Lesson 8

Read the text: Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) - ADVANTAGES AND DISADVANTAGES

Modeling with CAD systems offers a number of advantages over traditional drafting methods that use rulers, squares, and compasses. For example, designs can be altered without erasing and redrawing. CAD systems also offer "zoom" features analogous to a camera lens, whereby a designer can magnify certain elements of a model to facilitate inspection. Computer models are typically three dimensional and can be rotated on any axis, much as one could rotate an actual three dimensional model in one's hand, enabling the designer to gain a fuller sense of the object. CAD systems also lend themselves to modeling cutaway drawings, in which the internal shape of a part is revealed, and to illustrating the spatial relationships among a system of parts.

To understand CAD it is also useful to understand what CAD cannot do. CAD systems have no means of comprehending real-world concepts, such as the nature of the object being designed or the function that object will serve. CAD systems function by their capacity to codify geometrical concepts. Thus the design process using CAD involves transferring a designer's idea into a formal geometrical model. Efforts to develop computer-based "artificial intelligence" (AI) have not yet succeeded in penetrating beyond the mechanical—represented by geometrical (rule-based) modeling.

Other limitations to CAD are being addressed by research and development in the field of expert systems. This field is derived from research done in AI. One example of an expert system involves incorporating information about the nature of materials—their weight, tensile strength, flexibility, and so on—into CAD software. By including this and other information, the CAD system could then "know" what an expert engineer knows when that engineer creates a design. The system could then mimic the engineer's thought pattern and actually "create" more of the design. Expert systems might involve the implementation of more abstract principles, such as the nature of gravity and friction, or the function and relation of commonly used parts, such as levers or nuts and bolts. Expert systems might also come to change the way data are stored and retrieved in CAD/CAM systems, supplanting the hierarchical system with one that offers greater flexibility. Such futuristic concepts, however, are all highly dependent on our abilities to analyze human decision processes and to translate these into mechanical equivalents if possible.

One of the key areas of development in CAD technologies is the simulation of performance. Among the most common types of simulation are testing for response to stress and modeling the process by which a part might be manufactured or the dynamic relationships among a system of parts. In stress tests, model surfaces are shown by a grid or mesh, that distort as the part comes under simulated physical or thermal stress. Dynamics tests function as a complement or substitute for building working prototypes. The ease with which a part's specifications can be changed facilitates the development of optimal dynamic efficiencies, both as regards the functioning of a system of parts and the manufacture of any given part. Simulation is also used in electronic design automation, in which simulated flow of current through a circuit enables the rapid testing of various component configurations.

The processes of design and manufacture are, in some sense, conceptually separable. Yet the design process must be undertaken with an understanding of the nature of the production process. It is necessary, for example, for a designer to know the properties of the materials with which the part might be built, the various techniques by which the part might be shaped, and the scale of production that is economically viable. The conceptual overlap between design and manufacture is suggestive of the potential benefits of CAD and CAM and the reason they are generally considered together as a system.

Exercise 1. Read and memorize using a dictionary:

spatial, drafting, cutaway, retrieve, flexibility, penetrate, artificial, grid, mesh, distort, facilitate, substitute, implementation, tensile, pattern, viable, overlap, lever, property, shape

Exercise 2. Answer the questions:

1. How can a designer magnify certain elements of a model to facilitate inspection?

2. How do dynamics tests function?

3. What are the most common types of simulation?

4. How are model surfaces shown in stress tests?

Exercise 3. Complete the sentences with the suggested words: relation, involve, gravity, mimic, nuts.

The system could then _____ the engineer's thought pattern and actually "create" more of the design. Expert systems might _____ the implementation of more abstract principles, such as the nature of _____ and friction, or the function and _____ of commonly used parts, such as levers or _____ and bolts.

Exercise 4. Ask questions to the given answers:

1. Question: _______________________________?

Answer: The system could then mimic the engineer's thought pattern and actually "create" more of the design.

2. Question: _______________________________?

Answer: Dynamics tests function as a complement or substitute for building working prototypes.

3. Question: _______________________________?

Answer: Simulation is also used in electronic design automation, in which simulated flow of current through a circuit enables the rapid testing of various component configurations.

Exercise 5. Match the left part with the right:

1. One of the key areas of development in CAD technologies	a) can magnify certain elements of a model to facilitate inspection.
2. Thus the design process using CAD involves	b) is the simulation of performance.
3. The system could then mimic the engineer's thought pattern	c) transferring a designer's idea into a formal geometrical model.
4. CAD systems also offer "zoom" features analogous to a camera lens, whereby a designer	d) and actually "create" more of the design.

Exercise 6. Learn the following definitions:

A cutaway drawing is a 3D graphics, drawing, diagram and or illustration, in which surface elements a three-dimensional model are selectively removed, to make internal features visible, but without sacrificing the outer context entirely.

Stress testing (sometimes called torture testing) is a form of deliberately intense or thorough testing used to determine the stability of a given system or entity. It involves testing beyond normal operational capacity, often to a breaking point, in order to observe the results.

Artificial intelligence (AI) is the intelligence exhibited by machines or software, and the branch of computer science that develops machines and software with human-like intelligence.

Gravity is the force of attraction that moves or tends to move bodies towards the centre of a celestial body, such as the earth or moon.

Exercise 7. Compose a story on one of the topics (up to 100 words):

“Advantages of CAD and CAM”

“Disadvantages of CAD and CAM”