Manufacturing Process Fundamentals
Core concepts
Manufacturing process fundamentals covers how a design becomes a physical part: the major process families (casting, forming, machining, joining, additive, and surface treatment), their capabilities, and the tradeoffs that drive process selection. A candidate should be able to match a feature or material to a plausible process and explain why alternatives are inferior.
What to know cold
- Casting (sand, die, investment): good for complex internal geometry; watch shrinkage allowance and draft angle.
- Forming (rolling, forging, stamping, extrusion): strong grain structure, low waste, but tooling cost is high and volumes must justify it.
- Machining (turning, milling, drilling): tight tolerance and fine finish, but slower and more material waste.
- Joining (welding, brazing, adhesive, fasteners): affects heat-affected zones and inspection requirements.
- Additive: design freedom and low tooling, but anisotropic properties and post-processing.
Traps in questions
Questions often test draft angle (needed for removal from molds), shrinkage allowance (patterns made oversized), and minimum wall thickness by process. Another common trap: confusing a process's capability tolerance with a typical tolerance. Do not assume the tightest published number is economic.
Rule of thumb
For process selection: if annual volume is low and geometry complex, favor casting or additive; if volume is high and geometry simple, favor forming or die casting; if tolerance dominates, favor machining regardless of volume. A useful sanity check: doubling precision roughly multiplies cost, so specify the loosest tolerance that functions.
Worked example
A bracket needs 50,000 units/year, moderate complexity, ±0.5 mm tolerance. Die casting fits volume and complexity; sand casting is too slow per unit, and machining from billet wastes material at this volume.