Question

How can we eliminate the shrinkage cavity?

(a) By increasing riser height

(b) By reducing riser height

(c) Reducing the number of risers

(d) By using an open riser

The question was posed to me during a job interview.

My doubt stems from Riser Design in section Pattern and Mould, Principles of Gating & Risering of Casting-Forming-Welding I

Answer 1

The correct choice is (a) By increasing riser height

To explain: If riser height is reduced, the pipe will extend to cast cavity. Similarly, if less no of the riser is used it will not satisfy feeding distance. Open riser alone can’t help in reduction of the cavity. But by increasing length of the riser, the pipe can be controlled in riser itself eliminating shrinkage cavity in casting.