18-07-2012, 03:54 PM
DESIGN OF JIG AND FIXTURE FOR MILLING MACHINE
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1NIRODUCTION
One of the most time-consuming and labor extensive processes in the manufacturing of a
mechanical part is the process of work holding or fixiuring. It is often remarked that
only approximately 10-15% of the overall time required to produce a part is spent
actuaii); on cutting or drilling a work piece; the other time is spent primariiy pianning for
executing part setup or work holding which is still performed by highly skilled
machinists based on their experience. Kecently, industries have begun to experience
difficulty finding highly skilled machinists because the number of apprentices is
decreasing and it is iikeiy that the situation wit1 worsen in the future.
Problem Statements
Manufacturing in its broadest sense is the process of converting raw material into
products. it encompasses the design of the product, the selection of raw nlaterials and
the sequence of processes through which the product will be manufactured.
klanufacturing is the backbone of any industriaiized nation. Its impor'ance is
emphasized by the fact that, as an economic activity, it comprises approximately 20% to
JO'% of the vaiue of atl goods and services produced. Manufacturing also involves
activities in which the manufactured product is itself used to make other products.
Examples of these products are large presses to shape sheet metal tbr car bodies,
machinery to make bolts and nuts and sewing machines for making clothing.
Scope of Project
Jigs and fixtures are production-work holding devices used to manufacture duplicate
parts accurately. Ajig is a special device which holds, supports, or is placed on a part to
be machined. It is a production tool made so that it not only locates and holds the work
piece, but also guides the cutting tool as the operation is performed. A fix-ture is a
production tool that locates, holds and supports the work securely so the required
machining operations a n be performed. A fixture should be securely fastened to the
table of the machine upon which the work is done.
Introduction to the Jigs and Fixtures
Mast production aims at high productivity to reduce unit cost and interchange ability to
facilitate cost assembly. 'l'his necessitates production devices to increase tlie rate of
manufacture devised, to speed up the inspection devised and to speed up the inspection
procedure.
Definition of Jigs and Fixtures
Jigs:
Budget may be defined as the device which holds and positions the work piece, iocates
or guides the cutting tool related to the work piece and usually is not fixed on the
machine table.