Method for milling molded surface of blade tip of overhaul machine after additional material

Abstract

The invention discloses an overhaul machine blade tip additional material rear molded surface milling method. The method comprises the following steps that 1, a special clamp is adopted to be connected with a five-axis numerical control milling main shaft, and a blade is installed on the clamp; 2, a measuring system is adopted to measure the blade and generate a tool path; step 3, processing an additional material blade body part; 4, machining the redundant part of the blade tip of the blade; 5, the additional material blade body allowance is removed; in the step 3, when the additional material blade body part is machined, the allowance ranging from 0.02 mm to 0.05 mm is reserved for the back of a blade body molded surface basin, and the allowance ranging from 0.1 mm to 0.15 mm is reserved at the R position of the front edge and the rear edge. The method can greatly reduce the maintenance cost of the blade when the aero-engine is maintained after the life, facilitates the rapid repair of the blade when the aero-engine is maintained after the life, and improves the repair efficiency. And meanwhile, the cost is saved, and the blades with intact tenons and abraded and warped blade tips are secondarily processed and utilized.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical processing, and in particular relates to a method for milling a blade tip of an overhaul machine blade after material addition. Background Art

[0002] Aircraft engine blades are the core components of aircraft engines, with the characteristics of large blade twist, complex surface, and high comprehensive performance requirements. After the blades are installed and used, the blade tips will wear and shorten, and the blade tip profile will warp. If the engine is repaired by replacing new blades, the engine maintenance cost will be high. For used blades, the tenons are generally intact and meet the use requirements. If the tenons are intact but the blade tips are worn and warped, the blade tips are repaired and meet the use requirements. After the overhauled blades are installed again, the engine maintenance cost will be greatly reduced. However, the blade body profile of the overhauled blades is quite different from the theoretical model, and the CNC machining of the additive welding part of the blade tip is quite difficult. It is very technically difficult to achieve a seamless connection between the repaired area and the unrepaired area.

[0003] The Chinese invention patent with publication number CN115740950B discloses a laser deposition repair method for DZ125 alloy turbine blades based on reverse modeling. It solves the problem of difficult to ensure the repair quality due to uneven wall thickness of the tip of the high-pressure turbine working blade and deformation after use. Through the test piece level repair test and performance evaluation and the repair test verification of actual parts, the extension repair of the blade tip wear defects of the parts was successfully achieved. The metallurgical properties and dimensional accuracy of the repaired parts meet the requirements of engine use. This solution method is complex and has many steps, which is not suitable for mass production. Summary of the invention

[0004] In order to solve the above problems, the present invention aims to provide a method for milling the blade tip of an overhaul machine blade after material addition.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a method for machining the tip of a blade of an overhaul machine by adding material and then milling the blade, comprising the following steps:

[0006] Step 1: Use a special fixture to connect with the five-axis CNC milling spindle and install the blade on the fixture;

[0007] Step 2: Use the measuring system to measure the blade and generate the tool path;

[0008] Step 3: Processing the additive blade part;

[0009] Step 4: Process the excess part of the blade tip;

[0010] Step 5: Remove the excess of the additive blade;

[0011] When processing the added material blade part in step 3, a margin of 0.02mm-0.05mm is left on the back of the blade body basin, and a margin of 0.1mm-0.15mm is left at the front and rear edges R.

[0012] Preferably, the special clamp of step 1 includes a clamp base and an auxiliary support arranged at the upper end of the clamp base, the clamp base includes a disc base and a support seat arranged at the center of the disc base and integrally formed, the auxiliary support is vertically arranged at the upper end of the clamp base and the clamping space is matched with the end face of the blade base.

[0013] Preferably, the fixture base of the special fixture is connected to the five-axis CNC milling spindle, the tenon part of the blade is placed on the support seat of the fixture base, and the blade base is vertically placed in the clamping space and fixed.

[0014] Preferably, the augmented blade body portion of the blade is higher than the auxiliary support of the fixture.

[0015] Preferably, the clamped blades are measured by a measuring system, the measured results are compared with the theoretical model, and the five-axis CNC milling machine generates a tool trajectory based on the measurement results.

[0016] Preferably, the step 4 is to cut off the excess portion of the blade tip using an end mill.

[0017] Preferably, in step 5, the excess of the additively-made blade body is removed by polishing.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. This method can greatly reduce the maintenance cost of the blades of the aircraft engine at the end of its service life, which is conducive to the rapid repair of the blades of the engine at the end of its service life and improves the efficiency of rework. At the same time, it saves costs and reprocesses the blades with intact tenons and worn and warped blade tips for reuse.

[0020] 2. This processing method has simple steps, is easy to operate, and achieves seamless connection between the repaired area and the unrepaired area. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a three-dimensional schematic diagram of a blade clamped by a special clamp in the present invention;

[0023] Figure 2This is a comparison diagram between the theoretical model and the actual surface in the present invention; Figure 3 A comparison diagram of the theoretical processing trajectory and the actual processing trajectory in the present invention; In the figure, 1- fixture base; 2- auxiliary support; 3- blade base; 4- additive blade body. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0025] This method has done the following research:

[0026] 1. Research on the difference of overhaul blade profile. Due to the use of overhauled machine blades, each blade has bending deformation and the degree of deformation of each blade is not consistent. By comparing the actual profile size of the blade body with the theoretical model, the difference between the two is obtained. Figure 2 The white part is the theoretical model, and the red part is the actual position of the detected part. Since the situation of each overhaul blade is different, it is difficult to process qualified parts with the theoretical tool path during the processing. Only one piece can be measured and processed to achieve a smooth transition between the overhaul blade matrix and the additive part. In order to ensure that the blade is processed qualifiedly, the adaptive processing method must be adopted for processing. The results are fed back to the adaptive processing software through inspection results, and the processing tool path is automatically adjusted through the software, and the program is regenerated when the blade is processed qualifiedly.

[0027] 2. Research on CNC milling blade body profile, after measuring, the five-axis CNC milling cutter is used for processing. The five-axis milling equipment will adjust the processing path according to the actual position of the detected parts, see Figure 3 The blue one is the theoretical processing path, and the red one is the actual processing path. Due to the change of each processing path, the inclination angle of the tool relative to the part will also change. Since the blade profile is a complex curved surface, affected by the curvature, the blade tip will be over-cut or under-cut in the processing process. In order to ensure that the blade will not be over-cut or under-cut locally, different allowances are left at different positions according to the polishing processing allowance to ensure that the local area will not be over-cut or under-cut. Finally, the size of the blade profile is guaranteed by polishing.

[0028] 3. Research on CNC equipment. Due to the complex curved surface of the blade back, the machine tool probe can only be inspected perpendicular to the blade surface during detection. The machine tool is affected by the ambient temperature, the thermal expansion and contraction of the spindle, and the probe has errors in Z-direction detection. The detection system is a high-end precision equipment with high ambient temperature requirements. Large temperature differences during processing will cause inconsistent spindle expansion and contraction, uneven force on parts, and changes in tool length. Therefore, the tool connection and size of parts are difficult to control. In order to ensure that the blade can be processed to the required standard and eliminate clamping and measurement errors, processing equipment with a measurement system must be selected. Before processing, the position of the blade and the margin of the processing part must be accurately measured to ensure that the blade is processed to the required standard. At the same time, the data is transmitted to the adaptive system to generate a new program segment.

[0029] 4. Research on CNC fixtures. The structure of the additive blades is different from that of the new blades. When processing the new blades, the tenon can be used to position the process boss for clamping. However, the additive blades do not have process bosses and can only be positioned and clamped by the tenon. Since the blade body surface is very thin and cannot bear force, it will be deformed during processing. Although auxiliary fixtures are used to clamp the blade body surface to eliminate the force on the blade body surface, errors caused by the tool letting phenomenon will still occur during high-speed cutting. In order to ensure the stability of the blade during processing, the blade tenon working surface with a tolerance of only 0.007mm is used for positioning, and the blade tenon ground is used for clamping to ensure that the blade tenon working surface is completely fitted. At the same time, the blade body profiling auxiliary support is added to the non-processing part of the blade body to reduce vibration during processing and ensure that the blade is not clamped.

[0030] Based on the results of the above research, in order to ensure that the blade surface meets the requirements, a fixture with a tenon clamp to clamp the blade and add auxiliary support for profiling is used for processing on a five-axis CNC milling machine with a measuring system and an adaptive system. During processing, a 0.02mm-0.05mm margin is left for the blade basin when facing back, and a 0.1mm-0.15mm margin is left at the front and rear edges R, and then polishing is performed to ensure the quality of the blade, so that the obtained blade meets the use requirements.

[0031] Reference Figure 1 The surface processing method of the blade tip after material addition includes a special fixture, a measuring system, a blade body milling cutter, an end face milling cutter, a five-axis CNC milling machine, and a polishing machine; the special fixture includes a fixture base 1, an auxiliary support 2 arranged at the upper end of the fixture base 1, the fixture base 1 includes a disc base and a support seat arranged at the center of the disc base and integrally formed, the auxiliary support 2 is vertically arranged at the upper end of the fixture base 1 and the clamping space is matched with the end face of the blade base 3.

[0032] The steps are as follows:

[0033] Step 1: The fixture base 1 is connected to the five-axis CNC milling spindle, the auxiliary support 2 is connected to the fixture base 1, the tenon part of the blade is placed on the support seat of the fixture base 1, the blade base 3 is vertically placed in the clamping space and fixed, and the auxiliary fixture 2 clamps the blade body of the blade base 3;

[0034] Step 2: Measure the clamped blades through the measurement system, compare the measured results with the theoretical model, and generate the tool path based on the measurement results by the five-axis CNC milling machine;

[0035] Step 3: Considering the measurement system and the curvature of the blade profile, leave a margin of 0.02mm-0.05mm on the blade profile 4 and a margin of 0.1mm-0.15mm at the leading and trailing edges R before processing;

[0036] Step 4: After the additive blade body 4 is processed, the excess part of the blade tip is cut off using an end milling cutter;

[0037] Step 5: Use a polishing machine to remove the excess of the additive blade.

[0038] Example

[0039] Step 1: The fixture base 1 is connected to the five-axis CNC milling spindle, so that the blade can rotate on the x-axis of the equipment, while ensuring that the center of the blade, the center of the fixture and the A-axis of the equipment coincide; the auxiliary support 2 is connected to the fixture base 1 to ensure the stability of the blade processing process, prevent vibration during processing, and improve the processing quality of the blade surface; the blade base 3 is vertically clamped in the space of the fixture, and the blade tenon is used for positioning, while the center of the blade coincides with the A-axis of the equipment; the auxiliary fixture 2 holds the blade base 3, and the held part is 10mm away from the processing part to ensure that the fixture and the tool do not interfere during processing. "

[0040] Step 2: Use the measurement system to measure the processing part of the clamped blade, and compare the measured results with the theoretical model. Since the position of each blade is different during the tip additive process, the measurement results need to be fed back to the adaptive software system. According to the adaptive processing system, a new digital axis CNC processing program will be generated.

[0041] Step 3: Considering the error of the measurement system, the change of the curvature of the blade profile and the requirement that the roughness of the final blade profile is Rao.4, the blade body after CNC milling cannot meet the design requirements. Therefore, during the CNC milling process, the blade body 4 profile has a margin of 0.02-0.05mm in the back direction of the basin, and a margin of 0.1-0.15mm at the front and rear edges R of the blade body 4.

[0042] Step 4: After the processing of the additive blade body 4 is completed, the excess part of the blade tip is cut off with an end mill. Since the roughness requirement is Ra0.4, the roughness of the cut does not meet the requirement. When cutting, a 0.02mm margin needs to be left for polishing to ensure the quality of the added blade.

[0043] Step 5: Polish the blade 4 after milling, use a wool felt wheel to process the back direction of the blade 4, use a rubber wheel to process the front and rear edges R of the blade 4, and use three-coordinate measurement to measure the processed blade 4. The contour tolerance of the blade 4 and the topographic tolerance of the trailing edge R must meet the requirements.

[0044] The above is a detailed introduction to the milling method for the tip of the overhaul machine blade after material addition provided by the present invention. This article uses specific examples to illustrate the structure and working principle of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for milling the blade tip of an overhaul machine after material addition, characterized in that: The following steps are included: Step 1: Use a special fixture to connect with the five-axis CNC milling spindle and install the blade on the fixture; Step 2: Use the measuring system to measure the blade and generate the tool path; Step 3: Processing the additive blade body (4); Step 4: Process the excess part of the blade tip; Step 5: Remove the excess of the augmented blade (4); When processing the added blade body (4) in step 3, a margin of 0.02 mm to 0.05 mm is left on the back of the blade body basin, and a margin of 0.1 mm to 0.15 mm is left at the front and rear edges R.

2. The method for milling the blade tip of an overhaul machine blade after material addition according to claim 1, characterized in that: The special clamp of step 1 comprises a clamp base (1), an auxiliary support (2) arranged at the upper end of the clamp base (1), the clamp base (1) comprises a disc base and a support seat arranged at the center of the disc base and integrally formed, the auxiliary support (2) is vertically arranged at the upper end of the clamp base (1) and the clamping space is arranged to match the end face of the blade base (3).

3. A method for milling the blade tip of an overhaul machine according to claim 1 or 2, characterized in that: The fixture base (1) of the special fixture is connected to a five-axis CNC milling spindle, the tenon portion of the blade is placed on a support seat of the fixture base (1), and the blade base (3) is vertically placed in the fixture space and fixed.

4. The method for milling the blade tip of an overhaul machine blade after material addition according to claim 3, characterized in that: The added material blade body (4) portion of the blade is higher than the auxiliary support (2) of the fixture.

5. The method for milling the blade tip of an overhaul machine after material addition according to claim 1, characterized in that: The clamped blades are measured by the measuring system, and the measured results are compared with the theoretical model. Based on the measurement results, the five-axis CNC milling machine generates the tool trajectory.

6. The method for milling the blade tip of an overhaul machine after material addition according to claim 1, characterized in that: The step 4 is to cut off the excess part of the blade tip with an end mill.

7. The method for milling the blade tip of an overhaul machine blade after material addition according to claim 1, characterized in that: In step 5, a polishing machine is used to remove the excess of the augmented blade body (4).

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