Optimizing projects with both FDM and SLA 3D printing

Not everyone is aware that FDM and SLA are complementary technologies that when used together can be highly beneficial for your AM projects. In product development, SLA 3D printing is ideal for detailed concept models or functional prototypes. In manufacturing, both technologies can be used to create jigs, fixtures and other tooling. FDM is usually preferred for large, simple parts, while SLA is better suited for complex jigs, highly accurate tooling and molds. For businesses, it is crucial to understand the fundamental differences in print quality, materials, applications, workflow, speed and cost in order to optimize projects.

Comparing FDM and SLA 3D Printing

At the consumer level, FDM 3D printing remains the most widely used technology. FDM 3D printers work by extruding thermoplastics layer by layer on the build plate, until the part is produced. On the other hand, SLA is more widely used in professional sectors. It uses a laser to cure resin into hardened plastic, a process called photopolymerization. While FDM produces a mechanical bond between layers, SLA creates chemical bonds by cross-linking photopolymers across each layer. The result is a fully dense part that is water and airtight and also ideal for many engineering and manufacturing applications where material properties matter. SLA parts also provide high degrees of lateral strength, resulting in isotropic parts. In terms of precision and accuracy, FDM technology still struggles with very fine detail, especially for complex parts.

FDM 3D printed part (left) and SLA 3D printed part (right). In terms of geometric complexity, SLA technology is more precise and accurate | Credits: Formlabs

As you may know, once the part has been 3D printed, the final step in the 3D printing workflow is post-processing. During this step, SLA parts always need to be rinsed in isopropyl alcohol (IPA) or alternative solvents to remove any uncured resin from their surface. Some also require post-curing, which provides the part with higher strength and stability. The FDM process does not require cleaning. Additionally, both FDM and SLA parts can be machined, primed, painted and assembled for specific applications or finishes.