Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

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Performance objectives

• Explain the sand casting process.
• Identify the materials and tools used.
• Describe the steps involved in sand casting.
• Evaluate the advantages and disadvantages of sand casting.

Lesson summary

Welcome, students. Look around you. The metal legs of your desk, the engine block in a tro-tro, the heavy-duty cooking pot (*dadesen*) used at home, or the parts of a corn mill in your community – have you ever wondered how these complex metal shapes are made? Many are created using a very old but powerful technique called sand casting. This process involves pouring molten metal into a sand mould to form a desired shape. Understanding sand casting is fundamental to manufacturing because it is one of the most common and versatile ways to produce engineered components that power our industries and daily lives in Ghana.

Lesson notes

This section breaks down the entire sand casting process into understandable parts. A. What is Sand Casting?

Sand casting is a metal casting process that uses sand as the mould material. It is a net-shape or near-net-shape process, meaning the initial product is very close to the final desired shape. The process involves: Making a mould by packing sand around a model or pattern. Removing the pattern to leave a cavity in the sand. Pouring molten metal into the cavity. Allowing the metal to cool and solidify. Breaking away the sand mould to retrieve the metal casting. B. Key Terminology and Components

Before we look at the steps, let's understand the language of sand casting. Pattern: A replica or model of the object to be cast. It is used to create the cavity in the sand mould. Patterns are usually made from wood, metal, or plastic and are made slightly larger than the final product to account for metal shrinkage during cooling. Flask: The rigid frame that holds the sand mould. It is typically made of two parts: Cope: The top half of the flask. Drag: The bottom half of the flask. Moulding Sand: A special mixture of sand (usually silica sand), clay (as a binder), and water. It must be strong enough to hold its shape but also porous enough to allow gases to escape during pouring. Core: A separate insert placed inside the mould cavity to create hollow sections or internal features in the final casting (e.g., the hole in the middle of a pulley wheel). Mould Cavity: The hollow space in the sand mould, created by the pattern, which will be filled with molten metal. Gating System: A network of channels that delivers the molten metal to the mould cavity. It consists of: Pouring Basin: Where the molten metal is first poured. Sprue: A vertical channel through which the metal flows downwards. Runner: A horizontal channel that connects the sprue to the gates. Gate (or Ingate): The entry point where the molten metal enters the mould cavity. Riser: A reservoir of molten metal connected to the mould cavity. Its purpose is to feed extra molten metal to the casting as it shrinks during solidification, preventing defects like voids or shrinkage cavities. Parting Line: The surface where the cope and drag separate.

![A simple diagram showing a cross-section of a sand mould would be drawn on the board here, labelling all the parts above.] C. The Step-by-Step Sand Casting Process

Evaluation guide

• Explain the sand -casting process in manufacturing.
• Experiential Learning: Show learners a video of an industry -based sand -casting process and let
• learners, in think -pair-share groups, summarise the casting process and present their results to
• the class.