Evrim Berk 030060161 10th Week

1-) Reciprocating Mold Process

A reciprocating, water-cooled copper mold is used, the down stroke being synchronized with the discharge rate of the slab. Molten metal is poured into the holding furnace and is discharged to the mold after being metered through a '%-in. (22-mm) orifice at the needle valve. The down spout tube is 1% in. (28 mm) in diameter and delivers metal at the rate of 30,000 lb/h (225 kg/s).

The molten metal is distributed across the mold from a submerged horizontal crosspiece. The level of the metal is held constant at all times. The pouring rate of the molten metal is controlled by a needle valve through the top of the holding furnace. As the metal becomes chilled in the lower part of the mold, it discharges at a constant rate and enters the withdrawing rolls. These are synchronized with the downward movement of the mold and are mounted just above a circular saw that cuts the slab to required lengths. Brass slabs are further processed by cold rolling into sheets and strips. Large quantities of 7- to 10-in. (178- to 254-mm) round billets for hot-extrusion processes are also produced in this manner.

( Ostwald P. Munoz J., Manufacturing Processes and Systems, Pg: 119)


*There is not any available older definition.

2-) Printed Circuit Board

The microcircuit begins with conceptualization of the circuit design. When the design is completed, sets of plates called photomasks are produced from the circuit layout. Each photomask contains a pattern for a layer on the circuit. These patterns are transferred to the silicon wafer by the photolithographic process, thus building layer upon layer on the microelectronic circuit. An early step in circuit fabrication is the layout. This phase is often called the artwork. To print the circuit, first a photographic mask must be made. The mask is a photographic reduction of a set of cut and strip masters typically 250 to 500 times larger than the actual size of the circuit. At each stage of this process, including the final stage when the entire circuit is completed, the layout is checked by means of detailed computer drawn plots. Since the individual circuit elements can be as small as a few micrometers across, the checking plots must be magnified. Thus, these plots are 500 times larger than the final size of the circuit. Eventually, the photomask becomes a glass plate about 5 in./ side (125 mm) and has a single circuit pattern repeated many times on its surface. These plates are transferred to the wafer fabrication facility, where they will be used to produce the desired sequence in a physical structure.

Another step in the construction of the mask is photography. High-precision camera equipment must be used to ensure a sharp, clear image on the reduction. Also, the camera and master must be clean and rigidly supported. A dust spot could render the final circuit inoperational. A clean room where conditions can be controlled is necessary.

Long exposures are often taken. Therefore, the camera must not be affected by any vibrations.

( Ostwald P. Munoz J., Manufacturing Processes and Systems, Pg: 455 )


*There is not any available older definition.


3-) Laser Beam Machining


Laser beam machining is the process which the work material is melted vapourised by means of intense monochromatic beam of light called the laser. Laser is an electromagnetic radiation. It produces monochromatic light in the form of an almost collimated beam to remove material.


Advantages:


1-Dissimilar Metals can be welded easily.
2-Heat affected zone is small.
3-No direct contact between the tool and workpiece.
4-Ease of control
5-Refractory, brittle and hard materials are easy to work.
6-No tool wear.
7-Soft materials like rubber and plastics can be welded.


Disadvantages:


1-Overall efficiency is extremely low. (%10 - %15)
2-The process is limited to thin sheets.
3-Low rate of material removals.
4-Lite of flash lamp is low
5-High cost.


Applications:


1-Welding
2-Cutting
3-Heat Treatment
4-Microwelding and Microcutting
5-Sheet metal trimming, blanking and engraving
6-Determining of the distance, velocity, direction, size and form of distant objects by menas of selected signals of the radar.


( Bawa H.S., Manufacturing Processes - II, Pgs: 196 - 198 )


*There is not any available older definition.


4-) Flame Straightening


Flame Straightening employs the same technique as flame bending but is used to straighten steel members instead of bending them. While flame straightening can be used to remove bends in pipe and small rolled sections, its principle application is the in-place repair of damaged, heavy steel sections; beams, columns, girders, trusses, and crane rails. Any steel member can be repaired by flame straightening. These repairs are often done on bridge beams struck by over-height loads, or damaged by over-weight vehicles. Sometimes bridge columns need straightening after being hit by run-away vehicles, loads and ships. Steel erection mishaps, structural steel fire damage, and cargo container crane boom collapses are also excellent candidates for flame straightening. Flame straightening is also very useful for straightening railings, racks and other long structures that have been bent by welding shrinkage.


( Marlow M.F., Welding Application & Repair: Questions and Answers, Pg: 120 )


*There is not any available older definition.


5-) Electrostatic Workholder



Magnetic Chucks can be used only with ferromagnetic materials. Electrostatic chucks can be used with any conductive materials. This principle (figure below) directs that work be held by mutually attracting electrostatic fields in the chuck and the workpiece. This provide a holding force up to 20 psi (21000 Pa) Non-metal parts can usually be held if they are flashed with in a thin layer of metal. These chucks have the added advantage of not inducing residual magnetism in the work.

( Black J.T. Kohser R.A., DeGarmos's Materials & Processes in Manufacturing, 10th Edition, Pg: 696 )

*There is not any available older definition.