Research on the rapid design technology of automotive inspection structure based on MBD model

In view of the specificity and low efficiency of the design of automobile inspection fixture, a deformation design method of inspection fixture based on BP neural network algorithm is proposed. BP neural network algorithm is used to realize the learning and classification of case knowledge, and FCM (fuzzy c-means) algorithm and kernel principal component analysis are used to optimize the information source to improve the retrieval efficiency and accuracy. Based on the analysis of the existing fixture design case structure, the case structure is skeletonized to increase the applicability of the case structure. At the same time, the case frame structure is associated with the size chain, the priority deformation rule is proposed, and the relationship of each size chain is established to realize the mutual adjustment of each size chain. From the similarity of retrieval cases, the paper proposes the design scheme of inspection tools to improve the design efficiency. Finally, taking the front bumper model as the experimental object, the deformation rules are compared, and the priority deformation rule is more accurate than the ordinary basic rule. Compared with the manual design, the design efficiency of this method is improved by 55.71%, which proves the feasibility of this method.

EFFICIENT SPOT WELDING SEQUENCE SIMULATION IN COMPLIANT VARIATION SIMULATION

Geometrical variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometrical variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components, can be achieved using the Method of Influence Coefficients (MIC), based on the Finite Element Method (FEM). The sequence with which the spot welding operation is performed influences the final geometrical deformations of the assembly. Finding the optimal sequence that results in the minimum geometrical deformation is a combinatorial problem that is experimentally and computationally expensive. Traditionally, spot welding sequence optimization strategies have been to simulate the geometrical variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, a method is proposed where the springback calculation in the inspection fixture is bypassed during the sequence evaluation. The results show a significant correlation between the proposed method of weld relative displacements evaluation in the assembly fixture and the assembly deformation in the inspection fixture. Evaluating the relative weld displacement makes each assembly simulation less time-consuming, and thereby, sequence optimization time can be reduced by up to 30%, compared to the traditional approach.

Efficient Spot Welding Sequence Simulation in Compliant Variation Simulation

Geometric variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometric variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components can be achieved using the Method of Influence Coefficients (MIC), based on the Finite Element Method (FEM). The sequence, with which the spot welding operation is performed, influences the final geometric deformations of the assembly. Finding the optimal sequence that results in the minimum geometric deformation is a combinatorial problem that is experimentally and computationally expensive. For an assembly with N number of welds, there are N! possible sequences to perform the spot welding operation. Traditionally, spot welding optimization strategies have been to simulate the geometric variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture, using an appropriate measure of variation. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, the cause of variation in the deformations after the springback, between different sequences is identified. The relative displacements of the weld points in the assembly fixture, when welded in a sequence, is the source of such behavior. Capturing these displacements leads to large time savings during sequence optimization. Moreover, this approach is independent of the inspection fixture. The relative weld displacements have been evaluated on two sheet metal assemblies. The sequence optimization problem has been solved for the two assemblies using this approach. The optimal sequence, the corresponding final assembly deformations, and the time-consumption have been compared to the traditional approach. The results show a significant correlation between the weld relative displacements in the assembly fixture, and the assembly deformation in the inspection fixture. Considering the relative weld displacement makes each assembly evaluation less time-consuming, and thereby, sequence optimization time can be reduced up to 30%, compared to the traditional approach.

A Finite-Element Boundary Condition Setting Method for the Virtual Mounting of Compliant Components

Using finite-element analysis (FEA) to numerically mount compliant components onto their inspection fixture is an approach proposed by researchers in the field of computational metrology. To address the shortcomings of the underlying principle of current methods, this paper presents a boundary displacement constrained (BDC) optimization using FEA. The optimization seeks to minimize the distance between corresponding points, in the scanned manufactured part and the nominal model, that are in unconstrained regions. This is done while maintaining that a distance between corresponding points in constrained regions (i.e., fixing points) remains within a specified contact distance. At the same time, the optimization limits the magnitude and direction of forces on boundary. In contrast to the current methods, postprocessing of the point cloud is not required since the method uses information retrieved from the FEA of the nominal model to estimate the manufactured part’s mechanical behavior. To investigate the performance of the proposed method, it is tested on ten (10) free-state simulated manufactured aerospace panels that differ in their level of induced deformation. Results are then compared to those obtained using the underlying principles of current methods.

Fixture Design Process Automation for Coordinate Measuring Machines: A Knowledge-Based Approach

Nowadays, the inspection process is an essential part of the manufacturing process, where a product is subjected to verification of the geometric features, dimensions and tolerance specifications with respect to the product design specifications. One of the most interesting topics in the automation of the inspection process is the right fixture design. In the fixture design process we have used the information provided by the part design and manufacturing process. However, the lack of integration and structuring of this information results in one of the most important problems, producing an increase in the time and cost implied in the development of the fixture design and its implementation. For this reason, this work presents a knowledge model for the inspection fixture design process for a Coordinate Measuring Machine (CMM), which allows the automation of the inspection fixture design process to be made easier, reducing time and cost associated to the inspection process and to the manufacturing process in general.

Paper 39: In Situ Out-of-Roundness Measurement

A new method is described for measurement of out-of-roundness characteristics of parts under conditions that are now considered extremely difficult or impossible. For example, it is now possible to measure very large parts while they are still mounted in the machine tool, on a makeshift inspection fixture, or even in an assembly. Typical of parts now being measured by this method are crankshaft journals and throw surfaces, piston pins, machine tool spindle shafts, mill rolls, and reactor fuel rods. No expensive masters, precision spindles, or special skills are required. Results are plotted and measured on polar charts such as used on the more conventional roundness gauge. Accuracy of the out-of-roundness measurement is within ±10 per cent for most parts.