By the end of this topic, you should be able to...
construct and interpret CAD models suitable for rapid prototyping.
Guiding Question
Why is it necessary for designers to prototype ideas as part of a design process?
💡 Did You Know? Your CAD model looks flawless on screen—then the 3D printer stops halfway through, leaving a spaghetti sculpture of failed plastic, because what renders beautifully doesn't always print successfully.
Why Rapid Prototyping?
Designing for rapid prototyping requires fundamentally different CAD thinking than traditional manufacturing. That elegant cantilever in your model? It needs support structures or it collapses mid-print. Those wall thicknesses that look fine at 1mm? Too thin—the part will warp or shatter. That intricate hollow interior? Impossible to remove support material without destroying it.
Constructing CAD models for additive manufacturing means anticipating physical realities: minimum feature sizes, overhang angles (typically 45° max without supports), bridging distances, part orientation effects on strength, and file mesh quality that prevents gaps or inverted normals. But equally critical—interpreting others' CAD files for printability:
Can you identify why a colleague's STL fails to slice?
Recognize when wall intersections create non-manifold geometry?
Spot where tolerances are too tight for layer resolution?
Professional designers don't just "export to STL and hope"—they engineer models with print physics embedded in every design decision, then troubleshoot failures by reading CAD geometry like diagnosticians reading medical scans.
Case in Point
Open Bionics, which manufactures affordable 3D-printed prosthetic hands for children, designs every CAD component with rapid prototyping constraints: minimum 2mm wall thickness for strength, 45° self-supporting angles to eliminate supports, parametric sizing so files automatically scale across 50+ hand sizes, and deliberate part splits at natural stress lines. Their CAD methodology isn't just smart design—it's the difference between $50,000 traditional prosthetics and $500 printed alternatives that ship in days, not months.
Learning Goals
In this topic, you'll learn to construct print-optimized CAD models, interpret geometric features for additive feasibility, and troubleshoot common rapid prototyping failures—skills that will transform your IA prototypes from expensive trial-and-error into predictable, efficient development.
Linking Questions
When creating physical prototypes, which ergonomic considerations should be taken into account? (A1.1)
To what extent are user-centred research strategies useful to gather feedback on models and prototypes of proposed design solutions? (A2.1)
How do designers use their knowledge of prototyping techniques to ensure effective modelling and prototyping? (A2.2)
Which aspects of material properties can be explored through modelling? (A3.1)
How can information about a proposed structural system, such as a product housing, be gathered using CAD modelling and contribute to the development of a design solution? (A3.2, B3.2)
How effectively can mechanical systems be mocked up and tested using modelling and prototyping? (A3.3, B3.3)
How can effective electronic systems be modelled virtually? (A3.4, B3.4)
How does the development of prototypes inform the choice of manufacturing techniques and production systems for a product? (A4.1, B4.1)
How can modelling and prototyping be used to inform the development of a product following a user-centred design (UCD) strategy? (B1.1)
To what extent is modelling and prototyping essential for inclusive design? (B2.2)
To what extent can the same materials used for modelling and prototyping be used in the material selection of a commercial product? (B3.1)