Solid Modelling Basic Concepts Solid Modeling CAD

Solid modelers have become commonplace in engineering departments in the last ten years due to faster pc's and competitive software pricing. They are the work horse of machine designers.

Solid modeling software creates a Virtual Reality for machine design and analysis. Interface with the human operator is highly optimized and includes programmable macros, keyboard shortcuts and dynamic model manipulation. The ability to dynamically re-orient the model, in Real-time shaded 3-D, is emphasized and helps the designer maintain a mental 3-D image.

The designer generally has access to models that others are working on concurrently. For example, several people may be designing one machine that has many parts. New parts are added to an assembly model as they are created. Each designer has access to the assembly model, while a work in progress, and while working in their own parts. The design evolution is visible to everyone involved.

A solid model generally consists of a group of features, added one at a time, until the model is complete. Engineering solid models are built mostly with sketcher-based features; 2-D sketches that are swept along a path to become 3-D. These may be cuts, or extrusions for example.

Another type of modeling technique is 'surfacing'. Here, surfaces are defined, trimmed and merged, and filled to make solid. The surfaces are usually defined with datum curves in space and a variety of complex commands. Surfacing is more difficult, but better applicable to some manufacturing techniques, like injection molding. Solid models for injection molded parts usually have both surfacing and sketcher based features.

Another example of where surfacing excels is automotive body panels. If two curved areas of the panel have different radii of curvature and are blended together, tangency won't be enough. They need to have a contunious rate of curvature change between the two sections for proper belnding appearance.

The learning curve for these software packages is steep, but a fluent machine designer who can master these software packages is highly productive.

3 Parametric solid modeling

A revolution in 3-D cad began in 1989 when the first parametric modeler, T-FLEX was released for the pc. Pro/ENGINEERPro/ENGINEER (commonly "Pro/e" or "Pro") is a 3D Solid modeling CAD program created by PTC. Pro/e is a state of the art mechanical design tool. It is a highly capable and program for creating complex 3D Models. Since the 2002 release of Pro/Engineer, whic was released the same year. Most solid modelers are now parametric.

Parametric modeling uses parameters to define a model (dimensions, for example). The parameter may be modified later, and the model will update to reflect the modification.

Example: a shaft is created by extruding a circle 100mm. A hub is assembled to the end of the shaft. Later, the shaft is modified to be 200mm long (click on the shaft, select the length dimension, modify to 200). When the model is updated the shaft will be 200mm long, the hub will relocate to the end of the shaft to which it was assembled, the engineering drawings and mass properties will reflect all changes automatically.

Examples of parameters are; dimensions used to create model features, material density, formulas to describe swept features, imported data (that describe a reference surface, for example).

Parametric modeling is obvious and intuitive. But for the first three decades of cad this was not the case. Modification meant re-draw, or add a new cut or protrusion on top of old ones. Dimensions on engineering drawings were created, instead of shown.

Parametric modeling is very powerful, but requires more skill in model creation. A complicated model for an injection molded part may have a thousand features, and modifying an early feature may cause later features to fail. Skillfully created parametric models are easier to maintain and modify.

Parametric modelling also lends itself to data re-use. A whole family of capscrews can be contained in one model, for example.

Animation of a computer generated character is an example of parametric modeling. Jar_Jar_BinksJar Jar Binks is a fictional character in the Star Wars movies The Phantom Menace Attack of the Clones and the yet to be released Revenge of the Sith''. His primary role was to be comic relief--based on his gangly way of walking, and his unique speech acc is described by parameters which locate key body positions. The model is then built off these locations. The parameters are modified, and the model rebuilt, for each frame to create animation.

4 Medical solid modeling

Modern computed axial tomographyComputed axial tomography (CAT computer-assisted tomography computed tomography CT or body section roentgenography is the process of using digital processing to generate a three-dimensional image of the internals of an object from a large series of two-di and magnetic resonance imagingMagnetic resonance imaging MRI is a method of creating images of the inside of opaque organs in living organisms as well as detecting the amount of bound water in geological structures. It is primarily used to visualise pathological or other physiological scanners can construct solid models of interior body features.

Uses of medical solid modeling;

Visualization
Visualization of specific body tissues (just blood vessels and tumor, for example)
Creating solid model data for rapid prototyping (to aid surgeons preparing for difficult surgeries, for example)
Combining medical solid models with CAD solid modeling (design of hip replacement parts, for example)

5 See also

6 External links

6.1 Commercial Solid Modelers

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Home > Solid modelling

1 Basic concepts

2 Solid modeling CAD

3 Parametric solid modeling

4 Medical solid modeling

5 See also

6 External links

6.1 Commercial Solid Modelers

Topics: Solid Modelling, Basic Concepts, Solid Modeling CAD...