Department of Mechanical Engineering
MANIT Bhopal
ME 223 Manufacturing Processes 1
(Section M1)
Assignment #1
Q.1: As we know that design of risers is an important task for the casting processes in manufacturing
industries. As discussed in the class, the purpose of riser is to provide liquid metal to compensate liquid
and shrinkage during phase change, the secondary purpose of riser is to show that whether casting is
full or not. So the riser design should be such that it solidify after casting, so that liquid metal is available
to compensate shrinkage. The solidification time for both riser and casting can be expressed as:
2
V
t (1.1)
A
where V is the volume of riser and A is the surface area of riser. (a) compare the solidification time of
two optimum side and top riser, one is cylindrical and other is square parellopipe, and (b) determine the
dimensions of a cylindrical side and top riser used for casting brass cube of 20 cm dimension. The
volume shrinkage can be taken as 9%.
Q.2: A round casting is 200 mm in diameter and 750 mm in length. Another casting of the same metal is
elliptical in cross-section, with a major-to-minor axis ratio of 2, and has the same length and cross-
section area as the round casting. Both pieces are cast under the same conditions. What is the
difference in the solidification times of the two castings?
Q.3: If you need only few units of a particular casting, which process(es) would you use? Why?
Q.4: Rank the casting processes such as die casting (cold chamber), squeeze casting, centrifugal casting,
slush casting, die casting (hot chamber) and permanent casting interms of their solidification rate. That
is, which processes extract heat the fastest from a given volume of metal?
Q.5: The blank for the spool shown in Figure A1.1 is to be sand cast out of A-319 aluminum casting alloy:
Figure A1.1
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(a) Make a sketch of the wooden pattern for this part, and include all necessary allowance for shrinkage
and machining.
(b) In sand casting, it is important that the cope-mold half be weighted down with sufficient force to
keep it from floating when the molten metal is poured in. For the casting shown in Figure A1.2, calculate
the minimum amount of weight necessary to keep the cope from floating up as the molten metal is
poured in.
Section A-A Material: Low-carbon steel
Density: 7197 kg/m3
All dimensions in mm
Figure A1.2
Q.6: The gating systems are used to push the liquid metal into mould cavity. The detailed process is
shown in the Figure A1.3. Generally three types of gates names top gating, bottom gating and horizontal
gating.
Figure A1.3
(a) Design the sprue to avoid the aspiration effect with the application Bernoullis equation for top and
bottom gates.
(b) Considering a casting of size (100 100 25) cm3 was filled by top and bottom gates with
manometric height in pouring basin to be 25 cm. Compare the time to fill the casting by different gates.
The area of gate is 5 cm2. Also, determine the total time required to full the entire casting and riser.
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Q.7: Gating system design for casting thin aluminium alloy (Al-Si) plates as shown in Figure A1.4.
(a)
(b)
Figure A1.4 (a) Schematics of the mould cavities of plates A,B,C and D and the Gating, and (b) Casting
after cleaning
(a) Materials: wood, glue (Alteco 110), Aluminium (Al-Si-Mn-Mg-Cu) alloy scraps, silica sand (River sand),
betonies (Clay), water and additive (wood ash).
(b) Equipment: Coal fired Crucible Melting furnace
(c) Gating Design Calculations: The methods that will be use for this study is the principle of gating
system design calculations according to:
As:Ar:Ag=1:4:4 (Non pressurized gating ratio) (7.1)
where As is the cross sectional area of the sprue exit, Ar is the cross sectional area of the Runner(s) and
Ag is the cross sectional area of the ingate(s). The choke (the smallest cross sectional area) is at the sprue
base exit therefore.
As=Ac (7.2)
where Ac is the cross sectional area of the choke. Table 1 shows the dimensions of the pattern plates
used in the design of a gating for four thin aluminium alloy plates.
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Table 1 Dimensions of the pattern plates
Plate designation Thickness Length Width Volume
(mm) (mm) (mm) (mm3)
A 4.06 81.28 40.64 13411.07
B 6.10 121.92 60.96 45335.68
C 8.13 162.56 81.28 107420.69
D 10.16 203.20 101.6 209754.42
Based on the above data and assumptions, Calculate:
(i) the total weight of castings.
(ii) the pouring rate and pouring time.
(iii) the effective sprue height.
(iv) the choke cross sectional area.
(v) the sprue inlet area, since sprue exit area Asprue_exit = choke area Ac.
(vi) the Ingates and Runner cross-sectional areas using a gating ratio of 1: 4: 4.
(vii) and design of Sprue well.
Q.8: A jeweler wishes to produce 24 gold rings in one investment casting operation The wax parts are
attached to a wax central sprue 12 mm in diameter. The rings are located in four rows, each 12 mm
diameter from the other on the sprue. The rings require a 3 mm diameter, 12 mm long runners to the
sprue. Estimate the weights of gold needed to completely fill the rings, runners, and sprues. The specific
gravity of gold is 19.3.
Q.9: Assume that you are an instructor covering the topics such casting, design of gating systems,
pattern and pattern making, mould preparations and materials solidification process, and you are giving
a quiz on the numerical aspects of casting processes to test the understanding of the students. Prepare
two quantitative problems and supply the answers.
Q.10: The general design recommendations for a well in sand casting are that (a) its diameter should be
at least twice the exit diameter of the sprue and (b) its depth should be approximately twice the depth
of the runner. Explain the consequences of deviating from these guidelines.
Prepared by Dr. Vinod Yadav
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