Method for restoring precision of bearing test equipment

Abstract

The application discloses a bearing test equipment precision recovery method, comprising the following steps: S1, tool assembly; S2, precision failure determination; S3, allowance calculation; S4, coaxiality reference positioning; S5, grinding treatment is carried out on the main shaft hole and the test unit mounting hole; and S6, precision rechecking. The application solves the problems that after the existing bearing test equipment is used for a long time, the stress release deformation of components leads to the coaxiality of the main shaft seat and the tool seat to be out of tolerance, and the traditional surfacing and the repair mode of additionally installing a bushing have the problems of long cost period and that the newly-added material is easy to be deformed again and affect the test precision after stress release.

Description

Technical Field

[0001] This invention relates to the technical field of bearing testing equipment accuracy recovery methods, specifically a bearing testing equipment accuracy recovery method. Background Technology

[0002] Bearing testing equipment is a core specialized piece of equipment for conducting radial and axial load performance and durability life tests on various bearings. The equipment contains a drive spindle seat and a test unit tooling seat. The coaxiality accuracy of the cylindrical mounting holes of the two directly determines the amount of vibration and the magnitude of eccentric load during the bearing test, which in turn affects the accuracy of the bearing test data and the service life of the test piece.

[0003] The bearing testing equipment base, spindle seat, and tooling seat are all metal cast or forged components. During the long-term reciprocating loading and continuous rotation of the equipment, the residual stress inside the metal will be slowly released, causing slight deformation of the mating plane and cylindrical hole of the spindle seat and tooling seat. As the usage time increases, the cumulative deformation continues to increase, eventually causing the spindle hole of the spindle seat and the mounting hole of the test unit of the tooling seat to be misaligned and the coaxiality to be seriously out of tolerance. When the axes of the two holes are not aligned, the test bearing will continuously bear the periodic eccentric load every time it rotates, causing the equipment to vibrate violently, which in turn leads to the distortion of test data. In severe cases, it can directly damage the bearing under test, forcing the equipment to be shut down for precision repair.

[0004] Currently, the mainstream repair methods in the industry fall into two categories: the first is bushing fitting repair, which involves removing part of the material from the inner wall of the deformed hole, pressing in a metal bushing, and then machining the inner hole of the bushing to the standard size; the second is weld overlay repair, which involves welding metal overlay to fill the gap in the inner wall of the deformed hole, and then boring to restore the nominal hole diameter. Both of these traditional repair methods require the introduction of new dissimilar metal materials such as bushings and weld overlays into the equipment body. However, the newly added metal materials contain unreleased casting and welding residual stresses, which means that after the repair is completed and put into use, the stress of the new materials will gradually be released and deform again, causing the coaxiality accuracy to fail again in a short period of time, requiring repeated shutdowns for rework. At the same time, the weld overlay and bushing insertion processes are cumbersome, requiring multiple separate processing and assembly processes, resulting in long repair cycles, high machining material and labor costs, and significantly reducing the effective operating time of bearing testing equipment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for restoring the accuracy of bearing testing equipment. This method aims to solve the problems of excessive coaxiality between the spindle seat and the tooling seat caused by stress release deformation of components after long-term use of existing bearing testing equipment, as well as the long cost and cycle of traditional repair methods such as overlay welding and adding bushings, and the easy deformation of newly added materials due to subsequent stress release, which affects the test accuracy.

[0006] To achieve the above objectives, the present invention provides a method for restoring the accuracy of bearing testing equipment, comprising the following steps: S1. Install the spindle in the spindle hole of the spindle seat, assemble the rotating end of the spindle with the test unit mounting hole on the tooling seat, install a dial indicator on the rotating end of the spindle and make the probe of the dial indicator contact the inner peripheral wall of the test unit mounting hole; S2. Rotate the spindle to allow a dial indicator to detect the coaxiality difference between the spindle seat and the tool seat. Determine the coaxiality difference. If the coaxiality difference is >0.01mm, it is determined that the coaxiality accuracy of the tool seat and the spindle seat is lost. If the coaxiality difference is ≤0.01mm, it is determined that the coaxiality accuracy of the tool seat and the spindle seat is normal. S3. Based on step S2, if the coaxiality difference is >0.01mm, record the coaxiality difference value and calculate the grinding distance data of the spindle hole and the test unit mounting hole. The grinding distance data of the spindle hole and the test unit mounting hole are both the coaxiality difference value + the safety margin reserved for grinding operation. The safety margin reserved for grinding operation is 1mm. S4. The spindle seat consists of a first seat body and a first cover body, and the tooling seat consists of a second seat body and a second cover body. The spindle seat is disassembled to separate the first seat body from the first cover body, and the tooling seat is disassembled to separate the second seat body from the second cover body. Based on the grinding distance data, the top wall plane of the first seat body, the bottom wall plane of the first cover body, the top wall plane of the second seat body, and the bottom wall plane of the second cover body are respectively subjected to a first grinding process using a CNC milling machine cutter. The first seat body and the first cover body, after the first grinding process, are then fastened together with screws to form the spindle seat. The first seat body and the first cover body, after the first grinding process, are then assembled together. The two seats and the second cover are fastened together with screws to form a tooling seat. The spindle seat and the tooling seat are clamped onto a CNC boring machine. The CNC boring machine processes the outer walls on both sides of the first seat and the outer walls on both sides of the first cover to form cylindrical positioning protrusions of the spindle seat. Two cylindrical positioning protrusions of the spindle seat on the same side combine to form a cylindrical positioning surface of the spindle seat. The CNC boring machine processes the outer walls on both sides of the second seat and the outer walls on both sides of the second cover to form cylindrical positioning protrusions of the tooling seat. Two cylindrical positioning protrusions of the tooling seat on the same side combine to form a cylindrical positioning surface of the tooling seat. S5. Set the initial dimension data, take the cylindrical positioning protrusion of the tooling seat in step S4 as the machining reference, and perform a second grinding process on the spindle hole using the initial dimension data through a CNC boring machine. Take the cylindrical positioning protrusion of the spindle seat after the second grinding process as the machining reference, and perform a third grinding process on the test unit mounting hole using the initial dimension data through a CNC boring machine. S6. After processing in step S5, the spindle seat and tool seat are re-traversed through steps S1 and S2 for re-determination. If the determination fails, steps S3 to S5 are re-traversed.

[0007] The present invention further includes the following features: the CNC milling cutter is a carbide end mill, and the CNC milling machine adopts a layer-by-layer micro-cutting mode with the single milling depth controlled within the range of 0.02mm-0.05mm.

[0008] The present invention further provides that: when collecting the coaxiality value in step S2, the dial indicator is uniformly selected at least 6 points along the circumference of the mounting hole of the test unit to record the dial indicator reading, and the difference between the maximum and minimum values ​​of the dial indicator reading is taken as the final coaxiality difference value.

[0009] The present invention further includes the following: before assembling the spindle and dial indicator in step S1, the outer circle of the spindle and the inner wall of the test unit mounting hole are pre-treated by degreasing, rust removal and burr grinding.

[0010] The advantages of adopting the above technical solution are: the repair process in the above technology only involves cutting and removing the metal from the main spindle seat and the tool seat's own body plane and outer wall. No repair methods such as welding or bushing are used to introduce dissimilar new materials. There is no problem of the stress release of the added material causing the seat to deform again or the coaxiality to exceed the tolerance. The coaxial accuracy of the equipment can be maintained stably for a long time after repair, which greatly reduces the frequency of repeated shutdowns and repairs, and effectively improves the continuous operation time and testing stability of the bearing testing equipment.

[0011] The aforementioned technology employs a standardized coaxiality testing and judgment system. A dedicated testing structure is built by assembling a spindle and a dial indicator. At least six dial indicator readings are collected circumferentially along the mounting holes of the test unit. The difference between the maximum and minimum readings is taken as the true coaxiality deviation, and a quantitative judgment threshold of 0.01 mm is used. This ensures objective testing data with minimal error, accurately distinguishing between qualified and failed equipment states, thus avoiding false positives and false negatives caused by relying on manual experience. Simultaneously, a quantitative grinding allowance calculation rule is established. The measured coaxiality difference is superimposed with a fixed safety allowance of 1 mm as the grinding distance for each mating surface. This ensures complete compensation of the original coaxial offset while mitigating insufficient grinding or machining allowance through the safety allowance. This achieves standardized and controllable grinding dimensions, significantly improving the first-pass yield.

[0012] In the aforementioned technology, the spindle seat is divided into a first seat body and a first cover body, and the tooling seat is divided into a second seat body and a second cover body. The mating surfaces of each component are individually milled and ground to precisely eliminate warping caused by stress deformation of the mating surfaces. The milling employs a carbide end mill with a 0.02-0.05mm layer-by-layer micro-cutting process to avoid localized thermal deformation and stress abrupt changes in the seat body caused by large cutting amounts, ensuring the flatness accuracy of the mating surfaces. After the individual components are ground, the spindle seat and tooling seat are locked together and clamped on a CNC boring machine, where cylindrical positioning protrusions are machined simultaneously. This allows the positioning protrusions on the same side to combine to form a complete cylindrical positioning surface. The entire structure uses the same machining datum, completely solving the defects of inconsistent machining datums and coaxial deviations after repair in traditional separate-component machining methods. This ensures the basic coaxial accuracy of the cylindrical positioning surfaces of the spindle seat and tooling seat from the source of machining.

[0013] The above technology employs a step-by-step precision boring process with mutual references: first, the spindle hole is repaired using the cylindrical positioning protrusion of the tooling seat as a reference, and then the test unit mounting hole is precision bored using the corrected cylindrical positioning protrusion of the spindle seat as a reference. The entire process is strictly processed according to the initial dimensions of the equipment from the factory, thereby accurately restoring the original design assembly dimensions of the equipment, eliminating the periodic eccentric load during the test operation, thereby reducing equipment vibration and ensuring that the test data of various bearing performance are true and accurate.

[0014] The above technology sets up a closed-loop retest and repair process, so that after the finishing is completed, the coaxiality test is re-executed. If the accuracy does not meet the standard, the allowance calculation, plane milling and boring processes can be repeated until the coaxiality meets the usage standard, thereby ensuring the lower limit of repair accuracy.

[0015] In the above-mentioned technology, the outer circle of the spindle and the inner wall of the test unit mounting hole are pretreated by degreasing, derusting and deburring before testing. This removes impurities and protrusions from the hole wall, prevents foreign objects from squeezing the dial indicator probe and interfering with the reading, further reduces the coaxiality detection error and improves the reliability of the accuracy judgment result.

[0016] In summary, compared with traditional welding and bushing repair solutions, this invention eliminates the need for complex processes such as welding, bushing customization, and secondary fitting, significantly shortening the equipment downtime repair cycle. This reduces the costs of welding consumables, bushing accessories, and labor, resulting in good economic benefits. It is also suitable for coaxial accuracy calibration operations of various bearing durability and load performance testing equipment. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the tooling base and spindle base in the deformed state in this invention; Figure 2 This is a three-dimensional view of the tooling base and spindle base in this invention; Figure 3This is a simplified view of the two main spindle bearing cylindrical positioning protrusions in the closed state before the second grinding in this invention; Figure 4 This is a simplified view of the two main spindle bearing cylindrical positioning protrusions in the closed state after the second grinding in this invention. Detailed Implementation

[0018] This invention provides a method for restoring the accuracy of bearing testing equipment, comprising the following steps: S1. Install the spindle in the spindle hole of the spindle seat, assemble the rotating end of the spindle with the test unit mounting hole on the tooling seat, install a dial indicator on the rotating end of the spindle and make the probe of the dial indicator contact the inner peripheral wall of the test unit mounting hole; S2. Rotate the spindle to allow a dial indicator to detect the coaxiality difference between the spindle seat and the tool seat. Determine the coaxiality difference. If the coaxiality difference is >0.01mm, it is determined that the coaxiality accuracy of the tool seat and the spindle seat is lost. If the coaxiality difference is ≤0.01mm, it is determined that the coaxiality accuracy of the tool seat and the spindle seat is normal. S3. Based on step S2, if the coaxiality difference is >0.01mm, record the coaxiality difference value and calculate the grinding distance data of the spindle hole and the test unit mounting hole. The grinding distance data of the spindle hole and the test unit mounting hole are both the coaxiality difference value + the safety margin reserved for grinding operation. The safety margin reserved for grinding operation is 1mm. S4. The spindle seat consists of a first seat body and a first cover body, and the tooling seat consists of a second seat body and a second cover body. The spindle seat is disassembled to separate the first seat body from the first cover body, and the tooling seat is disassembled to separate the second seat body from the second cover body. Based on the grinding distance data, the top wall plane of the first seat body, the bottom wall plane of the first cover body, the top wall plane of the second seat body, and the bottom wall plane of the second cover body are respectively subjected to a first grinding process using a CNC milling machine cutter. The first seat body and the first cover body, after the first grinding process, are then fastened together with screws to form the spindle seat. The first seat body and the first cover body, after the first grinding process, are then assembled together. The two seats and the second cover are fastened together with screws to form a tooling seat. The spindle seat and the tooling seat are clamped onto a CNC boring machine. The CNC boring machine processes the outer walls on both sides of the first seat and the outer walls on both sides of the first cover to form cylindrical positioning protrusions of the spindle seat. Two cylindrical positioning protrusions of the spindle seat on the same side combine to form a cylindrical positioning surface of the spindle seat. The CNC boring machine processes the outer walls on both sides of the second seat and the outer walls on both sides of the second cover to form cylindrical positioning protrusions of the tooling seat. Two cylindrical positioning protrusions of the tooling seat on the same side combine to form a cylindrical positioning surface of the tooling seat. S5. Set the initial dimension data, take the cylindrical positioning protrusion of the tooling seat in step S4 as the machining reference, and perform a second grinding process on the spindle hole using the initial dimension data through a CNC boring machine. Take the cylindrical positioning protrusion of the spindle seat after the second grinding process as the machining reference, and perform a third grinding process on the test unit mounting hole using the initial dimension data through a CNC boring machine. S6. After processing in step S5, the spindle seat and tool seat are re-traversed through steps S1 and S2 for re-determination. If the determination fails, steps S3 to S5 are re-traversed.

[0019] Furthermore, the CNC milling machine uses carbide end mills as the milling cutters, and the CNC milling machine adopts a layer-by-layer micro-cutting mode in its milling and grinding process, with the single milling depth controlled within the range of 0.02mm-0.05mm.

[0020] Further: When collecting the coaxiality value in step S2, the dial indicator is uniformly selected at least 6 points along the circumference of the mounting hole of the test unit to record the dial indicator reading. The difference between the maximum and minimum values ​​of the dial indicator reading is taken as the final coaxiality difference value.

[0021] Furthermore: Before assembling the spindle and dial indicator in step S1, the outer circle of the spindle and the inner wall of the test unit mounting hole are pre-treated by degreasing, rust removal and deburring.

[0022] In the above-described technology, the spindle seat is designated as 1 in the accompanying drawings, the spindle hole is 11, the cylindrical positioning protrusion of the spindle seat is 12, the first seat body is designated as 13, the top wall plane of the first seat body is designated as 131, the first cover body is designated as 14, the bottom wall plane of the first cover body is designated as 141, the cylindrical positioning protrusion of the spindle seat is designated as 15, the tooling seat is designated as 2 in the accompanying drawings, the test unit mounting hole is 21, the cylindrical positioning protrusion of the tooling seat is 22, the second seat body is designated as 23, the top wall plane of the second seat body is designated as 231, the second cover body is designated as 24, the bottom wall plane of the second cover body is designated as 241, and the cylindrical positioning protrusion of the tooling seat is designated as 25.

[0023] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A method for restoring the accuracy of bearing testing equipment, characterized in that: Includes the following steps: S1. Install the spindle in the spindle hole of the spindle seat, assemble the rotating end of the spindle with the test unit mounting hole on the tooling seat, install a dial indicator on the rotating end of the spindle and make the probe of the dial indicator contact the inner peripheral wall of the test unit mounting hole; S2. Rotate the spindle to allow a dial indicator to detect the coaxiality difference between the spindle seat and the tool seat. Determine the coaxiality difference. If the coaxiality difference is >0.01mm, it is determined that the coaxiality accuracy of the tool seat and the spindle seat is lost. If the coaxiality difference is ≤0.01mm, it is determined that the coaxiality accuracy of the tool seat and the spindle seat is normal. S3. Based on step S2, if the coaxiality difference is >0.01mm, record the coaxiality difference value and calculate the grinding distance data of the spindle hole and the test unit mounting hole. The grinding distance data of the spindle hole and the test unit mounting hole are both the coaxiality difference value + the safety margin reserved for grinding operation. The safety margin reserved for grinding operation is 1mm. S4. The spindle seat consists of a first seat body and a first cover body, and the tooling seat consists of a second seat body and a second cover body. The spindle seat is disassembled to separate the first seat body from the first cover body, and the tooling seat is disassembled to separate the second seat body from the second cover body. Based on the grinding distance data, the top wall plane of the first seat body, the bottom wall plane of the first cover body, the top wall plane of the second seat body, and the bottom wall plane of the second cover body are respectively subjected to a first grinding process using a CNC milling machine cutter. The first seat body and the first cover body, after the first grinding process, are then fastened together with screws to form the spindle seat. The first seat body and the first cover body, after the first grinding process, are then assembled together. The two seats and the second cover are fastened together with screws to form a tooling seat. The spindle seat and the tooling seat are clamped onto a CNC boring machine. The CNC boring machine processes the outer walls on both sides of the first seat and the outer walls on both sides of the first cover to form cylindrical positioning protrusions of the spindle seat. Two cylindrical positioning protrusions of the spindle seat on the same side combine to form a cylindrical positioning surface of the spindle seat. The CNC boring machine processes the outer walls on both sides of the second seat and the outer walls on both sides of the second cover to form cylindrical positioning protrusions of the tooling seat. Two cylindrical positioning protrusions of the tooling seat on the same side combine to form a cylindrical positioning surface of the tooling seat. S5. Set the initial dimension data, take the cylindrical positioning protrusion of the tooling seat in step S4 as the machining reference, and perform a second grinding process on the spindle hole using the initial dimension data through a CNC boring machine. Take the cylindrical positioning protrusion of the spindle seat after the second grinding process as the machining reference, and perform a third grinding process on the test unit mounting hole using the initial dimension data through a CNC boring machine. S6. After processing in step S5, the spindle seat and tool seat are re-traversed through steps S1 and S2 for re-determination. If the determination fails, steps S3 to S5 are re-traversed.

2. The method for restoring the accuracy of a bearing testing equipment according to claim 1, characterized in that: The CNC milling machine uses carbide end mills as the milling cutters. The milling and regrinding mode of the CNC milling machine adopts a layer-by-layer micro-cutting mode, and the single milling depth is controlled within the range of 0.02mm-0.05mm.

3. The method for restoring the accuracy of a bearing testing equipment according to claim 1, characterized in that: In step S2, when collecting coaxiality values, the dial indicator is used to uniformly select at least 6 points along the circumference of the mounting hole of the test unit to record the dial indicator readings. The difference between the maximum and minimum values ​​of the dial indicator readings is taken as the final coaxiality difference value.

4. The method for restoring the accuracy of a bearing testing equipment according to claim 1, characterized in that: Before assembling the spindle and dial indicator in step S1, the outer circle of the spindle and the inner wall of the test unit mounting hole are pre-treated by degreasing, rust removal and burr grinding.

Images