ENGR10006 Chap.4 CAD Modelling, Assembly and Technical Drawings
CAD Modelling, Assembly and Technical Drawings
The speaker stream builds its driver and enclosure in SolidWorks, and robot teams use the same skills for their gripper paddles. This chapter follows the workflow the workshops teach: choose a plane at the origin, sketch in 2D, fully constrain the sketch, then apply a feature. It compares extrude, extruded cut, revolve, circular pattern, mirror and fillet, explains parametric editing, and lists the six assembly mates.
It then reads the prototype speaker drawings, with their title-block rules and scales from 10:1 to 1:2, before moving to manufacture: preparing DXF files for the laser cutter with red cut lines and black engraving, and the volume and size limits on 3D-printed parts. Worked examples read a drawing at its scale and prepare a laser file, and practice items test sketch planes and mates in the style of the speaker practice quiz.
What this chapter covers
- 01
Planes, origin and MMGS units
- 02
Dimensional, algebraic and geometric constraints
- 03
Extrude, cut and revolve features
- 04
Circular pattern, mirror and fillet
- 05
Six assembly mates
- 06
Drawing scales and title blocks
- 07
Laser cutting colour rules
- 08
3D printing limits
Worked example · free
Reading drawing scales before preparing a laser cut file
- +1At 10:1 the printed insert edge is ten times its true size, so 80 mm on paper is the true 8 mm edge; at 1:2 the printed back panel is half size, so 78.1 mm on paper is the true 156.2 mm.
- +1The title block says do not scale the drawing: the dimension text gives true sizes, so the file must use 8 mm and 156.2 mm and be exported at true size as a DXF.
- +1In CorelDRAW, join the panel outline into one closed object and set it to red, RGB 255 0 0, at hairline width so it is cut rather than engraved.
Key terms
- Parametric modelling
- Modelling in which changing a dimension value updates the shape without redrawing.
- Fully defined sketch
- A sketch whose lines are all fixed by dimensions and relations, shown when every line turns black.
- Extruded cut
- A feature that removes material by sweeping a sketch through a part, for example Through All.
- Revolve
- A feature that sweeps a profile around an axis, used for the speaker cone.
- Coincident mate
- An assembly relation that makes faces, edges or points touch and lie in one plane.
- Concentric mate
- An assembly relation that aligns the axes of cylindrical features, as for a bolt in a hole.
- Drawing scale
- The ratio between a feature's size on the sheet and its true size, such as 10:1 or 1:2.
- DXF file
- The 2D drawing format sent to the laser cutter.
CAD Modelling, Assembly and Technical Drawings FAQ
Why does the sketch plane matter in SolidWorks?
The plane sets the direction of every feature built from the sketch. A cut through a disc must be sketched on a plane parallel to its faces, and the back-panel exercise only mirrors correctly if the quarter sketch sits on the Front Plane with its corner at the origin.
What do the colours mean on the laser cutter?
In the CorelDRAW workflow, red outlines set to RGB 255 0 0 at hairline width are cut, while black outlines set to RGB 0 0 0 are engraved. The machine engraves first, from bottom to top, and then cuts, so engraving is finished before parts drop free.
What size limits apply to 3D-printed speaker parts?
Each custom printed component must not exceed 120 cubic centimetres and must fit within 50 by 50 by 100 mm, and the specification notes these are separate limits. Prints must finish in under 12 hours on a Prusa MK4S using 1.75 mm PLA.
Which drawings must the speaker report include?
The report requirements ask for multiview projections of the chassis, speaker and enclosure sub-assemblies, choosing the view type that shows each best and including every relevant dimension, together with an explanation of the CAD techniques used and drawings of the custom enclosure.
Assessment move
Practise the workflow on paper before you open the software: for each part, write the plane, the 2D sketch, the constraints and the feature you will use, then check that the order would still work if a dimension changed. Redo the workshop exercises from a blank file without the handout and time yourself, because milestone tasks are done in class.
For assemblies, list each joint and name its mate before applying it, and count mates for simple panel boxes so quiz questions about them become routine. For drawings, read every title block and write down the scale and what the dimension text means at that scale.
Before visiting the laser cutter, prepare a DXF at true size, join curves, set colours and arrange parts to waste as little of the single 600 by 300 mm sheet as possible. Keep screenshots of features and drawings as you go, because the report asks you to explain the techniques you used.
Finally, compare your finished parts against the prototype drawings dimension by dimension before cutting, since a cut panel cannot be edited the way a sketch can. Keep each part file named consistently so the assembly opens cleanly on the lab computers.
