Key Engineering Materials Vols. 419-420

Abstract: Constraint-based model reconstruction is one of the key research problems in recent reverse engineering. Surfaces of structural parts are mostly quadratic and have mutual constraints. Aiming at this feature, the paper proposes a method for conducting constraint-based synchronous fitting on multiple surfaces. Synchronous fitting is carried out through constraint optimization method, the constraints among surfaces can be maintained and the original design intents incarnated.

Abstract: A framework for process planning and NC programming based on STEP and STEP-NC data model is proposed in this paper. The STEP standard and its data structure for CAD models, especially the NURBS based representation of complex surfaces is analyzed. Then the general strategy for process planning using the STEP-NC data structure is presented, and the calculation of cutter contact points and cutter location data for producing complex surfaces based on the geometrical information is addressed. Finally a prototype system is developed for demonstration of the proposed STEP-compliant NC programming approach for complex surface components.

Abstract: In the field of reverse engineering, data quality assessment is a very important work in the detection, the result of data quality assessment will directly or indirectly affect the detection and the following manufacturing process quality. Data quality assessment can be used in the camera calibration, the model and model reconstruction comparison, and so on. In this paper, on the basis of the existing method of calculating each point error, and multipurpose use of average and standard error and some other concepts of mathematical statistics, and then improve a novel and simple calculating error method. This method is applicable to many groups of one-to-one ideal data and the measured data comparison, and it can be more intuitive to reflect the error of overall data, as well as the error distribution, and it can be more efficient to determine the measured data is reasonable or not. In this paper, the data point quality which is collected in the reverse engineering is assessed, and it can see that the method which is proposed in this article has some advantages in the data point quality assessment field.

Abstract: Precise simulation of the temperature distribution throughout welding process is basic for stress analysis. In this paper, numerical simulations and multi-factor regression were used to investigate how the three process parameters, laser power, spot radius and spot offset, influence the temperature distribution in Beryllium (Be) cylindrical shells. The experiments are designed by the compound response surface method. Based on numerical results, regression model are gained as an expression about laser power, laser spot radius and laser spot offset. Then the effects of these three parameters on temperature distribution were obtained. The results could provide guidelines for welding process of Be cylindrical shells.

Abstract: Intense competition drives the need for dynamic and flexible integration of dispersed and heterogeneous information systems. This paper proposes a semantic gateway architecture for system integration in networked manufacturing to solve the semantic heterogeneity problems. The system integration mode based on semantic gateway is set up to enable unified expression and analysis of the information to be integrated, so that the flexibility and transparency of integration between heterogeneous systems are significantly improved.

Abstract: Combining element free Galerkin method with rigid/visco-plastic flow theory, the paper establishes the three-dimensional rigid/visco-plastic element free Galerkin method, and introduces it to analyze three-dimensional bulk metal forming processes. The velocity field is approximated by MLS method. Employing the incomplete generalized variation principle, stiffness matrix equation and solution formulas are derived. And STL format discrete triangular patches are used to describe the mould cavity. An analysis program for simulating three-dimensional bulk metal forming processes is developed. The program is capable of simulating three-dimensional unsteady bulk metal forming processes with severe deformation and arbitrarily shaped dies. A numerical example is analyzed. Numerical results such as material flow patterns and distributions of the effective stress are obtained. The effectiveness and validity of the proposed method and techniques are demonstrated by comparing with results obtained by using commercial finite element software.

Abstract: The reverse modeling solution and its key technologies about complex part with internal cavity are introduced in this paper, taken the casting valve body for an example. The melt silicon rubber is injected in the valve body to duplicate its internal cavity surface, which is transformed into the external surface of the concretionary silicon rubber entity. The technical hurdle of collecting internal cavity surface data is solved. The key modeling technologies are studied according to data of spot cloud collected by laser-scanning approach, data preprocessing of spot cloud based on synthetic method, respectively constructing contour curves of internal and external piping surfaces, building the sold models corresponding internal and external surfaces on basis of alignment of their coordinates. The final CAD model of valve body is created after Boolean calculation of two sold models. This technical process is be efficiently used to solve the bottleneck of the rapid design and lean development about part with internal cavity structure.

Abstract: To resolve the problems aroused by G code in manufacturing industry, a plan for NC system based on STEP-NC is proposed. The whole system is designed into two parts: system software and system architecture. With modularized design thinking, the control software includes five modules: interpreting module, man-machine interface, task coordinator, axis group module and axis module. For the system architecture, an open architecture is used which adopts different products from different manufacturers, being connected together by softSERCANS bus. By a machining test, the expected machining features are realized, proving that the NC system designed is reliable.

Abstract: In this paper, a new concept named “Closed-loop Manufacturing System” (CLMS) is proposed. The Workpiece Machining Precision PID Control Model (WMPPCM) is outlined firstly, in which PID model expressions are structured and the role of proportion, integration, differential adjustment are analyzed. Then, the experimental method of WMPPCM is established to verify the feasibility and validity of this model. In the experiment, WMPPCM could be utilized to estimate the trend of processing error so as to conduct the adjustment before production. It is also proved that WMPPCM in CLMS has a significant effect on error compensation, which builds up the theoretical foundation for paper research on CLMS in terms of WMPPCM.

Abstract: This paper presents an inverse method to derive the elastic constants of thick composite plates from the resonance frequencies of a free-edge test specimen based on modal vibration test. A mixed numerical experimental identification procedure is used for this purpose. The sum of the squared differences between the experimental frequencies and analytical frequencies from finite element method is chosen as the objective function. The optimization techniques, Hybrid Genetic /Simulated Annealing algorithm, have been applied to determine the elastic constants. As the objective function reaches its minimum, its corresponding design variables are the elastic constants of the material. The present method is applied to determine the elastic constants of AS4/PEKK material. The results indicate that different stacking sequences and numbers of frequencies have effects on the determination of elastic constants of the materials.