Foundary Notes

7/31/2019 Foundary Notes

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FOUNDARY SHOP

General Objectives

On completion of this module the trainee should be able to:

1. Understand the safety aspect of foundry work

2. Understand the working principles of common foundry tools and devices

3. Understand the principles, types and techniques of foundry work

4. Know foundry materials, their composition, properties and applications.

Student Outcome:

On completion of this module, the student will be able to

1. Comply with safety rules and regulations in foundry workshop

2. Effectively utilize common foundry tools and devices

3. Apply different principles, types and techniques in foundry operation4. Identify foundry materials and their composition

5. Use foundry materials effective

INTRODUCTION

A foundry is where the elaborate metal casting process takes place. A metal foundry may

specialize in making one particular item or a variety of products using different alloys. Based

on the production requirement, there are small foundries that employ

few people and large industrial foundries that employ thousands of

workers. A foundry is a factory which produces metal casting from

either ferrous or non-ferrousalloys. Metals are turned into parts by

melting the metal into a liquid, pouring the metal in a mold, and then

removing the mold material or casting. The most common metal

alloys processed are aluminium and cast iron. However, other

metals, such as steel, magnesium, copper, tin, andzinc, can be

processed.

PATTERN

Incasting, 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 patterns used insand castingmay

be made of wood, metal, plastics or other materials.

Functions of a pattern:-

The main functions of a pattern are:-

1. To produce the mould cavity of appropriate shape and size.

2. To produce seats for cores is which cores can be placed.

3. To establish the parting surfaces and lines in the mould

4.

To minimize defects in castings

5. To minimize the cost of casting.
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TYPE OF PATTERNS:-

Single piece pattern

Split pattern

Cope and drag pattern

Match plate patternGated pattern

Loose piece pattern

Sweep pattern

Skeleton pattern

Segmental pattern

Shell pattern

1. Single piece pattern.

A single piece pattern is the simplest of all forms. As the name indicates they are made of a

single piece as shown in fig. This type of pattern is used only in cases where the product isvery simple and can be easily withdrawn from the mould. This pattern is contained entirely in

the drag. One of the surfaces is usually flat which is used as the parting plane.

2. Split pattern or two-piece pattern

This is the most common type of pattern for intricate castings. When the contour of the

casting makes its withdrawal from the mould difficult or when the depth of the casting is too

high,then the pattern is split into two parts. One part is contained in the drag and the other

in the cope. The split surface of the pattern is same as the parting plane of the mould. The two

halves of the pattern should be aligned properly by making use of dowel pins which are fitted

to the top half.

3. Cope and Drag Pattern

When very large castings are to be made the complete pattern becomes too heavy to be

handled by a single operator. Such a pattern is made in two parts which are separately

moulded in different moulding boxes. After completion of the moulds, the two boxes are

assembled to form the complete cavity. One part is contained by the drag and the other by the
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cope. Thus it is different from split pattern in which both pieces are moulded separately

instead of being moulded in the assembled position.

4. Match plate pattern

These patterns are made in two pieces. One piece is mounted on one side and the other on the

other side of a plate called match plate. Gates and runners are also attached to the plate along

with the pattern. After moulding when the match plate is removed a complete mould with

gating is obtained by joining the cope and drag together. The complete pattern with match

plate is entirely made of metal, usually aluminium for its light weight and

machinability. These are generally used for mass production of small castings with higher

dimensional accuracy. These patterns are mainly employed for machine moulding..

6. Gated Pattern

They are used for mass production of small castings. For such castings multi-cavity moulds

are prepared, i.e. a single sand mould carriers a number of cavities as shown in fig. Pattern

for these castings are connected to each other by means of gate formers. They provide

suitable channels or gates in sand for feeding the molten metal to these cavities.

Sweep Pattern:-

Sweep pattern can be advantageously used for preparing moulds of large symmetrical

castings, particularly of circular cross section. The equipment consists of abase, suitablyplaced in the sand mass, a vertical spindle and a wooden template called sweep. The outer

end of the sweep carries the contour corresponding to the shape of the desired casting. The

sweep is rotated about the spindle to form the cavity as shown in fig. Then the sweep and

spindle are removed leaving the base in the sand. The hole made by the removal of spindle is

patched up by filling the sand.
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9. Pattern with Loose Pieces

Certain single piece patterns are made to have loose pieces in order to enable their easy

withdrawal from the mould. These pieces from an integral part of the pattern during

moulding. After the mould is complete the pattern is withdrawn leaving the pieces in the

sand. These pieces are later withdrawn separately through the cavity formed by the pattern asshown in figure. Moulding with loose piece is a highly skilled job and is generally expensive.

10. Follow board pattern

Some castings have certain portions which are structurally weak. If those portion of thepattern is not supported properly they are likely to break under the force of ramming. In this

case a special type of pattern called follow board pattern is adopted. A follow board is a

wooden board used to support a pattern during moulding. It acts as a seat for the pattern.

11. Segmental Pattern

Those pattern are used for preparing moulds of large circular castings, avoid the use of a

solid pattern of exact size. In principle they are similar to sweep patterns. But the difference

is that while a sweep pattern is given a continuous revolving motion to generate the desired

shape, a segmental pattern is a portion of the solid pattern itself and the mould is prepared in

parts by it. It is mounted on a central pivot and after preparing the part mould in one position,the segment is moved to the next position. The operation is repeated till the complete mould

is ready.
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Pattern materials:-

The common pattern materials are wood, metals, plaster, plastics and wax.

(1) Wood

Is the most common material used for pattern making because of the following advantages.

(a) It is cheap and available in abundance

(b)It can be easily shaped into any required design.

(c)It is light in weight

(d)Good surface finish can be easily obtained

(e)It has fanty long life.

But wood has got certain disadvantages also.

i. It wears out quickly.

ii. It is very susceptible to moisture

(2) Metals

Metals are usually employed as pattern material when large number of casings is to be made

and close dimensional accuracy is desired. They have longer life than wooden patterns. The

common metal used as pattern materials are aluminum alloys, Grey cast iron, Steel, leadalloys and brass and bronze.


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(3) Plastics

Plastics are used as pattern materials because of their low weight, easier formability, smooth

surfaces and durability. They do not absorb moisture. They are dimensionally stable and can

be easily cleaned. Plastic patters can be made in sand, clay moulds or moulds made of plaster

of paris. The most generally used plastics are cold setting epoxy rins with suitable fillers.

(4) Plaster

Plaster of Paris or gypsum cement is used as pattern material since it can be easily cast intoany shape. Its expansion can be easily controlled and it carries a very -high compression

strength. Plaster of paris expands on being solidified. So if a plaster of proper coefficient of

expansion is selected the effect of shrinkage of casting can be automatically neutralized.

(5) Wax

Wax patterns are exclusively used in investment casings. For this a die or metal mould is

made in two halves. Then heated wax is poured into it. The die is kept cold by circulating

water around it. As the wax sets on cooling the die parts are separated and wax pattern taken

out. Any complex shaped pattern of any size can be conveniently produced by this method.

Foundary Tools :-

HAND TOOLS:

Shovel:
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A shovel is used for mixing and tempering moulding sand and for moving the sand from the pile

to flask.

Riddle:

A riddle some times called a screen consists of a circular or square wooden frame fitted with a

standard wiremesh. It is used to remove foreign materials such as nails, splinters etc

Rammer:

A hand rammer used for packing and ramming the sand into the mould, one end called the peen,

wedge shaped and opposite end called the butt, has a flat surfaces.

Trowel:A trowel consists of a metal blade fitted with the wooden handle; it is used to smooth on sleek

over the surfaces of moulds.

Slick:It is small double ended tool having a flat on one end and a spoon on the other end. It is used for

repairing and finishing small surfaces of the mould.

Lifter:

Lifters are made of thin section of steel of various widths and lengths. This is used to clean andfinish the bottom and sides of deep, narrow opening in mould.

Strike-off-bar:

This is a piece of metal may by wood used to strike-off-excess sand from the mould after

ramming to provide a level surface.


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Pin:

A pin is a tapered peg pushed through the cope to the joint of the mould. The pins forms the

runner and riser in cope

Bellow:

Bellows are used to flow loose particles of sand from the pattern and the mouldcavity.

Swab:

A simple swab is a small brush having long hemp filters, a full swab has a rubber bulb to hold the

water and a soft hair brush at the open end.

Gate cutter:It is a small piece of tin plate shaped as a knife. It serves as a tool for cutting gates and runner in

the mould.

Vent rod:

A vent rod used to make a series of small holes permit gases to escape while the molten metal in

being poured.

Draw spike:

The draw spike is a pointed steel rod with a loop at one end. It is used to rap and draw patterns

from the sand.

FLASKS:Sand moulds are prepared in specially constructed boxes called flasks. The purpose of the flask is

to impart the necessary rigidity and strength to the sand in moulding.They are usually made in

two parts held in alignment by dowel pins. The top part is called the cope and the lower part is

called drag. If the flask is made in three sections, the center is called the cheek. These flasks can

be made of either wood or metals depending upon the size required and the purpose of flasks

must serve.

Casting Defects:-


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1. Flash

This casting shows a very common defect, flash. This is where the mold somehow

seperated enough to allow metal between the halves, along the parting line.

2. Mold Shift

This is due to operator error: not aligning the mold correctly. Most

flasks have alignment pins to prevent this,

3. Porosity

This is an investment casting. Different from sand casting, but defects still

happen all the same. In this case, it was either gas or slag. There are actually

a few pinholes which you can see light clear though in the porous area.

4. Inclusions

Still on the same casting, this is the bottom plate. This is much more of a

problem in sand molds, since loose sand can easily be abraded off and letloose in the mold cavity. Makes for a bad finish on (usually) the drag side of

the casting.

5. Short Casting


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This is usually caused by the metal solidifying before it fills the cavity - the

metal was too cold. It could also be a restriction: too small a sprue, gate, or

not enough venting keeping the metal from going in.

MOULDING SANDS

Foundary sands are of two types:

1.NATURAL SAND:It contains sufficient amount of bimding clay and therefore,no more binder

is required.

2.SYNTHETIC SAND:When mixed with other constituents like binders and additives are

known as synthetic sand.

TYPES OF MOULDING SANDS:

1.GREEN SAND:It is fine,soft,light and porous sand and contains moisture 6 to 8 % water with

18 to 30 % clay to give sufficient bond.

2.DRY SAND:Moulding sand contains excess moisture but has been evaporated from it by

drying in suitable oven is called dry sand.

3.FACING SAND:It is asand which forms the face of the mould made up of silica sand and clay

without addition of used sand.

4.PARTING SAND:It is used to keep the green sand from sticking to the pattern and also to

allow the sand to seprate the cope and drag without clinging on parting surface.

5.LOAM SAND:It is clay (50%) and dries hard.

6.FLOOR SAND OR BRAKING SAND:It is used to backup the facing sand and to fill up

whole volume of flask.

7.SYSTEM SAND:In mechanical sand prepration and handling units, nofacing sand is used.The

used sand is cleaned and ractivated by addition of water binders and special additives.

8.CORE SAND:The sand which is used for making core and carries a silica content is known as

core sand.


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9.OIL SAND.

10.MOLASSES SAND.

CHARACTERSTICS OF MOULDING SAND

1.Porosity or permeability.

2.Collasibility.

3.Flow-ability.

4.Adhsiveness.

5.Cohesiveness.

6.Refractoriness.

7.Other properties:

(a)It should be cheap and easily available.

(b)Coefficient of expansion should be low.

(c)It should be reusable.(d)It should not react chemically.

CONSTITUTENTS OF MOULDING SAND

1.Silica sand:Silica sand contains water for a long time and suitable for a wide range.It is very

cheap and used for cast iron and non ferrous meatls castings.

2.Binders:To impart sufficient strength and cohesiveness in moulding sand binders are added.

Ex-Dextrin, Molasses,Resins,Ball clayFire clay etc.

3.Additives.Materials which are to moulding sand to improve the existing properties or to impart

certain new properties.Ex-Coal dust,Sea coal,Pitch,Cereals,Silica flour,Wood flour etc.

4.Water.Clay content added to the foundary sand will not give the required strength an bond until

a sitable quantity of water is added to it.Quantity of water varies from 2 to 8%.

5.Sand mould:

(A)Green sand moulds:

(B)Dry sand moulds

(C)Skin dried mould

MOULD PROCEDURE:

The procedure for making a mould in either green or dry sand is as follows.

1.First of all a suitable flask is selected ,large enough to accommodate the pattern and also

allow some space around it for ramming of sand.

2.The drag part is placed upside down on moulding board.

3.the pattern is placed on the board inside the flask in such a position that space is left for

gatecutting.

4.If in 2 parts,the lower part of the pattern is placed in the drag.

5.If facing sand is is used,it is placed all along the pattern surface tosuitable depth(say25mm).


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6.The drag is then filled with ordinary moulding sand and rammed properly.

7.The excess sand is cut-off to bring it in level with the edgesof the flask.

8.A small amount of dry loose sand is sprinkled over the top surface and the drag turned

upside down,along with the bottom board placed over it,after venting.

9.The cope I sthen placed over the drag and the top part of the pattern(if it is in two parts)assembeled in position.

10.Dry loose parting sand is then sprinkled over the entire surface of the drag and pattern.

11.Runner and risers are put in positions and supported vertically by tuckling a small amount

of moulding sand around them.

12.The facing sand,if used,is again put around the pattern surface to the usual depth.

13.Excess sand is then cut off,runner and risers pin then removed,venting performed,pouring

basin formed and dry sand sprinkled on the top surface.

14.A bottom board is placed over the cope and the latter rolled over.

15.The pattern parts are then removed from both th drag and cope.

EXPERIMENT NO:

AIM:

To make a green sand moulding for the given Single Piece Pattern.

TOOLS REQUIRED:

Moulding box, Mouldin board, Shovel, Rammer, Runner, Vent wire, Lifter,

Bellows, Swab, Slicks, Gate cutter, Draw spike, Mallet

SAFETY DEVICES:

1. Hand gloves.

2. Goggles.

3. Shoes.

PRECAUTION FOR PERSONAL AND MACHINE SAFETY:

1. Hand gloves and shoes must be worn charging the furnace.

2. Goggles should be worn during cleaning of casting by grinding and chipping.

3. Heat resistance clothing should be used while handling molten metal.

4. The first air box should be kept ready for use.

PROCEDURE:

1) The moulding sand is properly tempered before prepare the green sand hand moulding.2) Prepare the drag box or foundry floor and partially filled with green sand to from the

mould cavity.

3) To ensure that the sand is properly compacted and bedded in single piece solid pattern in

suitable method.

4) Ramming the sand carefully on all area around the pattern and necessary to ram closer to

the pattern.

5) For check, pattern can be drawn and the mould cavity surface tested for soft spots.

6) All soft spots should be filled with extra sand and the pattern again pressed in its cavity

until properly rammed mould cavity is obtained.

7) Use strike-off bar on the drag to found the smooth surface and spread the parting sand. In

case of typical drag in mould box set has tilted the drag box and found the smooth surfaceand spread the parting sand by turn over method mould preparation.


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8) The cope is placed over the drag as well as suitable to pattern.

9) The runner and riser pins are located and the cope is filled with moulding sand.

10)Made required marks over drag and cope.

11) The cope is rammed up carefully all area and around the spure pins.

12)After checking the proper ramming taken out the runner and riser carefully and taken out

the cope box from drag.13) The pattern is drawn out from drag carefully by using spike and mallet.

14)Make a suitable gate by using gate cutter and make it smooth ideal profile.

15)Make necessary vent holes on smooth surfaces of cope and drag.

16)And the cope is replaced in its correct position and complete the mould.

RESULT:

Thus the green sand mould was prepared for the given Single Piece Pattern

pattern.

Foundary Notes

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