This considered as art and science. The rigging

This chapter is mainly describing
the theory and research which have been defined and done by various researcher
years ago. Related information of previous studies is extracted as references
and discussion based on their research about gel coat thickness, laminate
composite structure, mechanical and physical properties

Making a casting is one of the oldest
manufacturing techniques known to mankind and an immediate method for creating
metal parts. The essential castings can be backpedalled to out of date China is
the fourth century B.C. Through the casting system,
fluid metal is filled a shape that matches the last estimations of the finished
product. While all metals can be cast, the most common are aluminium, iron,
copper-base, and steel combinations. The range of casting is in weight from
less than an ounce to single parts measuring a few hundred tons as shown at
figure 2.1 Casting process of metal parts 4th century B.C. (Habashi, 2007)

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            Defects
such as porosity and shrinkage are exist in sand casting process to permanent
mould casting. Design is the progress to make improvement of high quality and
cost effective of the casting product. In designing a decent permanent mould,
the part geometry assumes an important part. The primary reason for designing
the moulds is to concentrate the fluid metal compression until to the last part
of the casting to solidify. Besides, comprehensive set of economical permanent
mould is important to produced. The first part that must consider in sand
casting mould preparation is the gating system. (Groover,
2012)

The design of framework is extremely basic
to the casting processes since it will influence the ensuing design procedures
and impact the quality of the casting product. Besides, gating designs is the
important part must be considered if not it could lead to various defects such
as gas porosity, shrinkage, flow lines, cold shuts and poor surface finish. A
standout amongst the most approaches was using a continuous gating system and a
bigger size runner, and the fluid metal speed through the gating was slightly
reduced. (Butler,
2001)

            (Jhavar,
Paul, & Jain, 2013), the authors describe the causes of
failures and repairing alternatives in designing of die and mould in the design
stage. Designing of permanent moulds for casting can be considered as art and
science. The rigging system which is runners, gates, risers, overflows and cooling channels
are the most important part
of the mould. Presently, the current practice in designing mould is an
experimenting method where based on trial and error. The experimentation
strategy exclusively relies upon learning and experience of design engineers.
However, this practice leads time consuming and high cost.

This paper
presents the connecting rod crankshaft as a case study. The objective of this
research is to design and analysis the systems for die casting using computer
engineering analysis software. The simulation presents the analysis of static
pressures, velocity magnitude, turbulence kinetic energy, internal energy and
cell Reynolds numbers. Based on the simulation results, the die casting was
developed.

The die casting process is a name given to metal casting
processes that utilize metal moulds or permanent dies. There are really several
distinct processes included under the general name. The die casting process has
three main sub-processes. These are permanent mould casting, also called
gravity die casting, low-pressure die casting, and high-pressure die casting.
The three processes differ mainly in the amount of pressure that is used to
force the molten metal into the die. In fact, the useful of the mould depends
largely on the pouring temperature, the material of the mould and the
complexity of the component being cast. Figure 2.2 illustrated the process tree
under permanent mould casting process. (Kalpakjian, S. &
Steven, 2009)

The alternate elements that have been consider are mould
preheating, mould coating, rigging system, gating design, runner design and whether
the operation is manual or automated. The end use of the casting also has a
bearing (If the auxiliary capacity is the main criteria, and not its
appearance, a mould can be utilized longer before disposing). In spite of the
fact that, all things considered, the permanent moulds are metallic, graphite
moulds, used at times, also come under the category of Permanent Moulds. When
sand cores are used, it is called a Semi-Permanent Moulding (SPM) process. (M. S. Ramaprasad
& Malur N. Srinivasan, 2012).

 

            (Lampman, 2009) describes permanent mould casting is a casting process that uses non-expendable
that are either made from metal or graphite. Permanent mould processes involve
the production of castings by pouring molten metal into permanent metal molds
using gravity, low pressure, vacuum or centrifugal pressure and simple reusable
cores are usually made of metal.

High volume production of non-ferrous metal due to the
repeatability used is one of the permanent mould advantages. Furthermore, the
surface finish for the permanent mould is more better compared to the
conventional method which is sand casting. The immense heat transfer rate acquired
by methods for metal moulds can additionally refine and enhance the last cast
structure, and along therefore the mechanical properties of the castings due to
faster cooling rate. Moreover, the other benefit that it has is it also a
dimensional stability, geometric fidelity, and near net shaped castings. (Ravi, 2004)

Die casting mould have a good surface roughness than conventional
method which is sand casting because it is production of castings with uniform
wall thickness with 3.0mm can be cast, closer dimensional tolerances and better
surface finish that will restricted undercuts that will enhanced mechanical properties
(Lampman, 2009). As shown on Figure 2.3 is the illustrates of tolerance range
against surface roughness of various process include die casting and sand
castings process.

The disadvantages or design
limitations for the die casting mould is due to high cost, metal dies, longer
lead time for die production and for changes to the die caused by a casting
design change (Butler, 2001). Die casting mould casting has a few contraints, for example, not
all compounds are appropriate for die casting mould casting because of the

relatively high tooling costs, and a long set-up time of the
procedures because of that, a highly generation volume is required to keep this
process economically variable manufacturing option. The process can be restrictively
costly for low production amount. Furthermore, some shapes cannot be made using
die casting mould casting, because of parting line location, undercuts, or
difficulties in removing the casting from the mould.

 

Finally, coatings are required to protect the mould from attack by
the fluid metal (Lampman, 2009). Otherwise, die casting process is in general limited to smaller
castings. Besides, its higher the pouring temperature of the fluid metal and it
will shorter the life of the mould. (Zheng, Wang, Zhao, & Wu, 2009). Table 2.1 shown the gravity die casting and other castings.

Defects reduce the performance and increase the cost of castings.
It is critical to understand the mechanism of defects and microstructure on the
performance so that an effective tool can be developed to prevent defects and
control the microstructure. There are several defects that happen in casting
processes. Those defects are dependent on the chemistry of alloys, casting
design, and casting processes (Lampman 2009).

 

            (Strojniški, 2013) describes defects produced in aluminium alloy die casting dies
during die operation. The most frequent defect is thermal fatigue cracking.
Hardness and toughness is measured on specimens cut from different parts of
used die casting die. The results show a significant difference in material
microstructure and hardness between the surface and the core. Figure 2.4 shown the
several types defect of casting.

As one of
the oldest manufacturing methods, casting involves pouring molten metal into a
mould cavity that is con?gured to the shapes and dimensions of the ?nished
form. The methods of shape casting can be divided into several broad
categories, as illustrated in Figure 2.5. The main categories are expendable
moulds with permanent patterns, expendable moulds with expendable patterns and
Metal or permanent mould processes. (Strojniški, 2013).

Otherwise die casting mould is also called permanent mould,
it does not mean that the moulds are permanent. Indeed, the administration life
of the mould depends generally on the pouring temperature, the material of the
mould and the unpredictability of the component that being cast. Permanent
Moulds are used in many variants of casting processes like Gravity Die Casting
(GDC), Low Pressure Die Casting (LPDC), High Pressure Die Casting (HPDC),
Centrifugal Casting (CFC), Squeeze Casting (SC) and Continuous Casting (CC). (M. S. Ramaprasad
& Malur N. Srinivasan, 2012)

The most
important things to consistent and have a good casting design is how to choose
a suitable geometry. For make a cost-effective casting design, there are six
parameters based on physics that must considers. There are four considerations
based on casting properties such as, liquid metal fluid life, solidification
shrinkage type, slag/dross formation tendency and pouring temperature.
Furthermore, there also have two other design parameters are based on
structural properties which is section modulus and modulus of elasticity.
Geometry is not only the result of the product function design, it also influences
the of cost-effective that are economically produced, machined, and assembled
into a final product (Lampman, 2009)

            In designing a permanent mould there
set of general guidelines that can be followed such as design the part to make
a shape of cast is easy, locate the parting line of the mould in the part,
locates the design gates to allow uniform feeding of the mould cavity, select
appropriate runners geometry for the system and locate mould features such as
sprue, screen and riser as appropriate (Kalpakjian, S. &
Steven, 2009)

The rigging
system includes the system of sprues, runners, gates, risers, and chills that
channel and control the ?ow of liquid metal into the mould cavity, feed the
casting as it solidi?es, and control the heat transfer and rate of
solidi?cation in critical regions. Rigging system design speci?es the size,
dimensions and location of sprues, runners, gates, risers, and chills that
comprise the system. In the traditional approach, an expert casting engineer
designs the rigging system, usually after the geometry of the casting has been
speci?ed. Rigging design decisions typically include selection of the
following: orientation of the cast part, parting line, potential sites for
chills and chill types, sprue height and location, runner types and
con?guration, ingate sites, choke area, riser sites and con?guration, and
pouring rate and temperature. (Stoll, 2009)

(Banchhor & Ganguly, 2014) describes risers are used for prevention of shrinkage defects
(Figure 2.6). However, they decrease the usage rate of metal and extend the
cooling time of castings after solidification as well. Therefore, proper riser
size needs to be designed to satisfy feeding with the smallest volume.

(Howells, 2003) describes risering, deals with the development of suitable
reservoirs of feed metal in addition to the desired casting shape so that
undesirable shrinkage cavities in the casting are eliminated or moved to
locations where they are acceptable for the intended application of the
casting. When metals solidify and cool to form a casting, they generally
undergo three distinct stages of volume contraction, or shrinkage. Solid
shrinkage, also called patternmaker’s shrinkage, is accommodated by making the
pattern and, therefore; the mold cavity, somewhat larger than the desired
dimensions of the ?nal casting. Liquid shrinkage and solidi?cation shrinkage
are the concern of risering practice. In the absence of risers, a casting would
otherwise solidify as shown in Figure 2.7. (Lampman 2009)

To determine the correct riser locations, the designer should make
use of the concept of directional solidi?cation. If shrinkage cavities in the
casting are to be avoided, solidi?cation should proceed directionally from
those parts of the casting farthest from the riser, through the intermediate
portions of the casting, and ?nally into the riser itself, where the ?nal
solidi?cation will occur. Shrinkage at each step of solidi?cation is thus fed
by liquid feed metal being drawn out of the riser. (Kalpakjian, S. & Steven, 2009) Figure 2.8 shown the direction and progressive solidification in
casting.

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