ME-305 Manufacturing Process - Jun 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
   aA cylindrical riser of $6\text{ cm}$ diameter and $6\text{ cm}$ height has to be designed for a sand-casting mould for producing a steel rectangular plate casting of $7\text{ cm} \times 10\text{ cm} \times 2\text{ cm}$ dimensions having the total solidification time of $1.36\text{ minute}$. What is the total solidification time (in minute) of the riser?
   How to answer

   • State Chvorinov's rule: $t_s = C (V/A)^2$
   • Calculate Volume and Surface Area of the rectangular casting
   • Determine the mould constant $C$ using $t_{s,\text{casting}} = 1.36\text{ min}$
   • Calculate Volume and Surface Area of the cylindrical riser (top or side type)
   • Compute the solidification time of the riser $t_{s,\text{riser}}$
2. 7 Marks
   bExplain the procedure of investment casting with neat sketch, what are the advantages limitations and applications of investment casting?
   How to answer

   • Define investment casting (lost-wax casting process)
   • Step-by-step procedure: wax pattern making, tree assembly, slurry dip/stuccoing, dewaxing, firing, pouring, shell removal
   • Schematic diagram of the process steps
   • Key advantages (excellent surface finish, dimensional accuracy, complex geometries)
   • Limitations (high cost, time consuming) and typical applications (turbine blades, jewellery, medical implants)
3. 7 Marks
   aA cylindrical blind riser with diameter $d$ and height $h$, is placed on the top of the mold cavity of a closed type sand mold as shown in the figure. If the riser is of constant volume, then the rate of solidification in the riser is the least when the ratio of $h : d$ is _______. Comment on the results.
   How to answer

   • Relate rate of solidification to cooling surface area: least rate means minimum heat dissipation area for constant volume
   • Write expression for volume $V = \frac{\pi}{4} d^2 h$ and heat transfer area $A$
   • Express area in terms of $d$ and $V$: $A(d)$
   • Differentiate $dA/dd = 0$ to find optimal condition
   • Determine the ratio $h/d$ and comment on the result
4. 7 Marks
   bWhat are chills, Chaplets and core prints, explain their applications in casting with neat sketch.
   How to answer

   • Define chills (internal/external) and explain role in directional solidification
   • Define chaplets and explain role in supporting cores inside mold cavity
   • Define core prints and explain their function in locating and seating cores
   • Draw neat sketches for chills, chaplets, and core prints in a casting mold
5. 7 Marks
   aA cubic casting of $50\text{ mm}$ side undergoes volumetric solidification shrinkage and volumetric solid contraction of $4\%$ and $6\%$ respectively. No riser is used. Assume uniform cooling in all directions. Find the side of the cube after solidification and contraction. Explain your assumption in brief.
   How to answer

   • Calculate initial volume $V_0 = 50^3 = 125,000\text{ mm}^3$
   • Discuss the role of solidification shrinkage without riser (forms shrinkage cavity / pipe vs external dimensions)
   • Apply solid contraction to calculate final external volume $V_f$
   • Compute final cube side $a_f = V_f^{1/3}$
   • Explain assumptions regarding uniform volumetric contraction and location of shrinkage void
6. 7 Marks
   bDifferentiate the hot working and cold working process. Justify which process is best suitable for wire drawing?
   How to answer

   • Define hot working (above recrystallization temperature) and cold working (below recrystallization temperature)
   • Tabulate differences: working temperature, strain hardening, surface finish, dimensional tolerances, residual stresses, force required
   • Identify wire drawing as predominantly a cold working process
   • Justify choice: cold working provides high tensile strength, precise dimensions, and good surface finish necessary for wires
7. 7 Marks
   aWhat is the use of Pattern Allowance in casting?
   How to answer

   • Define pattern allowance as intentional modifications to pattern dimensions
   • Explain why allowances are required (metal shrinkage, draft for mold removal, machining allowance, distortion correction, shake allowance)
   • State the importance in achieving exact final component specifications
8. 7 Marks
   bDefined each of them with the neat sketch.

   1. i)Shrinkage Allowance
   2. ii)Draft Allowance
   3. iii)Machining Allowance
   4. iv)Deformation or Camber Allowance
   5. v)Shake or Rapping Allowance
   How to answer

   • Define Shrinkage Allowance with sketch showing oversize pattern
   • Define Draft Allowance (taper) with sketch showing taper angle on vertical surfaces
   • Define Machining Allowance with sketch showing extra metal layer
   • Define Camber/Distortion Allowance with sketch showing pre-curved pattern
   • Define Shake/Rapping Allowance with note on negative allowance
9. 14 Marks
   A low carbon steel plate is to be welded by the manual metal arc welding process using a linear $V - I$ characteristic DC Power source. The following data are available: OCV of Power source $= 62\text{ V}$ Short circuit current $= 130\text{ A}$ Arc length, $L = 4\text{ mm}$ Traverse speed of welding $= 15\text{ cm/s}$ Efficiency of heat input $= 85\%$ Voltage is given as $V = 20 + 1.5\ L$ Calculate the heat input into the work price
   How to answer

   • Find arc voltage: $V = 20 + 1.5(4) = 26\text{ V}$
   • Use linear power source characteristic: $V = V_0 - \left(\frac{V_0}{I_s}\right) I \implies 26 = 62 - \left(\frac{62}{130}\right) I$
   • Solve for welding current $I$
   • Calculate net power: $P_{\text{net}} = \eta \cdot V \cdot I$
   • Calculate heat input per unit length: $H = \frac{\eta V I}{v}$ in $\text{J/cm}$ or $\text{J/mm}$
10. 7 Marks
    aIn an arc welding operation, carried out with a power source maintained at $40\text{ volts}$ and $400\text{ amperes}$, the consumable electrode melts and just fills the gap between the metal plates to be butt welded. The heat transfer efficiency for the process is $0.8$, melting efficiency is $0.3$ and the heat required to melt the electrode is $20\text{ J/mm}^3$. If the travel speed of the electrode is $4\text{ mm/s}$, what is the cross-sectional area, in $\text{mm}^2$, of the weld joint?
    How to answer

    • Total power input: $P = V \times I = 40 \times 400 = 16,000\text{ W}$
    • Heat rate utilized for melting: $H_m = \eta_h \times \eta_m \times P = 0.8 \times 0.3 \times 16,000 = 3,840\text{ J/s}$
    • Rate of melting: $u_m \times A_w \times v = 3,840$
    • Solve for cross-sectional area: $A_w = \frac{3840}{20 \times 4} = 48\text{ mm}^2$
11. 7 Marks
    bWhat are different welding defects? What are the remedies of weld splitters and porosity control for ideal welding?
    How to answer

    • List common welding defects: porosity, spatters, cracks, undercut, incomplete penetration, slag inclusion
    • Explain causes of weld spatter (high current, excessive arc length, incorrect shielding gas)
    • Give remedies for spatter control (optimize current/voltage, maintain proper arc length, use correct shielding)
    • Explain causes of porosity (entrapped gas, moisture on electrode, grease/rust on work)
    • State remedies for porosity (clean workpiece, dry electrodes, adequate gas flow rate)
12. 7 Marks
    aA hole of $20\text{ mm}$ diameter is to be drilled in a steel block of $40\text{ mm}$ thickness. The drilling is performed at rotational speed of $400\text{ rpm}$ and feed rate of $0.1\text{ mm/rev}$. The required approach and over run of the drill together is equal to the radius of drill. Find the drilling time (in minute).
    How to answer

    • Calculate total drill travel: $L = \text{thickness } t + (\text{approach } A + \text{over run } O) = 40 + 10 = 50\text{ mm}$
    • Calculate feed per minute: $f_m = f \times N = 0.1 \times 400 = 40\text{ mm/min}$
    • Compute drilling time: $T = \frac{L}{f \cdot N} = \frac{50}{40} = 1.25\text{ minutes}$
13. 7 Marks
    bWhat is the difference between elastic and plastic deformation.
    How to answer

    • Define elastic deformation as reversible and temporary deformation below yield strength
    • Define plastic deformation as permanent and irreversible deformation above yield strength
    • Compare on: reversibility, atomic bond stretching vs dislocation motion, Hooke's law applicability, stress-strain behavior
14. 7 Marks
    aWhat is forging and deep-drawing defect and their remedies?
    How to answer

    • Identify major forging defects: laps/folds, cold shuts, flash cracking, scale pits, and their remedies
    • Identify major deep drawing defects: wrinkling in flange/wall, tearing/fracture, earing, surface scratches
    • Discuss remedies for deep drawing defects: optimal blank holder pressure, proper die and punch corner radii, adequate lubrication
15. 7 Marks
    bExplain, with neat sketch i) Perfecting ii) Notching iii) Lancing iv) Embossing
    How to answer

    • Explain Perforating (printed as Perfecting): punching multiple close holes in sheet metal, with sketch
    • Explain Notching: removing a piece of scrap from the edge of a sheet/strip, with sketch
    • Explain Lancing: cutting along a line and bending simultaneously without removing material, with sketch
    • Explain Embossing: creating raised or indented designs using matched male and female dies without changing sheet thickness, with sketch