1. ME8352: MANUFACTURING TECHNOLOGY-I
PATTERN AND THEIR TYPES
Presented by
S.Kannan
Assistant Professor
Department of Mechanical Engineering
Vel Tech Engineering College
Avadi-Chennai-62
2. INTRODUCTION TO CASTING
• Casting is a manufacturing process by which a liquid
material is usually poured into a mold, which
contains a hollow cavity of the desired shape, and
then allowed to solidify.
• It is most ancient process of manufacturing metallic
components.
4. PATTERNS
• In casting, a pattern is a replica of the object to be
cast, used to prepare the cavity into which molten
material will be poured during the casting process.
• It is not exact replica of the exact desired casting.
• It is slightly larger than the desired casting, because
of allowances.
6. TYPES OF PATTERN
1. Single piece pattern: It is simplest of all pattern is
made in one piece. It is suited for limited process only.
2. Spilt piece pattern: It is used for intricate casting for
usual shapes. These two patterns are joined together
with the help of dowel pins.
7. TYPES OF PATTERN
3. Loose piece pattern: Some patterns usually single piece
are made to have loose pieces in order to enable their
easy with drawn from the mould.
8. TYPES OF PATTERN
4. Gate pattern
It is simply one or more loose patterns
Having attached gates and runners.
5. Match plate pattern
It is a split pattern having the cope
And drags portions mounted on
opposite sides of a plate
(usually metallic),Called as match plate.
9. TYPES OF PATTERN
6. Sweep pattern
A sweep is a section or board
(wooden) of proper contour that is
rotated about one edge to shape
mould cavities having shapes of
rotational symmetry.
7. Skeleton pattern
sweep patterns, these are simple wooden
frames that outline the shape of the part to
be cast and are also used as guides by the
molder in the hand shaping of the mould.
10. TYPES OF PATTERN
8. Follow pattern
Follow board pattern consists of tool that is a simple
wooden board which is used in processes where
casting structures are weak and they may break after
the application of force.
11. TYPES OF PATTERN
9. Shell pattern
Shell pattern is specially
used for obtaining hollow
shaped structure. Along the
center the parting process is
done
12. REQUIREMENTS OF A GOOD PATTERN
• Secure the desired shape and size of the casting.
• Cheap and readily repairable.
• Simple in design for ease of manufacture.
• Light in mass and convenient to handle.
• Have high strength and long life in order to
make as many moulds as required.
• Retain its dimensions and rigidity during the
definite service life.
• Its surface should be smooth and wear resistant.
• Able to withstand rough handling.
13. DESIGN CONSIDERATION IN PATTERNS
1. Proper allowance should be provided.
2. The parting line should be carefully selected.
3. Proper material should always be selected.
4. The wall thickness and sections should kept as
uniform as possible. Abrupt changes should invariably
be avoided.
5. The use of offset pairing, instead of cores, should be
encouraged to as great extent as it is possible. Abrupt
changes should invariably be avoided.
14. PATTERN LAYOUT
Pattern making consists of two different stages to prepare
a layout and to shape the different parts. Layout consists
of the following steps:
a. Initially study the drawing pattern and select a wood
that can suitably accommodate two views.
b. Take on surface of the wood as base and plane the
adjacent surface.
c. Take a folding rule and measure the dimensions as per
the drawing.
d. Prepare the layout by using various measuring and
marking tools locating position of core prints and surface
to be machined.
15. PATTERN MATERIALS
• Wood: Piece and short run production
• Metal: Large scale and mass production
• Cement, Plastics for example epoxy resin: Batch
production.
16. ALLOWANCEs
1.Shrinkage allowance
After solidification of the metal from further cooling (room
temp.) dimensions of the patterns increases. So pattern size is
bigger than that of the finished cast products.
2.Machining allowance
Machining allowance or finish allowance indicates how much
larger the rough casting should be over the finished casting to allow
sufficient material to insure that machining will "clean up" the
surfaces.
17. 3.Draft or tapper allowance
Pattern draft is the taper placed on the pattern surfaces
that are parallel to the direction in which the pattern is
withdrawn from the mould to allow removal of the pattern
without damaging the mould cavity
4.Distortion allowance
This allowance is taken into consideration when casting
products of irregular shapes. When these are cooled they are
distorted due to metal shrinkage
18. 5.Rapping or shake allowance
To take the pattern out of the mould cavity it is
slightly rapped to detach it from the mould cavity. So
the cavity is increased a little.
