Design for Additive Manufacturing: Design Principles and Constraints
What the Design domain tests
The Design domain asks whether you can shape a part so that it can be built additively without losing function. Candidates must understand design freedom versus process constraints, orientation-dependent features, self-supporting geometry, minimum feature size, wall thickness, overhang angle, anisotropy, and the trade-off between part consolidation and inspectability. You should also know how lattices, topology optimization, and generative design differ: topology optimization removes material from a defined design space under loads, generative design explores many candidate solutions against goals, and lattice design replaces solid regions with repeating unit cells.
Traps to watch
Questions often present a design that is printable but not functional, or functional but not printable. Watch for overhang rules quoted without a process context: a 45-degree self-support threshold is a rule of thumb for laser powder bed fusion, not a universal law. Another trap is confusing minimum wall thickness with minimum feature size; thin walls may print while thin pins may not survive depowdering. Orientation traps are common: a hole designed horizontally becomes a teardrop, and a flat top face may need support unless chamfered. Also expect questions about anisotropy, where build-direction properties differ, and about part consolidation that removes fasteners but creates inaccessible internal channels.
Worked example
A bracket has a horizontal circular cooling channel of 6 mm diameter. Rule of thumb: for powder bed fusion, keep unsupported horizontal holes at or below roughly 8 mm, or redesign as a teardrop with a 45-degree roof. Because 6 mm is under the threshold, the channel can print without internal support, but the designer should still add a drain path for trapped powder. If the channel were 15 mm, the answer is a teardrop or self-supporting diamond section rather than internal supports that cannot be removed.
Exam strategy
Read every design question for the process named, the material, and the orientation. If any is missing, the correct answer usually states the dependency rather than a fixed number.