12-12-2012, 06:19 PM
National Small Industries Corporation Ltd. (NSIC
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INTRODUCTION
NSIC was formed on August 24,1980. National Small Industries Corporation Ltd. (NSIC), is an ISO 9001-2008 certified Government of India Enterprise under Ministry of Micro, Small and Medium Enterprises (MSME). NSIC has been working to fulfill its mission of promoting, aiding and fostering the growth of small industries and industry related micro, small and medium enterprises in the country. Over a period of five decades of transition, growth and development, NSIC has proved its strength within the country and abroad by promoting modernization, upgradation of technology, quality consciousness, strengthening linkages with large medium enterprises and enhancing exports - projects and products from small enterprises.
NSIC operates through countrywide network of offices and Technical Centres in the Country. To manage operations in African countries, NSIC operates from its office in Johannesburg, South Africa. In addition, NSIC has set up Training cum Incubation Centre & with a large professional manpower, NSIC provides a package of services as per the needs of MSME sector.
NSIC carries forward its mission to assist small enterprises with a set of specially tailored schemes designed to put them in a competitive and advantageous position. The schemes comprise of facilitating marketing support, credit support, technology support and other support services.
MILLING MACHINE
Working Principle:
The workpiece is holding on the worktable of the machine. The table movement controls the feed of workpiece against the rotating cutter. The cutter is mounted on a spindle or arbor and revolves at high speed. Except for rotation the cutter has no other motion. As the workpiece advances, the cutter teeth remove the metal from the surface of workpiece and the desired shape is produced.
Different milling machine & cutters
Plain milling cutters that are more than 3/4 inch in width are usually made with spiral or helical teeth. A plain spiral-tooth milling cutter produces a better and smoother finish and requires less power to operate. A plain helical tooth milling cutter is especially desirable when milling an uneven surface or one with holes in it.
The helical milling cutter is similar, to the plain milling cutter, but the teeth have a helix angle of 45° to 60°. The steep helix produces a shearing action that results in smooth, vibration-free cuts. They are available for arbor mounting, or with an integral shank with or without a pilot. This type of helical cutter is particularly useful for milling elongated slots and for light cuts on soft metal. See Figure 8-5.
Saw teeth similar to those shown in Figure 8-3 are either straight or helical in the smaller sizes of plain milling cutters, metal slitting saw milling cutters, and end milling cutters. The cutting edge is usually given about 5 degrees primary clearance. Sometimes the teeth are provided with off-set nicks which break up chips and make coarser feeds possible.
STRADDLE MILLING
When two or more parallel vertical surfaces are machined at a single cut, the operation is called straddle milling. Straddle milling is accomplished by mounting two side milling cutters on the same arbor, set apart at an exact spacing. Two sides of the workpiece are machined simultaneously and final width dimensions are exactly controlled.
MILLING A HEXAGON
Straddle milling has many useful applications introduction machining. Parallel slots of equal depth can be milled by using straddle mills of equal diameters. Figure 8-29 illustrates a typical example of straddle milling. In this case a hexagon is being cut, but the same operation may be applied to cutting squares or splines on the end of a cylindrical workpiece. The workpiece is usually mounted between centers in the indexing fixture or mounted vertically in a swivel vise. The two side milling cutters are separated by spacers, washers, and shims so that the distance between the cutting teeth of each cutter is exactly equal to the width of the workpiece area required. When cutting a square by this method, two opposite sides of the square are cut, and then the spindle of the indexing fixture or the swivel vise is rotated 90°, and the other two sides of the workpiece are straddle milled.
FORM MILLING
Form milling is the process of machining special contours composed of curves and straight lines, or entirely of curves, at a single cut. This is done with formed milling cutters, shaped to the contour to be cut. The more common form milling operations involve milling half-round recesses and beads and quarter-round radii on workplaces (Figure 8-33), This operation is accomplished by using convex, concave, and corner rounding milling cutters ground to the desired circle diameter. Other jobs for formed milling cutters include milling intricate patterns on workplaces and milling several complex surfaces in a single cut such as are produced by gang milling.