3D printing: FDM, SLA, SLS comparison

Lisa Ernst · 12.11.2025 · Technology · 10 min

The choice of the right 3D printing technology is crucial for the success of a project. Today, three different processes are available: FDM, SLA and SLS. They differ massively in costs, quality, materials and effort. A solid understanding of their strengths and weaknesses enables choosing the appropriate technology for prototypes, small series or functional components.

Quelle: Eigene Darstellung

Introduction

When FDM, SLA and SLS are discussed, it is about three methods to build a component from plastic layer by layer. Each process uses a different starting material: FDM uses filament, SLA liquid resin and SLS powder. These differences largely shape the properties of the printed parts and influence the choice of technology for specific applications.

Technologies in detail

In FDM, a plastic filament is melted by a heated nozzle and extruded as a thin bead onto a print bed. Layer by layer, the part is formed. Typical FDM materials are thermoplastics like PLA, ABS, PETG or TPU, which are supplied on spools and drawn into the extruder. This process is robust, relatively fault-tolerant and therefore widespread in hobbyist, for fixtures and simple functional prototypes. FDM-Druck (Fused Deposition Modeling) SLA works differently: A build platform is immersed into a vat of liquid resin, and a UV laser or projector cures the desired geometry layer by layer. The result is very smooth surfaces, fine details and high dimensional accuracy, as each layer is defined optically – i.e., pixel- or laser-based. The resins used range from brittle standard materials to heat-resistant or flexible variants to, for example, biocompatible formulations.

SLA (Stereolithografie) SLS finally uses a powder bed: Thin layers of fine plastic powder, usually nylon, are laid down, and a laser fuses the powder only where the part is to be formed. Unfused powder supports the part during printing, so no separate support structures are needed and very complex geometries with internal channels become possible. The resulting parts are mechanically robust, often with almost isotropic properties, and are suitable for functional prototypes, small series and applications with impact or temperature loading.

SLS (Selective Laser Sintering) In simple terms: FDM works with filament, SLA with liquid resin and SLS with a powder bed – three paths to 3D-printed plastic parts that differ greatly in detail.

Clear comparison of the key features of FDM, SLA and SLS, showing the strengths and weaknesses of each technology.

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SLS remained largely confined to large industrial facilities for a long time, which quickly cost around 200,000 USD. But benchtop-industrial systems reduce the entry; a complete SLS setup consisting of printer, powder management and post-processing costs around 60,000 USD, while the printer with a depowdering kit already starts under 30,000 USD. Other providers place SLS systems in the range of about 60,000 to 100,000 USD and drive a veritable race toward compact, 'affordable' SLS printers.

In practice, a clear deployment pattern has emerged: FDM is mainly used for inexpensive prototypes, fixtures and larger parts where visible layer lines are acceptable. SLA is standard for highly detailed design and functional prototypes, medical models, dental applications or casting molds, where surface finish and dimensional accuracy are foreground. SLS is mainly used for functional plastic parts, complex geometries, snap fits, hinges and small series, where mechanical properties and design freedom are more important than a perfect finish directly off the printer.

The choice between FDM, SLA and SLS rarely depends solely on the technology, but on a mix of budget, willingness to take risks and the real tasks of the parts. Many beginners choose FDM because the acquisition costs and materials are cheapest and errors are comparatively easy to forgive. Those who want fine details, smooth surfaces and precisely fitting prototypes quickly end up with SLA – despite higher material costs and additional post-processing steps.

At first glance, SLS often seems oversized, but in professional environments the calculation tilts as soon as many parts are printed per week and post-processing should be kept to a minimum. The powder bed replaces support structures, parts can be packed densely in the build volume, and the processing effort is usually limited to blowing out and cleaning – thus the labor time per part drops significantly. SLA also offers a well-standardizable workflow with automatable washing and curing processes, while FDM delivers inexpensive parts but, especially for complex geometries, requires a lot of manual support structure removal and surface finishing.

Manufacturers naturally communicate these differences with their own emphasis: providers of resin printers like to highlight surface quality and precision, while FDM manufacturers argue with material variety, build volume and speed. Independent comparison guides distill from this simple decision rules like 'FDM for simple functional prototypes, SLA for detailed models, SLS for robust end parts' and try to present strengths and weaknesses of the processes transparently side by side. For you that means: behind every recommendation lies a context – your project benefits if you consciously consider this context rather than just looking at a ranking.

This video clearly explains how the materials, surfaces and details of FDM-, SLA- and SLS- parts differ by showing real components side by side and commenting on their properties.

The three main players in 3D printing: FDM, SLA and SLS – each technology with its unique properties and application areas.

Facts and Myths

Many comparison articles claim that SLA offers the highest detail fidelity and the smoothest surface among the three techniques. This statement is well supported, as SLA in technical guides is consistently described as the technology with the finest resolution and the tightest tolerances. Overviews comparing FDM, SLA and SLS classify FDM as medium detail quality, SLS as rather rough, matte surface, and SLA as the finest structures and visually high-quality models.

Equally well supported is the assessment that FDM is the most cost-effective entry method, both for printers and materials. While SLA resins and SLS powders typically lie in the higher tens to hundreds of dollars per liter or per kilogram range, FDM filaments start at around 20 USD per kilogram and remain well below the material prices of the other two processes, even for engineering plastics.

Also well established is the fact that SLS does not require separate support structures because the unfused powder supports the part during printing, enabling complex geometries, including internal channels. Technical descriptions and application notes highlight this advantage as a central argument when it comes to hollow spaces, overhangs or interlocking mechanisms.

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It remains unclear which process is objectively fastest, as the answer depends strongly on part size, layer height, fill density, cooling time and machine type. Comparisons show that fast resin printers often come out ahead for individual, highly detailed parts, SLS reaches the highest number of parts per job when the build volume is fully utilized, and FDM remains competitive for simple, smaller parts – there is therefore no universal speed winner.

Equally hard to answer universally is the question of which process is always the most economical per part, as besides material costs also machine price, depreciation, utilization, energy and labor costs play a role. Reputable cost calculators recommend always incorporating your own usage profile, typical quantities and the planned runtime of the system, rather than uncritically adopting smooth euro-per-part values.

Misleading/false claims

The widely spread claim that SLS is fundamentally only for large corporations and completely out of reach for smaller companies or ambitious makers is no longer tenable in this absolutist form. While acquisition costs remain significantly higher than for FDM and SLA, with benchtop-industrial systems starting at barely 30,000 USD for the printer and around 60,000 USD for a complete ecosystem, SLS has become realistic even for development departments of smaller firms and specialized service providers.

Equally misleading is the statement that FDM parts are always mechanically unusable compared to SLA and SLS. With the right material choice, appropriate layer height, sufficient wall thickness and smart part orientation, FDM parts can be produced that are more than stable enough for many fixtures, housings and functional prototypes, even if SLS has an overall advantage in isotropic properties and long-term strength.

Also shortened is the notion that resin printing is generally “too dangerous” for offices or small workshops; in fact there are clearly designated, certified resins as well as extensive safety and disposal instructions from the manufacturers. As long as ventilation, personal protective equipment and disposal according to safety data sheets are implemented, SLA printing can be operated in a controlled manner – still you should always check current product information and local regulations before deciding on a resin printer for the workplace.

Visual comparison of test patterns produced with FDM, SLA and SLS technologies to highlight the different surface qualities and material properties.

Conclusion and Outlook

Ultimately there is no 3D printing technology that can do everything perfectly; there are processes with clear strengths and equally clear limits. FDM offers the cheapest and most flexible entry for simple to medium-weight plastic parts, SLA delivers the highest level of detail and smooth surfaces, and SLS plays to its strengths for robust, complex parts and growing quantities. If you define your requirements honestly, compare a few sample parts and also consider hidden costs such as post-processing and downtime, you can choose a technology that truly fits your project technically and economically.

The good news: You do not have to commit definitively. Many teams start with FDM, later supplement with SLA for detail tasks or use SLS service providers as projects become more complex and quantities larger. If you understand the differences between FDM, SLA and SLS consciously, the seemingly difficult choice becomes a tool with which you can translate your ideas into robust components.

This webinar provides a compact overview of history, application areas and decision criteria of FDM, SLA and SLS and demonstrates with real-world examples why companies switch from one process to another.

Open questions

Quelle: user-added

Questions about long-term stability of new materials, aging of resins and filaments, as well as the sustainability of powders and cleaning chemicals remain not fully answered. Research reviews show how strongly printing parameters, material choice and part orientation influence mechanical properties and how important it is to verify critical applications – such as safety-critical components – with your own tests rather than relying solely on datasheets.

In addition, regulatory topics come into play: Once 3D-printed parts are used in medical devices, vehicles or other safety-critical applications, standards and approval procedures come into play, which are continually evolving. Especially for biocompatible resins, sterilized nylon parts or components with fire protection requirements, it is crucial to check current certifications and test reports from material manufacturers rather than relying on older versions or marketing statements.