M. Burak Toprakoğlu - 030070082 - 4th week

Water-Jet Machining:

When we put our hand across a jet of water or air, we feel a considerable concentrated force acting on it. This force results from the momentum chance of the stream and, in fact, is the principle on which the operation of water or gas turbines is based. In water-jet machining (WJM) (also called hydrodynamic machining), this force is utilized in cutting and deburring operations.

The water jet acts like a saw and cuts a narrow groove in the material. A pressure level of about 400 MPa is generally used for efficinet operation, although pressures as high as 1400 MPa can be generated. Jet-nozzle diameters range between 0,05 and 1 mm. A variety of materials can be cut, including plastics, fabrics, rubber, wood products, paper, leather, insulating materials, thickness can range up to 25 mm and higher. Vinly and foam coverings for automobile dashboards (as well as some body panels) are being cut bu multiple-axis, robot-guided water-jet machining equipment. Because, it is an efficient and clean operation compared with other cutting processes, it is also used in the food-processing industry for cutting and slicing food products

The advantages of this process are as follows:

-Cuts can be started at any location without the need for predrilled holes
-No heat is produced
-No deflection of the rest of the workpiece takes places; thus, the process is suitable or flexible materials.
-Little wetting of the workpiece takes places
-The burr produced is minimal
-It is an environmentally safe manufacturing process.

(Kalpakjian S. Schmid S.R.,Manufacturing Engineering and Technology Sixth Edition in SI Units, p. 778)

Vertical Integration:

Firms may find opportunities for exparison in existing product lines, in vertical integration or in diversification. They can achieve this expansion either by internal growth or by acquisition. Before turning to a detailed consideration of these issues it is useful to summarise some of the main factors that help shape the outcome

Vertical Integration may be considered either as a static dimension of market structure or as a dynamic process which alters market structure and possibly business behviour and performance.

As a static measure of the extent to which vertically related activities take place within a firm there is no difficulty in identifying individual industries where vertical integration is extremely important and those where it is not. The petroleum industry clearly falls into the first category since the largest firms carry out all the activities from exploration, through refining to the final marketing of the products. On the other hand retailing is largely unintegrated, with most retailing giants doing very little manufacturing.

Although clear-cut cases are not difficult to identify there are problems in devising quantitive measures that allow systematic comparisons across industries. A measure of integration that would appear suitable and which can be computed from available data is the ratia of value added to sales. However this will give misleading comparisons when firms are located at different stages in the vertical chain.

(Kenneth Desmond George, Caroline Joll, E. L. Lynk, Industrial organisation: competition, growth and structural change, 4th Edition, p.63-64)

Tempering:

If steels are hardened by heat treatment, then tempering or drawing is used in order to reduce brittleness, increase ductility and toughness, and reduce residual stresses. The term "tempering" is also used for glasses. In tempering, the steel is heated to a specific temperature, depending on its composition, and then cooled at a prescribed rate. Alloy steels may undergo teper enbirttlement, which is caused by the segregation of impurities along the grain boundries at temperatures between 480 C and 590 C.

(Kalpakjian S. Schmid S.R.,Manufacturing Engineering and Technology Sixth Edition in SI Units, p. 123)

Austempering:

In austempering, the heated steel is quenched from the austenitizing temperature rapidly, to avoid formation of ferrite or pearlite. It is held at a certain temperature until isothermal transformation from austenite to bainite is complete. It is then cooled to room temperature, usually in still air and at a moderate rate in order to avoid thermal gradients within the part. The quenching medium most commonly used is molten salt, at temperatures ranging from 160 C to 750 C.

Austempering is often substituted for conventional quenching and tempering, either to reduce the tendency toward cracking and distortion during quenching or to improve ductility and toughness while maintaining hardness. Because of the shorter cycle time involved, this process is also economical for many applications. In modified austempering, a mixed structure of pearlite and bainite is obtained. The best example of this practise is patenting, which provides high ductility and moderately high strength, such as in patented wire.

(Kalpakjian S. Schmid S.R.,Manufacturing Engineering and Technology Sixth Edition in SI Units, p. 123)