From Theory to Practice
In the last installment, we uncovered what 3D printing is and why additive manufacturing is so revolutionary. Now that we understand the basic principle of “adding material,” it’s time to look at how it all works in practice. The term “3D printing” actually encompasses a whole family of different technologies, each with its specific advantages and ideal uses. Let’s get acquainted with the most important ones.
How 3D Printing Works
The term “3D printing” actually encompasses a whole family of different technologies, each with its specific advantages, disadvantages, and ideal uses. There isn’t one universal method that’s best for everything; rather, it’s a set of tools from which to choose the right one for a given task. Let’s look at the most important ones.
Fused Deposition Modeling (FDM/FFF): The King of Desktop Printing
This is undoubtedly the most widespread and well-known 3D printing technology, especially in the home and hobby user segment. The principle is easy to understand: a plastic string, called filament, is unwound from a spool and pushed into the print head. Inside the head is a heating element (hotend) that melts the filament into a semi-liquid consistency. This molten plastic is then extruded through a thin nozzle onto a heated print bed, where it draws a cross-section of the model layer by layer. After one layer is applied, the print bed or print head moves, and the process repeats until the entire object is finished.
The terms FDM and FFF (Fused Filament Fabrication) essentially refer to the same process. However, FDM is a registered trademark of Stratasys, which invented this technology in the 1980s. The community and other manufacturers therefore use the open term FFF.
For printing more complex shapes with overhangs (parts that hang in the air), it is necessary to generate so-called supports. These are temporary structures that are printed along with the model and provide it with support. After printing is complete, these supports are mechanically removed – broken off or cut away.
- Advantages: Affordability of printers and materials, wide range of usable plastics, simplicity, and relative speed for less complex objects.
- Disadvantages: Visible layers on the surface of the print, lower resolution and detail accuracy compared to other technologies, necessity of support removal.
Stereolithography (SLA): Precision and Detail
This family of technologies represents the original form of 3D printing and is synonymous with high precision and a smooth surface. Instead of plastic filament, liquid, photosensitive resin (photopolymer) is used as the building material, contained in a transparent vat. A UV light source then selectively cures the resin in the desired areas, creating a solid layer of the model.
There are several variants of this technology, differing primarily in their light source:
- SLA (Stereolithography): Uses a UV laser beam precisely directed by mirrors to progressively “draw” each layer. It is a very precise method, but print speed depends on the complexity of the given layer.
- DLP (Digital Light Processing): Instead of a laser, it uses a digital projector that illuminates and cures an entire layer at once. This makes the method typically significantly faster than laser SLA, as the time per layer is constant regardless of its content.
- MSLA (Masked Stereolithography) / LCD: This technology, which popularized resin printing for home use, utilizes an array of UV LED diodes as a light source. An LCD screen is placed between the LEDs and the resin vat, functioning as a mask – it only allows light to pass through where curing is desired. It is a cost-effective and fast method.
It’s important to realize that the process doesn’t end when the model is removed from the printer. The print is covered with uncured resin and must therefore undergo post-processing: first, it is washed in a solvent (usually isopropyl alcohol – IPA) and then finally cured in a UV chamber. Furthermore, resins are toxic chemicals, so when handling them, it is absolutely essential to use protective equipment such as nitrile gloves and safety glasses, and to work in a well-ventilated area.
- Advantages: Exceptional level of detail, perfectly smooth surface, ideal for miniatures, jewelry, and prototypes with fine features.
- Disadvantages: Higher material cost, need for more complex and messy post-processing, safety risks associated with chemicals, usually smaller print volume.
Industrial Technologies: The Power of Powder
These technologies are the backbone of professional and industrial additive manufacturing, enabling the printing of highly functional and durable parts.
- Selective Laser Sintering (SLS): This method uses a high-powered laser that progressively sinters thin layers of fine powdered plastic, most commonly nylon. A key advantage of SLS is that the model does not require any printed supports. During printing, it is fully surrounded and supported by loose, unsintered powder. This allows for printing extremely complex geometries and freely moving assemblies in a single step.
- Direct Metal Laser Sintering (DMLS) / Selective Laser Melting (SLM): The principle is very similar to SLS, but instead of plastic powder, metal powder is used (e.g., titanium, aluminum, stainless steel). The laser fully melts the material here, creating dense and strong metal parts comparable to those made by traditional machining.
Other industrial methods: The world of additive manufacturing is even broader and includes technologies such as Binder Jetting, where a print head deposits a binder onto a layer of powder (metal, sand, or ceramic), or Material Jetting, which works similarly to an inkjet printer, but instead of ink, it deposits drops of photopolymer that are immediately cured by UV light. Stratasys also developed SAF (Selective Absorption Fusion) technology, which uses an infrared lamp to melt powder onto which an absorbing liquid has been applied.
It Works
We’ve introduced the key technologies that power the world of 3D printing. From affordable FDM printers for everyone, through precise SLA printers for perfect details, to industrial giants using the power of powder. Each method has its place and purpose. Now you know how printers work, but what do you need to print something yourself?
In the next article, we will guide you through the complete process from A to Z: we will show you where to get a 3D model, how to prepare it for printing, and what equipment you will need.
