Cycloid rough machining method for inverted T-shaped blade root wrapping groove of steam turbine blade

Abstract

The invention discloses a cycloid rough machining method for an inverted-T-shaped blade root wrapping groove of a turbine blade. Relates to the field of turbine blade machining. Rough machining and finish machining of an outer wrapping groove of an existing inverted-T-shaped blade root both adopt a radially-fed forming milling cutter for machining, the forming milling cutter is customized according to the outline of the outer wrapping groove, the manufacturing cost is high, and the forming milling cutter needs to be integrally replaced after being abraded. The method comprises the following steps that the inverted-T-shaped outer wrapping structure blade root is divided into two areas to be milled, an inverted-T-shaped groove serves as a first area, an outer wrapping groove serves as an independent rough milling area, and the area serves as a second area; the second area adopts an end mill; the first area is machined in the radial direction according to a traditional end mill A, redundant allowance of the groove is removed, and then the second area is machined; the cycloid tool path is set to be of an oval structure, and an Elipse Move command is selected according to the size of a blade wrapping groove and the diameter size of an end mill B. The method is applied to the field of machining of the inverted-T-shaped blade root of the turbine blade.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steam turbine blade processing, in particular to a trochoidal rough machining method for outer wrapping groove of inverted T-shaped blade root of steam turbine blade. BACKGROUND

[0002] The inverted T-shaped outer wrapping structure of the steam turbine blade is a key part of the connection between the blade and the disc, and the machining precision directly affects the assembly performance and operation safety of the blade.

[0003] In the prior art, the rough machining and finish machining of the inverted T-shaped outer wrapping groove of the blade root are both processed by using a radial feeding profile milling cutter, the profile milling cutter is customized according to the profile of the outer wrapping groove, the manufacturing cost is high, and the profile milling cutter needs to be replaced as a whole after wearing. The material removal amount is large in the rough machining stage, and the frequent replacement of the profile milling cutter not only reduces the machining efficiency, but also increases the machining allowance and difficulty of finish machining. Moreover, due to the too large length-diameter ratio of the cutter, it is difficult to cut and remove chips in the radial direction, and it is easy to cause the cutter to break teeth due to too large allowance during finish machining, damage the blade, or appear the situation of chatter marks on the groove bottom.

[0004] Therefore, there is an urgent need for a rough machining method for the inverted T-shaped outer wrapping groove of the blade root, which can reduce the cost of the cutter and improve the rough machining efficiency and stability. SUMMARY

[0005] In order to solve the problem that the rough machining and finish machining of the inverted T-shaped outer wrapping groove of the blade root are both processed by using a radial feeding profile milling cutter in the prior art, the profile milling cutter is customized according to the profile of the outer wrapping groove, the manufacturing cost is high, and the profile milling cutter needs to be replaced as a whole after wearing, the present application provides a trochoidal rough machining method for the inverted T-shaped outer wrapping groove of the steam turbine blade.

[0006] The technical scheme of the present application is as follows:

[0007] A trochoidal rough machining method for the inverted T-shaped outer wrapping groove of the steam turbine blade, the method comprising the following steps:

[0008] Step 1: defining the machining area:

[0009] The blade root of the inverted T-shaped outer wrapping structure is divided into two areas for milling, wherein the inverted T-shaped groove is the first area, and the outer wrapping groove is an independent rough milling area, which is the second area;

[0010] Step 2: selecting the machining cutter:

[0011] According to the machining area in step 1, the second area adopts a vertical milling cutter;

[0012] Step 3: planning the trochoidal path:

[0013] First, the first area is machined along the radial direction by using a vertical milling cutter A according to the conventional method, and then the second area is machined after removing the excess allowance of the groove.

[0014] Step four: cycloid parameter setting:

[0015] The cycloid cutter track is set as an elliptical structure, and the Elipse Move command is selected according to the size of the outer package groove of the blade and the size of the B diameter of the end mill;

[0016] Step five: subsequent processing:

[0017] After rough milling, the existing forming milling cutter is used to finish milling the second area to ensure the final size accuracy and surface quality of the outer package structure.

[0018] Further, according to the processing tool selection in step two:

[0019] Step two one: diameter selection of the tool:

[0020] The tool diameter is determined according to the width of the outer package groove, and the tool is smaller than the minimum width of the outer package groove;

[0021] Step two two: length selection of the tool:

[0022] The length of the tool edge satisfies the complete coverage of the radial depth of the groove when processing in the inner-back radial direction.

[0023] Further, the second area in the processing tool selection in step two uses a vertical milling cutter as a non-forming tool.

[0024] Further, according to the cycloid path planning in step three:

[0025] Step three one: second area processing track:

[0026] The second area is changed to vertical milling cutter B processing along the blade height direction, and the cutter track adopts cycloid processing, that is, vertical milling cutter B makes circular motion with a preset radius while continuously feeding along the blade height direction, superimposes the circular cycloid motion of the preset radius, and forms a composite track of spiral advancing type cutting track;

[0027] Step three two: processing of the inverted T outer package groove part:

[0028] The inverted T outer package groove part adopts the method of processing in the inner-back radial direction, that is, using vertical milling cutter B to process half of the depth of the inverted T outer package groove in the blade root and the back radial direction, to ensure that there is no unprocessed area after processing.

[0029] Further, according to the cycloid parameter setting in step four:

[0030] Step four one: width numerical value setting of milling cutter B:

[0031] Width (width) = (the outer package groove width - the end mill B diameter) ÷ 2 - the semi-finish allowance, wherein the semi-finish allowance is 0.1;

[0032] Step four two: the step size value setting of the milling cutter B:

[0033] Step size is set to 0.1;

[0034] Step four three: the feed speed and cutting speed value setting of the milling cutter B:

[0035] The feed rate and cutting speed are set according to the blade material and tool diameter.

[0036] Further, according to the definition of the independent rough milling area in the processing area in step one, the rough milling area is defined as a groove with a width of 6.5 mm, a radial depth of 20.8 mm and a blade height direction depth of 5 mm.

[0037] Further, according to the processing tool selection in step two, according to the blade groove width of 6.5 mm, a 6 mm diameter hard alloy end mill is selected.

[0038] Further, according to the cycloid path setting in the cycloid path planning in step three, when feeding, the 6 mm diameter end mill needs to feed outside the outer package groove and cannot touch the unprocessed part, wherein the inner radial direction and the back radial direction milling depth are 12 mm respectively.

[0039] Further, according to the cycloid parameter setting in step four, when the feed speed is 150 mm / min, the spindle speed is 5000 rpm, and the feed per tooth is 0.0075 mm;

[0040] Width = (6.5 - 6) ÷ 2 - 0.1 = 0.15;

[0041] The step distance is set to 0.1.

[0042] Compared with the prior art, the present application has the following effects:

[0043] The present application reconfigures the processing direction and adjusts the rough and finish machining tool combination strategy, gets rid of the problems of high cost and low efficiency caused by the dependence of the rough milling of the inverted T outer package structure on the profile milling cutter in the prior art, and improves the processing precision and quality of the blade root.

[0044] The tool cost of the present application is reduced (the data is calculated according to the product of the implementation case), the outer package groove uses a general end mill (cost 600 yuan per piece) instead of a special profile milling cutter (2000 yuan per piece). The profile milling cutter is only used for finish machining, and the service life is improved by more than 3 times.

[0045] The invention comprehensively reduces the cost by 75%, such as the cost of a set of 150 blade knives for a certain unit blade is reduced from 18000 yuan to 4000 yuan.

[0046] The invention improves the processing efficiency, wherein the rough machining time is shortened by 88%, such as the rough machining time of a single blade is shortened from 23.17 min to 2.32 min.

[0047] The invention improves the processing quality, solves the profile error caused by large vibration of the forming milling cutter in traditional processing, and significantly reduces the cycloid milling cutting force fluctuation, without tool breaking and slot bottom tremor phenomenon. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The figure is a schematic diagram of the inverted T-shaped outer wrapping structure blade structure of the invention;

[0049] Figure 2 The figure is a schematic diagram of the first area and the second area in the middle milling; Figure 1

[0050] Figure 3 The figure is a schematic diagram of the first area when the traditional vertical milling cutter A is processed in the radial direction, wherein the cutter track is a pink dotted line;

[0051] Figure 4 The figure is a schematic diagram of the second area when the traditional forming milling cutter is processed in the radial direction;

[0052] Figure 5 The figure is a schematic diagram of the vertical milling cutter B when it is processed in the blade height direction, wherein the composite track is a pink spiral line;

[0053] Figure 6 The figure is a schematic diagram of the inverted T-shaped outer wrapping blade root processing size;

[0054] Figure 7 The figure is a left view in the figure; Figure 6 DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the embodiments of the invention clearer, the technical scheme in the embodiments will be described clearly and completely below in combination with the drawings in the embodiments of the invention. The following embodiments are used to illustrate the invention, but not to limit the scope of the invention. DETAILED DESCRIPTION

[0057] In combination with Figure 1 — Figure 5 The invention is described in this embodiment, a cycloid rough machining method for the inverted T-shaped blade root outer wrapping groove of a steam turbine blade;

[0058] Step one: define the processing area:

[0059] ​​The T-shaped outer package structure blade root is divided into two parts for milling, i.e. the T-shaped groove is the first area, and the outer package groove is an independent rough milling area, i.e. the second area.

[0060] Step two: tool selection:

[0061] Figure 2 The second area adopts a general end mill (non-forming tool), the tool diameter is determined according to the width of the outer package groove (cannot be too small, and cannot be greater than the minimum width of the outer package groove), and the tool edge length satisfies the complete coverage of the radial depth of the groove when the inner back is processed in two directions.

[0062] Step three: cycloid path planning:

[0063] First, the first area is processed in the radial direction by using a conventional end mill A, and the tool path is a pink dotted line, as shown in Figure 3 , which aims to remove the excess amount of the groove. Then the second area is processed.

[0064] Figure 2 The second area in Figure 4 is processed in the radial direction by a conventional forming milling cutter, as shown in Figure 5 , and is changed to an end mill B processed in the blade height direction, as shown in Figure 5 . The tool path adopts cycloid processing, i.e. the end mill B makes a circular motion with a preset radius while continuously feeding in the blade height direction, and superimposes the circular cycloid motion with a preset radius to form a composite trajectory of spiral advancing cutting trajectory, such as the pink spiral line in

[0065] Due to the small size of the T-shaped outer package groove of the blade and the small diameter of the end mill B, if the radial depth is processed, the tool is easy to wear and the vibration is extremely large, therefore the T-shaped outer package groove part is processed in the inner back radial direction, i.e. the end mill B is used to process half of the depth of the T-shaped outer package groove in the inner back radial direction of the blade root, to ensure that there is no unprocessed area after processing, as shown in Figure 5 .

[0066] Step four: cycloid parameter setting:

[0067] The cycloid tool path is set as an elliptical structure, the Elipse Move command is selected, and then the corresponding values are set according to the size of the outer package groove of the blade and the diameter of the end mill B as follows:

[0068] Width (width) = (outer package groove width - end mill B diameter) ÷ 2 - half-precision allowance (usually 0.1);

[0069] Step Size (step size) is set to 0.1;

[0070] Feed rate and cutting speed are set according to the blade material and tool diameter.

[0071] Step 5: Subsequent Processing

[0072] After rough milling, use an existing form milling cutter to mill the second area, such as... Figure 2 As shown, precision milling is performed to ensure the final dimensional accuracy and surface quality of the outer structure. Specific Implementation Method Two:

[0074] Combination Figure 6 and Figure 7 This embodiment describes a cycloidal rough machining method for an inverted T-shaped blade root outer groove of a steam turbine blade;

[0075] Taking the inverted T-shaped outer blade root structure of a certain type of steam turbine blade as an example (dimensions as follows) Figure 6 Processing using this method:

[0076] Define the rough milling area as a groove with a width of 6.5 mm, a radial depth of 20.8 mm, and a depth of 5 mm in the blade height direction.

[0077] Based on the blade groove width of 6.5mm, select a carbide end mill with a diameter of 6mm.

[0078] Cycloidal path settings. When feeding, the 6mm diameter end mill must feed from outside the outer groove, avoiding contact with unmachined areas. The milling depth in the inner and back radial directions is 12mm respectively.

[0079] Cutting parameters. Based on the cycloidal parameter settings described in step four, when the feed rate is 150 mm / min, the spindle speed is 5000 rpm, and the feed per tooth is 0.0075 mm;

[0080] Width = (6.5 - 6) ÷ 2 - 0.1 = 0.15; Step size is set to 0.1. Specific implementation method three:

[0082] Combination Figure 1 — Figure 7 This embodiment describes a cycloidal rough machining method for an inverted T-shaped blade root outer groove of a steam turbine blade, based on the machining area defined in step one:

[0083] The locking T-shaped outer casing blade is cleverly divided into two parts for milling. The locking T-groove is defined as Region 1, while the outer casing groove is a separate milling area, Region 2. This division helps to select the most suitable machining strategy and tools based on the characteristics and machining requirements of different regions, thereby improving machining efficiency and quality. DETAILED DESCRIPTION FOUR

[0085] In combination Figure 1 — Figure 7 To illustrate this embodiment, a cycloid rough machining method for the inverted T-shaped blade root outer groove of a steam turbine blade is described according to the machining tool selection in step two:

[0086] For the area 2 in Figure 2 , a general end mill (non-forming tool) is used for machining. The diameter of the tool needs to be accurately determined according to the width of the outer groove, which cannot be too small, otherwise it will increase the number of machining times and time, reducing the efficiency; it cannot be larger than the minimum width of the outer groove, otherwise it cannot be effectively machined. At the same time, the length of the cutting edge must meet the requirement that it can completely cover the radial depth of the groove when machining in the inner-back radial direction, so as to ensure the integrity and accuracy of the machining. DETAILED DESCRIPTION FIVE

[0088] In combination Figure 1 — Figure 7 To illustrate this embodiment, a cycloid rough machining method for the inverted T-shaped blade root outer groove of a steam turbine blade is described according to the cycloid path planning in step three:

[0089] First, for area 1, use milling cutter A to process in the radial direction according to the traditional processing method (the tool path is a radial straight line, as shown in Figure 3 . The main purpose of this step is to remove the excess amount of the groove, and to prepare for subsequent finishing. After completing the machining of the first area, the second area is machined.

[0090] The second area in Figure 2 is machined in the radial direction by a traditional forming milling cutter, as shown in Figure 4 , and is replaced by end mill B machining in the blade height direction, as shown in Figure 5 . The specific machining method is to use cycloid machining, that is, end mill B makes circular motion with a preset radius, while continuously feeding in the blade height direction, superimposes the circular cycloid motion of the preset radius, forms a composite trajectory of spiral advancing cutting trajectory, such as the pink spiral line trajectory in Figure 5 .

[0091] Because the size of the inverted T-shaped outer groove is small, the tool wear will increase sharply when the end mill B is used for the usual radial depth machining, which will affect the machining quality and tool life. Therefore, for the inverted T-shaped outer groove part, we use the method of inner-back radial separate machining. That is, use end mill B to machine half of the depth of the inverted T-shaped outer groove in the inner-back radial direction of the blade root, which can effectively reduce the tool wear during machining, ensure that there is no unprocessed area after machining, and ensure the accuracy and integrity of the machining. DETAILED DESCRIPTION SIX

[0093] In combination Figure 1 — Figure 7 To illustrate this embodiment, a cycloid rough machining method for the inverted T-shaped blade root outer groove of a steam turbine blade is described as follows:

[0094] The cycloid tool path is set as an elliptical structure, and the EllipseMove command is selected. Then, according to the size of the blade outer groove and the diameter of the end mill B, the corresponding values are set.

[0095] The calculation formula for Width is: (outer groove width - end mill B diameter) ÷ 2 + half precision allowance (usually 0.1). The setting of this width needs to consider the actual size of the outer groove and the diameter of the end mill, to ensure that the cycloid machining can cover the entire groove area, while leaving appropriate precision allowance for subsequent finishing.

[0096] Step Size is set to 0.1. The choice of step size directly affects the accuracy and efficiency of machining. Smaller step size can improve machining accuracy, but will increase machining time; larger step size will reduce machining accuracy, but can improve machining efficiency. After comprehensive consideration, the step size is set to 0.1 to improve machining efficiency as much as possible while ensuring machining accuracy.

[0097] Feed rate and Cutting speed need to be set according to the blade material and tool diameter. Different blade materials and tool diameters have different requirements for feed rate and cutting speed. For example, for blade materials with high hardness, the feed rate and cutting speed need to be appropriately reduced to reduce tool wear; for large tool diameters, the feed rate and cutting speed also need to be adjusted accordingly to ensure the stability and safety of machining. Specific implementation method seven:

[0099] In combination Figure 1 — Figure 7 To illustrate this embodiment, a cycloid rough machining method for the inverted T-shaped blade root outer groove of a steam turbine blade is described as follows:

[0100] After rough milling, the existing forming milling cutter is used to finish mill the second area 2, as shown in Figure 2 The purpose of finishing is to ensure the final size accuracy and surface quality of the outer structure. During finishing, machining parameters such as feed rate and cutting speed need to be strictly controlled to ensure that the size accuracy after machining meets the requirements, and the surface quality meets the expected standard. Through finishing, the machining marks left in the rough milling process can be removed, making the surface of the outer structure smoother and more uniform, improving its assembly performance and running safety.

[0101] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make some changes or modifications to the above disclosed technical contents to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any simple modification, equivalent replacement and improvement of the above embodiments, as long as it does not depart from the technical solution of the present application, and is within the spirit and principle of the present application, shall be within the protection scope of the present application.

Claims

1. A cycloidal roughing method for an outer wrap groove of an inverted T-shaped blade root of a steam turbine blade, characterized by, The method comprises the following steps: Step one: define the machining area: The T-shaped outer package structure blade root is divided into two parts for milling, wherein the T-shaped groove is the first area, and the outer package groove is an independent rough milling area, which is the second area; Step two: tool selection: According to the machining area in step one, wherein the second area adopts a ball end mill; Step three: cycloid path planning: First, the first area is machined along the radial direction using a conventional ball end mill A, and after removing the excess amount of the groove, the second area is machined; Step four: cycloid parameter setting: The cycloid tool path is set as an elliptical structure, the Elipse Move command is selected, and the size of the blade outer package groove and the diameter of the ball end mill B are determined; Step five: subsequent machining: After rough milling, the second area is finished by using an existing forming milling cutter to ensure the final size accuracy and surface quality of the outer package structure.

2. The trochoidal roughing method of an outer shroud groove of an inverted T-shaped root of a turbine blade according to claim 1, characterized by, According to the tool selection in step two: Step two one: diameter selection of the tool: The diameter of the tool is determined according to the width of the outer package groove, and the tool is smaller than the minimum width of the outer package groove; Step two two: length selection of the tool: The length of the tool blade is sufficient to cover the radial depth of the groove when machining in the inner and back radial directions.

3. The trochoidal roughing method of an outer shroud groove of an inverted T-shaped root of a gas turbine blade according to claim 2, characterized by, The second area in the tool selection in step two adopts a ball end mill as a non-forming tool.

4. The trochoidal roughing method of an outer shroud groove of an inverted T-shaped blade root of a steam turbine blade according to claim 1, characterized by, According to the cycloid path planning in step three: Step three one: machining track of the second area: The second area is machined along the blade height direction using a ball end mill B, and the tool path adopts cycloid machining, that is, the ball end mill B makes circular motion with a preset radius while continuously feeding along the blade height direction, and the circular cycloid motion with a preset radius is superimposed to form a composite track of spiral advancing cutting track; Step three two: machining of the T-shaped outer package groove part: The T-shaped outer package groove part is machined in the inner and back radial directions, that is, the ball end mill B is used to machine half of the depth of the T-shaped outer package groove in the inner and back radial directions of the blade root to ensure that there is no unprocessed area after machining.

5. The trochoidal roughing method of an outer shroud groove of an inverted T-shaped blade root of a steam turbine blade according to claim 1, characterized by, According to the cycloid parameter setting in step four: Step four one: width numerical setting of the ball end mill B: Width = (outer package groove width - ball end mill B diameter) ÷ 2 - half-finish allowance, wherein the half-finish allowance is 0.1; Step four two: step length numerical setting of the ball end mill B: The step length is set to 0.1; Step four three: numerical setting of the feed speed and cutting speed of the ball end mill B: The feed speed and cutting speed are set according to the blade material and tool diameter.

6. The trochoidal roughening method of an outer shroud groove of an inverted T-shaped root of a turbine blade according to claim 1, characterized by, According to the definition of the rough milling area in the definition of the machining area in step one, the rough milling area is defined as a groove with a width of 6.5 mm, a radial depth of 20.8 mm, and a blade height direction depth of 5 mm.

7. The trochoidal roughening method of an outer shroud groove of an inverted T-shaped root of a turbine blade according to claim 1, characterized by, According to the tool selection in step two, a 6 mm diameter hard alloy ball end mill is selected according to the blade groove width of 6.5 mm.

8. The trochoidal roughening method of an outer shroud groove of an inverted T-shaped root of a turbine blade according to claim 1, characterized by, According to the cycloid path setting in the cycloid path planning in step three, when feeding, the 6 mm diameter ball end mill needs to feed outside the outer package groove and cannot touch the unprocessed part, wherein the milling depth in the inner and back radial directions is 12 mm respectively.

9. The trochoidal roughening method of an outer shroud groove of an inverted T-shaped root of a turbine blade according to claim 1, characterized by, According to the setting of the cycloid parameters described in step four, when the feed speed is 150 mm / min, the spindle speed is 5000 rpm, and the feed per tooth is 0.0075 mm; Width = (6.5-6) ÷ 2 - 0.1 = 0.15; Step distance is set to 0.1.

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