SIR PADAMPAT SINGHANIA UNIVERSITY

Lab Manual

Of

Manufacturing Technology Lab (ME317)

Lab Instructor:

Naveen Kumar

REGULATIONS FOR THE LABORATORY

1. STUDENTS MUST DRESS PROPERLY (WEAR A LONG WORKSHOP SUIT, SHOES PREFERABLY SAFETY SHOES, SOCKS, SAFETY GLASSES WHEN APPROPRIATE).

2. STUDENTS MUST COME TO IE WORKSHOP AT THE FACULTY OF ENGINEERING BUILDING ON TIME. LATE COMING RESULTS IN A PENALTY OF 10% OF FULL MARKS. IF THE LATENESS IS MORE THAN 15 MINUTES, THE STUDENTS WILL NOT BE ALLOWED TO PRACTICE IN THAT LABORATORY-SESSION, AND THE MARK FOR THAT SESSION WILL BE ZERO.

3. THERE IS NO MAKE-UP FOR THE LABORATORY SESSION. STUDENTS WHO MISS ANY SESSION WILL GET ZERO MARK FOR THE SESSION.

4. THERE IS NO EXTENSION OF THE LABORATORY TIME. STUDENTS SHOULD TRY TO FINISH THE ASSIGNMENT WITHIN THE REGULAR LABORATORY TIME. AT THE END OF THE SESSION, THE WORK-PIECE MUST BE SUBMITTED REGARDLESS OF ITS COMPLETENESS. THE MARKS WILL BE GIVEN BASED ON THE QUALITY OF THE WORK-PIECE.

5. STUDENTS MUST OBEY ALL INSTRUCTIONS FROM INSTRUCTORS. STUDENTS MUST NOT TRY ANYTHING THAT IS CONSEQUENCE IS NOT CLEARLY KNOWN. BEFORE TRYING ANYTHING, ASK THE INSTRUCTOR FIRST.

6. STUDENTS MUST AVOID ANY UNSAFE ACT, E.G., RUNNING, PLAYING, MISUSE OF THE TOOLS, PRESSING AN UNKNOWN BUTTON, AND OPERATING AN UNKNOWN SWITCH OR LEVER.

7. STUDENTS MUST USE PROTECTION EQUIPMENT SUPPLIED BY THE INSTRUCTOR.

8. FAIL TO COMPLY WITH THE INSTRUCTIONS, SAFETY RULES, AND COMMON SENSE, MAY RESULT IN A SEVERE INJURY.

List of Experiments

S.N. Name Of Experiments Page No.

1. Study of Various types of raw and Prepared Sand

2. To find out the grain fineness number of the given sand sample

3. To Calculate the permeability of the sand sample

4. To find out the moisture content of the sand sample

5. Study of gas welding and different types of flames

6. A Job using gas welding

Experiment-1

1. Objective:- Study of Various types of raw and Prepared Sand.

2. Theory:-

Following are the important properties of molding sand

Refractoriness

It is the ability of the molding material to resist the temperature of the liquid metal to be poured so that it does not get fused with the metal. The refractoriness of the silica sand is highest.

Permeability

During pouring and subsequent solidification of a casting, a large amount of gases and steam is generated. These gases are those that have been absorbed by the metal during melting, air absorbed from the atmosphere and the steam generated by the molding and core sand. If these gases are not allowed to escape from the mold, they would be entrapped inside the casting and cause casting defects. To overcome this problem the molding material must be porous. Proper venting of the mold also helps in escaping the gases that are generated inside the mold cavity.

Green Strength

The molding sand that contains moisture is termed as green sand. The green sand particles must have the ability to cling to each other to impart sufficient strength to the mold. The green sand must have enough strength so that the constructed mold retains its shape.

Dry Strength

When the molten metal is poured in the mold, the sand around the mold cavity is quickly converted into dry sand as the moisture in the sand evaporates due to the heat of the molten metal. At this stage the molding sand must posses the sufficient strength to retain the exact shape of the mold cavity and at the same time it must be able to withstand the metallostatic pressure of the liquid material.

Hot Strength

As soon as the moisture is eliminated, the sand would reach at a high temperature when the metal in the mold is still in liquid state. The strength of the sand that is required to hold the shape of the cavity is called hot strength.

Collapsibility

The molding sand should also have collapsibility so that during the contraction of the solidified casting it does not provide any resistance, which may result in cracks in the castings.Besides these specific properties the molding material should be cheap, reusable and should have good thermal conductivity.

Molding sands may be classified, according to their use as under:

1) Green sand: - When sand is in its natural (more or less moist) state, it is referred to as green sand. It is a mixture of silica sand, with 18 to 30% clay and 6 to 8% water. The clay and water give bonding strength to green sand. It is fine soft, light and porous. Being damp, it retains the shape given to it under pressure during squeezing. As the mould becomes dense by ramming, the structure is made porous by venting. Sharp edges are avoided in green sand moulding, because these being weak, break when hot is poured. Green sand is generally used for casting small or medium sized moulds. Larger output can be obtained from a given floor space as the cost and delay involved in drying the moulds is saved. Coal dust is mixed in Green sand to prevent defects in castings.

2) Dry sand: - Dry sand molding is employed for large casting. The moulds prepared in green sand are dried or baked to remove, almost, all moisture of the moist sand. The structure in the molding boxes after drying becomes stronger and compact. Venting is therefore necessary but not to that extent, as in the case of Green sand mould. For larger heavy moulds, cow dung, horse manure, etc. are mixed with the sand of coarser grains.

3) Loam sand: - It is a mixture of clay and sand milled with water to a thin plastic paste, from which moulds are built up on a backing of soft bricks. Loam sand contains up to 50% clay and dries hard. It also contains fire clay. It must sufficiently adhesive to hold on to the vertical surfaces of the rough structure of the mould. Chopped stray and manure are commonly used to assist in binding. The moisture content is from 18 to 20%.

Loam is dried very slowly and completely before it is ready for casting. It is used for casting larger regular shaped casting like chemical pans, drums, etc.

4) Facing sand:- It is used directly next to the surface of the pattern and it comes into contact with the molten metal. Since, it is subjected to the most severe conditions; it must possess high strength and refractoriness. It is made of silica sand clay without the addition of used sand. Different forms of carbon known as facing materials. (e. g, plumbago powder, ceylon lead or graphite) are used to prevent the mealy form burning in to the sand. Sometimes they are mixed with 6to 15 times fine moulding sand to make mould facings.Facing sand layer in a mould, usually ranges from 20 to 30mm. Facing sand comprises 10 to 15% of the whole amount of mould sand.

5) Backing sand:- The old repeatedly used moulding sand ,black in colour due addition of coal dust and burning or coming in contact with molten metal is known as backing sand or floor sand or black sand. It is used to fill in the mould at the back of facing layer. It is weak in bonding strength because the sharp edges of sand grain become rounded due to high temperature of molten metal and burning of clay content.

6) System sand:- This used in machine moulding to fill the whole flask. Its strength, permeability, and refractoriness must be higher than those backing sand.

7) Parting sand:- The moulding boxes are separated from adhering to each other by spreading a fine sharp dry sand called 'parting sand’. Parting sand is also used to keep the green sand from sticking to the pattern. It is clean clay free silica sand. Burnt core sand could also be used for this purpose.

8) Core sand:- It is used for making cores . It is silica sand mixed with Core oil (linseed oil rosin, light mineral oil and other binders). For the sake of economy pitch or flour and water may be used as core sand for large Cores.

Various specialized sand used for making moulds are described below:

9) CO₂-sand:- In CO₂-sand, the silica grains, instead of being coated with natural clay, are coated with sodium silicate. This mixture is first packed around the pattern and then hardened by passing CO₂ through the interstices for about a minute. The sand thus sets hard and produces a strong mould.

10) Shell sand:- Shell sand are synthetic sands coated with phenol or urea-formaldehyde resins and cured against a hated pattern to produce very strong, thin shell . No back up sand is required to provide support for the weight of the casting. Since, alloys solidify at high temperatures, the resins are not dissociated. But moulds disintegrate when casting has solidified due to breaking up of chemical bond by heat from solidifying casting.

11)Facing sands:- Usually, Facing sands is first applied on the pattern, so that only it, comes in contact with the molten metal. This sand is refractory enough so as not get fused and burnt on coming in contact with the metal.

12)Backing sands:- These are applied as back up mechanical support to facing sand. These are permeable to allow gases to escape.

13)Mould washes: - These are slurries of fine ceramic grains. These are applied over the mould surfaces to minimize fusing of the facing sand grains. These also produce smoother surface on casting due to filling up of the interstices.

Following are the ingredients in the molding sand:

Base sand, Binder, and

Moisture

Base Sand

Silica sand is most commonly used base sand. Other base sands that are also used for making mold are zircon sand, Chromite sand, and olivine sand. Silica sand is cheapest among all types of base sand and it is easily available.

Binder

Binders are of many types such as:

1. Clay binders, 2. Organic binders and

3. Inorganic binders

Clay binders are most commonly used binding agents mixed with the molding sands to provide the strength. The most popular clay types are:

Kaolinite or fire clay (Al2O3 2 SiO2 2 H2O) and Bentonite (Al2O3 4 SiO2 nH2O)

Of the two the Bentonite can absorb more water which increases its bonding power.

Moisture

Clay acquires its bonding action only in the presence of the required amount of moisture. When water is added to clay, it penetrates the mixture and forms a microfilm, which coats the surface of each flake of the clay. The amount of water used should be properly controlled. This is because a part of the water, which coats the surface of the clay flakes, helps in bonding, while the remainder helps in improving the plasticity. A typical composition of molding sand is given in

Experiment -2

Objective: - To Determine the Grain fineness number of the given sand sample.

Equipment’s required:- Standard Mesh’s, Trowel etc.

Theory:-

Grain fineness test: - Granular Particles of various sizes and shapes provide variable interstices [space between grains] and hence, are directly responsible for permeability and compactness of the sand. Granular particles have higher strength but lower permeability, whereas round grains have high permeability and lower strength.

To carry out this test, a sample of dry sand weighing 50 grams, free from clay is placed on the topmost sieve bearing U.S. series equivalent number 6 A set of standard testing sieves having U.S. Bureau of standard meshes 6,12,20,30,40,50,70,100,200,and 270 are mounted on a mechanical shaker. The above sample is shaked for about 15 minutes. After this, weight of the sand retained on each sieve can be obtained.

Proposed method & Calculation

To obtain the grain –fineness, weight of the sand retained by each sieve is multiplied by 2, which gives the percentage of weight retained by each sieve. This percentage is again multiplied by a multiplying factor given in the example solved below;

The A.F.S. (American foundry Men’s society) grain fineness number will be,

Total product = Total sum of percentages of Sand retained by different sieves

Calculation for AFS grain Fineness number

Sieve numberSieve Size(Microns )

Sand retained

Multi-Plier

Product(4)*(5)Weight % wt. retained

Calculation:-

Total product Grain fineness number = % of Sand retained

Results:-

AFS-Grain fineness number of the given material =____________

Experiment -3

Objective:-To Determine the Permeability number of the given material

Equipment’s required:- Permeability meter, etc

Theory: Permeability is a condition of porosity and thus is related to the passage of gaseous materials through the sand. It is expressed as the volume of air in cubic centimeters that will pass per minute under a pressure of 10kg/m2 through a specimen of sand 1 square centimeter of cross- sectional area and one centimeter in height.

There are four conditions for permeability.

(a) Base permeability is the permeability measured in a specimen of packed dry sharp sand.

(b) Green permeability is the permeability measured in a specimen made of moist moulding sand.

(c) Dry permeability is the permeability measured in a specimen made of moulding sand and dried at about 100 to 110®C.

(d) Baked permeability is the permeability measured in a specimen made of sand with thermo- setting binder and backed at some temperature above 105®C.

Foundry Sand Grading Classification

Grain Clay Content

Grain Class Fineness Zone Clay Class Clay Zone

1 200to and including 300 A 0.0 to and including 0.5

2 140 to but not including 200 B 0.5to and including 2.0

3 100 to but not including 140 C 2.0 to and including 5.0

4 70 to but not including 100 D 5.0 to and including 10.0

5 50 to but not including 70 E 10.0 to and including 15.0

6 40 to but not including 50 F 15.0 to and including 20.0

7 30 to but not including 40 G 20.0 to and including 30.0

8 20 to but not including 30 H 30.0to and including 45.0

9 15 to but not including 20

10 10 to but not including 15

Procedure of Permeability test:-

Permeability test is carried out by using a permeability meter consisting of an aluminum casting in the form of a water tank and a base. A balanced tank floats inside the water tank. A specimen tube extends down to the specimen and opens into the air space. The sand specimen is placed at the base and is sealed with mercury. Lowering of the floating tank makes air to pass through the sand specimen. Air is passed through a nozzle to adjust the flow rate. For fine sand, flow rate should be slow.

Permeability test is conducted with the specimen usually of 20.26 cm2 cross-sectional and 5.08cm height, placed in the instrument cup, which provides a mercury seal, and a predetermined amount of air is forced through the specimen under controlled conditions.

The Permeability reading is taken by noting the time in which 2000 c.c of air passed through the specimen at constant pressure. Then Permeability number is obtained by dividing 3007.2 by the time in seconds. This Permeability number is a relative number. It does not necessarily tell the Permeability of a mould made with the same sand, which depends on the compactness of the sand. The unit can be made direct reading, if an electric timer unit and a direct reading dial are provided.

Calculation:-

The Permeability number P can be found mathematically, by the formula given below:

v.h. P = p.a.tP = Permeability number to be determined.

V = volume of air passing through the specimen in cm3.

h = height of the specimen in cm.

p = pressure of air in gm. /cm2

A = cross- sectional area of specimen in cm2 (A standard value of 20.26 cm2 is generally -

adopted ).T = time for air to pass in minutes.

Results:-

Permeability number of the given material =________________

Experiment -4

1. Objective:-To Determine the moisture content in the given sand sample.

2. Equipments and Materials: Electronic Balance, Oven with temperature 120

degree.

3. Procedure:-

a) Take the 150 gram sample of the sand.

b) Mix the water till it becomes in the paste form

c) Make it in the cylindrical shape.

d) Weight it

e) Put the sample in the oven for 10 minutes at 110 degree temperature

f) Take the sample out of the oven

g) Weight it again

h) The difference is the amount of moisture.

4. Obeservations:-

a) Initial weight of the sand sample with water= gm

b) Final weight of the sand sample after drying= gm

5. Calculations:-

The moisture content= Initial weight (gm)- Final weight(gm)

% Moisture content = Initial weight (gm)- Final weight(gm)/ Initial weight (gm)

6. Results:

The moisture content is---------------gm

Experiment-5

1. Objective:- To study gas welding process and various flames.

2. Theory:-

There are two types of welding process:

• Plastic Welding or Pressure Welding :The piece of metal to be joined are heated to a plastic state and forced together by external pressure(Ex) Resistance welding

• Fusion Welding or Non-Pressure Welding: The material at the joint is heated to a molten state and allowed to solidify (Ex) Gas welding, Arc welding.

Other broad classifications of welding processes is based on the type of heat generation and method of joining is as follow

(i). Arc welding

a) Carbon arc (b)Metal arc (c)Metal inert gas (d)Tungsten inert gas (e)Plasma arc

f)Submerged arc (g)Electro-slag

(ii). Gas Welding

a) Oxy-acetylene (b) Air-acetylene (c) Oxy-hydrogen

(iii). Resistance Welding

a) Butt (b)Spot (c)Seam (d)Projection (e)Percussion

(iv)Thermit Welding

(v)Solid State Welding

a)Friction (b)Ultrasonic (c)Diffusion (d)Explosive

(vi)Newer Welding

a)Electron-beam (b)Laser

(vii)Related Process

a)Oxy-acetylene cutting (b) Arc cutting (c)Hard facing (d)Brazing (e)Soldering

Gas Welding:

• Sound weld is obtained by selecting proper size of flame, filler material and method of moving torch

• The temperature generated during the process is 33000c

• When the metal is fused, oxygen from the atmosphere and the torch combines with molten metal and forms oxides, results defective weld

• Fluxes are added to the welded metal to remove oxides

• Common fluxes used are made of sodium, potassium. Lithium and borax.

• Flux can be applied as paste, powder,liquid.solid coating or gas.

Gas Welding Equipments:

Gas Cylinders

Pressure

Oxygen – 125 kg/cm2

Acetylene – 16 kg/cm2

2. Regulators

Working pressure of oxygen 1 kg/cm2

Working pressure of acetylene 0.15 kg/cm2

Working pressure varies depends upon the thickness of the work pieces welded.

3. Pressure Gauges

4. Hoses

5. Welding torch

6. Check valve

7. Non return valve

Types of Flames:

• Oxygen is turned on, flame immediately changes into a long white inner area (Feather) surrounded by a transparent blue envelope is called Carburizing flame (30000c)

• Addition of little more oxygen give a bright whitish cone surrounded by the transparent blue envelope is called Neutral flame (It has a balance of fuel gas and oxygen) (32000c)

• Used for welding steels, aluminium, copper and cast iron

• If more oxygen is added, the cone becomes darker and more pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame

• Has the highest temperature about 34000c

• Used for welding brass and brazing operation

Experiment-6

1.Objective:- To prepare a butt joint using gas welding.

2.Material and Equipments:-

Two mild steel pieces of given sizes, welding set, filler rod,flux,lighter, chipping hammer, wire brush, safety goggles, Gloves and files.

3.Procedure:-

a) The edges are properly cleaned and v-groove is prepared.

b) The workpieces are placed properly on the table.

c) Open the valves of the oxygen and acetylene cylinders

d) Light up the tip of the torch

e) Adjust the torch valve so that the flame is neutral

f) Using leftward technique, the welding rod and torch are moved along the desired line of the weld till the weld is complete.

4. Results:-

The welding of the two pieces is completed

5. Precautions:-

a) Use welding goggles while welding

b) Remove all flammable items from the vicinity of the cylinders

c) While lighting torch, the valve of oxygen cylinder is opened first