Double-journal boring machining method for long overhanging thin-wall blade

Abstract

The invention belongs to the technical field of aero-engines and gas turbines, and particularly relates to a long overhanging thin-wall blade double-journal boring machining method which serves as a machining process method for precisely controlling errors of journals when the long overhanging thin-wall blade has the requirement for precise machining of mounting journals / process journals. Boring is used for precision machining of the double journals of the blade, the traditional journal turning / grinding machining mode is broken through, and the problems of machining chattering and machining deformation of the long-cantilever thin-wall blade are solved. The first-pass yield of shaft neck machining precision reaches 100%, the blade shaft neck machining efficiency of the structure is greatly improved, and the position precision between the shaft neck and a blade body molded surface is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aeroengines and gas turbines, and in particular relates to a double-neck boring processing method for long-overhang thin-wall blades. Background Art

[0002] The weight reduction of the fan unit of an aircraft engine directly affects the thrust-to-weight ratio and efficiency of the aircraft engine. Advanced aircraft engines at home and abroad have been committed to the weight reduction and structural optimization of fan parts. The double-journal structure at both ends of the adjustable blade profile of a fan has design features such as long cantilever, eccentric profile, thin profile wall (or hollow), etc. The total length of the blade is ≥350mm. The blade is assembled and positioned with the fan casing through the large and small journal structures at both ends. The airflow is pre-pressurized before entering the compressor to adjust the airflow size. For the blades of this structure, when turning / grinding the journals at both ends of the blade profile, even if the counterweight fixture is carefully designed and used, the processing accuracy is difficult to guarantee. In order to reduce weight, the rigidity of the blade profile is designed to be very weak. The blade profile is used as a connector between the large and small end journals. When turning / grinding the journals, the eccentric rotation of the blade profile is difficult to suppress the vibration; the blade cantilever is long and thin. During the turning / grinding process, due to the influence of large cutting force and cutting heat, the blade undergoes large bending deformation, and the coaxiality of the journals at both ends, the blade profile and the journal position cannot be guaranteed. The journals at both ends are a very important parameter for the quality control of this blade, which is directly related to the assembly accuracy with the fan casing and the reliability of the fan unit. It has become the most difficult bottleneck problem to solve in the development process of journal-adjustable blades. Summary of the invention

[0003] In view of the problems in the prior art, the present invention provides a double-journal boring processing method for long-overhang thin-walled blades. When the long-overhang thin-walled blades have the requirement of precision processing of the installation journal / process journal, the present invention serves as a processing method for accurately controlling the error of the journal.

[0004] The technical solution of the present invention is: A double-neck boring method for a long overhang thin-walled blade comprises the following steps: Step 1: Determine the type of machining center machine tool used for boring processing, and determine the equipment stroke and processing direction according to the processing position and tooling structure; Step 2: Determine the positioning reference for journal machining: Step 2.1, the rotation reference of the journal processing: determined according to the relationship between the processing journal and the blade body, the blade body rotation axis is used as the rotation reference of the journal processing; Step 2.2, the length reference of the shaft neck processing: determined according to the relationship between the shaft neck and the blade body, the blade body or the process table when processing the blade body is used as the length reference of the shaft neck processing; Step 3: Select the boring tool according to the journal size; Step 3: Design the CNC boring cycle program for the journal; Step 4: Design the journal boring process and allowance allocation: Step 4.1, rough mill the journal profile, leaving a diameter margin of 0.4~0.6mm; Step 4.2: Roughly bore the journal, leaving a diameter margin of 0.1~0.2mm; Step 4.3, precision boring the journal, leaving a diameter margin of 0mm; Step 4.4, precision boring the journal to make the dimensions of the journal within the tolerance range; Step 5, design the CNC boring cycle program for the journal, and perform machining according to the machining steps and allowances designed in step 4; Step 6: Inspect the journal according to the dimensional accuracy and technical requirements of the processed journal.

[0005] Furthermore, in the above-mentioned method for boring a double-journal shaft of a long-overhang thin-walled blade, in step 3, the boring tool is composed of a shank, an external cylindrical boring head, a boring rod, and a boring blade. The shank type is selected according to the equipment selected in step 1; the specifications of the external cylindrical boring head are determined according to the specifications of the shank; a boring rod of standard specifications is selected and pressed and connected with the external cylindrical boring head by screws, and a triangular blade is selected as the boring blade to meet the boring shaft neck diameter processing range, and the blade R angle is the same as the bottom R of the shaft neck.

[0006] Furthermore, in the above-mentioned method for boring a double-journal of a long overhang thin-walled blade, in step 4.4, the dimensions of the journals are within the tolerance range, specifically: the diameter dimension accuracy is ≤0.02mm, and the coaxiality of the large and small end journals is ≤Φ0.05mm.

[0007] Advantages and beneficial effects of the present invention: 1. The present invention solves the problem that the original journal-type blade journal cannot be tightly positioned during turning / grinding, is severely deformed, vibrates during processing, rotates eccentrically, and cannot meet the processing accuracy requirements; 2. The present invention can achieve precise control of the machining error of the journal of long overhang thin-walled blades, improve the position accuracy of the journals at both ends and the journal and the blade body profile, and thus improve the overall qualified rate and assembly reliability of the blades. From the first-time qualified rate of turning / grinding 0% to the first-time qualified rate of boring processing 100%, the blade processing quality is guaranteed, the diameter size accuracy is ≤0.02mm, the coaxiality of the large and small end journals is ≤Φ0.05mm, and the machining surface roughness reaches Ra0.8. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the structure of the adjustable blade and the large and small journals at both ends in the embodiment; Figure 2 The diagram is a diagram showing the relationship between the adjustable blade journal and the blade body rotation in the embodiment; Figure 3 Graph showing the relationship between the adjustable blade journal and the blade body in the embodiment. DETAILED DESCRIPTION

[0009] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings and examples of the specification. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention. Example

[0010] The processing object of this embodiment is the large and small journals at both ends of the adjustable blade. The structural diagram is as follows: Figure 1 As shown, the boring processing method includes the following steps: Step 1. Determine the type of machining center machine tool used for boring. The tooling structure for machining the large and small journals at both ends of the adjustable blade is a horizontal clamping blade. The total length of the tooling is 500mm. Determine to select a four-axis horizontal CNC milling (boring) machining center with a worktable and a stroke greater than 500mm. The NC control can drive the blade to automatically rotate 180° on the worktable, realize the one-time clamping of the blade, and complete the boring of the large and small journals. Step 2: Determine the positioning reference for journal machining: Step 2.1, the rotation base of the journal processing: Determine according to the relationship between the processing journal and the blade body, such as Figure 2 As shown, with the large and small end journals as the reference, the position accuracy of the blade body rotation axis is required to be within Φ0.4mm, that is, with the blade body rotation axis as the reference, the position accuracy of the two end journals is within Φ0.4mm, and the blade body rotation axis is the rotation reference for journal machining; Step 2.2, the length reference of the journal processing: Determine it according to the relationship between the processing journal and the blade body, such as Figure 3 As shown, the C surface of the large end journal is taken as the zero line of the height dimension of each section, that is, when machining the length dimension of the journal, the blade body or the process table when machining the blade body is taken as the length reference of the journal machining; Step 3: Select the boring tool according to the journal size; The boring tool consists of a handle, an external boring head, a boring bar, and a boring blade. According to the equipment selected in step 1, select a handle of HSKA63; the inner diameter of the handle of HSKA63 is Φ32mm, so select an external boring head of Φ32mm; select a standard boring bar and tighten it with the external boring head through screws, and select a triangular boring blade. When machining a journal of Φ18mm with a bottom R of 0.2mm, the blade R is 0.2mm; Step 4: Design the journal boring process and allowance allocation: Step 4.1, rough mill the journal profile, leaving a 0.5mm diameter margin; Step 4.2, rough boring the journal, leaving a diameter margin of 0.2mm; Step 4.3, precision boring the journal, leaving a diameter margin of 0mm; Step 4.4, precision boring the journal to make the dimensions of the journal within the tolerance range, where the large end shaft diameter is 18mm, the tolerance is 0.011mm; the small end diameter is 10mm, the tolerance is 0.018mm; the coaxiality of the large and small end journals is Φ0.05mm; Step 5: Design the CNC boring cycle program for the journal; Taking the boring of the small end shaft diameter as an example, the boring procedure and analysis are as follows: ...at the beginning of the program, setting the spindle safety position, etc. N10 T6 M06 goes to the tool magazine to get the tool N05 G53 X325.0 Y-200.0 The spindle moves to a safe position in the machine coordinate system N35 G53 Z540.0 N10 G52 X0.0 Y0.0 Z0.0 A-90.0 B0.0 C180.0 Flip the small end journal to the processing position angle in the local coordinate system N20 G54 opens the workpiece coordinate system N30 G1 X45.0 F3000 The tool reaches the processing position N40 G90 G1 X-31.0 Y-30.0 Z395.0 F2000 N50 X0. Y0. N60S200M04 spindle rotation N70 M08 Open coolant N80 #100=390.15 boring journal N90 Z#100 F200 N100 Z364.05F12 N110 Z385.15 F100 N120 G1 Z395.0 F2000 machining completed and retracted ...end of program, setting of spindle safety position, etc. @ TOTAL Machine Time: 11.63min Program processing time Combined with the above procedures, the processing is carried out according to the processing steps and allowances designed in step 4; Step 6: Perform shaft neck inspection according to the dimensional accuracy and technical requirements of the processed shaft neck; Processing Figure 1The adjustable blades are required to have two large and small end journals, with a large end journal tolerance of 0.011mm. According to the requirement that "the accuracy of the measuring tool should be ≤ 1 / 4 of the measured tolerance", the measurement accuracy of ordinary micrometers is 0.005mm, which cannot meet the measurement requirements. Therefore, the large end journal size is determined to be Φ18 (0 / -0.011) mm and is detected by a three-coordinate measuring machine (accuracy of 0.002mm). Similarly, the small end journal size is Φ10 (0 / -0.018) mm and is detected by a three-coordinate measuring machine (accuracy of 0.002mm).

Claims

1. A double-journal boring method for long overhang thin-walled blades, characterized in that: The following steps are involved: Step 1: Determine the type of machining center machine tool used for boring processing, and determine the equipment stroke and processing direction according to the processing position and tooling structure; Step 2: Determine the positioning reference for journal machining: Step 2.1, the rotation reference of the journal processing: determined according to the relationship between the processing journal and the blade body, the blade body rotation axis is used as the rotation reference of the journal processing; Step 2.2, the length reference of the shaft neck processing: determined according to the relationship between the shaft neck and the blade body, the blade body or the process table when processing the blade body is used as the length reference of the shaft neck processing; Step 3: Select the boring tool according to the journal size; Step 4: Design the journal boring process and allowance allocation: Step 4.1, rough mill the journal profile, leaving a diameter margin of 0.4~0.6mm; Step 4.2: Roughly bore the journal, leaving a diameter margin of 0.1~0.2mm; Step 4.3, precision boring the journal, leaving a diameter margin of 0mm; Step 4.4, precision boring the journal to make the dimensions of the journal within the tolerance range; Step 5, design the CNC boring cycle program for the journal, and perform machining according to the machining steps and allowances designed in step 4; Step 6: Inspect the journal according to the dimensional accuracy and technical requirements of the processed journal.

2. A double-journal boring method for long overhang thin-walled blades according to claim 1, characterized in that: In step 3, the boring tool consists of a shank, an external boring head, a boring bar, and a boring blade. The type of shank is selected according to the equipment selected in step 1; the specifications of the external boring head are determined according to the specifications of the shank; a boring bar of standard specifications is selected and pressed and connected to the external boring head by screws, and a triangular boring blade is selected as the boring blade to meet the boring shaft neck diameter processing range, and the blade R angle is the same as the bottom R of the shaft neck.

3. The method for boring a long overhang thin-walled blade with double journals according to claim 1, characterized in that: In step 4.4, the dimensions of the journal are within the tolerance range, specifically: diameter dimension accuracy ≤ 0.02mm, coaxiality of the large and small end journals ≤ Φ0.05mm.

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