Lab Report
The objective of this paper is to illustrate the experiences in the classroom during the demonstration of a pilot section.
Introduction
The Engineering Design Graphics (EDG) course included the engineering analysis for incorporating the new CAD component in to the computer laboratory. The students were required to construct two solid models that match in terms of their profiles, however they differ slightly in terms of their geometry as shown below:
Figure 1: Rocker arm solid model of the rocker arm used for studying, producing, and comparing .MPR files (mass-properties report files).
The students used the solid model and applied a material property to it for producing .MPR files for each of the two models. The typical AutoCAD example is shown below:
The object given in the figure below is an example of solid modeling. A solid model refers to a clear and complete illustration of an absolutely filled and enclosed volume of a solid object consisting of surfaces, edges, vertices or nodes, volume and weight.
Figure 2: The object constructed through CSG by using the Boolean Operations
The above object can be constructed through the three methods of solid modeling, which are: Boundary Representation that uses finite element programs, Constructive Solid Geometry such as the 3-D modeler of AutoCAD, Unigraphics, etc., and Parametric Modeling, for example, SolidWorks, AutoCAD-s Inventor, Unigraphics and Pro-Engineering.
In order to obtain the object in the above figure 2, the students used the Constructive Solid Geometry technique of solid modeling with help of the Boolean operations for integrating the basic primitive solid shape and the generated solid shape together. The basic primitive solid shapes are: cube, cylinder, sphere cone, triangular prism (wedge and block), and donut or torus. The three fundamental types of the Boolean operations are: Union, Subtract and Intersection.
Procedure
This figure 3 shows the examples of such two dimensional objects that were chosen because they are most receptive to a Finite Element Analysis (FEA) as well as to an interpretation of the CAD training of students at this initial stage.
Figure 3: The two dimensional object design for use in geometric modeling, reverse engineering, and geometric analysis.
Every group of the students had these tools with them: a pencil, a scale, a set of clippers and grid paper. The groups used the techniques of reverse engineering to draw the full size outline of the selected two dimensional objects by directly measuring the dimensions of the object. This drawing will then be used as the engineering document to construct the objects’ respective geometric model. The students first prepared a solid model of the objects through its reverse engineering sketch in order to take the piece of a section from its two dimensional design for the purpose of applying the FEA on it with the help of the two dimensional program of AutoFEA running within the AutoCAD software.
Results & Discussion
The above process involves the application of the known loads to certain points on the models so as to acquire the color contours for showing the outcomes of the FEA, as shown below:
Figure 3: Application of loads to the two dimensional design object used FEA.
Figure 4: Outcomes obtained from the FEA of the two dimensional object by the AutoFEA program within the AutoCAD.
The students’ groups qualitatively examined the acquired results for determining the points of optimum stresses for the purpose of suggesting ways for the modification of the geometry of the given design object so that the obtained optimum stresses could be reduced.
Conclusion
The results obtained indicate that a CAD/CAM component can be effectively used in the EDG lab. This further infers that the CAD/CAM component illustrates the contemporary technique towards the engineering design and will, in turn, develop a better apprehension of the concurrent engineering environment. Thus, it is thereby concluded that the CAD/CAM component should be added in to the curriculum of Engineering Design Graphics.
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