Injection-molded and 3D-printed Polymeric Parts: A Theoretical Approach to Mechanical Performance and Processing Costs

Introduction: This study provides a comparative analysis of two manufacturing methods for Polypropylene (PP): injection molding and Fused Deposition Modeling (FDM) 3D printing. We correlate the mechanical and thermal properties of both processes with a preliminary economic analysis to help guide the selection of the most suitable method for various industrial applications. Methods: The analysis was based on technical data provided by manufacturers, without conducting laboratory tests. Key properties such as tensile strength, flexural strength, impact resistance, and softening temperature were evaluated. The data was organized into graphs and tables to facilitate a direct comparison between the two processes. Results: Injection-molded polypropylene exhibited significantly superior mechanical and thermal performance. This is attributed to the higher structural density and molecular orientation achieved during the process. In contrast, 3D-printed polypropylene showed lower mechanical performance, primarily due to the presence of interlaminar discontinuities. However, it demonstrated key advantages in geometric flexibility and lower initial cost, making it suitable for lowvolume production and rapid prototyping. The preliminary economic analysis (taking into account the Brazilian scenario) revealed that injection molding requires a high initial investment, particularly for the mold fabrication, but it becomes more cost-effective in large-scale production due to a drastic reduction in unit cost. 3D printing, on the other hand, is ideal for ondemand applications and the production of unique or low-volume parts, where customization and agility are more critical than mechanical performance. discussion: The choice between these two manufacturing methods should not be based solely on individual performance metrics or cost. A systemic analysis is necessary, one that considers the product's life cycle, production scale, and the specific functional requirements of each application. The findings highlight a trade-off: superior performance and low unit cost at high volume with injection molding versus high design flexibility and low initial cost for low-volume production with 3D printing. Discussion: The choice between these two manufacturing methods should not be based solely on individual performance metrics or cost. A systemic analysis is necessary, one that considers the product's life cycle, production scale, and the specific functional requirements of each application. The findings highlight a trade-off: superior performance and low unit cost at high volume with injection molding versus high design flexibility and low initial cost for low-volume production with 3D printing. Conclusion: This study concludes that the optimal choice between injection molding and 3D Printing for polypropylene depends on a holistic evaluation of both technical and economic factors. The research provides a foundation for more informed decisions making in product engineering by considering the structural performance, economic viability, and the practical application needs of each process.