A small deformation low vibration rough milling method of a multi-stage impeller blade profile

Abstract

A method for low-deformation, low-vibration rough milling of multi-stage impeller blade profiles is disclosed. This method ensures the clamping rigidity of the multi-stage impellers through machining allowance allocation. Based on the characteristics of the blade cavity structure and the cutting infeed direction, different low-vibration unidirectional layer milling tool trajectory strategies are selected to control the range of tool tilt angle variation. During blade cavity rough milling, a depth calculation mode based on the flow channel surface is adopted. The machining sequence of the multi-stage impellers is arranged according to the principle of enhancing machining rigidity and reducing machining deformation. The method includes the following steps: reserving allowances at the connection positions of each stage flange and drum based on the structural characteristics of the part; designing a low-vibration unidirectional layer milling strategy according to the characteristics of the blade cavity structure; calculating the rough milling tool trajectory of the blade cavity using a flow channel-based depth model; determining the rough milling sequence of each stage impeller blade cavity; and verifying the low-deformation, low-vibration multi-stage impeller blade profile rough milling scheme. The advantages of this invention are: enhanced machining rigidity of the multi-stage impellers, improved machining process stability, and guaranteed efficiency in multi-stage impeller blade profile rough milling.

Description

Technical Field

[0001] This invention relates to the field of integral impeller machining technology for aero-engines, and in particular to a rough milling method for multi-stage impeller blade profiles with small deformation and low vibration. Background Technology

[0002] Integral multistage impellers are a gradually adopted rotor structure that effectively improves pressure ratio and aerodynamic efficiency. Integral multistage impellers do not use bolted connections and are manufactured using two methods. The first method involves machining a single forging. The second method involves welding multiple impeller blanks together before machining the blade profile. These two methods effectively reduce machining deviations caused by welding deformation, ensuring dimensional and positional accuracy of the blade profile. However, integral multistage impellers have a complex structure, narrow disk cavity space, insufficient space for tool shaft movement during blade machining, limited tool avoidance space, and the large amount of material removed and poor machining rigidity due to machining the blade profile from the blank state. The machining quality of integral multistage impeller blades carries a high risk; if a single blade has a machining problem, the entire multistage impeller may become unusable.

[0003] In rough milling of multi-stage impeller blade cavities, a parametric depth mode is generally used. The cutting path and tool movement path employ the same tool axis vector control strategy. To avoid interference, the tool axis oscillation amplitude is relatively large in the lower part of the cavity, which easily generates cutting chatter and poses a risk of overcutting due to vibration. To reduce cutting vibration and control machining deformation, existing machining schemes for integral multi-stage impellers typically employ relatively conservative cutting parameters. Integral multi-stage impellers have a long leading edge and short trailing edge. When using a parametric depth mode for rough milling of the blade cavity, the leading and trailing edge regions of the blade profile have the same number of rough milling toolpaths, allowing for improved machining efficiency. The allocation of machining allowance and the arrangement of machining sequence significantly affect the machining rigidity of integral multi-stage impellers, requiring the avoidance of cutting vibration caused by unreasonable machining sequence and allowance allocation. Summary of the Invention

[0004] The purpose of this invention is to improve the machining stability of rough milling of integral multi-stage impeller blade profiles, reduce cutting vibration, minimize machining deformation, avoid over-cutting of the blade profile due to rough milling vibration, and ensure machining efficiency. Specifically, this invention provides a low-deformation, low-vibration rough milling method for integral multi-stage impeller blade profiles. The objective of this invention is to improve the machining stability of rough milling of integral multi-stage impeller blade profiles, reduce cutting vibration, minimize machining deformation, avoid over-cutting of the blade profile due to rough milling vibration, and ensure machining efficiency.

[0005] The technical solution of this invention is to design a rough milling scheme that can reduce cutting vibration and machining deformation based on the vibration characteristics of rough milling of multi-stage impeller blade profiles and the cutting performance of the tools used, thereby enhancing the stability of the machining process and ensuring the efficiency of rough milling of multi-stage impeller blade profiles.

[0006] This invention provides a method for rough milling multi-stage impeller blades with small deformation and low vibration. Specifically, this method addresses the machining of multi-stage impeller blades by ensuring the rigidity of the multi-stage impeller clamping through machining allowance allocation. Based on the characteristics of the blade cavity structure and the cutting infeed direction, different low-vibration unidirectional layer milling tool trajectory strategies are selected to control the range of tool tilt angle variation. During blade cavity rough milling, a depth calculation mode based on the flow channel surface is adopted. By reducing the total cutting distance, machining efficiency can be improved to a certain extent. The machining sequence of the multi-stage impellers is arranged according to the principle of enhancing machining rigidity and reducing machining deformation, effectively releasing the internal stress of the part and ensuring that the part deformation is small and uniform.

[0007] Includes the following steps:

[0008] Step 1: Based on the structural characteristics of the parts, allowances should be reserved at the connection positions of each level of flange and drum;

[0009] Based on the structural dimensions, material hardness, and axial height of the parts, a certain margin is reserved relative to the final dimensions of the multi-stage impeller at the impeller flange 1 and the impeller drum connection position 2 at each stage to ensure the rigidity of the process system during blade milling of the multi-stage impeller.

[0010] Step 2: Develop a multi-stage impeller clamping and positioning scheme based on the part's reference position;

[0011] Select the clamping and positioning position on the impeller of the stage to which the radial reference surface 3 and the axial reference surface 4 belong. Select the inner circular surface 5 of the wheel disk that is coaxial with the radial reference surface 3 as the clamping radial positioning reference. Select the rim plate plane 6 that is parallel to the axial reference surface 4 as the clamping axial positioning reference. Determine the impeller rim plate plane 8 that is farthest from the axial reference surface 4 as the pressing position.

[0012] Step 3: Design a low-vibration unidirectional layer milling strategy based on the characteristics of the blade cavity structure;

[0013] Each stage of the impeller is formed by blade shape 7 and flow channel 9 to rough mill the blade cavity 11. Combining the structural characteristics of the blade cavity 11 and the tilt angle of the flow channel 9 relative to the rotation center 10 of the multi-stage impeller, low vibration unidirectional layer milling strategies 12, 13, 14 and 15 are designed. In low vibration unidirectional layer milling strategies 12 and 14, each tool path first cuts and then moves the tool. In low vibration unidirectional layer milling strategies 13 and 15, each tool path first moves the tool and then cuts. Unidirectional layer milling strategies 14 and 15 have additional tool paths with safety margin. The first cutting trajectory 16 avoids the blade side to prevent the tool from generating an excessive contact area during cutting and to ensure stable cutting.

[0014] Each complete toolpath of the unidirectional layer milling strategies 12, 13, 14, and 15 includes a cutting path and a tool movement path. The tool axis vector of the cutting path adopts the tool tilt angle control mode, and the tool axis vector of the tool movement path adopts the smooth and interference-free control mode.

[0015] Step 4: Calculate the rough milling tool path for the blade cavity according to the flow channel-based depth mode;

[0016] For the blade cavity 11 of each impeller, ball end mills and feed direction are selected according to the machining requirements. The blade cavity 11 is divided into n segments for machining. In the i-th segment, a cutting strategy i = 1, 2...n is selected from the low vibration unidirectional layer milling strategies 12, 13, 14, and 15. The flow channel-based depth mode 17 is used to calculate and generate the rough milling tool path for the i-th segment. In the cutting path, the tool vector is smooth and interference-free, so that the tool rake angle is always positive or always negative, and the absolute value of the tool rake angle varies in the range of 2° to 30°. In the tool movement path, the tool axis vector is smooth and interference-free, and the feed rate of the tool movement path is selected in the range of 2 to 15 times the feed rate of the cutting path.

[0017] Step 5: Determine the rough milling sequence for the cavities of each impeller blade;

[0018] Step 5.1: Based on the method of enhancing machining rigidity and reducing machining deformation, the rough milling sequence of each stage of impeller blade cavity 11 is in the order from farthest to near the axial reference plane 4 of the part;

[0019] Step 5.2: Following a symmetrical machining approach, determine the machining sequence for rough milling the blade cavities 11 of each impeller stage. Considering the weight of material removed from each group of blades, for impellers where the workpiece material is easily deformable, divide all areas to be rough milled into approximately equal parts, starting from the zero-degree angle towards the position. p Group p≥2, according to 1, 2 p / 2+1,2 p / 4+1,2 pFor impellers whose workpiece material is not easily deformable, starting from the zero-degree angle towards the position, all areas to be rough milled are approximately divided into even numbers qq≥2, and processed in the order of 1, q / 2+1, 2, q / 2+2...

[0020] Step 6: Verify the rough milling scheme for multi-stage impeller blade profiles with small deformation and low vibration;

[0021] For multi-stage impellers, the blade profiles of each stage are machined according to the established machining sequence, using the calculated rough milling tool path to verify the smoothness of the blade machining process and the compliance of the machining quality. If there is significant machining deformation and cutting vibration during the machining process, the cutting strategy and tool axis vector can be adjusted appropriately according to steps 1 to 5, and the machining verification can be performed again.

[0022] Compared with the prior art, the advantages of this invention are:

[0023] The present invention provides a method for rough milling multi-stage impeller blade profiles with small deformation and low vibration, which can reduce cutting vibration and machining deformation, enhance the machining rigidity of multi-stage impellers, improve the stability of the machining process, and ensure the rough milling efficiency of multi-stage impeller blade profiles. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0025] Figure 1 A two-dimensional schematic diagram of a multi-stage impeller (three stages).

[0026] Figure 2 Two-dimensional schematic diagram of the leaf-shaped part

[0027] Figure 3 A schematic diagram of low-vibration unidirectional layer milling without safety margin (cutting first, then tool retraction).

[0028] Figure 4 A schematic diagram of low-vibration unidirectional layer milling without safety margin (tool repositioning before cutting).

[0029] Figure 5 A schematic diagram of low-vibration unidirectional layer milling with a safety margin (cutting first, then tool retraction).

[0030] Figure 6 A schematic diagram of low-vibration unidirectional layer milling with a safety margin (tool repositioning before cutting).

[0031] Figure 7 Toolpath in depth mode based on flow channel

[0032] In the figure, 1-edge plate, 2-impeller drum connection position, 3-radial reference plane, 4-axial reference plane, 5-inner circular surface of edge plate, 6-edge plate plane, 7-blade shape, 8-impeller edge plate plane farthest from the axial reference plane, 9-flow channel, 10-rotation center of multi-stage impeller, 11-rough milling of blade cavity, 12-low vibration unidirectional layer milling strategy without safety margin (cut first, then move tool), 13-low vibration unidirectional layer milling strategy without safety margin (move tool first, then cut), 14-low vibration unidirectional layer milling strategy with safety margin (cut first, then move tool), 15-low vibration unidirectional layer milling strategy with safety margin (move tool first, then cut), 16-first cutting trajectory, 17-depth mode based on flow channel. Detailed Implementation

[0033] The present invention will be further explained below with reference to specific implementation schemes, but it is not limited to the present invention. Any modification of the structure, change of the proportion or adjustment of the size, without affecting the effect and purpose that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0034] This invention provides a method for rough milling a multi-stage impeller with small deformation and low vibration. The multi-stage impeller has three stages, with narrow blade spacing and high dimensional accuracy requirements. The flow channel has a large tilt angle relative to the rotation center of the multi-stage impeller, making the workpiece material prone to deformation. The specific operation steps are as follows:

[0035] Step 1: Based on the structural characteristics of the parts, allowances should be reserved at the connection positions of each level of flange and drum;

[0036] Based on the structural dimensions, material hardness, and axial height of the parts, a certain margin is reserved relative to the final dimensions of the multi-stage impeller at the impeller flange 1 and the impeller drum connection position 2 at each stage to ensure the rigidity of the process system during blade milling of the multi-stage impeller.

[0037] Step 2: Develop a multi-stage impeller clamping and positioning scheme based on the part's reference position;

[0038] Select the clamping and positioning position on the impeller of the stage to which the radial reference surface 3 and the axial reference surface 4 belong. Select the inner circular surface 5 of the wheel disk that is coaxial with the radial reference surface 3 as the clamping radial positioning reference. Select the rim plate plane 6 that is parallel to the axial reference surface 4 as the clamping axial positioning reference. Determine the impeller rim plate plane 8 that is farthest from the axial reference surface 4 as the pressing position.

[0039] Step 3: Design a low-vibration unidirectional layer milling strategy based on the characteristics of the blade cavity structure;

[0040] Each stage of the impeller is formed by blade shape 7 and flow channel 9 to rough mill the blade cavity 11. Combining the structural characteristics of the blade cavity 11 and the tilt angle of the flow channel 9 relative to the rotation center 10 of the multi-stage impeller, low vibration unidirectional layer milling strategies 12, 13, 14 and 15 are designed. In low vibration unidirectional layer milling strategies 12 and 14, each tool path first cuts and then moves the tool. In low vibration unidirectional layer milling strategies 13 and 15, each tool path first moves the tool and then cuts. Unidirectional layer milling strategies 14 and 15 have additional tool paths with safety margin. The first cutting trajectory 16 avoids the blade side to prevent the tool from generating an excessive contact area during cutting and to ensure stable cutting.

[0041] Each complete toolpath of the unidirectional layer milling strategies 12, 13, 14, and 15 includes a cutting path and a tool movement path. The tool axis vector of the cutting path adopts the tool tilt angle control mode, and the tool axis vector of the tool movement path adopts the smooth and interference-free control mode.

[0042] Step 4: Calculate the rough milling tool path for the blade cavity according to the flow channel-based depth mode;

[0043] For the blade cavities 11 of each impeller stage, a Φ6 ball end mill is selected according to the machining requirements. The cutter enters from the air intake side of each impeller stage, dividing the blade cavity 11 into two sections for machining. In the first section, a low-vibration unidirectional layer milling strategy 12 is selected, and in the second section, a unidirectional layer milling strategy 14 is selected. The unidirectional layer milling strategy 14 has an additional toolpath with a safety margin of 0.5mm to prevent overcutting of the part due to cutting vibration. The flow channel-based depth mode 17 is used to calculate and generate the rough milling toolpaths for the first and second sections. In the cutting path, the tool vector is smooth and interference-free, so that the tool pitch angle is always kept positive, and the absolute value of the tool pitch angle varies within the range of 2° to 24°. In the moving tool path, the tool axis vector is smooth and interference-free. The feed rate of the moving tool path is selected as 6 times the feed rate of the cutting path.

[0044] Step 5: Determine the rough milling sequence for the cavities of each impeller blade;

[0045] Step 5.1: Based on the method of enhancing machining rigidity and reducing machining deformation, the rough milling sequence of each stage of impeller blade cavity 11 is in the order from farthest to near the axial reference plane 4 of the part;

[0046] Step 5.2: Based on the symmetrical machining method, formulate the machining sequence for rough milling the blade cavity 11 of each impeller stage. Combined with the weight of material removed from each group of blades, for impellers whose workpiece material is easily deformable, start from the zero-degree angle and divide all areas to be rough milled into approximately 2p groups (p≥2), and perform machining in the order of 1, 5, 3, 7...

[0047] Step 6: Verify the rough milling scheme for multi-stage impeller blade profiles with small deformation and low vibration;

[0048] For multi-stage impellers, the blade profiles of each stage were machined according to the established machining sequence, using the calculated rough milling tool path. The smoothness of the blade profile machining process and the conformity of the machining quality were verified. The machining results showed that the multi-stage impeller blade profile milling process was smooth, with minimal cutting vibration and machining deformation.

[0049] Matters not covered in this invention are common knowledge.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for rough milling of multi-stage impeller blades with small deformation and low vibration, characterized in that: Includes the following steps: Step 1: Based on the structural characteristics of the parts, allowances are reserved at the connection positions of the impeller rim plates and drum at each stage; Based on the part's structural dimensions, material hardness, and axial height, a certain margin is reserved relative to the final dimensions of the multi-stage impeller at the impeller flange plate (1) and the impeller drum connection position (2) at each stage to ensure the rigidity of the process system during blade milling of the multi-stage impeller; Step 2: Develop a multi-stage impeller clamping and positioning scheme based on the part's reference position; Select the clamping and positioning position on the impeller of the stage to which the radial reference surface (3) and axial reference surface (4) of the multi-stage impeller belong. Select the inner circular surface (5) of the wheel disk that is coaxial with the radial reference surface (3) as the clamping radial positioning reference. Select the rim plate plane (6) that is parallel to the axial reference surface (4) as the clamping axial positioning reference. Determine the impeller rim plate plane (8) that is farthest from the axial reference surface (4) as the clamping position. Step 3: Design a low-vibration unidirectional layer milling strategy based on the characteristics of the blade cavity structure; Each impeller stage consists of blade profile (7) and flow channel (9) to form a rough milling blade cavity (11). Combining the structural characteristics of the blade cavity (11) and the tilt angle of the flow channel (9) relative to the rotation center (10) of the multi-stage impeller, low vibration unidirectional layer milling strategies one, two, three and four are designed. In low vibration unidirectional layer milling strategies one and three, each tool path first cuts and then moves the tool. In low vibration unidirectional layer milling strategies two and four, each tool path first moves the tool and then cuts. Low vibration unidirectional layer milling strategies three and four have additional tool paths with safety margin. The first cutting trajectory (16) in each low vibration unidirectional layer milling strategy avoids the blade side to prevent the tool from generating too large a contact area during cutting and to ensure stable cutting. Each complete toolpath of the low-vibration unidirectional layer milling strategy one, two, three, and four includes a cutting path and a tool movement path. The tool axis vector of the cutting path adopts the tool tilt angle control mode, and the tool axis vector of the tool movement path adopts the smooth and interference-free control mode. Step 4: Calculate the rough milling tool path for the blade cavity according to the flow channel-based depth mode; For the blade cavity (11) of each impeller, ball end mill and feed direction are selected according to the machining requirements. The blade cavity (11) is divided into n segments for machining. In the i-th segment, a cutting strategy is selected from the low vibration unidirectional layer milling strategies one, two, three, and four, i = 1, 2, ... n. The flow channel-based depth mode (17) is adopted to calculate and generate the rough milling tool path of the i-th segment. In the cutting path, the tool vector is smooth and there is no interference, so that the tool pitch angle is always positive or always negative, and the absolute value of the tool pitch angle varies in the range of 2° to 30°. In the tool movement path, the tool axis vector is smooth and there is no interference. The feed speed of the tool movement path is selected in the range of 2 to 15 times the feed speed of the cutting path. Step 5: Determine the rough milling sequence for the cavities of each impeller blade; Step 5.1: Based on the method of enhancing machining rigidity and reducing machining deformation, the rough milling sequence of each stage of impeller blade cavity (11) is in the order from farthest to near the axial reference surface (4) of the part; Step 5.2: Based on the symmetrical machining method, determine the machining sequence for rough milling the blade cavity (11) of each impeller stage. Combined with the weight of material removal for each group of blades, for impellers where the workpiece material is easily deformable, start from the zero-degree angle and divide all areas to be rough milled into approximately equal parts. p Group, p≥2, according to 1, 2 p / 2+1,2 p / 4+1,2 p The machining is carried out in the order of ×3 / 4+1……. For impellers whose workpiece material is not easily deformed, starting from the zero-degree angle, all areas to be rough milled are approximately divided into even numbers q, q≥2, and the machining is carried out in the order of 1, q / 2+1, 2, q / 2+2……. Step 6: Verify the rough milling scheme for multi-stage impeller blade profiles with small deformation and low vibration; For multi-stage impellers, the blade profiles of each stage are machined according to the established machining sequence, using the calculated rough milling tool path to verify the smoothness of the blade machining process and the compliance of the machining quality. If there is significant machining deformation and cutting vibration during the machining process, the cutting strategy and tool axis vector can be adjusted appropriately according to steps 1 to 5, and the machining verification can be performed again.

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