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INTRODUCTION OF INVESTMENT CASTING Process of investment casting Application of investment casting Benefits of investment casting DIE DESIGN Component of Die DESIGN OF GATING SYSTEM Design of Gating Elements
Investment casting is an industrial process and also called lost-wax casting.
The castings allow the production of components with accuracy, repeatability, versatility and integrity in a variety of metals and high-performance alloys.
It can be used to make parts that cannot be produced by normal manufacturing techniques, such as turbine blades that have complex shapes, or airplane parts that have to withstand high temperatures.
The mold is made by making a pattern using wax or some other material that can be melted away.
Tolerances of 0.5 % of length are routinely possible, and as low as 0.15 % is possible for small dimensions.
Castings can weigh normal size ranges from 200 g to about 8 kg
(7 oz to 15 lb).
e or blank.
Characteristics of the blanking process include:
Normal minimum wall thicknesses are about 1 mm to about 0.5 mm (0.040-0.020 in) for alloys that can be cast easily.
The types of materials that can be cast are Aluminum alloys, Bronzes, tool steels, stainless steels, Stellite, Hastelloys, and precious metals.
Parts made with investment castings often do not require any further machining, because of the close tolerances that can be achieved.
Investment Casting Process is as follow:
1) Wax Injection
1) Assembly
1) Shell Building
1) Dewax
1) Conventional Casting
1) Knockout
1) Cut off
1) Finished Casting
Investment casting is used in the aerospace and power generation industries to produce turbine blades with complex shapes or cooling systems.
Investment casting is also widely used by firearms manufacturers to fabricate firearm receivers, triggers, hammers, and other precision parts at low cost.
Other industries that use standard investment-cast parts include military, medical, commercial and automotive.
The investment shell for casting a turbocharger rotor
A view of the interior investment shows the smooth surface finish
o Excellent surface finish.o Tight dimensional tolerances.o Complex and intricate shapes may be produced.o Capability to cast thin walls.o Wide variety of metals and alloys (ferrous and non-ferrous) may be
cast.o Low material waste.
Benefits of Investment CastingBenefits of Investment Casting
A Die is a specialized tool used in manufacturing industries to cut or shape material using a press.
Like molds, dies are generally customized to the item they are used to create.
Products made with dies range from simple to complex pieces used in advanced technology.
In addition to these many types of channels, there are other design issues that must be considered in the design of the dies.
Firstly, the die must allow the molten metal to flow easily into all of the cavities.
Equally important is the removal of the solidified casting from the die.
Die DesignDie Design
Dies can be fabricated out of many different types of metals. High grade tool steel is the most common and is typically used.
Other common materials for dies include chromium, molybdenum, nickel alloys, tungsten, and vanadium.
Die block This is main part that all the other parts are attached to.
Punch plate This part holds and supports the different punches in place.
Blank punch This part along with the Blank Die produces the blanked part.
Pierce punch This part along with the pierce Die removes parts from the
blanked finished part.
Component of DieComponent of Die
Finger stop / Guide This part is used to make sure that the material being worked
on always goes in right position.
Setting (Stop) Block This part is used to control the depth that the punch goes into
the die.
Selection of ComponentSelection of Component
Connecting Rod
We have to select following connecting Rod.
A mould cavity must be filled with clean metal in a controlled manner to ensure smooth, uniform and complete filling, for the casting to be free of discontinuities, solid inclusions and voids. This can be achieved by a well-designed gating system.
The first step involves selecting the type of gating system and the layout of gating channels: the orientation and position of spure, runner and in gate
The most critical design decision is the ideal filling time, based on which the gating channels are designed.
The main objective of a gating system is to lead clean molten metal poured from ladle to the casting cavity, ensuring smooth, uniform and complete filling.
Design of Gating SystemDesign of Gating System
The major elements of a gating system include pouring basin, sprue, runner and in gate, in the sequence of flow of molten metal from the ladle to the mould cavity.
Gating systems can be classified depending on the orientation of the parting plane (which contains the sprue, runner and in gates), as horizontal or vertical. Depending on the position of the in gate , gating systems can be classified as top, parting and bottom.
Sprue
It usually has a circular cross-section, which minimizes turbulence and heat loss.
Design of Gating ElementDesign of Gating Element
Gating ratio
The area of the sprue top should be calculated using mass and energy
Balance equations, to prevent flow separation in the sprue. Essentially,
A1 √H1 = A2 √H2 Where, H1 and H2 are the metallostatic pressure head at the
top and bottom of the sprue, Respectively; A1 and A2 being the respective cross-sectional
areas.
Runner
The main function of the runner is to slow down the molten metal, which speeds up during its free fall through the sprue, and take it to all the ingrates.
This implies that the Total cross-sectional area of runner(s) must be greater than the sprue exit.
In general a Ratio of 1:2 is recommended. The second implication is that the runner must fill completely
before letting the molten metal enters the ingrates.
Ingate
The ingate leads the molten metal from the gating system to the mould cavity.
Design of Gate for Connecting RodDesign of Gate for Connecting Rod
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Fabrication of Die of Connecting rod.
