Machining method of aero-engine heavy frame

Abstract

The invention discloses a method for machining a heavy frame of an aero-engine, which comprises the following steps of: embedding a plurality of supporting blocks in notches in the front surface of the heavy frame, and fixing the supporting blocks on the heavy frame by using screws. The end faces of all the supporting blocks are machined on the same plane, and then the back face of the heavy frame is roughly milled. Then the supporting blocks are disassembled, the back face of the heavy frame serves as a support, and the bottom face of the heavy frame groove is roughly milled; the supporting blocks are embedded into the notches in the front face of the heavy frame again and fastened through the screws, the end faces of all the supporting blocks are machined on the same plane again, the back face of the heavy frame is subjected to finish milling to meet the size requirement, then the supporting blocks are detached, and the bottom face of the heavy frame groove is subjected to finish milling with the back face of the heavy frame as a support to meet the size requirement. On the premise that the requirements for the flatness of the back face of the heavy frame and the thickness tolerance of the groove bottom of the heavy frame are met, efficient machining of the large thin-wall heavy frame is achieved, the problems that parts are poor in rigidity and deform in the machining process are solved, and the supporting blocks can be repeatedly used.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a machining method for an aero-engine support frame. Background Technology

[0002] aircraft engine support frame, such as Figure 1 As shown, the support frame is a large web thin-walled structure. The blank is a casting made of a difficult-to-machine titanium alloy. The back and front groove bottom of the support frame need to be machined to ensure that the thickness of the groove bottom is 2±0.05mm and the flatness tolerance of the back of the support frame is no more than 0.1mm.

[0003] Due to the poor rigidity of the support frame, it is prone to deformation during processing. There are three sets of lifting lugs on the front of the support frame that are higher than the groove opening. When milling the back of the support frame, there is no clamping process edge, so multiple pads are needed to support the groove opening. It is difficult and time-consuming to align the back of the support frame. At the same time, multiple pressure plates are needed to press the back of the support frame. During milling, the pressure plates should be avoided. After milling, the pressure plates should be adjusted to the machined plane, and then the unmachined surface should be removed.

[0004] The problems with the above processing method are: the groove surface is the surface of the casting, which has poor flatness; there are gaps when the pad blocks are used for support; the support frame deforms when the pressure plate is pressed on the back; when the pressure plate is changed, the support frame returns to its deformed state, resulting in a tool joint between adjacent surfaces of the two processing operations; the flatness and thickness tolerances do not meet the design requirements, which affects the performance of the engine. Summary of the Invention

[0005] The present invention aims to provide a processing method for aero-engine support frames, which achieves efficient processing of large thin-walled support frames while meeting the requirements for the flatness of the back surface of the support frame and the thickness tolerance of the bottom of the support frame groove.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for manufacturing an aircraft engine support frame, comprising: Step 1: Embed N support blocks (N≥6) into the slots on the front of the support frame. The support blocks are cuboids. Two support block clearance slots parallel to the front and rear faces of the support blocks are opened on the lower end face of the support blocks. Screw holes are opened on the front and rear faces of the support blocks, and the screw holes are connected to the support block clearance slots. A support block clamping slot parallel to the lower end face of the support block is opened on the left or right end face of the support block. Embed the two reinforcing ribs on the support frame into the two support block clearance slots of the support blocks. Insert screws into all the screw holes and tighten all the screws on the N support blocks until the ends of the screws enter the support block clearance slots to clamp the reinforcing ribs, thereby fixing the N support blocks on the support frame. Step 2: Place the support frame on the machine tool workbench, using the back of the support frame as support. Set multiple pressure plates around the edges of the front of the support frame. Check the gap between the back of the support frame and the workbench under the pressure plates. Fill the gap with filler material and then press the support frame tightly. Step 3: Mill the upper surfaces of N support blocks to make the upper surfaces of the support blocks in the same plane with a height error of less than 0.01mm; Step 4: Using the upper end face of the support block milled in Step 3 as a support, press the support block pressing groove on the support block, and machine the back of the support frame, leaving a 0.3mm to 0.5mm allowance on the back of the support frame; Step 5: Remove all support blocks from the support frame; Step 6: Using the back of the support frame as support, rough mill the bottom surface of all support frame grooves, leaving a margin of 0.3mm to 0.5mm; Step 7: Repeat steps 1 to 3 to finish the back of the support frame to the required dimensions; Step 8: Remove all support blocks from the support frame and perform precision machining on the bottom surface of all support frame slots to meet dimensional requirements.

[0007] As one option, the support block clearance groove and the support block clamping groove in step 1 are both straight grooves with rectangular cross sections.

[0008] As one option, the filler in step 2 is a copper sheet.

[0009] As one option, in step 4, the tool used for milling the back of the support frame is a carbide end mill with a diameter of 50 mm and a tip radius of 0.5 mm, and the depth of cut for each layer is 0.5 mm to 0.8 mm.

[0010] As one option, in step 7, the tool used for milling the back of the support frame is a solid carbide end mill with a diameter of 20 mm and a tip radius of 0.5 mm, and the depth of cut for each layer is 0.15 mm to 0.25 mm.

[0011] As one approach, in steps 4 and 7, the milling cutter's tool path is a unidirectional path, the cutting distance is 70% to 85% of the tool diameter, and the cutting direction is parallel to the direction of the support block clamping groove.

[0012] Compared with the prior art, the present invention has the following characteristics: (1) This invention is applicable to the processing of large thin-walled load-bearing frames without process edge slots. The load-bearing frame processing method of this invention solves the problems of poor casting blank condition, poor part rigidity and deformation during processing, and improves processing efficiency and stability. (2) The support block of the present invention can be reused, saving the investment in special fixtures in the development of new products and accelerating the development of new products. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the load-bearing frame structure in this invention; Figure 2 This is a front view of the load-bearing frame structure in this invention; Figure 3 This is a schematic diagram of the clamping of the support frame and support block in this invention; Figure 4 This is a schematic diagram of the support block structure in this invention; Figure 5 This is a schematic diagram of the tool path in this invention; Figure 6 This is a schematic diagram showing the position where the pressure plate is pressed against the perimeter of the front of the support frame in this invention; In the diagram: 1. Support frame; 2. Support block; 3. Screw; 101. Front of support frame; 102. Lifting lug of support frame; 103. Bottom of support frame groove; 104. Back of support frame; 201. Support block clamping groove; 202. Support block clearance groove; 203. Screw hole. Detailed Implementation

[0014] The present invention will be further described below with reference to specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0015] like Figure 1 and Figure 2 As shown, a large thin-walled support frame with a groove structure is provided. The support frame is mainly composed of the front side 101 of the support frame, the lifting lug 102 of the support frame, the bottom surface of the groove 103 of the support frame, and the back side 104 of the support frame. The bottom surface of the groove 103 and the back side 104 of the support frame are both surfaces to be processed.

[0016] The basic idea of ​​this invention is to embed N support blocks 2 into the slots on the front side 101 of the support frame ( Figure 1 In the cubic groove (in the middle), the support block 2 is fixed to the support frame 1 with screws 3. First, machine all the end faces of the support blocks 2 (i.e., Figure 3 The upper surface of support block 2 is on the same plane. Then, turn the frame around and rough mill the back surface 104 of the support frame. Then, remove support block 2 and, using the back surface 104 of the support frame as support, rough mill the bottom surface 103 of the support frame groove. Reinsert support block 2 into the support frame groove and tighten it with screws 3. Then, process all the end faces of support block 2 to be on the same plane again. Finish mill the back surface 104 of the support frame to the required dimensions. Then, remove support block 2 and, using the back surface 104 of the support frame as support, finish mill the bottom surface 103 of the support frame groove to the required dimensions.

[0017] like Figure 4 As shown, the support block 2 is a cuboid. Two support block clearance grooves 202 parallel to the front and rear end faces of the support block 2 are opened on the lower end face of the support block 2. Two screw holes 203 are opened on the front and rear end faces of the support block 2. The screw holes 203 are connected to the support block clearance grooves 202. A support block clamping groove 201 parallel to the lower end face of the support block 2 is opened on the left end face (or right end face) of the support block 2.

[0018] The specific processing method for aircraft engine support frames is as follows: Step 1, as follows Figure 3 Six support blocks 2 are embedded in the slots on the front of the support frame 101. Two reinforcing ribs on the support frame 1 (two parallel reinforcing ribs corresponding to the slots on the front of the same support frame) are embedded in the support block clearance slots 202. The screws 3 on each support block 2 are tightened to fix the support block 2 on the support frame 1. Step 2: Place the support frame 1 on the machine tool worktable, using the back 104 of the support frame as support, and install multiple pressure plates (e.g., on the four edges of the front 101 of the support frame) around the perimeter. Figure 6 Install 9 pressure plates at 9 locations in the middle. Check the gap between the back of the support frame 104 and the workbench below the location where the pressure plates are set. Pad with copper sheets or copper plates of appropriate thickness, and then press them down. Step 3: Mill the upper surfaces of the 6 support blocks 2 so that the upper surfaces of the 6 support blocks 2 are in the same plane and the height error of the 6 upper surfaces is less than 0.01mm (that is, the maximum height difference between the 6 upper surfaces is less than 0.01mm). Step 4: Using the upper end face of the support block 2 milled in Step 3 as support, press the support block pressing groove 201 on the support block 2, and process the back side 104 of the support frame. Use a carbide end mill with a diameter of 50mm and a tip radius of 0.5mm. The depth of cut for each layer is 0.5mm to 0.8mm, and leave a margin of 0.3mm to 0.5mm on the back side. Step 5: Remove all support blocks 2 from the support frame 1; Step 6: Using the back of the support frame 104 as support, rough mill the bottom surface 103 of all support frame grooves, leaving a margin of 0.3mm to 0.5mm; Step 7: Repeat steps 1 to 3 to finish the back side 104 of the support frame using a solid carbide end mill with a diameter of 20mm and a tip radius of 0.5mm. The depth of cut for each layer is 0.15mm to 0.25mm. Step 8: Remove all support blocks 2 from the support frame 1, and perform precision machining on the bottom surface 103 of all support frame slots of the support frame 1 to meet the dimensional requirements.

[0019] In steps 4 and 7 above, such as Figure 5As shown, the tool path is a unidirectional tool path (the dark blue dashed line in the vertical direction on the left is the downward tool path, the red dashed line in the horizontal direction above is the rapid traverse path, the dark blue dashed line in the vertical direction on the right is the retraction tool path, and the light blue solid line in the horizontal direction below is the cutting path). The cutting distance is 70% to 85% of the tool diameter, and the cutting direction is parallel to the direction of the support block clamping groove 201 to improve machining stability.

[0020] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for processing an aircraft engine support frame, characterized in that, include: Step 1: Embed N support blocks (2) into the front slot of the support frame (1), where N ≥ 6. The support block (2) is a cuboid. Two support block clearance grooves (202) parallel to the front and rear end faces of the support block (2) are opened on the lower end face of the support block (2). Screw holes (203) are opened on the front and rear end faces of the support block (2), and the screw holes (203) are connected to the support block clearance grooves (202). A strip of steel is opened on the left or right end face of the support block (2). Parallel to the lower end face of the support block (2), the support block clamping groove (201) is used to insert two reinforcing ribs on the support frame (1) into the two support block clearance grooves (202) of the support block (2), screws (3) are installed in all screw holes (203), and all screws (3) on the N support blocks (2) are tightened until the end of the screws (3) enters the support block clearance groove (202) to clamp the reinforcing ribs, thereby fixing the N support blocks (2) on the support frame (1); Step 2: Place the support frame (1) on the machine tool workbench, with the back of the support frame (104) as support, and set multiple pressure plates around the edges of the front of the support frame (101). Check the gap between the back of the support frame (104) and the workbench below the pressure plates, fill the gap with filler, and then press the support frame (1) tightly. Step 3: Mill the upper surfaces of N support blocks (2) to make the upper surfaces of the support blocks (2) in the same plane with a height error of less than 0.01mm; Step 4: Using the upper end face of the support block (2) milled in step 3 as support, press the support block pressing groove (201) on the support block (2), and process the back side (104) of the support frame, leaving a margin of 0.3mm to 0.5mm on the back side (104) of the support frame; Step 5: Remove all support blocks (2) from the support frame (1); Step 6: Using the back of the support frame (104) as support, rough mill the bottom surface (103) of all support frame grooves, leaving 0.3mm to 0.5mm. Step 7: Repeat steps 1 to 3 to finish the back of the support frame (104) to the required dimensions; Step 8: Remove all support blocks (2) from the support frame (1) and perform precision machining on the bottom surface (103) of all support frame slots to the required dimensions.

2. The method for processing an aero-engine support frame according to claim 1, characterized in that: The support block clearance groove (202) and support block pressing groove (201) in step 1 are both straight grooves with rectangular cross sections.

3. The method for processing an aero-engine support frame according to claim 1, characterized in that: The filler in step 2 is a copper sheet.

4. The method for processing an aero-engine support frame according to claim 1, characterized in that: In step 4, the tool used to mill the back side (104) of the support frame is a carbide milling cutter with a diameter of 50 mm and a tip radius of 0.5 mm, and the cutting depth of each layer is 0.5 mm to 0.8 mm.

5. The method for processing an aero-engine support frame according to claim 1, characterized in that: In step 7, the tool used to mill the back side (104) of the support frame is a solid carbide milling cutter with a diameter of 20 mm and a tip radius of 0.5 mm, and the depth of cut for each layer is 0.15 mm to 0.25 mm.

6. The method for processing an aero-engine support frame according to claim 1, characterized in that: In steps 4 and 7, the milling cutter's tool path is a unidirectional path, the cutting distance is 70% to 85% of the tool diameter, and the cutting direction is parallel to the direction of the support block clamping groove (201).

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