A method for processing fir-type milling cutter and mortise

Abstract

This invention relates to a method for regrinding fir tree-shaped end mills, including checking the sharpness and diameter wear of the end mill to determine the regrinding method; rake angle regrinding, using a grinding wheel to regrind the rake angle of the fir tree-shaped end mill; or clearance angle + rake angle regrinding, using a grinding wheel to regrind both the clearance angle and rake angle of the fir tree-shaped end mill. This invention also relates to a method for machining fir tree-shaped tenons using a fir tree-shaped end mill, including checking the end mill, determining the machining method, and performing one-pass machining or two-pass machining. This regrinding method increases the number of regrinding cycles for the fir tree-shaped end mill, extending its service life by 3-4 cycles and reducing the cost of the fir tree-shaped end mill by 20%. This machining method ensures the machining accuracy of the fir tree-shaped tenons.

Description

Technical Field

[0001] This invention belongs to the field of turbine machining technology, specifically a method for grinding and tenoning a fir tree-shaped milling cutter. Background Technology

[0002] The main shaft is a key component of a turboexpander. The moving blades are mounted on the main shaft through the blade root tenon groove to realize their function. The machining quality of the main shaft blade root tenon groove is directly related to the dynamic balance of the rotor, as well as the performance and service life of the entire unit.

[0003] The main shaft of a turbine expander is generally made of alloy steel. The blade root tenon is located on the outer circumference of the hub. The tenon is a fir tree-shaped tenon evenly distributed along the axial direction of the main shaft, typically with multiple stages. The machining of the blade root tenon is completed on a gantry milling machine or specialized equipment. The machining of the blade root tenon must not only ensure that the tooth profile dimensions meet the design drawings, but also requires a high surface roughness of Ra1.6. For machining this type of fir tree-shaped tenon, a fir tree-shaped form milling cutter is used. The tooth profile accuracy of the main shaft tenon relies on the accuracy of the form milling cutter. The regrinding method of the form milling cutter not only ensures the dimensional accuracy and surface roughness of the design drawings, but also increases the number of regrinding cycles, reducing tool costs and exhibiting strong economic efficiency. Therefore, the combined regrinding process of the fir tree-shaped form milling cutter is crucial. Summary of the Invention

[0004] To address the issues of low re-grinding frequency of fir tree-shaped milling cutters and high machining costs of tenon grooves at the root of turbine expander spindle blades, this invention proposes a method for re-grinding fir tree-shaped milling cutters and machining tenons grooves.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for regrinding a fir tree-shaped end mill includes the following steps:

[0007] Step 1: Inspect the milling cutter and determine the re-grinding method.

[0008] For the fir tree-shaped end mills in use, check the sharpness of the cutting edge. If the sharpness meets the requirements, continue to use it; if the sharpness does not meet the requirements, it needs to be re-sharpened.

[0009] When resharpening is required, check the diameter wear of the fir tree-shaped end mill at the tooth profile. Based on the diameter wear, determine the resharpening method. The specific criteria are as follows:

[0010] When the diameter wear is less than or equal to 0.2 mm, the cutting edge is reground using the rake angle regrinding method.

[0011] When the diameter wear exceeds 0.2mm, the cutting edge is re-grinded using a back angle + front angle grinding method.

[0012] Step 2, front corner grinding

[0013] The rake angle of the fir tree-shaped end mill is reground using a grinding wheel. The grinding surface of the grinding wheel is parallel to the rake face. Each rake face is reground one by one, and the regrinding amount is less than or equal to 0.2mm. Once the rake angle cutting edge is qualified, the end mill can continue to be used.

[0014] Step 3, refinish the rear and front corners.

[0015] The back angle of the fir tree-shaped milling cutter is re-grinded using a grinding wheel, with the grinding surface of the grinding wheel corresponding to the angle of the back angle, until the cutting edges of the two back angles are qualified.

[0016] The rake angle of the fir tree-shaped milling cutter is reground using a grinding wheel until the rake angle cutting edge is qualified.

[0017] After the back angle and front angle are ground, the milling cutter can be used again.

[0018] The above-mentioned fir tree-shaped milling cutter re-grinding method, step 2, rake angle re-grinding, further includes: when the sharpness of the cutting edge does not meet the usage requirements, re-grinding and use are repeated, and re-grinding can be repeated 5 times.

[0019] The above-described method for regrinding fir tree-shaped end mills involves grinding the end mills with a grinding wheel, including rough grinding and fine grinding.

[0020] A method for machining fir tree-shaped tenons, using a fir tree-shaped milling cutter, includes the following steps:

[0021] Step 4: Inspect the milling cutter and determine the machining method.

[0022] Fir tree-shaped milling cutters are used to machine fir tree-shaped tenons. The diameter wear of the milling cutter at the tooth profile is checked, and the machining method of the tenon is determined based on the diameter wear. The specific criteria are as follows:

[0023] When the diameter wear is less than 0.2mm, a one-cut forming process is adopted.

[0024] When the diameter wear is greater than or equal to 0.2 mm, a two-blade forming process is adopted.

[0025] Step 5, One-cut forming process

[0026] The center of the fir tree-shaped end mill coincides with the center of the fir tree-shaped tenon, and the fir tree-shaped end mill is formed in one pass.

[0027] Step 6, Two-blade shaping process

[0028] The center of the fir tree-shaped end mill does not coincide with the center of the fir tree-shaped tenon. The center line of the fir tree-shaped end mill is offset by δ / 2 relative to the center line of the fir tree-shaped tenon, where δ is the amount of grinding of the tool diameter.

[0029] The milling cutter is offset from the center of the tenon groove and moves back and forth, with each two passes offsetting to the left once and to the right once.

[0030] In the above-mentioned method for processing fir tree-shaped tenons, in step 5, during the two-blade forming process, the wear of the tool diameter is greater than 0.2 mm, the grinding amount of the tool diameter is δ = 1 mm, and the tool teeth are shifted 0.5 mm towards the center of the tool.

[0031] The beneficial effects of this invention are:

[0032] A method for regrinding fir tree-shaped milling cutters increases the number of regrinding cycles for fir tree-shaped precision milling cutters by combining different fir tree-shaped tenon and groove machining processes. This extends the service life of fir tree-shaped precision milling cutters by 3 to 4 cycles, reduces the cost of fir tree-shaped precision milling cutters by 20%, and is highly economical. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a fir tree-shaped tenon joint;

[0034] Figure 2 This is a schematic diagram of a fir tree-shaped precision milling tool;

[0035] Figure 3 This is a schematic diagram of the diameter of a fir tree-shaped precision milling tool;

[0036] Figure 4 This is a schematic diagram of the grinding rake face of a fir tree-shaped milling cutter;

[0037] Figure 5 This is a schematic diagram of the rake face and flank face of a fir tree-shaped end mill;

[0038] Figure 6 This is a schematic diagram showing the center of the cutting tool coinciding with the center of the mortise.

[0039] Figure 7 This is a schematic diagram of the "one-cut shaping" cutting method;

[0040] Figure 8 This is a schematic diagram of the back face of a fir tree-shaped milling cutter after grinding;

[0041] Figure 9 This is a schematic diagram showing the change in tool diameter after "rear angle + front angle" re-grinding;

[0042] Figure 10 Schematic diagram showing the offset of the tool center from the mortise center by δ / 2;

[0043] Figure 11 This is a schematic diagram of eccentric machining with a fir tree-shaped end mill;

[0044] Figure 12(a) is a schematic diagram of the rake face and flank face of a fir tree-shaped end mill;

[0045] Figure 12(b) is an enlarged view of BB in Figure 12(a);

[0046] Figure 13 This is a schematic diagram showing the 1mm change in tool diameter after "back angle + front angle" re-grinding;

[0047] Figure 14 This is a schematic diagram showing the offset of the tool center from the mortise center by 0.5mm;

[0048] Figure 15 This is a schematic diagram of machining a fir tree-shaped end mill with an eccentricity of 0.5mm. Detailed Implementation

[0049] Example 1

[0050] A method for regrinding a fir tree-shaped end mill includes the following steps:

[0051] Step 1: Perform a pre-inspection on the fir tree-shaped end mill that needs to be regrinded. If the reduction in tool diameter is greater than 0.2 mm, use the "back angle + front angle" regrinding method and determine the regrinding amount of tool diameter δ = 1 mm.

[0052] Step 2: Adjust the grinding wheel and machine tool. According to Figure 12, regrind the flank face of the fir tree-shaped end mill, keeping the clearance angles β1 (8° in the figure) and β2 (20° in the figure) constant. Regrinding is divided into rough grinding and fine grinding, controlling the regrinding amount δ = 10 mm of the tool diameter. +0.04 This reduces the overall diameter of the tool teeth by 1, shifts the overall tool teeth profile towards the tool center by 0.5 mm, while keeping the tool tooth profile profile, tool clearance angles β1 and β2, and pressure surface pitch unchanged. The result is... Figure 13 The cutting tool shown.

[0053] Step 3, adjust the grinding wheel and machine tool according to... Figure 4 The rake angle α (40° as shown in the figure) of the fir tree-shaped milling cutter is precision ground.

[0054] Step 4: After grinding, the fir tree-shaped end mill needs to be cleaned, inspected, and coated.

[0055] Step 5: After sharpening the fir tree-shaped end mill, use... Figure 14 , Figure 15 The process involves precision machining of the spindle tenon groove.

[0056] Figure 1 The finishing of the fir tree-shaped tenon shown is achieved through... Figure 2 The fir tree-shaped precision milling cutter shown is completed. The dimensional accuracy of the tenon tooth profile is entirely guaranteed by the precision of the fir tree-shaped precision milling cutter tooth profile. With the use and resharpening of the fir tree-shaped precision milling cutter, the tool diameter φD1~φD8 of the fir tree-shaped precision milling cutter ( Figure 3As shown, the diameter of the fir tree-shaped milling cutter will decrease. When the diameter reduction is greater than 0.2 mm, the fir tree-shaped milling cutter will not meet the dimensional accuracy and surface roughness requirements of the fir tree-shaped tenon groove. The milling cutter will be scrapped due to the out-of-tolerance diameter φD1~φD8.

[0057] There are two methods for re-grinding fir tree-shaped precision milling forming tools: the "front angle" re-grinding method and the "back angle + front angle" re-grinding method.

[0058] 1. Roughing method for the front corner

[0059] When the diameter wear at each tooth profile of the finish milling cutter is less than 0.2mm, the "rake angle" regrinding method should be selected for tool regrinding. During regrinding, the grinding wheel only regrinds the rake face of the tool, the rake angle α remains unchanged, the rake face regrinding amount is ≤0.2mm, and the tool clearance angles β1 and β2 are not regrinded. See [link to documentation]. Figure 4 , Figure 5 Using this re-sharpening method, a fir tree-shaped finish milling cutter can be re-sharpened approximately 5 times. After multiple re-sharpening of the rake angle and machining use, the finish milling cutter will be scrapped because the reduction in tool diameter is greater than 0.2mm, which does not meet the dimensional requirements of the fir tree-shaped tenon groove.

[0060] Finishing process: During finishing, the center of the finish milling cutter coincides with the center of the spindle tenon groove (see details). Figure 6 The tool path of a finish milling cutter is "one-cut shaping" (see details). Figure 7 ).

[0061] 2. Grinding method for "rear corner + front corner"

[0062] After the forming milling cutter completes the machining of the spindle tenon groove, after multiple rounds of rake angle re-grinding and use, the tool diameter reduction is greater than 0.2mm, which cannot meet the subsequent machining requirements of the spindle tenon groove. At the same time, if the tool does not have chipping or other issues, it can be modified by the following tool "rear angle + rake angle" re-grinding and finishing process to continue its use.

[0063] The tool clearance angle is regrinded by uniformly grinding the clearance angles β1 and β2 along the tool tooth profile. During regrinding, the diameter of all parts of the tool tooth profile is reduced by δ, and the tool tooth profile is shifted δ / 2 towards the tool center. The tool tooth profile, clearance angles β1 and β2, and pressure surface pitch remain unchanged. See details. Figure 5 , Figure 8 , Figure 9 After the clearance angle of the tool is ground, the rake angle α of the tool is ground to make the tool meet the requirements for use in the tenon groove.

[0064] Finishing process: During finishing, the center of the finish milling cutter does not coincide with the center of the spindle tenon groove; the cutter center is offset by δ / 2 (see details). Figure 10 ), where δ is the amount of tool diameter regrinding. The tool path of a finish milling cutter is "two-pass shaping," see details. Figure 11 .

[0065] After the fir tree-shaped precision milling cutter is reground using the above-mentioned "back angle + front angle" method, the tool cost can be reduced by 20%, which is highly economical.

Claims

1. A method for processing fir tree-shaped tenons, characterized in that, Includes the following steps: Step 1, inspect the milling cutter and determine the re-grinding method: For the fir tree-shaped end mills in use, check the sharpness of the cutting edge. If the sharpness meets the requirements, continue to use it; if the sharpness does not meet the requirements, it needs to be re-sharpened. When resharpening is required, check the diameter wear of the fir tree-shaped end mill at the tooth profile. Based on the diameter wear, determine the resharpening method. The specific criteria are as follows: When the diameter wear is less than or equal to 0.2 mm, the cutting edge should be reground using the rake angle regrind method; When the diameter wear exceeds 0.2mm, the cutting edge should be reground using a back angle + front angle regrinding method. Step 2, front corner grinding: The rake angle of the fir tree-shaped end mill is reground using a grinding wheel. The grinding surface of the grinding wheel is parallel to the rake face. Each rake face is reground one by one, and the regrinding amount is less than or equal to 0.2mm. The end mill can be used again after the rake angle cutting edge is qualified. Step 3, Grinding the rear and front corners: The back angle of the fir tree-shaped end mill is re-grinded using a grinding wheel, with the grinding surface of the grinding wheel corresponding to the angle of the back angle, until the cutting edges of the two back angles are qualified. The rake angle of the fir tree-shaped milling cutter was reground using a grinding wheel until the rake angle cutting edge was acceptable; The back angle and front angle have been sharpened; the end mill can continue to be used. Step 4: Inspect the milling cutter and determine the machining method: Fir tree-shaped milling cutters are used to machine fir tree-shaped tenons. The diameter wear of the milling cutter at the tooth profile is checked, and the machining method of the tenon is determined based on the diameter wear. The specific criteria are as follows: When the diameter wear is less than 0.2mm, a one-cut forming process is adopted; When the diameter wear is greater than or equal to 0.2mm, a two-blade forming process is adopted; Step 5, One-cut forming process: The center of the fir tree-shaped end mill coincides with the center of the fir tree-shaped tenon, and the fir tree-shaped end mill is formed in one pass; Step 6, two-blade shaping process: The center of the fir tree-shaped end mill does not coincide with the center of the fir tree-shaped tenon. The center line of the fir tree-shaped end mill is offset by δ / 2 relative to the center line of the fir tree-shaped tenon, where δ is the amount of grinding of the tool diameter. The milling cutter is offset from the center of the tenon groove and moves back and forth, with each two passes offsetting to the left once and to the right once.

2. The method for processing fir tree-shaped tenons according to claim 1, characterized in that, Step 2, front angle sharpening, further includes: if the sharpness of the cutting edge does not meet the usage requirements, sharpening and use are repeated, and sharpening can be repeated 5 times.

3. The method for processing fir tree-shaped tenons according to claim 1, characterized in that, The grinding wheel is used to regrind the fir tree-shaped milling cutter, including rough grinding and fine grinding.

4. The method for processing fir tree-shaped tenons according to claim 1, characterized in that, In step 5, during the two-blade forming process, the wear of the tool diameter is greater than 0.2 mm, the grinding amount of the tool diameter is δ=1 mm, and the overall tool tooth profile is shifted 0.5 mm towards the tool center.

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