Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Computer Aided Drawing (Pictoral and Auxiliary Views)
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Computer Aided Drawing (Pictoral and Auxiliary Views)
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Subject: Technical Drawings
Class: Senior Secondary 2
Term: 1st Term
Week: 6
Theme: Pictoral Drawing
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Use the computer to draw is ometric, oblique, and perspective views of simple shaped blocks. Use the computer to draw the 1st and 2nd auxiliary plans and elevations of shaped blocks. Use the computer to draw the auxiliary plans and elevations of cut geometrical solids.
Pictorial Drawing industries. For example, designing a unique chair with ergonomically angled backrests or a solar panel mounting frame might require auxiliary views to verify angles and material cuts for local fabrication.
8. Differentiation, Remediation and Extension 8.1 Differentiation Strategies Group Work: Create mixed-ability groups where stronger students can support struggling ones. Assign specific roles within the group (e.g., one operates CAD, another verifies dimensions, a third checks commands).
Varied Task Complexity: Provide a range of objects for practice, from very simple blocks to more complex solids with multiple inclined surfaces, allowing students to choose tasks suitable for their current level.
Visual Aids: For visual learners, provide pre-drawn orthographic views on handouts to guide their CAD drawing process, or short video tutorials showing specific commands. 8.2 Remediation Activities One-on-One Support: The teacher provides direct, focused guidance to students who are struggling with specific concepts or CAD commands.
Simplified Exercises: Provide extra practice exercises involving only the most basic CAD commands and very simple geometric shapes for pictorial and auxiliary views. For example, drawing only the base of an isometric block or just one auxiliary view of a flat inclined surface.
Re-demonstration: Re-demonstrate challenging steps or commands (e.g., `ISODRAFT` settings, projection line setup for auxiliary views) using a different example or at a slower pace.
CAD Command Drills: Focus on repetitive practice of fundamental CAD commands required for the lesson (e.g., drawing lines at specific angles, using `TRIM`, `OFFSET`). 8.3 Extension Activities (for high-achieving learners)
Advanced Pictorials: Challenge students to create more complex perspective drawings (e.g., three-point perspective) or to use 3D modeling features of the CAD software to generate renderings of their designs.
Parametric Design Exploration: Introduce the concept of parametric design, where students create designs that can be easily modified by changing key dimensions, and explore how auxiliary views update automatically in such a setup.
Real-World Design Challenge: Assign a small project requiring students to design a component relevant to a local industry (e.g., a specific part for a water pump, a farming tool, or a fixture for a furniture workshop). They must use appropriate pictorial and auxiliary views to fully detail their design, considering material and manufacturing processes. They could research common local issues and propose a CAD-designed solution. downwards at 45° until it meets the opposite top edge or a designated point on it, defining the slope. (e.g. from top right corner, draw line @-60,50 for an edge that meets 40mm from the top left corner, then connect the points). Or, if it's a simple gable, just draw a line from the midpoint of the top edge to the two bottom corners of that face.
2. Draw Plan (Top View): Project down from the Front Elevation to draw a 100mm x 60mm rectangle. Show the top edges of the inclined surface as projected.
3. Draw First Auxiliary Elevation: In the Front Elevation, identify the inclined surface. Draw a construction line (`X1-Y1`) parallel to the edge view of this inclined surface. From each corner (and any critical point) of the object in the Front Elevation, draw projection lines perpendicular to the `X1-Y1` line. Refer to the Plan view to get the 'depth' measurements. Measure the perpendicular distance from the `X-Y` line (reference line for Front/Plan) to each point in the Plan view. Transfer these distances onto the respective projection lines in the auxiliary view, measuring from the `X1-Y1` line. For example, the front edge of the base in the plan will be `0` from `X-Y`, while the back edge will be `60mm` from `X-Y`. These `0` and `60mm` distances are applied perpendicular to `X1-Y1`. Connect the transferred points to reveal the true shape of the inclined surface. Use `HATCH` if required to denote the inclined surface clearly.
Commentary: This exercise systematically teaches students to generate an auxiliary view to find the true shape of an inclined surface, a fundamental skill in engineering design.
5. Independent Practice (Questions Only)
1. Draw the isometric view of a step block with the following dimensions: Base 80mm x 60mm, overall height 50mm. The first step is 40mm high and 30mm deep from the front.
2. An engineer needs to represent a custom fabricated steel plate for a local bridge support. The plate is 120mm x 80mm, with a uniform thickness of 10mm. Draw its Cabinet Oblique view, with the 120mm x 80mm face as the front, and receding lines at 60°.
3. A simple wooden stool has a square top of 300mm x 300mm. Its legs are 400mm tall and flare outwards. Draw a 2-point perspective view of this stool, assuming an eye level that is slightly above the stool's top, and two vanishing points. (Hint: Focus on setting up the construction lines and conceptual representation in CAD).
4. A block has an inclined face. Its orthographic views are given (e.g., Front Elevation shows a sloping edge, Plan shows the full width). Draw the Front Elevation, Plan, and a First Auxiliary View showing the true shape of the inclined face. (Provide a simple sketch of the orthographic views for students).
5. A triangular prism (equilateral triangle base, 50mm side; length 80mm) is truncated by a cutting plane that cuts one edge at 30mm from the base and another edge at 60mm from the base. Draw the Front Elevation, Plan, and an Auxiliary View showing the true shape of the cut surface (section).
6. Draw the isometric view of a simple machine component (e.g., a 'pulley block' shape - a rectangular block with a semi-circular groove on its top face).
Overall dimensions: 80x50x40mm. Groove radius 20mm, centrally located.
7. Draw a Cavalier Oblique view of a small storage shed design. Front face is 5m wide, 3m high. Depth is 4m. Use 45° for receding lines. Include a centered door opening (1m wide, 2m high) on the front face.
8. An object has an oblique surface that is not perpendicular to any principal plane. After drawing its principal orthographic views and a first auxiliary view, draw a second auxiliary view that shows the true shape of this oblique surface. (Provide a sketch of the object with an oblique surface).
6. Evaluation and Assessment Evaluation Guide: "
1. Use the computer to draw given objects." Formative Assessment Strategies: Observation: The teacher will circulate during guided practice, observing students' proficiency with CAD commands (e.g., `ISODRAFT`, `LINE`, `ELLIPSE`, `TRIM`, projection methods) front face.
8. An object has an oblique surface that is not perpendicular to any principal plane. After drawing its principal orthographic views and a first auxiliary view, draw a second auxiliary view that shows the true shape of this oblique surface. (Provide a sketch of the object with an oblique surface).
6. Evaluation and Assessment Evaluation Guide: "
1. Use the computer to draw given objects." Formative Assessment Strategies: Observation: The teacher will circulate during guided practice, observing students' proficiency with CAD commands (e.g., `ISODRAFT`, `LINE`, `ELLIPSE`, `TRIM`, projection methods) and their ability to follow instructions. Immediate feedback will be provided.
Quick Checks: Ask specific questions about CAD settings or commands related to pictorial/auxiliary views (e.g., "How do you switch isometric planes?", "What is the purpose of an auxiliary view?").
Screenshot/File Submission: Students take screenshots of their progress or submit intermediate CAD files for quick review of their approach and accuracy during the lesson.
Summative Assessment Strategies: Practical CAD Test (End of Lesson/Week): Task: Students are given 2-3 complex objects (e.g., a block with a compound inclined surface, a truncated pyramid) and instructed to draw their: Isometric or Cabinet Oblique view. First Auxiliary View of a specified inclined surface. Auxiliary View showing the true shape of a given cut section.
Submission: Students will save their CAD files (`.dwg` or equivalent) and submit them electronically or for printout.
Marking Scheme/Rubric: Accuracy of Dimensions and Geometry (40%): Correct lengths, angles, positions of features. Correct Projection Technique (30%): Proper application of isometric/oblique rules, accurate projection for auxiliary views, correct transfer of distances. Completeness and Clarity (20%): All required views are drawn, visible and hidden lines are correctly represented (or removed), section lines are correctly applied (if applicable). CAD Proficiency (10%): Efficient use of CAD commands, proper layer management (if introduced), clean drawing environment.
Project Work (Extended): Students could be assigned a mini-design project, e.g., "Design a simple tool holder for a carpentry workshop in your community." They would then use CAD to draw pictorial and auxiliary views of their design components.
7. Real-life Applications / Integration
1. Architectural and Building Construction in Nigeria: CAD is indispensable for architects and civil engineers in Nigeria. Pictorial views (especially isometric and perspective) are used to visualise proposed building designs (e.g., residential bungalows, commercial complexes, schools). This helps clients understand the design better than traditional 2D plans. Auxiliary views are critical for detailing complex roof structures, staircases, or structural elements with inclined members, ensuring accurate fabrication and assembly on site. For example, an auxiliary view might be used to determine the true shape of a cut for a truss member in a building.
2. Manufacturing and Fabrication Industry: In sectors like metal fabrication, automotive repair, and spare parts manufacturing in Nigeria (e.g., designing components for vehicles, agricultural machinery like tractors or palm oil processing machines), CAD is vital. Designers use pictorial views to illustrate machine parts, assembly instructions, or product designs. Auxiliary views are essential for accurately manufacturing components with inclined surfaces, such as brackets, cams, or engine parts, ensuring they fit and function correctly. The true shape of a drilled hole on an inclined surface, for instance, requires an auxiliary view for correct setting on a drilling machine.
3. Product Design and Local Innovation: Nigerian entrepreneurs and product designers use CAD to develop new products, from furniture to consumer goods. Pictorial views allow them to present realistic prototypes and explore different design aesthetics quickly. Auxiliary views ensure the manufacturability of intricate parts, especially those produced through local artisans or small-scale industries. For example, designing a unique chair with ergonomically angled backrests or a solar panel mounting frame might require auxiliary views to verify angles and material cuts for local fabrication.
8. Differentiation, Remediation and Extension 8.1 Differentiation Strategies Group Work: Create mixed-ability groups where stronger students can support struggling ones. Assign specific roles within the group (e.g., one operates CAD, another verifies dimensions, a third checks commands).
Varied Task Complexity: Provide a range of objects for practice, from very simple blocks to more complex solids with multiple inclined surfaces, allowing