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2.2 Orthographic projections in drawings

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Technology

Grade 9

Architectural planning

Module 8

Orthographic projections in drawings

Activity 1:

To be able to distinguish between types of lines that are used in drawings

  • Several different types of line are used to make drawings clearly understandable. . The appearance of a final drawing will depend on the quality of the lines drawn, so it is certainly worth taking care in this area.

Orthographic projection: First Angle and Third Angle Projection. The views in both will be the same but the projection on paper differs. The symbols below are used on drawings to indicate which projection is used.

First angle projection symbol

Third angle projection symbol

  • For this exercise we will only look at First Angle Projection. Your educator will provide you with grid paper which makes it easier for you to draw. If you have drawing equipment it is even better.
  • Always start by drawing the front elevation since this will determine the position of the other views. The plan view is drawn below the front elevation, and the end views on the side furthest away from their position on the front view. Each view only shows two dimensions and together they combine to give a three-dimensional description of the object.
  • The example below illustrates Orthographic views in the first angle projection.

Focus task a

  • Draw a first angle projection of your space case on scale 1:2

END A ELEVATION

FRONT ELEVATION

END B ELEVATION

PLAN

LO 1.5 LO 1.9

Activity 2:

To be able to draw dimension drawings

  • Drawings need to be dimensioned to show what the size of the object is in real live. The dimensions should be the real dimensions of the object. There are international rules for the application of dimensions:
  • All dimensions should be read from the bottom or right-hand side of the paper
  • Limit lines should be drawn out from the object and numbers written above the dimensioning lines stretching between these
  • Smaller measurements should be placed closer to the drawing

Study these examples:

diameters

RADII

POSITION OF HOLES

SIZE OF HOLES

LO 1.15

Assessment

Learning outcomes(LOs)
LO 1
TECHNOLOGICAL PROCESSES AND SKILLS The learner will be able to apply technological processes and skills ethically and responsibly using appropriate information and communication technology.
Assessment standards(ASs)
We know this when the learner:
investigates:1.1 identifies and explains a problem, need or opportunity from a real-life context, and investigates the context, the nature of the need, the environmental situation, and the people concerned;
1.4 uses a variety of available technologies and methods to:
  • locate (e.g. use library referencing system, database searches, indexes);
  • collect (questionnaires, data collection forms, requests for information, information searches, literature surveys);
  • compare;
  • sort;
  • verify;
  • evaluate;
  • store information;
designs:1.5 writes or communicates a short and clear statement or a design brief for the development of a product or system related to a context, problem, need or opportunity that has been identified by self;
1.6 lists product specifications and design specifications and constraints for a solution to an identified problem, need or opportunity based on all of the design key words listed below:
  • people, age, target market, human rights, access;
  • purpose, function, what the product will do;
  • appearance and aesthetics: form, colour, shape, feel;
  • environment: where product will be used or made, impact on the environment in the long and short term;
  • safety: for users and manufacturers;
  • cost, cost of materials, wastage, cost of manufacture, maximum selling price;
  • ergonomics;
  • quality;
  • production;
1.7 generates a range of possible solutions that are significantly different from each other, and that show clear links to the design brief and specifications and constraints;
makes:1.9 develops plans for making that include all of the following:
  • resource lists (e.g. materials lists, tools, people, cost);
  • formal drawings showing dimensions or quantities (e.g. orthographic, oblique or isometric views, sequence drawings, exploded views);
  • manufacturing sequence;
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Source:  OpenStax, Technology grade 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11071/1.1
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