IIT Guwahati QUIZ 1 ME222 (Manufacturing Technology I) Duration: 60 mts Total: 50 marks

NOTE: Part C should be answered in the question paper itself. Provide figures wherever required. Data not given can be assumed.

Part A: Solve the following problems. (2 x 5 = 10 marks) 1. In casting experiments performed using a certain alloy and type of sand mold, it took 155

seconds for a cube-shaped casting to solidify. The cube was 50 mm on a side. (a) Determine the value of the mold constant Cm in Chvorinov's rule, (b) If the same alloy and mold type were used, find the total solidification time for a cylindrical casting in which the diameter = 30 mm and length = 50 mm. (a) V/A = 125000/15000 = 8.33 mm; Cm = 155/(8.33)2 = 2.232 s/mm2. (b) V = 35343 mm3; A = 6126 mm2; V/A = 5.77; ts = 2.232 (5.77)2 = 74.3 sec.

2. The total solidification times of three casting shapes are to be compared: (1) a sphere with diameter = 10 cm, (2) a cylinder with diameter and length both = 10 cm, and (3) a cube with each side = 10 cm. The same casting alloy is used in the three cases. (a) Determine the relative solidification times for each geometry. (b) Based on the results of part (a), which geometric element would make the best riser? (c) If Cm = 3.5 min/cm2 in Chvorinov's rule, compute the total solidification time for each casting. (a) Sphere: V = 4/3r3; A = 4 r2; V/A = 1.667 cm; ts = (1.667)2Cm = 2.778 Cm Cylinder: 2.778 Cm; Cube: 2.778 Cm (b) All three geometries are good for making risers (c) ts (for all cases) = 2.778 x 3.5 = 9.723 min.

Part B: Answer the following. (4 x 6 = 24 marks) 3. Explain bedding-in method and false cope in making mold with their significance. 4. Explain the significance of, (i) core print, (ii) chaplets, and (iii) tins. 5. Explain vertical and bottom gating methods. Derive expression for filling time in bottom

gating method. 6. Write short notes on vacuum molding.

Part C: Answer the following in two or three lines clearly. (4 x 4 = 16 marks)

7. Identify the three sources of contraction in a metal casting after pouring.

8. What is significance of chill in casting?

9. What is runner in casting practice? What is its significance?

10. A mold cavity has the shape of a cube, 100 mm on a side. Determine the dimensions and volume of the final cube after cooling to room temperature if the cast metal is copper. Assume that the mold is full at the start of solidification and that shrinkage occurs uniformly in all directions. For Cu, solidification shrinkage is 4.9%, solid contraction during cooling is 7.5%. Volume of cavity = V = 1003 = 1000000 mm3 volume of casting = a3 = v = 1000000 (1-0.049) (1-0.075) = 879675 mm3 dimensions of cube = a = 95.82 mm.