How 3D Printing Works — FDM and MSLA Explained

3D printing — technically additive manufacturing — works by building an object layer by layer from a digital model, rather than machining or casting it. But how does this actually work in practice?

The Common Foundation: From Digital Model to Layers

Every print starts with a 3D model (an STL or STEP file). Slicer software breaks this down into thin horizontal layers and plans the path of the print head or light source for each one. The machine then executes this layer-by-layer recipe, working from the bottom up.

FDM — Fused Deposition Modeling

FDM (Fused Deposition Modeling) is the most widely used process. The machine melts a plastic filament through a heated nozzle and deposits it point by point onto the current layer, where it solidifies instantly. The next layer builds on top of that. It’s ideal for robust, load-bearing, functional parts, with a wide range of materials available (PLA, PETG, ABS, nylon, and their composites).

MSLA — Photopolymer Resin Printing

MSLA (Masked Stereolithography) cures liquid photosensitive resin using UV light projected through an LCD mask, hardening entire layers at once. It’s characterized by extremely fine detail and smooth surfaces, making it the best choice for small, highly detailed parts, models, and display pieces.

Which One, and When?

• FDM: load-bearing, functional parts, prototypes, small batches
• MSLA: fine detail, smooth surface, small and aesthetic parts
• Many projects are best solved with a combination of both

Choosing the right technology and material depends on the part’s function, load, and desired surface finish — this is exactly what engineering consultation is for, before anything gets manufactured.