Three dimensional (3D) CAD (computer-aided-design) models have enabled major productivity gains in product design and engineering. Prior to the advent of economical desktop computers skilled draftsmen spent hours laboring with graphite lead pencils on velum and Mylar to achieve engineering quality documentation for fabrication and production manufacturing. The process required tedious checking to eliminate errors wherein modification required erasures and redrawing over and over on the same sheet. Large projects had many drawing documents linked to one another that required procedural revisions and archiving.
Two dimensional (2D) CAD (computer-aided-design) was a great step forward in moving from the drafting table to the desktop computer. The graphical display capabilities of the desktop computer enabled a user to graphically draft using mouse, keyboard strokes, text line commands, and tablet with stylus. Each CAD system had its own (UI) User Interface. While manual drafting may have actually been faster in the early years, two dimensional (2D) CAD (computer-aided-design) technologies allowed endless changes to be made with sharp clean printed copies printed without limitation. It was easy to export the CAD drawings in PDF format for viewing and printing on any non-licensed computer.
Three dimensional wire framing was the next step in CAD wherein two dimensional (2D) sections was given depth to extrude, sections were revolved around an axis and swept along trajectories to create 3D forms. Surface modeling was another advancement wherein surface skins were created using typical wire framing three dimensional commands. Solid modeling was the biggest advancement in three dimensional (3D) CAD (computer-aided-design). Solid models could be created using similar commands from surface modeling and wire framing but the result was that the model took on mass properties useful for analysis, sectioning, and Boolean operations of merging for adding, subtracting, and merging.
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Sunday, June 7, 2009
Rapid Prototyping
One of the most powerful advantages associated with CAD modeling is the ability to create physical 3D prototypes of the design using the actual CAD model data itself. These prototypes can be used to evaluate the shape of the product for aesthetics or ergonomics, testing and verifying component performance, and to ensure part fits and function before committing to production tooling, such as injection molds and die casting dies.
The prototypes can be produced quickly and inexpensively, usually within a few days and for a few hundred dollars, more or less depending on the size of the parts and the number needed. And because they are made directly from the CAD models themselves, any design mistakes made, such as interference between parts or omitted features, can be corrected in the CAD model. Then a new set of prototypes can be produced to verify the corrections.
It is not uncommon to use several prototype "builds" during the development process to evaluate the design at different stages. For example, non-functional industrial design models may be used for trade show demonstrations or marketing research to define shapes and colors. Later, functional models can provide test data to verify mechanical design. Finally, the CAD files can be released for injection molding or die casting with only small adjustments required for overall part qualification.
In general, prototypes are made in either plastic or metal, with plastic being used much more often due to lower cost and the comparable similarities with injection molded parts. The plastics used are either liquid photopolymer, powdered thermoplastics, or extruded thermoplastic filament depending on the process. The metals used are very fine metal powders, and include copper alloys, stainless steels and others. For die cast part verification, either process can be used to verify dimensional accuracy, and plating is available to give some plastics the look and feel of metal.
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The prototypes can be produced quickly and inexpensively, usually within a few days and for a few hundred dollars, more or less depending on the size of the parts and the number needed. And because they are made directly from the CAD models themselves, any design mistakes made, such as interference between parts or omitted features, can be corrected in the CAD model. Then a new set of prototypes can be produced to verify the corrections.
It is not uncommon to use several prototype "builds" during the development process to evaluate the design at different stages. For example, non-functional industrial design models may be used for trade show demonstrations or marketing research to define shapes and colors. Later, functional models can provide test data to verify mechanical design. Finally, the CAD files can be released for injection molding or die casting with only small adjustments required for overall part qualification.
In general, prototypes are made in either plastic or metal, with plastic being used much more often due to lower cost and the comparable similarities with injection molded parts. The plastics used are either liquid photopolymer, powdered thermoplastics, or extruded thermoplastic filament depending on the process. The metals used are very fine metal powders, and include copper alloys, stainless steels and others. For die cast part verification, either process can be used to verify dimensional accuracy, and plating is available to give some plastics the look and feel of metal.
read more
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