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1、名师精编优秀教案Teaching Plan -6: Geometry modeling Learning Outcomes On the completion of this unit you will be able to correctly grasp the following knowledge as follows: ?The concept and the importance of Geometric modeling. ?Three-dimensional models type and their use. ?The methods of Geometric construc
2、tion ?The types of Free form surfaces ?The concept of constraints based modeling and its process Assessment Competency will be assessed by grasping the knowledge throughout this section. Resources Theory (Period: 2 classes in classroom) CAD/CAM Principles and Applications?Chapter 4: Geometric Modeli
3、ng (only 4.1-4.4) Key Point geometric modeling, the line model, the surface model, the solid or volume model, geometric construction, free form surfaces, constraints based modeling 名师精编优秀教案Geometric modeling Geometric modeling is the important base of the total product cycle in the manufacturing env
4、ironment. The mind of design can bring along a lot of continued concepts or functions. If the designer s mind is to be translated into reality, a relevant test and manufacture should be done on the design. And the preliminary designs can be developed or improved based on the market research and prod
5、uct feedback. Geometric modeling is the central part of all the activities. Design analysis: Evaluation of inertial properties, areas and volumes Interference checking in assemblies Analysis the tolerance build-up in assemblies Analysis of kinematics mechanics, robotics Automatic mesh generation for
6、 finite element analysis Drafting: Planar cross section Hidden line and surface removal Production of shaded images Dimensioning Creation of exploded views for technical illustrations Manufacturing: Parts classification Process planning Numerical control data generation and verification 名师精编优秀教案Robo
7、t program generation Production engineering: Bill of materials Material requirement Manufacturing resource requirement Scheduling Inspection and quality control: Program generation for inspection machines Comparison of produced part with design The geometric modeling technique would provide faciliti
8、es for the all type of applications. The geometric models can be broadly categorized into two types: Two-dimensional models Three dimensional models The two-dimensional models were the first ones to be developed in view of their relatively lesser complexity. Their ability has more inherent difficult
9、y in representing complex objects. Their utility lies in many of the low end drafting, or in representing essentially two-dimensional manufacturing applications such as simple turning jobs, sheet metal punching , flame cutting or laser cutting. The three-dimensional geometric modeling has the abilit
10、y to provide all the information required for the manufacturing applications. Three-dimensional models type There are a number of ways in which the three-dimensional representation can be arrived at: The line model The surface model The solid or volume model The line model is the simplest and is use
11、d in low-cost designing system. It is also called the wire frame represented. The complete object is represented by a 名师精编优秀教案number of lines with their end point coordinates(x, y, z) and their connectivity relationships. Though it appears simple, there is an ambiguity possible as it is difficult to
12、 understand the outside represented by the wire frame model. The line model is inadequate for representing the more complex solids and it is also possible to draw some impossible solid object. The surface model is constructed essentially from surfaces such as planes, rotate curve surface and very co
13、mplex surfaces. It has clearly representing of the solid from the manufacturing point of view. This type model without the interior is available to generate the NC cutter data. But the calculation of the properties such as mass or inertia would be difficult. This model is extremely tedious and is no
14、t generally attempted. But the facilities would be used when the model s surfaces are non-analytical and sculptured surfaces such as those used for modeling the car bodies and ship-hulls. The solid or volume model consisting of the complete description of the solid in a certain form is the most idea
15、l representation, as all the information required for manufacturing can be obtained with this technique. It is most widely used. the line model the surface model the solid or volume model Automatic view generation Cross-section Manually guided Manually guided Elimination of the hidden details Manual
16、ly guided Maybe Analysis functions Numerical control application Geometric construction methods The production drawing consists of a lot of information besides the simple view or the geometric representation: the dimension, tolerance, material specification, the processing requirement, assembly requirement, etc. It is the incumbent on the geometry construction method employed to make use of the normal information available at the design state and also as simple as possible in construction. 名师精编优
