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: 4
Grade code: 2.3.1.LI.2
Strand code: 3
Sub-strand code: 2
Content standard code: 2.3.1.CS.2
Indicator code: 2.3.1.LI.2
Theme: Manufacturing tools, equipment and processes
Subtheme: Manufacturing Processes
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This lesson focuses on the fundamental, hands-on process of creating simple engineering components using basic hand tools. In Ghana, from the local welder making burglar-proof doors in our communities to the technician repairing farm equipment, the ability to accurately mark out, cut, shape, and measure materials is a critical skill. It is the foundation of innovation, repair, and small-scale manufacturing. This practical lesson will take you through the entire sequence of operations, from reading a drawing to producing a finished component, emphasizing safety, precision, and the proper use of tools. This is a project-based lesson where you will apply theory to create something tangible.
The process of creating a component by hand follows a logical, step-by-step procedure. Rushing or skipping a step almost always leads to mistakes, wasted material, and potential injury. The Core Manufacturing Process Flow Interpretation of Drawing: Understand the required shape, dimensions, and tolerances. Preparation of Workpiece: Clean the material and prepare a surface for marking. Marking Out: Transferring the dimensions from the drawing onto the workpiece. Cutting: Removing excess material to get the rough shape. Shaping and Fitting: Refining the shape using files and other tools to achieve the final dimensions and surface finish. Measuring and Checking: Continuously verifying the dimensions for accuracy. Finishing: Deburring sharp edges and cleaning the final component.
Let's break down the key stages and the tools involved. A. Marking Out
This is the most critical stage. An error here will be carried through the entire process. The goal is to create clear, thin lines on the metal to guide your cutting and filing. Preparing the Surface: For mild steel, you can apply Marking Blue or chalk to the surface. This creates a coloured background, making the fine lines you will scribe much easier to see. Establishing a Datum: You cannot measure from a rough, uneven edge. The first step is to file one edge straight and one adjacent edge square (at 90°) to the first. These become your datum edges – two true surfaces from which all measurements are taken. You check for straightness with the edge of a steel rule and for squareness with a Try Square. Marking Out Tools: Steel Rule: Used for measuring lengths. When marking, hold it firmly against the workpiece. Scriber: A sharp, pointed steel tool used to scratch fine, accurate lines onto the metal surface. It should be tilted slightly in the direction of motion. Try Square: Has a stock and a blade at a fixed 90°. It is used for two main jobs: Checking for 'squareness' (90° angles). Drawing lines perpendicular to a datum edge. Centre Punch: Has a 90° point. It is used with a hammer to make a conical indentation to mark the centre of a hole to be drilled. This prevents the drill bit from 'wandering'. Dot Punch (Prick Punch): Has a 60° point. Used to make small, permanent marks along a scribed line to make it more visible, especially if the marking blue wears off.
Example: Marking out a 60mm x 40mm Rectangle File two adjacent edges of your workpiece straight and square. These are your Datum Edge A and Datum Edge B. Place the stock of the try square firmly against Datum Edge A. Slide your steel rule along the blade of the try square and use the scriber to make a small mark at 60mm. Slide the try square further down Datum Edge A and repeat the process. Place the steel rule connecting the two marks and scribe a clear line. This line is parallel to Datum Edge A. Repeat the process from Datum Edge B, measuring and marking at 40mm to complete the rectangle. B. Cutting