Transforming subjective expectations into measurable technical specifications for additive manufacturing success.
In the high-stakes world of aerospace and medical additive manufacturing, ambiguity is the enemy of efficiency. When a design engineer specifies that a part should have a "high-quality surface," they might be envisioning an injection-molded look, while the print operator considers a standard matte finish "high quality" for the chosen material. This discrepancy often results in rejected batches, wasted material, and strained relationships between departments or vendors.
Strong acceptance criteria are built on three pillars: Measurability, Repeatability, and Procedural Clarity. If a requirement cannot be measured with a calibrated tool, it likely belongs in a subjective category rather than a mandatory technical acceptance document. Compare these common phrases used in procurement:
| Weak (Subjective) | Strong (Objective) |
|---|---|
| "The part must be durable enough for industrial use." | "The component must withstand a tensile load of 450N along the Z-axis without delamination." |
| "Surface should be free of major print lines." | "Primary faces must exhibit a surface roughness (Ra) not exceeding 6.3 µm, measured per ISO 4287." |
| "Dimensions must be as close to CAD as possible." | "Outer dimensions must maintain a tolerance of +0.0/-0.15mm relative to the H7 bore specification." |
To transition your documentation to a professional standard, every sentence should follow a strict logic. Instead of describing what the part is, describe how it behaves under specific testing conditions. Use third-person present-tense verbs to state facts: "The lattice structure supports the internal cavity during the sintering process." Use imperative verbs for the inspection stage: "Verify the internal diameter using a calibrated pin gauge."
A final audit of your criteria should ask: Could two different inspectors, using the same tools in different facilities, arrive at the same conclusion? If the answer is no, your language is still too weak for production-ready additive manufacturing. Refine the language until the measurement method and the pass/fail threshold are indisputable.