There are many ways to 3D print, but three technologies dominate: FDM, SLA and SLS. They all build parts layer by layer, but in completely different ways — and the results differ in surface finish, strength and price. Here we walk through how each works and when to choose which.
FDM — melted plastic filament
FDM (Fused Deposition Modeling) melts a plastic filament and lays it down layer by layer through a nozzle. It's the most common technology — both at home and in industry.
- Surface finish: Visible layer lines. Smoother with thinner layers, but rarely perfectly smooth straight off the printer.
- Strength: Good, especially within the plane of the layers. A little weaker between layers. Materials like PETG and ABS give tough, functional parts.
- Cost: Lowest of the three. Cheap materials and a fast process for simpler geometries.
- Best for: Prototypes, fixtures, enclosures, spare parts and functional parts where an exact finish isn't critical.
SLA — resin cured with light
SLA (and the closely related DLP technology) uses liquid resin cured point by point with UV light. The result is highly detailed.
- Surface finish: Excellent. Smooth surfaces and sharp detail, with almost no visible layers.
- Strength: Varies with the resin. Standard resin is often more brittle than FDM plastic, but there are tough, durable specialty resins.
- Cost: Higher material and post-processing cost. Parts must be washed and post-cured.
- Best for: Figurines, jewellery, dental, small detailed parts and visual prototypes.
SLS — powder sintered with a laser
SLS (Selective Laser Sintering) uses a laser to fuse nylon powder together. The surrounding powder supports the part, so no support material is needed.
- Surface finish: Matte and slightly grainy, even all around with no support marks.
- Strength: Very good and consistent in all directions. Well suited to end-use products.
- Cost: Higher, but efficient for several parts at once since the whole build volume can be filled.
- Best for: Complex geometries, moving parts, small batches and functional end-use parts.
How to choose the right one
Think about what the part needs to do:
- Need a cheap, functional part fast? Choose FDM.
- Want maximum detail and a smooth surface? Choose SLA.
- Need strong, complex geometry without supports? Choose SLS.
The material matters at least as much as the technology — see PLA vs PETG for a concrete comparison, or start with the basics in What is 3D printing?.
Summary
FDM is affordable and functional, SLA gives the finest finish and SLS gives strong parts with free geometry. Unsure what suits your part? Upload your model and get a quote — we'll help you pick the right technology and material.