How to make a pattern in in casting process

1. ME 2170: Manufacturing Engineering II
Semester: 4
Familiarization with metal Casting - II
By
Index no. Name Marks
170164U M.P.B. FERNANDO
Date of Submission 04.12.2019
Due Date of Submission 04.12.2019
Advisors’/Instructors’ Names Signature
Mr. K.M.B. Rathnasooriya
Department of Mechanical Engineering
University of Moratuwa
Sri Lanka
ME 2170: Manufacturing Engineering II
Semester: 4
Familiarization with metal Casting - II
By
Index no. Name Marks
170
Date of Submission
Due Date of Submission
Advisors’/Instructors’ Names Signature

2. Conclusion
Metallic casting is one of the main parts of the pattern and is a form of casting. For a variety of
products, we can use a variety of materials to make patterns such as wood, metal (aluminum, steel,
cast iron, brass), plastics and wax. The choice of materials depends on the shape and size of the
casting, the number of castings, the molding method and the ease of molding process. The pattern
can be a single piece or many pieces. So there are many patterns, such as a single piece or pattern,
split pattern, loose-piece pattern, gate pattern, matching plate pattern, flow board pattern, sweep
pattern. The pattern is a molded form but differs in dimensions due to various allowances such as
pattern allowance, draft or paper allowance, machine allowance, distortion or chamber allowance,
and rapping or shaking. Patterns are provided to compensate for the shrinkage of metal, to provide
adequate metal for machinery, and to facilitate molding.
Reference
1. http://mechanicalinventions.blogspot.com/2016/02/different-types-of-pattern-allowances.html
[Accessed 4 Dec. 2019].
2. https://techminy.com/pattern-types/ [Accessed 4 Dec. 2019].
3. https://mechanicalinfo.wordpress.com/2011/10/31/pattern-materials/ [Accessed 4 Dec. 2019].
4. https://www.reliance-foundry.com/blog/what-is-a-casting-pattern#gref [Accessed 4 Dec. 2019].

3. Materials and Methods
Tools
1. Radial arm saw
2. Thickness planer
3. Wood working planner machine
4. Wood lathe machine
5. Bench drill
6. Jointer Planner
Machines
1. Scriber and marking tool
2. Spring Caliper
3. Divider.
4. Boring tools
5. Turning tools
6. Parting-off tools
7. Auger drill bit
Procedure
1. First the mahogany wooden stock was shaped to given size by using the radial arm saw and
thickness planer.
2. The centers on both sides were marked using the marking tool.
3. Chamfers on all edges were made using the jointer planner in the length direction.
4. Then the wooden stock was clamped between live and dead centers to the wooden lathe
machine and round end each side was produced.
5. The round end of the stock was clamped to the lathe chuck and other end was clamped on the
dead center of the machine.
6. The stock was turned into a round shape with the required sizes by measuring using spring
calipers and dividers.
7. By using turning and parting-off tools the base was cut from the right end of the stock.
8. The remaining piece of the stock was drilled and cut to the required depth from the right end
using and auger drill bit that was mounted on the lathe tailstock.
9. The final shape of the hole was made using the boring tool and the outside profile was done
by using a turning tool.
10. Parting off tool was used to cut the final piece from the lathe and the down hole was drilled
using the bench drill.
11. Finally, the two pieces were assembled together to finish the making of flower vase pattern.

4. Summary
In sand casting pattern making is significant and example can be utilized as a model for the genuine
casting item. Example is just used to make the cavity of the casting and the size of the example is
contrasting from the first casting so as to permit the metal for recoil and give adequate metal to
completing tasks. These called as allowance and there are various kinds of allowance like, design
stipend, machine allowance, decrease allowance and twisting recompense. Despite the fact that for
making design it can utilized wood just as metals like Aluminum, metal, steel and cast iron
however in this lab practice we just concentration about the wood designs. When making the wood
design for small vase, there are loads of pattern making tasks just as forming and turning activities
were performed so as to get the best completing and get the higher exactness in the pattern. What's
more, different machines like spiral arm saw, wood lathe, wood working planer machines are
utilized for different tasks and furthermore utilized various kinds of molding and going apparatuses
to acquire the ideal wrapping up. As the pattern make as two pieces, the assembling procedure is
performed and complete the pattern making.
Introduction
Casting is the process of pouring liquid metal into a mould, where it cools and solidifies. The
casting process can produce everything from art pieces to engine parts. The shape is determined by
the mould cavity, but something needs to shape the mould—that’s where the pattern comes in.
Patterns are a model for the object to be cast. A pattern makes an impression on the mould, liquid
metal is poured into the mould, and the metal solidifies in the shape of the original pattern.
Patternmaking isn’t as simple as the definition suggests. In addition to shaping the mould cavity, a
pattern must provide accurate dimensions, have means of exiting the mould cavity without
breaking it, compensate for solidification shrinkage and distortion, and include a feeding system of
gates and risers to deliver liquid metal into the mould. Any flaw can result in a failed casting.
Getting all those factors right requires precision and more than a few calculations. Each pattern is
carefully designed and constructed.
The metal foundries usually use wooden patterns to make samples. Because of its cheap cost, easy
modification and quick delivery. According to the different complex, one set of wooden patterns
will use about 3 to 10 days to complete. The wooden pattern has a very short lifetime. They usually
can make only hundreds of castings. However, you must store them very carefully. Even so, they
will have deformation after a period time. Therefore, they cannot be used for batch production. In
addition, their strength is limited, so they cannot make some castings with very thin wall thickness
and some special structures.
In this practical we familiarized with make a wood pattern of a flower vase.

5. Distortion or Camber Allowance
During cooling of the casting, stresses developed in the solid metal which induces distortions in the
cast, If the casting is thinner in width as compared to its length and having irregular shapes such as
U shape, T shape or those who having large flat areas. This can be avoided by initially distorting
the pattern in the opposite direction. This change in casting dimension is known as distortion or
camber allowance. Distortion allowance is given to the pattern by judgment and experience of
pattern maker.
Rapping or Shaking Allowance
A pattern is rapped all around the faces, during removal of the pattern from the mould cavity, to
remove pattern easily. Due to this, cavity in the mould is slightly increased. It is ignored while
casting having an average size but in large casting size and when casting is required of precise size
then rapping or shaking allowance is consider by making a pattern slightly smaller.

6. A pattern is replica of casting but it has slightly different dimensions than casting. These
differences are known as pattern allowances. Pattern allowances are given to the pattern to
compensate metal shrinkage, to provide sufficient metal for machining, to facilitate moulding, etc..
Shrinkage Allowance
When any metal cools from liquid to solid state, it naturally shrinks in size. If the actual object is
used for the pattern, resulting casting size would be slightly smaller than desired size. To overcome
this shrinkage problem, shrinkage allowance is considered while designing a pattern and due to this
pattern is slightly larger than casting.
Draft Allowance
When a pattern is drawn out from a mould, then the surface of mould in contact with pattern is
damages, if the surface is parallel to the direction at which pattern withdrawn. To avoid this, taper
is given to this surface. This tapering of the sides of pattern is known as draft. This allows easy
removal of pattern from mould. The amount of draft is required, depends upon the shape and size
of casting, moulding method, complexity of pattern.
Machining Allowance
Casting is not a final or finish product. To convert casting into finish product, casting is going
through some machining or finishing operations. In machining operation some amount of material
is removed from casting, this factor is considered while designing a pattern and pattern is design
slightly larger than required dimensions this is known as finishing allowance or machining
allowance.

7. Multi piece pattern:
It is one type of pattern types. When complicated part molded together, to require a sand casting
pattern making in more than two parts in order to casting process with easily withdrawal and mold.
This pattern contain may be three, or more number of pattern based on the design. For following
example of multi piece pattern.It is having three piece patterns. The top part is cope, bottom is drag
and middle part of molding box is called check. They are three pattern will be connected by using
dowel pins and molding box clamped by using clamp.
Gated pattern:
To make multiple parts with in single mold and single pattern for all the part cavity of mold. The
multi cavity mold is prepared a single sand mold carries a multiple number of cavities. The gates
are used to connect the pattern each other. The suitable gates or channels are provided for feeding
the molten metal into cavity. All the cavity are feed by using single runner. It mainly consider for
low molding time and uniformly feeding of molten metal. It used for mass production of small
casting.
Loosepiece pattern:
A single piece are made to have loose piece in easy to allow withdrawal from the mold the molding
process are completed, after the main pattern is withdrawn leaving from that piece in the sand.
After the withdrawal of piece from mold, it cavity separately formed by the pattern. It loose piece
pattern is highly skilled job and expensive.

8. The pattern types in casting process depends on the part to be manufactured. The sand casting
pattern making will be easy remove from the mold without any damage in the mould product. It is
based on design patterns material and more.
Solid pattern:
The solid pattern types is a most and simple method for simple shape casting. Its pattern can make
without any sub-part or joint in the mould part. In this type of pattern only produce simple shape
and withdrawn for very easily from the mould. The solid pattern placed in the drag position. That is
used for making a flat surface like as gear blanks, square blocks and more.it solid pattern made
depend on design patterns material, shape and more.
Split pattern:
When contour of casting manufacture. The sand-casting pattern making withdraw from the mould
is difficult or when the part depth too high in the casting. The pattern is split into two half part. For
one half is contained in the drag and another one in cope. For intricate shape part manufactured
using the two or more pattern pieces. The dowel pins used to piece are aligning together. This
pattern types are known as split pattern. The split pattern is common method for intricate casting
part to produce. The two halves of pattern to align properly by using dowel pin. It placed on the top
half of pattern. The split pattern is above figure.

9. Plastic Patterns:
A plastic material is high in use, but they are not safe and not used at high temperatures.
Advantages of Plastic Patterns:
 Pattern making with plastic is low in weight.
 Plastic can obtain to high accuracy in dimensions.
 This type of patterns are strong and smooth.
 Plastic patterns have not to effect from nature like corrosion, rust, moisture etc...
 This type of patterns has a long life without protection.
 Handling is easy.
Disadvantages of plastic Patterns:
 Plastic patterns are not useful at higher temperatures.
 Stronger plastic materials are more costly to use.
According to the above compare and contrast of advantages and disadvantages, we can make
following conclusions.
Wood patterns can be used where high surface finish is required. For an example, sand
casting wood patterns are used in reusable pattern casting processes. Making the wood patterns are
easy comparatively. Patten is easy to machine so in casting applications it is a time saver.
As meatal parts are reusable and durability is very high, they are used in die casting
processes. They are used in whee high number of castings and production rates are required. They
are used where better surface finish and higher dimensional accuracy required. Large number of
moulds can be produced using one metal pattern.
Plastic patterns are strong and smooth. This type is use in investment casting because of
their characteristics. Plastic patterns cannot be used in high heat casting processes because of its
melting quality. It will not crack, curl, or become frayed like paper. It is easy to cut, mark, and
notch. For computerized pattern scribers, Material Concepts recommend pattern plastic

10. Discussion
The main pattern materials are wood, metal and plastic. The selection of pattern material depends
on the size, complexity of pattern, dimensional accuracy required, and volume of the casting need
to be made from the pattern.
Wood Patterns:
Wood is the most common material used in making a pattern, this type of material is easy in
making patterns. to make wood into a pattern, it should dry properly.
Advantages of Wood Patterns:
 Wood is highly available in nature and less cost.
 Making patterns is easy.
 We can obtain to a high surface finish easily with less effort.
 Wood can construct into different forms easily.
 They have comparatively more strength to weight ratio.
 This type of pattern material is easy to machine.
Disadvantages of Wood Patterns:
 Wood material is not high accuracy in dimensions we required.
 This material should handle with care and smooth.
 It has less wear resistance.
 Wood has low abrasion resistance.
Metal Patterns:
Metal patterns are one of the strong and hard patterns and these patterns are more costly than
different types pattern materials.
Advantages of Metal Patterns:
 Metal patterns are comparatively stronger.
 We can obtain high surface finish.
 Metals can obtain to high dimensional accuracy.
 They are more resistant to wear, corrosion etc...
 Metals can be stored for long periods than wood.
Disadvantages of Metal Patterns:
 Metals are more weight; it is not easy to handle.
 They are high in cost compared to many pattern materials.
 Pattern should take care to avoid any damages like corrosion, deformation etc.