Ever since the first engineer rotated a 3-D prototype of a product on his computer screen rather than in his hand, the CAD industry has been dreaming of a seamless virtual design process.

Imagine engineering teams around the world firing up their CAD stations to start designing a new automobile. As each designer works on the various components, the car model starts to take shape. Tooling engineers collaborate on the process as they work on their own pieces of the design. When the design for the motor is complete, testing teams employ finite element analysis packages feeding the results back to the CAD engineers.

Even the marketing departments are involved. They create presentations of the car from the CAD model and display them on the company's Web site in full interactive 3-D. Feedback from the presentation influences the design. When production begins, the product is designed, the components are tested, and the marketing program is already under way.With more than ten years of effort, CAD companies have not been able to deliver this dream of a virtual design process. Ten years is an eternity in any computer-related industry.

So what's the hold up? It's certainly not the hardware. Even standard desktop computers are capable of real-time operations on complex CAD models, and CAD systems operate on state of the art equipment. And it's not the connectivity either. Intranets and the Internet connect remote sites around the world.

No, the problem is more fundamental. CAD models are large, very large. Even models of simple products can reach hundreds of megabytes in size. During the virtual design process these gigantic models have to be transmitted across the already overburdened wires of the Internet, and that's just been impossible - until now.Over the past few years, a new technology has emerged that has the potential to realize the virtual design process.

The technology is streaming 3-D, and it is already solving major problems in the CAD industry. Streaming 3-D allows 3-D data, like the data composing CAD models, to be transmitted across networks incrementally rather than all at once. As a user views and manipulates a model, the streaming 3-D technology automatically downloads the portions the user can see. This technique allows a user to operate on highly complex models right over the Internet.Suppose a plant design firm is designing a factory for a client. The firm wants to display the factory design in 3-D on their Web site so that the client can view the work in progress.

The CAD file representing the factory is over 500 megabytes. The client cannot view the design because downloading 500 megabytes over the Internet is unworkable. But, why should the client download the entire factory, when he can only see a small portion at any given time? A streaming 3-D technology only needs to download the portions of the factory that the client can see.For example, as the client navigates through the factory, a piece of machinery comes into view. This machinery is first downloaded and displayed at low detail.

As the user approaches the machinery, additional detail is downloaded, and the visual quality of the machinery improves. Relatively little data is required to display any particular view of the factory. For this reason, streaming 3-D allows the user to navigate through the 500-megabyte factory model over an extremely slow network connection, such as a 28.8 Kbps modem.Screen shot using SolidWorks; courtesy of RealityWave IncToday, applications use streaming 3-D technology to allow CAD engineers to show their designs to people all over the world.

A prototype that used to take days to ship to a client by mail can now be shown during a phone call. Companies can replace flat, 2-D pictures on their Web sites with interactive 3-D models of their products. Customers can view the company's product line on a Web site in 3-D, examine the construction of the products, and make a purchase. If the product requires assembly, the customer can use that same 3-D model as a guide.

A CAD model is no longer used just in development, but also in marketing, sales, support and training activities. By expanding the use of the CAD model, companies increase the return on their investment in CAD.Streaming 3-D is even being used for real-time collaboration. While an engineer is working on a CAD model, other people around the world can see the model as the designer is making changes. Together with the engineer, these remote participants form a collaboration team. Any member of the team can synchronize his 3-D view of the model with the other team members.

Members can also mark points of interest on the model and show those points to other team members. If the engineer makes a change to the model, all team members see that change as it is made.All of this collaboration takes place in real-time while the team members are speaking to each other in a conference call. By increasing the interaction between team members, a company can slash its design cycle and time to market by months.

This form of real-time collaboration is as close as the industry has come to a truly virtual design process.Streaming 3-D technology has opened the bottleneck that has hindered the advancement of the CAD industry for years. CAD companies are now integrating streaming 3-D as part of their comprehensive Internet strategies. From 3-D products on Web sites to real-time collaboration, streaming 3-D is bringing the CAD industry into the age of the Internet. Virtual product design as it was envisioned 10 years ago is not yet a reality.

But now it will be, soon.Rapid PrototypingWe could also consider holographic CAD, The image could be solid in design with 3 dimensional views, using a remote pen we could make adjustments and move things around, while walking around the image.For factory layouts we could design and then transfer the holographical image to the shop floor and walk around it to spot any potential problems.We could also use virtual reality to design, but we must consider that if we are able to do this, would we become prisoners of our own designs? Would we enter our pods and never want to leave a world we had designed in our own image.Therefore we must ask ourselves, could the future of CAD design be a way of extenuating an already unsociable society into a society of hermits, maybe not to that extreme but it would be easy to get wrapped up in our own manufactured desires.The above is closely linked with Rapid Prototyping, except that instead of making a 3D model we use holograms instead, this will save on materials, energy and environment.

There are a lot of CAD systems on offer now, from the basic wire frame to 3D solid Modelling and systems that can be sent to a milling machine to make a model (Rapid Prototyping).We can use PEPs to design, try the design in simulation mode before sending the programme to the machine.So what is Rapid Prototyping in detail and how does it relate to CAD:The term rapid prototyping (RP) refers to a class of technologies that can automatically construct physical models from Computer-Aided Design (CAD) data. These "three dimensional printers" allow designers to quickly create tangible prototypes of their designs, rather than just two-dimensional pictures. Such models have numerous uses.

They make excellent visual aids for communicating ideas with co-workers or customers. In addition, prototypes can be used for design testing. For example, an aerospace engineer might mount a model airfoil in a wind tunnel to measure lift and drag forces. Designers have always utilized prototypes; RP allows them to be made faster and less expensively.At least six different rapid prototyping techniques are commercially available, each with unique strengths. Because RP technologies are being increasingly used in non-prototyping applications, the techniques are often collectively referred to as solid free-form fabrication, computer automated manufacturing, or layered manufacturing.

The latter term is particularly descriptive of the manufacturing process used by all commercial techniques. A software package "slices" the CAD model into a number of thin (~0.1 mm) layers, which are then built up one atop another. Rapid prototyping is an "additive" process, combining layers of paper, wax, or plastic to create a solid object. In contrast, most machining processes (milling, drilling, grinding, etc.

) are "subtractive" processes that remove material from a solid block. RP's additive nature allows it to create objects with complicated internal features that cannot be manufactured by other means.Of course, rapid prototyping is not perfect. Part volume is generally limited to 0.125 cubic meters or less, depending on the RP machine.

Metal prototypes are difficult to make, though this should change in the near future. For metal parts, large production runs, or simple objects, conventional manufacturing techniques are usually more economical. These limitations aside, rapid prototyping is a remarkable technology that is revolutionizing the manufacturing process.The Basic ProcessAlthough several rapid prototyping techniques exist, all employ the same basic five-step process. The steps are:1. Create a CAD model of the design2.

Convert the CAD model to STL format3. Slice the STL file into thin cross-sectional layers4. Construct the model one layer atop another5. Clean and finish the modelCAD Model Creation: First, the object to be built is modeled using a Computer-Aided Design (CAD) software package.

Solid modelers, such as Pro/ENGINEER, tend to represent 3-D objects more accurately than wire-frame modelers such as AutoCAD, and will therefore yield better results. The designer can use a pre-existing CAD file or may wish to create one expressly for prototyping purposes. This process is identical for all of the RP build techniques.Conversion to STL Format: The various CAD packages use a number of different algorithms to represent solid objects. To establish consistency, the STL (stereolithography, the first RP technique) format has been adopted as the standard of the rapid prototyping industry. The second step, therefore, is to convert the CAD file into STL format.

This format represents a three-dimensional surface as an assembly of planar triangles, "like the facets of a cut jewel." 6 The file contains the coordinates of the vertices and the direction of the outward normal of each triangle. Because STL files use planar elements, they cannot represent curved surfaces exactly. Increasing the number of triangles improves the approximation, but at the cost of bigger file size. Large, complicated files require more time to pre-process and build, so the designer must balance accuracy with manageablility to produce a useful STL file.

Since the .stl format is universal, this process is identical for all of the RP build techniques.Slice the STL File: In the third step, a pre-processing program prepares the STL file to be built. Several programs are available, and most allow the user to adjust the size, location and orientation of the model. Build orientation is important for several reasons. First, properties of rapid prototypes vary from one coordinate direction to another.

For example, prototypes are usually weaker and less accurate in the z (vertical) direction than in the x-y plane. In addition, part orientation partially determines the amount of time required to build the model. Placing the shortest dimension in the z direction reduces the number of layers, thereby shortening build time. The pre-processing software slices the STL model into a number of layers from 0.01 mm to 0.

7 mm thick, depending on the build technique. The program may also generate an auxiliary structure to support the model during the build. Supports are useful for delicate features such as overhangs, internal cavities, and thin-walled sections. Each PR machine manufacturer supplies their own proprietary pre-processing software.Layer by Layer Construction: The fourth step is the actual construction of the part. Using one of several techniques (described in the next section) RP machines build one layer at a time from polymers, paper, or powdered metal.

Most machines are fairly autonomous, needing little human intervention.Clean and Finish: The final step is post-processing. This involves removing the prototype from the machine and detaching any supports. Some photosensitive materials need to be fully cured before use. Prototypes may also require minor cleaning and surface treatment.

Sanding, sealing, and/or painting the model will improve its appearance and durability.As mentioned previously CAD can be used in conjuncion with many applications, but as a summary with some things not previously mentioned: for example you can convert text into PDF file formats, You can use CAD to do design and then send to machines to do Rapid Prototyping, the possibilities are endless and the future is of CAD is a never ending amount of possibilities, and with all new software, they are trying to make the add on's more versatile and user friendly, while being flexible with most CAD applications.