3.4 Computer Aided Design

Surface models are photo-realistic images of a product, offering some machining data but no data about the interior of the product.

Solid models are clear representations of the final product. They provide a complete set of data for the product to be realized including internal dimensions and volume.

A data model explicitly determines the structure of data or structured data including statistical modelling.

Typical data models include databases and information systems.

Virtual prototyping involves the use of surface and solid modelling to develop photo-realistic interactive models. These can be considered digital mock-ups.

When designing using a “bottom-up” strategy, the designer creates part geometry independent of the assembly or any other component. Although some design criteria are often established before modelling the part, this information is not shared between models. Once all part models are completed, they are brought together for the first time in the assembly. For example, the process by which the Mars rover Curiosity was created followed a “bottom-up” strategy.

Place existing parts and subassemblies into an assembly file, positioning components by applying assembly constraints, such as mate and flush. If possible, place the components in the order in which they would be assembled in manufacturing.

“Top-down” design is a product-development process obtained through 3D, parametric and associated CAD systems.

The main feature of this method is that the design originates as a concept and gradually evolves into a complete product consisting of components and sub-assemblies.

“Top-down” begins with the design criteria and create components that meet those criteria. Designers list known parameters and create an engineering layout. The layout can be a 2D design that evolves throughout the design process as shown in the following image.

Digital humans are computer simulations of a variety of mechanical and biological aspects of the human body. They can be used to interact with a virtual prototype. Human simulation in product design enables a product to be developed more quickly, as there can be more design iterations in less time. This results in higher product quality that meets human requirements more accurately. Digital prototypes are cheaper to produce than physical prototypes. Products are safer as a result of more thorough analysis of safety aspects. Improved productivity results from enhanced automation of the development process.

Motion capture is the recording of human and animal movement by any means, for example, by video, magnetic or electro-mechanical devices.

A person wears a set of acoustic, inertial, LED, magnetic or reflective markers at each joint. Sensors track the position of the markers as the person moves to develop a digital representation of the motion.

Motion capture saves time and creates a more natural movements than manual animation.

Haptic technology is a technology that interfaces the user via a sense of touch. Also known as force feedback technology, haptic technology works by using mechanical actuators (motor) to apply forces to the user.

By simulating the physics of the user’s virtual world, it is possible to compute these forces into real time. Haptic technology allows the user to become part of a computer simulation and to interact with it, enabling the designer to observe the user’s performance and to design a better outcome. It can also be used in situations where it is difficult to train in the real environment.

Haptic technology is also used in feedback devices used in home entertainment consoles.

Virtual reality is the ability to simulate a real situation on the screen and interact with it in a near-natural way.

Can also use VR Goggles and gloves to aid interaction

Animation is the ability to link graphic screens together in such a way as to simulate motion or a process.

Finite element analysis involves the calculation and simulation of unknown factors in products using CAD systems, for example, simulating stresses within a welded car part. (virtual model)

Uses colour indication to show:

-Structural load (stress and strain)

-Aerodynamics

-Thermodynamics