Fig. 24 shows a CAD model of a desk lamp displayed on a computer screen. The product is manufactured in large quantities using industrial processes. The cho...

(a) Two advantages of using CAD modelling instead of making a physical model during the developing stage:

1. Changes can be made quickly without rebuilding a physical model [1]. If a proportion, feature, or dimension needs adjustment, the designer modifies the digital model immediately. A physical model would need to be remade from scratch or extensively reworked, which takes more time.
2. The model can be viewed from any angle and rendered with realistic materials and colours [1]. CAD software allows the designer to rotate, zoom, and apply photorealistic surface finishes to visualise exactly how the lamp will appear, without consuming any physical materials or producing waste.

Other valid advantages include: dimensions can be checked accurately using built-in measuring tools; the digital file can be shared electronically with clients or manufacturers for feedback; and no material cost or waste is produced during virtual modelling.

(b) A CAD model allows a designer to refine the design specification because the designer can test features such as proportions, ergonomics, and appearance on screen, identifying changes needed before committing to a physical prototype [1]. For example, if the lamp shade appears too small relative to the base in the CAD view, the specification can be updated with revised dimensions. This iterative on-screen testing ensures the specification is realistic, complete, and achievable before any materials are purchased.

(c) One method a designer could use to produce a physical prototype directly from the CAD model is 3D printing (also called rapid prototyping or additive manufacturing) [1]. The CAD file is exported in a suitable format (such as STL) and sent to a 3D printer, which builds up the model layer by layer from plastic filament or resin, faithfully reproducing the digital geometry. Other valid methods include CNC machining and laser cutting.