M&C Questions
• What is the function of core in the molding?
Castings often required hollow surfaces and recesses etc. of different sizes and
shapes. Theses impressions can be obtained by using cores.
Cores are separately made by packing sand and using binder in boxes known as
core boxes.
• Define modulus of a casting?
Modulus of a casting is defined as “Volume of a casting divided by its cooling surface area”.
This physical relationship is first defined by Chvorinov's in 1940. Mathematically it can be
written as;
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑐𝑎𝑠𝑡𝑖𝑛𝑔
Modulus= M =
𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑐𝑎𝑠𝑡𝑖𝑛𝑔
• Describe design advantages of casting process?
• Size
Casting weight from few grams to tones can be made. In fact casting is the only method
available for producing massive objects in one single piece.
• Complexity
Complex and intricate shapes can easily be cast e.g., curved surfaces inside or outside which
would otherwise be very difficult or impossible to machine, forge or fabricate can usually be
cast.
• Weight Saving
AS the metal can be placed exactly where it is required, large saving in weight is
achieved. Such weight saving leads to increased efficiency in transportation and
economy in transport charges
• Production of prototypes
Easy to produced models or prototypes required for creating new designs
• Wide range of properties and versatility
Casting offer the most complete range of mechanical and physical properties available in
metals. Almost any requirement such as mechanical strength, wear resistance, hardness,
strength-to-weight ratio, corrosion resistance, electrical and thermal conductivity can be
satisfied by cast alloys.
Describe the steps involve in making sand mold?
There are number of methods available to produced mold cavity, the simplest method
is to produced mold by using sand. The basic steps involved in making sand mold are:
1. Pattern making (Including core boxes to make core)
Patterns are used to make mold.
The mold is made by packing molding sand around the pattern.
When the pattern is withdrawn its imprint provide the mold cavity.
Finally, the mold cavity is filled by molten metal to produced required shape.
Thus, for molding the first step is pattern making.
2. Core making
Cores are the materials used to produced cavities and hollow projections which cannot
normally be produced by the pattern alone.
or Cores are used to form interior surfaces of the castings.
Cores are usually made from sand, but sometimes metallic cores are also used
Core boxes (normally made of wood) are required to produced cores.
3. Molding
All the operations which are necessary to prepare a mold for receiving molten metal.
It involves sprinkling and ramming the molding aggregate around a pattern which was
held within a supporting frame.
Withdrawing the pattern to leave mold cavity
The mold is than ready for pouring
4. Melting and Pouring
The preparation of molten metal for casting is referred to simply as melting.
For melting the metal and alloys furnaces are employed.
Melting is sometimes done in ambient condition and under controlled environment as
well i.e. vacuum
5. Cleaning and Inspection
The operations necessary for the removal of the sand and excess metal from the casting
The cast part is removed from the molding sand and transported to the cleaning
department
Excess metal in the form of fins and gating are cut off.
This will improve the appearance and surface finish of the casting
Defective castings are removed during inspection
6. Machining (if required)
7. Heat treatment (if required)
• Differentiate between different types of foundries?
Classification based on nature of work
Write the function of a jobbing foundry?
I. Jobbing Foundry
Jobbing foundry having a physical plant that usually contracts to produced casting or a
small number of castings of a given kind.
II. Production Foundry
A production foundry is a highly mechanized foundry which require that large numbers
of a given kind of casting be made in order to produced them at low cost.
III. Semi-production Foundry
These are the foundries where a portion of the work is of jobbing nature and balance is
production castings
IV. Captive Foundry
This type of foundry is an integral part of some manufacturing company and whose
castings are mainly consumed in the products of the parent organization.
V. Independent Foundry
It is usually a separate company that produced castings for any number of customers
• What is a gating?
The gating system is a set of channels and passages that are designed in a metal casting mold
to control the flow of molten metal into the mold cavity. It helps to ensure that the metal fills
the mold uniformly and completely, while minimizing defects such as porosity or shrinkage.
The gating system typically includes a sprue, runner, and gating components such as gates,
vents, and risers.
What are core prints?
The core print is an added projection on the pattern, and it forms a seat in the mold in
which the sand core rests during the pouring of the mold. The core print must be of
adequate size and shape so that it can support the weight of the core during casting
operation.
