A method for restoring the embedded handle after the fracture of the rear handle of a round broach

Abstract

The application provides a method for restoring the embedded handle after the fracture of the rear handle of a circular broach, comprising the following steps: measuring and determining the fracture position and size of the original rear handle, performing turning processing on the rear guide part of the broach, processing the step structure and the annular groove, heating the new rear handle for thermal assembly, and fixing by adopting three-point positioning threads. The method realizes the reliable repair of the fractured rear handle by combining the thermal assembly and mechanical locking, and has the characteristics of simple processing technology, low repair cost and high connection reliability.

Description

Technical Field

[0001] This application relates to the field of machining technology, specifically to a method for restoring the shank of a circular broach after it breaks. Background Technology

[0002] A broach is an important precision machining tool. Its shank's primary function is to act as a rear support for broaches larger than 60mm and heavier, preventing them from tilting during operation. The structure of a broach typically includes a shank, neck, transition taper, leader, cutting teeth, alignment teeth, rear guide, and shank. The integrity of the shank significantly impacts the broach's performance.

[0003] Currently, in the manufacturing and use of broaches, the common methods for fixing the broach shank mainly include two types: integral machining and mechanical connection. Integral machining has the advantages of simple structure and high connection strength, but the cost is relatively high; although mechanical connection is convenient for assembly, it is prone to loosening and loss of precision.

[0004] In actual production, the back shank of a broach may break due to material defects, overload, fatigue failure, improper heat treatment, or other reasons. Currently, broaches with broken back shanks are typically scrapped, which not only wastes a significant amount of resources but also increases production costs.

[0005] The existing technology has the following main problems: During routine production, processing, and use, there is a lack of effective repair methods for broken broach shanks, leaving them only the option of scrapping, resulting in significant economic losses. Furthermore, the few existing repair solutions suffer from technical defects such as poor connection reliability and difficulty in guaranteeing precision. Summary of the Invention

[0006] In view of this, this application provides a method for restoring the retaining shank after a circular broach has broken, which solves the problem in the prior art that there is no effective repair method after the broach's rear shank breaks, and the only option is to scrap it, resulting in economic losses.

[0007] This application provides a method for restoring the shank of a circular broach after it breaks, including the following steps:

[0008] The location and size of the original rear shank fracture were determined by measurement. The outer diameter, roundness and coaxiality of the rear guide were measured using a coordinate measuring machine or precision measuring tools to establish the baseline data.

[0009] Perform turning of the guide section after broaching, including:

[0010] The first roughing is performed using carbide tools with a feed rate f≤0.15mm / r, a depth of cut ap≤1mm, and a cutting speed of 80-100m / min to remove the surface oxide layer.

[0011] A second finishing turn is performed using ceramic cutting tools, with a feed rate f≤0.08mm / r, a depth of cut ap≤0.2mm, and a cutting speed of 120-150m / min, to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm;

[0012] A ring groove is machined on the stepped structure, with a groove depth of 0.5-1mm, a surface roughness Ra≤1.6μm, and a cylindricity error controlled within 0.01mm;

[0013] The first rear shank is designed and machined according to the dimensions of the stepped structure, and three through threaded holes are arranged at 120° intervals along the circumference of the rear guide part of the circular broach. Each threaded hole has a countersunk hole structure of 90° or 120°.

[0014] The first rear handle is placed in a medium-temperature tempering furnace and heated to 350℃, and held for 15-20 minutes. The temperature uniformity is controlled within ±5℃. The first rear handle is a newly customized rear handle.

[0015] A dedicated centering fixture is used for heat fitting assembly. The leveling error of the fixture base is controlled within 0.02mm / 1000mm, and the centering accuracy is ≤0.01mm.

[0016] After natural cooling, apply medium-strength thread-locking agent to the threaded connection surface, and screw the three screws through the threaded holes respectively, so that the screw ends extend into the annular groove for limiting and fixing. Tighten in steps using a torque wrench, and control the screw tightening torque error within ±5%.

[0017] The first rear handle and the stepped structure are fitted with the following parameters:

[0018] diameter The following uses an H7 / u6 fit with an interference fit of 0.015-0.025mm;

[0019] diameter H7 / u7 fit, interference fit 0.020-0.032mm;

[0020] diameter The above uses an H7 / u8 fit with an interference fit of 0.025-0.040mm;

[0021] The mating surfaces are inspected using blue light, and the contact area ratio is ≥85%, with contact points evenly distributed.

[0022] The selection and installation of the screws include:

[0023] Select screws with a strength grade of 12.9;

[0024] For diameter Screws, tightened with a torque of 25-30 N·m;

[0025] For diameter Screws, tightened with a torque of 45-50 N·m;

[0026] For diameter Screws, tightened with a torque of 70-80 N·m;

[0027] The thread fit clearance is selected as 6g / 6H.

[0028] The location and size of the original rear shank fracture were determined by measurement. The outer diameter, roundness and coaxiality of the rear guide were measured using a coordinate measuring machine or precision measuring tools to establish the baseline data.

[0029] Perform turning of the guide section after broaching, including:

[0030] The first roughing is performed using carbide tools with a feed rate f≤0.15mm / r, a depth of cut ap≤1mm, and a cutting speed of 80-100m / min to remove the surface oxide layer.

[0031] A second finishing turn is performed using ceramic cutting tools, with a feed rate f≤0.08mm / r, a depth of cut ap≤0.2mm, and a cutting speed of 120-150m / min, to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm;

[0032] Micron-level stereolithography is used to print a transition connection layer on the fracture surface using epoxy acrylate photosensitive resin material. The laser power is controlled at 80-100mW and the scanning speed is 200-300mm / s.

[0033] The process of printing a transitional connection layer on the fracture surface includes: printing a honeycomb-shaped base grid with a unit size of 50-100 micrometers and a gradient distribution of structural density, which gradually decreases from the inside to the outside; and setting micro-barb structures with a height of 15-25 micrometers.

[0034] Layered solid fabrication technology was used to stack 42CrMo alloy sheets layer by layer, with the thickness of the alloy sheets starting from 0.1 mm and increasing to 0.2 mm layer by layer.

[0035] The layers are bonded together using modified epoxy resin structural adhesive, with an adhesive application rate of 0.15-0.20 g / cm³ per layer. 2 ;

[0036] The pressing pressure is 3-5 MPa, and the pressing force increases by 10% with each layer.

[0037] Interlayer alignment accuracy ≤ 0.02 mm, vacuum degree during stacking process ≤ 10 Pa;

[0038] Perform stress relief heat treatment at 200-250℃ for 2-3 hours, then cool with the furnace.

[0039] After cooling, three through threaded holes are arranged every 120° along the circumference. Each threaded hole has a countersunk hole structure of 90° or 120°, and three screws are screwed in through the threaded holes respectively.

[0040] The modified epoxy resin structural adhesive uses a gradient formulation:

[0041] The bottom layer uses a high-toughness formula with a shear strength ≥25MPa;

[0042] The middle layer uses a standard formula and has a temperature resistance of -40℃ to 150℃.

[0043] The surface layer uses a high-strength formula and has a curing time of 120 minutes (120℃).

[0044] The bond strength shall not be less than 85% of the strength of the parent material.

[0045] The method further includes performing the following tests after molding:

[0046] Ultrasonic flaw detection is performed every 5 floors.

[0047] After final molding, X-ray inspection is performed to ensure that there are no internal defects;

[0048] The surface hardness must be tested and must reach at least 90% of that of the raw material.

[0049] Dynamic balancing was performed, and the dynamic balancing level reached G2.5.

[0050] The location and size of the original rear shank fracture were determined by measurement. The outer diameter, roundness and coaxiality of the rear guide were measured using a coordinate measuring machine or precision measuring tools to establish the baseline data.

[0051] Perform turning of the guide section after broaching, including:

[0052] The first roughing is performed using carbide tools with a feed rate f≤0.15mm / r, a depth of cut ap≤1mm, and a cutting speed of 80-100m / min to remove the surface oxide layer.

[0053] A second finishing turn is performed using ceramic cutting tools, with a feed rate f≤0.08mm / r, a depth of cut ap≤0.2mm, and a cutting speed of 120-150m / min, to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm;

[0054] The first rear handle is placed in a medium-temperature tempering furnace and heated to 350℃, and held for 15-20 minutes. The temperature uniformity is controlled within ±5℃. The first rear handle is a newly customized rear handle.

[0055] Three through threaded holes are arranged every 120° along the circumference. Each threaded hole has a countersunk hole structure of 90° or 120°, and three screws are screwed in through the threaded holes to fix it.

[0056] An elastic compensation structure is designed between the first rear shank and the original rear guide, including:

[0057] It uses three elastic diaphragms evenly distributed at 120°, made of 42CrMo alloy steel with a hardness of HRC32-36;

[0058] The diaphragm thickness is precisely controlled between 1.5-2mm, with an inner-to-outer thickness ratio of 1.2:1;

[0059] The effective working length is 0.4-0.5 times the diameter of the rear shank;

[0060] Install a bearing support system, including:

[0061] Select double-row angular contact ball bearings with P4 precision;

[0062] The bearing preload is adjusted by a precision nut and controlled between 5% and 8% of the dynamic load.

[0063] The bearing housing is made of 40Cr quenched and tempered steel in an integral design.

[0064] Radial clearance is controlled within 0.01-0.015 mm;

[0065] Assembly includes:

[0066] The elastic diaphragm is installed using a special positioning fixture, and the position of the elastic diaphragm is staggered with the position of the threaded hole.

[0067] The circumferential distribution error of the three diaphragms should be controlled to be ≤0.5°;

[0068] The perpendicularity between the diaphragm and the connecting surface is ≤0.02mm;

[0069] The installation torque should be controlled between 20-25 N·m;

[0070] Setting up a bearing system includes:

[0071] The bearing housing bore diameter accuracy requirement is H6 grade;

[0072] The interference fit of the bearing outer ring is 0.01-0.02mm;

[0073] The perpendicularity between the bearing end face and the housing is ≤0.005mm;

[0074] The preload is controlled by a special torque wrench.

[0075] The performance parameters of the elastic diaphragm include:

[0076] Material elastic modulus: 210 GPa;

[0077] Yield strength: ≥835MPa;

[0078] Fatigue strength: ≥400MPa;

[0079] Elastic deformation: 0.2-0.3mm;

[0080] Bearing preload: 2000-3000N.

[0081] The restored insert must meet the following criteria:

[0082] Static testing:

[0083] Radial runout ≤ 0.01 mm;

[0084] Axial runout ≤0.015mm;

[0085] Coaxiality ≤ 0.02mm;

[0086] Angle swing ≤ 0.1°;

[0087] Dynamic detection:

[0088] Vibration value at operating speed ≤ 0.8 mm / s;

[0089] Temperature rise ≤15℃;

[0090] Noise level ≤75dB.

[0091] The assembly environment requirements include:

[0092] The temperature in the constant-temperature workshop is 20±2℃.

[0093] Relative humidity should be controlled between 45% and 65%.

[0094] Illuminance not less than 500 lux;

[0095] The flatness of the work surface is ≤0.05mm / m 2 ;

[0096] Regularly check the machine tool's accuracy to ensure machining stability.

[0097] This application has the following technical effects:

[0098] It can effectively repair and replace the broken shank, avoiding the economic losses caused by scrapping the broach;

[0099] It adopts a combination of thermal assembly and mechanical locking, which has high connection reliability and operational stability;

[0100] It has low repair costs, high efficiency, and strong reliability.

[0101] The processing conditions are easy to meet, making production and manufacturing convenient. Attached Figure Description

[0102] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below:

[0103] Figure 1 A schematic diagram of the rear shank fracture provided in an embodiment of this application;

[0104] Figure 2 A schematic diagram of the machining and embedding shape of the rear guide portion provided in an embodiment of this application;

[0105] Figure 3 This is a schematic diagram of the first rear handle structure provided in an embodiment of this application;

[0106] Figure 4 This is a schematic diagram of broken handle repair provided in an embodiment of this application;

[0107] Figure 5 This is a schematic diagram of screw clamping provided for an embodiment of this application. Detailed Implementation

[0108] This application provides a method for restoring the shank of a circular broach after it breaks, including:

[0109] First embodiment:

[0110] S1: Measure and determine the location and size of the original rear shank fracture, and use a coordinate measuring machine or precision measuring tool to measure the outer diameter, roundness and coaxiality of the rear guide to establish the baseline data;

[0111] Before repairing a broken broach shank, it is necessary to examine the broken area (such as...). Figure 1 A comprehensive measurement and inspection is conducted to ensure the dimensional and assembly accuracy after repair. Specifically, a coordinate measuring machine or other precision measuring instruments (such as inside and outside micrometers, roundness testers, etc.) are used to perform detailed dimensional measurements on the rear guide section at the fracture location.

[0112] During the measurement process, the following aspects are the focus: First, the outer diameter of the rear guide needs to be measured at multiple points in different locations to determine whether there is ellipticity or taper error; second, roundness measurement is performed by measuring different cross sections to obtain the roundness error data of the rear guide; finally, coaxiality measurement is performed by using the undamaged part as a reference to measure the coaxiality relationship between the rear guide and other key parts (such as the front guide, cutting teeth, etc.).

[0113] In addition, special attention should be paid to the influence of ambient temperature on the measurement results. The ambient temperature should be maintained within the range of 20±2℃, and the workpiece should be ensured to reach thermal equilibrium with the ambient temperature before measurement. For parts with high dimensional accuracy requirements, it is recommended to use multiple measurements and take the average value to reduce the influence of random errors.

[0114] The purpose of obtaining this baseline data is twofold: firstly, to provide accurate dimensional references for subsequent processing, ensuring a precise fit between the newly manufactured rear shank and the original rear guide; and secondly, to provide fundamental data for quality control, allowing for the evaluation of repair effectiveness by comparing data before and after the repair. All measurement data should be recorded in detail, and corresponding measurement record tables should be drawn up to provide a reference for subsequent processes.

[0115] It should be noted that if other damage (such as cracks or deformation) is found at the fracture site during the measurement process, it should also be recorded. This information is of significant reference value for the selection of subsequent repair techniques and parameter determination. At the same time, it is recommended to observe and record the morphological characteristics of the fracture surface, which helps in analyzing the cause of the fracture and provides a basis for preventing similar failures.

[0116] S2: Perform broaching and turning of the guide section.

[0117] After completing the measurement data acquisition, the next step is to perform turning on the guide section of the broach. This process is divided into two stages: roughing and finishing, each with its specific process parameters and technical requirements.

[0118] S2 includes:

[0119] S2.1: Use carbide tools for the first rough turning, with a feed rate f≤0.15mm / r, a depth of cut ap≤1mm, and a cutting speed of 80-100m / min to remove the surface oxide layer;

[0120] The main purpose of the roughing stage is to remove the surface oxide layer and uneven parts of the fractured area, creating a good foundation for subsequent finishing. In this stage, carbide cutting tools are used, with P10-P20 grade inserts recommended. The tool rake angle should be 6°-8°, and the clearance angle 8°-10°. Machining parameters should be controlled within the following ranges: feed rate not exceeding 0.15 mm / r, depth of cut controlled within 1 mm, and cutting speed maintained at 80-100 m / min. These parameters consider both machining efficiency and tool life and machining quality.

[0121] During roughing, the following points should be paid special attention to: First, ensure that the cutting fluid is sufficient and the flow rate is stable. It is recommended to use a cutting fluid with a concentration of 4%-6% and a flow rate of not less than 20L / min. Second, intermittent feed should be used, pausing the feed every 3-5mm to effectively control the accumulation of cutting heat. Finally, observe the shape and color of the chips in a timely manner, and adjust the cutting parameters immediately if any abnormalities are found.

[0122] S2.2: Use ceramic cutting tools for a second finishing turn, with a feed rate f≤0.08mm / r, a depth of cut ap≤0.2mm, and a cutting speed of 120-150m / min to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm;

[0123] The main task of the finishing stage is to machine the required stepped structure. Ceramic cutting tools are used in this stage to achieve better machining accuracy and surface quality. It is recommended to use Al2O3-based nitride ceramic inserts with a tip radius of 0.4 mm. Finishing parameters must be strictly controlled: feed rate not exceeding 0.08 mm / r, depth of cut controlled within 0.2 mm, and cutting speed increased to 120-150 m / min. Special attention should be paid to leaving a finishing allowance of 0.02-0.05 mm, as this allowance is crucial for subsequent precision fits.

[0124] During the finishing process, the following aspects need to be focused on: First, check the accuracy of the machine tool before machining, especially the spindle runout error should be controlled within 0.005mm; second, the workpiece should be clamped using a three-jaw chuck in conjunction with a tailstock support to ensure stability during machining; third, check the tool wear regularly, and replace the tool in time when obvious wear is found to ensure machining accuracy.

[0125] To ensure machining quality, it is recommended to perform online monitoring during the machining process. A dial indicator can be used to check the workpiece runout. At the same time, it is important to control the temperature of the cutting zone, and it is advisable to perform a dimensional check after machining each critical dimension. If any accuracy deviation is found, the machining parameters should be adjusted or the cutting tool replaced promptly.

[0126] The entire turning process should be carried out in a constant temperature environment, with the workshop temperature maintained at 20±2℃ and the relative humidity controlled between 45% and 65%. This can minimize the impact of thermal deformation on machining accuracy. At the same time, it is recommended to record key parameters during the machining process, including cutting force, spindle current, and vibration values. These data are of significant reference value for process optimization and quality control.

[0127] S2.3: Machine an annular groove on the stepped structure, with a groove depth of 0.5-1mm, a surface roughness Ra≤1.6μm, and a cylindricity error controlled within 0.01mm;

[0128] like Figure 2 As shown, S2.1-S2.2 respectively perform turning machining on the fractured area, and S2.3 further machines the annular groove (embedded in the outer shape) to facilitate the installation of the newly designed first rear shank.

[0129] S3: The first rear shank is designed and machined according to the dimensions of the stepped structure, and three through threaded holes are arranged at 120° intervals along the circumference of the rear guide part of the circular broach. Each threaded hole has a countersunk hole structure of 90° or 120°.

[0130] After machining the stepped structure of the guide section, it is necessary to design and machine a matching first rear shank (such as...). Figure 3 This involves designing and machining the threaded fixing structure. This step requires high precision and directly affects the reliability of the final assembly.

[0131] The first step is the design of the first rear shank. Based on the previously measured dimensions of the stepped structure, the mating parts of the first rear shank are designed. The design of the mating surfaces must consider the requirements for thermal fit, with a surface roughness requirement of Ra0.8 and a coaxiality error controlled within 0.01mm. The rear shank material is selected as 42CrMo, and the heat treatment requires a hardness of HRC28-32 after quenching and tempering to ensure sufficient strength and good toughness.

[0132] When machining the first rear shank, a CNC lathe is used for roughing and finishing. The roughing allowance is controlled within 0.3-0.5mm, and the finishing is performed in two stages: the first finishing allowance is 0.1mm, and the second finishing allowance is 0.02-0.03mm. The cylindricity error of the mating surfaces is required to be controlled within 0.005mm, and the surface hardness uniformity deviation is not to exceed ±2HRC.

[0133] The arrangement of the threaded holes is another crucial point in this step. Three threaded holes are arranged at 120° intervals along the circumference; this uniform arrangement ensures a uniform distribution of the fixing force. Special attention must be paid to the following points when machining the threaded holes: the perpendicularity error between the drilling centerline and the axis must be controlled within 0.02mm; the positional accuracy error of the threaded holes must be controlled within ±0.05mm; and the angular distribution error of the three threaded holes must not exceed ±0.5°.

[0134] Each threaded hole is designed with a countersunk head structure, with a countersunk angle of 90° or 120° available. The specific angle selection depends on the screw type and stress conditions. Machining the countersunk hole requires a specialized countersunk drill. The countersunk depth must ensure the screw head is completely embedded, but not too deep, which would affect strength. The surface roughness of the countersunk hole should be Ra1.6 to ensure a good fit with the screw head.

[0135] The machining process for threaded holes is as follows: first, use a center drill for positioning; then, drill a through hole with a drill bit; next, use a reamer for precision reaming; and finally, machine the threads and countersunk head. A forming tap is used for thread machining to obtain better thread surface quality. The thread accuracy grade requirement is 6H, and the effective engagement length of the thread is not less than 1.5 times the thread diameter.

[0136] During the machining process, the following points should be noted: When drilling, use low speed and high feed to prevent drilling deviation; during tapping, ensure sufficient cutting fluid lubrication and use chip breaking method; the machining dimensions of all holes must strictly follow the drawing requirements, and inspection records should be kept.

[0137] Finally, a comprehensive inspection of the machined threaded holes is performed, including: checking thread accuracy using a thread gauge, checking the countersunk angle using a universal tool microscope, and checking the hole's position and perpendicularity using a coordinate measuring machine. It is also recommended to perform a thread torque test on each threaded hole to ensure the expected tightening effect is achieved during assembly.

[0138] S4: Place the first rear handle into a medium-temperature tempering furnace and heat it to 350℃. Hold it at that temperature for 15-20 minutes. The temperature uniformity should be controlled within ±5℃. The first rear handle is a newly customized rear handle.

[0139] After machining the first shank, the next step is heat assembly and fixing. This process includes three main steps: heat treatment, heat fitting assembly, and thread fixing, each of which requires strict control of process parameters.

[0140] The first step is the heat treatment process. The machined first shank is placed in a medium-temperature tempering furnace for heating. The tempering furnace needs to be preheated to ensure temperature uniformity. During heating, the temperature rise rate is controlled at 100℃ / hour to avoid stress concentration caused by rapid temperature increases. When the temperature reaches 350℃, it is held for 15-20 minutes, and the furnace temperature fluctuation must be controlled within ±5℃ during this period. To monitor temperature uniformity, it is recommended to install temperature sensors at different locations on the workpiece to record temperature data in real time.

[0141] Controlling the heat treatment environment is also crucial. Good hot air circulation should be maintained inside the furnace; forced convection can be used to ensure uniform heating of all parts of the workpiece. Simultaneously, to prevent oxidation of the workpiece surface, a protective gas (such as nitrogen or argon) with a purity of not less than 99.99% can be introduced.

[0142] S5: A dedicated centering fixture is used for hot fitting assembly. The leveling error of the fixture base is controlled within 0.02mm / 1000mm, and the centering accuracy is ≤0.01mm.

[0143] In the hot-fitting assembly process, a dedicated centering fixture is used. The fixture design must consider thermal expansion and contraction, and a special alloy steel with a low coefficient of thermal expansion is selected. Leveling the fixture base is crucial; a precision level is used to ensure the leveling error is controlled within 0.02mm / 1000mm. The centering device employs a three-point positioning principle, combined with a photoelectric sensor, to achieve a centering accuracy of ≤0.01mm.

[0144] The assembly process needs to be fast and accurate. Once the first rear handle reaches the designated temperature, it should be quickly removed from the tempering furnace and transferred to the assembly station using a special insulated clamp. Before assembly, the cleanliness of both mating surfaces should be checked again to ensure there are no oil stains, dust, or other impurities. During assembly, force should be applied evenly to avoid eccentricity or tilting. The entire hot assembly process is recommended to be completed within 3 minutes to fully utilize the difference in thermal expansion.

[0145] Figure 4 This is a schematic diagram of the repaired product.

[0146] S6: After natural cooling, apply medium-strength thread-locking agent to the threaded connection surface, and screw the three screws through the threaded holes respectively, so that the screw ends extend into the annular groove for limiting and fixing. Tighten in steps using a torque wrench, and control the screw tightening torque error within ±5%.

[0147] After the workpiece has cooled to room temperature naturally (usually 4-6 hours), proceed with the thread fixing step. First, check the condition of the threaded hole to ensure there is no deformation or damage. Apply a medium-strength threadlocker evenly to the threaded connection surface. It is recommended to use an anaerobic threadlocker with a temperature resistance of not less than 150℃. The amount applied should be moderate, avoiding too much or too little.

[0148] The screw installation employs a step-by-step tightening method. First, screw in the three screws individually, but not completely tighten them; the screw tips should just extend into the annular groove. Second, using a calibrated torque wrench, pre-tighten in a diagonal, alternating sequence, controlling the torque to 60% of the final tightening torque. Third, tighten again in the same sequence to achieve the specified tightening torque value. Throughout the entire tightening process, the torque error must be controlled within ±5%. Figure 5 This is a schematic diagram showing the assembly of screws. Marked as 1 is the first rear shank, marked as 2 is the screw, and marked as 3 is the guide section of the broach.

[0149] To ensure tightening quality, it is recommended to use a combined torque and angle control method during the tightening process, and record the tightening torque and rotation angle data for each screw. After tightening, mark the screws for easy inspection later. It is also recommended to wait for the threadlocker to fully cure (usually 24 hours at room temperature) before proceeding with further operations.

[0150] Finally, a comprehensive inspection of the assembled components should be conducted, including the measurement and recording of parameters such as coaxiality, runout, and screw tightening torque. It is recommended to conduct a re-inspection 24 hours after the initial assembly to confirm the stability of all performance indicators. All test data should be recorded in detail as a basis for quality traceability.

[0151] The first rear handle and the stepped structure are fitted with the following parameters:

[0152] diameter The following uses an H7 / u6 fit with an interference fit of 0.015-0.025mm;

[0153] diameter H7 / u7 fit, interference fit 0.020-0.032mm;

[0154] diameter The above uses an H7 / u8 fit with an interference fit of 0.025-0.040mm;

[0155] The mating surfaces are inspected using blue light, and the contact area ratio is ≥85%, with contact points evenly distributed.

[0156] The selection and installation of the screws include:

[0157] Select screws with a strength grade of 12.9;

[0158] For diameter Screws, tightened with a torque of 25-30 N·m;

[0159] For diameter Screws, tightened with a torque of 45-50 N·m;

[0160] For diameter Screws, tightened with a torque of 70-80 N·m;

[0161] The thread fit clearance is selected as 6g / 6H.

[0162] Second embodiment:

[0163] S1: Measure and determine the location and size of the original rear shank fracture, and use a coordinate measuring machine or precision measuring tool to measure the outer diameter, roundness and coaxiality of the rear guide to establish the baseline data;

[0164] S2: Perform broaching and turning of the guide section, including:

[0165] S2.1: Use carbide tools for the first rough turning, with a feed rate f≤0.15mm / r, a depth of cut ap≤1mm, and a cutting speed of 80-100m / min to remove the surface oxide layer;

[0166] S2.2: Use ceramic cutting tools for a second finishing turn, with a feed rate f≤0.08mm / r, a depth of cut ap≤0.2mm, and a cutting speed of 120-150m / min to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm;

[0167] The descriptions of S1-S2 are the same as in the first embodiment, and will not be repeated here.

[0168] S3: Micron-level stereolithography is used to print a transition connection layer on the fracture surface using epoxy acrylate photosensitive resin material. The laser power is controlled at 80-100mW and the scanning speed is 200-300mm / s.

[0169] The process of printing a transitional connection layer on the fracture surface includes: printing a honeycomb-shaped base grid with a unit size of 50-100 micrometers and a gradient distribution of structural density, which gradually decreases from the inside to the outside; and setting micro-barb structures with a height of 15-25 micrometers.

[0170] After the guide section is machined, the next crucial step is to establish a transition layer on the fracture surface (which is relatively smooth after machining, making it easier to create a transition layer). This step employs micron-level stereolithography, a high-precision additive manufacturing process that enables precise structural control at the microscale.

[0171] First, the fracture surface needs special treatment before photolithography. This includes surface cleaning, plasma activation, and applying an undercoat. The cleaning process uses ultrasonic cleaning with a specific cleaning agent to remove surface oil and oxides; plasma activation is to increase surface energy and enhance the adhesion of subsequent materials; the selection of the undercoat must consider its compatibility with the photosensitive resin.

[0172] In terms of material selection, epoxy-based photosensitive resins are used, as these materials possess excellent mechanical and processing properties. The resin selection criteria include: viscosity between 200-300 mPa·s, curing shrinkage less than 3%, and elongation at break greater than 15%. To improve material performance, nanoscale reinforcing agents, such as nano-silica or carbon nanotubes, can be added to the resin, with the addition ratio controlled between 0.5-1%.

[0173] During photolithography, controlling the laser power is crucial and must be strictly controlled within the range of 80-100mW. Excessive power can lead to over-crosslinking or localized overheating of the material, while insufficient power cannot ensure adequate curing. A scanning speed of 200-300mm / s is recommended, as this range ensures both good forming quality and high processing efficiency.

[0174] A special scanning strategy is employed when printing the honeycomb base mesh. The process involves contour scanning first, followed by internal filling, and finally compensation scanning. The cell size is controlled between 50-100 micrometers, a range that ensures both structural strength and good flexibility. The gradient design of the structural density is crucial; a density distribution that gradually decreases from the inside out better adapts to stress transfer requirements.

[0175] The design and fabrication of the micro-barb structure is the most delicate part of the entire process. The barb height is controlled between 15-25 micrometers, the angle is designed between 60°-75°, and the spacing is evenly distributed. These barbs not only increase the mechanical interlocking force, but also produce micro-deformation under stress, providing additional stress buffering.

[0176] During the printing process, the following parameters must be strictly controlled: ambient temperature maintained at 23±1℃, relative humidity controlled at 40%-60%, and dustproof rating meeting Class 1000. Printing must be carried out in a warm light environment to avoid the influence of ambient light on the photosensitive resin. Simultaneously, the entire worktable surface must be kept level, and vibration must be controlled below 0.1μm.

[0177] In terms of quality control, each completed layer undergoes real-time inspection, including observing the structural integrity using a microscope and measuring surface roughness using a profilometer. If defects are found, process parameters must be adjusted immediately or the layer must be reprinted. It is recommended to calibrate key parameters of the photolithography system at regular intervals, including laser power, spot size, and scanning accuracy.

[0178] Finally, post-printing processing is also crucial, including the removal of residual monomers and UV curing. The curing process must be carried out under nitrogen protection, with the temperature controlled at 60-80℃ for 2-4 hours. This ensures the material achieves optimal mechanical properties. Key parameters must be recorded throughout the entire process to provide a basis for quality traceability.

[0179] It should be noted that the original fracture surface is usually irregular, and the surface may have an oxide layer, burrs, etc. Therefore, S2 turning can: remove the surface oxide layer, providing a clean base surface and a regular machining surface, which facilitates subsequent precise machining. Then, in S3, photolithography and printing are performed on the treated regular surface, which can: improve the accuracy and controllability of the photolithography process and ensure the uniformity of the honeycomb base mesh.

[0180] S4: 42CrMo alloy sheets are stacked layer by layer using a layered solid manufacturing technique, wherein the thickness of the alloy sheets starts from 0.1mm and increases to 0.2mm layer by layer;

[0181] The use of layered solid fabrication technology in the manufacturing of the first rear shank is an innovative approach. This technology constructs the part by stacking thin sheets of 42CrMo alloy layer by layer, achieving excellent mechanical properties and microstructure control.

[0182] The first step is the preparation of the alloy sheets. 42CrMo alloy sheets require precision rolling, demanding strict control of the chemical composition: carbon content 0.38-0.45%, chromium content 0.9-1.2%, and molybdenum content 0.15-0.25%. During rolling, the temperature must be strictly controlled, maintained between 850-900℃, and the thinning rate per pass must be controlled at 15-20% to ensure the uniformity of the sheet's microstructure and mechanical properties.

[0183] The thickness of the thin sheets is controlled using a progressive design, starting with a 0.1mm thick sheet at the bottom and then increasing in increments of 0.01mm until reaching 0.2mm. This progressive design ensures structural strength while achieving a uniform stress transition. The surface roughness of each sheet is required to be Ra0.4, and the flatness error is controlled within 0.005mm.

[0184] Interface treatment during the stacking process is crucial. Each sheet requires surface activation before stacking, including two steps: plasma cleaning and chemical activation. The plasma cleaning parameters are: power 300-400W, processing time 30-40 seconds; chemical activation uses a specially formulated activation solution, with an immersion time controlled at 20-30 seconds. This ensures that the interlayer bonding strength reaches more than 90% of the strength of the parent material.

[0185] During the lamination process, a precision positioning system is used for alignment. This system includes a laser guide and a mechanical positioning device, with a positioning accuracy requirement of ≤0.01mm. After each layer is placed, a pressure sensor is used to check the uniformity of pressure distribution, and the pressure is controlled within the range of 5-7MPa. Simultaneously, the entire lamination process is carried out in a vacuum environment, with the vacuum level maintained above 10^-3 Pa.

[0186] Interlayer bonding employs diffusion welding, with the following welding parameters: temperature 1050-1100℃, pressure 8-10MPa, and holding time 30-40 minutes. To prevent oxidation, the entire welding process is conducted under a high-purity hydrogen atmosphere (purity ≥99.999%). After each layer is welded, the bonding quality is inspected using an ultrasonic flaw detector to ensure the absence of inclusions, porosity, and other defects.

[0187] The following parameters must be strictly controlled during the stacking process: ambient temperature 23±1℃, relative humidity 40-60%, and worktable levelness error ≤0.02mm / 1000mm. An intermediate inspection should be carried out every 3-5 layers, including dimensional measurement, flatness inspection, and ultrasonic testing. If any problems are found, the process parameters should be adjusted in a timely manner.

[0188] In terms of quality control, a complete process parameter recording system should be established, including the batch number of each sheet, surface treatment parameters, welding parameters, etc. It is also recommended to reserve sampling locations during the stacking process for subsequent mechanical property testing and metallographic analysis. X-ray flaw detection should be performed on each critical component after completion to ensure internal quality.

[0189] Finally, the overall heat treatment after stacking is also crucial. The heat treatment process includes: normalizing (880-900℃) + quenching (840-860℃, oil cooling) + tempering (550-580℃) to obtain the desired microstructure and mechanical properties. The required hardness after heat treatment is HRC28-32, tensile strength ≥900MPa, and reduction of area ≥45%.

[0190] Figure 4 This is a schematic diagram for repairing a broken handle.

[0191] S5: Modified epoxy resin structural adhesive is used for bonding between layers, with an adhesive application rate of 0.15-0.20 g / cm² per layer. 2 ;

[0192] The pressing pressure is 3-5 MPa, and the pressing force increases by 10% with each layer.

[0193] Interlayer alignment accuracy ≤ 0.02 mm, vacuum degree during stacking process ≤ 10 Pa;

[0194] In the layering and stacking of 42CrMo alloy sheets, interlayer bonding is a crucial step in ensuring overall performance. This process uses modified epoxy resin structural adhesive for bonding, requiring strict control of process parameters and environmental conditions.

[0195] First, the selection and preparation of the structural adhesive are crucial. A two-component modified epoxy resin structural adhesive is used, with the ratio of the main agent to the curing agent precisely controlled at 100:30 (by weight). The performance requirements for the structural adhesive are: viscosity (25℃) 8000-12000 mPa·s, pot time (25℃) 40-60 minutes, shear strength ≥25 MPa, and temperature resistance not lower than 120℃. To improve the toughness of the structural adhesive, a nano-level toughening agent can be added, with the addition ratio controlled at 2-3%.

[0196] Special attention needs to be paid to controlling the amount of adhesive used during the application process. The amount of adhesive applied for each layer should be strictly controlled between 0.15-0.20 g / cm³. 2 This range ensures sufficient bond strength while preventing excessive adhesive layer buildup. Precision metering equipment is used for application, with uniformity deviation controlled within ±5%. Care should be taken to avoid positioning holes and critical functional surfaces during application; localized masking can be used for protection.

[0197] The lamination process employs a progressive pressurization method. The initial pressure is set at 3 MPa, and with each additional layer, the pressure increases by 10%, but does not exceed the upper limit of 5 MPa. This progressive pressurization effectively removes excess adhesive layers while ensuring that the bottom layer does not deform due to overpressure. A multi-point synchronous pressurization system is used to apply pressure, with pressure uniformity deviation controlled within ±3%.

[0198] To ensure interlayer alignment accuracy ≤0.02mm, a combination of a dual-path laser alignment system and mechanical positioning is employed. The laser alignment system achieves a resolution of 0.001mm, with deviations monitored in real-time via CCD images. Mechanical positioning utilizes precision locating pins, with the cylindricity error of the pins controlled within 0.002mm and a clearance of 0.005-0.008mm.

[0199] Vacuum control is crucial for ensuring bonding quality. The entire lamination process is conducted in a vacuum chamber, with a required vacuum level of ≤10 Pa. The vacuuming process is divided into two stages: the first stage involves rapid vacuuming to 100 Pa, followed by a second stage of slow vacuuming to the target value, avoiding sudden vacuuming that could cause air bubbles. Simultaneously, a desiccant is placed within the vacuum chamber to control ambient humidity.

[0200] The temperature control system employs a zoned heating method, maintaining the operating temperature at 23±2℃. To prevent temperature fluctuations from affecting the bonding quality, a water circulation thermostat is installed on the outer wall of the vacuum chamber. Simultaneously, thermocouples monitor the temperature of each zone in real time, allowing for timely adjustments upon detection of any abnormalities.

[0201] After the layers are stacked, allow 24 hours for natural curing. The curing environment temperature should be controlled at 23±2℃ and the relative humidity at 45-65%. After curing, perform final dimensional inspection and mechanical property testing to ensure that the product quality meets the design requirements.

[0202] S6: Perform stress relief heat treatment at 200-250℃ for 2-3 hours, followed by furnace cooling.

[0203] S7: After cooling, arrange three through threaded holes every 120° along the circumference. Each threaded hole has a countersunk hole structure of 90° or 120°, and screw three screws through the threaded holes respectively.

[0204] The modified epoxy resin structural adhesive uses a gradient formulation:

[0205] The bottom layer uses a high-toughness formula with a shear strength ≥25MPa;

[0206] The middle layer uses a standard formula and has a temperature resistance of -40℃ to 150℃.

[0207] The surface layer uses a high-strength formula and has a curing time of 120 minutes (120℃).

[0208] The bond strength shall not be less than 85% of the strength of the parent material.

[0209] The following tests are performed after molding:

[0210] Ultrasonic flaw detection is performed every 5 floors.

[0211] After final molding, X-ray inspection is performed to ensure that there are no internal defects;

[0212] The surface hardness must be tested and must reach at least 90% of that of the raw material.

[0213] Dynamic balancing was performed, and the dynamic balancing level reached G2.5.

[0214] Third embodiment:

[0215] S1: Measure and determine the location and size of the original rear shank fracture, and use a coordinate measuring machine or precision measuring tool to measure the outer diameter, roundness and coaxiality of the rear guide to establish the baseline data;

[0216] S2: Perform broaching and turning of the guide section, including:

[0217] S2.1: Use carbide tools for the first rough turning, with a feed rate f≤0.15mm / r, a depth of cut ap≤1mm, and a cutting speed of 80-100m / min to remove the surface oxide layer;

[0218] S2.2: Use ceramic cutting tools for a second finishing turn, with a feed rate f≤0.08mm / r, a depth of cut ap≤0.2mm, and a cutting speed of 120-150m / min to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm;

[0219] S3: Place the first rear handle into a medium-temperature tempering furnace and heat it to 350℃. Hold it at that temperature for 15-20 minutes. The temperature uniformity is controlled within ±5℃. The first rear handle is a newly customized rear handle.

[0220] S4: Three through threaded holes are arranged every 120° along the circumference. Each threaded hole has a countersunk hole structure of 90° or 120°. Three screws are screwed in through the threaded holes to fix the hole.

[0221] For detailed explanations of S1-S4, please refer to Example 1, which will not be repeated here.

[0222] S5: An elastic compensation structure is designed between the first rear shank and the original rear guide, including:

[0223] It uses three elastic diaphragms evenly distributed at 120°, made of 42CrMo alloy steel with a hardness of HRC32-36;

[0224] The diaphragm thickness is precisely controlled between 1.5-2mm, with an inner-to-outer thickness ratio of 1.2:1;

[0225] The effective working length is 0.4-0.5 times the diameter of the rear shank;

[0226] The elastic compensation structure design between the first rear shank and the original rear guide is a key element in ensuring overall performance. This elastic compensation structure employs a specially designed diaphragm system, which can effectively alleviate stress concentration during operation and improve overall reliability.

[0227] First, the material selection and heat treatment of the elastic diaphragm are crucial. 42CrMo alloy steel is chosen as the diaphragm material, with its chemical composition strictly controlled: carbon content 0.40-0.45%, chromium content 0.9-1.2%, and molybdenum content 0.15-0.25%. The heat treatment process includes: quenching and tempering (quenching temperature 840-860℃, tempering temperature 520-540℃) and aging treatment (200℃×2h), ultimately achieving a hardness of HRC32-36. The microstructure after heat treatment is required to be: tempered sorbite + dispersed carbides, with a grain size level of 8-9.

[0228] The diaphragm structure is designed with a 120° evenly distributed arrangement to ensure uniform stress distribution. Precision positioning grooves are used for the circumferential positioning of the three diaphragms, with a positioning accuracy controlled within 0.01mm. Each diaphragm is precision machined with a dimensional tolerance grade of IT6 and a form and position tolerance zone of 0.01mm. The diaphragm geometry employs a gradient curve design to achieve optimal stress distribution.

[0229] Controlling the diaphragm thickness is crucial for ensuring performance. The overall thickness is controlled within the range of 1.5-2mm, with a thickness ratio of 1.2:1 between the inner and outer ends. This gradual design allows for a more reasonable stress distribution and improves fatigue life. High-precision CNC milling machines with specialized fixtures are used during machining, with thickness tolerances controlled within ±0.01mm. The surface roughness requirement is Ra0.4, and the surface treatment employs nitriding followed by polishing.

[0230] The effective working length is closely related to the back shank diameter and is controlled at 0.4-0.5 times the back shank diameter. This ratio is the optimal value determined through finite element analysis and experimental verification, which can provide appropriate elastic deformation while ensuring sufficient rigidity. The working length is machined using a profile grinding machine, and the contour error is controlled within 0.005mm.

[0231] Precise control of the diaphragm installation position is crucial. The coaxiality of the mounting surfaces must be 0.01 mm, and the perpendicularity 0.02 mm. Specialized tooling should be used during installation to ensure uniform force distribution on the three diaphragms, with preload deviation not exceeding 5%. After installation, the flatness of the diaphragms in their free state must be checked to ensure no initial deformation.

[0232] Quality control in the manufacturing process includes the following aspects:

[0233] Material incoming inspection: composition analysis, metallographic examination, and mechanical property testing;

[0234] Process control: 100% inspection of critical dimensions and online measurement of geometric tolerances;

[0235] Heat treatment process control: temperature uniformity ±5℃, hardness distribution detection;

[0236] Assembly process control: preload measurement, coaxiality measurement;

[0237] Each membrane sheet must undergo the following performance tests:

[0238] Static stiffness test: linearity deviation of the loading displacement curve ≤ 3%;

[0239] Dynamic fatigue test: No cracks or permanent deformation were observed after 106 cycles;

[0240] Frequency response test: The natural frequency must meet the design requirements;

[0241] To ensure assembly quality, a detailed assembly process specification should be established:

[0242] Clean all contact surfaces to ensure they are free of oil and impurities;

[0243] Check the geometric accuracy of the mounting surface;

[0244] Install the diaphragms in the marked order;

[0245] Use a torque wrench to tighten evenly;

[0246] Measure key assembly parameters;

[0247] Conduct functional testing;

[0248] Finally, the overall performance of the assembled elastic compensation structure was verified, including:

[0249] Static displacement test;

[0250] Dynamic response testing;

[0251] Temperature effect test;

[0252] Reliability assessment;

[0253] All manufacturing and testing data must be fully recorded, and product files must be established to ensure traceability. Detailed assembly and maintenance procedures should also be developed to ensure standardized use and maintenance in the future.

[0254] S1-S4 are used to measure and establish reference data, and a regular stepped structure and a prefabricated screw connection structure are obtained through turning. Finally, the first rear shank is heat-treated.

[0255] S5 introduces an elastic compensation structure: an elastic diaphragm is placed between the first rear stem and the original rear guide.

[0256] S1-S4 complete the basic machining and connection preparation. S5 adds an elastic compensation mechanism on this basis, providing dynamic compensation capability. Therefore, the screw connection provides basic fixation, while the elastic compensation structure provides dynamic adjustment capability, and the bearing system provides motion support.

[0257] S6: Set up a bearing support system, including:

[0258] Select double-row angular contact ball bearings with P4 precision;

[0259] The bearing preload is adjusted by a precision nut and controlled between 5% and 8% of the dynamic load.

[0260] The bearing housing is made of 40Cr quenched and tempered steel in an integral design.

[0261] Radial clearance is controlled within 0.01-0.015 mm;

[0262] The design and installation of the bearing support system is a precision component of the entire system, directly affecting operational accuracy and service life. This system requires comprehensive consideration of multiple factors, including load characteristics, temperature effects, and assembly processes.

[0263] First, the bearing selection is crucial. A double-row angular contact ball bearing with P4 precision and a 25° contact angle is chosen. This design can withstand both radial and axial loads. The bearing steel is GCr15SiMn, with specific requirements: carbon content 0.95-1.05%, chromium content 1.40-1.65%, and hardness HRC62-64. The purity of the bearing steel must be ≤-II, and the carbide uniformity ≤3, to ensure reliability during high-speed operation.

[0264] Controlling bearing preload is a critical process parameter. The preload is adjusted using a precision nut to maintain it between 5% and 8% of the dynamic load. Preload measurement employs a combination of strain gauge and torque methods, with the strain gauges having an accuracy class of 0.1. The adjustment process consists of two stages: coarse adjustment and fine adjustment.

[0265] Coarse adjustment: Use a dedicated torque wrench to make a preliminary adjustment according to the calculated theoretical torque value.

[0266] Fine-tuning: By testing bearing temperature rise and vibration, the preload is finely adjusted to the optimal state.

[0267] The bearing housing is designed as a single-piece structure made of 40Cr quenched and tempered steel. The heat treatment process for the material is quenching and tempering (quenching temperature 850℃, tempering temperature 580℃), achieving a hardness of HRC28-32. The main dimensional tolerance grade for the single-piece design is IT6, with a geometric tolerance zone of 0.01mm. The structural features of the bearing housing include:

[0268] The cylindricity error of the bearing mounting surface is ≤0.005mm;

[0269] The perpendicularity error of the end face is ≤0.008mm;

[0270] The surface roughness of the mating surface is Ra0.4;

[0271] Design effective lubrication channels and sealing structures;

[0272] Radial clearance is controlled using a precision matching method, maintaining it within the range of 0.01-0.015 mm. This range represents the optimal value after considering factors such as temperature variations and load deformation. Clearance is measured using the following method:

[0273] Static clearance is measured using a dial indicator at room temperature;

[0274] Dynamic clearance is monitored using an eddy current sensor during operation;

[0275] The change in clearance was measured at different temperatures;

[0276] Controlling the assembly process is also very important:

[0277] Clean and inspect all parts;

[0278] Geometric accuracy inspection of bearing housing mounting surfaces;

[0279] Pre-assembly and clearance inspection of bearings;

[0280] Cleanliness inspection of the lubrication system;

[0281] Installation of seals;

[0282] Adjustment and inspection of preload;

[0283] Trial operation and performance testing;

[0284] The design of a lubrication system should consider the following factors:

[0285] Use ISO VG32 high-speed bearing oil;

[0286] The oil circuit design ensures adequate lubrication;

[0287] Set an oil level observation window;

[0288] Equipped with temperature monitoring device

[0289] The monitoring system configuration includes:

[0290] Temperature sensor: accuracy ±0.1℃;

[0291] Vibration sensor: frequency range 0.1-10kHz;

[0292] Displacement sensor: resolution 0.1μm;

[0293] Online monitoring system;

[0294] Quality control measures include:

[0295] Bearing arrival inspection: dimensions, precision, surface quality;

[0296] Bearing housing machining process control;

[0297] Recording key parameters during the assembly process;

[0298] Operational test data collection and analysis;

[0299] Special Notes:

[0300] The assembly environment temperature is controlled at 20±2℃;

[0301] Relative humidity should be controlled between 45% and 65%.

[0302] Dustproof rating reaches Class 1000;

[0303] Assembly tools must be calibrated;

[0304] Usage and maintenance recommendations:

[0305] Regularly check the quality of the lubricating oil;

[0306] Monitor bearing temperature rise and vibration;

[0307] Record runtime parameters;

[0308] Develop a preventative maintenance plan;

[0309] All assembly processes and debugging data must be recorded in detail, and a complete technical file must be established. At the same time, contingency plans should be developed to deal with any possible abnormal situations.

[0310] S7: Perform assembly, including:

[0311] The elastic diaphragm is installed using a special positioning fixture, and the position of the elastic diaphragm is staggered with the position of the threaded hole.

[0312] The circumferential distribution error of the three diaphragms should be controlled to be ≤0.5°;

[0313] The perpendicularity between the diaphragm and the connecting surface is ≤0.02mm;

[0314] The installation torque should be controlled between 20-25 N·m;

[0315] The installation of the elastic diaphragm is a critical step in the entire assembly process, requiring precise control of positioning, torque, and geometric parameters to ensure the stability and reliability of the system.

[0316] The first step involves the design and calibration of a dedicated positioning fixture. This fixture is made of high-strength aluminum alloy (7075-T6), and its surface hardness and wear resistance are improved through anodizing. The main features of the fixture include:

[0317] The flatness error of the reference surface is ≤0.005mm;

[0318] The cylindricity error of the locating pin hole is ≤0.003mm;

[0319] The angle scale accuracy is 0.1°;

[0320] Integrated torque monitoring system;

[0321] Preparatory work before installation is very important:

[0322] Clean all contact surfaces and wipe them with a lint-free cloth dampened with isopropyl alcohol.

[0323] Inspect the surface of the elastic diaphragm to ensure it is free of scratches and deformation;

[0324] Verify the accuracy of the positioning fixture;

[0325] Prepare a calibrated torque wrench;

[0326] Check the specifications and condition of all fasteners;

[0327] The elastic diaphragm is installed using a staggered arrangement, offset from the threaded holes by 120°. This arrangement optimizes stress distribution and improves overall stiffness. Specific installation steps:

[0328] Adjust the positioning fixture to a horizontal position with an error ≤ 0.02mm / 1000mm;

[0329] Install the first diaphragm as a reference;

[0330] Use an angle division device to determine the positions of the second and third diaphragms;

[0331] Install each piece individually while monitoring the circumferential distribution error;

[0332] Controlling the circumferential distribution error is crucial, requiring it to be ≤0.5°. The following methods are used to ensure installation accuracy:

[0333] Real-time monitoring using a high-precision photoelectric angle sensor;

[0334] Position verification was performed using a coordinate measuring machine.

[0335] A position compensation mechanism is included, allowing for fine-tuning.

[0336] Real-time data recording is performed for each installation step;

[0337] The perpendicularity between the diaphragm and the connecting surface is controlled within 0.02mm, and the following measures are taken:

[0338] Real-time monitoring is performed using a precision level.

[0339] Install a dedicated support frame to provide stable support;

[0340] Verticality was verified using a multi-point measurement method;

[0341] Use shims for fine-tuning if necessary;

[0342] The installation torque should be controlled within the range of 20-25 N·m, and special attention is required during this process.

[0343] Use a digital torque wrench with an accuracy class of ±2%.

[0344] A step-by-step tightening method is adopted:

[0345] Step 1: Achieve 40% of the target torque;

[0346] Step 2: Achieve 70% of the target torque;

[0347] Step 3: Reach the final torque value;

[0348] The torque error at each fastening point is controlled within ±1 N·m;

[0349] Quality control measures during installation:

[0350] Establish a detailed installation checklist;

[0351] Record the installation parameters for each diaphragm;

[0352] Real-time monitoring of key geometric parameters;

[0353] Take photos and archive each assembly step;

[0354] Inspection items after installation:

[0355] Diaphragm circumferential position measurement;

[0356] Verticality full circumference inspection;

[0357] Torque value verification;

[0358] Diaphragm prestress condition inspection;

[0359] Overall coaxiality measurement;

[0360] Special Notes:

[0361] The installation environment temperature should be maintained at 20±2℃;

[0362] Avoid direct sunlight to prevent uneven temperature distribution;

[0363] To prevent contamination by dust and impurities;

[0364] Operators must undergo specialized training;

[0365] Assembly record requirements:

[0366] Record the serial number of each membrane;

[0367] Record the installation torque and angle data;

[0368] Record the model and accuracy of the testing instrument;

[0369] Record information about operators and inspectors;

[0370] Establish complete assembly records;

[0371] After installation, functional testing is also required:

[0372] Static displacement test;

[0373] Vibration characteristic testing;

[0374] Stiffness testing;

[0375] Verification of prestressed state;

[0376] All test data must be fully recorded and compared with design requirements to ensure compliance with technical specifications. A detailed maintenance plan should also be developed to ensure long-term stable system operation.

[0377] S8: Set up the bearing system, including:

[0378] The bearing housing bore diameter accuracy requirement is H6 grade;

[0379] The interference fit of the bearing outer ring is 0.01-0.02mm;

[0380] The perpendicularity between the bearing end face and the housing is ≤0.005mm;

[0381] The preload is controlled by a special torque wrench.

[0382] The assembly process of a bearing system is a precision task that requires strict control over fit accuracy, assembly process and preload to ensure the operating performance and service life of the bearing system.

[0383] First, let's look at the machining requirements for the bearing housing. The bearing housing bore diameter must meet H6 precision standards, and the specific machining process is as follows:

[0384] Rough machining allowance: 0.3-0.5mm;

[0385] The machining process is: precision milling → precision boring → grinding.

[0386] The final dimensional tolerance band width is between 10-14 μm;

[0387] Cylindricity error is controlled within 0.004mm;

[0388] The surface roughness of the aperture is Ra0.4;

[0389] The interference fit between the bearing outer ring and the bearing housing should be controlled within 0.01-0.02mm, which requires precise dimensional measurement and temperature control.

[0390] Use a three-point inside micrometer to measure the bearing housing bore diameter;

[0391] The outer ring diameter of the bearing is measured using an outside micrometer;

[0392] The ambient temperature for measurement should be controlled at 20±0.5℃;

[0393] The cleanliness level of the mating surfaces shall not be lower than NAS6 level;

[0394] The perpendicularity between the bearing end face and the housing must be ≤0.005mm. This requires the following measures:

[0395] Process control:

[0396] The datum surface is machined in a single clamping operation.

[0397] Use a precision vertical milling machine;

[0398] Online measurement is performed using precision measuring instruments;

[0399] Detection method:

[0400] Use a high-precision dial indicator;

[0401] Roundness tester was used for measurement;

[0402] Multi-point sampling verification;

[0403] The preload is controlled using a dedicated torque wrench. Specific requirements are as follows:

[0404] The torque wrench has an accuracy grade of 0.5.

[0405] Minimum scale division: 0.1 N·m;

[0406] It has overload protection function;

[0407] Equipped with a digital display of torque value;

[0408] Control of assembly process flow:

[0409] Cleaning and inspection of bearing housings;

[0410] Clean with a lint-free cloth;

[0411] Inspect the surface condition;

[0412] Measure critical dimensions;

[0413] Preparation for bearing installation;

[0414] Preheat the bearing to 30-35℃;

[0415] Check the bearing's rotational flexibility;

[0416] Prepare specialized installation tools;

[0417] Bearing installation process;

[0418] Hydraulic assembly method is used;

[0419] Control assembly speed to ≤5mm / min;

[0420] Monitor changes in assembly force;

[0421] Preload adjustment;

[0422] Step-by-step loading method;

[0423] Real-time monitoring of bearing temperature rise;

[0424] Record data during the adjustment process;

[0425] The performance parameters of the elastic diaphragm include:

[0426] Material elastic modulus: 210 GPa;

[0427] Yield strength: ≥835MPa;

[0428] Fatigue strength: ≥400MPa;

[0429] Elastic deformation: 0.2-0.3mm;

[0430] Bearing preload: 2000-3000N.

[0431] The restored insert must meet the following criteria:

[0432] Static testing:

[0433] Radial runout ≤ 0.01 mm;

[0434] Axial runout ≤0.015mm;

[0435] Coaxiality ≤ 0.02mm;

[0436] Angle swing ≤ 0.1°;

[0437] Dynamic detection:

[0438] Vibration value at operating speed ≤ 0.8 mm / s;

[0439] Temperature rise ≤15℃;

[0440] Noise level ≤75dB.

[0441] The assembly environment requirements include:

[0442] The temperature in the constant-temperature workshop is 20±2℃.

[0443] Relative humidity should be controlled between 45% and 65%.

[0444] Illuminance not less than 500 lux;

[0445] The flatness of the work surface is ≤0.05mm / m 2 ;

[0446] Regularly check the machine tool's accuracy to ensure machining stability.

Claims

1. A method for restoring the shank of a circular broach after it breaks, characterized in that, Includes the following steps: The location and size of the original rear shank fracture were determined by measurement. The outer diameter, roundness and coaxiality of the rear guide were measured using a coordinate measuring machine or precision measuring tools to establish the baseline data. The back guide section of the broach is machined, including: a first rough turning using carbide tools, with a feed rate f≤0.15mm / r, depth of cut ap≤1mm, and cutting speed 80-100m / min, to remove the surface oxide layer; a second finish turning using ceramic tools, with a feed rate f≤0.08mm / r, depth of cut ap≤0.2mm, and cutting speed 120-150m / min, to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm; a transition connecting layer is printed on the fracture surface using micron-level stereolithography technology with epoxy acrylate photosensitive resin material, wherein the laser power is controlled at 80-100mW and the scanning speed is 200-300mm / s; the printing of the transition connecting layer on the fracture surface includes: printing a honeycomb basic mesh with a unit size of 50-100 The structure is micrometers thick, with a gradient density distribution that gradually decreases from the inside out. Micro-barb structures are incorporated, with a height of 15-25 micrometers. Layered solid fabrication technology is used to stack 42CrMo alloy sheets, with the thickness starting at 0.1 mm and increasing to 0.2 mm layer by layer. Modified epoxy resin structural adhesive is used for bonding between layers, with an application rate of 0.15-0.20 g / cm² per layer. The pressing pressure is 3-5 MPa, increasing by 10% with each layer. The interlayer alignment accuracy is ≤0.02 mm, and the vacuum degree during stacking is ≤10 Pa. Stress-relieving heat treatment is performed at 200-250℃ for 2-3 hours, followed by furnace cooling. After cooling, three through-holes are arranged every 120° along the circumference, each with a 90° or 120° countersunk hole structure, and three screws are screwed into each hole.

2. The method according to claim 1, characterized in that, The modified epoxy resin structural adhesive adopts a gradient formulation: the bottom layer uses a high-toughness formulation with a shear strength ≥25MPa; the middle layer uses a standard formulation with a temperature resistance of -40℃ to 150℃; the top layer uses a high-strength formulation with a curing time of 120 minutes at 120℃; and the bonding strength is not less than 85% of the strength of the parent material.

3. The method of claim 1, wherein, The method further includes the following tests after molding: ultrasonic flaw detection every 5 layers; X-ray inspection after final molding to ensure no internal defects; surface hardness testing, requiring it to reach more than 90% of the raw material; and dynamic balance testing, with the dynamic balance level reaching G2.

5.

4. A method for restoring the shank of a circular broach after it breaks, characterized in that, Includes the following steps: The location and size of the original rear shank fracture were determined by measurement. The outer diameter, roundness and coaxiality of the rear guide were measured using a coordinate measuring machine or precision measuring tools to establish the baseline data. The back guide section of the broach is machined, including: a first rough turning using carbide tools, with a feed rate f≤0.15mm / r, depth of cut ap≤1mm, and cutting speed 80-100m / min, to remove the surface oxide layer; a second finish turning using ceramic tools, with a feed rate f≤0.08mm / r, depth of cut ap≤0.2mm, and cutting speed 120-150m / min, to machine a stepped structure, leaving a finishing allowance of 0.02-0.05mm; the second... The first rear handle is placed in a medium-temperature tempering furnace and heated to 350℃, held for 15-20 minutes, with temperature uniformity controlled within ±5℃. This first rear handle is a custom-made one. Three through-holes are arranged every 120° along the circumference, each with a 90° or 120° countersunk hole structure. Three screws are screwed into the threaded holes for fixation. An elastic compensation structure is designed between the first rear handle and the original rear guide, including three elastic diaphragms evenly distributed at 120°, made of 42C material. rMo alloy steel, hardness HRC32-36; diaphragm thickness precisely controlled at 1.5-2mm, inner and outer end thickness ratio 1.2:1; effective working length 0.4-0.5 times the rear shank diameter; bearing support system including: P4 grade precision double row angular contact ball bearings; bearing preload adjusted by precision nuts, controlled between 5%-8% of dynamic load; bearing housing made of 40Cr quenched and tempered steel integral design; radial clearance controlled at 0.01-0.015mm; Assembly includes: installing elastic diaphragms using a special positioning fixture, with the positions of the elastic diaphragms staggered with the positions of the threaded holes; controlling the circumferential distribution error of the three diaphragms to be ≤0.5°; the perpendicularity of the diaphragms to the connecting surface to be ≤0.02mm; controlling the installation torque to be 20-25 N·m; setting up the bearing system, including: bearing housing bore diameter accuracy requirement of H6 grade; bearing outer ring interference of 0.01-0.02mm; bearing end face perpendicularity to the housing to be ≤0.005mm; and controlling the preload using a special torque wrench.

5. The method of claim 4, wherein, The performance parameters of the elastic diaphragm include: material elastic modulus: 210 GPa; yield strength: ≥835 MPa; fatigue strength: ≥400 MPa; elastic deformation: 0.2-0.3 mm; bearing preload: 2000-3000 N.

6. The method according to claim 4, characterized in that, The restoration insert must meet the following standards: Static test: radial runout ≤ 0.01mm; axial runout ≤ 0.015mm; coaxiality ≤ 0.02mm; angular wobble ≤ 0.1°; Dynamic test: vibration value at operating speed ≤ 0.8mm / s; temperature rise ≤ 15℃; noise value ≤ 75dB.

7. The method according to claim 4, characterized in that, The environmental requirements for assembly include: constant temperature workshop temperature of 20±2℃; relative humidity controlled at 45%-65%; illumination not less than 500 lux; worktable flatness ≤0.05mm / m²; regular inspection of machine tool accuracy to ensure processing stability.

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