CAD Modelling Questions

Below are questions to test your knowledge and understanding of CAD modelling.

Before you continue, make sure you have studied the theory by clicking here.

Questions

Question 1

Question 2

Question 3

Question 4

Question 1

Freeform modelling is often used to produce animated characters. a. Explain, giving two reasons, why freeform modelling is used to create animated characters. (4 marks)

Answers

a. (Answers to explain questions must have a cause and an effect)

Freeform modelling allows the creation of organic designs which would be well-suited to character design
Polygon meshes used within freeform modelling allow for manipulation of points/edges/ faces to provide a greater level of detail when editing features of characters
Freeform modelling provides designers with creative freedom to manipulate and tweak the model

Tools such as mirror help with modelling characters to make symmetrical features

Question 2

A dog treat toy is shown below.a. Describe, using 3D CAD modelling techniques, how you would model component A. You may use sketches and annotate the model images to support your answer.

Stage 1 (4 marks)
Stage 2 (2 marks)
Stage 3 (2 marks)
Stage 4 (4 marks)

Answers

a.Stage 1

Sketch an ellipse profile with a major axis of 100 mm and a minor axis of 88mm. Offset a workplane 40mm and sketch a circle profile 100mm (1 mark)

Use the loft command to connect the ellipse to the circle (1 mark)
Fillet the bottom edge of the shape to a radius of 30mm (1 mark)
Sketch a circle to 95mm on the top surface and extrude to 4mm (1 mark)

Stage 2

Turn on a middle plane and sketch a circle with a diameter of 1 (or R0.5) in the correct position shown (1 mark)
Using the helix command, set the pitch to 3 mm with one revolution (1 mark)

Stage 3

Sketch a circle profile at 18mm and 25mm from the centre. Turn on a perpendicular workplane and sketch the path at radius 50mm (1 mark)
Extrude subtract along a path (1 mark)

Stage 4

Sketch a rectangle 20x4 on a Pitch Circle Diameter of 70 (1 mark)
Offset a workplane 20mm and sketch a rectangular profile 18x2. Use the loft command (1 mark)
Create irregular fillets of 0.5mm to 1 mm applied to all four corners (1 mark)
Radial array, the blade features 6 times around the centre axis (1 mark)

Question 3

Top-down modelling and surface modelling were used to create components B and C, as shown.

a. Describe two ways top‑down modelling was used to support the production of component B. (2 marks)b. Explain, giving two reasons, why surface modelling is a suitable modelling technique for component C. (2 marks)

Answers

Component B could be modelled using the projected geometry from the rim or ridge of component A to ensure an accurate fit
The subtracted helix on component B could be taken from the geometry of component A to ensure an accurate fit
Component C could be made to fit the diameter and notches shown on component B, ensuring an accurate fit

Surface modelling allows the designer more creative freedom, as polygon meshes can be applied
It allows for the creation of organic shapes, eg the inclusion of the finger indents
The use of thicken/offset ensures a uniform wall thickness that conforms to the organic form
A thin wall thickness is used in the product; therefore, surface modelling is a suitable technique

Question 4

A CAD model of a siphon coffee maker is shown. The ‘stand’ was made using 3D CAD solid modelling techniques, and the ‘beaker’ using 3D CAD surface modelling techniques. a. Describe the 3D CAD solid modelling techniques used to create the stand. You may use sketches to support your answer. (7 marks)

The grip on the stand was created using morphing (freeform modelling) techniques.b. Describe, using morphing (freeform modelling) techniques, how the grip was created. Stage 1 has been completed for you. You may use sketches to support your answer. (4 marks)
Stage 1: Offset the geometry of the top section of the stand and use this to create a new solid.

c. Describe the 3D CAD surface modelling techniques used to create the beaker. Refer to dimensions in your answer. You may use sketches to support your answer. (6 marks)

Answers

Sketch for top feature with the dimensions (R30, R20, 10, 15mm) and extrude 10mm (1 mark)
Profile for stem (15, 10, R5, R4) and positioned 2mm from the back of the top feature (1 mark)
Path for stem with all dimensions (30, 117, R14, 116, 39, R12, 30) (1 mark)
Extrude along a path with an 8-degree taper applied (1 mark)
Profile for base feature with all dimensions (120 degree, R69) and path profile with all dimensions (rectangle 28, 4xR4) (1 mark)
Extrude along a path (1 mark)
All 4mm fillets applied to the top piece and base (1 mark)

Stage 2: Create a free form with 12 × 6 mesh
Stage 3: Apply an axis of symmetry
Stage 4: Edit the form using points/edges/faces to create the desired form
Stage 5: Convert the form into a solid

Sketch the profile shown below and revolve the bottom profile of the beaker around the centre axis (1 mark)
Offset a plane 75mm from the circle of a 120 and sketch an ellipse profile with major axis 90 and minor axis 78 (1 mark)
Loft the circle and ellipse together (1 mark)
Sketch the top surface to the dimensions shown below and surface revolve 360 degrees around the centre axis (1 mark)
Fillet R7 applied between the lofted and revolved sections (1 Mark)
Thicken the model to 2mm (1 mark)

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