Foundry Lab

FOUNDRY AND FORGING LAB

Syllabus

Part A ( Sand Testing) Testing of moulding and core sand

Part B (Foundry Practice) Use of foundry tools and other equipments Preparation of moulds using two moulding

boxes

Part C( Forging operations) Preparing minimum three forged models

involving upsetting, drawing and bending operations.

Estimation of length of the raw material

Compression. Tensile and shear tests on universal sand testing machine

Permeability test Hardness tests Sieve analysis Clay content test Moisture content test

MANUFACTURING

“The Process of Converting Raw Materials Into Products”

Manufacturing ?

Manufacturing in its broadest sense is the process of converting raw materials in to useful products

It includes i) Design of the product ii) Selection of raw materials and iii)The sequence of processes

through which the product will be manufactured

Manufacturing Processes

Manufacturing Processes

Casting Machining Forming Joining (Net shapeprimary process)

( Subtractive secondary process)

(Net shapesecondary process)

( Additive secondary process)

Casting Casting is the process of pouring molten metal

in to a mould cavity of required shape & size and allowing for cooling

It involves a series of operations i) Pattern making ii) Core making iii) Mould making iv) Melting v) Pouring vi) Cleaning

Types of casting

Casting

Conventional Methods Unconventional Methods Green sand mould

Dry sand mouldCO2 Moulding (Strong mould)

Permanent (Metal mould)

Shell Moulding (Thinn mould)

Investment casting (Precision)

Centrifugal ( without core)

Continuous Casting (Open)

Advantages & Disadvantages Advantages

Design flexibility

Reduced costs

Dimensional accuracy

Versatility in production

Disadvantages

Lot of molten metal is wasted in riser & gating

Casting may require machining to remove rough surfaces

Machining

Machining of metal involves forcing of cutting tool through the excess material of the workpiece.

The excess material is progressively separated from the workpiece in the form of chips to get required shape

Types of machining

Machining

ConventionalTurning by lathe m/c’sGrinding by grinding m /c’s

UnconventionalEDM, ECM, EBM, LBM

Forming

Shaping of a component by the application of external forces

Metal is deformed plastically under the action of externally applied forces

Types of forming

Forging, rolling, drawing etc

Forming

Explosive forming, Electro hydraulic

Based on working temp

Cold

Hot

Based on stress applied

Compression

Tension

Combined

Shear

Based on energy used

Conventional

Unconventional

Joining

In engineering practice none of the product can be made in a single process the products are assembly of many individual parts

Joining is a general term covering many process like welding, brazing, soldering, riveting and other mechanical fastening methods

Types of joining Joining

Temporary fastening Permanent fastening

Bolts & nuts

Screws

Riveted

Welding

Fusion

Solid state

Soldering

Brazing

Casting

Casting is one of the oldest manufacturing process and even today is the first step in manufacturing most of the products

It is based on the property of a liquid to take up the shape of vessel containing it.

Products ranging from a few mm to several m and

a few grams to several tons

Foundry is the place where metal is melted and casting are produced

Similar to that of making ice cubes in a refrigerator

Casting Terms Pattern- replica of the part to be cast Molding material- material that is packed around

the pattern to provide the mold cavity Flask- rigid frame that holds the molding

aggregate Cope- top half of the pattern Drag- bottom half of the pattern Core- sand or metal shape that is inserted into

the mold to create internal features

Casting Terms Mold cavity- combination of the mold material

and cores Riser-additional void in the mold that provides

additional metal to compensate for shrinkage Gating system- network of channels that delivers

the molten metal to the mold Pouring cup- portion of the gating system that

controls the delivery of the metal Sprue- vertical portion of the gating system Runners- horizontal Parting line- separates the cope and drag

Six Basic Steps of Casting

Pattern making

Core making

Moulding

Melting

Pouring

Cleaning & inspection

The Pattern

A full‑sized model of the part, slightly enlarged to account for shrinkage and machining allowances in the casting

Pattern materials: Wood - common material because it is easy to work,

but it warps Metal - more expensive to make, but lasts much

longer Plastic - compromise between wood and metal Plaster of paris Wax –precision casting

Types of Patterns(a) solid pattern ( single piece)(b) split pattern ( Two piece)(c) match‑plate pattern(d) cope and drag pattern

(e) Sweep pattern

(f) Skeleton pattern

Core in Mold A core consists of two portions: the body of the

core and one or more extensions (called prints) Cores are used to create internal cavities. Core is a separate entity placed in a mould to

produce a corresponding cavity – hole or undercut – in the casting

Cores for sand casting are manufactured by packing specially prepared sand in core boxes

Chaplets

Major part of Moulding material in sand casting are

1. 85-90% silica sand (SiO2)

2. 3-7% bonding material e.g., clay cereal etc.3. 3-6% waterRequirements of molding sand are:(a) Refractoriness(b) Cohesiveness(c) Permeability(d) Collapsibility

The cavity in the sand mold is formed by packing sand around a pattern, then separating the mold into two halves and removing the pattern

Moulding

Melting

• Furnaces most commonly used in foundries: − Cupolas

− Direct fuel-fired furnaces

− Crucible furnaces

− Electric-arc furnaces

− Induction furnaces

Pouring the Molten Metal

For this step to be successful, metal must flow into all regions of the mold, most importantly the main cavity, before solidifying

Factors that determine success: Pouring temperature Pouring rate Turbulence

Sections of foundry

Metal

Melting

Handling molten metal

Sand

Sand mixing & preparation

Moulding

Pouring

Shaking out

Finishing

Heat treatment

Inspection & Testing

Melting Section Moulding Section

Sand additives

General layout of foundry

Foundry store

Melting

Sand

Moulds ready for pouring

Furnaces

Inspection Bench Core making

Grinding

Muller

Preparation of sand mould

Before any casting can take place a wooden pattern is made precisely. This is called pattern making and in industry this is a very skilful job. Any inaccuracy at this stage will result in the final cast being wrong or even failing.

Drag is placed inverted on the mould floor and pattern is placed at the center of the box

SAND CASTING

Special casting sand will soon be packed around the pattern for easy removal of pattern from

parting powder is sprinkled over and around it. It stops the casting sand sticking to the pattern and pulling away with it when the pattern is finally removed from the sand.

Casting sand is then shaken through a sieve (called riddled sand) so that only fine particles fall around the pattern. This is called facing sand and it must be fine so that detail on the pattern shows up on the final casting.


The drag is then packed with more casting sand and then ram it down firmly using a ramming tool. The tool has two ends, one is cylindrical and is used for general packing down of the sand. The other end is quite pointed and this can be used for packing sand close up to the pattern.

When the drag is packed fully it is levelled off (called ‘strickled off’) using a straight steel bar.


The entire drag and its contents are then turned over so that the base of the pattern can be seen

A top box called a ‘cope’ is then placed on top of the drag and locating pins are put in position so that the casting boxes cannot move sideways.


Sprue pins are positioned. One usually on the back of the pattern and the other to the side. These will eventually provide an entrance and exit for the molten aluminium when it is poured into the sand.

The sand is packed/rammed into the cope in the same

way as the drag.


The top box (the cope) is then removed and if all is well the cope with the sand inside should lift off the drag (bottom box) without the sand falling out. A small ‘gate’ is cut below the position of one of the sprue pins. This will help the molten metal to flow into the cavity left by the mould. Small tools are available or can easily be made to dig a variety of shapes in the casting sand. They are similar to small trowels


The pattern is removed using a ‘spike’. Before removing the pattern it is a good idea to gently tap the spike so that it loosens the pattern from the sand. It can then be lifted away from the casting box (drag). The cope (top casting box) is placed back on top

of the drag and the locating pins put in position. Before this is done vents can be created using a thin piece of welding rod, pushing it through the sand . This allows gases to escape once the molten metal is poured.


The molten metal is poured with great care. The molten metal is poured down the hole left by the first sprue pin (now called the ‘runner’). As it runs down the runner it flows through the ‘gate’ cut by the trowel, into the cavity left by the pattern and up the riser (the hole left by the second sprue pin).

The casting should be left for at least an hour before removal from the sand

When removed from the sand, the runner and riser are cut away and the casting is ready for machining


Sand Testing

Sand testing

Each foundry should draw out a minimum test programme which should be strictly followed for control of the sand system

Controlling quality of sand in a foundry is very important as the quality of the casting depends on the quality of the mould sand

The quality of the mould and core depends on the sand, binder, additives used & also on the percentage of each of the constituents

Sand testing provides clues for improving casting quality Since molding sands and core sands are important in foundry

operations, their control and testing is essential Sand control tests are performed on the sand which has been

prepared and is ready to be transferred to the moulding section

Testing of mould & core sand

1)Preparation of standard test specimen 2)Mould hardness test 3)Core hardness test 4)Moisture content test on foundry sand 5)Sieve analysis 6)Clay content test 7)Permeability test 8)Compression, shear test

1)Preparation of standard test specimen

The standard specimen is prepared using a standard sand rammer and specimen tube accessories.The specimen is rammed with three blows. The weight of the ram may be 63-72 N by

weight. The ram is dropped from a height of 50mm . The specimen is rammed with three blows- This is the standard procedure.

This operation that is ramming sand three times compacts the sand to a standard hardness

2)Mould hardness test

Mold surface hardness is the resistance offered by the surface of a green sand mold

An instrument for determining the mold surface hardness shall measure the depth of penetration in to the mold surface of a plunger having a load applied at a 90º angle

to the mold surface 3)Core hardness testCore hardness is the resistance offered by the surface of a dry sand core

4)Moisture content test on foundry sand In clay bonded sand some moisture is essential to

develop working strength. The influence of moisture may be harmful if the

proportion is not controlled within the definite limits.

The strength of a sand is also influenced by its moisture content.

It is therefore important to make certain that the sand contains the correct percentage of water

Two methods i) simply by measuring the weight difference between the green sand and the dry sand, then calculating percentage of moisture = (W1-W2)/W1X100

ii) chemical method: by speedy moisture teller water + calcium carbide= acetylene

gas=pressure=pointer

5)Sieve analysis

The grain size is expressed by number known as grain fineness number.

For determination of grain fineness number of a given sand sample, a standard sieve set is used.

The apparatus consists of eleven sieves mounted one above the other.

The shaker vibrates the sieve by motor arrangement. So the sand placed at the top sieve gets screened and get collected on different sieves of different sizes depending up on the size of the grain.

The sieve system is vibrated for some specific period.

6)Clay content test

The necessary bonding strength for mouliding sand is clay, so that after ramming the mould doesn’t loose its shape.

However as the quantity of the clay is increased, the permeability of the sand decreases.

Clay is responsible for bonding the sand particles together.

It influences strength permeability and other moulding sand properties.

Known quantity moulding sand is taken and washed with water and NaOH. Then dried and reweighed

The weight of clay is given by the difference between the original weight and weight after washing

7)Permeability test Gases and water vapour are released in the mould

cavity by the molten metal and sand. If they do not find opportunity to escape completely

through the mould, they will get entrapped and form gas holes or pores in the casting

The sand must therefore be sufficiently porous to allow the gases and water vapour to escape out.

This property of sand is referred to as permeability. The apparatus has an arrangement which allows

controlled amount of air to pass through a sand sample and the time taken for all the air to pass through the same is measured

Permeability no = VH/PAT V= volume of air, H=height, P=pre

A=area of specimen, T= Time

8)Compression, shear test Strength tests have been devised to test the

holding power of various bonding materials in green and dry sand

The strength is governed by the amount of bonding materials

The universal sand strength testing machine is used to test the strength of sand

Compressive strength, shear strength, tensile stregth of the moulding sand is done on this universal sand strength machine by replacing the different grippers

Test machine gives direct reading

G G

Hand tools used in moulding

In hand moulding processes, all the moulding operations, such as ramming the sand, placing and drawing the pattern, turning over the moulding boxes, etc, are performed by hand

A number of hand tools which are used by the molder to perform above mentioned operations are shown below

1)Bellow : A bellow is used to blow loose sand particles from the pattern and the mold cavity


2) Lifter or cleaner: It lifts dirt or loose sand from the mold. It is used for repairing and finishing the sand mold cavity

3)Heart & square: It is employed for finishing the mould cavity

4)Hand rammer:It is used for ramming the sand in molds


5)Floor rammer: It is larger in size as compared to hand rammer. It is used for floor molding

6)Hand riddle:It consists of wire mesh fitted into a circular wooden frame. It is used for cleaning, removing foreign matter from sand

7)Sprue pin: It is tapered wooden rod which is placed in the

cope to make sprue cavity.


8) Trowels: used to finish flat surfaces of the mould,

cut ingates, make joints or repair moulds

9)Smoothers and corner slics:They are employed to repair and finish corners, edges, round and flat surfaces


9)Gate cutter: it is a shaped piece of sheet metal . It is used to cut the gate

10)Shovel : used to transfer moulding sand from store to place of use. Also used to mix and temper the moulding sand

Thank u

Documents

Foundry Lab