Lesson Notes By Weeks and Term v4 - SHS 3
Manufacturing Processes
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Manufacturing Processes
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Subject: Manufacturing Engineering
Class: SHS 3
Term: 2nd Term
Week: 6
Grade code: 2.3.2.LI.2
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.2.CS.2
Indicator code: 2.3.2.LI.2
Theme: Manufacturing tools, equipment and processes
Subtheme: Manufacturing Processes
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This lesson focuses on the fundamental processes used to join manufactured parts together. In Ghana, from the local carpenter assembling a new chair in Madina, to the welder in Suame Magazine fixing a vehicle, or the technician assembling a new piece of equipment for the Tema port, joining processes are everywhere. Understanding how to correctly and safely use fasteners like screws, bolts, and nuts (non-permanent joints) and techniques like welding (permanent joints) is a critical skill for any aspiring engineer or technician. This knowledge allows us to create strong, reliable products and repair existing ones, contributing directly to our local economy and infrastructure.
A. Introduction to Joining Processes
In manufacturing, we rarely make a complex product from a single piece of material. Instead, we create individual parts and then join them together. The methods we use for joining are broadly categorised into two types: Non-permanent and Permanent. Non-permanent Joints: These are joints that can be disassembled without damaging the components. This is ideal for parts that may need maintenance, replacement, or adjustment. The primary examples are screws, bolts, and nuts. Permanent Joints: These are joints that, once made, cannot be taken apart without destroying or seriously damaging the components. These are used when a very strong, permanent connection is needed. The primary example we will study is welding. B. Non-Permanent Joining: Screws, Bolts, and Nuts
These are mechanical fasteners that hold objects together. Screws A screw is a fastener with a threaded shank and a head. It works by cutting its own thread into the material as it is turned. This is why you can drive a screw directly into wood. Key Features: Head: Can be flat-head, cross-head (Phillips), hexagonal, etc., to match the screwdriver or tool. Shank: The body of the screw. Threads: The helical ridges that grip the material. Common Types in Ghana: Wood Screws: Coarse threads and a tapered point, designed specifically for wood. Used by carpenters for furniture. Machine Screws: Straight shank with fine threads. Used to join metal parts, often screwed into a pre-tapped hole. You find these in electronics and appliances. Self-Tapping Screws: Can form their own thread in thin metal sheets or plastic. Used for roofing sheets and vehicle bodywork.
*(Teacher to draw simple sketches on the board showing the difference in threads and points)* Bolts and Nuts A bolt is similar to a screw but is designed to be used with a nut. It does not cut its own thread. Instead, it passes through aligned holes in the parts to be joined and is secured by tightening a nut onto its threaded end. This creates a powerful clamping force. Components of a Bolted Joint: Bolt: Consists of a head and a threaded shank. Nut: A block with internal threads that matches the bolt's threads. Washer (Optional but recommended): A flat, thin ring of metal. Purpose of a Washer: Distributes the load from the bolt head and nut over a wider area, preventing damage to the component surface. Prevents the bolt or nut from loosening due to vibration.