A method for milling internal splines in a blisk

Abstract

The present invention provides a milling method for the spline of an integral bladed disk, which uses a milling cutter to process the spline feature. An angle head is used to connect the milling cutter and the CNC machine tool to ensure that the milling cutter can reach the processing surface. No other additional processing equipment is required, which greatly reduces the processing cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aero-engine machining, in particular to a milling method for inner spline of blisk. BACKGROUND

[0002] Spline connection is one of the most commonly used connection methods. Spline connection is composed of inner spline and outer spline. Both inner spline and outer spline are multi-toothed parts. The spline on the inner cylindrical surface is inner spline, and the spline on the outer cylindrical surface is outer spline. Spline tooth structure is widely used in the field of engine transmission, such as blisk with spline and some rotating parts with spline. Spline structure is a standard structure, and different standards are usually selected according to the use area of the equipment. Manufacturers produce according to the standard size specified in the American standard, German standard or Chinese standard. Figure 1 As shown in Fig. 1, an inner spline structure 2 is arranged on the blisk 1. Figure 2 As shown in Fig. 2, the inner spline structure includes an inner cylindrical spline body 2-3 with an inner diameter d, spline teeth 2-1 and tooth roots 2-2. Figure 1 As shown in Fig. 3, the tooth roots 2-2 in this embodiment are flat tooth roots, and in some other structures, the tooth roots also include round tooth roots. Figure 3 In spline connection, the inner and outer splines transmit torque or motion based on the working tooth surfaces 2-4 on both sides of the spline teeth 2-1 during work.

[0003] Because the inner spline structure is the spline on the inner cylindrical surface, it is difficult for the milling cutter to reach the machining area due to its special structure. Therefore, in the prior art, spline structure machining mostly adopts gear shaping manufacturing process or gear grinding manufacturing process. However, both processes require the use of special machining equipment, and each machining needs to be specially developed and debugged, and non-standard cutters need to be customized according to the size of the parts, resulting in high cost of developing parts and long machining cycle. SUMMARY

[0004] In order to solve the problems of long machining cycle and high cost of spline in the prior art, the present application provides a milling method for inner spline of blisk, which reduces the manufacturing difficulty of spline, reduces the processing cost and shortens the manufacturing cycle.

[0005] The technical scheme of the present application is as follows: a milling method for inner spline of blisk, characterized in that it comprises the following steps:

[0006] S1: confirming the size and shape of the inner spline in the inner spline structure to be machined, and making a special machining cutter;

[0007] The special machining tool is a milling cutter, and the cutter tip is adapted to the size and shape of the spline groove;

[0008] S2: Select the angle head for machining;

[0009] The angle head includes: a mounting part and a machine tool spindle interface, wherein a milling cutter for machining is provided on the mounting part, and the machine tool spindle interface is connected to a CNC machine tool;

[0010] Confirm the inner diameter of the spline body in the internal spline structure, and select an angle head whose mounting part length is smaller than the inner diameter;

[0011] S3: Select a ball end mill with a diameter smaller than the width of the spline groove as the roughing tool;

[0012] S4: Based on a CNC machine tool, construct a groove machining program for the spline groove;

[0013] The groove machining process includes: a roughing process, a semi-finishing process, and a finishing process;

[0014] In the roughing process, based on the roughing tool, a cycloidal milling strategy is used to complete the roughing of the spline groove on the inner cylinder of the spline body.

[0015] In the semi-finishing process, based on the special machining tool, the center line of the spline bottom surface is selected, and the spline groove is machined using line drive based on the planar milling command. During the machining process, the spline groove sidewalls and bottom surface retain allowance.

[0016] In the finishing process, based on the special machining tool, the center line of the spline bottom surface is selected, and the spline groove is machined using line drive based on the planar milling command, without leaving any allowance during the machining process;

[0017] S5: Based on the groove machining program, for each spline groove in the internal spline structure to be machined, the machining is completed one by one in the order of roughing, semi-finishing and finishing to obtain the machined internal spline structure.

[0018] The roughing tool and the special machining tool are mounted on the CNC machine tool through the angle head. During the machining process, the roughing tool and the special machining tool are located on the line connecting the center point of the spline bottom surface and the center of the inner cylinder.

[0019] Its further features are:

[0020] In step S2, a spline groove measuring tool also needs to be made;

[0021] The spline groove measuring tool includes: a measuring head and a measuring rod, wherein the measuring head is disposed at the end of the measuring rod;

[0022] The dimensions of the measuring tool are adapted to the dimensions of the inner cylinder of the internal spline structure to be processed, and the shape of the measuring head is adapted to the inner cavity of the spline groove;

[0023] The measuring rod can be straight, Y-shaped, or star-shaped;

[0024] When the measuring rod is in the shape of a straight line, the measuring head is located at one or both ends of the measuring rod;

[0025] When the measuring rod is Y-shaped or star-shaped, each branch at its end is adapted to a spline groove, and the measuring head is disposed on each end of the attack body;

[0026] Step S5 specifically includes the following steps:

[0027] a1: Select any one of the spline slots in the spline body as the starting point of a measuring head branch of the spline slot measuring tool;

[0028] On the spline body, find the spline grooves corresponding to the positions of all measuring heads, and denote the unprocessed spline grooves as: grooves to be processed.

[0029] a2: The machining of the groove to be machined is completed in the order of roughing, semi-finishing and finishing;

[0030] a3: Using the spline groove measuring tool, place the measuring head in the processed spline groove, and pull it from one end to the other along the length of the spline body to complete the quality inspection of the spline groove;

[0031] a4: Repeat steps a1 to a4 until all the spline slots have been machined;

[0032] The CNC machine tool is a four-axis or five-axis CNC machine tool.

[0033] This invention provides a milling method for the internal splines of an integral bladed disk. It employs a milling cutter to machine the spline features, using an angle head to connect the milling cutter and the CNC machine tool, ensuring the milling cutter reaches the machined surface. No additional machining equipment is required, significantly reducing machining costs. Based on CNC machine tool machining, only one spline groove machining program needs to be designed. The machining of other spline grooves can be completed simply by adjusting the angle of the machining tool on the CNC machine tool, greatly reducing the difficulty of program development, shortening the overall workpiece machining cycle, reducing labor costs, and thus lowering the overall machining cost. Furthermore, roughing only requires a standard ball end mill, while semi-finishing and finishing programs use dedicated milling cutters, eliminating the need for other types of tools, further reducing machining costs. Based on the technical solution of this application, not only is the manufacturing difficulty of splines reduced, but machining costs are also lowered, and the manufacturing cycle is shortened. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the spline structure within the overall bladed disk;

[0035] Figure 2 for Figure 1 Enlarged structural diagram of point A in the middle;

[0036] Figure 3 This is a schematic diagram of a round tooth root spline structure;

[0037] Figure 4 A schematic diagram showing the machining status of the angle head and special machining tools;

[0038] Figure 5 A schematic diagram showing the status of the angle head and special machining tools;

[0039] Figure 6 for Figure 4 Enlarged structural diagram of section B in the middle;

[0040] Figure 7 A schematic diagram showing the positional relationship between a dedicated machining tool in machining mode and the spline groove;

[0041] Figure 8 Example 1 of a spline groove measuring tool;

[0042] Figure 9 Example 2 of a spline groove measuring tool. Detailed Implementation

[0043] The present invention includes a milling method for the internal spline of an integral bladed disk, which includes the following steps.

[0044] S1: Confirm the size and shape of the internal spline in the internal spline structure to be machined, and make a special machining tool 4.

[0045] Specialized machining tool 4 is a milling cutter, such as Figure 7 As shown, the special machining tool 4 includes a tool holder 4-1 and a tool head 4-2. The shape of the tool head 4-2 is adapted to the size and shape of the spline groove 2-5.

[0046] Because spline grooves are generally shallow, the cutting edge of the specially designed machining tool 4 only needs to meet the spline groove depth. A shorter cutting edge design increases the overall rigidity of the tool and improves machining accuracy. In this method, the shape of the tool head 4-2 is adapted to the size and shape of the spline groove 2-5, ensuring that the tool shape can cut through the spline groove of the part in one stroke during machining. The tool shape guarantees the spline tooth profile, thus meeting the final spline quality requirements.

[0047] S2: Select angle head 3 for machining;

[0048] The angle head 3 includes: an angle head body 3-1, a machine tool spindle interface 3-2, and a mounting part 3-3, such as... Figure 4 to Figure 6 As shown, a milling cutter for machining is installed on the mounting part 3-3, and the machine tool spindle interface 3-2 is connected to the CNC machine tool.

[0049] like Figure 1 As shown, confirm the inner diameter d of the spline body 2-3 in the internal spline structure, and select an angle head 3 whose length of the mounting part 3-3 is smaller than the inner diameter d. In practical applications, if the inner circle size allows, try to select an angle head with a larger size and higher torque, so that the rigidity will be better during machining.

[0050] S3: Select a ball end mill with a diameter 2-5 mm smaller than the width of the spline groove as the roughing tool.

[0051] In practical applications, ball end mills with a taper are used for rough milling of grooves because the diameter of the ball end is small, allowing for material removal within the spline groove. The reason for using a ball end mill with a taper is that the taper increases the rigidity of the tool, and the machining performance is also improved after the tool shank diameter is increased.

[0052] S4: Based on CNC machine tools, construct a groove machining program for spline grooves 2-5;

[0053] The CNC machine tool is a four-axis or five-axis CNC machine tool. In this solution, an angle head is used to perform machining on a four-axis or five-axis CNC machine tool with a rotating worktable. This allows the angle head and the cutting tool to extend into the inner circle to machine the splines. For each spline machined, the worktable rotates by the angle of one spline, and so on, until all splines are machined.

[0054] In practical applications, the spline shape is drawn and verified within the software according to the standard spline parameter table, and the dimensions of the spline tool are designed based on the spline's graphic shape. In this method, only one tool specification needs to be designed, because the tool for semi-finishing can use the tool for final finishing. Allowances are left in the program, saving tool machining steps and reducing overall costs. The dimensions of the spline tool need to be designed according to the tolerances in the spline parameter table, with the tool's profile dimensions designed to the mean deviation of the spline tolerance.

[0055] The grooving process includes: roughing, semi-finishing, and finishing.

[0056] In the roughing program, using a trochoidal milling strategy with a roughing tool, the spline groove on the inner cylinder of the spline body 2-3 is roughed. In the semi-finishing program, using a dedicated machining tool 4, the centerline of the spline bottom surface is selected, and the spline groove 2-5 is machined using a wire drive based on the planar milling command. During the machining process, allowances are retained on the sidewalls and bottom surface of the spline groove 2-5. In the finishing program, using a dedicated machining tool 4, the centerline of the spline bottom surface is selected, and the spline groove 2-5 is machined using a wire drive based on the planar milling command. No allowances are retained during the machining process.

[0057] S5: Based on the slot machining program, each spline slot 2-5 in the internal spline structure to be machined is machined one by one in the order of roughing, semi-finishing and finishing to obtain the machined internal spline structure.

[0058] The roughing tool and the special machining tool 4 are mounted on the CNC machine tool via the angle head 3. During machining, the roughing tool and the special machining tool 4 are located on the line connecting the center point of the spline bottom surface and the center of the inner cylinder. In this embodiment, the spline groove has a flat bottom, so the tool 4 and the bottom of the spline groove 2-5 share a common center line to ensure that the position of the tool 4 does not shift. When the spline groove has a round bottom, it is sufficient to ensure that the tool 4 is located on the line connecting the center of the round bottom of the spline groove and the center of the inner cylinder.

[0059] In practical applications, enter the cam_general machining module in UG and create a tool. First, create a tapered ball end mill as the roughing tool. Because the diameter of the ball end mill is smaller than that of the spline groove, this embodiment creates a 3mm diameter tapered ball end mill with a single-sided angle of 4 degrees. Use the CAVITY_MILL cavity milling command to create a cycloidal milling machining strategy. The machining parameters are 30 meters per minute, feed per tooth of 0.02mm, and side cutting width of 0.3mm per cut. The cycloidal milling method in roughing uses the side cutting edge of the tool to remove material. The space of the spline groove is narrow, and the cycloidal milling side cutting method can avoid the tool tip impact caused by repeated tool feed and retraction, reduce tool wear, and increase tool stability.

[0060] After roughing, semi-finishing is required. A forming tool with the same shape as the spline is created as a dedicated machining tool 4. Using UG's PLANAR_MILL planar milling command, the center line of the spline bottom surface is selected, and wire drive is used to machine the spline groove. Since there is still a lot of material remaining at the bottom of the spline groove after roughing, the machining parameters need to be reduced during semi-finishing. The machining parameters are 25 meters per minute, 0.017mm per tooth, and 0.1mm allowance on the bottom surface. Although only the bottom surface allowance is left, since the spline shape is V-shaped, there will also be residual material on the side walls of the spline.

[0061] The finishing and semi-finishing methods are basically the same. Use the spline forming cutter, use the UG PLANAR_MILL planar milling command, select the center line of the spline bottom surface, use wire drive to machine the spline groove, the machining parameters are 25 meters per minute, the feed per tooth is 0.017mm, and no allowance is left on the bottom surface.

[0062] In this embodiment, the spline program only requires programming one spline groove. The machining of all spline grooves is completed by rotating the machine tool table. This significantly reduces development time and costs. Furthermore, because a single groove machining program is used, it can be debugged at the initial stage of machining, greatly improving efficiency. In this machining method, the spline groove needs to be rough-machined first using a ball end mill smaller than the spline groove shape and a cycloidal milling method to remove the excess material. Then, a form milling cutter of the same shape as the spline groove is used for semi-finishing, leaving a remaining allowance. Finally, a form milling cutter is used to complete the machining in one pass. The entire machining process is clear, simple, and error-free, greatly improving efficiency and reducing development difficulty.

[0063] In order to detect problems in the machining process in a timely manner, and to replace the spline tool wear at any time during the process, this application also needs to make a spline groove measuring tool 5 to measure the finished spline groove during the machining process.

[0064] like Figure 8 and Figure 9 As shown, the spline groove measuring tool 5 includes: a measuring head 5-2 and a measuring rod 5-1. The measuring head 5-2 is located at the end of the measuring rod 5-1. The size of the measuring tool is adapted to the size of the inner cylinder of the inner spline structure to be processed, and the shape of the measuring head 5-2 is adapted to the inner cavity of the spline groove 2-5.

[0065] The measuring rod 5-1 can be straight, Y-shaped, or star-shaped.

[0066] When the measuring rod 5-1 is in the shape of a straight line, the measuring head 5-2 is set at one or both ends of the measuring rod 5-1;

[0067] When the measuring rod 5-1 is Y-shaped or star-shaped, each branch at its end corresponds to a spline groove 2-5, and the measuring head 5-2 is set at each end of the measuring rod 5-1. Because the spline grooves are evenly distributed on the inner ring of the spline body 2-3, the angle between the measuring heads 5-2 on the Y-shaped or star-shaped spline groove measuring tool 5 can be adapted to the position of the spline grooves in the internal spline structure to be processed. The number of branches on the star-shaped measuring rod 5-1 can be 5, 7, or 9, and can be up to the same as the total number of spline grooves in the internal spline structure to be processed. After all spline grooves have been processed, the star-shaped spline groove measuring tool 5 is used for final testing.

[0068] The processing procedure in step S5 specifically includes the following steps:

[0069] a1: Select any spline groove 2-5 in the spline body 2-3 as the starting point of a branch of the measuring head 5-2 of the spline groove measuring tool 5;

[0070] On the spline body 2-3, find the spline grooves 2-5 that correspond to the positions of all measuring heads 5-2, and mark the unprocessed spline grooves 2-5 as: grooves to be processed.

[0071] a2: The machining of the groove to be machined is completed in the order of roughing, semi-finishing and finishing;

[0072] a3: Using the spline groove measuring tool 5, place the measuring head 5-2 into the processed spline groove 2-5, and pull it from one end to the other along the length of the spline body 2-3 to complete the quality inspection of the spline groove 2-5;

[0073] a4: Repeat steps a1 to a4 until all spline slots 2-5 are machined.

[0074] Due to the unique characteristics of milling splines, spline inspection needs to be performed simultaneously on the milling machine. This solution incorporates a specially designed spline groove measuring tool 5, in the form of a go / no-go gauge, for this purpose. During inspection, the tool can be manually inserted into the spline groove, preventing defects from being discovered only during CMM (Continuous Machine Tool) inspection after machining.

[0075] In this method, the machining of any spline groove follows a sequence of roughing, semi-finishing, and finishing. Only after each machining operation is completed is the next spline groove machined. In practical application, if the total number of spline grooves in the internal spline structure to be machined is even, a straight-line spline groove measuring tool 5 can be used in the early stages of machining. If the total number of spline grooves is odd, a Y-shaped spline groove measuring tool 5 is initially used for measurement. After machining two or three spline grooves, spline groove inspection is performed to ensure that any problems are detected as early as possible, reducing machining costs and improving yield. Later, a Y-shaped or star-shaped multi-ended spline groove measuring tool 5 can be used for inspection, which can improve machining efficiency and also promptly detect tool wear issues.

[0076] Using the technical solution of this invention, splines can be directly machined inside the inner hole of a part using a four-axis CNC or five-axis CNC milling machine and an angle head. This method reduces the manufacturing difficulty of splines, shortens the manufacturing cycle, and provides convenience for the research and development of parts.

Claims

1. A milling method for the internal splines of an integral bladed disk, characterized in that, Includes the following steps: S1: Confirm the size and shape of the internal spline in the internal spline structure to be machined, and make a special machining tool; The special machining tool is a milling cutter, and the cutter head is adapted to the size and shape of the spline groove; S2: Select the angle head for machining; The angle head includes: a mounting part and a machine tool spindle interface, wherein a milling cutter for machining is provided on the mounting part, and the machine tool spindle interface is connected to a CNC machine tool; Confirm the inner diameter of the spline body in the internal spline structure, and select an angle head whose mounting part length is smaller than the inner diameter; S3: Select a ball end mill with a diameter smaller than the width of the spline groove as the roughing tool; S4: Based on a CNC machine tool, construct a groove machining program for the spline groove; The groove machining process includes: a roughing process, a semi-finishing process, and a finishing process; In the roughing process, based on the roughing tool, a cycloidal milling strategy is used to complete the roughing of the spline groove on the inner cylinder of the spline body. In the semi-finishing process, based on the special machining tool, the center line of the spline bottom surface is selected, and the spline groove is machined using line drive based on the planar milling command. During the machining process, the spline groove sidewalls and bottom surface retain allowance. In the finishing process, based on the special machining tool, the center line of the spline bottom surface is selected, and the spline groove is machined using line drive based on the planar milling command, without leaving any allowance during the machining process; S5: Based on the groove machining program, for each spline groove in the internal spline structure to be machined, the machining is completed one by one in the order of roughing, semi-finishing and finishing to obtain the machined internal spline structure. The roughing tool and the special machining tool are mounted on the CNC machine tool through the angle head. During the machining process, the roughing tool and the special machining tool are located on the line connecting the center point of the spline bottom surface and the center of the inner cylinder. In step S2, a spline groove measuring tool also needs to be made; The spline groove measuring tool includes: a measuring head and a measuring rod, wherein the measuring head is disposed at the end of the measuring rod; The dimensions of the measuring tool are adapted to the dimensions of the inner cylinder of the internal spline structure to be processed, and the shape of the measuring head is adapted to the inner cavity of the spline groove; The measuring rod can be straight, Y-shaped, or star-shaped; When the measuring rod is in the shape of a straight line, the measuring head is located at one or both ends of the measuring rod; When the measuring rod is Y-shaped or star-shaped, each branch at its end is adapted to a spline groove, and the measuring head is disposed at the end of each branch of the measuring rod. Step S5 specifically includes the following steps: a1: Select any one of the spline slots in the spline body as the starting point of a measuring head branch of the spline slot measuring tool; On the spline body, find the spline grooves corresponding to the positions of all measuring heads, and denote the unprocessed spline grooves as: grooves to be processed. a2: The machining of the groove to be machined is completed in the order of roughing, semi-finishing and finishing; a3: Using the spline groove measuring tool, place the measuring head in the processed spline groove and pull it from one end to the other along the length of the spline body to complete the quality inspection of the spline groove; a4: Repeat steps a1 to a3 until all the spline slots have been machined; If the total number of spline grooves in the internal spline structure to be processed is even, a straight spline groove measuring tool can be used in the early stage of processing. If the total number of spline grooves in the internal spline structure to be processed is odd, then a Y-shaped spline groove measuring tool is used for initial measurement. After machining two or three spline grooves, the spline grooves are inspected. Later, Y-shaped or star-shaped multi-ended spline groove measuring tools are used for testing.

2. The milling method for the internal spline of an integral bladed disk according to claim 1, characterized in that: The CNC machine tool is a four-axis or five-axis CNC machine tool.

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