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GATE 2016 ME (ME1) – Question 61

Casting, Forming and Joining Processes · Casting: patterns, moulds, cores, solidification, riser and gating design, defects · 2 marks · Multiple choice

A cylindrical job with diameter of 200 mm and height of 100 mm is to be cast using modulus method of riser design. Assume that the bottom surface of cylindrical riser does not contribute as cooling surface. If the diameter of the riser is equal to its height, then the height of the riser (in mm) is

  1. 150
  2. 200
  3. 100
  4. 125

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Correct answer: (A) 150

Explanation

Casting volume isπD²H/4 and its full cooling area isπDH+πD²/2, giving Mc=25mm for D200,H100. For a riser with diameter=height=h and bottom excluded, Mr=(πh³/4)/(πh²+πh²/4)=h/5. The conventional design assumption Mr=1.2Mc gives h=5·30=**150mm, A**. The1.2 safety factor is implicit in the keyed choice.