Blade and blade root fillet milling method

Abstract

The application discloses a blade and a blade root fillet milling method, which generates tangent fillet circle center lines and tangent cutting fillet circle center lines in a graphic processing mode, and performs tangent connection, so that the continuity of the fillet is realized by taking the circle center line as a driving line. The method can complete the processing of the blade transition fillet at one time, does not perform secondary processing of the tangent cutting fillet, reduces the processing time, makes the processing surface a whole surface without tool marks, and improves the processing quality of the fillet surface.

Description

Technical Field

[0001] This invention belongs to the field of blade processing technology and relates to a method for milling blades and the rounded corners at the blade root. Background Technology

[0002] The blade profile and the ferrule are connected by a structural circle. The ferrule surface area is relatively small compared to the blade profile. In open areas, the transition fillet between the ferrule and the blade profile is tangent to both the blade profile and the ferrule surface simultaneously. In narrow areas, due to the smaller ferrule area, the fillet can only be tangent to the blade profile and intersecting the edge of the ferrule. In this case, a mixture of tangent and intersecting fillets appears at the junction of the ferrule and the blade profile.

[0003] Currently, two methods are used to process fillets in CNC machining. One method uses a built-in fillet machining module in the software for automatic programming and milling. This method is simple and fast. However, due to the complex and diverse blade structure, the automatic programming module has poor adaptability, and the milling trajectory often exhibits defects such as folding and abrupt changes in direction, resulting in material accumulation or overcutting at the fillet surface. In the automatic programming machining process, to ensure the continuity and smoothness of the machining trajectory, mixed fillets are processed into tangential fillets. Intersecting fillets are finally machined separately. The other method is manual preprocessing, which involves tangentially extending and expanding a narrow area of ​​the flange surface, offsetting the flange surface and the blade profile according to the fillet radius value, and using the intersection line of the two surfaces as the center line. This line drives the tool movement to achieve contour milling of the fillet. This method can eliminate defects such as folding and abrupt changes in direction in the machining trajectory, but it ignores the machining of intersecting fillets. After machining, the intersecting fillet area shows a bulge or incomplete machining, requiring special methods to detect the bulge value and manual compensation in the software to complete the machining of the intersecting fillet, resulting in low machining efficiency.

[0004] Currently, both processing methods require secondary machining of the intersecting rounded corner surfaces. During the secondary machining, the machine tool positioning error caused by the secondary positioning is difficult to eliminate, resulting in bulges and dents on the rounded corner surfaces, which directly affects the quality of the rounded corner machining. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing machining methods require secondary machining of intersecting rounded corners. During this secondary machining, machine tool positioning errors caused by the secondary positioning are difficult to eliminate, resulting in protrusions and dents on the rounded corners, directly affecting the quality of the rounded corner machining. This invention provides a method for milling rounded corners of blades and blade roots. It utilizes graphic processing to find the center lines of intersecting and tangent rounded corners and connects them tangentially. Using the center lines as driving lines, continuous machining of the rounded corners is achieved.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for milling the root radius of a blade includes the following steps:

[0008] Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet;

[0009] Generate the center line of the secant fillet: Select any point on the secant line of the edge plate surface, draw a circle with the point as the center in the vertical plane of the tangent vector at that point, sweep the resulting circle along the secant line of the edge plate surface to form a swept surface, and set the intersection line of the swept surface and the blade offset surface as the center line of the secant fillet.

[0010] A complete center line is constructed based on the center lines of tangent and secant fillets. A tool milling trajectory is generated based on the complete center line, and the fillet at the root of the blade is machined according to the tool milling trajectory.

[0011] A further improvement of the present invention is that:

[0012] The process of generating the center line of the tangent fillet includes the following steps:

[0013] When offsetting the blade profile and rim plate surface towards the center of the rounded corner, the offset distance is the radius of the machining tool.

[0014] The process of generating the center line of the intersecting fillet includes the following steps:

[0015] When drawing a circle with that point as the center in the plane perpendicular to the tangent vector, the radius of the circle is the radius of the machining tool.

[0016] The construction of a complete circle centerline based on the centerlines of tangent and secant fillets includes:

[0017] The center lines of the intersecting rounded corners are cut using the center lines of the tangent rounded corners as the boundary. The cut center lines of the intersecting rounded corners are then connected tangentially to the center lines of the tangent rounded corners to form a complete center line.

[0018] It also includes homogenizing the complete circle center line to obtain a homogenized circle center line, and generating the tool milling trajectory based on the homogenized circle center line.

[0019] The process of homogenizing the complete circle centerline includes:

[0020] Points are sampled at equal intervals along the complete circle center line to generate a point set. Cubic splines are generated based on the point set, and a homogenized circle center line is generated based on the cubic splines.

[0021] Sampling was performed at a distance of 0.1 mm.

[0022] A method for milling the root radius of a blade includes the following steps:

[0023] Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet;

[0024] Generate the center line of the secant fillet: Using the secant line of the flange surface as the central axis of the pipe, select the outer diameter of the pipe, construct the outer surface of the pipe, and set the intersection line of the outer surface of the pipe and the offset surface of the blade as the center line of the secant fillet.

[0025] A complete center line is constructed based on the center lines of tangent and secant fillets. A tool milling trajectory is generated based on the complete center line, and the fillet at the root of the blade is machined according to the tool milling trajectory.

[0026] When constructing the outer surface of the pipe, the diameter of the cutting tool is used as the pipe diameter.

[0027] A blade, wherein the root radius of the blade is machined using the milling method described in any one of the present invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention discloses a method for milling the root rounded corners of blades. It generates tangent and secant rounded corner center lines through graphic processing and connects them tangentially. Using the center lines as driving lines, continuous machining of the rounded corners is achieved. This method can complete the machining of the blade transition rounded corners in one step, eliminating the need for secondary machining of secant rounded corners, reducing machining time, and resulting in a seamless machined surface without tool marks, thus improving the machining quality of the rounded corner surface. Attached Figure Description

[0030] 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.

[0031] Figure 1 This is a schematic diagram of the mixed fillet radius of the blade of the present invention.

[0032] Wherein: 1-Intersecting fillet; 2-Tangent fillet; 3-Center line. Detailed Implementation

[0033] 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 embodiments of the present invention, and not all embodiments. 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.

[0034] Therefore, the following detailed description of the embodiments of the 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 invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present 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, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings:

[0040] See Figure 1 This invention discloses a method for milling the root fillet of a blade. This method is used for CNC milling of continuous mixed fillets (tangential and secant) at the junction of the blade profile and the ferrule, where a mathematical model exists. The method utilizes graphic processing to find the center lines of the secant and tangential fillets and connects them tangentially. The center lines are used as driving lines to achieve continuous fillet machining. No secondary machining of the secant fillets is performed. The purpose of this method is achieved through the following steps:

[0041] Example 1

[0042] This invention discloses a method for milling the root radius of a blade, comprising the following steps:

[0043] Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet;

[0044] Generate the center line of the secant fillet: Select any point on the secant line of the edge plate surface, draw a circle with the point as the center in the vertical plane of the tangent vector at that point, sweep the resulting circle along the secant line of the edge plate surface to form a swept surface, and set the intersection line of the swept surface and the blade offset surface as the center line of the secant fillet.

[0045] A complete center line is constructed based on the center lines of tangent and secant fillets. A tool milling trajectory is generated based on the complete center line, and the fillet at the root of the blade is machined according to the tool milling trajectory.

[0046] Example 2

[0047] This invention discloses a method for milling the root radius of a blade, comprising the following steps:

[0048] Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet;

[0049] Generate the center line of the secant fillet: Select any point on the secant line of the edge plate surface, draw a circle with the point as the center in the vertical plane of the tangent vector at that point, sweep the resulting circle along the secant line of the edge plate surface to form a swept surface, and set the intersection line of the swept surface and the blade offset surface as the center line of the secant fillet.

[0050] A complete center line is constructed based on the center lines of tangent and secant fillets. A tool milling trajectory is generated based on the complete center line, and the fillet at the root of the blade is machined according to the tool milling trajectory.

[0051] Furthermore, in this embodiment, when the blade profile and the edge plate are offset towards the center of the rounded corner, the offset distance is the radius of the machining tool.

[0052] Furthermore, in this embodiment, when drawing a circle, the radius of the circle is the radius of the machining tool.

[0053] Example 3

[0054] This invention discloses a method for milling the root radius of a blade, comprising the following steps:

[0055] Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet;

[0056] Generate the center line of the secant fillet: Select any point on the secant line of the edge plate surface, draw a circle with the point as the center in the vertical plane of the tangent vector at that point, sweep the resulting circle along the secant line of the edge plate surface to form a swept surface, and set the intersection line of the swept surface and the blade offset surface as the center line of the secant fillet.

[0057] A complete center line is constructed based on the center lines of tangent and secant fillets. A tool milling trajectory is generated based on the complete center line, and the fillet at the root of the blade is machined according to the tool milling trajectory.

[0058] Furthermore, in this embodiment, constructing a complete center line based on the center lines of tangent and secant fillets includes:

[0059] The center lines of the intersecting rounded corners are cut using the center lines of the tangent rounded corners as the boundary. The cut center lines of the intersecting rounded corners are then connected tangentially to the center lines of the tangent rounded corners to form a complete center line.

[0060] Furthermore, in this embodiment, the process also includes homogenizing the complete center line to obtain a homogenized center line, and generating a milling trajectory based on the homogenized center line.

[0061] Furthermore, in this embodiment, the complete center line is homogenized, including:

[0062] Points are sampled at equal intervals along the complete circle center line to generate a point set. A cubic spline is generated based on the point set, and a homogenized circle center line is generated based on the cubic spline. Specifically, sampling is performed at intervals of 0.1 mm.

[0063] Example 4

[0064] A method for milling the root radius of a blade, characterized by comprising the following steps:

[0065] Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet;

[0066] Generate the center line of the secant fillet: Using the secant line of the flange surface as the central axis of the pipe, select the outer diameter of the pipe, construct the outer surface of the pipe, and set the intersection line of the outer surface of the pipe and the offset surface of the blade as the center line of the secant fillet.

[0067] A complete center line is constructed based on the center lines of tangent and secant fillets. A tool milling trajectory is generated based on the complete center line, and the fillet at the root of the blade is machined according to the tool milling trajectory.

[0068] Furthermore, in this embodiment, when constructing the outer surface of the pipe, the diameter of the cutting tool is used as the diameter of the pipe.

[0069] Example 5

[0070] Step 1, determine the center line of the tangent fillet: the distance between the offset blade surface and the machining tool radius of the blade plate surface, the approximate direction of the offset towards the center line of the fillet, forming the offset surface of the blade surface and the offset surface of the blade plate surface, and determine the intersection line of the offset surface of the blade surface and the offset surface of the blade plate surface. This intersection line is the center line of the tangent fillet.

[0071] Step 2, Determine the center line of the secant fillet: This embodiment discloses two methods for obtaining the center line of the secant fillet:

[0072] The first method is to draw a full circle with a tool radius equal to the radius of the circle on the perpendicular plane of the cutting vector at any point on the cleaving line of the flange, with the center of the circle being the point on the cleaving line. Sweep the circle along the cleaving line to form a swept surface. The intersection line of the swept surface and the offset surface of the blade profile in step 1 is determined as the center line of the cleaving fillet.

[0073] The second method is as follows: using the cleaving line of the flange as the center line of the pipe and the diameter of the cutting tool as the diameter of the pipe, the outer surface of the pipe is formed. The intersection line of the outer surface of the pipe and the offset surface of the blade profile in step 1 forms the center line of the secant fillet.

[0074] Step 3, Continuous circle center line generation: Using the tangent circle center line generated in Step 1 as the boundary, trim the intersecting circle center line in Step 2 to remove redundant segments, and connect the trimmed intersecting circle center line tangentially with the tangent circle center line generated in Step 1 to form a complete circle center line.

[0075] Step 4, Homogenization of the center line: Sample points along the entire center line at 0.1 mm intervals to generate a point set. Use this point set to generate a cubic spline and generate the homogenized center line.

[0076] Step 5, Machining Mixed Fillets: Place the tool tip on the drive line, select a suitable tool axis direction, and move it along the tool axis by one tool ball radius value to form a tool position point, generate the tool path, and process it into code executable by the CNC machine tool to machine the part on the machine tool.

[0077] This embodiment also discloses a blade having intersecting fillet 1 and tangent fillet 2. The blade generates a center line 3 by the milling method disclosed in any embodiment of the present invention, and then the fillet at the root of the blade is machined.

[0078] The method disclosed in this embodiment finds the center line of the mixed fillet and homogenizes it to generate a smooth and homogenized CNC tool path. The machining of the blade transition fillet is completed in one go without secondary machining, which reduces the machining time and makes the machined surface a whole surface without tool joint marks, thus improving the machining quality of the fillet surface.

[0079] This embodiment uses a certain blade as an example:

[0080] The blade transition fillet is R5, and the blade has a cleaving fillet on the exhaust side. Previously, this area was machined separately using fixed-axis machining. Due to the secondary positioning, this was not only time-consuming but also resulted in machining joints and poor fillet quality. Now, a mathematical model-based method for machining mixed fillets on blades is used to machine the transition fillet. The steps are as follows:

[0081] Step 1: Offset the blade profile and shroud surface by 5 mm each, with the offset direction roughly pointing towards the center line. The intersection of the two offset surfaces is the tangent center line;

[0082] Step 2: Since the intersection of the exhaust edge and the exhaust edge is approximately a straight line, it is relatively simple. Use the pipe command to quickly generate a pipe with an outer diameter of 10 mm. The pipe surface and the blade profile offset surface will intersect.

[0083] Step 3: Trim the redundant parts of the intersection line generated in Step 2 with the center line of the circle in Step 1 as the boundary, and use tangential connection at the endpoints of the two line segments to form the overall center line;

[0084] Step 4: Sample points along the entire center line at 0.1 mm intervals to generate a point set. Use this point set to generate a cubic spline and then generate the homogenized center line.

[0085] Step 5: Place the tool tip on the drive line, select the tool axis direction to be 70 degrees relative to the blade centroidal axis, project the tool onto the blade surface along the tool axis direction to generate the tool path, convert it into code that can be executed by the CNC machine tool, and process the part on the machine tool.

[0086] The transition fillet processed by the method disclosed in this embodiment has no tooling required, has high surface quality, requires no secondary processing, saves processing time, and improves processing efficiency.

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for milling the root radius of a blade, characterized in that, Includes the following steps: Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet; Generate the center line of the secant fillet: Select any point on the secant line of the edge plate surface, draw a circle with the point as the center in the vertical plane of the tangent vector at that point, sweep the resulting circle along the secant line of the edge plate surface to form a swept surface, and set the intersection line of the swept surface and the blade offset surface as the center line of the secant fillet. A complete circle center line is constructed based on the center lines of the tangent and secant fillets. A tool milling trajectory is generated based on the complete circle center line. The fillet at the root of the blade is then machined according to the tool milling trajectory. The process of generating the center line of the tangent fillet includes the following steps: When offsetting the blade profile and rim plate surface towards the center of the rounded corner, the offset distance is the radius of the machining tool; The process of generating the center line of the intersecting fillet includes the following steps: When drawing a circle with that point as the center in the plane perpendicular to the tangent vector, the radius of the circle is the radius of the machining tool.

2. The method for milling the root radius of a blade according to claim 1, characterized in that, The construction of a complete circle centerline based on the centerlines of tangent and secant fillets includes: The center lines of the intersecting rounded corners are cut using the center lines of the tangent rounded corners as the boundary. The cut center lines of the intersecting rounded corners are then connected tangentially to the center lines of the tangent rounded corners to form a complete center line.

3. The method for milling the root radius of a blade according to claim 2, characterized in that, It also includes homogenizing the complete circle center line to obtain a homogenized circle center line, and generating the tool milling trajectory based on the homogenized circle center line.

4. The method for milling the root radius of a blade according to claim 3, characterized in that, The homogenization process for the complete circle's center line includes: Points are sampled at equal intervals along the complete circle center line to generate a point set. Cubic splines are generated based on the point set, and a homogenized circle center line is generated based on the cubic splines.

5. The method for milling the root radius of a blade according to claim 4, characterized in that, Sampling was performed at a distance of 0.1 mm.

6. A method for milling the root radius of a blade, characterized in that, Includes the following steps: Generate the center line of the tangent fillet: Offset the blade profile and the edge plate surface towards the center of the fillet, obtain the blade offset surface and the edge plate offset surface, and set the intersection of the blade offset surface and the edge plate offset surface as the center line of the tangent fillet; Generate the center line of the secant fillet: Using the secant line of the flange surface as the central axis of the pipe, select the outer diameter of the pipe, construct the outer surface of the pipe, and set the intersection line of the outer surface of the pipe and the offset surface of the blade as the center line of the secant fillet. A complete circle center line is constructed based on the center lines of the tangent and secant fillets. A tool milling trajectory is generated based on the complete circle center line. The fillet at the root of the blade is then machined according to the tool milling trajectory. When constructing the outer surface of the pipe, the diameter of the cutting tool is used as the diameter of the pipe. The process of generating the center line of the tangent fillet includes the following steps: When offsetting the blade profile and rim plate surface towards the center of the rounded corner, the offset distance is the radius of the machining tool.

7. A blade, characterized in that, The root radius of the blade is machined using the milling method according to any one of claims 1-6.

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