Casting is a process of forming metallic products by melting the metal and pouring it into a cavity know as the mould and allowing it to solidify, there are several casting methods like gravity or permanent mould casting, slush casting, pressed or corthias castings, die casting, hot chamber machines, cold chamber machines, centrifugal castings, semi-centrifugal casting. Precision castings lost wax casting method, Plaster moulds, Shell molding, mould of woods, rubber and paper.
In this article we will discuss advantages and dis-advantages of DIE CASTING process.
Advantage of Die Casting
1)Very high rates of production are possible, viz, in cold chamber type 75 to 150 units per hour and in hot chamber type 300 to 350 units per hour.
2)Close dimensional control can be maintained, in zinc, a tolerance of +/- 0.075 mm up to 25 mm size and +/- 0.025 mm for each additional 25 mm can be easily achieved.
3)Thin section can be cast; under favorable conditions minimum thickness cast are about 0.5 mm for zinc and 0.875 mm for aluminum.
4)Surface finish of 1250 micro-mm R.M.S can be obtained hence appearance is improved and finishing operation are minimized.
5)Details can be reproduced successfully with a high degree of precision.
6)Die Casting dies retain their accuracy and usefulness for a long time, dies for zinc alloys may produce as many as 5 million castings.
7)For mass production die casting is very economical due to elimination of machining and mould making resulting in saving of labor and time.
8)Because of the uniformity in wall thickness less material is required in die casting than in sand casting.
9)There are no possibilities for sand inclusions and a strong dense metal structure is obtained.
Disadvantage of Die Castings
1)High cost of the equipment and dies used requires sufficiently large quantities to compete economically with other processes, For die casting minimum economic quantity is considered like 20,000 pcs per production lot.
2)There is rapid decrease in the life of the dies as the metal temperature increases.
3)In some cases there is an undesirable chilling effect on the metal.
4)Metals having high coefficient of contraction must be removed from the mould as soon as possible because of the inability of the mould to contract with the casting.
5)There is certain limitation in the shape of die castings and the process is not adapted to the production of large castings, so far the maximum size cast is 100 Kg in zinc and 30 Kg in Aluminum.
6)Die castings usually contain some porosity due to the entrapping of air.
7)Die casting has, to a large extent, been limited to low melting non ferrous alloys.
With gradual improvement of heat resisting metals for dies, this process can now be used for numerous alloys.
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