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During the final assembly process, finding a best fitting resolution for gap and flush between assembled parts is the main object. This paper divides these fitting problems into two optimization stages, which are attitude fitting and position fitting, and proposes a mixed model which combines the Gaussian Imaging method (Enriched Complex Extended Gaussian Imaging) and even fitting algorithm (Hausdorff distance based criteria). It is illustrated that Gaussian Imaging method can be used to orient two similar curve objects and therefore accelerate the optimization process by the even fitting method. We also demonstrate the model by fitting a 2D classic case, an automobile door fitting into a frame, and generalize the application of the model into 3D curve fitting by fitting a simple automobile lamp into an auto-body. The best rotation and translation is found by using two curve objects' similarity in attitude and minimum width in gap and flush as criteria.

Since resistance spot welding has become the dominant method for car body assembly, studies on spot welding quality control and inspection are becoming more and more important and urgent for the automobile industry. Compared to the traditional air gun, the servo gun spot welding system has the advantages of precise control and feedback of electrode position and pressure. Therefore, it provides the possibility of controlling and inspecting weld quality online. By using the electrode position feedback function of the servo gun, this paper proposes a method for online weld quality inspection based on weld indentation. During a welding process, a weld indentation is extracted from a servo encoder under various welding failures. Then, a weld lobe, which is based on indentation, is built to identify the range for good welds. Finally, experimental data are presented to prove that this method can effectively achieve online weld quality inspection.

In this paper, an intelligent heuristic optimization algorithm in active variation compensation is proposed to improve the dimension accuracy in the assembly of a vehicle body by finding the optimal configuration of joint types and the corresponding assembly sequence to compensate variation accumulation in the conceptual assembly process. The authors develop and apply the algorithm to predict variation accumulation and then develop compensating assembly schemes to accomplish optimal joint configuration and assembly sequence compensating for the unnecessary or surplus variation. The essence of the active variation compensation algorithm means measuring and correcting assembling variations during the assembly conceptual process. The paper employs the design of experiment (DOE) approach to verify the heuristic optimization method in the simple application case.

The lower formability of aluminum alloy sheet greatly limits its application in reducing weight of stamping parts. This paper proposes a new strategy to optimize the variable blank holder force (BHF) and determine the drawing limit under the constant and variable BHF. The optimization strategy is based on the analysis of BHF formability window and integrated into FEM code to obtain time and spatial optimal BHF that applies on segmental binders. And then a stepped rectangular box of 60 mm drawing height with 10 segmental binders is adopted to validate the optimization strategy. The constant BHF experiment and the derived trajectory of optimal BHF are verified on a multipoint variable BHF hydraulic press and the experiment results correspond well with those of FEM optimization. This new BHF optimization strategy helps to determine time and spatial optimal BHF profiles simultaneity in a single round of FEM simulation, which makes it an effective method.

The body assembly process design (BAPD) system is currently under development at the laboratory of Auto Body Manufacture Technology Center of Shanghai Jiao Tong University. To ensure that assembly issues have been properly considered in the conceptual design phase, different methods, procedures and tools should be developed. The paper gives a brief view of the system architecture of the BAPD system, and the paper will present a framework to carry qualitative simulation procedure and conduct hierarchical qualitative simulation to analyze and predict assembly variation flow with limited parameters and fuzzy knowledge; the system conducts qualitative information acquisition of physical parameters of assembly features, and obtains cardinal factors influence the variation results by qualitative analysis in the assembly process. An analytical case is discussed to explain the function of qualitative analysis.

Mathematical models of the electromagnetic field, fluid flow and heat transfer of a three-dimensional moving gas tungsten arc (GTA) weld pool with external longitudinal magnetic field applied are established in the paper. Using a multi-coupled analysis function of ANSYS finite element code, distributions of current density and magnetic field, as well as fluid flow and heat transfer in a moving weld pool, were systematically studied and investigated to understand and reveal the effect of an external longitudinal magnetic field on liquid metal in a moving GTA weld pool and also to supply a basis for the application of an external longitudinal magnetic field in welding technology .

Wrinkling and fracture are main defects in sheet-metal forming. They can be reduced or eliminated by manipulating a suitable blank-holder force (BHF). But it is difficult to attain the optimum BHF during sheet-metal forming. In this article, a new optimization algorithm integrating the finite element method (FEM) and adaptive response surface methodology $(r)ARSM$(c) is presented to determinate the optimum BHF. To assure convergence, the trust region modes management strategies are used to adjust the move limit of design spaces. Finally, the optimum results of rectangular box deep drawing are given. Experiments are performed to verify the optimal result.

Under the control of external longitudinal magnetic field, substantial changes happen to ordinary gas tungsten arc welding (GTAW) process. In this paper, mathematical models of fluid flow and heat transfer of external longitudinal magnetic field moving GTAW three-dimensional weld pool were established. Current density distribution on weld pool surface was obtained by probe method. Using the multi-coupled analysis function of finite element analysis software ANSYS, distributions of current density and magnetic field as well as fluid flow and heat transfer in three-dimensional moving weld pool were systematically investigated to understand and reveal the effect of external longitudinal magnetic field on liquid metal in moving GTA weld pool and also to supply basis for the application of external longitudinal magnetic field welding technology.

In the stamping forming process of an automotive panel, some defects such as wrinkles and fractures can be eliminated by setting a proper drawbead, such that a successful forming operation can be obtained. The effect of the structure, the geometrical shape and the parameters of a drawbead on the draw restraining force has been analyzed, as also the effect of the draw restraining force on the metal flow in the panel forming process. Some principal guidelines of drawbead setting are summarized for the die-tool design of a panel. The drawing process of a trunk lid is simulated numerically using non-linear finite elements. Referencing the simulation results and the principal guidelines, the geometric shape of the drawbead is adjusted partly, and the material flow is controlled effectively during the drawing process. It is shown that the principal guidelines of drawbead design and the numerical simulation method of the cover panel forming process are reliable.

Postponement manufacturing often requires that the identical items should be differentiated for customization with different processes at a Customer Process Differentiation Point(CPDP). A significant issue then emerges as how to determine the input item quantity that should be processed with a customization process at a manufacturing stage. A real-time yield rate based methodology is proposed to achieve dynamic adjustment of MRP. The algorithm for implementing the proposed methodology is also developed. A case study shows that the item-differentiating decisions made at CPDP are more reasonable than those made according to traditional MRP approaches.

Since resistance spot welding (RSW) has become the dominant way for car-body assembly, studies on spot welding quality control and on-line inspection are becoming more and more important for automobile industry. This article mainly relates an on-line weld quality inspection way based on electrode indentation measured from servo gun. In the servo spot welding system, electrode indentation is extracted from servo encoder and calibrated by a PLC data collecting system including laser displacement sensor and A/D convertor. Then a weld lobe along with indentation is determined for 0.8mm DP600 sheet. At last, on-line quality inspection is carried out according to the indentation range in the weld lobe to demonstrate that this method is reliable.

This paper investigates new wavelet-based multiresolution modeling techniques in CAD. MRA techniques are extended to detail feature transplanting and detail feature copying from previous MRA editing including sweep editing, fractional editing, synthesis editing and detail blending. Two new editing methods called detail feature transplanting and detail feature copying are added to previous sweep editing, fractional editing, synthesis editing and detail blending. Detail feature transplanting editing is a way to transplant detail features of a curve/surface to another curve/surface. Detail feature copying editing is a way to copy or move detail features on the same curve/surface.

The main goal of this paper is to describe a method based on the continuous wavelet transform (CWT). The Shannon entropy of CWT coefficients in each scale is calculated in order to detect the characteristic trends of the CMM measurement data efficiently. This method is successfully implemented in a body-in-white (BIW) assembly for the detection of periodic trends in coordinate measure machine (CMM) data. It would contribute to main cause location in BIW quality control. The principle of the CWT and the property of the periodic trend after the CWT are explained from a mathematical viewpoint. An actual quality-control case is analyzed using the CWT method. Consistency between the results and the actual situation proves the effectiveness of this CWT method.