A processing method of a fan blade metal edge wrapping

Abstract

The application provides a processing method for fan blade metal edging, which can be used for processing of fan blade metal edging as a thin-walled part, has good processing quality and high yield. The method comprises the following steps: step one, rough milling blank; step two, five-axis rough machining; step three, stress relief by heat treatment, and correction of the reference surface and the reference hole after heat treatment; step four, five-axis secondary rough machining; step five, stress relief by heat treatment again, and correction of the reference surface and the reference hole after heat treatment; step six, five-axis finish machining; step seven, cutting off the upper edging and the lower seat body from the connecting section; and step eight, trimming the edging and detecting surface defects.

Description

Technical Field

[0001] This invention relates to the field of blade processing technology, specifically a method for processing metal edging on fan blades. Background Technology

[0002] In recent years, aerospace technology has developed rapidly, and more and more engine technologies have adopted composite material technology. Engine fan blade disk technology also utilizes composite materials, which are lightweight, highly elastic, long-lasting, and stable. However, the inlet leading edge of composite materials cannot meet design requirements. Therefore, composite blades must be combined with titanium alloy metal edging. Due to the large size of the fan blades and the small leading edge width, the metal edging structure of the fan blades is complex. Specifically, the specific structure of the metal edging is as follows... Figure 1 As shown in the figure, the top of the metal edging 100 is recessed to form a groove, and the bottom is a curved surface. The metal edging is a thin-walled part, with the thinnest part of its sidewall being only 0.39mm and the bottom thickness being about 1.2mm. However, the length of the edging can reach 1103mm, which shows that its structure is complex and extremely easy to deform, and therefore it is difficult to process. Summary of the Invention

[0003] To address the problems of complex metal edging structure, easy deformation, and high processing difficulty of fan blades, this invention provides a processing method for metal edging of fan blades. This method can be used for processing metal edging of fan blades as thin-walled parts, with good processing quality and high yield.

[0004] The technical solution is as follows: A method for processing metal edging of fan blades, characterized by the following steps: Step 1, rough milling of blank; the blank includes an upper edging blank for processing into an edging and a lower seat blank for processing into a seat body, forming pressure plate grooves on the front and rear sides of the seat blank by processing the seat blank, finely finishing the bottom surface of the blank to form a reference plane and forming a reference hole on the bottom surface;

[0005] Step 2, five-axis rough machining; using the machined reference plane and reference hole as references, after fixing the blank on the rough machining fixture through the pressure plate groove, rough machining is performed on the upper edge blank. During machining, the five-axis machine tool is used to machine the top, front, back, left and right sides of the edge blank in one clamping. After machining, a single-sided allowance A is left. At the same time, the connection between the edge blank and the seat blank is machined to form an inwardly recessed connecting section.

[0006] Step 3: Heat treatment to relieve stress. After heat treatment, the datum surface and datum hole are corrected.

[0007] Step 4, five-axis secondary rough machining; using the corrected reference plane and reference hole as references, after fixing the workpiece on the rough machining fixture, perform secondary rough machining on the upper edge blank of the blank, and leave a single-sided allowance B after machining, B is less than A;

[0008] Step 5: Perform a second heat treatment to relieve stress, and then correct the reference surface and reference hole after the heat treatment;

[0009] Step Six: Five-axis finishing; Using the corrected reference plane and reference hole as references, after fixing the workpiece on the roughing fixture, semi-finish mill the inner groove surface formed by the concave top of the edge blank, leaving a allowance C after semi-finish milling, where C is less than B. After semi-finish milling, finish mill to eliminate the allowance. The remaining allowance B needs to ensure that the workpiece has sufficient rigidity to meet the processing requirements when semi-finish milling and finish milling the inner surface; After machining the inner surface, machine the outer surface of the edge blank. When machining the outer surface, divide the outer surface into multiple segments from top to bottom, and finish mill each segment to eliminate the allowance B left on the outer surface;

[0010] Step 7: Cut the upper edging and the lower base at the connecting section;

[0011] Step 8: Trim the edges and inspect for surface defects.

[0012] Its further features are:

[0013] The blank is made of TC4 titanium alloy. The heat treatment method in steps three and five is as follows: heat the workpiece to 550±10℃, hold it for 240min-255min, and then air cool it to room temperature.

[0014] Step seven uses a milling fixture to cut the edging and the base. The milling fixture includes a fixture base plate for placing the workpiece to be milled. A pressure plate for fixing the base to the fixture base plate is installed on the fixture base plate. A special-shaped frame located directly above the edging is also installed on the fixture base plate via a column. Special-shaped ejector pins extending toward the top groove of the edging are evenly threaded onto the special-shaped frame. The milling fixture also includes multiple sets of side ejector pins evenly distributed along the length of the edging. The side ejector pins are installed on side mounting seats, and each set of side ejector pins is symmetrically distributed on the front and back sides of the bottom of the edging.

[0015] The steps for cutting the edge and the base using the milling fixture are as follows: S1, Install the fixture base plate on the machine tool, insert the pressure plate into the pressure plate groove, and then fix the workpiece on the fixture base plate;

[0016] S2. Install the column on the left and right ends of the fixture base plate. After installation, install the irregular frame on the column. Then install the irregular ejector pin on the irregular frame while the irregular ejector pin does not press against the workpiece.

[0017] S3. Starting from the left or right end of the workpiece, cut the edging and the seat along the connecting section. During the cutting process, divide the cutting path into multiple segments. For each segment cut, install the side ejector pins of that segment and make the side ejector pins abut against the front and rear sides of the bottom of the edging, while making the irregular ejector pins abut against the top of the edging. After the cutting is completed, remove the milling fixture and obtain the metal edging.

[0018] The beneficial effects of this invention are: 1. Rough machining is performed by a five-axis machine tool, which can process five surfaces in one clamping, avoiding errors caused by multiple clampings, and reducing process changeover time.

[0019] 2. After each rough machining is completed, stress-relieving heat treatment is performed to remove residual stress and processing stress in the material, ensuring processing quality.

[0020] 3. During finishing, the inner surface is machined first, followed by the outer surface. This ensures sufficient rigidity and smooth machining of the inner surface by relying on the allowance of the outer surface. When machining the outer surface, a layered machining method is used, which can achieve the finished product machining of fan blade metal edging with a minimum thickness of 0.39mm. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the metal edging structure;

[0022] Figure 2 This is a schematic diagram of the blank structure;

[0023] Figure 3 This is a schematic diagram of the blank structure after rough milling.

[0024] Figure 4 This is a schematic diagram of the rough machining tooling structure;

[0025] Figure 5 This is a schematic diagram of the workpiece after rough machining.

[0026] Figure 6 This is a schematic diagram of the finished outer surface.

[0027] Figure 7 This is a schematic diagram of the milling fixture structure;

[0028] Figure 8 This is a schematic diagram of a milling fixture with a workpiece clamped in place. Detailed Implementation

[0029] A type of processing such as Figure 1 The method for edge banding the fan blades with metal (100) as shown includes the following steps: Step 1: After the blank passes ultrasonic testing, rough milling is performed using a three-axis CNC machine tool or a five-axis CNC machine tool. Figure 2The rectangular TC4 titanium alloy blank 200 shown; the blank 200 after rough milling is as follows: Figure 3 As shown (the dotted line in the figure represents the edge-binding shape that needs to be processed), it includes an upper edge-binding blank 300 for processing into an edge and a lower seat blank 400 for processing into a seat. The seat blank 400 is processed to form pressure plate grooves 401 located on the front and rear sides of the seat blank, and lifting holes are processed to facilitate subsequent installation onto the tooling. The bottom surface of the blank is finely finished to form a reference plane and reference holes are machined on the bottom surface. It is necessary to pay attention to controlling the position and diameter of the two positioning pin holes (reference holes), as well as the flatness of the bottom surface of 0.02mm.

[0030] Step 2, Five-axis rough machining; using the machined datum plane and datum hole as datums, the blank is fixed in place by the pressure plate 2 through the pressure plate groove 401. Figure 4 After mounting the roughing fixture 500 as shown, the upper edge of the blank is roughed. During the machining process, a five-axis CNC machine tool is used to machine the top, front, back, left, and right sides of the edge blank in one clamping operation (which can be done in multiple ways). Figure 3 (as a directional reference), after processing, as follows Figure 5 As shown, a 5mm allowance is left on one side. At the same time, the connection between the edge blank 300 and the seat blank 400 is machined to form an inwardly recessed connecting section 600. The machining tool can be a 20mm diameter rounded end mill with a cutting speed of 80 meters per minute. Side-edge cycloidal milling is used with a feed per tooth of 0.1mm. The high cutting speed and feed rate improve the roughing efficiency of the part.

[0031] Step 3: Stress relief through heat treatment. A box furnace was used, with a temperature control setting of 550±10℃ and a holding time of 240-255 minutes. Cooling was performed by air cooling to room temperature. After heat treatment, the datum surface and datum hole were modified to ensure datum coincidence in subsequent processes. Specifically, the datum surface was machined, the diameter of the datum hole was enlarged, and the locating pins on the tooling and parts were modified to facilitate proper assembly.

[0032] Step 4: Five-axis secondary roughing; Using the corrected reference plane and reference hole as references, after fixing the workpiece on the roughing fixture, perform secondary roughing on the upper edge of the blank. After machining, leave a 2mm allowance on each side. The machining equipment is a five-axis CNC machine tool, and the machining tools are D8, D10, D12, D16, etc. Round corner milling cutters. Because the V-shaped deep groove of the part also needs to be measured, a D8 round corner milling cutter is used. Considering that the final part is a thin-walled and easily deformable part, it is difficult to control the deformation of the material by directly finishing the material. Therefore, secondary roughing is added here to gradually reduce the allowance through multiple roughing operations.

[0033] Step 5: Perform heat treatment again to relieve stress, following the steps in Step 3. After heat treatment, correct the datum surface and datum hole to ensure that the datum is in good condition.

[0034] Step Six: Five-Axis Finishing; Due to the thin-walled nature of the part, the machining process needs to be divided within the operation; otherwise, chatter is easily generated during machining, making machining difficult. In this solution, a machining scheme of finishing the inner surface first and then finishing the outer surface is adopted. Specifically, using the modified datum plane and datum hole as datums, after fixing the workpiece on the roughing fixture 500, the inner surface of the groove formed by the concave top of the edge blank is semi-finish milled. After semi-finish milling, a allowance of 0.15mm is left. After semi-finish milling, finish milling is performed to eliminate the allowance. The remaining 5mm allowance needs to ensure that the workpiece has sufficient rigidity to meet the machining requirements during semi-finish milling and finish milling of the inner surface. During the machining of the inner surface, R2*4 degrees is used. Tapered ball end mills, R1.5*3 degree tapered ball end mills, cutting speed 80 meters per minute, feed per tooth 0.08mm, then finishing to 0 position. The program uses a reciprocating machining strategy to reduce idle time and improve machining efficiency. During internal surface machining, the 2mm allowance on the external surface ensures structural rigidity and guarantees normal machining of the internal surface. After machining the internal surface, the external surface of the edge blank is machined. If the external surface is machined in one semi-finish milling and finish milling from top to bottom, the 0.39mm wall thickness cannot guarantee rigidity, and machining cannot continue. Therefore, when there is still a 2mm allowance on the external surface, the external surface is machined in layers, such as... Figure 6 As shown, during the machining of the outer surface, the outer surface is divided into multiple segments from top to bottom. Figure 6 The curve on the 300mm edge blank is used to indicate the segment position. Curve L in the figure is one of the curves (specifically divided into 10 layers). The excess material left on the outer surface is eliminated by precision milling along the length direction.

[0035] Step 7, using as follows Figure 7 , Figure 8 The milling fixture shown cuts off the upper edge and the lower seat at the connecting section. The milling fixture includes a fixture base plate 1, which is used to place the workpiece to be milled. A pressure plate 2 is installed on the fixture base plate 1 to fix the seat on the fixture base plate. A special-shaped frame 3 located directly above the edge is also installed on the fixture base plate 1 through a column 4. Special-shaped ejector pins 5 extending toward the top groove of the edge are evenly threaded on the special-shaped frame 3. The milling fixture also includes multiple sets of side ejector pins 6 evenly distributed along the length of the edge. The side ejector pins 6 are installed on the side mounting base 7 and each set of side ejector pins is symmetrically distributed on the front and back sides of the bottom of the edge.

[0036] The steps for cutting the edge and the base using a milling fixture are as follows: S1, Install the fixture base plate 1 on the machine tool, insert the pressure plate 2 into the pressure plate groove 401, and then fix the workpiece on the fixture base plate.

[0037] S2. Install the columns 4 at the left and right ends of the fixture base plate 1. Since the 11 special-shaped thimbles 5 and the 11 positioning holes of the special-shaped frame 3 are custom-made to match each other, they need to be installed one by one according to the marks on each thimble and hole. Do not install them randomly in the wrong holes. Just install the thimbles on the special-shaped frame. There is no need to hold the parts temporarily.

[0038] S3. Start from the left or right end of the workpiece and cut off the edge wrapping and the seat body along the connecting section. During the cutting process, install the 11 groups of side thimbles 6 on the fixture base plate 1 step by step according to the cutting sequence of the processing program. Specifically, cut one section and install one group of thimbles, and gradually cut the part in segments. Since when cutting, the part will vibrate and sag due to being suspended, install and tighten the corresponding side thimbles 6 for the cut part to hold the bottom sides of the metal edge wrapping, and at the same time tighten the upper special-shaped thimbles 5 to hold the metal edge wrapping from above, and so on, gradually cut the part completely. Since each milled part can be held by the special-shaped thimbles above the metal edge wrapping at the top of the metal edge wrapping, and at the same time can be supported by a group of side thimbles at the front and back sides of the bottom curved surface of the metal edge wrapping, such a rigid clamping point can effectively ensure the stability of subsequent milling. It should be noted that the pressure plate 2 does not need to be disassembled throughout the process, and the pressure plate 2 can only be removed after the cutting is completed to obtain the metal edge wrapping. This step effectively assists the process cutting through the multi-angle vector thimbles, completes the processing of the metal edge wrapping. Due to the good clamping rigidity, convenient operation, the cutting joint at the front edge is reduced and controlled within 0.05 mm, which reduces the workload of subsequent filing and polishing and improves the production beat of the part.

[0039] Step Eight: Filing and Repairing. Mainly remove the cutting joints in the filing and repairing area, remove the cutting joints in the arc transition area of the inner cavity of the deep V groove, remove all edge burrs but keep the sharp edges to make the surface consistency of the product better. Then conduct fluorescence penetration inspection to detect surface defects of the machined product. After passing the inspection, mark the product.

[0040] Above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those familiar with the technology within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for processing metal edging on fan blades, characterized in that, It includes the following steps: Step 1: Rough milling of the blank; The blank includes an upper edge blank for processing into an edge and a lower seat blank for processing into a seat body. The seat blank is machined to form pressure plate grooves on the front and rear sides of the seat blank. The bottom surface of the blank is finished to form a reference plane and a reference hole is machined on the bottom surface. Step 2, five-axis rough machining; using the machined reference plane and reference hole as references, after fixing the blank on the rough machining fixture through the pressure plate groove, rough machining is performed on the upper edge blank. During machining, the five-axis machine tool is used to machine the top, front, back, left and right sides of the edge blank in one clamping. After machining, a single-sided allowance A is left. At the same time, the connection between the edge blank and the seat blank is machined to form an inwardly recessed connecting section. Step 3: Heat treatment to relieve stress. After heat treatment, the datum surface and datum hole are corrected. Step 4, five-axis secondary rough machining; using the corrected reference plane and reference hole as references, after fixing the workpiece on the rough machining fixture, perform secondary rough machining on the upper edge blank of the blank, and leave a single-sided allowance B after machining, B is less than A; Step 5: Perform a second heat treatment to relieve stress, and then correct the reference surface and reference hole after the heat treatment; Step Six: Five-axis finishing; Using the corrected reference plane and reference hole as references, after fixing the workpiece on the roughing fixture, the inner surface of the groove formed by the concave top of the edge blank is semi-finish milled. After semi-finish milling, a allowance C is left, which is less than B. After semi-finish milling, finish milling is performed to eliminate the allowance. The remaining allowance B needs to ensure that the workpiece has sufficient rigidity to meet the processing requirements when semi-finishing and finish milling the inner surface. After machining the inner surface, the outer surface of the edge blank is then machined. When machining the outer surface, the outer surface is divided into multiple segments from top to bottom, and the allowance B left on the outer surface is eliminated by finish milling segment by segment. Step 7: Cut the upper edging and the lower base at the connecting section; Step 8: Trim the edges and inspect for surface defects; In step seven, a milling fixture is used to cut the edging and the base. The milling fixture includes a fixture base plate for placing the workpiece to be milled. A pressure plate for fixing the base to the fixture base plate is installed on the fixture base plate. A special-shaped frame located directly above the edging is also installed on the fixture base plate via a column. Special-shaped ejector pins extending toward the top groove of the edging are evenly threaded onto the special-shaped frame. The milling fixture also includes multiple sets of side ejector pins evenly distributed along the length of the edging. The side ejector pins are installed on side mounting seats, and each set of side ejector pins is symmetrically distributed on the front and back sides of the bottom of the edging.

2. The processing method for metal edging of fan blades according to claim 1, characterized in that: The blank is made of TC4 titanium alloy. The heat treatment method in steps three and five is as follows: heat the workpiece to 550±10℃, hold it for 240min-255min, and then air cool it to room temperature.

3. The processing method for metal edging of fan blades according to claim 2, characterized in that: The steps for cutting the edge and the base using the milling fixture are as follows: S1, Install the fixture base plate on the machine tool, insert the pressure plate into the pressure plate groove, and then fix the workpiece on the fixture base plate; S2. Install the column on the left and right ends of the fixture base plate. After installation, install the irregular frame on the column. Then install the irregular ejector pin on the irregular frame while the irregular ejector pin does not press against the workpiece. S3. Starting from the left or right end of the workpiece, cut the edging and the seat along the connecting section. During the cutting process, divide the cutting path into multiple segments. For each segment cut, install the side ejector pins of that segment and make the side ejector pins abut against the front and rear sides of the bottom of the edging, while making the irregular ejector pins abut against the top of the edging. After the cutting is completed, remove the milling fixture and obtain the metal edging.

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