Three-dimensional design auxiliary method for complex slide shoe casting clamping fixture combined with CAD software

Abstract

This invention relates to the field of mechanical manufacturing and tooling fixture design technology, specifically a three-dimensional design auxiliary method for clamping fixtures of complex saddle castings using CAD software. The method includes: importing workpiece models, process information, fixture component information, machine tool space information, and machining and measurement path information, and unifying the coordinate systems of the machine tool, workpiece, and fixture; extracting clamping-related geometric features and process constraint features to determine candidate positioning surfaces, support positions, clamping positions, and auxiliary lifting positions; arranging positioning, support, and clamping components to form a clamping scheme based on process judgment parameters; performing contact establishment and clamping process simulation to obtain pre-seat and locking states; and then performing datum transfer, interference, and support height chain verification. If the conditions are met, the three-dimensional assembly result of the fixture is output; otherwise, adjustments are made and re-verification is performed. This invention improves the efficiency, reliability, and accuracy assurance capability of three-dimensional design of clamping fixtures for complex saddle castings under continuous processes.

Description

Technical Field

[0001] This invention relates to the field of mechanical manufacturing and tooling fixture design technology, specifically to a three-dimensional design auxiliary method for clamping fixtures for complex sliding saddle castings using CAD software. Background Technology

[0002] Currently, the design of clamping fixtures for complex saddle castings in multiple processes of roughing, semi-finishing, and finishing is usually based on general 3D modeling tools and human experience. When the workpiece has thin walls, long cantilever, composite datum transfer, and limited machining and measurement space, the existing design method cannot perform accurate analysis and dynamic verification of the process correlation of positioning surfaces, clamping areas, and fixture component arrangement. Each adjustment may be accompanied by repeated trial fittings, interference rework, and clamping instability risks, which reduces the efficiency and reliability of 3D fixture design. Summary of the Invention

[0003] The purpose of this invention is to provide a three-dimensional design assistance method for clamping fixtures of complex sliding saddle castings using CAD software. This method enables accurate analysis and dynamic verification of clamping schemes, avoids repeated trial fittings, interference rework, and the risk of clamping instability, and improves the efficiency and reliability of fixture three-dimensional design. This invention can be achieved through the following technical solutions: A 3D design-aided method for clamping fixtures of complex saddle castings, combined with CAD software, is applied to the 3D design of clamping fixtures for complex saddle castings in multiple processes including roughing, semi-finishing, and finishing. This includes: S1. Import the workpiece model, process information, fixture component information, machine tool space information, machining path and measurement path information, and establish and unify the machine tool coordinate system, workpiece coordinate system and fixture coordinate system; S2. Based on the unified information, extract the geometric features and process constraint features related to clamping, and determine the candidate positioning surface, candidate support position, candidate clamping position and auxiliary lifting position; S3. Determine the current process category based on the process judgment parameters, and select and arrange positioning elements, support elements and clamping elements in combination with candidate positioning surfaces, candidate support positions, candidate clamping positions, auxiliary lifting positions and fixture element information to form a clamping scheme. S4. Simulate the contact establishment and clamping process of the clamping scheme to obtain the workpiece pre-seat state and locking state. S5. Perform benchmark transfer verification, machining or measurement interference verification, and support height chain verification on the clamping scheme; output the three-dimensional assembly result of the fixture when all verifications meet the preset allowable conditions corresponding to the current process; if any verification is not met, adjust the clamping scheme and re-verify.

[0004] Preferably, S2 includes: Extract information on the area, flatness, local thickness, curvature variation, and prohibited pressure areas of candidate surfaces from the workpiece model to determine the pressure-bearing capacity level of each candidate surface; Based on the pressure bearing capacity level, surface spatial distribution, and degree of freedom constraints, the candidate surfaces are divided into a set of main positioning surfaces, a set of auxiliary positioning surfaces, and a set of limiting surfaces.

[0005] Preferably, S2 further includes: The degree of rigidity weakness is determined based on the local thin-wall distribution, long cantilever distribution, and center of gravity offset at the candidate clamping position; The thin-wall deformation assessment value is determined based on the local equivalent wall thickness at the candidate clamping position, the distance to the high-stiffness region, the cantilever characteristics, and the clamping eccentricity. When the thin-wall deformation assessment value is greater than the preset thin-wall threshold, the corresponding candidate clamping position is determined as the clamping prohibition position; When the thin-wall deformation assessment value is less than or equal to the preset thin-wall threshold, the corresponding candidate clamping position is determined as the clampable position.

[0006] Preferably, in S3, the process judgment parameters include blank size error, reference transfer accuracy requirement, tool deflection space requirement, measurement space requirement, and module reuse priority; The current process category is determined based on the process judgment parameters. The current process category includes at least roughing, semi-finishing, and finishing. The current process category is updated when at least one of the following conditions is exceeded: blank size error, reference transfer accuracy requirement, tool deflection space requirement, and measurement space requirement. Otherwise, the current process category is maintained.

[0007] Preferably, S4 includes: In the initial approach state, set the initial gap between the workpiece and the support element and determine the contact sequence; In the pre-contact state, the workpiece is allowed to be finely adjusted within a preset posture range, and the initial bonding state is determined based on the number of stable contact points, the stability of the center of gravity support, and the amount of posture drift. After determining that the initial bonding state meets the stable bonding conditions based on the number of stable contact points, the stability of the center of gravity support, and the amount of attitude drift, the clamping force is increased in stages to enter the locking state. If the support comes loose, the workpiece drifts beyond the limit, or the angle between the clamping direction and the local main force direction exceeds the preset allowable angle, the components should be reconfigured.

[0008] Preferably, when verifying the transfer of process-level references in S5, the reference status information after the transfer of each process reference is recorded, and the reference selection priority is determined according to the relative positional relationship between each reference and the key processing surface of the next process, the processing quality level, the repeatability accuracy and the degree of interference. When the reference selection priority reaches the preset upgrade threshold, the corresponding reference will be promoted to the priority positioning reference for the next process, and the positioning constraints and clamping constraints will be reassigned; when the reference selection priority does not reach the preset upgrade threshold, the current state of the corresponding reference will be maintained.

[0009] Preferably, the reference status information includes reference type, processed quality grade, pressure-bearing grade, repeatability, and dimensional relationship with the critical dimension chain; During process switching, the upgraded reference status information is invoked during the selection of candidate positioning surfaces for the next process, the loosening of existing supports, the verification of new support contact, and the redistribution of positioning.

[0010] Preferably, in S3, the main support, follower support, limit support, pressure plate, side clamping mechanism, hydraulic clamping mechanism and adjusting pad are combined and configured according to the current process category and fixture component information; For candidate clamping positions that are determined to be prohibited from clamping, no clamping elements are installed.

[0011] Preferably, S5 further includes a constraint check on the fixture components and the machining space, the constraint check including: The interference amount is determined based on the overlap volume of the fixture element with the tool envelope or probe path of the corresponding machining path and measurement path, the length of the blocked path, and its influence on the spindle swing angle range. The total deviation of the support height is determined based on the manufacturing deviation of the support elements, the thickness deviation of the adjusting shims, and the equivalent deviation caused by the mounting contact surface. When the interference exceeds the preset interference threshold, the arrangement of the fixture components is adjusted. When the total deviation of the support height exceeds the preset height chain allowable value, transition pads are used for compensation and the coplanarity of the support plane is rechecked.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves data integration for the three-dimensional design of clamping fixtures for complex saddle castings across multiple processes by importing workpiece models, process information, fixture component information, machine tool space information, and machining and measurement path information, and by unifying the machine tool coordinate system, workpiece coordinate system, and fixture coordinate system. Combined with the extraction and filtering of candidate positioning surfaces, candidate support positions, candidate clamping positions, and auxiliary lifting positions, it can generate process-related clamping schemes to meet different requirements of roughing, semi-finishing, and finishing. 2. This invention introduces a candidate surface bearing capacity level evaluation mechanism and a thin-wall deformation evaluation and prohibited clamping area determination mechanism to avoid misjudging areas with bearing capacity lower than the preset standard as the main positioning surface and to suppress the clamping deformation risk of thin-walled and long cantilever areas, thereby improving the accuracy and stability of positioning and clamping arrangement; 3. This invention, through state machine simulation of contact establishment, pre-seat placement and phased locking, as well as reference transfer verification, machining or measurement interference verification, fixture element and machining space limitation verification, and support height chain verification, can promptly detect problems such as support detachment, attitude drift, path blockage and coplanar misalignment and trigger adjustments, thereby reducing repeated trial assembly, interference rework and clamping instability, and improving the efficiency, reliability and accuracy assurance capability of 3D design of clamping fixtures for complex saddle castings under continuous processes. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application: Figure 1 This is a flowchart of the three-dimensional design assistance method for clamping fixtures of complex saddle castings using CAD software, based on the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0015] Please see Figure 1 This paper describes a 3D design auxiliary method for clamping fixtures of complex saddle castings, combining CAD software. This method is applied to the 3D design of clamping fixtures for complex saddle castings in multiple processes including roughing, semi-finishing, and finishing. The methods include: S1. Import the workpiece model, process information, fixture component information, machine tool space information, machining path and measurement path information, and establish and unify the machine tool coordinate system, workpiece coordinate system and fixture coordinate system; S2. Based on the unified information, extract the geometric features and process constraint features related to clamping, and determine the candidate positioning surface, candidate support position, candidate clamping position and auxiliary lifting position; S3. Determine the current process category based on the process judgment parameters, and select and arrange positioning elements, support elements and clamping elements in combination with candidate positioning surfaces, candidate support positions, candidate clamping positions, auxiliary lifting positions and fixture element information to form a clamping scheme. S4. Simulate the contact establishment and clamping process of the clamping scheme to obtain the workpiece pre-seat state and locking state. S5. Perform benchmark transfer verification, machining or measurement interference verification, and support height chain verification on the clamping scheme; output the three-dimensional assembly result of the fixture when all verifications meet the preset allowable conditions corresponding to the current process; if any verification is not met, adjust the clamping scheme and re-verify. S2 includes: Extract information on the area, flatness, local thickness, curvature variation, and prohibited pressure areas of candidate surfaces from the workpiece model to determine the pressure-bearing capacity level of each candidate surface; Based on the pressure bearing capacity level, surface spatial distribution, and degree of freedom constraint requirements, the candidate surfaces are divided into a set of main positioning surfaces, a set of auxiliary positioning surfaces, and a set of limiting surfaces. S2 also includes: The degree of rigidity weakness is determined based on the local thin-wall distribution, long cantilever distribution, and center of gravity offset at the candidate clamping position; The thin-wall deformation assessment value is determined based on the local equivalent wall thickness at the candidate clamping position, the distance to the high-stiffness region, the cantilever characteristics, and the clamping eccentricity. When the thin-wall deformation assessment value is greater than the preset thin-wall threshold, the corresponding candidate clamping position is determined as the clamping prohibition position; When the thin-wall deformation assessment value is less than or equal to the preset thin-wall threshold, the corresponding candidate clamping position is determined as the clampable position.

[0016] The system in this embodiment is deployed at the process planning end of a large CNC machining center. For complex saddle castings with composite features such as housing, guide rail surface, side ear plate and inner cavity, a three-dimensional solution for clamping fixtures is performed for multiple consecutive processes from roughing to finishing. The system acquires the workpiece's three-dimensional boundary representation model, product manufacturing information process annotation data, fixture component parameter library, machine tool workspace parameters, and computer-aided manufacturing toolpath and probe path envelope data through the data import module, and establishes and calibrates the machine tool coordinate system, workpiece coordinate system, and fixture coordinate system in a unified global space. To ensure the continuity of the subsequent parsing process, if some surface machining allowances or material attribute fields are found to be missing during the import process, the system will automatically call the basic attributes in the standard blank library to fill the missing nodes with default values, so as to avoid interruption of the entire feature extraction process due to local data breaks. After completing coordinate system one, the system enters the feature analysis stage, extracting geometric features and process constraint features related to clamping, and determining candidate positioning surfaces, candidate support positions, candidate clamping positions, and auxiliary lifting positions on the workpiece surface; the scheduling engine determines the current process category based on the current process judgment parameters covering blank size error, datum transfer accuracy requirements, tool deflection space requirements, measurement space requirements, and module reuse priority. Based on the process category, the system selects positioning elements, support elements, and clamping elements from the fixture resource pool and arranges them in space to form an initial clamping scheme; the system performs physical simulation of the contact establishment and clamping process for this scheme to solve the pre-seat state and final locking state of the workpiece. The system transforms the fixture support point into an equivalent three-dimensional linear spring model. The input feature vector of its simulation model includes the spatial coordinates of the contact points of each fixture element, the initial normal clearance, the equivalent stiffness coefficient of the element, and the workpiece gravity vector. By constructing the overall stiffness matrix Substitute the vector containing the workpiece's gravity. The applied clamping force vector and the support reaction vector equivalently generated by the three-dimensional linear spring model The system of static equilibrium equations for multiple rigid bodies; Among them, gravity vector Clamping force vector and support reaction vector Both are six-dimensional generalized force vectors containing three translational force components and three rotational torque components, and are represented by the displacement vectors of the workpiece in the three translational directions (X, Y, and Z) and the three rotational directions. The output vector is used for iterative solution until the resultant force and resultant moment residuals approach the preset zero extreme value, thereby determining the final contact force distribution and locking state. The formula is as follows: The system performs benchmark transfer verification, machining or measurement interference verification, and support height chain verification on the clamping scheme; when all the above verifications meet the preset allowable conditions corresponding to the current process, the system outputs the three-dimensional assembly result of the fixture; If any check fails, the constraint adjustment mechanism is triggered, the clamping scheme is modified, and the check process is restarted; the system introduces an evaluation mechanism for pressure bearing capacity level; the system extracts the area, flatness, local thickness, curvature change, and information on prohibited pressure areas marked in the product manufacturing information of each candidate surface; The calculation logic calculates the pressure-bearing capacity level of each candidate surface according to the rule that the pressure-bearing capacity increases when the area increases, the flatness error decreases, the local thickness increases, the curvature change decreases, and there is no information on prohibited pressure areas; for example, the system normalizes the area, flatness, local thickness, and curvature changes. Positive normalization is used for area and local thickness that are positively correlated with bearing capacity, while negative normalization is used for flatness error and curvature change that are negatively correlated. Specifically, for positive normalization, the system will extract the current value of the corresponding indicator. Subtract the minimum value of this index obtained statistically among all current candidate surfaces. And divide by the maximum value of this index obtained statistically among all current candidate surfaces. and minimum value The difference is used to obtain the normalized value. That is, using the calculation formula: For inverse normalization, the system will maximize the value. Subtract the current extraction value Then divide by the maximum value and minimum value The difference is used to obtain the normalized value. That is, using the calculation formula: Before performing the above calculations, the system determines... and If the absolute value of the difference is less than the preset floating-point minimum tolerance, then the normalized value of this index is directly assigned to 1 for all current surfaces; through the above processing, it is ensured that the normalized index value is limited to... Within the range The system calculates the normalized values ​​of each indicator. With the corresponding number The equal weighting coefficients of each indicator The sum of the products, and its relationship with the Boolean state of the prohibited pressure zone. Multiply by the product to calculate the pressure-bearing capacity rating. The calculation formula used is: Among them, the index serial number The values ​​1, 2, 3, and 4 are assigned sequentially, corresponding to the four indicators of area, flatness, local thickness, and curvature variation, respectively; equal weighting coefficients are used. Let be a pre-defined dimensionless constant, and satisfy... This is used to balance the relative contribution of each geometric characteristic index to the pressure bearing capacity level; Based on the calculated pressure-bearing capacity level, combined with the spatial distribution of the surface and the freedom constraints of the current process, the system decouples the candidate surfaces and divides them into a set of main positioning surfaces, a set of auxiliary positioning surfaces, and a set of limiting surfaces for direct use in subsequent resource orchestration; the system also performs a quantitative assessment of the rigidity of the candidate clamping areas. The thin-wall deformation assessment value is calculated based on the local equivalent wall thickness, the distance to the high stiffness region, the cantilever characteristics, and the clamping eccentricity. It follows the rule that the assessment result increases when the local equivalent wall thickness is less than the preset wall thickness threshold, the distance to the high stiffness region is greater than the preset distance threshold, the cantilever characteristic size is greater than the preset size threshold, and the clamping eccentricity is greater than the preset eccentricity threshold. When the thin-wall deformation assessment value of a candidate clamping area is greater than the preset thin-wall threshold, the system updates its status flag to a prohibited clamping area, thereby avoiding damage to the rigid and weak area by the clamping force. For example, for the quantification of thin-wall deformation assessment values, the system adopts a structured scoring accumulation mechanism: for example, a local equivalent wall thickness score of 40 points for less than 10mm, a distance score to the high stiffness area score of 30 points for greater than 50mm, a cantilever feature score of 20 points for cantilever, and a clamping eccentricity score of 10 points for eccentricity greater than 5mm. If a region has an equivalent wall thickness of 8mm, is 60mm away from the high-rigidity zone, has a cantilever and is 7mm eccentric, then the evaluation value is 40+30+20+10=100 points; if the preset thin-wall threshold is 80 points, then the region exceeds the threshold and the clamping operation is explicitly blocked.

[0017] In S3, the process judgment parameters include blank size error, reference transfer accuracy requirements, tool deflection space requirements, measurement space requirements, and module reuse priority. The current process category is determined based on the process judgment parameters. The current process category includes at least roughing, semi-finishing, and finishing. The current process category is updated when at least one of the blank size error, reference transfer accuracy requirement, tool deflection space requirement, and measurement space requirement crosses a preset switching threshold corresponding to another process category; otherwise, the current process category is maintained. S4 includes: setting the initial gap between the workpiece and the support element and determining the contact sequence in the initial approach state; In the pre-contact state, the workpiece is allowed to be finely adjusted within a preset posture range, and the initial bonding state is determined based on the number of stable contact points, the stability of the center of gravity support, and the amount of posture drift. After determining that the initial bonding state meets the stable bonding conditions based on the number of stable contact points, the stability of the center of gravity support, and the amount of attitude drift, the clamping force is increased in stages to enter the locking state. If the support comes off, the workpiece drifts beyond the limit, or the angle between the clamping direction and the local main force direction exceeds the preset allowable angle, the components should be reconfigured. S3 also combines and configures the main support, follower support, limit support, pressure plate, side clamping mechanism, hydraulic clamping mechanism and adjusting pad according to the current process category and fixture component information; For candidate clamping positions that are determined to be prohibited from clamping, no clamping elements are installed.

[0018] The system introduces dynamic process judgment parameters, which include not only blank size error, reference transfer accuracy requirements, tool deflection space requirements, and measurement space requirements, but also module reuse priority. This priority is a sorting result calculated based on the number of reusable fixture components in the current resource library and the adjustment amount required to adapt to the current process. Specifically, the system calculates a reuse score for each candidate fixture module. The system calculates the reuse score according to the rule of using the number of components as a positive factor and the adjustment amount as a negative factor, and sorts them in descending order. The reuse score is the product of the reusable quantity and the first preset coefficient, minus the product of the adjustment amount and the second preset coefficient. The scheduling engine determines the current process category, namely roughing, semi-finishing, or finishing, based on the above-mentioned judgment parameters. During the multi-round iterative optimization process, the system continuously monitors the status of the above parameters. When at least one of the blank size error, reference transfer accuracy requirement, tool clearance space requirement, and measurement space requirement crosses the preset switching threshold corresponding to another process category, the system immediately updates the current process category; otherwise, it maintains the current category. Meanwhile, when the real-time evaluation value of the tool space requirement crosses the first preset switching threshold, or when the real-time evaluation value of the measurement space requirement crosses, for example, a preset switching threshold greater than 80%, at least one of the conditions of crossing the preset switching threshold is met, and the system automatically updates the current process category. Based on the determined current process category and fixture component information, the system combines and configures the main support, follower support, limit support, pressure plate, side clamping mechanism, hydraulic clamping mechanism and adjusting pad; During this configuration process, the system directly reads the area markers generated in the previous steps. For candidate clamping areas where the thin-wall deformation evaluation value exceeds the preset thin-wall threshold, the system forcibly limits the participation of the area and does not arrange any clamping elements. This embodiment constructs a three-stage clamping state machine simulation process; in the initial approach state, the system sets an initial small gap between the workpiece and the support and calculates the theoretical contact sequence; in the pre-contact state, the system allows the workpiece to be finely adjusted under the action of gravity within a preset posture range; During this process, the system collects the number of stable contact points, the stability of the center of gravity support, and the workpiece attitude drift before and after fine-tuning in real time; the stability of the center of gravity support is characterized by determining whether the projection of the workpiece's center of gravity falls within the support polygon area formed by the support points. Based on the above data, the system determines whether a stable initial bonding state has been reached. When the initial bonding state meets the preset stability conditions, the system gradually increases the clamping force in stages until it enters the locking state. The specific rules for applying the clamping force in stages are as follows: the target maximum clamping force is divided into N fixed loading steps, for example, N is 10. After applying the corresponding clamping force increment in each loading step, the system extracts the current force residual and node displacement change of the workpiece. Static equilibrium is determined to be reached only when the force balance residual of the current step approaches zero and the change in node displacement is lower than the preset displacement convergence tolerance, thus triggering the application of clamping force in the next step, thereby avoiding algorithm divergence caused by the application of full load in a single step. If, during state machine simulation, the support detaches, the workpiece attitude drift exceeds the limit, or the angle between the clamping direction and the local main force direction (i.e., the direction determined on the corresponding local surface according to the processing load direction or the measured contact force direction of the current process) exceeds the preset allowable angle, the system will immediately interrupt the current simulation cycle, determine that the clamping has failed, and roll back to the resource configuration stage to rearrange the components. To ensure the accuracy of the judgment, the specific quantitative rule for determining that the workpiece attitude drift exceeds the limit is as follows: collect the spatial displacement change value of the workpiece in the three translational degrees of freedom of the X, Y, and Z axes and the rotation angle change value around the three axes before and after the fine adjustment. When any spatial displacement change value is greater than, for example, a preset translational tolerance of 0.05 mm, or any rotation angle change value is greater than, for example, a preset rotational tolerance of 0.1 degrees, the attitude drift exceeds the limit. The preset allowable angle is determined based on the direction of the maximum cutting force component of the current process cutting force estimation model and the static friction coefficient between the fixture elements and the workpiece surface. To avoid abstract, unobservable models and ensure dimensional consistency in static analysis, the direction of the maximum cutting force component is determined by extracting the depth of cut from the computer-aided manufacturing process data. and feed rate Combined with the empirical unit cutting force coefficient of the corresponding workpiece material The theoretical main cutting force is calculated using empirical formulas for cutting force. : The system further extracts the principal cutting edge angle and inclination angle parameters of the tool in the current step, and uses the geometric space direction cosine to map and project the theoretical principal cutting force to calculate the magnitude of the cutting force components in the three orthogonal directions of X, Y, and Z. The system then performs spatial vector synthesis to obtain the resultant force direction, which is taken as the direction of the maximum cutting force component. This ensures that the normal component of the clamping force is sufficient to overcome the normal working load, and that the tangential component does not exceed the static friction limit. For example, in the machining of saddle castings, the upper limit of the preset allowable angle is usually set to 15 degrees.

[0019] When verifying the transfer of process-level references in S5, the reference status information after the transfer of each process reference is recorded, and the reference selection priority is determined based on the relative positional relationship between each reference and the key machining surface of the next process, the machining quality level, the repeatability accuracy, and the degree of interference. When the priority of the reference selection reaches the preset upgrade threshold, the corresponding reference will be promoted to the priority positioning reference of the next process, and the positioning constraints and clamping constraints will be reassigned. The reference status information includes reference type, processed quality grade, pressure rating, repeatability, and dimensional relationship with the critical dimension chain; During process switching, the upgraded reference status information is called during the selection of candidate positioning surfaces for the next process, the loosening of existing supports, the verification of new support contact, and the reallocation of positioning. S5 also includes constraint checks on fixture components and machining space, including: The interference amount is determined based on the overlap volume of the fixture element with the tool envelope or probe path of the corresponding machining path and measurement path, the length of the blocked path, and its influence on the spindle swing angle range. The total deviation of the support height is determined based on the manufacturing deviation of the support elements, the thickness deviation of the adjusting shims, and the equivalent deviation caused by the mounting contact surface. When the interference exceeds the preset interference threshold, the arrangement of the fixture components is adjusted. When the total deviation of the support height exceeds the preset height chain allowable value, transition pads are used for compensation and the coplanarity of the support plane is rechecked.

[0020] When the system verifies the transfer of process-level benchmarks, it records the benchmark status information after each process is completed in the global status record table. This status information includes the reference type, the grade of finished quality, the pressure rating, the repeatability, and the relative positional relationship between the reference and the critical dimension chain, which includes the reference dimension, the transfer dimension, or the closed-loop dimension. The scheduling engine sorts the references based on their relative positional relationship with the critical machining surfaces of the next process, machining quality level, repeatability accuracy, and degree of interference, and calculates the reference selection priority value. To ensure that priority determination has a clear quantitative basis, the system uses a discrete index scoring system to determine the order value; for example: 30 points for parallel or perpendicular relative position, 10 points for otherwise, 30 points for machining quality reaching the finishing level, 20 points for semi-finishing, 20 points for repeatability accuracy less than 0.01mm, and 20 points for no interference. When the priority value of a certain reference reaches the preset upgrade threshold, the system upgrades its status to the priority positioning reference for the next process and reallocates positioning constraints and clamping constraints accordingly. When switching between actual processes, the system directly calls the upgraded reference status information and uses it as the input conditions for selecting candidate positioning surfaces for the next process, releasing and loosening existing supports, and verifying the contact of new supports. This corrects the support arrangement and clamping sequence in the next process, achieving smooth inheritance of the reference. The system also performs constraint checks on fixture components and machining space. The system extracts the overlap volume between the fixture element and the tool envelope or probe path, the length of the blocked path, and the reduction in the spindle swing angle range. These parameters are then normalized according to their respective preset upper limits, and the interference is calculated by weighting to obtain the above comprehensive evaluation value. To clarify the order of magnitude boundaries of the normalization conversion, the system uses linear proportional mapping logic for normalization: the actual extracted value of the overlapping volume is divided by the maximum allowed overlapping volume of the safety space of this type of fixture element, the length of the blocked path is divided by the total length of the machining path of the probe or tool in this step as the upper limit value, and the spindle swing angle reduction is divided by the rated swing angle range of the machine tool spindle as the upper limit value. If the actual extracted value of any indicator exceeds its corresponding preset upper limit during the calculation process, the normalized value is set to 1; otherwise, the actual ratio is used, thus strictly limiting the value range of each interference indicator to a uniform value. Inside; The weighted calculation logic assigns specific weights to each normalized index, such as 40% for overlapping volume, 40% for blocked path, and 20% for principal axis swing angle reduction. For example, if the overlapping volume accounts for 50% of the upper limit after normalization, the blocked path accounts for 10% of the upper limit, and the principal axis swing angle is not reduced, then the interference amount is 0.5×0.4+0.1×0.4+0=0.24. When the interference amount, i.e., 0.24, does not exceed a preset interference threshold of, for example, 0.3, the verification is deemed successful; if it exceeds the threshold, the system triggers an anti-collision adjustment mechanism, iteratively translating the position of the fixture element along the normal direction of the tool or probe path that caused the interference with a preset step size, or iteratively rotating the pose of the fixture element with a preset angle, until the recalculated interference amount is less than or equal to the preset interference threshold, and the rearrangement is completed; at the same time, during the modular fixture changeover process, the superposition of manufacturing errors of standard parts will lead to a decrease in the coplanarity of the support plane; The system collects manufacturing deviations of support components, thickness deviations of pads, and equivalent deviations caused by installation contact surfaces. It sums up the absolute values ​​of each deviation to calculate the total deviation of the support height. When the total deviation of the support height exceeds the preset height chain allowable value of the corresponding process, the system inserts transition pads in the virtual assembly model for thickness compensation and rechecks the coplanarity of the support plane. To achieve an accurate mapping from deviation exceeding tolerance to compensation execution, the system establishes the following thickness compensation rule: extract the global absolute Z-axis coordinates of the contact surfaces of all current main support components, and select the maximum Z-axis coordinate value as the ideal coplanar reference line; For each support point whose Z-coordinate value is lower than the guideline, calculate the difference between the guideline and its Z-coordinate value. When the difference is greater than, for example, a preset assembly fit gap of 0.01mm, directly determine the difference as the target thickness value of the transition pad required at the corresponding position, and complete the determined quantitative parameter compensation. If, during the compensation process, it is found that there is no transition pad of suitable thickness in the existing pad resource library, the system will automatically generate a custom pad processing requirement and mark the current height compensation status as pending, thereby avoiding the distortion of height chain calculation caused by forcibly pushing forward the assembly due to the lack of adaptable components.

[0021] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for assisting in the 3D design of clamping fixtures for complex saddle castings using CAD software, applied to the 3D design of clamping fixtures for complex saddle castings in multiple processes including roughing, semi-finishing, and finishing. Its features include: include: S1. Import the workpiece model, process information, fixture component information, machine tool space information, machining path and measurement path information, and establish and unify the machine tool coordinate system, workpiece coordinate system and fixture coordinate system; S2. Based on the unified information, extract the geometric features and process constraint features related to clamping, and determine the candidate positioning surface, candidate support position, candidate clamping position and auxiliary lifting position; S3. Determine the current process category based on the process judgment parameters, and select and arrange positioning elements, support elements and clamping elements in combination with the candidate positioning surface, candidate support position, candidate clamping position, auxiliary lifting position and fixture element information to form a clamping scheme. S4. Simulate the contact establishment and clamping process of the clamping scheme to obtain the workpiece pre-seat state and locking state. S5. Perform benchmark transfer verification, machining or measurement interference verification, and support height chain verification on the clamping scheme; output the three-dimensional assembly result of the fixture when all verifications meet the preset allowable conditions corresponding to the current process; if any verification is not met, adjust the clamping scheme and re-verify.

2. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software, as described in claim 1, is characterized in that... S2 includes: Extract the area, flatness, local thickness, curvature variation, and prohibited pressure area information of the candidate surfaces in the workpiece model to determine the pressure bearing capacity level of each candidate surface; Based on the pressure bearing capacity level, surface spatial distribution, and degree of freedom constraint requirements, the candidate surfaces are divided into a set of main positioning surfaces, a set of auxiliary positioning surfaces, and a set of limiting surfaces.

3. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software, as described in claim 2, is characterized in that... S2 further includes: The degree of rigidity weakness is determined based on the local thin-wall distribution, long cantilever distribution, and center of gravity offset of the candidate clamping positions; the thin-wall deformation evaluation value is determined based on the local equivalent wall thickness, distance to the high-stiffness region, cantilever characteristics, and clamping eccentricity of the candidate clamping positions; when the thin-wall deformation evaluation value is greater than a preset thin-wall threshold, the corresponding candidate clamping position is determined as a prohibited clamping position; when the thin-wall deformation evaluation value is less than or equal to the preset thin-wall threshold, the corresponding candidate clamping position is determined as a clampable position.

4. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software as described in claim 1, characterized in that, In S3, the process determination parameters include blank size error, reference transfer accuracy requirement, tool deflection space requirement, measurement space requirement, and module reuse priority. The current process category is determined based on the process determination parameters, and the current process category includes at least roughing, semi-finishing, and finishing. The current process category is updated when at least one of the blank size error, reference transfer accuracy requirement, tool deflection space requirement, and measurement space requirement crosses a preset switching threshold corresponding to another process category; otherwise, the current process category is maintained.

5. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software, as described in claim 1, is characterized in that... S4 includes: In the initial approach state, the initial gap between the workpiece and the support element is set and the contact sequence is determined; In the pre-contact state, the workpiece is allowed to be finely adjusted within a preset posture range, and the initial bonding state is determined based on the number of stable contact points, the stability of the center of gravity support, and the amount of posture drift. After determining that the initial bonding state meets the stable bonding conditions based on the number of stable contact points, the stability of the center of gravity support, and the amount of attitude drift, the clamping force is increased in stages to enter the locking state. If the support comes loose, the workpiece drifts beyond the limit, or the angle between the clamping direction and the local main force direction exceeds the preset allowable angle, the components should be reconfigured.

6. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software as described in claim 1, characterized in that, When verifying the transfer of process-level references in S5, the reference status information after the transfer of each process reference is recorded, and the reference selection priority is determined according to the relative positional relationship between each reference and the key processing surface of the next process, the processing quality level, the repeatability accuracy and the degree of interference. When the reference selection priority reaches the preset upgrade threshold, the corresponding reference is promoted to the priority positioning reference of the next process, and the positioning constraints and clamping constraints are reassigned; when the reference selection priority does not reach the preset upgrade threshold, the current state of the corresponding reference is maintained.

7. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software, as described in claim 6, is characterized in that... The reference status information includes reference type, processed quality grade, pressure bearing capacity grade, repeatability accuracy, and dimensional relationship with the critical dimension chain; During process switching, the upgraded reference status information is invoked during the selection of candidate positioning surfaces for the next process, the loosening of existing supports, the verification of new support contact, and the redistribution of positioning.

8. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software, as described in claim 3, is characterized in that... S3 further combines and configures the main support, follower support, limit support, pressure plate, side clamping mechanism, hydraulic clamping mechanism and adjusting pad according to the current process category and fixture component information. Specifically, for the candidate clamping positions that are determined to be prohibited clamping positions, no clamping elements are arranged.

9. The method for assisting in the three-dimensional design of clamping fixtures for complex sliding saddle castings using CAD software, as described in claim 8, is characterized in that... S5 also includes a constraint check on the fixture components and the machining space, the constraint check including: The interference amount is determined based on the overlap volume of the fixture element with the tool envelope or probe path corresponding to the machining path and measurement path, the length of the blocked path, and the influence on the spindle swing angle range. The total deviation of the support height is determined based on the manufacturing deviation of the support element, the thickness deviation of the adjusting shim, and the equivalent deviation caused by the mounting contact surface. When the interference exceeds a preset interference threshold, the arrangement of the fixture components is adjusted. When the total deviation of the support height exceeds the preset height chain allowable value, a transition pad is used for compensation and the coplanarity of the support plane is rechecked.

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