A method for quickly determining fixture factors of gearbox shell bearing hole roundness out-of-tolerance

Abstract

This application discloses a rapid method for determining fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings, relating to the field of machining error diagnosis technology. The method includes: positioning and clamping the gearbox housing blank to be machined and performing machining; maintaining the workpiece in a closed clamping state to obtain hole diameter data at a specified cross-section and calculating a first roundness parameter; releasing the constraint and allowing it to stand still, obtaining hole diameter data at the same cross-section and calculating a second roundness parameter; comparing the two roundness parameters with the design roundness tolerance threshold; and, based on the compliance status of the first and second roundness parameters, and the comparison result of their difference with the deformation threshold, determining and outputting diagnostic results for single fixture-related causes, single machine tool faults, or coupled faults between the machine tool and fixture. This invention utilizes physical measurement comparison of the same workpiece under different stress states to decouple inherent errors from fixture clamping deformation errors, avoiding blind trial cutting for troubleshooting and improving the accuracy and efficiency of fault cause localization.

Description

Technical Field

[0001] This application relates to the field of machining error diagnosis technology, and in particular to a method for rapid determination of fixture factors when the roundness of bearing holes in a gearbox housing exceeds the tolerance. Background Technology

[0002] In the machining process of automotive gearbox housings, the machining accuracy of bearing holes directly affects the assembly quality of the gearbox. When bearing hole roundness deviations occur, since the machining system contains multiple actuators, the existing troubleshooting methods usually involve measuring the workpiece in a single state after unloading. This only obtains the final error result and makes it difficult to distinguish whether the error originates from inherent machining defects of the machine tool, such as the accuracy of the machine tool spindle's running trajectory, or from elastic deformation of the workpiece caused by the constraint force applied by the fixture. Machine tool factors and fixture factors are confused with each other, making it impossible to decouple and diagnose the source of error at the physical level.

[0003] Faced with mixed errors that are difficult to distinguish, the processing site lacks diagnostic logic based on data for direct judgment. Technicians often rely on manual experience to blindly adjust machine tool operating parameters or fixture support status, and use repeated stop-and-test cuts to verify the adjustment results. This makes it impossible to accurately separate simple fixture-induced or inherent errors, and also impossible to determine whether the two are coupled and interfered with each other, resulting in long troubleshooting cycles and low processing efficiency.

[0004] Existing inspection procedures lack standardization in extracting deviation data, affecting the reliability of diagnostic criteria. In actual measurements, the effects of measurement reference conversion and spatial phase shift are ignored. Changing measuring tools or inconsistent measurement sections can introduce secondary errors. Moreover, conventional operations do not consider the residual cutting thermal deformation of the workpiece after machining and the mechanical elastic recovery process in the initial stage of unloading. Measurements are performed directly without static treatment, resulting in distorted hole diameter data that cannot reflect deformation caused by clamping factors, thus reducing the accuracy of the final judgment. Summary of the Invention

[0005] The purpose of this invention is to provide a method for rapid determination of fixture factors in the roundness tolerance of bearing holes in gearbox housings. This method addresses at least one technical problem in the existing process of troubleshooting the roundness tolerance of bearing holes in gearbox housings: the inherent error and fixture clamping deformation are confused and difficult to decouple, the reliance on manual trial cutting leads to long processing cycles, and the data distortion caused by non-standard measurement operations affects the accuracy of diagnosis.

[0006] This invention provides a method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings, comprising the following steps:

[0007] Position and clamp the gearbox housing blank to be processed according to the clamping parameters;

[0008] The machining process is performed to complete the machining of the specified bearing holes on the gearbox housing blank, thereby generating the gearbox housing workpiece;

[0009] Maintaining the closed clamping state of the gearbox housing workpiece, acquiring first hole diameter data in multiple directions at a designated axial section of the designated bearing hole, and calculating a first roundness parameter based on the first hole diameter data;

[0010] Release the constraints on the gearbox housing workpiece and let it stand still. Obtain second hole diameter data in multiple directions at the same axial section of the designated bearing hole, and calculate the second roundness parameter based on the second hole diameter data.

[0011] The first roundness parameter is compared with the preset design roundness tolerance threshold, and the second roundness parameter is compared with the design roundness tolerance threshold.

[0012] When the first roundness parameter meets the design roundness tolerance threshold and the second roundness parameter exceeds the design roundness tolerance threshold, the output indicates that the fixture factor is the single cause of the gearbox housing bearing hole roundness deviation.

[0013] When the first roundness parameter exceeds the design roundness tolerance threshold, a second diagnostic result indicating that the machining system has an inherent error is output, and the difference between the first roundness parameter and the second roundness parameter is calculated. If the difference exceeds a preset deformation threshold, a coupling fault diagnostic result indicating that there is a fault cause of coupling between the machine tool and the fixture is output.

[0014] Furthermore, the steps of positioning and clamping the gearbox housing blank to be machined according to the clamping parameters, and performing machining operations to complete the machining of the specified bearing holes on the gearbox housing blank specifically include:

[0015] The gearbox housing blank is placed in the clamping mechanism of the processing equipment to complete the reference positioning of the gearbox housing blank;

[0016] The clamping mechanism is triggered according to the set clamping parameters to apply an external constraint force to the gearbox housing blank to complete the closed clamping.

[0017] The preset machine tool operating parameters and cutting tool parameters are called, wherein the preset machine tool operating parameters include spindle speed, feed rate and depth of cut to ensure consistency between machining cutting force and cutting heat.

[0018] The spindle of the control processing equipment drives the cutting tool to rotate, and cuts the gearbox housing blank at a predetermined position according to the set processing trajectory and feed rate to form the designated bearing hole.

[0019] Furthermore, the specific methods for calculating the first roundness parameter based on the first aperture data and the second roundness parameter based on the second aperture data are as follows:

[0020] The maximum and minimum pore diameter values ​​are selected from the first pore diameter data, and half of the difference between the maximum pore diameter value selected from the first pore diameter data and the minimum pore diameter value selected from the first pore diameter data is used as the first roundness parameter.

[0021] The maximum and minimum pore diameter values ​​are selected from the second pore diameter data, and half of the difference between the maximum and minimum pore diameter values ​​selected from the second pore diameter data is used as the second roundness parameter.

[0022] Furthermore, the steps of obtaining first bore diameter data in multiple directions at a specified axial section of the specified bearing bore, and obtaining second bore diameter data in multiple directions at the same axial section of the specified bearing bore, specifically include:

[0023] Using the same inner diameter measuring tool, position it to the specified axial section of the specified bearing hole;

[0024] Using the theoretical axis of the specified bearing hole as a reference, the measurement direction is selected on the circumference according to the evenly divided angle, and the first hole diameter data is obtained in sequence.

[0025] After the constraints are released, the reference hole or locating pin groove carried by the gearbox housing workpiece itself is used as a spatial phase reference to calibrate the starting zero-degree angle of the measurement. The same measurement position and measurement direction are maintained as when the first hole diameter data is obtained, and the same inner diameter measuring tool is used to obtain the second hole diameter data.

[0026] Furthermore, the specific implementation method for maintaining the closed clamping state of the gearbox housing workpiece is as follows:

[0027] After the machining process is completed, the motion control circuit of the clamping mechanism used to maintain the closed clamping state is locked, and no release or unloading command is sent to the clamping mechanism.

[0028] The clamping force and auxiliary support force applied to the gearbox housing workpiece should be consistent in magnitude, point of application, and direction of application as during the machining process.

[0029] Furthermore, the specific implementation method for releasing the constraint on the gearbox housing workpiece and allowing it to settle is as follows:

[0030] The clamping mechanism that controls and maintains the closed clamping state removes all physical constraints on the gearbox housing workpiece and moves the gearbox housing workpiece to a horizontal testing platform free from external interference.

[0031] The gearbox housing workpiece is left to stand still for a preset time under its own weight only. The preset time is the time required to ensure that the microscopic thermal deformation caused by cutting heat and the mechanical elastic recovery after the fixture is removed are fully released.

[0032] Further, the step of calculating the difference between the first roundness parameter and the second roundness parameter, and outputting a coupling fault diagnosis result indicating the presence of a fault cause of machine tool and fixture coupling if the difference exceeds a preset deformation threshold, specifically includes:

[0033] Calculate the absolute value of the difference between the second roundness parameter and the first roundness parameter, and define the absolute value as the deformation deviation parameter;

[0034] The deformation deviation parameter is numerically compared with the deformation threshold.

[0035] When the deformation deviation parameter is greater than the deformation threshold, the coupling fault diagnosis result is output;

[0036] When the deformation deviation parameter is less than or equal to the deformation threshold, a single fault diagnosis result is output, indicating that only a single equipment repair is needed for the machine tool spindle, tool wear, or bearing clearance.

[0037] Furthermore, the preset deformation threshold is the allowable deformation used to evaluate the rationality of clamping, and the preset deformation threshold can be obtained in any of the following ways:

[0038] The preset proportional value of the preset design roundness tolerance threshold is directly converted into the deformation threshold, wherein the preset proportional value is a proportion used to limit the allowable deformation fluctuation range of thin-walled parts;

[0039] The theoretical springback deformation of the bearing hole section of the gearbox housing workpiece under the nominal clamping force is extracted using finite element analysis, and the theoretical springback deformation is used as the deformation threshold.

[0040] Furthermore, the specific indications of the single precipitating factor indicated by the first diagnostic result include:

[0041] The clamping force applied by the clamping actuator exceeds the limit, the support point arrangement of the fixture deviates from the rigid node inside the gearbox housing workpiece to generate a suspended bending moment, or there are impurities on the positioning reference surface of the fixture causing unbalanced extrusion stress.

[0042] Furthermore, the preset design roundness tolerance threshold is an allowable error value set according to the hole tolerance accuracy grade of the target bearing hole;

[0043] The method further includes:

[0044] When the first roundness parameter is less than or equal to the preset design roundness tolerance threshold, and the second roundness parameter is less than or equal to the preset design roundness tolerance threshold, a normal machining result is output. The normal machining result indicates that the roundness of the bearing hole of the current workpiece meets the design requirements, and the diagnostic process ends.

[0045] The above solution achieves the following beneficial technical effects:

[0046] This invention separates inherent machining errors of the machine tool from fixture deformation errors by acquiring hole diameter data and calculating roundness parameters when the workpiece is in a closed clamped state and in a free and stationary state. The first roundness parameter in the clamped state directly reflects the machine tool spindle running trajectory and tool state, while the second roundness parameter after the constraint is released superimposed the mechanical elastic recovery deformation of the workpiece after losing external constraint. By comparing physical measurements of the same workpiece under two different stress states, the problem of confusion between machine tool factors and fixture factors in traditional troubleshooting is avoided, and the physical level decoupling of error sources is achieved.

[0047] This invention constructs a diagnostic logic based on multi-level threshold comparison to directly output fault judgment results. By comparing the roundness parameters calculated twice with the design roundness tolerance threshold, and further comparing the magnitude relationship between the deformation deviation parameter and the deformation threshold under the premise that the first roundness parameter exceeds the tolerance, it can accurately distinguish and output complex faults such as simple fixture-induced faults, simple inherent errors, and combined faults of machine tool errors and fixture deformation coupling interference. This replaces the traditional troubleshooting process of blindly adjusting based on manual experience and repeatedly stopping the machine for trial cutting, thus shortening the abnormality handling cycle.

[0048] This invention standardizes the measurement operation steps and environmental conditions, improving the data reliability of diagnostic judgment. By limiting the use of the same inner diameter measuring tool and positioning the same axial section before and after constraint removal, and relying on the workpiece's built-in reference hole as a spatial phase reference to calibrate the measurement starting angle, it eliminates secondary errors caused by measuring tool conversion and measurement position offset. At the same time, combined with the preset static time after the workpiece is freed from constraints, it ensures that the workpiece fully releases cutting thermal deformation and mechanical elastic recovery without external force interference, ensuring that the extracted deviation data truly reflects clamping factors and guaranteeing the objectivity and accuracy of the final diagnostic results. Attached Figure Description

[0049] Figure 1 This is a block diagram of the overall module architecture of the determination system of this invention.

[0050] Figure 2 This is the overall execution flowchart of the determination method of the present invention. Detailed Implementation

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] See attached document Figure 1 This invention provides a rapid determination system for fixture factors causing out-of-tolerance bearing hole roundness in gearbox housings. The system includes: a trial machining module, a clamping detection module, a loosening detection module, and a determination module.

[0053] The trial machining module acquires the gearbox housing blank to be processed. The trial machining module controls the machining equipment to position and clamp the gearbox housing blank according to the clamping parameters set by the production line. The trial machining module calls the preset machine tool speed parameters and cutting tool parameters to execute the cutting process. The trial machining module completes the machining process of the specified bearing hole on the gearbox housing blank and generates the gearbox housing workpiece.

[0054] After the machining process is completed, the clamping detection module maintains the fixture mechanism in the current closed clamping state. The clamping detection module ensures that the clamping parameters and force state of the gearbox housing workpiece do not change. The clamping detection module obtains first hole diameter data in multiple directions at a specified axial section of the bearing hole. The clamping detection module calculates the first roundness parameter of the bearing hole based on the obtained first hole diameter data.

[0055] After the clamping detection module records the first roundness parameter, the releasing detection module executes the operation procedure of releasing the clamp. The releasing detection module controls the clamping mechanism to release the constraint on the gearbox housing workpiece. The releasing detection module confirms that the gearbox housing workpiece is placed on a horizontal detection platform without external force interference. The releasing detection module uses the same inner diameter measuring tool to obtain the second hole diameter data in multiple directions at the same axial section of the bearing hole. The releasing detection module calculates the second roundness parameter of the bearing hole based on the second hole diameter data.

[0056] The judgment module receives the first roundness parameter output by the clamping detection module and the second roundness parameter output by the loosening detection module. The judgment module compares and analyzes the first roundness parameter with the design roundness tolerance, and the judgment module compares and analyzes the second roundness parameter with the design roundness tolerance.

[0057] When the judgment module determines that the first roundness parameter meets the design roundness tolerance and the second roundness parameter exceeds the design roundness tolerance, the judgment module outputs the first diagnostic result. The first diagnostic result indicates that the fixture factor is the single cause of the out-of-tolerance roundness of the gearbox housing bearing hole.

[0058] When the judgment module determines that the first roundness parameter exceeds the design roundness tolerance, the judgment module outputs a second diagnostic result. The second diagnostic result indicates that there is an inherent error in the machining system. Furthermore, the judgment module further calculates the difference between the first roundness parameter and the second roundness parameter for decoupling analysis. If the difference exceeds the preset deformation threshold, it indicates that there is a fault cause of coupling between the machine tool and the fixture.

[0059] When the judgment module determines that both the first roundness parameter and the second roundness parameter meet the design roundness tolerance, the judgment module outputs the normal machining result, and the system ends the current judgment process.

[0060] See attached document Figure 2 This invention provides a method for rapid determination of fixture factors causing out-of-tolerance bearing bore roundness in gearbox housings, comprising the following steps:

[0061] Obtain the gearbox housing blank to be processed, and position and clamp the gearbox housing blank according to the set clamping parameters;

[0062] The machine tool speed parameters and cutting tool parameters are called to execute the cutting process, complete the machining of the specified bearing hole on the gearbox housing blank, and generate the gearbox housing workpiece;

[0063] After processing, maintain the fixture mechanism in its current closed clamping state to ensure that the clamping parameters and force state of the gearbox housing workpiece remain unchanged;

[0064] Obtain first bore diameter data in multiple directions at a specified axial section of the bearing bore, and calculate the first roundness parameter of the bearing bore based on the first bore diameter data;

[0065] Release the clamping mechanism from the gearbox housing workpiece, place the gearbox housing workpiece on a horizontal testing platform and keep it in a state free from external interference;

[0066] The same measuring tool is used to obtain second bore diameter data in multiple directions at the same axial section of the bearing bore, and the second roundness parameter of the bearing bore is calculated based on the second bore diameter data;

[0067] Compare the first roundness parameter with the design roundness tolerance, and compare the second roundness parameter with the design roundness tolerance;

[0068] When the first roundness parameter meets the design roundness tolerance and the second roundness parameter exceeds the design roundness tolerance, the first diagnostic result is output. The first diagnostic result indicates that the fixture factor is the single cause of the out-of-tolerance roundness of the gearbox housing bearing hole.

[0069] When the first roundness parameter exceeds the design roundness tolerance, the second diagnostic result is output. The second diagnostic result indicates that there is an inherent error in the machining system. After the second diagnostic result is output, the difference between the first roundness parameter and the second roundness parameter is calculated for decoupling analysis. If the difference exceeds the preset deformation threshold, it indicates that there is a fault cause of coupling between the machine tool and the fixture.

[0070] When both the first roundness parameter and the second roundness parameter meet the design roundness tolerance, the machining result is output as normal, and the diagnostic process ends.

[0071] The specific steps for obtaining the gearbox housing blank to be processed and positioning and clamping it according to the set clamping parameters include:

[0072] Obtain the gearbox housing blank to be processed, and determine the material and structural properties of the housing blank. The gearbox housing blank belongs to the basic parts of the housing category. The materials of the gearbox housing blank include aluminum alloy, cast iron and cast steel. In terms of structural morphology, the gearbox housing blank contains a thin-walled shell structure with a wall thickness of less than or equal to 4 mm. From the perspective of mechanical principles, when the external clamping constraint force is applied to the shell with the thin-walled structure, stress will be generated inside the shell material and a small amount of elastic deformation will occur. This elastic deformation will naturally recover after the external constraint force is unloaded. This physical phenomenon is the basis for this method to isolate and determine the influence factors of the fixture by comparing different stress states.

[0073] The gearbox housing blank is placed in the fixture mechanism of the machining equipment to complete the workpiece's datum positioning. According to standard process requirements, the locating pins and support surfaces of the fixture mechanism are mechanically fitted with the locating datum holes and datum surfaces of the gearbox housing blank. For the specific positioning structure that uses a machine tool-specific fixture to restrict spatial freedom, those skilled in the art can perform conventional design and adjustment based on the drawings of the part to be machined; this is well-known technology in the field and will not be elaborated upon here.

[0074] The clamping mechanism's actuators are triggered according to the set clamping parameters to apply external constraint forces to the gearbox housing blank, completing the closed clamping. The set clamping parameters are the standard process parameters used in mass production on the current production line. These parameters include the clamping force of the hydraulic or pneumatic pressure foot, the stroke of the auxiliary support components, and the timing of the clamping actions. In this step, the clamping mechanism applies the rated clamping and supporting forces fully to the gearbox housing blank, fixing it at the machining station. Using unaltered conventional clamping parameters ensures that the actual boundary conditions and stress state are replicated when roundness deviations occur during mass production, avoiding interference with subsequent determination of the cause of deviations due to manual changes in pressure variables.

[0075] After the gearbox housing blank is positioned and clamped, the cutting process is executed by calling the preset machine tool speed parameters and cutting tool parameters to complete the machining of the specified bearing holes on the gearbox housing blank and generate the gearbox housing workpiece. The specific steps include:

[0076] The machine tool operating parameters and cutting tool parameters are retrieved from the control system of the machining equipment. The machine tool operating parameters specifically include spindle speed, feed rate, and depth of cut. For example, in a specific machining scenario, the machine tool spindle speed is set to 2400 r / min. The cutting tool parameters include the tool material, model, and geometric dimensions. In a specific implementation scenario, a polycrystalline diamond (PCD) boring bar is used. In this step, the machine tool operating parameters and cutting tool parameters retrieved are the original standard process parameters of the production line. Maintaining the original cutting parameters aims to ensure the consistency of machining cutting force and cutting heat, thereby recreating the actual machining environment when a roundness deviation fault occurs.

[0077] The spindle of the control machining equipment drives the cutting tool to rotate and cut at predetermined positions on the gearbox housing blank according to the set machining trajectory and feed rate. During the cutting operation, the cutting tool removes excess material from the surface of the blank to form bearing holes. The specific interpolation instructions, tool path planning, and cutting fluid supply methods for hole machining on CNC machine tools can be conventionally programmed and set by those skilled in the art according to the drawing requirements and machine tool operating specifications; these are well-known technologies in the field and will not be elaborated upon here.

[0078] The machine tool detects the completion status of the cutting operation, stops the machine spindle feed, and returns the cutting tool to its initial safe origin position. At this point, the target bearing hole on the gearbox housing blank has been machined and formed, becoming the gearbox housing workpiece. From the perspective of machining principles, under the current force-bearing clamping state, because the constraint force of the fixture has not been removed, the stress deformation state inside the gearbox housing workpiece is solidified and maintained. The actual physical shape of the bearing hole wall, which has just been cut and formed, corresponds to the rotational motion trajectory of the machining equipment spindle and the cutting tool. This forming state provides a comparison benchmark for the inherent errors of the subsequent separation machining system and the deformation errors of the fixture.

[0079] After machining, the steps to maintain the fixture mechanism in its current closed clamping state and ensure that the clamping parameters and force state of the gearbox housing workpiece remain unchanged include:

[0080] After confirming that the machine tool spindle has completely stopped feeding and the cutting tool has returned to its safe origin position, the motion control circuit of the clamping mechanism is locked. During this operation, neither the operating system nor manual operation sends release or unloading commands to the clamping system. Implementation methods for the locking control circuit include maintaining the current operating position of the solenoid directional valve in the hydraulic or pneumatic clamping system, or maintaining the self-locking state of the mechanical linkage clamp to prevent displacement or retraction of the clamping components. For the specific hardware implementation of hydraulic system pressure holding or pneumatic circuit locking, those skilled in the art can use conventional pressure holding valves or hydraulically controlled check valves for circuit design, which are well-known technologies in the field and will not be elaborated upon here.

[0081] Maintaining the system's pressure output level ensures that the clamping force and auxiliary support force applied by the actuator to the gearbox housing workpiece, along with their magnitude, point of application, and direction of application, are consistent with those applied during the machining cutting process. Because the gearbox housing workpiece has a thin-walled structure, it undergoes elastic deformation when subjected to external constraints from the fixture. By maintaining the current closed clamping state, the internal force distribution and stress concentration within the workpiece are continuously and physically solidified, preventing elastic recovery of the workpiece material due to the removal of external force.

[0082] A benchmark detection environment is constructed to reflect the actual cutting trajectory of the tool. Under the condition of maintaining clamping constraints and preventing elastic stress release, the inner wall contour shape of the machined bearing hole objectively reflects the actual rotational accuracy of the machine tool spindle, the tool wear condition, and the rigidity characteristics of the machining system. From the perspective of mechanical cutting principles, with the workpiece position fixed, the cutting tool rotates within the hole to machine an envelope surface. As long as the rotational trajectory of the machine tool spindle is circular, the cross-section of the bearing hole machined under the current stress state must be circular. The dimensional characteristics measured at this time are directly equivalent to the machining accuracy of the machine tool system, completely eliminating the dimensional changes caused by unloading deformation. Establishing this stress-constrained detection environment, by maintaining the stress state and isolating the dimensional changes caused by deformation recovery, provides a reliable physical comparison control group for subsequent decoupling and distinguishing between the inherent errors of the machining system and the clamping causes.

[0083] The steps of obtaining first bore diameter data in multiple directions at a specified axial section of the bearing bore, and calculating the first roundness parameter of the bearing bore based on the first bore diameter data, specifically include:

[0084] Determine the specified axial section of the bearing bore to be measured and select a matching internal diameter measuring tool. Considering the structural interference that may exist at both ends of the bearing bore due to chamfered edges at the bore opening or undercut grooves at the bottom, select the radial plane located at the midpoint of the bearing bore's axial depth (e.g., halfway through the bore depth) as the specified axial section. Using a section located at the midpoint can objectively reflect the overall machining quality of the bore wall. The internal diameter measuring tool can be an internal diameter gauge, internal micrometer, or a contact measuring probe integrated into the machine tool spindle. The specific zeroing and calibration process of the measuring tool can be performed by those skilled in the art according to conventional operating procedures, which are well-known techniques in the field and will not be elaborated here.

[0085] Multiple sets of measurements are uniformly acquired along the circumference within a specified axial section using an internal diameter measuring tool. In actual measurement operations, the operator or measurement program uses the theoretical axis of the bearing hole as a reference and selects measurement directions at equally spaced angles on the circumference of the section. For example, two-point diameter measurements are performed sequentially in the horizontal 0°, 45°, vertical 90°, and 135° directions to obtain the first hole diameter data in four directions. This set of diameter values ​​measured under the condition of workpiece clamping constitutes the first hole diameter data set, which is used for subsequent extraction of extreme values.

[0086] From a geometric measurement perspective, the strictly defined roundness error is the difference between the radii of two concentric circles enclosing the actual profile. In practical engineering, when a gearbox thin-walled housing is subjected to clamping forces from both sides of a fixture, the deformation of its bearing holes typically exhibits an approximately elliptical, symmetrical distribution. Based on this deformation characteristic, half the difference between the maximum and minimum diameters measured using the two-point method can highly approximate and quickly quantify the magnitude of the roundness error. Therefore, the maximum and minimum hole diameter values ​​are selected from multiple recorded first hole diameter data, and half the difference between the maximum and minimum hole diameter values ​​is calculated. This calculated result is defined as the first roundness parameter under the current clamping condition. The formula for calculating the first roundness parameter is:

[0087] ;

[0088] In the formula, This represents the first roundness parameter, in mm; This represents the maximum diameter value in the first aperture data measured under clamping conditions, in mm. This represents the minimum diameter value in the first hole diameter data measured under clamping conditions, in mm. The first roundness parameter is quantified using this formula, characterizing the degree of deviation of the target bearing hole cross-sectional profile from a perfect circle when the gearbox housing workpiece maintains machining clamping constraints.

[0089] The specific steps for releasing the clamping mechanism from the gearbox housing workpiece and placing the gearbox housing workpiece on a horizontal testing platform while maintaining a state free from external interference include:

[0090] A release command is sent to the motion control circuit of the clamping mechanism to control the clamping mechanism to remove all physical constraints on the gearbox housing workpiece. Specific implementation methods include controlling the hydraulic or pneumatic pressure foot to return to the release origin position and removing all auxiliary support components and locating pins. From the perspective of materials mechanics principles, the removal of the external clamping force directly changes the force boundary conditions of the workpiece. With the disappearance of external mechanical constraints, the internal elastic stress accumulated in the gearbox housing workpiece, especially in thin-walled areas, during machining and clamping is released, and the material undergoes spontaneous elastic deformation recovery. Since the bearing hole is machined into a perfect circle under clamping pressure, once the constraint is removed and elastic recovery occurs, the original perfect circle hole wall will undergo radial displacement as the material rebounds, and the overall geometry will physically distort towards a natural stress-free state and evolve into a non-circular shape.

[0091] The gearbox housing workpiece, after being released from constraints, is removed from the machining workpiece of the processing equipment and placed stably on a horizontal inspection platform. A lower-level embodiment of the horizontal inspection platform uses a granite / marble inspection platform with a precision of 00 grade or a cast iron measurement reference platform. This high-precision platform provides a physical reference surface with extremely high flatness for subsequent dimensional measurements of the workpiece. Specific operational procedures for workpiece transfer, lifting, or manual handling can be followed by those skilled in the art according to the standard material flow procedures for precision parts in a workshop; these are well-known techniques in the field and will not be elaborated upon here.

[0092] To establish a stress-free state for the gearbox housing workpiece, it is allowed to settle until it reaches a deformation steady state. On a horizontal testing platform, the gearbox housing workpiece is held in place solely by its own weight. The use of any clamps, blocks, or fixtures to apply new fixing forces or lateral thrusts to the gearbox housing workpiece is strictly prohibited, while ensuring the testing environment is free from significant mechanical vibration interference. In actual measurement operations, the settling process specifically involves allowing the gearbox housing workpiece to cool naturally at room temperature and remain stationary for a predetermined period, such as 15 to 30 minutes, to ensure that the microscopic thermal deformation caused by cutting heat and the mechanical elastic recovery after fixture removal are fully released. Establishing this stress-free state is crucial for isolating error variables. After eliminating all non-gravitational external physical constraints and allowing sufficient settling, the deformation process of the bearing hole caused by fixture unloading completely terminates and reaches its final steady state. At this point, the geometry of the bearing hole fully encompasses the cross-sectional profile distortion caused by elastic recovery, providing an accurate test object for subsequent extraction of deformation errors caused by the fixture.

[0093] The steps for obtaining second hole diameter data in multiple directions from the same cross-section of the bearing hole and calculating the second roundness parameter, under the condition that the gearbox housing workpiece is on a horizontal inspection platform and there is no external force interference, specifically include:

[0094] Select the same internal diameter measuring tool used during measurement in the closed clamping state and position it at the same specified axial section of the bearing bore being measured. To ensure strict data comparability, the original measuring tool used to extract the first bore diameter data should be used, such as the same internal diameter gauge or micrometer. During the secondary measurement positioning, use a height gauge, gauge blocks, or an internal diameter measuring fixture with a depth limit ring, with the machined flat end face of the gearbox housing as the Z-axis positioning reference, thereby ensuring that the probe depth of the current measuring tool is strictly consistent with the axial depth measured on the machine tool. The physical significance of maintaining consistency between the measuring tool and the measurement depth is to eliminate systematic measurement errors introduced by changing measuring equipment or offset of the measuring section, ensuring a unified inspection reference.

[0095] The internal diameter measuring tool is used to acquire multiple sets of measurements along the circumferential direction within a specified axial section. In actual measurement operations, the measurement position and direction are strictly maintained identical to those used during the acquisition of the first bore diameter data. Since the workpiece has now detached from the machine tool fixture's positioning coordinate system, the operator or measurement program needs to rely on the reference hole or positioning pin groove inherent in the gearbox housing workpiece itself as a spatial phase reference to recalibrate the starting zero-degree angle of the measurement circumference. After aligning the reference, two-point diameter measurements are sequentially performed in the horizontal 0-degree, 45-degree, vertical 90-degree, and 135-degree directions of the section to obtain the second bore diameter data in the corresponding directions. For the specific readings and data recording operations of the internal diameter measuring tool on the free-state workpiece, those skilled in the art can follow conventional geometric precision inspection specifications, which are well-known techniques in the field and will not be elaborated upon here. After this step, a second bore diameter data set is obtained. Since the workpiece has released its internal elastic stress and reached a deformation steady state, this data set accurately records the geometric contour of the bore wall affected by deformation after the workpiece is naturally unloaded.

[0096] The extreme values ​​are obtained by comparing the values ​​in the second aperture data set, and then substituted into the calculation model to derive the second roundness parameter. The maximum and minimum aperture values ​​are selected from the recorded multiple second aperture data sets. Based on the same geometric measurement principle and engineering approximation algorithm for form and position tolerance evaluation as described above, half of the difference between the maximum and minimum aperture values ​​is calculated, and this result is defined as the second roundness parameter under the current interference-free state. The formula for calculating the second roundness parameter is:

[0097] ;

[0098] In the formula, This represents the second roundness parameter, in mm; This represents the maximum diameter value in the second aperture data measured under conditions of no external force interference, in mm; This represents the minimum diameter value in the second aperture data measured under conditions of no external force interference, expressed in mm. The second roundness parameter is quantified using this formula, characterizing the actual error degree of deviation of the target bearing hole cross-sectional profile from an ideal circle after all external mechanical constraints are removed and elastic recovery is achieved in the gearbox housing workpiece.

[0099] The steps of comparing the calculated first roundness parameter and second roundness parameter with the preset design roundness tolerance threshold to determine whether the roundness characteristics of the gearbox housing workpiece are qualified under different physical conditions specifically include:

[0100] Extract the design roundness tolerance threshold of the target bearing hole from the engineering drawings or 3D digital model process documents of the gearbox housing parts. In the principles of machining and assembly, the roundness tolerance of the bearing hole is set according to the accuracy grade of the bearing it is assembled with and the required operating speed. For example, for the drive shaft bearing hole of a conventional gearbox, referring to the hole tolerance accuracy grades IT6 to IT7 in the national standard, its design roundness tolerance threshold is usually determined to be between 0.010 mm and 0.020 mm. Here, the specific tolerance value extracted is defined as the design roundness tolerance threshold.

[0101] The first roundness parameter obtained under the clamped state is numerically compared with the design roundness tolerance threshold. In the principle of mechanical cutting, when the workpiece is maintained in a closed clamped state without unloading and springback, the measured hole wall profile directly reproduces the actual rotation trajectory of the machine tool spindle. The specific comparison and judgment logic is as follows:

[0102] If the following relationship is satisfied:

[0103] ;

[0104] Then, the first roundness of the gearbox housing workpiece under the closed clamping state is deemed acceptable. Where, This represents the first roundness parameter, in mm; This indicates the design roundness tolerance threshold, in mm. The result shows that the rotational accuracy of the machine tool spindle and the cutting trajectory of the tool meet the theoretical requirements of the drawings, and the machining system has no inherent static or dynamic deviations.

[0105] Conversely, if the following relationship is satisfied:

[0106] ;

[0107] If the first roundness of the gearbox housing workpiece is found to be unqualified under the closed clamping state, it is determined that the workpiece is not qualified. Since the fixture has not yet been released at this time, the interference of elastic deformation recovery is eliminated. This result directly reflects that there is an inherent error in the machining system itself that exceeds the tolerance range. Specific causes usually include equipment-level failures such as excessive radial runout of the machine tool spindle, severe tool wear, or damage to the spindle bearing.

[0108] The second roundness parameter obtained under the condition of no external force interference is numerically compared with the same design roundness tolerance threshold. Under this condition, the elastic stress accumulated inside the workpiece has been completely released, and the cross-sectional shape has undergone actual physical distortion. The specific comparison and judgment logic is as follows:

[0109] If the following relationship is satisfied:

[0110] ;

[0111] The second roundness of the gearbox housing workpiece is then deemed acceptable after the constraints are removed and the internal stress is released. Where, This represents the second roundness parameter, in mm; This indicates the design roundness tolerance threshold, in mm. This means that although the clamping force applied by the fixture causes a small deformation, the dimensional change after deformation recovery is still within the tolerance range allowed by the drawing.

[0112] Conversely, if the following relationship is satisfied:

[0113] ;

[0114] The gearbox housing workpiece is then determined to have an unacceptable second roundness after the constraints are removed. This unacceptable state is the bearing hole roundness deviation fault found during routine quality inspection on the production line. This comparison step provides boundary condition inputs for the final isolation and determination of fixture-related causes.

[0115] Based on the comparison results of the first roundness parameter, the second roundness parameter, and the design roundness tolerance threshold, the specific steps for performing logical reasoning operations and outputting the fault diagnosis result of the out-of-tolerance roundness of the bearing hole of the gearbox housing workpiece include:

[0116] Set and verify the trigger logic conditions for the first diagnostic result. When the control system or analysis program receives a judgment input indicating that the first roundness parameter is qualified and the second roundness parameter is unqualified, the first diagnostic mechanism is triggered. The specific trigger logic is as follows:

[0117] ;

[0118] In the formula, This represents the first roundness parameter, in mm; This represents the second roundness parameter, in mm; This represents the design roundness tolerance threshold, in mm. This represents the logical AND operator. Based on a general analysis of the deformation principles of machining, the first roundness parameter being within acceptable limits indicates that the rotation trajectory of the machine tool spindle and the rigidity of the cutting system meet the machining requirements, and the machining equipment itself has not experienced any precision degradation. However, the second roundness parameter exceeding tolerance after the clamping constraints are removed indicates that excessive elastic strain energy accumulated inside the workpiece during the clamping stage. As the external force disappears, the stress release causes significant distortion of the circular hole wall. This logical combination physically eliminates the interference of machine tool body errors.

[0119] In response to the aforementioned triggering conditions, the first diagnostic result is output, clearly determining that the bearing hole roundness error of the gearbox housing workpiece is caused by deformation error due to fixture clamping. To transform the generalized fixture clamping cause into an operable adjustment basis in the field, the specific sub-points of this diagnostic result include the following common working conditions: the hydraulic or pneumatic pressure setting of the clamping actuator is too high, resulting in the clamping force applied to the thin-walled area exceeding the limit; the position of the clamping foot's application point is deviated from the internal reinforcing ribs or rigid nodes of the workpiece, generating a suspended bending moment; or there are chips and impurities attached to the bottom support reference surface of the fixture, causing the workpiece to bear additional unbalanced compressive stress when clamped and closed.

[0120] Set and verify the trigger logic conditions for the second diagnostic result to form a closed loop for fault diagnosis. When the system receives a judgment input indicating that the first roundness parameter is unqualified, the specific trigger logic relationship is as follows:

[0121] ;

[0122] In response to this trigger condition, regardless of the value of the second roundness parameter, a second diagnostic result is output, determining that the main cause of the bearing hole roundness deviation fault is the inherent error of the machining system. From a cutting geometry perspective, if the hole cross-section has lost its perfect circular shape while maintaining the current clamping force state and before elastic recovery occurs, it proves that the cutting trajectory of the tool itself has deviated or distorted. At this point, the next step in the troubleshooting will directly focus on machine tool equipment-level faults such as excessive radial runout of the machine tool spindle, excessive spindle bearing clearance, or insufficient rigidity of the boring bar causing tool chatter. For specific maintenance specifications for machine tool spindle accuracy, those skilled in the art can follow the machine tool maintenance manual, which is common knowledge in the field and will not be elaborated here.

[0123] Set and verify the trigger logic conditions for normal processing. When the system receives a judgment input indicating that both the first and second roundness parameters are qualified, the specific trigger logic is as follows:

[0124] ;

[0125] In response to this trigger condition, the system outputs a normal processing result, determining that the roundness of the bearing hole in the current workpiece meets the design requirements, and that both the machine tool status and the clamping force status are within reasonable process boundaries. The system then allows the workpiece to proceed to the next production process. This logic branch covers normal production scenarios without faults, ensuring the logical completeness of the entire numerical comparison and diagnostic mechanism.

[0126] Under the premise of triggering the second diagnostic result (i.e., determining that there is an inherent error in the machining system), the steps to further decouple and quantify the coupled deformation effect of fixture clamping on the roundness of bearing holes specifically include:

[0127] The system retrieves the first and second roundness parameters when the second diagnostic result is triggered. When the system determines that the first roundness parameter exceeds the design roundness tolerance threshold, it indicates that there is cutting trajectory distortion in the machine tool spindle or tool system. However, as a thin-walled workpiece, the gearbox housing, under this fault condition, often results in a final out-of-tolerance dimension that is a coupled result of inherent errors and springback deformation from fixture unloading. To determine whether the fixture system also needs simultaneous maintenance, it is necessary to extract the first and second roundness parameters from the same cross-section for difference analysis.

[0128] Calculate the deformation deviation parameter used to characterize the elastic recovery of the workpiece. From the perspective of mechanical structure mechanics, the first roundness parameter reflects the pure cutting trajectory error under stress, while the second roundness parameter includes both cutting error and stress release deformation. In on-site measurements in the workshop, due to the limitation that the two-point method cannot completely extract the phase angle of the roundness profile, the method of directly calculating the difference between two roundness scalar values ​​is used as an approximate engineering criterion. The absolute value of the difference can approximately isolate the inherent deviation of the machine tool body and reflect the change in cross-sectional shape caused by the external force applied by the fixture. The formula for calculating the deformation deviation parameter is:

[0129] ;

[0130] In the formula, This represents the deformation deviation parameter, in mm. This represents the second roundness parameter, in mm; This represents the first roundness parameter, in mm.

[0131] Determine the deformation threshold used to evaluate the rationality of clamping, denoted as . In engineering practice, due to the unavoidable slight deformation of thin-walled components, it is necessary to set an allowable fluctuation range. This deformation threshold... The specific determination method is divided into two sub-implementation methods: The first method is to perform finite element analysis on the three-dimensional digital model of the gearbox housing and extract the theoretical springback deformation of the bearing hole section under the nominal clamping force as the threshold; the second method is to use an empirical proportional reduction method, taking the value according to the preset proportion of the aforementioned design roundness tolerance threshold (usually taken as 20% to 30%). Here, the determined allowable deformation is defined as the deformation threshold. The specific mesh generation and load application process for finite element analysis can be performed by those skilled in the art using conventional mechanical simulation procedures, which are well-known techniques in the field and will not be elaborated upon here.

[0132] The calculated deformation deviation parameters are compared numerically with the deformation threshold, and the resulting detailed coupled fault diagnosis results are output. The specific comparison and judgment logic is as follows:

[0133] If the following relationship is satisfied:

[0134] ;

[0135] Then, a single fault diagnosis result will be output. In the formula, This represents the deformation deviation parameter, in mm. The value represents the deformation threshold in mm. This judgment indicates that although the machine tool itself produced an unqualified roundness, the clamping force of the fixture did not cause significant additional deformation. The system instructs on-site maintenance personnel to perform only single equipment repairs targeting the machine tool spindle, tool wear, or bearing clearance.

[0136] Conversely, if the following relationship is satisfied:

[0137] ;

[0138] The system then outputs a coupled fault diagnosis result. This result indicates that the current deviation is caused by two factors: the machine tool body has lost its rotational accuracy, and the clamping force of the fixture is set too high or the support point has failed, resulting in severe clamping deformation. The system instructs on-site maintenance personnel to restore the machine tool's accuracy while simultaneously recalibrating the hydraulic or pneumatic pressure parameters of the fixture and checking the positioning reference surface. This decoupled judgment mechanism reduces blind maintenance and missed fault diagnosis on the production line.

[0139] Specific application examples:

[0140] To facilitate understanding of the technical solution of the present invention, a specific application example is given below, based on the investigation of the problem of out-of-tolerance roundness of the bearing hole in the DCT400.

[0141] In this embodiment, the method can use conventional internal diameter measuring instruments such as roundness testers and dial indicators. This method is suitable for high-precision hole machining inspection of box-type parts made of cast iron, aluminum alloy, cast steel, etc. For thin-walled shells with a wall thickness of 4mm or less, the elastic deformation under stress is more pronounced, resulting in higher accuracy of the judgment. Regarding the selection of inspection points, at least four evenly distributed measurement points are selected circumferentially to avoid deviations in the judgment results due to accidental errors from a small number of inspection points.

[0142] Taking the DCT400 mid-plate part as an example, the design roundness tolerance threshold for the specified bearing hole in this housing is 0.012mm (i.e., ≤0.012mm). When batch roundness deviations occur after part processing, the specific implementation process for determining the cause using the method of this invention is as follows:

[0143] Machining and obtaining the workpiece: Select one medium-sized plate blank, position it, and clamp it on the special fixture of the machining equipment. Call the set machine tool operating parameters, use a PCD boring tool, and a spindle speed of 2400 r / min to cut the blank, complete the boring of the bearing hole, and generate the gearbox housing workpiece.

[0144] Clamping Status Inspection: After machining, maintain the workpiece in a closed clamping state. Using an inside micrometer, select a specified section at the axial midpoint of the designated bearing hole, and measure four diameter points circumferentially at 45° intervals to obtain the first hole diameter data. Calculate the difference between the maximum and minimum diameters to obtain the first roundness parameter, and record the corresponding dimensions.

[0145] Release state detection: Send a command to the fixture to release the workpiece and remove the physical constraint. Remove the workpiece and place it on a level marble testing platform free from external force and vibration to avoid errors introduced by placement posture or external interference. To ensure data comparability, use the same inside micrometer as in step two to obtain the second hole diameter data at the same cross-section and in the same measurement direction. Obtain the second roundness parameter by calculating the difference between the maximum and minimum diameters, and record the corresponding dimensions.

[0146] Results Comparison and Judgment: The actual measurement and calculation data obtained under the above two states are shown in the table below.

[0147] The table below shows the clamping and loosening status detection analysis.

[0148] Workpiece clamping state diameter Workpiece clamping state diameter Measurement point 1 84.973 84.979 Measurement point 2 84.976 84.989 Measurement point 3 84.971 84.973 Measurement point 4 84.972 84.966 Roundness value 0.005 0.023 judge Clamping is acceptable, loosening exceeds tolerance → the fixture is determined to be the cause.

[0149] Based on the measured data in the table, the first roundness parameter when the workpiece is clamped is 0.005 mm, and the second roundness parameter when the workpiece is released is 0.023 mm. These two roundness parameters are then compared with the design roundness tolerance threshold of 0.012 mm.

[0150] The comparison results show that the first roundness parameter meets the design roundness tolerance threshold (0.005≤0.012), while the second roundness parameter exceeds the design roundness tolerance threshold (0.023>0.012). According to the judgment logic of this invention, the condition of the first roundness parameter being qualified and the second roundness parameter being out of tolerance is met. The system outputs a diagnostic result indicating that the fixture factor is a single cause, directly determining that the core cause of the out-of-tolerance roundness of the bearing hole in the DCT400 is the elastic deformation of the workpiece caused by the fixture clamping, eliminating the inherent machining error of the machine tool itself. Based on this judgment result, the operator can directly carry out specific optimization of the fixture, avoiding the steps of blindly adjusting the machine tool and repeated trial cutting.

[0151] For ease of description, the above system is described by dividing it into various units and modules based on their functions. Of course, in implementing this application, the functions of each unit and module can be implemented in one or more software and / or hardware.

[0152] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0153] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0154] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings, characterized in that, Includes the following steps: Position and clamp the gearbox housing blank to be processed according to the clamping parameters; The machining process is performed to complete the machining of the specified bearing holes on the gearbox housing blank, thereby generating the gearbox housing workpiece; Maintaining the closed clamping state of the gearbox housing workpiece, acquiring first hole diameter data in multiple directions at a designated axial section of the designated bearing hole, and calculating a first roundness parameter based on the first hole diameter data; Release the constraints on the gearbox housing workpiece and let it stand still. Obtain second hole diameter data in multiple directions at the same axial section of the designated bearing hole, and calculate the second roundness parameter based on the second hole diameter data. The first roundness parameter is compared with the preset design roundness tolerance threshold, and the second roundness parameter is compared with the design roundness tolerance threshold. When the first roundness parameter meets the design roundness tolerance threshold and the second roundness parameter exceeds the design roundness tolerance threshold, the output indicates that the fixture factor is the single cause of the gearbox housing bearing hole roundness deviation. When the first roundness parameter exceeds the design roundness tolerance threshold, a second diagnostic result indicating that the machining system has an inherent error is output, and the difference between the first roundness parameter and the second roundness parameter is calculated. If the difference exceeds a preset deformation threshold, a coupling fault diagnostic result indicating that there is a fault cause of coupling between the machine tool and the fixture is output.

2. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The steps of positioning and clamping the gearbox housing blank to be machined according to the clamping parameters, and performing machining operations to complete the machining of the specified bearing holes on the gearbox housing blank specifically include: The gearbox housing blank is placed in the clamping mechanism of the processing equipment to complete the reference positioning of the gearbox housing blank; The clamping mechanism is triggered according to the set clamping parameters to apply an external constraint force to the gearbox housing blank to complete the closed clamping. The preset machine tool operating parameters and cutting tool parameters are called, wherein the preset machine tool operating parameters include spindle speed, feed rate and depth of cut to ensure consistency between machining cutting force and cutting heat. The spindle of the control processing equipment drives the cutting tool to rotate, and cuts the gearbox housing blank at a predetermined position according to the set processing trajectory and feed rate to form the designated bearing hole.

3. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The specific methods for calculating the first roundness parameter based on the first aperture data and the second roundness parameter based on the second aperture data are as follows: The maximum and minimum pore diameter values ​​are selected from the first pore diameter data, and half of the difference between the maximum pore diameter value selected from the first pore diameter data and the minimum pore diameter value selected from the first pore diameter data is used as the first roundness parameter. The maximum and minimum pore diameter values ​​are selected from the second pore diameter data, and half of the difference between the maximum and minimum pore diameter values ​​selected from the second pore diameter data is used as the second roundness parameter.

4. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The steps of obtaining first bore diameter data in multiple directions at a specified axial section of the specified bearing bore, and obtaining second bore diameter data in multiple directions at the same axial section of the specified bearing bore, specifically include: Using the same inner diameter measuring tool, position it to the specified axial section of the specified bearing hole; Using the theoretical axis of the specified bearing hole as a reference, the measurement direction is selected on the circumference according to the evenly divided angle, and the first hole diameter data is obtained in sequence. After the constraints are released, the reference hole or locating pin groove carried by the gearbox housing workpiece itself is used as a spatial phase reference to calibrate the starting zero-degree angle of the measurement. The same measurement position and measurement direction are maintained as when the first hole diameter data is obtained, and the same inner diameter measuring tool is used to obtain the second hole diameter data.

5. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The specific implementation method for maintaining the closed clamping state of the gearbox housing workpiece is as follows: After the machining process is completed, the motion control circuit of the clamping mechanism used to maintain the closed clamping state is locked, and no release or unloading command is sent to the clamping mechanism. The clamping force and auxiliary support force applied to the gearbox housing workpiece should be consistent in magnitude, point of application, and direction of application as during the machining process.

6. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The specific implementation method for releasing the constraint on the gearbox housing workpiece and allowing it to stand still is as follows: The clamping mechanism that controls and maintains the closed clamping state removes all physical constraints on the gearbox housing workpiece and moves the gearbox housing workpiece to a horizontal testing platform free from external interference. The gearbox housing workpiece is left to stand still for a preset time under its own weight only. The preset time is the time required to ensure that the microscopic thermal deformation caused by cutting heat and the mechanical elastic recovery after the fixture is removed are fully released.

7. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The step of calculating the difference between the first roundness parameter and the second roundness parameter, and outputting a coupling fault diagnosis result indicating the presence of a fault cause of machine tool and fixture coupling if the difference exceeds a preset deformation threshold, specifically includes: Calculate the absolute value of the difference between the second roundness parameter and the first roundness parameter, and define the absolute value as the deformation deviation parameter; compare the deformation deviation parameter with the deformation threshold. When the deformation deviation parameter is greater than the deformation threshold, the coupling fault diagnosis result is output; When the deformation deviation parameter is less than or equal to the deformation threshold, a single fault diagnosis result is output, indicating that only a single equipment repair is needed for the machine tool spindle, tool wear, or bearing clearance.

8. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The preset deformation threshold is the allowable deformation used to evaluate the rationality of clamping, and the preset deformation threshold can be obtained in any of the following ways: The preset proportional value of the preset design roundness tolerance threshold is directly converted into the deformation threshold, wherein the preset proportional value is set based on the material elastic modulus and wall thickness parameters of the gearbox housing workpiece; The theoretical springback deformation of the bearing hole section of the gearbox housing workpiece under the nominal clamping force is extracted using finite element analysis, and the theoretical springback deformation is used as the deformation threshold.

9. The method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in gearbox housings according to claim 1, characterized in that, The first diagnostic result of the indicated fixture factor as a single cause of out-of-tolerance bearing bore roundness of the gearbox housing specifically includes: The clamping force applied by the clamping actuator exceeds the limit, the support point arrangement of the fixture deviates from the rigid node inside the gearbox housing workpiece to generate a suspended bending moment, or there are impurities on the positioning reference surface of the fixture causing unbalanced extrusion stress.

10. A method for rapid determination of fixture factors causing out-of-tolerance roundness of bearing holes in a gearbox housing, as described in claim 1, is characterized in that... The preset design roundness tolerance threshold is an allowable error value set according to the hole tolerance accuracy grade of the target bearing hole; The method further includes: When the first roundness parameter is less than or equal to the preset design roundness tolerance threshold, and the second roundness parameter is less than or equal to the preset design roundness tolerance threshold, a normal machining result is output. The normal machining result indicates that the roundness of the bearing hole of the current workpiece meets the design requirements, and the diagnostic process ends.

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