柜式空調(diào)下面板注塑模具三維設(shè)計(jì)與模擬仿真【說明書+CAD+PROE+仿真】

柜式空調(diào)下面板注塑模具三維設(shè)計(jì)與模擬仿真【說明書+CAD+PROE+仿真】,說明書+CAD+PROE+仿真,柜式空調(diào)下面板注塑模具三維設(shè)計(jì)與模擬仿真【說明書+CAD+PROE+仿真】,空調(diào),面板,注塑,模具,三維設(shè)計(jì),模擬,摹擬,仿真,說明書,仿單,cad,proe Journal of Mechanical Science and Technology 23 (2009) 13311341 DOI 10.1007/s12206-009-0407-3 Journal of Mechanical Science and Technology Feature-based non-manifold modeling system to integrate design and analysis of injection molding products Sang Hun Lee * School of Mechanical and Automotive Engineering, Kookmin University, Seoul, 136-702, Korea (Manuscript Received December 30, 2008; Revised January 24, 2009; Accepted January 24, 2009) - Abstract Current CAE systems used for both the simulation of the injection molding process and the structural analysis of plastic parts accept solid models as geometric input. However, abstract models composed of sheets and wireframes are still used by CAE systems to carry out more analyses more efficiently. Therefore, to obtain an adequate abstract model, designers often have to simplify and idealize a detailed model of a part to a specific level of detail and/or abstraction. For such a process, we developed a feature-based design system based on a non-manifold modeling kernel supporting feature-based multi-resolution and multi-abstraction modeling capabilities. In this system, the geometric models for the CAD and CAE systems are merged into a single master model in a non-manifold topological representation, and then, for a given level of detail and abstraction, a simplified solid or non-manifold model is extracted immediately for an analysis. For a design change, the design and analysis models are modified simultaneously. As a result, this feature- based design system is able to provide a more integrated environment for the design and analysis of plastic injection molding parts. Keywords: Injection molding product; Integration of CAD and CAE; Multi-resolution; Level of detail; Level of abstraction; Feature; Solid; Non-manifold - 1. Introduction In the area of design and manufacturing of plastic injection molding parts, various trials have been car- ried out to develop a specialized CAD system that could be used to design of plastic parts and molds 1, 2, 3 and to develop a CAE system that could be used to simulate the injection molding process to find defects before the manufacturing stage 4-6. The complete design process supported by the CAD and CAE sys- tems is illustrated in Fig. 1. At the initial design stage, the CAD system dedicated to the design of the plastic part can be used to enhance design productivity. The structural analysis and the molding process simulation using the CAE system can validate the initial design. If the simulation results do not satisfy the functional requirements, the design process is repeated by feed- ing back the simulation results to the CAD system. The design-analysis/simulation cycle is iterated until the functional requirements are satisfied. Traditionally, the geometric models used in the design stage are solid models including the feature informa- tion, whereas the models used in the analysis stage are abstract non-manifold topological (NMT) models composed of medial surfaces and axes, as illustrated in Fig. 2. The abstract NMT models are created in the CAE system using its pre-processor. Therefore, the designer must create and maintain two types of a geometric model of a part at the same time. Moreover, the process to convert a solid model into an abstract NMT model is very tedious and time-consuming. This paper was recommended for publication in revised form by Associate Editor Tae Hee Lee * Corresponding author. Tel.: +82 2 910 4835, Fax.: +82 2 910 4839 E-mail address: shleekookmin.ac.kr KSME if subtractive, the operation is difference (). 5. Idealization The idealization process for the extraction of analy- sis models consists of two stages: detail removal and dimensional reduction. The multi-resolution modeling technique for feature-based solid models 14 is adopted for detail removal at various LODs. The most advanced multi-resolution modeling technique based on the history-based selective Boolean operations is applied for detail removal. The multi-abstraction mod- eling technique for feature-based NMT models 15 is introduced for dimensional reduction at various LOAs. 5.1 Detail Removal Detail removal is the first stage of the part geometry idealization process. If the user wants to use some simplified solid models of a part to analyze the parts stress and strain distribution or to simulate the molding process, the detailed features have to be suppressed. For instance, a hole whose diameter is smaller than the mesh size is removed for molding flow simulation. The detail removal process can be explained by us- ing the example shown in Fig. 4. The process consists of the following three steps. (Step 1) User input: the user specifies the threshold values to determine whether a feature is to survive or not. Typical values are the mesh size and the fea- ture volume. (Step 2) Selection of features: the system selects the features that pass the threshold of survival. (Step 3) Selection of topological entities: The system selects the topological entities constituting the Boo- lean result. For this purpose, the system first com- poses a string of a sequence of the Boolean opera- tions with the surviving features in the original crea- tion order of the features. The model is exactly the same as that of the Boolean operations on the effec- tive volumes of the features rearranged in the order of feature significance 33. For example, if the fea- tures F0, F1, F2, F3, F8, F9 are selected, then “P0,0 + P1,0 + P2,0 + P3,0 P8,0 P9,0” is composed. Next, the string is delivered to the selection module, which selects the topological entities constituting the Boolean result and displays them on the screen. The simplified solid model can be used for a CAE system that requires CAD solid models as geometric input. If the user wants to reduce the dimensionality of the simplified solid model, he/she can execute the dimensional reduction process successively. 5.2 Dimensional Reduction If the user wants to use any abstract analysis model of a part for structural analysis or molding process simulation, the dimensional reduction process has to be executed. The criteria of LOA are application- dependent. In structural analysis, the aspect ratio is a good criterion to determine the abstraction level 24, 31. Depending on the aspect ratio, a solid object may be abstracted to a beam element or a plate element. In injection molding simulation, the ratio of the features key dimension and the mesh size can be the criterion of LOA. For instance, if the diameter of a boss is less than the mesh size, it is abstracted to a wireframe model; otherwise, it is abstracted to a sheet model. A hole is abstracted to a wireframe if its diameter is smaller than the mesh size. Eventually, these ab- stracted models are converted into FEM meshes such as linear triangles, cold/hot solid runners, cold/hot annular runners, and connectors. A linear triangle is a three-node shell mesh, and the others are all two-node beam meshes. Three node meshes are used to repre- sent the main shape and ribs of a part, and two node meshes are used to represent bosses, pins, runners, and gates. In the dimensional reduction process, the system se- lects and marks the topological entities that contribute to the construction of the abstract model for analysis. For a given LOA criterion, the system selects the ap- propriate abstract model for each feature that survived in the detail reduction process. The selection method is implemented in the class of each form feature. A string representing a sequence of the Boolean opera- S. H. Lee / Journal of Mechanical Science and Technology 23 (2009) 13311341 1339 tions performed on the selected abstract models is composed and sent to the selection module, which then marks and displays the topological entities consti- tuting the Boolean result. Fig. 6 presents the idealiza- tion results of an example part model for various LODs and LOAs. Once the idealization process is finished for mesh generation or transfer to a CAE system, a clean geo- metric model for analysis needs to be created from the selected topological entities of the merged-set model. There are two methods to create a clean analysis mod- el: one, to copy the merged set and delete the unse- lected entities, and the other, to create a new model using the NMT Euler operators. Since the former is easier than the latter, we chose the former method. Finally, this clean analysis model is transferred to CAE systems directly, or to a CAE pre-processor for mesh generation. 6. Conclusions We have proposed a new method for the integration of design and analysis models for injection molding parts using the NMT model and the multi-resolution and multi-abstraction modeling techniques. In the proposed system, various different geometric models for design and analysis are simultaneously created and merged into an NMT master part model, and for a specific level of detail and abstraction, an analysis model in solid or NMT representation is provided immediately from the master part model. In addition, the NMT B-rep allows easy implementation of the immediate deletion and interaction detection of fea- tures, which are difficult to implement in a solid mod- eler. In addition, our NMT kernel provides sheet mod- eling capabilities and the transformation function, which transforms a sheet to a solid, to facilitate model- ing of thin-walled parts. Moreover, this system, which is implemented using object-oriented programming technique, allows the user to define and add a new feature into the feature library without the need to change the source code of the existing system. There- fore, the proposed approach is expected to integrate the CAD and CAE systems for the realization of con- current engineering methodology. However, to achieve more complete integration of the CAD/CAE system, the following tasks need to be conducted as future work: (1) integration of the MAT function to overcome the limitations of the design-by- feature method, (2) enlargement of the feature library for the feeding system to include features such as gates and runners, (3) development of a more robust em- bedding method of abstract models (currently, the abstract models for an additive sub-feature are ex- tended and trimmed by the abstract models of the fea- ture to be attached), and (4) evolution of the system into a more intelligent one by adopting an expert sys- tem to evaluate the results of design and analysis. Acknowledgments This work was supported by research program 2006 Fig. 6. Idealized models for the example part. 1340 S. H. Lee / Journal of Mechanical Science and Technology 23 (2009) 13311341 of Kookmin University in Korea. References 1 C. G. 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Sheffer, Model simplification for meshing using face clustering, Computer-Aided Design, 33 (2001) 925-934. 32 VMTech, http:/www.vmtech.co.kr. 33 K. K. Wang, et al., Integration of CAD/CAM for injection-molded plastic parts, CIMP Progress Re- port, No. 13, (1987). Sang Hun Lee received his B.S., M.S., and Ph. D. degrees in Mechanical Design and Pro- duction Engineering from Seoul National University, Korea, in 1986, 1988, and 1993, respec- tively. Dr. Lee is currently a Professor at the School of Me- chanical and Automotive Engineering at Kookmin University in Seoul, Korea. His research interests include CAD/ CAM, human-centered design and engineering, digital human modeling and simulation, computer-aided automotive design and manufactur- ing., and computer-aided tooling design.