1. ME 2170 Manufacturing Engineering II
Semester 4
Familiarisation with metal casting I
by
Index No Name Marks
150131A Dilshan K.M.G.L.
Workshop Name Welding Shop
Course B.Sc Engineering (Hons.)
Department Mechanical Engineering
Group M 1.3
Date of performance 06.09.2017
Date of submission 20.09.2017
Due date of submission 20.09.2017
Department of Mechanical Engineering
University of Moratuwa
Sri Lanka
Practical No: P04
2. Introduction
Manufacturing process in industries, many different processes or manufacturing
methods are used. To be able to select the technically and economically best manufacturing
sequence for a product, it is necessary to have a broad fundamental knowledge of the
possibilities and limitations of the various manufacturing processes, including work materials
used and geometries, surface finishes and tolerance required. The team process can in general
be defines as a change in the properties of an object, including geometry, hardness, stat,
information content and so on.
Casting on of the oldest manufacturing processes. It basically involves the introduction
of molten metal into a mold cavity, where upon solidification, metal takes on the shape of the
mold cavity.
Here we discuss about the sand casting. Sand casting also known as sand molding
casting is a metal casting process characterized by using sand as the mold material. Sand
casting are produced un specialized factories called foundries.
3. Procedure
There are few processes for sand casting consisting six processes. They are,
1. Mold making
2. Clamping
3. Pouring
4. Cooling
5. Removal
6. Trimming
Mold making
First step is creating the mold for the casting. In expendable mold process this step
must perform for each casting. A sand mold is formed by packing sand into each half of the
mold. The sand is packed around the pattern, which is replica of the eternal shape of the
casting. When the pattern is removed the cavity that will form the casting remains. Any
internal features of the casting that cannot be formed by the pattern are formed by separating
cores which are made of sand prior to the formation of the mold. The mold making time
includes positioning the pattern, packing sand and removing pattern. The mold making time
is affected by the size of the part, the number of cores, and the type of sand mold and type of
and sand mold. If the mold type requires heating or braking time, the mold making time is
substantially increased. Also, lubrication is often applied to the surface of the mold cavity in
order to facilitate removal of the casting. The use of a lubricant also improves the flow the
metal and can improve the surface finish of the casting. The lubricant that is used is chosen
based upon the sand and molten metal temperature.
Clamping
Once the mold has been made, it must be prepared for the molten metal to be poured.
The surface of the mold cavity is first lubricated to facilitate the removal of the casting. Then
the cores are positioned and the mold halves are closed and securely clamped together. It is
essential that the mold halves remain securely closed to prevent the loss of any material.
4. Discussion
Core print
Also known as the projections placed on the pattern to form seat in the mould for
introducing dry sand cores in the mold. Core prints make conception in the form seats into
which the cores may be set and thus placed in the proper position in the mold. When the
alteration of a core in the mold would spoil the casting, the prints are made of such a shape
and size, that would be very hard to set the core in any position except the proper one. Core
prints should be made to afford the east ailment in moulding. It should exactly fit the seat of
core. It also should be of sufficient and will size so that impression in the sand will have
plenty of bearing surface and won’t be crushed out of shape by the weight of the core or by
the molten metal.
Vent hole
Vent hole is a thin long passage while allows the gasses escape from the cavity while
the molten metal is entering to the mould cavity. This is a proper method to avoid having any
trapped gasses inside the casting. Normally the vent hole can be seen at the highest place of
mould cavity once the molten metal enters to the cavity through the pouring basin, the inside
gases are pushed through the vent hole.
Riser
A riser is also known as feeder head. It is a sort of passage in the mould sand,
shrinkage takes place during cooling and solidification of casting. If the casting is allowed to
solidify as it is, there will be a shrinkage cavity formed on the top of the casting. To avoid
happening this, the risers have been introduced. They usually are provided on the top of the
mould cavity.
Main use of a riser
• Compensate for shrinkage cavities formed in casting
• Permit the escape of air and mould gases as the mold is being filled by the molten
metal
• Promote directional solidification
• Get sound casting
5. There are two types of risers
1. Open riser
A conventional type of riser whose top is exposed to the atmosphere. This is
connected either at the top of the cope or on the side at the pouring line
2. Blind riser
It is enclosed by the sand mould and is designed for a least surface area per unit
volume. A vent or permissible core at the top of the atmosphere, gravitational force
is the only feeding force for the liquid metal in the casting. A blind riser can either be
connected on the top of the cope or at the side of the casting in the drag or parting
line.
Advantages of blind riser
• The hottest metal remains in the riser that permits directional solidification
• A blind riser is comparatively smaller than an open riser
• Blind risers can be placed in any position in a mold cavity
• Blind risers can be removed more easily from the castings
• Metal in the riser cools much slower than the metal in a casting
Disadvantages of blind riser
• It is comparatively hard to mould
• A blind riser may trend to draw liquid metal from the solidifying casting
Gating system
Gating system is the basic design. It is introduced to construct a smooth and
appropriate filling of the mould cavity of the casting avoid any discontinuity, voids or any
inclusions. An efficient way of gating system is that is shows the way to the pure molten
metal to flow through the casting cavity which ensures proper and smoother filling of the
cavity. Main elements of a gating systems are as follows
• Pouring basin
• Spure
• Spure well, choke
• Runner
• Ingate
• Ladle
• Slag tap or filter
6. Tools that are used in sand casting which are used by the mold maker
• Shovel
Use to handle and board scoop or blade for digging and mounting material from the
storage to the place where casting is doing
• Drag and cope
Upper part of the casting flask is known as cope, when the lower part of it is known
as drag
• Riddle
A tool which consist of a wooden handle and a bucker which is made of a steel net.
It is used to separate smaller sand from large sand particles. Smaller sand particles are
essential for a smooth mould surface.
• Rammer
This is a tool which has a heavy flat bottom surface which is made of iron. In casting
process, this tool is used to pack the green sand tightly by applying forceful impact.
• Strike off bar
This is normally a wooden bar which has a flat thick bottom. This is used to remove
the additional sand from the mould and flatten it after ramming.
• Dust bag
This is containing powder which is use to sprinkle dust in the middle of the surface
which separate the cope and drag this prevents cope adhesion with drag.
• Lifters
This device uses to lift or put green sand carefully in to the mould cavity. These are
considerably small as it carries a little amount of material form or to the cavity.
• Went wires
It used to create the vent hole. It is having a smaller round cross sectional area.
• Trowel
His is a flat bladed hand tool for levelling spreading or shaping green sand in the
mould. It is used when crating the pouring basin.
7. • Spure pin
This is a wooden piece which is having a descending cross section and conic shape.
This can use to produce the sprue well in mould.
References
Sand casting. (2017, 09 10). Retrieved from Custompart.net:
http://www.custompartnet.com/wu/SandCasting
Serope Kalpakjian, S. S. (2009). Manufacturing, Engineering and Technology. London:
Pearson.
