Unit II technological processes

Part I

I. Read the text and decide if the following questions correspond to the information in the text.

1) Is the real purpose of engineering to create useful goods and services, to make them better, cheaper, and more abundant?

2) Can you enumerate some processes of making objects from metal?

3) Engineers work with many kinds of materials, but metals are the most important because of their strength, durability, and stability, aren’t they?

4) Can any article be produced by only one process?

5) When was the first power-driven machine tool used?

6) What are the advantages of metal machining?

7) What types of methods require great skill to guide the tools to produce true surfaces?

8) Can you give the definition of the machine tool?

Technological Process

The real purpose of engineering is to create useful goods and services, to make them better, cheaper, and more abundant. The physical conveniences of our everyday lives are constant evidence of engineers' efforts. Swift and comfortable transportation, instant and widespread communication, efficient appliances, and light and power from electricity are only a few of the conveniences available to us because of the ceaseless endeavor of engineers to transmit ideas into realities. And one of the most important aids to engineers in realizing their goals is metal machining, the cutting or shaping of metals by power-driven machine tools.

Objects can be made from metal by a number of processes. Among them are founding, forging, forming, rolling, welding, and cutting. Metal machining in­cludes the cutting processes. An article can often be made by any of several processes. Sometimes the most convenient method is chosen, but normally that process is selected that produces the required results at the lowest cost.

Metal machining is advantageous in many cases. The basic machine tools are versatile, and almost any piece can be made with them. Large amounts of material can be removed by machining when necessary, and pieces can be cut off parent material or separated from each other without excessive waste. Parts can be machined from standard shapes like bars and places.

Machining is not limited to make parts in small quantities. It has advantages for large as well as small quantity production. Surfaces can be machined to almost any degree of accuracy. In fact, the most accurate surfaces can be obtained at reason­able cost only by machining methods. Parts that are formed roughly by other processes, like founding and forging, normally have some or all of their surfaces refined by machining. For instance, most engine blocks are cast, and then their cylinders, faces, and bearing surfaces are machined. Certain machining processes, like grinding, are capable of finishing the surfaces of very hard substances.

In all metal cutting opera­tions an edged tool is driven through material to separate chips from the parent body. Metal may be cut by simple hand tools such as hammer and chisel, file, saw, or stone. At one time such tools were about the only means available for cutting metals. Obviously the articles cut from metal solely by hand tools were few and crude. Such methods are slow and laborious and require great skill to guide the tools to produce true surfaces. With the advent of the industrial revolution, the invention and development of devices like the steam engine and textile machinery called for faster and more accurate methods of cutting and forming metals. Machines were devised to apply power to metal cutting and hold and move workpieces surely and precisely. These superior tools were given the name of machine tools, in contrast to hand tools, and the work done by them was called metal machining. The planing, turning, drilling, and boring machines came into being early. At first it was considered quite an accomplishment just to make a few articles of metal; later the demand arose for quantity production. Machining methods were applied to firearms and clocks and to new inventions, like the reamer and the sawing ma­chine. Other machine tools like the milling machine, turret lathe, and grinding machine were developed to cut metal faster, reduce labor, and bring about greater precision. To meet the demands of the present century for production in very large quantities, highly specialized and automatic machine tools have been developed. Up to the present time the improvement of machine tools and machin­ing methods has gone steadily forward and gives no sign of faltering.