a feed rate less than 100 mm / min and control the cutting force in the Y-axis direction;

[0061] Step 7.3.2: The milling cutter is spirally enlarged, the feed is less than 200 mm / min, and the cutting force in the Y-axis direction is controlled;

[0062] Step 7.3.3, the milling cutter mills the inner contour, reduces the tool overhang length, controls the amount of cutter clearance, and ensures the finished size of the part.

[0063] Through the above operations, the large-scale thin-walled hollow blade-shaped parts cast can be accurately clamped, aligned and positioned, and the milling of the parts can be completed with high quality. This operation method can greatly reduce the deformation of the thin-walled parts during the positioning and clamping process, effectively reduce the vibration during the milling process, improve the alignment and processing accuracy of the parts, and greatly improve the product processing quality and qualified rate.

Claims

1. A method for accurately clamping and positioning a large thin-walled hollow blade casting part by a fixture for clamping the part for milling processing, wherein the fixture comprises a base for supporting an upper structure, a floating plate assembly, a first auxiliary support assembly, a second auxiliary support assembly, a bottom reference and a bottom auxiliary support are respectively installed on the base by bolts, the floating plate assembly and the first auxiliary support assembly are located at one end of the upper surface of the base and are arranged opposite to each other, a bottom reference and a bottom auxiliary support are installed on the base between the two, and a second auxiliary support assembly arranged opposite to the bottom reference is installed on the other end of the upper surface of the base; It is characterized in that The following steps are involved: Step 1, place the blade surface of the part on the positioning fixture; then adjust the blade position of the part so that the blade surface fits with the six reference points formed by the side reference I, side reference II and side reference III, the side reference and the two bottom references to ensure that there is no gap; Step 2, install the adjustable support into the hollow blade of the part, adjust the installation position of the adjustable support, and then use a hexagonal wrench to adjust the tightening screw, adjust the extension length of the sliding support end of the adjustable support, and use the fixed end profiling support surface and the sliding end profiling support surface of the adjustable support to support the inner wall surfaces on both sides of the blade of the part, so that the external support point of the part and the pressing point are collinear along the direction of the adjustable support and ensure that the part has no obvious deformation; The adjustable support device comprises a long connecting rod, and a positioning ball I and a positioning ball II are respectively installed at both ends of the long connecting rod, the positioning ball I is also hinged to one end of the position adjustment screw rod I, the positioning ball II is also hinged to one end of the position adjustment screw rod II, the other end of the position adjustment screw rod I is hingedly installed on the side wall surface of the fixed support end of the spiral support device, and the other end of the position adjustment screw rod II is connected to the other side wall surface of the fixed support end of the spiral support device by brazing. Step 3, adjust the auxiliary support II and the auxiliary support I so that the auxiliary support I and the auxiliary support II are just close to the blade surface, tighten the lateral clamping screw, so that the floating pressure plate moves axially to clamp the blade side, and ensure that the six reference points of the positioning fixture are in contact with the part without gap during the clamping process; Step 4, tighten the top surface clamping screw so that the top surface clamping plate presses the upper part of the part blade, and during the clamping process, ensure that the six reference points of the positioning fixture are in contact with the part without gap; Step 5, adjust the auxiliary support III of the remaining parts to cooperate with the auxiliary support V, the auxiliary support IV to cooperate with the auxiliary support VI and the bottom auxiliary support to press the parts tightly. The dial indicator can be used to control the clamping process to ensure that there is no obvious deformation of the parts during the clamping process; Step 6: Measure the part status and analyze the data through the typical coordinate point table method. After confirming that there is no problem with the data, the coordinate system can be established according to the data for milling operation; Step 7: After determining the coordinate system, perform milling on the blade end face, side wall contour and island inner shape of the part.

2. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 1, characterized in that: The floating pressure plate assembly includes a seat I, the bottom end of which is fixedly mounted on the base by bolts, a slide groove is provided at the top of the seat I, a long slider is installed in the slide groove, the front end of the long slider is connected to a connecting rod, floating pressure plates are respectively installed at both ends of the connecting rod, and the floating pressure plate is fixed to the connecting rod by nuts, the rear end of the long slider is rotatably connected to the screw end of the lateral clamping screw, a top plate and a rear plate closed slide groove are respectively installed on the top and rear side wall of the seat I, a lateral clamping screw is threadedly connected to the rear plate, and the long slider is pushed to slide in the slide groove by rotating the lateral clamping screw, thereby pushing the floating pressure plate to clamp the blade profile.

3. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 2, characterized in that: A U-shaped seat is processed at the front end of the long slider, and through holes are opened on the two arms of the U-shaped seat. A through hole corresponding to the through hole of the U-shaped seat is opened in the middle of the connecting rod. The connecting rod is located in the U-shaped seat. The connecting rod is fixed to the U-shaped seat by passing a bolt through the through hole of the U-shaped seat and the through hole of the connecting rod and then screwing a nut on the end of the bolt.

4. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 1, characterized in that: There are two bottom datums, and the two bottom datums are arranged face to face. The cross-sectional shape of the bottom datum is L-shaped. The bottom datum is fixed on the base through a horizontal part and bolts, and the top of the vertical part of the bottom datum is processed into an arc surface to form a positioning reference point.

5. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 1, characterized in that: The first auxiliary support assembly includes a stand II, the bottom end of which is fixed on the base by bolts, a countersunk hole is opened on the top of the stand II, the small hole of the countersunk hole is processed into a threaded hole, the cylindrical end of the top pressure plate is installed in the large hole of the countersunk hole, the top clamping screw passes through the through hole of the cylindrical end of the top pressure plate and is threadedly connected with the small hole of the countersunk hole, and a spring I is installed in the through hole at the bottom of the cylindrical end of the top pressure plate and is sleeved on the outside of the top clamping screw, a side plate I and a side plate II are installed on the side wall of one end of the stand II, and a side reference I is installed between the side plate I and the side plate II, the top of the side wall of the side plate I and the bottom of the side wall of the side plate II are respectively installed with auxiliary supports I and auxiliary supports II, a side plate III is installed on the side wall of the other end of the stand II, the top and bottom of the side plate III are respectively installed with side reference II and side reference III, and a lateral reference is installed on the side wall of the stand II at the top of the side plate III.

6. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 5, characterized in that: The planes on which the side reference I, side reference II and side reference III face the floating pressure plate are side reference points.

7. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 1, characterized in that: The second auxiliary support assembly includes a U-shaped base and a vertical plate. The U-shaped base is fixedly installed on the base by bolts, and the vertical plate is fixedly installed on the side wall of the base by bolts. Auxiliary supports III and IV are respectively installed on the top of the U-shaped base, and auxiliary supports V and VI corresponding to auxiliary supports III and IV are respectively installed on the top of the vertical plate.

8. The method for accurately clamping and positioning large thin-walled hollow blade casting parts by a fixture for milling according to claim 1, characterized in that: The spiral support device includes a fixed support end, an end face of one end of the fixed support end is a fixed end profiling support surface, and the other end is provided with a groove, a sliding support end is installed in the groove, the end face of the sliding support end is a sliding end profiling support surface, a wedge-shaped slider is slidably installed in the sliding support end, and a spring II is installed between the sliding support end and the wedge-shaped slider, the wedge-shaped slider is connected to a driving device screwed on the fixed support end, in a working state, the wedge-shaped slider of the rotating driving device moves inward along the groove of the sliding support end, pushing the sliding end profiling support surface to move outward; in a non-working state, the reverse rotating driving device moves the wedge-shaped slider outward along the groove of the sliding support end, and at the same time, the sliding support end is retracted into the groove under the action of the spring elastic force.

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