: Formsprutning vs Additiv tillverkning

This study explores the possibility of replacing plastic parts previously injection-moulded with components produced using additive manufacturing, also known as 3D printing. The focus is on an actual case at SAAB Training and Simulation in Huskvarna. The background to the study lies in the difficulties that arise when injection moulding tools are missing, are in poor condition, or simply incompatible with current machines, making it too expensive to recreate such parts for small batches of spare components. The study is based on an actual need for a spare part, which is replacing an adapter for a so-called “tracer light unit” in an older simulation system. The aim of the study is to identify which materials and manufacturing methods within the additive manufacturing field that can produce parts with equal or better performance compared to the original injection-moulded ones, ensuring the product still works properly, even when made using a different material and method compared to the originally used. A special focus is placed on finding techniques that minimise anisotropy, meaning variations in material properties depending on the direction of stress, which is a common issue with some 3D printing methods. The study also looks at whether these alternatives meet functional requirements, particularly in terms of strength, tolerances, and fit. The work combined both theory and practice, including literature reviews, interviews, and practical testing. Screening tests were conducted on a range of alternatives, leading to two additive manufacturing techniques that were eventually tested in SAAB’s own product qualification process. These tests exposed the candidate parts to environments and load cases similar to those seen in real-world customer use. Results show that, in this particular case, a 3D-printed component can directly replace a previously injection-moulded part, provided that the right material and printing method are chosen. Among the tested options, one specific combination met all strength requirements. All parts showed an acceptable fit, even though a few fell outside the set tolerance limits for the adapter. The tests indicated that 3D-printed components can meet both strength and geometric requirements. Additionally, the study found that some additive methods can produce components with relatively isotropic properties, meaning directional effects are limited and manageable. The conclusion is that, for this case and likely in other similar ones, additive manufacturing is a technically and financially workable alternative to injection moulding, especially for spare parts in batches with limited size. However, the study also highlights the importance of considering properties like fatigue strength when choosing material and method for a part, as these characteristics can be hard to predict without physical testing or robust data. For future work, further testing and development of simulation methods is recommended, as these could potentially reduce the need for physical trials.