production of gears by die casting

8/13/2019 Production of Gears by Die Casting

1/17

PRODUCTION OF GEARS BY

DIE CASTING

BATCH-2


2/17

DIE CASTING

In Die casting the molten metal is forced to flow into a

permanent metallic mold under moderate to high pressures,

and held under pressure during solidification.

This high pressure forces the metal into intricate details,

produces smooth surface and excellent dimensional accuracy.

High pressure causes turbulence and air entrapment. In order

to minimize this larger in-gates are used and in the beginning,

pressure is kept low and is increased gradually.

The mold cavity is created using two hardened tool steel dies

which have been machined into shape and work similarly to

an injection mold during the process.


3/17

Most die castings are made from non-ferrous metals,

specifically zinc, copper, aluminum, magnesium, lead, pewter

and tin based alloys. Depending on the type of metal beingcast, a hot- or cold-chamber machine is used.


4/17


5/17

Hot chamber casting


6/17

Cold chamber casting


7/17


8/17

Many different types of gears can be die cast, such as spur,

helical worm, clusters, and bevel gears.

Applications for these types of gears include toys, washing

machines, small appliances, hand tools, cameras, business

machines, and similar equipment.


9/17

OPERATION CYCLE

In a cold chamber process, the molten metal is poured into thecold chamber in each cycle.

The operating cycle is

(i) Die is closed and molten metal is ladled into the cold chamber

cylinder(ii) Plunger pushes molten metal into die cavity; the metal is held

under high pressure until it solidifies

(iii) Die opens and plunger follows to push the solidified slug from the

cylinder, if there are cores, they are retracted away (iv) Ejector pins

push casting off ejector die and plunger returns to original position.

This process is particularly useful for high melting point metals such as

Aluminum, and Copper (and its alloys).


10/17

ADVANTAGES

Excellent surface finish Excellent dimensional accuracy

High production rate

Complex shapes can be cast

Little or no finishing cost

DISADVANTAGES

Limitation on part size High cost of die

Generally limited to casting of non ferrous metals


11/17

ALUMINIUM BRONZE CASTING


12/17

STRENGTH Zinc diecastings ambient temperature Yield Strengths are far

more superior than those of Aluminium and Magnesium.

Zinc diecastings Ultimate Tensile Strengths (UTS) can

outperform Aluminium and Magnesium.

The strength of zinc diecastings in shear, torsion, under

bending and in compression is far superior to aluminium,

magnesium and plastics


13/17


14/17

Fatigue is one of the most frequent failure mechanisms in

components. Zinc, like other diecast metals, is between 7 to

10 times more resistant to fatigue than ABS.

TheFracture Toughness of diecast zinc and other metals is

around 10 to 30 times greater than that of engineering

plastics.


15/17

CONSISTANCY

Pressure diecastings are 5 to 10 times more accurate than

products made by other processes such as pressing, gravity

casting or powder forming. Within pressure diecasting, zinc

alloy castings are 2 to 4 times more accurate than those made

from magnesium and aluminium alloys. High solidificationshrinkage and water absorption make close tolerances in

plastics difficult to achieve.

The exceptional accuracy, predictability and repeatability

obtained from the zinc die casting process. Surface qualityconsistency is excellent due to the extremely low rate of tool

surface degradation.


16/17


17/17

THANK YOU

production of gears by die casting

Documents