Extrude and Revolve Skills

Overview

In this lesson, students practice building 3D parts in OnShape by extruding and revolving sketches. They will connect the geometry of angles and triangle-based shapes to real CAD operations, using precise measurements and repeatable steps.

Learning intentions

Students will be able to:

• WALT create a 3D solid by extruding a 2D sketch in OnShape.
• WALT create a 3D solid by revolving a sketch around an axis.
• WALT use angle and side measurements from diagrams to justify whether a triangle construction is unique, multiple, or impossible.
• WALT explain how slicing/sections reveal 2D shapes from 3D solids.

Success criteria

Students can:

• I can extrude a sketch to the correct depth and confirm the preview matches my intent.
• I can revolve a sketch around a chosen axis and produce a clean, watertight solid.
• I can state which given measures would determine exactly one triangle, more than one triangle, or no triangle.
• I can predict the 2D cross-section shape produced when a plane slices a 3D solid.

Curriculum links

• Geometry — draw and reason about triangles from given measures (constructability: unique vs more than one vs none).
• Geometry — describe 2D figures resulting from slicing 3D figures (plane sections).
• Geometry — solve real-world and mathematical problems involving area and volume of objects composed of triangles and quadrilaterals.
• Geometry — solve problems involving scale drawings (using proportional lengths).

Lesson structure (45 minutes)

1. 0–5 min · Hook (Show + prompt). Teacher displays two simple CAD previews: one made with an extrusion and one with a revolution, with a faint outline of the 2D profile. Students turn-and-talk: “Which tool do you think was used and why?”

2. 5–12 min · Mini direct teach (OnShape focus). Teacher demonstrates extrude and revolve using a single example profile, naming key decisions: sketch plane, profile selection, direction/extent for extrude, and axis + 360° vs partial angle for revolve. Students follow along with their cursor on a practice file, pointing out where they would click to select the profile and axis.

3. 12–18 min · Geometry quick check (triangle certainty). Teacher shows three “given measures” situations as card prompts (no CAD yet):

• Situation A: three angles sum to 180 with all angles given.
• Situation B: two angles and a side (not including whether the side is included) using a diagram.
• Situation C: two sides and a third side that clearly violates triangle inequality. Students write a quick answer: unique triangle, more than one triangle, or no triangle, and one sentence justification.

4. 18–30 min · Guided practice 1: Extrude part. Teacher assigns a short “Extrude Starter” task: students create a 2D sketch profile (provided dimensions on their worksheet), then extrude to a specified depth (e.g., a 3D keycap or bracket-like block). Students complete the steps in OnShape and capture a screenshot showing dimensions and the completed solid.

5. 30–38 min · Guided practice 2: Revolve part. Teacher models how to revolve a profile around an axis, emphasizing common mistakes: axis placement, selecting the correct profile region, and choosing the correct angle/extent. Students produce a second solid by revolving their profile (or a similar provided one) to create a symmetric 3D object (e.g., a vase-like shape or lamp shade silhouette).

6. 38–43 min · Section reasoning (connect to geometry). Teacher draws a simple cutting plane across each student’s final shape conceptually (not requiring exact machining). Students answer: “What 2D figure would you see at the slice—triangle, rectangle, trapezoid, or circle sector/segment?” They do this with a quick hand sketch.

7. 43–45 min · Exit ticket (2 questions). Students submit:

• Q1: One-sentence explanation of the difference between extrude vs revolve, including the role of the axis for revolve.
• Q2: For one triangle-card from earlier, state “unique / more than one / no triangle” and why.

Resources

• Chromebooks or laptops with OnShape access
• Teacher demo file (prepared extrude + revolve examples)
• Printed “Extrude Starter” and “Revolve Starter” worksheets with dimensions
• Pencil, eraser, graph paper or mini sketch paper
• Screenshot instructions (one image upload or share link method)
• Triangle card prompts (printed or projected)

Assessment

• Formative during practice: teacher checks for correct profile selection and correct extrude/revolve settings before students finalize.
• Formative geometry check: triangle certainty responses collected mid-lesson for quick targeting.
• Exit ticket: evaluates both tool understanding and geometry reasoning (constructability + section prediction).

Differentiation

• Support:
• Provide step-by-step visuals on the worksheet (Sketch → Select profile → Extrude/Revolve settings → Verify solid).
• Sentence starters: “I chose extrude because…”, “The revolve axis must be…”, “This triangle is unique/more than one because…”
• Offer a “checkpoints” timer where students must show their screen before continuing.
• Extension:
• Early finishers try changing extent: extrude “to a specified distance” vs “through all,” and revolve “partial angle” to create a notch or segment.
• EAL/SEN:
• Use consistent vocabulary on the board (profile, axis, extent, direction).
• Allow verbal justification for the triangle/section questions before writing, then have them write a short final sentence.