Question

What is the best casting process to produce 1,000,000 parts from cast iron with very low cost and why? List 3 casting defects and describe the reason to cause these and how to prevent these defects.

Answer 1

1) metal mold casting process is best suited for mass production of similar cast iron parts at low cost because metal molds which are inexpensive are not discarded after use and can be used over and over again.

2) casting defects :-

• Run out is when liquid metal leaks out of the mold, leading to an incomplete or missing casting.To prevent this casting defect, design the casting mold with precision. Inspect and replace any defective molds before casting. High temperatures can lead to excess wear and tear of the mold. Use quality raw materials for your mold that can resist high temperatures.
• Swells are an enlargement of the casting. Swells typically take on the shape of a slight, smooth bulge on the vertical face of castings.Swell is usually caused by improper or soft ramming of the mold or a low strength mold.Molds should be built to withstand liquid metal pressure. Otherwise, the mold wall may give way or move back, causing swelling. Using a strong, properly rammed mold prevents swells.
• Cold shut is a type of surface defect. You’ll see a line or crack with a round edge on the casting surface.This defect is visible to the naked eye and often results in rejecting the cast, as it creates a weak spot.When molten metal enters the mold from two gates, the streams will meet at a junction. Low temperature  can prevent fusion at the junction, causing the streams to solidify before fusion, creating a cold shut. Cold shut is usually a result of a lack of fluidity of the molten metal, or a poor design of the gating system.The best way to prevent cold shuts is to increase fluidity of the molten metal.