Question

Which of the following is the purpose of runner extension?

(a) To make smooth surface finish

(b) To make the casting of specific size and shape

(c) To remove slag and dross from the metal

(d) To make fast cooling of molten metal

I had been asked this question during an online exam.

I would like to ask this question from Gating Design topic in division Pattern and Mould, Principles of Gating & Risering of Casting-Forming-Welding I

Answer 1

Correct option is (c) To remove slag and dross from the metal

The best I can explain: The metal which moves first into the gating system is likely to contain slag and dross which should not be allowed to get into the mould cavity. This could be achieved by extending the runner beyond the in-gate so the clean metal can be expected to go into the mould after completely filling the runner extension.