Manufacturing: Process Selection, Parameters, and Post-Processing
What the Manufacturing domain tests
The Manufacturing domain covers how a design becomes a built part. Candidates must understand the main additive families and their trade-offs: powder bed fusion, directed energy deposition, material extrusion, vat photopolymerization, binder jetting, and sheet lamination. Know how laser power, scan speed, hatch spacing, and layer thickness interact to control energy density and defect formation. You should recognize common defects, including lack-of-fusion porosity from insufficient energy, keyhole porosity from excess energy, balling, delamination, warping from residual stress, and spatter. Support removal, heat treatment, hot isostatic pressing, machining allowances, and surface finishing are all part of the manufacturing chain and often appear as answer choices.
Traps to watch
A frequent trap is treating a parameter change as monotonic: raising laser power does not always improve density because too much energy causes keyholing. Another trap is confusing the cause of porosity: irregular, elongated pores suggest lack of fusion, while round pores suggest gas or keyhole effects. Questions may also test powder reuse and contamination, where the correct answer is usually about qualifying powder rather than assuming unlimited reuse. Watch for answers that ignore post-processing: an as-built surface may fail fatigue requirements even if the geometry is correct. Also expect distinctions between build rate and resolution, which trade off against each other.
Worked example
A coupon shows irregular, unmelted powder particles at layer boundaries. Rule of thumb: this is lack-of-fusion porosity, so increase volumetric energy density by raising power, slowing scan speed, or reducing hatch spacing or layer thickness. If instead the pores are round and centered in the melt track, suspect keyholing and reduce energy. The exam answer should name the defect signature first, then the parameter direction, not just a number.
Exam strategy
Anchor each question to the defect signature or the manufacturing step. Eliminate answers that ignore post-processing or that assume a parameter change is always beneficial.