A process for folding joint precision reference surface machining

Abstract

The present application belongs to the machining process, and particularly relates to a process method for machining a precision reference surface of a folding joint. First, the deformation amount of a part clamping is controlled, semi-finishing of the precision reference surface is carried out, and then the part semi-finishing is carried out. The paddle pin hole is machined by using a whole hard alloy cutter, and a single side has a margin. Finally, the precision reference surface of the folding joint is finished by fixing and clamping the paddle pin hole, so that the flatness is not greater than 0.03 mm. The deformation amount of the folding joint clamping is quantitatively controlled in the whole process, the operation is simple and clear, the process is accurate and controllable, and the result is convenient to measure. The flatness of the precision reference surface of the folding joint is not greater than 0.03 mm, that is, the deformation amount of the clamping in the first front face finishing is effectively controlled. The machining quality of the first front face finishing is ensured, and then the machining quality of the second back face finishing is ensured, so that all the sizes of the folding joint completely meet the requirements of the design drawing. The machining method can be referred to for other similar folding joint parts.

Description

Technical Field

[0001] This invention pertains to machining processes, specifically the machining of precision reference surfaces. More specifically, it describes a process for machining the precision reference surface of a folded joint. Background Technology

[0002] The folding joint is an important component of the main rotor hub. It moves through the movement of the sector teeth to achieve the folding motion of the main rotor blades. Therefore, the quality of the folding joint's processing directly affects whether the main rotor blades can be successfully folded.

[0003] The technical challenges faced are:

[0004] 1. The material of the folded joint is 30CrNi4MoA, which is a high-quality high-strength alloy steel material. It has high strength, high toughness, low cold brittle transition stability, and high fatigue strength. The tensile strength σβ is between 1080MPa and 1380MPa. This material has good machinability. During rough machining, the cutting is in the form of fragments and is not easy to get tangled. After the heat treatment process, the parts have a small amount of deformation.

[0005] 2. The folded joint cannot be machined to the required standard in one clamping operation; it requires a first front-side finishing operation and a second back-side finishing operation.

[0006] 3. The datum for the first front finishing is not the same as the datum for the second back finishing, but they are strongly related. Only by ensuring the machining quality of the first front finishing can the machining quality of the back finishing be improved.

[0007] 4. The first front-side finishing process is divided into semi-finishing and finishing. The quality of semi-finishing directly affects the quality of finishing.

[0008] 5. The quality of semi-finishing depends entirely on the accuracy of the reference surface. If the accuracy of the reference surface cannot be guaranteed, then the quality of semi-finishing cannot be guaranteed either.

[0009] 6. In summary, the finishing quality of the folded joint depends entirely on the precision reference surface. Only by ensuring the machining quality of the precision reference surface can the finishing quality of the folded joint be guaranteed. Summary of the Invention

[0010] Technical solution

[0011] A process for machining the precision reference surface of a folding joint involves first controlling the deformation during part clamping and then performing semi-finishing of the precision reference surface until the surface is smooth. Next, semi-finishing is performed on the part itself, using a solid carbide cutter to machine the blade pin hole, leaving a allowance on one side. Finally, by fixing and clamping the blade pin hole, the precision reference surface of the folding joint is finished to ensure a flatness of no more than 0.03 mm.

[0012] Furthermore, a process method for machining the precision reference surface of a folding joint is implemented based on a blade pin hole clamping fixture. The blade pin hole clamping fixture is a base with double lugs, each lug having four positioning pins used for positioning the blade pin holes. The specific operation steps are as follows:

[0013] Step 1) When compiling the roughing program, a platform is designed at the outer circle of the folded joint sector gear and the folded locking pin hole to facilitate the use of clamps during finishing.

[0014] Step 2) After heat treatment, the reference surface of the part is semi-finished until it is exposed to light;

[0015] Step 3) Perform the first semi-finishing, with a single-sided allowance of 0.25mm-0.3mm;

[0016] Step 4) Use the blade pin hole clamping fixture to perform final finishing on the folding joint precision reference surface by fixing and clamping the blade pin hole.

[0017] Step 5) After the semi-finishing is completed, place the folded joint on the inspection table and use a feeler gauge to check the gap between the precision reference surface and the inspection table surface to ensure that the feeler gauge with a thickness of 0.03mm cannot be inserted into the gap.

[0018] Furthermore, step 6) is included: if a feeler gauge with a thickness of 0.03 mm can be inserted into the gap between the accuracy reference surface and the test table surface, then steps 4) and 5) are repeated until the feeler gauge can no longer be inserted into the gap.

[0019] Furthermore, in step 1, the contact surfaces of the platform and the tooling must be on the same horizontal plane;

[0020] Furthermore, during rough machining, the folded joint and the platform are machined from the same forging casting, and the folded joint and the platform are made of the same material, specifically 30CrNi4MoA.

[0021] Furthermore, in step 2, when semi-finishing the reference surface, the clamping torque is 15MPa-17MPa; this torque range has been proven through multiple tests to ensure sufficient clamping force while minimizing part deformation.

[0022] Furthermore, in step 4, the clamping torque is 50 N·m-60 N·m (the torque range has been proven through multiple tests to ensure sufficient clamping force while ensuring that the deformation of the part does not exceed 0.05 mm).

[0023] Furthermore, the perpendicularity between the blade pin hole and the surface of the large fork is no more than 0.05mm.

[0024] Technical effect

[0025] This machining method provides quantitative control over the deformation during clamping of the folded joint throughout the entire process. It is simple and clear to operate, the process is precise and controllable, and the results are easy to measure. It ensures that the flatness of the folded joint's reference surface is no greater than 0.03mm, effectively controlling the deformation during the first front-side finishing process. Guaranteeing the quality of the first front-side finishing process ensures the quality of the second back-side finishing process, ultimately achieving a folded joint where all dimensions fully meet the design drawings. This machining method can be used as a reference for other similar folded joint parts, or parts with similar finishing clamping methods. Attached Figure Description

[0026] Figure 1 Isometric drawing of the part;

[0027] Figure 2 A schematic diagram of the part clamping process;

[0028] Figure 3 This is an isometric drawing of the tooling. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments. The following description represents only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] A process for machining the precision reference surface of a folding joint involves first controlling the deformation during part clamping and then performing semi-finishing of the precision reference surface until the surface is smooth. Next, semi-finishing is performed on the part itself, using a solid carbide cutter to machine the blade pin hole, with a single-sided allowance of 0.25mm-0.3mm. Finally, by fixing and clamping the blade pin hole, the precision reference surface of the folding joint is finished to ensure a flatness of no more than 0.03mm.

[0031] The process method for machining the precision reference surface of the folded joint is based on a blade pin hole clamping fixture. The blade pin hole clamping fixture is a base with double lugs, each lug having four locating pins used for positioning the blade pin holes. The specific operation steps are as follows:

[0032] Step 1) When preparing the machining plan, a platform is designed at the outer circle of the sector gear and the folding lock pin hole of the folding joint. The folding joint and the platform are made of the same material, 30CrNi4MoA. The contact surface of the platform and the tooling must be on the same horizontal plane to facilitate clamping during finishing.

[0033] Step 2) After heat treatment, the folded joint will form an oxide layer on the surface, which is reddish-black in color and mainly a mixture of iron(III) oxide and iron(II) oxide. The surface is uneven and cannot be directly subjected to the first front finishing process, so the precision reference surface semi-finishing process is carried out first.

[0034] Step 3) Perform semi-finishing of the precision reference surface, with a clamping torque of 15 N·m-16 N·m (this torque range has been proven through multiple tests to ensure sufficient clamping force while guaranteeing that the deformation of the part does not exceed 0.05 mm). Completely remove the mixture of iron(III) oxide and iron(II) oxide from the surface of the reference surface, revealing a silvery-white metallic surface;

[0035] Step 4) Perform the first semi-finishing of the front surface, with a clamping torque of 50 N·m-60 N·m (this torque range has been proven through multiple tests to ensure sufficient clamping force while guaranteeing that the part deformation does not exceed 0.05 mm, and that the perpendicularity between the blade pin hole and the large fork surface after machining does not exceed 0.05 mm). Completely remove the mixture of iron oxide and ferric oxide from the front surface of the folded joint, with a single-sided allowance of 0.25-0.3 mm, revealing a silvery-white metallic surface;

[0036] Step 5) Remove any remaining burrs after milling;

[0037] Step 6) Use the blade pin hole clamping fixture to fix and clamp the blade pin hole, and then use the pressure plate to press the folded joint. The clamping torque is 15N·m-20N·m (this torque range has been proven by multiple tests to ensure sufficient clamping force and ensure that the deformation of the parts is no more than 0.03mm). Perform precision machining on the folded joint precision reference surface.

[0038] Step 7) After processing, loosen the pressure plate and let the folded joint be in a free state. Use a lever gauge to calibrate the flatness of the precision reference surface. The runout error of the lever gauge is no more than 0.03mm, which means that the flatness of the precision reference surface is no more than 0.03mm.

[0039] Step 8) If the lever gauge reading error is greater than 0.03mm, then steps 6) and 7) need to be repeated until the lever gauge reading error is no greater than 0.03mm.

[0040] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. 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 process for machining a precision reference surface for a folded joint, characterized in that, First, control the deformation of the part during clamping and perform semi-finishing of the precision reference surface until the surface is smooth. Then, perform semi-finishing of the part, using a solid carbide cutter to machine the blade pin hole, leaving a margin on one side. Finally, perform finishing on the precision reference surface of the folding joint by fixing and clamping the blade pin hole. This is achieved using a blade pin hole clamping fixture, which is a base with double lugs and four locating pins on the lugs for positioning the blade pin hole. The specific operation steps are as follows: Step 1) When compiling the roughing program, a platform is designed at the outer circle of the folded joint sector gear and the folded locking pin hole to facilitate the use of clamps during finishing. Step 2) After heat treatment, the reference surface of the part is semi-finished until it is exposed to light; Step 3) Perform the first semi-finishing, with a single-sided allowance of 0.25mm-0.3mm; Step 4) Use the blade pin hole clamping fixture to perform final finishing on the folding joint precision reference surface by fixing and clamping the blade pin hole. Step 5) After the semi-finishing is completed, place the folded joint on the inspection table and use a feeler gauge to check the gap between the precision reference surface and the inspection table surface to ensure that the feeler gauge with a thickness of 0.03mm cannot be inserted into the gap. Step 6): If a feeler gauge with a thickness of 0.03 mm can be inserted into the gap between the accuracy reference surface and the test platform, repeat steps 4) and 5) until the feeler gauge can no longer be inserted into the gap.

2. The process method for machining the precision reference surface of a folded joint according to claim 1, characterized in that, In step 1, the contact surfaces of the platform and the tooling must be on the same horizontal plane.

3. The process method for machining the precision reference surface of a folded joint according to claim 1, characterized in that, During rough machining, the folded joint and the platform are machined from the same forging casting, and the folded joint and the platform are made of the same material, specifically 30CrNi4MoA.

4. The process method for machining the precision reference surface of a folded joint according to claim 1, characterized in that, When semi-finishing the reference surface in step 2, the clamping torque is 15MPa-17MPa.

5. The process method for machining the precision reference surface of a folded joint according to claim 1, characterized in that, The clamping torque in step 4 is 50N. m-60N m.

6. The process method for machining the precision reference surface of a folded joint according to claim 1, characterized in that, The perpendicularity between the blade pin hole and the surface of the large fork is no more than 0.05mm.

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