Adapting Machining Strategies for the Sustainable Fabrication of Titanium Implants Using AHP and PROMETHEE

This study proposes a sustainability-oriented optimization framework for the manufacturing of titanium ASTM F67 implants, integrating economic, environmental, and social indicators through a combined Analytic Hierarchy Process (AHP) and Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE II) approach. Two non-conventional machining technologies wire electrical discharge machining (WEDM) and abrasive waterjet cutting are analyzed, combined with milling and drilling operations to simulate 84 distinct manufacturing routes under varying demand scenarios (low, regular, high). Sustainability indicators, including energy consumption, CO₂ equivalent emissions, raw material utilization (titanium volume), and tool waste (carbide), are quantified and normalized. These are integrated alongside cost and operational safety metrics into the multicriteria decision-making framework. Energy consumption differs by up to 70% between the most and least efficient routes, while titanium utilization varies by 25%, directly impacting material costs and environmental footprint. The framework enables flexible weighting of criteria, accommodating different market or policy priorities. Results demonstrate that waterjet cutting combined with milling reduces energy consumption by up to 40% and titanium waste by 25% compared to WEDM routes under regular demand conditions, making it the most sustainable choice in such scenarios. Conversely, WEDM routes outperform in high-demand scenarios, achieving up to 35% higher productivity, despite elevated energy use. The framework offers a robust and adaptable decision-support tool, applicable not only to the biomedical sector but also scalable to other industries seeking to balance productivity and sustainability goals. This study delivers practical guidance for manufacturers and insights for policymakers aiming to promote sustainable manufacturing practices.