Osman Selçuk Şahin 030060090

DNC:Several machines are controlled directly step by step by a central mainframe computer.In this system the operator has access to the central computer through a remote terminal.With DNC,the status of all machines ina manufacturing facility can be monitored and assesed from a central computer.However DNC has a crucial disadvantage:If the computer shuts down all of the machines become inoperative.A more recent definition of DNC is distributed numerical control in which a central computer serves as the control system over a number of individual CNC machines having onoard microcomputers.This system provides large memory and computational facilities and offers flexibility while overcoming the disadvantage of direct numerical control.
(Serope Kalpakjian- Steven R. Schmid p:1155)

Hard Automation: The machines are designed to produce a standard product,such as gear, a shaft or an engine block. Although product size and processing parameters (such as speed, feed, and depth of cut) can be changed ,these machines are specialized and lack flexibiity.They cannot be modified to accomodate products that have different shapes and dimensions.Because these machines are expensive to design and build, their economical use requires the production of parts in very large quantities.The machines used in hard automation applications usually are built on the modular principle.They generally are called transfer machines and consist of two major components: powerhead production units and transfer mechanism.
(Serope Kalpakjian- Steven R. Schmid p:1150)

Design for servicing: Design for assembly and dissambly includes taking into account the ease with which a product can be serviced and if necessary repaired.Design for servicing essentially is based on the concept that the elements that are most likely to need servicing be at the outer layers of the product.In this way individual parts are easier to reach and service without the need to remove various other parts in order to do so.
(Serope Kalpakjian- Steven R. Schmid p:1186)

Flexible fixturing: In describing workholding devices for the manufacturing operations throughout this book, the words clamp,jig, adn fixture often were used interchangeably and sometimes in pairs such as in jigs and fixtures.Clamps are simple multifunctional workholding devices and jigs have various reference surfaces and points for accurate alignment of parts or tools.Fixtures generally are designed for specific purposes.Other workholding devices also include chucks, collets, and mandrels, many of which usually are operated manually. Workholding devices are also are designed and operated at various levels of mechanization and automation and are driven by mechanical hydraulic or electrical means.Workholding devices generally have specific ranges of capacity.For example a particular collet can accomodate bars only within a certain range of diameters; four-jaw chucks can accomodate square or prismatic workpieces having certain dimensions; various other devices and fixtures are designed and made for specific workpiece shapes and dimensionsan for specific tasks called dedicated fixtures.If the part has curved surfaces, it is possible to shape the contacting surfaces of the jaws themselves by machining them to comfort to the workpiece surfaces.The emergence of flexible manufacturing systems has necessitated the design and use of workholding devices and fixtures which have built in flexibility.There are several methods of flexible fixturing based on different principles that also are called intelligent fixturing systems.These devices are capable of quickly accomodating a range of part shapes and dimensions without the necessity of extensive changes adjustments or requiring operator interventions both of which would affect productivity adversely. (Serope Kalpakjian- Steven R. Schmid p:1176)