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Chapter 14 Symmetrical Features in Designs
Learning Objectives: Create Revolved Features Use the Mirror Feature Command Create New Borders and Title Blocks Create Circular Patterns Create and Modify Linear Dimensions Use Autodesk Inventor's Associative
Functionality Identify Symmetrical Features in Designs
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Introduction
Feature-based parametric modeling enables us to build complex designs by working on smaller and simpler units. This approach simplifies the modeling process and allows us to concentrate on the characteristics of the design. Symmetry is an important characteristic that is often seen in designs. Symmetrical features can be easily accomplished by the assortments of tools that are available in feature-based modeling systems.
The modeling technique of extruding two-dimensional sketches along a straight line to form three-dimensional features, as illustrated in the previous chapters, is an effective way to construct solid models. For designs that involve cylindrical shapes, shapes that are symmetrical about an axis, revolving two-dimensional sketches about an axis can form the needed three-dimensional features. In solid modeling, this type of feature is called a revolved feature.
In Autodesk Inventor, besides using the Revolve command to create revolved features, several options are also available to handle symmetrical features. For example, we can create multiple identical copies of symmetrical features with the Feature Pattern command, or create mirror images of models using the Mirror Feature command.
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Modeling Strategy
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Linear Diameter
To create a dimension that will account for the symmetrical nature of the design: pick the axis of symmetry, pick the entity, select Linear Diameter in the option menu, and then place the dimension.
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Creating A Revolved Feature
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Mirroring Features
In Autodesk Inventor, features can be mirrored to create and maintain complex symmetrical features. We can mirror a feature about a work plane or a specified surface. We can create a mirrored feature while maintaining the original parametric definitions, which can be quite useful in creating symmetrical features. For example, we can create one quadrant of a feature, then mirror it twice to create a solid with four identical quadrants.
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Construction GeometryIn Autodesk Inventor, we can also use construction geometry to help define, constrain, and dimension the required geometry. Construction geometry can be lines, arcs, and circles that are used to line up or define other geometry, but are not themselves used as the shape geometry of the model. When profiling the rough sketch, Autodesk Inventor will separate the construction geometry from the other entities and treat them as construction entities. Construction geometry can be dimensioned and constrained just like any other profile geometry. When the profile is turned into a 3D feature, the construction geometry remains in the sketch definition but does not show in the 3D model. Using construction geometry in profiles may mean fewer constraints and dimensions are needed to control the size and shape of geometric sketches.
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A Pattern Leader
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Circular Pattern In Autodesk Inventor, existing features can be easily duplicated. The Pattern command allows us to create both rectangular and polar arrays of features. The patterned features are parametrically linked to the original feature; any modifications to the original feature are also reflected in the arrayed features.
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Defining a New Border and Title Block
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Creating a Section View
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Associative Functionality
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