ME-305 Manufacturing Process - Dec 2023 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aCompare and contrast the principles and applications of centrifugal casting and continuous casting in industrial manufacturing. Highlight their advantages, limitations and suitable material choices for each process.
   How to answer

   • Working principle of centrifugal casting (mould rotation, inertial forces) vs continuous casting (water-cooled mould, continuous withdrawal)
   • Key applications for each process (e.g., pipes/sleeves vs billets/slabs)
   • Advantages and limitations of both methods
   • Suitable material selection for both techniques
2. 7 Marks
   bDiscuss the significance of electrode polarity in electric arc welding. Compare and contrast the effects of AC and DC welding on the weld bead geometry and penetration depth.
   How to answer

   • Definition and role of polarity in arc welding (straight vs reverse polarity)
   • Heat distribution at anode and cathode for DCEN (67% work, 33% electrode) and DCEP (33% work, 67% electrode)
   • Effects on bead width, height, and penetration depth
   • Characteristics of AC welding (balanced penetration and heat distribution)
   • Comparison sketch of penetration profiles
3. 7 Marks
   aDiscuss the role of gating and runners in the casting process. Provide a comprehensive analysis of how different gating and runner designs impact the quality, efficiency and overall cost-effectiveness of the casting production?
   How to answer

   • Function of gating system: sprue, runner, and ingates
   • Types of gating systems: top, bottom, parting line, step gating
   • Pressurized vs unpressurized gating systems
   • Impact on molten metal turbulence, air aspiration, and casting quality
   • Effect on casting yield, fettling cost, and process economics
4. 7 Marks
   bCompare and contrast the control mechanisms in TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) welding processes. Explain how these controls influence the welding speed and quality?
   How to answer

   • Non-consumable tungsten electrode (TIG) vs consumable wire electrode (MIG)
   • Control mechanisms in MIG: automatic wire feeder, voltage-current coordination (constant voltage power source)
   • Control mechanisms in TIG: manual/separate filler feed, high frequency arc initiation, constant current power source
   • Impact of parameter control on deposition rate, welding speed, precision, and weld quality
5. 7 Marks
   aAn engineering component requires a pattern allowance for shrinkage during casting. The linear shrinkage rate of the material used is 1.5%. If the final dimensions of the casting are intended to be $100\text{ mm} \times 80\text{ mm} \times 60\text{ mm}$, calculate the additional dimensions needed for the pattern considering the shrinkage rate.
   How to answer

   • Formula for shrinkage allowance: $\Delta x = x \times 0.015$
   • Calculate additional length: $100 \times 0.015 = 1.5\text{ mm}$
   • Calculate additional width: $80 \times 0.015 = 1.2\text{ mm}$
   • Calculate additional height: $60 \times 0.015 = 0.9\text{ mm}$
   • Final pattern dimensions: $101.5\text{ mm} \times 81.2\text{ mm} \times 60.9\text{ mm}$
6. 7 Marks
   bDetail the chemical reactions involved in Thermit welding. Discuss the essential conditions necessary for a successful Thermit weld and potential challenges in achieving them.
   How to answer

   • Thermit mixture composition ($3:1$ by weight of iron oxide to aluminium)
   • Chemical reaction equations ($8\text{Al} + 3\text{Fe}_3\text{O}_4 \rightarrow 9\text{Fe} + 4\text{Al}_2\text{O}_3$ and $2\text{Al} + \text{Fe}_2\text{O}_3 \rightarrow 2\text{Fe} + \text{Al}_2\text{O}_3$)
   • Ignition requirements (magnesium ribbon and barium peroxide)
   • Essential conditions: proper mold preparation, preheating, slag separation
   • Challenges: moisture contamination, oxidation, alignment of railway rails
7. 7 Marks
   aDescribe the techniques and considerations used in die casting to manage dimensional tolerances. Explain how die design, process optimization and material selection contribute to achieving tight tolerances in die-cast parts.
   How to answer

   • Techniques to manage tolerances (precision machining of dies, thermal management of mould)
   • Die design aspects: draft angles, parting line alignment, gating and venting placement
   • Process parameter optimization: injection pressure, plunger speed, cycle time, die temperature
   • Material factors: alloy shrinkage characteristics, fluidity, solidification range
8. 7 Marks
   bIdentify three common defects that can occur during welding and their respective causes. Propose suitable remedies for each defect to ensure high-quality welds.
   How to answer

   • Selection of three defects (e.g., Porosity, Undercut, Incomplete penetration/Slag inclusions)
   • For each defect: describe nature and visual appearance
   • Root causes: moisture/gas entrapment, excessive current/speed, incorrect bevel angle
   • Remedies: proper shielding gas, electrode baking, correct speed/current settings, proper edge preparation
9. 5 Marks
   aDescribe how TIG welding facilitates precise control over the welding process. Discuss the significance of the shielding gas and electrode selection in achieving precision.
   How to answer

   • Independent control of heat source (arc) and filler material addition
   • Electrode selection: pure tungsten, thoriated, lanthanated, zirconiated for DC/AC application
   • Role of shielding gases (Argon, Helium, or mixtures) on arc stability and bead profile
   • Applications where high precision is critical (aerospace, thin sheet fabrication)
10. 4 Marks
    bDefine the fundamental components of a lathe machine and describe the basic operations performed on a lathe.
    How to answer

    • List main components: bed, headstock, tailstock, carriage (saddle, cross-slide, compound rest, tool post), lead screw
    • Brief description of primary operations: straight turning, facing, taper turning, knurling, parting-off, threading
11. 5 Marks
    cA manufacturing plant is performing a blanking operation on a sheet metal with a width of $300\text{ mm}$ and a length of $500\text{ mm}$. The blanking process requires a 20% scrap margin on each side of the desired component. Calculate the maximum number of rectangular components that can be obtained from the sheet metal considering this scrap margin.
    How to answer

    • Identify given dimensions of the metal sheet ($300\text{ mm} \times 500\text{ mm}$)
    • Note the under-specified component dimensions in question text, stating assumptions clearly (or computing as fraction of total area)
    • Calculate unit layout pitch incorporating 20% scrap allowance on each side
    • Determine the integer number of blanks along length and width and compute maximum total components
12. 7 Marks
    aPropose preventive measures to minimize the occurrence of porosity defects in gas welding. Explain how gas flow adjustments and electrode manipulation can help mitigate porosity issues?
    How to answer

    • Causes of porosity in gas welding (gas entrapment, rust, oil, excessive oxygen)
    • Preventive measures: thorough surface cleaning, correct flux usage, dry materials
    • Role of gas flow adjustments: maintaining neutral flame, optimal flow rate to avoid atmosphere aspiration
    • Proper filler rod manipulation: uniform angle, continuous feed into the molten pool to avoid re-oxidation
13. 7 Marks
    bExplain the critical factors influencing the determination of pattern allowances. Provide examples where precision in allowance calculation significantly impacts the final casting quality and machining process.
    How to answer

    • Factors influencing pattern allowances: casting metal, mould rigidity, design complexity, machining requirements
    • Types of allowances: shrinkage, machining, draft, shake/rapping, distortion
    • Specific examples: undersized engine cylinder bore leading to failure during machining; excessive allowance increasing tool wear and machining cost
14. 7 Marks
    aExplain the difference between open-die forging and impression-die forging, highlighting their applications in the manufacturing industry.
    How to answer

    • Definition of open-die (flat/simple dies, unconstrained flow) vs impression-die (cavity dies, restricted flow, flash formation)
    • Key comparisons: dimensional accuracy, tool cost, production rate
    • Industrial applications of open-die (large shafts, rings, billets) vs impression-die (connecting rods, crankshafts, gears)
15. 7 Marks
    bCompare drop forging and horizontal forging machines in terms of their working principles and advantages in specific forging operations.
    How to answer

    • Working principle of drop forging (ram falling by gravity or assisted pressure onto an anvil)
    • Working principle of horizontal forging machines/upsetters (gripping dies and horizontal punch)
    • Advantages of drop forging (high impact energy, standard asymmetrical parts)
    • Advantages of horizontal forging (ideal for bar upsetting, bolt heads, valves, high automation)
    • Comparison summary table
16. 7 Marks
    aDescribe the main applications of grinding machines in metal working, emphasizing their advantages in precision machining.
    How to answer

    • Overview of grinding as a precision finishing process using abrasive wheels
    • Major applications: surface grinding, cylindrical grinding, centerless grinding, internal grinding
    • Advantages in precision machining: extremely tight tolerances ($< 0.005\text{ mm}$), superior surface finish, capability to machine hardened steels/materials
17. 7 Marks
    bExplain the basic functionality of a drilling machine and list two common types of drills used in metal working.
    How to answer

    • Basic functionality: spindle provides rotary cutting motion, feed mechanism advances the drill bit axially into the workpiece
    • Two common types of drills: twist drill (standard two-flute drill) and center drill (combination drill and countersink) / spade drill
    • Brief explanation of their construction and specific usages