FFF or SLA — which technology should you choose?

FFF/FDM builds with melted filament. SLA cures successive sections of liquid resin. Both create parts in layers, but they differ in finish, material behaviour, post-processing and typical use.

FFF/FDM — practical prototypes and working parts

An FFF nozzle deposits paths of thermoplastic. The process is a strong fit for housings, brackets, fixtures, larger prototypes and many short-series functional parts.

Its strengths include a broad material range, practical build sizes and control over internal structure. Visible layer paths are natural, and strong overhangs may need supports that leave marks.

SLA — fine detail and smoother surfaces

SLA uses light to cure liquid resin. It reproduces small lettering, textures and complex surfaces, making it useful for presentation models, miniatures, masters and small detailed parts.

The part must be washed, removed from supports and post-cured. Performance depends on the selected resin, and not every resin is intended for impact, temperature or sustained load.

Side-by-side comparison

Criterion	FFF/FDM	SLA
Surface	Visible paths and layers	Usually smoother and more detailed
Typical use	Enclosures, fixtures, prototypes	Miniatures, masters, detailed visual models
Material	Thermoplastics and composites	Resins with defined property profiles
Supports	Mainly under overhangs	Usually integral to build preparation
Finishing	Support removal, optional sanding	Washing, support removal and post-curing
Scale	Practical for many larger geometries	Often chosen for smaller detailed models

Choose FFF when you prioritise

• a functional part or working prototype,
• larger dimensions,
• a broad thermoplastic choice,
• sensible short-series economics,
• straightforward drilling, inserts or mechanical finishing.

Choose SLA when you prioritise

• very fine features and textures,
• a smooth surface on a small model,
• intricate compact geometry,
• a presentation, master or casting pattern,
• a resin verified for the requirement.

What changes the result most

Orientation strongly affects both processes. It determines support locations, surface appearance, time and part behaviour. SLA also requires drainage from hollow volumes, while FFF needs load direction considered relative to layer bonds.

Compare the complete workflow — material, orientation, support, finishing and inspection — rather than machine labels alone.

What if the project has mixed needs?

A concept can be tested quickly in FFF and later produced as a detailed presentation model in SLA. An enclosure may use filament while a small master uses resin. The process is a tool for the function, not a declaration for the whole product.

The best answer to “FFF or SLA?” starts with: what must this part do after printing?