Materials Science Forum Vols. 505-507

Abstract: In this study, elastic buckling criteria for die fins during extrusion of complex-shaped parts are analytically derived. In this analytical model, the fins of the extrusion die are regarded as cantilever beams with a narrow rectangular cross section. The load intensity acting on each fin is assumed to be distributed uniformly, which is quite similar to the actual distribution. The elastic critical load intensity of buckling is successfully obtained by solving simultaneously the moment equilibrium differential equations. A commercial finite element package “DEFORM 3D" is also employed to simulate the flow pattern of the billet inside the die in extrusion of a CPU heat sink. The stress distribution pattern on the fins of the extrusion die is discussed.

Abstract: A structured light pattern can be used to acquire the range data of an object from a single camera for 3-D imaging systems and it can be used for practical applications in a dynamic environment, i.e., a scene with moving objects. This paper illustrates the generation of a class of distinct structured light patterns with various sizes (range image points).

Abstract: This paper studies the phase transitions of Cu and Ni alloys as they cool from melting temperature to room temperature under high-pressure conditions. The interatomic forces acting between the atoms are modeled by the tight-binding potential. Control over the environmental pressure and the cooling temperature is maintained by a canonical ensemble (N, P, T) system. The numerical results confirm that the metal phase transition is influenced significantly by the pressure conditions, even in the case of pure Cu and Ni metals. Three specific transition pathways are identified for the Cu and Ni alloys as they cool from melting temperature to room temperature, namely a transition at the melting temperature to a crystalline structure, a transition at the glass transition temperature to a glass (amorphous) structure, and finally solidification at the melting temperature followed by a subsequent transition at the glass transition temperature. The results reveal that glass transition generally occurs at lower pressures in alloys with higher Cu compositions, while glass transition following prior solidification tends to takes place at higher pressures in alloys with higher Ni compositions.

Abstract: In this paper, a method for determining the approximated minimum-bounding box is presented. This method can only be used in the model that has finite vertices. A concept of the minimum span is introduced to determine one length of the bounding box according to a flush edge. After calculating a minimum span, the minimum-area rectangle of the projection is required to be one candidate of minimum-bounding boxes. In many applications, the volume of the bounding box is requested as small as possible. This paper provides an additional property to keep both one length and one rectangle of the bounding box are as small as possible.

Abstract: The contour of a two dimensional plate with a rectangular cavity was predicted by the linear least-squares error method. In the analysis process the heat conduction equation and the boundary conditions were discretized to form a linear matrix equation. On the basis of the concept of a virtual area, the unknown contour of the two dimensional plate was converted into virtual boundary temperatures that can be definitely expressed. Under the condition that the solution form and the initial values didn’t need to be preset, the contour of the two dimensional plate was predicted from temperatures of some points in the plate by only two inverse processes. The results show that even though the positions of the measured points are different the temperature field of the whole virtual system doesn’t change. When the number of the measured points is decreased or the measurement error is increased, the error of the prediction will increase. With reasonable measurement error, the geometry of the plate can be successfully predicted from a few measured points by the method proposed in this work.

Abstract: Manufacturing engineering education is science & technology based subjects that are traditionally the hardest to teach online because of the need for providing practice & hands-on experiences at a distance. Therefore, this research aims to develop an e-learning system to teach manufacturing technology and to enhance the quality, scale, and breadth of technological education. The major results of this research are; (1).Establish interactive on-line teaching material for the computer-aided manufacturing courses including CNC coding method, CNC simulation. (2).Propose the interactive teaching strategies for the students to learn machining process planning through web-based learning system. (3).Integrate multi-media and virtual laboratory in the developed interactive e-learning system to enhance the effectiveness of machining education through web-based system. (4). Enhance students the ability to extract the manufacturing features from a mechanical drawing in either 2D or 3D. (5). Cultivate the principle of manufacturing process planning through the developed interactive web-based learning system. (6). Discipline CNC programming and CNC machining techniques through Internet.

Abstract: Manufacturing execution system (MES) is a computer application system that integrates all relevant real-time information along every step in a manufacturing process. MES is essential for manufacturers for gathering real-time production line information, supporting manufacturing decision making and increasing manufacturing efficiency. MES is a must for operation control and lot tracking in the shop floor of a plant with complicated manufacturing processes, such as semiconductor manufacturing fab or TFT-LCD manufacturing plant. This paper presents the formulization of performance measurement of implementing MES from several quantitative and qualitative aspects by analyzing the basic functions and objectives of MES and interviewing with some senior consultants and MES related working staff. In addition, multi-attribute decision making technique, analytic hierarchy process (AHP) is used to decide the priority of these performance measurement indices. The results of this research will be useful for a company when MES is an existing system or is a To Be system.

Abstract: The surface mounting of electronic component is the major manufacturing technology for the electronic products in the last decade. The surface mounting technology (SMT) is an assembly process that assembles the surface mountable component (SMC) and the printed circuit board (PCB) together. The SMT mounter is an automatic assembly machine that processes the SMT assemblies in terms of the optical positioning and robotic handling. The SMT assembly consists of calibrating printed circuit board (PCB); vacuuming components form feeder stations; compensating the orientation of the vacuumed surface mountable component (SMC); and finally placing SMC chips on the PCB. In order to increase the throughput, the synchronous batch vacuuming of SMC components is designed. In addition, different types of component feeding and mixing in each batch increase the difficulties of finding the best component mounting sequence. In this paper, the optimal component placement scheduler is desired to perform higher assembly performance and to reduce the cycle time. The proposed optimal component placement scheduler is developed based on the rule based heuristic search approach. In addition, to evaluate the cycle time of each heuristic search, the route oriented Petri nets (ROPN) based SMT assembly models are constructed. The optimal component placement scheduler can be further determined in terms of evaluating the ROPN SMT assembly models. Finally, the practical test PCB board data is discussed in this paper.

Abstract: During design and implementation of the automatic materials handling system (AMHS) for a local 300mm semiconductor wafer fab (semiconductor fabrication plant), we observed and found an interesting phenomenon
Vehicle Clustering Phenomenon (VCP) from the dynamics of automated vehicles: As time evolves, the distance between any two adjacent vehicles usually becomes very close enough as if all the vehicles are a long train of vehicles running around the loop. The overall performance thus deteriorates due to this phenomenon. This paper explores the causes of the VCP problem and clarifies its impacts to automatic materials handling operations in 300mm semiconductor manufacturing.