Technology Studies: Design and Technology Grade 8 Study Notes
Grade 8 Technology Studies: Design and Technology - Exhaustive Study Notes
Design Fundamentals
Definition of Ergonomics: Ergonomics deals with the relationship between designed products and the people who use them. It aims at improving workspaces, products, and environments so that people are comfortable, safe, and at ease when using products or systems.
Applications of Ergonomics:
Chairs: Designed for comfort and to reduce the risk of injury during prolonged use.
Crutches: Designed to be used by people of different heights and to be comfortable for the user.
Toothbrushes: Designed with handles that are appropriate for grip and usage.
Baby High Chair: Features include cushions for comfort, safety straps, flexible table tops for food/games, modular design for assembly/disassembly, and lack of small detachable parts.
Ergonomics in Workstations: Factors considered include:
Wheels attached to the chair for mobility.
Adjustable seat heights to accommodate different users.
Screens placed slightly above table level to match eye level.
Reclined seats and backs for comfort.
Proper lighting systems.
Appropriate clearance for knees and legs.
Ergonomic Hazards:
Improper or poor design can lead to pain, strain, and injuries.
Hard intensive work over long periods can cause serious injury.
Incorrect lifting of heavy objects causes back pain.
Improper postures (sitting, standing, or bending) can cause harm even if products are designed ergonomically.
Repetitive tasks (e.g., computer use, cashier work) can lead to wrist, arm, and shoulder injuries.
Etymology of Ergonomics: Created in 1857 by Wojciech Jastrzebowski. Derived from the Greek "Ergon" (work) and "nomos" (natural law), meaning "how to work according to nature."
Anthropometrics: A field of ergonomics dealing with body measurements of human beings. It uses body size data to improve the safety, comfort, and efficiency of products.
Importance of Anthropometrics:
Ensures a product is fit for use by many people.
Increases safety levels.
Contributes to user comfort.
Leads to higher work efficiency.
Anthropometric Data Examples:
A: Overall height.
B: Knee height.
C: Popliteal (back of knee) height.
D: Buttock to popliteal height / Buttock-knee length.
E: Sitting elbow height.
F: Sitting shoulder height.
Hand Dimensions: Used to estimate handle diameters.
Clothing Sizes: Based on chest and length measurements (e.g., Small, Medium, Large).
Orthographic Projection
Definition: A technique that represents a 3D object in different 2D views, typically front, side, and top views. These are drawn to scale and arranged in a definite manner to show shape and size.
Principal Views:
Front View: Also called the "Front Elevation."
Top View: Also called the "Plan."
Side View: Also called the "End Elevation."
First Angle Projection: The standard projection method used in this curriculum (Third Angle Projection is mentioned as a future topic).
Drawing Rules:
The side view is drawn on the right when viewed from the left, and vice versa in First Angle Projection.
Hidden Edges: Represented using broken (dashed) lines to describe internal features or voids not visible to the observer.
Inclined Surfaces: The true length of an inclined surface is only visible on the view where the surface appears as an edge (e.g., the front view if the slope is along that axis).
Dimensions:
$W$ = Width
$H$ = Height
$D$ = Depth
Development of Solids
Definition: A development (or "net") is a flattened 2D shape that, when folded and assembled, forms a specific 3D geometrical form.
Components of a Net:
Folding Lines: Indicate where the sections are to be bent.
Flaps/Glue Tabs: Provide surfaces for adhesive during assembly.
Geometrical Forms and Shapes:
Cube: Square.
Cuboid (Square base prism): Rectangle.
Cylinder: Circle cross-section/Rectangle body.
Triangular Prism: Triangle ends/Rectangle sides.
Cone: Triangle section/Circle base.
Pyramid: Triangle sides.
Cylinder Development Details:
The circumference of the curved surface is estimated by dividing the circle (top view) into 12 equal divisions and transferring those chord distances to the development.
Cone Development Details:
Features a flat circular base and a curved surface converging at a point called the "Apex."
Modelling Tools: Bristol paper, carbon paper (for transferring designs), HB pencil, ballpoint pen, ruler, bone folder (for scoring folds), scissors, and glue sticks.
Material Technology
Common Properties of Materials:
Strength: Ability to withstand force. Includes Compressive (resisting squeezing), Tensile (resisting stretching), and Shear (resisting parting).
Toughness: Ability to withstand sudden shocks without breaking (e.g., mild steel).
Brittleness: Propensity to break easily with sudden shock (e.g., cast iron, glass).
Hardness: Resistance to wear, abrasion, and cuts (e.g., glass).
Malleability: Ability to be deformed (stretched, hammered, or flattened) without cracking (e.g., tin, copper, aluminium, lead).
Ductility: Ability to be drawn out into thin wires or threads (e.g., silver, copper).
Electrical Conductivity: Ability to allow electricity to flow. Materials that do not are "insulators" (rubber, plastic).
Thermal Conductivity: Ability to transfer heat. Materials that do not are "thermal insulators" (wood, ceramic).
Wood Classification:
Hardwood: Broad leaves, seeds in fruit, slow growth, temperate/warm climates. Examples: Teak, Meranti, Mahogany (Sapele), Beech, Ash.
Softwood: Needle-like leaves, cone-bearing, fast growth, temperate/cold climates. Examples: Pine, Douglas fir, Red cedar.
Metals Classification:
Ferrous: Contain iron, attract magnets, and rust if unprotected. Examples: Mild steel, Cast iron, Stainless steel (alloyed with chromium and nickel), High carbon steel.
Non-Ferrous: Do not contain iron, do not rust, not magnetic. Examples: Copper, Aluminium, Brass (copper-zinc alloy), Tin.
Recycling: The process of converting waste into new materials. Primary collected materials in Mauritius include paper/cards, metals, and plastics.
Tool Technology
Classification of Tools:
Measuring and Marking Out: Steel Rule, Measuring Tape, Pencil, Scriber (for metal), Felt Pen (for plastic), Sliding Bevel (for angles), Try Square (90 degrees on wood), Engineer Square (90 degrees on metal), Compasses/Dividers, Marking Gauge (parallel lines on wood).
Holding Tools: Bench Vice (wood), Engineer's Vice (metal), G-Clamp, Pliers, Sash Clamp (large workpieces), Corner Clamp, Bench Hook (sawing support), Mitre Box (45-degree cuts).
Driving Tools: Wooden Mallet, Ball Pein Hammer (nails/riving/bending), Screwdriver (flat or cross-blade), Spanner (nuts and bolts).
Cutting Tools:
Saws: Hand Saw (large boards), Back/Tenon Saw (straight cuts), Coping Saw (curved lines in wood/plastic), Hacksaw (metal/plastic), Junior Hacksaw, Abrafile (curves in metal).
Chisels: Wood Chisel (with mallet), Cold Chisel (metal, with hammer).
Planes: Jack Plane (wood sizing), Spokeshave (curved lines).
Filing: Wood Rasp, Metal Files (flat, square, triangular, round).
Drilling: Hand Drill, Drilling Machine.
Safety Considerations: Wear goggles, clamp workpieces securely, use correct tool grips, and ensure machines are cleaned and keys are removed from chucks after use.
Joining Methods
Classification of Joints:
Permanent: Cannot be undone without damage (e.g., welded, glued, riveted).
Temporary: Can be disassembled without damage (e.g., bolted, screwed, knock-down fittings).
Rigid: No relative movement (e.g., nailed).
Flexible: Allows movement (e.g., hinges, pin joints).
Specific Joining Techniques:
Screwing: Uses Countersunk (flush) or Round head screws. Slots include Straight, Philips, and Posidriv.
Bolting: Uses Bolts, Nuts (Hexagonal, Wing), and Washers to protect surfaces.
Glueing (Adhesives):
Cascamite/PVA: For wood.
Epoxy Resin: Two-part (resin/hardener) for wood, metal, glass, plastic.
Contact Adhesive: For large wood surfaces/formica.
Plastic Cement: For PVC/acrylics.
Riveting: Using soft steels or aluminium rivets; includes Solid and Pop riveting.
Common Wood Joints: Butt joint, Mitre joint (picture frames), Housing joint (shelves), Dowel joint, Mortise and Tenon, Finger joint.
Knock Down (KD) Fittings: Corner blocks, hinges, catches (magnetic/mechanical), and corner plates.
One-Point Perspective
Definition: A drawing technique representing objects in a natural and realistic way by simulating optical illusion (objects appear smaller as they move further away).
Key Technical Terms:
Vanishing Point (VP) or Centre of Vision (CV): The imaginary point where parallel lines seem to meet.
Horizon Line / Eye Level: Represents the actual height of the viewer's eyes.
Convergence Lines / Orthogonal Lines: Lines from the object that converge toward the CV.
Rules for One-Point Perspective:
Uses a single Vanishing Point.
Orthogonal lines are drawn faint (thin).
Visible edges are drawn thick (regular).
The "Crate Method" is used to construct complex blocks by drawing the overall bounding box first.
The Design Process
Sequence of Stages:
Identification of Problem: Describing a situation and defining the need.
Design Brief: A clear statement of the intended task (e.g., "To design and make a key holder").
Research and Analysis: Analyzing existing products and user needs.
Specifications: A list of requirements (Size, material, function, safety).
Generation of Ideas: Sketching multiple possible solutions.
Selection of Idea: Evaluating ideas against specifications using a ranking system to choose the best solution.
Development of Selected Idea: Refining the chosen idea through changes in shape, aesthetics, and material choice.
Final Design / Working Drawing: Producing a final pictorial drawing and an orthographic projection with dimensions.
Product Planning: Creating a cutting list and a flow chart for production steps.
Realisation: The making stage using tools and equipment while following safety precautions.
Testing and Evaluation: Checking the finished product against the original specifications and gathering user feedback.
Realisation Steps (Example - Key Holder):
Preparation: Planing wood to datum edges and check for flatness/squareness.
Marking: Using try squares, pencils, and marking gauges.
Cutting: Using tenon or coping saws.
Shaping: Using spokeshaves, files, or rasps.
Finishing: Applying sanding sealer and varnish (done in well-ventilated areas with respiratory masks).
Assembly: Fixing parts (e.g., hooks) to the base using screws or adhesives.