Lesson Notes By Weeks and Term v5 - Grade 8

Lesson Video

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Performance objectives

• Identify and describe three materials processing methods.
• Explain the application of these methods in manufacturing.
• Compare and contrast two different processing methods.
• Propose a manufacturing process for a simple product.
• Evaluate the environmental impact of a processing method.

Lesson summary

Processing materials is a fundamental part of technology and manufacturing. Every product we use, from the chair you're sitting on to the cell phone in your pocket, has gone through some form of processing. In South Africa, understanding materials processing is crucial for developing our local industries, creating jobs, and utilising our natural resources sustainably. For example, South Africa is rich in minerals like iron ore, which needs to be processed into steel for construction, manufacturing, and infrastructure development. Understanding these processes will equip you to become innovative problem-solvers and potential contributors to the South African economy.

Lesson notes

What is Materials Processing? Materials processing refers to the methods and techniques used to change the shape, properties, or surface finish of raw materials into useful products or components. It's the bridge between the materials we find in nature (or create in labs) and the things we use every day.

Common Materials Processing Methods: Here are some commonly used materials processing methods: Cutting: Separating a material into two or more pieces. This can be achieved through various methods, including sawing, shearing, laser cutting, water jet cutting, and abrasive cutting. The choice of cutting method depends on the material being cut, the required precision, and the desired finish.

Example:* Cutting wood using a saw to make furniture components. Cutting sheet metal using shears to make car panels.

South African Context:* Cutting timber for construction of RDP houses, cutting stone for building in Cape Town.

Shaping: Changing the form or contour of a material without removing any material (except in cases where a specific shape is desired via material removal).

Common shaping methods include: Bending:* Forming a material into a curved shape. This is often done using presses or rollers.

Example:* Bending metal sheets to create the body of a car. Bending PVC pipes for plumbing.

Forging:* Shaping metal by hammering or pressing it while it's hot. This is often used to create strong, durable parts.

Example:* Forging tools like hammers and spanners.

Molding:* Forming a material into a specific shape by pouring it into a mold. This is commonly used for plastics and metals.

Example:* Injection molding of plastic bottles and containers. Sand casting of metal engine blocks.

Extrusion:* Forcing a material through a die to create a long, continuous shape. This is often used for metals and plastics.

Example:* Extruding aluminum to create window frames. Extruding plastic to create pipes.

Joining: Connecting two or more pieces of material together.

Common joining methods include: Welding:* Fusing two pieces of metal together using heat.

Example:* Welding steel beams for building construction. Welding pipes for pipelines.

Soldering:* Joining two pieces of metal together using a lower-melting-point metal (solder).

Example:* Soldering electronic components onto circuit boards.

Brazing:* Similar to soldering, but uses a higher-melting-point filler metal (braze).

Example:* Brazing copper pipes together.

Adhesive Bonding:* Using glue or adhesive to join two pieces together.

Example:* Gluing wood together to make furniture. Using adhesives to bond car panels.

Mechanical Fastening:* Using screws, bolts, rivets, or other fasteners to hold two pieces together.

Example:* Screwing together wood panels to make a cabinet. Bolting together steel structures.

Surface Treatment: Altering the surface properties of a material to improve its appearance, durability, or resistance to corrosion.

Painting:* Applying a coating of paint to protect a surface from rust or corrosion, or to enhance its appearance.

Powder Coating:* Applying a dry powder coating to a surface and then heating it to fuse it together. This is often used for metal products.

Electroplating:* Coating a metal surface with a thin layer of another metal (e.g., chrome plating).

Worked example

Example 1: Manufacturing a Metal Gate

A small business in Soweto manufactures metal gates for residential properties.

Let's consider the processes involved:

Cutting: Steel tubing and sheet metal are cut to the required lengths and shapes using a metal cutting saw and shears.

Shaping: The steel tubing may be bent using a bending machine to create decorative curves.

Joining: The various pieces of steel are welded together to form the gate frame and decorative elements.

Surface Treatment: The gate is then sandblasted to remove any rust and scale, followed by painting with a corrosion-resistant paint.

Example 2: Manufacturing a Wooden Chair

A furniture workshop in Knysna produces wooden chairs:

Cutting: Timber logs are cut into planks using a sawmill. The planks are then cut to the required dimensions for the chair components using saws.

Shaping: The chair legs and backrest are shaped using woodworking tools like planers, routers, and chisels. Some shaping may involve bending, achieved through steaming the wood.

Joining: The chair components are joined together using glue, screws, or dowels.

Surface Treatment: The chair is sanded smooth and finished with varnish or paint.