Aero-engine multilayer stepped honeycomb workpiece processing method and electrode grinding wheel

Abstract

The application belongs to the technical field of aircraft engine part machining, and relates to a method for machining a multilayer stepped honeycomb workpiece of an aircraft engine and an electrode grinding wheel. According to the final design size and the original blank size of the multilayer stepped honeycomb workpiece, the radial and axial grinding allowances of each layer of the honeycomb workpiece are calculated, and through a plurality of rounds of electric spark machining parameter tests, the radial and axial step sizes of the multistep forming electrode grinding wheel are determined, and a multistep forming electrode grinding wheel that is shaped according to the structure of the multilayer stepped honeycomb workpiece to be machined is manufactured. After the workpiece to be machined is clamped and positioned, synchronous electric spark grinding machining is performed to obtain the multilayer stepped honeycomb workpiece. The application adopts the method for machining the multilayer stepped honeycomb by using the multistep forming electrode grinding wheel and electric spark grinding machining process parameters to grind the multilayer stepped honeycomb at one time, reduces the number of rough and fine grinding of the honeycomb, saves labor, improves production efficiency, and shortens the machining cycle of the multilayer stepped honeycomb.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine parts processing technology, and relates to a method for processing multi-layer stepped honeycomb workpieces for aero-engines and an electrode grinding wheel. Background Technology

[0002] Multi-layer stepped honeycomb seals for aero-engines are key components for improving engine efficiency. Their precision hexagonal grid structure, made of high-temperature alloy foil, effectively reduces high-pressure gas leakage, significantly improving thrust and fuel economy. However, the final dimensional accuracy and consistency of this component are highly dependent on the final grinding process. Current mainstream CNC EDM grinders use cylindrical electrode grinding wheels, which have inherent limitations in their machining process. They can only adopt a "layer-by-layer" strategy: first, precisely locate and grind all the honeycomb cores of the first step, then adjust the machine's Z-axis height and machining path through the CNC program to reposition and grind the second layer, repeating this process until all layers are processed. This serial machining logic has become a major bottleneck restricting the improvement of production efficiency and product quality.

[0003] The core drawbacks of this layer-by-layer machining method are mainly reflected in two aspects. First, there is the unavoidable error of multiple clamping and positioning. Even with the same CNC machine tool, the coordinate system needs to be reset and the tool set operation repeated every time the machining layer is switched. Even micron-level repeatability errors will have a cumulative effect on multi-layer structures, causing deviations in the relative position, concentricity, and overall height dimensions between the layers, which can easily lead to out-of-tolerance scrapping of products. Second, there is the staggering time consumption. Each layer of the honeycomb workpiece needs to independently complete the entire process from rough grinding to fine grinding, which means that the machining time increases almost proportionally with the number of layers. For components with complex structures and many layers, the grinding time accounts for a large proportion of the entire manufacturing cycle, resulting not only in low production efficiency but also in high equipment occupancy and a sharp increase in production costs, making it impossible to meet the needs of large-scale mass production of aero-engines. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for processing multi-layer stepped honeycomb workpieces for aero-engines and an electrode grinding wheel. The method uses a multi-step forming electrode grinding wheel and electrical discharge machining process parameters to grind multi-layer stepped honeycomb workpieces in one pass, reducing the number of rough and fine grinding operations, saving labor, improving production efficiency, and shortening the processing cycle of multi-layer stepped honeycomb workpieces.

[0005] This invention is achieved through the following technical solution:

[0006] A method for machining multi-layer stepped honeycomb workpieces for aero-engines includes the following steps:

[0007] Based on the final design dimensions and original blank dimensions of the multi-layer stepped honeycomb workpiece, the single-sided radial grinding allowance and axial grinding allowance of each layer of the honeycomb workpiece are calculated through the dimension chain.

[0008] Based on the single-sided radial grinding allowance and axial grinding allowance, and through multi-round EDM parameter tests, the radial step size and axial step size of the multi-step forming electrode grinding wheel are determined, and a multi-step forming electrode grinding wheel that conforms to the multi-layer stepped honeycomb workpiece structure to be processed is fabricated.

[0009] The multi-step forming electrode grinding wheel is installed on the spindle of the EDM machine, and the workpiece to be processed is clamped on the worktable of the EDM machine.

[0010] Using the multi-step forming electrode grinding wheel, after the workpiece to be processed is clamped and positioned, synchronous electrical discharge grinding is performed to obtain a multi-layer stepped honeycomb workpiece.

[0011] Preferably, the single-sided radial grinding allowance The calculation formula is:

[0012]

[0013] in, Let n be the design diameter of the nth layer of the honeycomb workpiece. is the original blank diameter of the corresponding m-th layer honeycomb workpiece.

[0014] Preferably, the axial grinding allowance The calculation formula is:

[0015]

[0016] in, Let n be the design height dimension of the honeycomb workpiece. For the first The design height dimension of the layered honeycomb workpiece.

[0017] Preferably, the multi-step shaped electrode grinding wheel is made of graphite material, preferably EDM-2 graphite material.

[0018] Preferably, when the radial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.05mm~±0.07mm, the radial step difference dimension tolerance of the multi-step formed electrode grinding wheel is controlled within ±0.01mm, and its step diameter tolerance is controlled within ±0.01mm.

[0019] When the radial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.07mm~±0.15mm, the radial step difference dimension tolerance of the multi-step formed electrode grinding wheel is controlled within ±0.02mm, and its step diameter tolerance is controlled within ±0.02mm.

[0020] Preferably, when the axial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.10mm~±0.15mm, the height step difference dimension tolerance of the middle layer of the multi-step formed electrode grinding wheel is controlled within ±0.02mm, and the height step difference dimension tolerance between the first layer and the last layer is controlled within ±0.05mm.

[0021] Preferably, the synchronous electrical discharge grinding process includes:

[0022] Call the roughing electrical parameter set to perform a synchronous rough grinding on the multi-layer stepped honeycomb workpiece;

[0023] The precision machining electrical parameter set is invoked to perform a synchronous precision grinding on the multi-layer stepped honeycomb workpiece.

[0024] Preferably, the multi-step forming electrode grinding wheel is mounted on the spindle of the EDM machine. After installation, the radial runout accuracy of the multi-step forming electrode grinding wheel and the perpendicularity of the EDM machine spindle to the worktable need to be calibrated.

[0025] Preferably, the requirements for clamping and positioning the workpiece to be processed are: before clamping the workpiece, the fixture must be aligned to ensure the runout of the fixture positioning surface and the concentricity of the fixture and the rotation center of the EDM machine's worktable.

[0026] A multi-step forming electrode grinding wheel for implementing the aforementioned processing method, wherein the body of the multi-step forming electrode grinding wheel has multiple coaxial steps that match the multi-layer stepped honeycomb workpiece structure to be processed, and the radial and height dimensions of the multiple coaxial steps are determined according to the design grinding allowance of each layer of the honeycomb workpiece.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] The purpose of this invention is to provide a method for machining multi-layer stepped honeycomb structures for aero-engines. This method employs a multi-step forming electrode grinding wheel and EDM (Electrical Discharge Machining) process parameters, eliminating the need for repeated rough and fine grinding steps. It achieves multi-layer stepped honeycomb machining in a single pass, reducing the number of rough and fine grinding operations, saving labor, improving production efficiency, and shortening the machining cycle. By eliminating the traditional layer-by-layer rough and fine grinding process, multi-layer simultaneous rough and fine grinding significantly shortens the machining cycle and reduces labor costs.

[0029] Furthermore, the appropriate rough / fine grinding process parameters prevent honeycomb lattice deformation and surface burns, while the elastic clamping claws and controlled contact gap prevent indentation and damage to the parts.

[0030] Furthermore, graphite materials have good electrical conductivity, high temperature resistance, and thermal shock resistance, making them particularly suitable for electrical discharge machining (EDM). They can ensure low electrode wear and stable processing when machining high-temperature alloy honeycomb.

[0031] Furthermore, a mathematical model for calculating radial and axial grinding allowances is presented, ensuring the scientific validity of the calculations and the accuracy of the results, thus laying a solid foundation for the precise determination of subsequent electrode dimensions.

[0032] Furthermore, the grinding wheel size can be flexibly adjusted according to the honeycomb tolerance requirements, and the three-coordinate inspection ensures reliable results, which can meet the needs of multi-layer stepped honeycomb processing or rework scenarios of aero-engines with different equipment and different tolerance requirements. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A simplified diagram of a ring-shaped honeycomb and a honeycomb lattice;

[0035] Figure 2 The diagram shows a simplified view of a honeycomb ring welding assembly. In the diagram, I, II, and III are the initial honeycomb rings, and IV is the honeycomb fixing ring. I, II, and III are respectively vacuum brazed (924) ring welded onto IV.

[0036] Figure 3 This is a diagram showing the current grinding sequence of honeycomb ring steps. In the diagram, 1, 2, 3, 4, and 5 represent the current grinding sequence of cylindrical electrode grinding wheels.

[0037] Figure 4 For the radial and axial dimension calibration of the multi-layer stepped honeycomb workpiece of the present invention;

[0038] Figure 5 This is a cross-sectional view of the multi-step formed electrode grinding wheel of the present invention;

[0039] Figure 6 This is a structural diagram of the multi-step molded electrode grinding wheel of the present invention;

[0040] Figure 7 This is a radial dimension marking diagram of the multi-layer stepped honeycomb workpiece in Example 1. The dashed line represents the initial honeycomb diagram, and the solid line represents the dimensions of the finished honeycomb.

[0041] Figure 8 This is a axial dimension marking diagram of the multi-layer stepped honeycomb workpiece in Example 1. The dashed line represents the initial honeycomb diagram, and the solid line represents the dimensions of the finished honeycomb. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] A method for machining multi-layer stepped honeycomb workpieces for aero-engines includes the following steps:

[0044] Based on the final design dimensions and original blank dimensions of the multi-layer stepped honeycomb workpiece, the single-sided radial grinding allowance and axial grinding allowance of each layer of the honeycomb workpiece are calculated through the dimension chain.

[0045] The single-sided radial grinding allowance The calculation formula is:

[0046]

[0047] in, Let n be the design diameter of the nth layer of the honeycomb workpiece. is the original blank diameter of the corresponding m-th layer honeycomb workpiece.

[0048] The axial grinding allowance The calculation formula is:

[0049]

[0050] in, Let n be the design height dimension of the honeycomb workpiece. For the first The design height dimension of the layered honeycomb workpiece.

[0051] After the dimensions of the multi-step forming electrode grinding wheel are determined and manufactured, the present invention conducts an experiment on the electrical discharge grinding process parameters. The optimization of the process parameters is very important for the processing quality of the honeycomb structure.

[0052] This invention conducted extensive testing of processing parameters on the original honeycomb model and summarized two sets of parameters suitable for part processing: rough and fine.

[0053] Based on the single-sided radial grinding allowance and axial grinding allowance, and through multi-round EDM parameter tests, the radial step size and axial step size of the multi-step forming electrode grinding wheel are determined, and a multi-step forming electrode grinding wheel that conforms to the multi-layer stepped honeycomb workpiece structure to be processed is fabricated.

[0054] The multi-step shaped electrode grinding wheel is made of graphite material, preferably EDM-2 graphite material.

[0055] When the radial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.05mm~±0.07mm, the radial step difference dimension tolerance of the multi-step formed electrode grinding wheel is controlled within ±0.01mm, and its step diameter tolerance is controlled within ±0.01mm.

[0056] When the radial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.07mm~±0.15mm, the radial step difference dimension tolerance of the multi-step formed electrode grinding wheel is controlled within ±0.02mm, and its step diameter tolerance is controlled within ±0.02mm.

[0057] When the axial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.10mm~±0.15mm, the height step difference dimension tolerance of the middle layer of the multi-step formed electrode grinding wheel is controlled within ±0.02mm, and the height step difference dimension tolerance of the first layer and the last layer is controlled within ±0.05mm.

[0058] The multi-step forming electrode grinding wheel is installed on the spindle of the EDM machine, and the workpiece to be processed is clamped on the worktable of the EDM machine.

[0059] Using the aforementioned multi-step forming electrode grinding wheel, after the workpiece to be processed is clamped and positioned, synchronous electrical discharge grinding is performed to obtain a multi-layered stepped honeycomb workpiece. The multi-step forming electrode grinding wheel is mounted on the spindle of the electrical discharge grinding machine. After installation, the radial runout accuracy of the multi-step forming electrode grinding wheel and the perpendicularity of the spindle of the electrical discharge grinding machine relative to the worktable need to be calibrated.

[0060] The requirements for clamping and positioning the workpiece to be processed are as follows: before clamping the workpiece, the fixture must be aligned to ensure the runout of the fixture positioning surface and the concentricity of the fixture and the rotation center of the EDM table.

[0061] The synchronous electrical discharge machining includes:

[0062] Call the roughing electrical parameter set to perform a synchronous rough grinding on the multi-layer stepped honeycomb workpiece;

[0063] The precision machining electrical parameter set is invoked to perform a synchronous precision grinding on the multi-layer stepped honeycomb workpiece.

[0064] A multi-step forming electrode grinding wheel for implementing the aforementioned processing method is characterized in that the body of the multi-step forming electrode grinding wheel has multiple coaxial steps that match the multi-layer stepped honeycomb workpiece structure to be processed, and the radial and height dimensions of the multiple coaxial steps are determined according to the design grinding allowance of each layer of the honeycomb workpiece.

[0065] Multi-layer grinding is achieved by using a multi-step forming electrode grinding wheel, which reduces the number of clamping operations and avoids the accumulation of errors from multiple clamping operations. At the same time, precision control methods such as grinding wheel size compensation and fixture reference calibration are used to ensure that the radial / axial dimensional tolerances of the honeycomb meet the standards.

[0066] Example 1

[0067] A method for machining multi-layer stepped honeycomb workpieces for aero-engines, comprising the following steps:

[0068] (1) Fabrication of multi-step shaped electrode grinding wheels: such as Figure 6 and Figure 5 As shown, based on the final machining dimensions of the multi-layer stepped honeycomb workpiece, the single-sided grinding allowance is calculated through the dimensional chain, and the radial and axial step dimensions of the multi-step forming electrode grinding wheel are established through parameter experiments.

[0069] like Figure 4 As shown, specifically: based on the final machining dimensions of the multi-layer stepped honeycomb workpiece, the single-sided grinding allowance of the part is calculated using a dimensional chain. The specific calculation of the single-sided grinding allowance is as follows:

[0070] First layer single-sided radial grinding allowance .

[0071] Axial grinding allowance for the first layer

[0072] Second layer single-sided radial grinding allowance .

[0073] Second layer axial grinding allowance

[0074] Third layer single-sided radial grinding allowance

[0075] 3rd layer axial grinding allowance

[0076] 4th layer single-sided radial grinding allowance

[0077] 4th layer axial grinding allowance

[0078] 5th layer single-sided radial grinding allowance

[0079] 5th layer axial grinding allowance

[0080] Note: D01, D02 and D03 are the diameters of each layer of the original three-layer honeycomb workpiece, and D1, D2, D3, D4 and D5 are the diameters of each layer of the five-layer honeycomb workpiece after grinding.

[0081] H0, H1, H2, H3, H4, and H5 are the design height dimensions of each step in the honeycomb workpiece, i.e., the axial step dimensions.

[0082] The radial and height dimensions of the multi-step molded electrode were determined through experiments. The experimental procedure is as follows:

[0083] Considering factors such as EDM parameters (pulse width, machining current, etc.), chip removal, and machining dimensional accuracy, graphite EDM-2 material was selected for the electrode.

[0084] The radial dimensions of the multi-step shaped electrode were determined through multiple rounds of iterative experiments. A and height dimensions H are as follows:

[0085] Among them, the radial dimension of the honeycomb workpiece ~ Mainly based on , , , Precision guarantee.

[0086] Through experiments, if the radial dimension of the honeycomb workpiece is... ~ The tolerance is ±0.05~±0.07mm, requiring a stepped grinding wheel. ~ The tolerance is within ±0.01mm, and the step diameter of the stepped grinding wheel... The tolerance of A should also be within ±0.01mm. A1 is generally determined by the different parts and equipment on site. (100.00mm ± 2.00mm). If the radial dimension of the honeycomb workpiece... ~ The tolerance is ±0.07~±0.15mm, requiring a stepped grinding wheel. ~ The tolerance is within ±0.02mm, and the step diameter of the stepped grinding wheel... ~ The tolerance should also be within ±0.02mm.

[0087] The axial dimensions of the honeycomb workpiece are H1 to H5 (i.e., ~ It is mainly based on the step difference of the step grinding wheel. , , , , Precision assurance. Through testing, if the axial dimensions H1 to H5 of the honeycomb workpiece have a tolerance of ±0.10 to ±0.15 mm, a step difference in the stepped grinding wheel is required. , , The tolerance is within ±0.02mm. , The tolerance should also be within ±0.05mm (since there is no honeycomb workpiece connection between H1 upwards and H5 downwards, the tolerance can be appropriately increased).

[0088] (2) Install multi-step forming electrode grinding wheel: According to the number of layers of multi-step honeycomb workpiece, install the corresponding multi-step forming electrode grinding wheel on the spindle of CNC EDM honeycomb workpiece grinding machine to ensure the radial runout accuracy of the multi-step forming electrode grinding wheel and the perpendicularity of the spindle rotation center of CNC EDM honeycomb workpiece grinding machine to the table surface.

[0089] (3) Fixture alignment: Ensure the runout of the fixture positioning surface and the concentricity of the bottom disc of the fixture with the rotary table of the CNC EDM honeycomb workpiece grinding machine;

[0090] (4) Install the parts: Install the parts on the fixture, and use a feeler gauge to check the fit between the parts and the positioning surface of the fixture to avoid indentations and damage;

[0091] (5) Rough grinding: Select the rough grinding parameters according to the rough grinding parameter card, and rough grind the 1st, 2nd, 3rd... layers of the honeycomb workpiece to the rough grinding dimensions;

[0092] (6) Fine grinding: According to the fine grinding parameter card, retrieve the fine grinding parameters and fine grind the 1st, 2nd, 3rd... layers of the honeycomb workpiece to the fine grinding dimensions;

[0093] (7) Dimensional inspection: Perform full-dimensional measurement on the honeycomb workpieces of the 1st, 2nd, 3rd... layers. After the dimensions are qualified, remove the parts from the fixture;

[0094] (8) Visual inspection: Visually inspect the surface of the honeycomb workpiece and the openings of the honeycomb workpiece.

[0095] Example 2: Machining of a 5-layer stepped honeycomb workpiece ring

[0096] The steps are: 1. Fabricating a multi-step shaped electrode grinding wheel:

[0097] Figure 7 and Figure 8 The image shows the final machining dimensions of the compressor sealing ring honeycomb workpiece. Figure 1 As shown, the existing honeycomb workpiece consists of the original 3-layer stepped honeycomb workpiece after brazing. Figure 2 Grinding to 5-layer stepped honeycomb workpiece ( Figure 3 ).

[0098] The original diameter of the first layer honeycomb workpiece was ground from ∅503.12 to ∅507.12±0.055 mm (first layer), while the height remained unchanged at 8.5 mm.

[0099] The original diameter of the second layer honeycomb workpiece was ground from ∅491.12mm to ∅501.12±0.055mm (second layer) and ∅495.12±0.048mm (third layer), and the height of 17.0mm was ground to 8.5mm (second layer) + 8.5mm (third layer).

[0100] The original diameter of the honeycomb workpiece in layer III was ground from ∅479.36mm to ∅489.36±0.048mm (layer 4) and ∅483.36±0.048mm (layer 5), and the height of 17.0mm was ground to 8.5mm (layer 4) + 8.5mm (layer 5).

[0101] From the above dimensional chain, the grinding allowances on each side are 2.00mm for the first layer, 5.00mm for the second layer, 2.00mm for the third layer, 5.00mm for the fourth layer, and 2.00mm for the fifth layer. After grinding the five-layer honeycomb workpiece, the height dimension of the honeycomb workpieces in the first, second, third, fourth, and fifth layers is required to be 8.5mm. After grinding, the runout of all honeycomb workpieces with respect to references A and B is guaranteed to be ≤0.06mm.

[0102] Electrode grinding wheel size and Figure 7 and Figure 8 Honeycomb workpiece structure surface ( Figure 7 and Figure 8 (As shown by the solid line) They correspond to each other. Considering the overall loss of the electrodes, they need to be formed in one piece according to the actual dimensions shown in the figure.

[0103] Due to the strict tolerances and high machining accuracy of the radial dimensions of the honeycomb workpiece, it is necessary to tighten the control of the radial step dimension tolerance of the stepped electrode grinding wheel. Considering the influence of discharge gap and slag removal, through parameter experiments, the diameter of the stepped electrode grinding wheel is set as ∅100±0.01mm as the reference dimension for machining the radial dimensions of the first layer of honeycomb. Based on the calculation of the honeycomb radial grinding allowance, the radial steps of the grinding wheel are determined to be 3.00±0.01mm, 2.99±0.01mm, 2.93±0.01mm, and 2.95±0.01mm, respectively, for machining the radial dimensions of the second, third, fourth, and fifth layers of honeycomb.

[0104] Because the tolerance of the height dimension (axial direction) in the honeycomb design drawings is 8.5±0.15mm, in order to ensure grinding quality, the step height dimension of the 1st and 5th layers can be appropriately relaxed. The final step electrode grinding wheel design height dimensions are 10.0±0.05mm, 8.5±0.02mm, 8.5±0.02mm, 8.5±0.02mm, and 10.0±-0.05mm, which are used for the axial dimension of the 5th layer honeycomb.

[0105] 2. Install multi-step forming electrode grinding wheels: Install the 5-step forming electrode grinding wheels on the spindle of the CNC EDM honeycomb workpiece grinder ZT-021 and ensure that they are in a conductive state; the motion accuracy of the electrode grinding wheels directly affects the machining accuracy of the honeycomb workpiece sealing ring. It is required that when the machine tool spindle rotates, the radial runout accuracy of the electrode grinding wheels be ≤0.04mm, and the perpendicularity of the machine tool spindle rotation center to the table surface be ≤0.010mm.

[0106] 3. Alignment fixture: The runout of positioning surface A is ≤0.04mm, and the concentricity between the bottom disc and the rotary table of the CNC EDM honeycomb workpiece grinding machine is ≤0.04mm;

[0107] 4. Install the parts: Align the parts with the reference outer circle of part B with a runout of ≤0.05mm. Use a feeler gauge to check the fit of the positioning surface of the parts box fixture. The gap should be ≤0.02mm to avoid indentations and damage.

[0108] 5. Rough Grinding: Following the rough grinding parameter card, retrieve the rough grinding parameters and rough grind the 1st, 2nd, 3rd, 4th, and 5th layers of the honeycomb workpiece to the rough grinding dimensions. After parameter testing and metallographic inspection of the test plate, the rough grinding parameters are as follows:

[0109] Pulse width / ON: 120μs

[0110] Pulse pause / OFF: 150μs

[0111] Processing polarity: Positive (workpiece)

[0112] Low voltage (processing) current / IP: 10A

[0113] High voltage (minimum) current / IP: 1.5A

[0114] Servo setting: 85%

[0115] Servo settings: U-axis

[0116] Electrode rotation speed: 100%

[0117] During the roughing process, high current and long pulse width parameters were used to effectively remove the surface allowance of the honeycomb workpiece structure in a shorter time. Compared with the single-layer grinding process using a cylindrical grinding wheel, which required 37 passes, the roughing process using a 5-layer stepped grinding wheel required only 11 passes, reducing the processing time from 37.29 hours to 10.25 hours. This improved the roughing efficiency by 2.64 times and also shortened the roughing cycle.

[0118] Comparison of single-step / multi-step rough grinding processes

[0119]

[0120] 6. Fine grinding: Select the fine grinding parameters according to the fine grinding parameter card, and fine grind the 1st, 2nd, 3rd, 4th and 5th layers of honeycomb workpieces to the fine grinding dimensions. After parameter testing and metallographic inspection of the test plate, the fine grinding parameters are as follows.

[0121] Pulse width / ON: 40μs

[0122] Pulse pause / OFF: 20μs

[0123] Processing polarity: Positive (workpiece)

[0124] Low voltage (processing) current / IP: 6A

[0125] High voltage (minimum) current / iP: 1.0A

[0126] Servo setting: 70%

[0127] Servo settings: U-axis

[0128] Electrode rotation speed: 100%

[0129] Surface roughness: Ra3.2 (Ra=3.2μm)

[0130] The fine grinding process is carried out under low current and narrow pulse width conditions, which effectively ensures the final precision and surface roughness of the product. Compared with 20 passes of single-layer grinding using a cylindrical grinding wheel, fine grinding using a 5-layer stepped grinding wheel requires only 4 passes, reducing the processing time from 12.5 hours to 2.5 hours, increasing the fine grinding efficiency by 4 times, and reducing the impact of human factors.

[0131] Comparison of single-step / multi-step precision grinding processes

[0132]

[0133] 7. Dimensional Inspection: Full-dimensional measurements were performed on the 1st, 2nd, 3rd, 4th, and 5th layers of the honeycomb workpiece; the dimensions were found to be within acceptable limits.

[0134] 8. Visual inspection: The surface of the honeycomb workpiece is free of defects upon visual inspection.

[0135] Example 3: Machining of a 4-layer stepped honeycomb workpiece ring

[0136] The steps are as follows: 1. Fabricate a multi-step shaped electrode grinding wheel: Based on the final machining dimensions of the multi-layer stepped honeycomb workpiece, calculate the single-sided grinding allowance through the dimensional chain, and determine the radial step dimensions and height dimensions of the multi-step shaped electrode grinding wheel through parameter experiments.

[0137] 2. Install multi-step forming electrode grinding wheels: Install the 4-layer stepped forming electrode grinding wheels on the spindle of the CNC EDM honeycomb workpiece grinder ZT-021 and ensure that they are in a conductive state; the motion accuracy of the electrode grinding wheels directly affects the machining accuracy of the honeycomb workpiece sealing ring. It is required that when the machine tool spindle rotates, the radial runout accuracy of the electrode grinding wheels be ≤0.04mm, and the perpendicularity of the machine tool spindle rotation center to the table surface be ≤0.010mm.

[0138] 3. Alignment fixture: The runout of the positioning surface is ≤0.04mm, and the concentricity between the bottom disc and the rotary table of the CNC EDM honeycomb workpiece grinding machine is ≤0.04mm;

[0139] 4. Install the parts: Install the parts on the fixture, and use a feeler gauge to check the fit of the positioning surfaces of the parts box fixture. The gap should be ≤0.02mm to avoid indentations and damage.

[0140] 5-6. Rough grinding and finish grinding: Retrieve the rough grinding parameters from the parameter card and rough grind the 1st, 2nd, 3rd, and 4th layers of the honeycomb workpiece to the rough grinding dimensions. The rough grinding and finish grinding parameters are as follows:

[0141] Pulse width / ON: 125μs (coarse) / 45μs (fine)

[0142] Pulse pause / OFF: 155μs (coarse) / 23μs (fine)

[0143] Processing polarity: Positive (workpiece)

[0144] Low-voltage (processing) current / IP: 10A (rough) / 6A (fine)

[0145] High voltage (minimum) current / IP: 1.5A (coarse) / 1.0A (fine)

[0146] Servo settings: 85% (coarse) / 75% (fine)

[0147] Servo settings: U-axis

[0148] Electrode rotation speed: 100%

[0149] Surface roughness: Ra3.2 (Ra=3.2μm)

[0150] Compared to single-layer grinding with a cylindrical grinding wheel requiring 40 passes, rough grinding with a four-layer stepped grinding wheel requires only 14 passes, reducing processing time from 41.4 hours to 14.6 hours, thus increasing rough grinding efficiency by 1.84 times. Fine grinding passes are reduced from 16 to 4, and processing time is shortened from 11.2 hours to 2.8 hours, increasing fine grinding efficiency by 3 times. The total processing time for rough and fine grinding is reduced from 52.6 hours to 17.4 hours, increasing overall processing efficiency by 2.02 times. This also reduces the impact of human factors and shortens the processing cycle of the honeycomb workpiece.

[0151] Comparison of single-step / multi-step rough grinding processes

[0152]

[0153] 7. Dimensional Inspection: Full-dimensional measurements were performed on the 1st, 2nd, 3rd, and 4th layers of the honeycomb workpiece; the dimensions were found to be within acceptable limits.

[0154] 8. Visual inspection: The surface of the honeycomb workpiece is free of defects upon visual inspection.

[0155] The advantages of this method are: when processing multi-layer stepped honeycomb, it can be ground by using multi-step forming electrode grinding wheel and EDM grinding process parameters, eliminating the need for repeated rough grinding and fine grinding steps. Using this method, multi-layer stepped honeycomb can be ground directly in one go, reducing the number of rough grinding and fine grinding honeycomb processes, saving time and shortening the processing cycle.

[0156] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0157] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0158] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0159] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for machining multi-layer stepped honeycomb workpieces for aero-engines, characterized in that, Includes the following steps: Based on the final design dimensions and original blank dimensions of the multi-layer stepped honeycomb workpiece, the single-sided radial grinding allowance and axial grinding allowance of each layer of the honeycomb workpiece are calculated through the dimension chain. Based on the single-sided radial grinding allowance and axial grinding allowance, and through multi-round EDM parameter tests, the radial step size and axial step size of the multi-step forming electrode grinding wheel are determined, and a multi-step forming electrode grinding wheel that conforms to the multi-layer stepped honeycomb workpiece structure to be processed is fabricated. The multi-step forming electrode grinding wheel is mounted on the spindle of the EDM machine, and the workpiece to be processed is clamped on the worktable of the EDM machine. Using the multi-step forming electrode grinding wheel, after the workpiece to be processed is clamped and positioned, synchronous electrical discharge grinding is performed to obtain a multi-layer stepped honeycomb workpiece.

2. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 1, characterized in that, The single-sided radial grinding allowance The calculation formula is: in, Let n be the design diameter of the nth layer of the honeycomb workpiece. is the original blank diameter of the corresponding m-th layer honeycomb workpiece.

3. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 1, characterized in that, The axial grinding allowance The calculation formula is: in, Let n be the design height dimension of the honeycomb workpiece. For the first The design height dimension of the layered honeycomb workpiece.

4. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 1, characterized in that, The multi-step shaped electrode grinding wheel is made of graphite material.

5. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 2, characterized in that, When the radial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.05mm~±0.07mm, the radial step difference dimension tolerance of the multi-step formed electrode grinding wheel is controlled within ±0.01mm, and its step diameter tolerance is controlled within ±0.01mm. When the radial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.07mm~±0.15mm, the radial step difference dimension tolerance of the multi-step formed electrode grinding wheel is controlled within ±0.02mm, and its step diameter tolerance is controlled within ±0.02mm.

6. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 2, characterized in that, When the axial dimension tolerance of the multi-layer stepped honeycomb workpiece is required to be ±0.10mm~±0.15mm, the height step difference dimension tolerance of the middle layer of the multi-step formed electrode grinding wheel is controlled within ±0.02mm, and the height step difference dimension tolerance of the first layer and the last layer is controlled within ±0.05mm.

7. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 1, characterized in that, The synchronous electrical discharge machining includes: Call the roughing electrical parameter set to perform a synchronous rough grinding on the multi-layer stepped honeycomb workpiece; The precision machining electrical parameter set is invoked to perform a synchronous precision grinding on the multi-layer stepped honeycomb workpiece.

8. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 1, characterized in that, The multi-step forming electrode grinding wheel is mounted on the spindle of the EDM machine. After installation, the radial runout accuracy of the multi-step forming electrode grinding wheel and the perpendicularity of the EDM machine spindle to the worktable need to be calibrated.

9. The method for processing multi-layer stepped honeycomb workpieces for aero-engines according to claim 1, characterized in that, The requirements for clamping and positioning the workpiece to be processed are as follows: before clamping the workpiece, the fixture must be aligned to ensure the runout of the fixture positioning surface and the concentricity of the fixture and the rotation center of the EDM table.

10. A multi-step forming electrode grinding wheel for implementing the processing method according to any one of claims 1-9, characterized in that, The multi-step forming electrode grinding wheel has multiple coaxial steps on its body that match the multi-layer stepped honeycomb workpiece structure to be processed. The radial and height dimensions of the multiple coaxial steps are determined according to the design grinding allowance of each layer of the honeycomb workpiece.

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