CAD Presentation and Plotting

≈ 40 min

CAD Presentation and Plotting

CAPS requires a CAD presentation drawing as part of the Grade 12 PAT. The conventions are identical to instrument work — CAD changes the tool, not the standard.

Layers. Put visible outlines, hidden detail, centre lines, dimensions, hatching and text on separate layers, each with its own line type and weight. Layers are what let you plot a clean drawing, turn off dimensions for a presentation view, or correct all centre lines at once.

Draw at full size, plot to scale. Model the object 1:1 in CAD and apply the scale when plotting. Drawing at a scaled size means every dimension must be scaled by hand, and the model no longer matches the real object.

Plot preflight. Before plotting: correct scale, line weights that will actually print (very thin lines can vanish), the title block complete, and the projection symbol present. Check a print, not just the screen.

Worked example. A drawing that looks correct on screen can plot with hidden-detail dashes so fine they disappear, turning hidden edges into missing ones. Line weight is a plotting property, not a screen appearance.

Core checkpoint: CAD does not relax any convention. Model 1:1, organise by layer, and check a real print.

At what size should an object be modelled in CAD?

Full size (1:1), with the scale applied when plotting.

At the plotting scale, so it fits the sheet.

At whatever size is convenient on screen.

At half size, then doubled when plotted.

What is the main purpose of using layers in a CAD drawing?

To group elements by type so line weights, visibility and edits can be controlled together.

To make the file smaller.

To let several people draw at once.

To allow colour printing.

Why must a CAD drawing be checked as a print rather than on screen?

Line weights, dash spacing and text size differ between screen and plotter, so very fine lines can vanish on paper.

Because screens display the wrong scale.

Because the title block does not appear on screen.

It need not be — the screen is authoritative.

Which conventions are relaxed when a drawing is produced in CAD rather than by instrument?

None — CAD changes the tool, not the standard.

Line types may be simplified.

The projection symbol is not required.

Dimensions may be omitted since the model holds them.