casting, welding and metal forming lab

LAB MANUAL PRACTICAL

AKSUM UNIVERSITYCOLLEGE OF ENGINEERING AND TECHNOLOGYDEPARTMENT OF MECHANICAL ENGINEERING

CASTING, WELDING and METAL FORMING LAB MANUAL

LIST OF EXPERIMENTS

CHAPTER 1: WELDING1. Study of Arc Welding Tool s2. Arc Welding (Lap joint)3. Gas Welding (Butt joint)4. Spot Welding (Lap joint)5. TIG Welding (Butt joint)

CHAPTER 2: Metal Forming:6. Press Working of Sheet metal7. Study of Different Types of Dies.

CHAPTER 3 : CASTING8. Study of Moulding Equipments9. Study of Patterns10.Mould Making using Split Pattern.

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1. STUDY OF ARC WELDING TOOLS

AIM: To study the different types of arc welding tools

APPARATUS REQUIRED: Welding table, Arc welding power source, electrode holder, welding electrode and hand screen etc.

PROCEDURE:

i. Arc welding power source: For AC welding supply, transformers are predominantly used for almost all arc welding where mains electricity supply is available. They have to step down the usual supply voltage (200- 400 volts) to the normal open circuit welding voltage (50-90 volts).

ii. Electrode holder: Electrode holder is used for holding the electrode manually and conducting current to it. These are usually matched to the size of the lead, which in turn matched to the amperage output of the arc welder. Electrode holders are available in sizes that range from 150 to 500 Amps.

iii. Welding Electrodes An electrode is a piece of wire or a rod of a metal or alloy, with or without coatings. An arc is set up between electrode and work piece. Welding electrodes are classified into following types-

(1) Consumable Electrodes (a) Bare Electrodes (b) Coated Electrodes (2) Non-consumable Electrodes (a) Carbon or Graphite Electrodes

(b) Tungsten ElectrodesConsumable electrode is made of different metals and their alloys. The end

of this electrode starts melting when arc is struck between the electrode and work piece. Thus consumable electrode itself acts as a filler metal. Bare electrodes consist of a metal or alloy wire without any flux coating on them. Coated electrodes have flux coating which starts melting as soon as an electric arc is struck. This coating on melting performs many functions like prevention of joint from atmospheric contamination, arc stabilizers etc.Non-consumable electrodes are made up of high melting point materials like carbon, pure tungsten or alloy tungsten etc. These electrodes do not melt away during welding. But practically, the electrode length goes on decreasing with the passage of time, because of oxidation and vaporization of the electrode material during welding. The materials of non consumable electrodes are usually copper coated carbon or graphite, pure tungsten, thoriated or zirconiated tungsten.

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iv. Hand Screen: Hand screen used for protection of eyes and supervision of weld bead.

v. Chipping Hammer: It is used to remove the slag by striking.vi. Wire brush: It is used to clean the surface to be weld.

vii. Protective clothing: Operator wears the protective clothing such as apron to keep away the exposure of direct heat to the body.

viii. Welding Table: It is used to hold the welding equipments and welding materials in welding process.

RESULT: Thus the given different types of equipments are studied.

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2. ARC WELDING (LAP JOINT)AIM: Prepare the lap joint using arc welding.

APPARATUS REQUIRED: Arc welding setup, chipping hammer, protective glass and welding table.

PROCEDURE: 1. Place the two work piece on the required position.2. First run of welding is done to fill the gap and penetration of the weld ment by

holding the electrode at about 700 and moving the electrode to another end uniformly.

3. Second run of welding is done with proper weaving and uniform movement.4. The scale formed is chipped with chipping hammer.

RESULT: Thus the given lap joint is performed using arc welding.

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3. GAS WELDING (BUTT JOINT)

AIM: Prepare the butt joint using gas welding.

APPARATUS REQUIRED: Gas welding setup, cloves, protective cloth, hammer, wire brush and welding table.

PROCEDURE: 1. Acetylene valve on the torch is opened slightly and lightened with the help of a spark lighter. 2. Now acetylene valve is opened to get required the flow of acetylene. 3. Oxygen valve is opened till the intermediate flame feather reduces into inner cone to get a neutral flame. 4. The torch tip is to be positioned above the plates so that white cone is at a distance of 1.5mm to 3mm from the plates. 5. Torch is to be held at an angle of 300 to 450 to the horizontal plane. 32 6. Now filler rod is to be held at a distance of 10mm from the flame and 1.5 mm to 3 mm from the surface of the weld pool. 7. As the backward welding allows better penetration, back ward welding is to be used. 8. After the completion of welding, slag is to be removed by means of chipping

hammer, wire brush.

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RESULT: Thus the given butt joint is performed using gas welding.

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4. SPOT WELDING ( LAP JOINT)

AIM: To prepare a lap joint on the given work piece using spot welding equipment.

APPARATUS REQUIRED: Spot welding equipment, snip and cloves.

PROCEDURE: 1. Switch on the machine and set the current in the machine to 2 Ampere 2. Set the timer to two seconds 3. Overlap the two metal pieces to the requires size and place them between the two electrodes.4. Apply pressure by foot on the lever such that two electrodes come into contact if the over lapped metals.

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5. After 2 seconds remove the pressure on the lever slowly. 6. Now the joint is ready for use.

RESULT: Effect of current on strength of spot weld is studied.

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Spot Welding

5. TIG WELDING (BUTT JOINT)

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AIM: To prepare a Butt Joint Using TIG Welding

APPARATUS REQUIRED: TIG (Tungsten Inert Gas) welding transformer, and Argon gas cylinder.

PROCEDURE:

1. Place the work pieces on the work table in the required position.2. Set the current of the machine to 100 A.3. Fix the tungsten electrode to the electrode holder.4. Required size of the nozzle is selected and it is fixed to the torch.5. Adjust the inert gas flow rate to the required rate.6. Select the filler rod (same as base metals) of required diameter.7. Touch the electrode to the work, so that current flow will be established and

then separated by a small distance and the arc will be generated.8. First tack weld is done on the work pieces.9. Move the electrode slowly along the length of the joint with the filler rod, so

that the filler metal will be deposited in the joint.10.Repeat the operation for the second pass, so that required amount of filler

metal will be deposited on the work pieces.

RESULT: Thus the given metal plate was welded using TIG welding machine.

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TIG Welding

6. PRESS WORKING OF SHEET METALL


AIM: To do the different types of press working operations in the piece of given sheet metal.

APPARATUS REQUIRED: Press working machine like shearing machine, sheet bending machine, punching machine etc.

PROCEDURE: Different types of press working operations are described below.

1. Blanking: Blanking is the operation of cutting a flat plate from sheet metal. The article punched out is called the „blank‟ and is the required product of the operation. The hole and metal left behind is discarded as waste. It is usually the first step of series of operations.

2. Punching (or Piercing): It is a cutting operation by which various shaped holes are made in sheet metal .Punching is similar to blanking except that in punching, the hole is the desired product, the material punched out to form the hole being waste.

3. Perforating: This is a process by which multiple holes which are very small and close together are cut in flat work material.

4. Trimming: This operation consists of cutting unwanted excess material from the periphery of a previously formed component.

5. Shaving: The edges of a blanked part are generally rough, uneven and unsquare. Accurate dimensions of the part are obtained by removing a thin strip of metal along the edges.

6. Slitting: It refers to shearing operation using circular blade. These blades follow straight line or circular path or curved path depending upon the requirement.

7. Lancing: This is a cutting operation in which a hole is partially cut and then one side is bent down to form a sort of tab or louver. Since no metal is actually removed, there will be no scrap.

8. Bending: In this operation, the material in the form of flat sheet or strip is uniformly strained around a linear axis which lies in the neutral plane and perpendicular to the lengthwise direction of the sheet metal.

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9. Drawing: This is a process of a forming a flat work piece into a hollow shape by means of a punch which causes the blank to flow into a die cavity.

RESULT: Thus the different types of press working operations are done in the given sheet metal using the different types of machinces.

Trimming

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7. STUDY OF DIFFERENT TYPES OF DIES.O


AIM: To study the different types of press tools and dies.

APPARATUS REQUIRED: Different types of press tools and dies and metal plates.

PROCEDURE: The dies may be classified according to the type of press operation and according to the method of operation.A. Types of press operation: According to this criterion, the dies may be classified as: cutting dies and forming dies.

i. Cutting dies: The dies are used to cut the metal. They utilize the cutting or shearing action. The common cutting dies are: blanking dies, piercing dies, perforating dies, notching, trimming, shaving dies etc.

ii. Forming dies: These dies change the appearance of the blank without removing any stock. These dies include bending dies, drawing dies, squeezing dies etc..

B. Method of operation: According to this criterion, the dies may be classified as: single operation dies or simple dies, compound dies, combination dies, transfer dies, progressive dies and multiple dies.

i. Simple die: Simple die or single action dies perform single operation for each stroke of the press. The operation may be one of the operation listed under cutting or forming dies.

ii. Compound die: One machine (or station) will have more than one die. But in one stroke, more than one cutting operation is performed it is called compound die. Figure show a compound die in which stainless steel washer is made by one stroke of the press. The washer is produced by the combined application of blanking and piercing operation.

iii. Combination die: One machine (or station) will have more than one die. But in one stroke a combination of cutting and forming operation is performed is called combination die. Figure show a stainless steel cup is made by one stroke of press. This cup is produced by the combined application of blanking and drawing operation.

iv. Progressive die or Follow on die: One machine will have more than one die. It is constructed with either only cutting dies or combination of both cutting dies and forming dies. But one stroke only one operation is performed, the next operation is performed in the next stroke of the same machine, like that the operations are continued upto finishing of work piece. For example in figure shows stainless steel washer is produced, for the first stroke hole is

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punched using punching operation and then the required washer will cut using blanking operation. So punching and blanking operation was done by separate two strokes and then we are able to get the washer.

RESULT: Thus the different types of dies were studied.

Simple die

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8. STUDY OF FOUNDRY TOOLS & EQUIPMENTS

AIM: To study the different types of foundry tools and equipments.

APPARATUS REQUIRED: Moulding equipments like moulding box, moulding board, shovel, sprue pin etc.

PROCEDURE: Different moulding equipments are described below.

1. Rammers: These are required for striking the molding sand mass in the molding box to pack or compact it uniformly all around the pattern.2. Strike of bar: It is used to strike off or remove the excess sand from the top of a molding box after completion of ramming thereby making its surface plane and smooth.3. Draw of Spike: It is used for driven into pattern which is embedded in the molding sand and raps the pattern to get separated from the pattern and finally draws out it from the mold cavity.4. Vent rod: After ramming and striking off the excess sand it is utilized to pierce series of small holes in the molding sand in the cope portion. The series of pierced small holes are called vents holes which allow the exit or escape of steam and gases during pouring mold and solidifying of the molten metal for getting a sound casting.5. Hand Riddle: It is generally used for cleaning the sand for removing foreign material such as nails, shot metal, splinters of wood etc. from it.6. Shovel: It is used in mixing, tempering and conditioning the foundry sand by hand. It is also used for moving and transforming the molding sand to the container and molding box or flask.7. Gate cutter: is a small shaped piece of sheet metal commonly used to cut runners and feeding gates for connecting sprue hole with the mold cavity.8. Molding box: It is wooden or cast iron box made rectangular or square shape used for sand molding to make the mold.9. Sprue pin: It is a tapered rod of wood or iron which is placed or pushed in cope to join mold cavity while the molding sand in the cope is being rammed. Later its withdrawal from cope produce a vertical hole in molding sand, called sprue through which the molten metal is poured into the mould using gating system. It helps to make a passage for pouring molten metal in mold through gating system.

RESULT: Thus the different types of foundry equipments are studied.

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Hand Riddle Shovel Rammers Sprue pin

Strike off bar Gate cutter Draw of spike

Draw of spike Moulding box

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9. STUDY OF PATTERNS

AIM: To study the different types of given solid patterns.

APPARATUS REQUIRED: Patterns like solid, split and match plate and gated pattern.

PROCEDURE: A. Different types of patterns: (i) Solid Pattern (ii) Split pattern (iii) Gated pattern

(iv) Match plate pattern (v) Loose piece pattern.

1. Solid or single piece pattern: Such patterns are made in one piece and are suitable only for very simple castings. There is no provision for runners and risers etc. Moulding can be done either in the foundry floor (called pit moulding) or in a moulding box. There is no difficulty in withdrawing the pattern from the mould as the broadest portion of the pattern is at the top. As an example, if a cylindrical pin with a circular head has to be cast, a one piece pattern shown in Fig 1. will be adequate.2. Split pattern: A pattern is made by two separate pieces it is called split pattern. Two halves of patterns are assembled to gather with use of dowel pins. In both solid and split pattern tapered or threaded holes are provided these holes are used to lift the pattern from the moulding sand using draw spike.3. Match plate pattern: Match plate is a metal plate, usually made of aluminium. The two halves of the split pattern are mounted on this match plate one on either side. While fixing them to the match plate, care is taken so that there is no mismatch. These patterns are used in conjunction with mechanically operated moulding machines. 4. Gated pattern: A patterns where provision for gating has been made are called gated patterns. It removes the necessity of making a gate separately.5. Loose piece pattern: In some cases, the casting may have small projections or overhanging portions. These projections make it difficult to withdraw the pattern from the mould. Therefore these projections are made as loose pieces. They are loosely attached to the main part of the pattern and the mould is made in the usual way.

B. Core and Core print:

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1. Core: Whenever a hole, recess, undercut or internal cavity is required in a casting, a core, which is usually made up of a refractory material like sand is inserted at the required location in the mould cavity before finally closing the mould.

2. Core print: Core prints are special extensions in the pattern used to produce a necessary support for core in the mould.

RESULT: Thus the different types of patterns with core are studied.

Core print

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Solid pattern

Split patternCore print


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10. Mould Making Technique using Split pattern

AIM: To make a mould using given split pattern.

APPARATUS REQUIRED: Split pattern, moulding box and moulding equipments.

PROCEDURE: i. Take the one half of the split pattern, place in the moulding box (cope box) at

correct position and pour the moulding sand using shovel and thoroughly ram it correctly.

ii. Rotate the moulding box place another half of the pattern correctly using dowel pin and fix another moulding box (Drag box) at appropriate position using lugs (aligning pin) and lock the pin. Fix the sprue pins at correct position for runner and riser.

iii. Pour the molding sand and ram the molding sand thoroughly using rammer using strike of remove the excess sand. Remove the sprue pins and separate the patterns.

iv. Remove the pattern using draw spike, cut the necessary gate way using gate cutter, fix the core at appropriate position draw the necessary vent hole using draw spike now the mould is ready to pour.

v. Again realign the moulding box and now the mould is ready to pour.

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RESULT: Thus the mould is prepared using given split pattern.

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casting, welding and metal forming lab

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