Lesson Notes By Weeks and Term v4 - SHS 3
Safety, Quality and the Environment
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Safety, Quality and the Environment
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Subject: Manufacturing Engineering
Class: SHS 3
Term: 1st Term
Week: 11
Grade code: 1.3.2.LI.2
Strand code: 3
Sub-strand code: 3
Content standard code: 1.3.2.CS.2
Indicator code: 1.3.2.LI.2
Theme: Manufacturing Tools, Equipment and Processes
Subtheme: Safety, Quality and the Environment
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This lesson introduces three fundamental sheet metal working operations: cutting, bending, and drawing. Sheet metal work is all around us in Ghana. From the roofing sheets that protect our homes and schools, to the metal trunks ("chop boxes") we use for storage, the cooking pots ("dadessn") used in our kitchens, and even the bodies of tro-tros and cars. Understanding how to safely shape metal sheets with high quality is a vital skill in modern manufacturing and local artisanship.
A. Introduction to Sheet Metal Definition: Sheet metal is simply metal that has been formed into thin, flat pieces. It is one of the most common materials in manufacturing because it is strong, durable, and can be easily formed into complex shapes. Common Types in Ghana: Mild Steel: Strong and cheap. Used for car bodies, metal gates, and structural parts. Prone to rust if not coated. Galvanized Steel: Steel coated with a layer of zinc to prevent rusting. This is what is commonly used for roofing sheets, water tanks, and buckets. Aluminium: Lightweight, resistant to rust, and a good conductor of heat. Used for cooking pots, drink cans, and long-span roofing. Stainless Steel: Resistant to rust and corrosion, very hygienic. Used for kitchen sinks, cutlery, and medical equipment. It is more expensive. B. Operation 1: Cutting
Cutting is the process of separating a piece of sheet metal from a larger sheet or removing unwanted material. The primary mechanism is shearing, where two sharp blades apply opposing forces to slice through the metal.
i. Cutting Processes & Tools: Shearing/Guillotining: Used for making long, straight cuts. The sheet is clamped, and a moving upper blade comes down past a fixed lower blade, much like a giant pair of scissors. Tool: Guillotine or Power Shear. Blanking: A stamping operation where a piece of metal (the "blank") is punched out of a larger sheet. The punched-out piece is the desired product. Think of using a cookie cutter on dough. Tool: Punch and Die set in a Press. Punching (or Piercing): Similar to blanking, but the goal is to create a hole in the sheet metal. The material punched out is the waste (a "slug"), and the sheet with the hole is the desired product. Tool: Punch and Die set in a Press.
ii. Safety, Quality, and Environment for Cutting: Safety: Sharp Edges: Cut metal edges are extremely sharp and can cause deep cuts. Always wear thick leather or cut-resistant gloves when handling sheet metal. Pinch Points: Machines like guillotines and presses have powerful moving parts. Keep hands and fingers far away from the blades and dies. Use guards provided on the machine. Flying Debris: Small pieces of metal can fly off during cutting. Always wear safety glasses or a face shield. Quality: Burrs: A good cut should be clean and smooth. A poor cut leaves a rough, sharp edge called a burr. Burrs are a safety hazard and look unprofessional. They can be removed by filing. Accuracy: The dimensions of the cut piece must be precise. Measure carefully using a steel rule or vernier caliper before and after cutting. Ensure the workpiece is securely clamped before cutting. Environment: Scrap Management: Cutting always produces scrap metal. Do not leave sharp off-cuts lying around. Collect all scrap in a designated bin. Recycling: Metal is highly recyclable. Workshops should sell their scrap metal to recycling companies. This saves energy and reduces the need for mining new ore. C. Operation 2: Bending