Background information
900 layers in 3D printing: Apple shows how the Titanium Watch is made
by Martin Jungfer
My first time with resin: how SLA works
27.1.2026
Translation: Patrik Stainbrook
I’ve been 3D printing for a few years now. Now I’m venturing into SLA technology for the first time. I’ll explain exactly how it works right here, part one of an ongoing miniseries.
I’ve used 3D printing to make plenty useful things over the years. Little household helpers, spare parts for appliances and toys for the kids. Doing so, I always used fused deposition modelling (FDM). But I want to try stereolithography (SLA) now, a process that uses synthetic resin.
In this article, I’ll explain what SLA is and how it differs from FDM. This will kick off a small series in which I’ll share my experiences during the process.
How SLA 3D printing works
SLA is the oldest 3D printing process, invented by Chuck Hull in 1983. It also marks the birth of additive manufacturing. To this day, SLA is considered the most precise 3D printing process, ideal for applications where maximum accuracy is required.
The process, also known as resin printing, produces extremely detailed and smooth models. In contrast to FDM printers, which apply molten filament layer by layer, resin printers work with liquid synthetic resin that’s cured by UV light.
The printing process detailed
This is how you print with modern SLA devices:
The resin basin: liquid synthetic resin sits in a transparent basin, which allows UV light to pass through from below. The resin reacts to the radiation and hardens.
UV light source and LCD masking: there’s an LCD screen under the basin that directs the UV light in a targeted manner. It projects the design of each layer into the resin and hardens the desired areas.
Layer by layer, all the way up: after each layer has hardened, the platform rises slightly. Models are built upside down, with new layers applied from the bottom. This process repeats until the print is done.
Post-print: after that’s done, a model gets lifted out of the tank, not ready for use yet. It’ll be covered in uncured resin that has to be washed off – usually with isopropyl alcohol (IPA). The model is then post-exposed in a UV chamber to cure completely and achieve the desired properties.
In the end, you’ll have a model with impressive details and smooth surfaces. This makes resin printing perfect for intricate designs, miniatures and prototypes.
Source: Shutterstock/MarinaGrigorivna
The most important differences between resin and FDM
As an experienced FDM user, I asked myself what the differences even were. Both processes use additive manufacturing, but they differ in several ways:
Print quality and resolution
Resin printers deliver superior quality. With layers up to 0.025 mm in height, they reproduce even the finest details – ideal for miniatures, dental models or jewellery. FDM printers achieve 0.1 mm at best, often leaving behind rough surfaces too.
Print speed and efficiency.
Although resin printers cure entire layers at once, they aren’t necessarily faster. The curing process and elevating the platform between layers takes time, especially with larger models. One advantage: resin printers can make several small objects at the same time without extending the printing time. FDM printers require extra time for each object.
After the print
There’s a clear difference here. With FDM, it’s usually fine to remove the finished structure from your build plate and remove any supports. You’ll have to do more for resin printing:
- Washing: uncured resin has to be removed from your model.
- Second curing: the model will have to fully cure under UV light.
- Removing supports: due to all those fine details, removing support structures often requires more care.
Material and cost considerations
Resin printing is pricier. Resin costs more than filament, and additional materials such as IPA and nitrile gloves only increase expenses. Special resins, say for flexible or robust builds, are even pricier.
Safety and workplace equipment
Safety plays a major role in resin printing. Resin is poisonous, and can damage your skin and respiratory tract. Always remember to work in a well-ventilated environment, wear gloves and handle the material with care. The printing process also requires more space as well as a clean, organised working environment.
My verdict following some research
The differences between FDM and SLA are considerable – especially in terms of print quality and handling. FDM is simple and beginner-friendly, while SLA requires more work post-print and generates higher running costs. On the other hand, it offers significantly higher precision.
I’m particularly concerned about safety and the workplace equipment required. So far, I’ve only printed in my small office, which isn’t well-ventilated. So, for better or worse, I’ll have to move my SLA printer somewhere else. I’ll tell you where that’ll be and which printer I bought in the next article.
Header image: Shutterstock / Stocky boi
Kevin Hofer
Senior Editor
kevin.hofer@digitecgalaxus.chFrom big data to big brother, Cyborgs to Sci-Fi. All aspects of technology and society fascinate me.
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