SLA Vs. FDM: Comparing Common 3D Printing Technologies

3D printing technology has developed to date and has become an important force in the manufacturing industry, changing the way products are designed and manufactured. Among the many 3D printing technologies, SLA (stereolithography) and FDM (fused deposition modeling) are two extremely common and widely used technologies. SLA uses ultraviolet lasers to irradiate photosensitive resins and solidify them layer by layer to build three-dimensional objects. This technology can produce fine and complex objects with extremely high precision and smooth surfaces, and can use resin materials of various colors and textures. FDM heats and melts plastic filaments, and then deposits the materials layer by layer through an extruder to form an object. Its principle is simple, the equipment cost and material cost are relatively low, and the printing speed is fast. It is widely used in families, school education, maker spaces, and small industrial production, but it is usually inferior to SLA in terms of accuracy and surface quality. Understanding the characteristics, advantages and limitations of SLA and FDM is crucial for the rational selection of appropriate 3D printing technologies in different industries and application scenarios. This article will conduct an in-depth comparative analysis of SLA and FDM, two common 3D printing technologies, so as to make better decisions in practical applications.



What is the difference between SLA and FDM 3D printer?
1.What is an FDM 3D printer?
1.1How do FDM 3d printers work?
2.What is an SLA 3D Printer?
2.2How do SLA 3d printers work?
3.Material Properties of SLA and FDM
4.Characteristics of SLA and FDM 3D Printers
4.1Features of SLA 3D Printers
4.2Features of FDM 3D Printers
5.When to Use SLA and FDM


1.What is an FDM 3D printer?

Fused Deposition Modeling (FDM), also known as fused filament fabrication (FFF), is the most common 3D printing technology on the market. Typically, FDM 3D printers are equipped with single or dual extruders that are compatible with thermoplastic filaments. The filaments are loaded into the machine through material spools, melted, and deposited on a heated printing platform according to a preset trajectory. The materials cool synchronously during the deposition process and adhere to each other to build a three-dimensional part.
FDM printers have various specifications and different material compatibility, and the price range ranges from US$5,000 to US$500,000. Applicable materials include plastics such as ABS, ASA, and PLA, while some more advanced 3D printers are beginning to offer filled carbon fiber and nylon materials, which are stronger and have a longer service life.

1.1How do FDM 3d printers work?
FDM, one of the earliest forms of 3D printing, was invented by Scott Crump, one of the founders of Stratasys. The principle is very simple, just like using a hot glue gun. A spool of thermoplastic filament or plastic is heated to the melting point. The hot liquid plastic is extruded through a nozzle and forms a thin single layer on the print platform along the X and Y axes. This layer quickly cools and hardens. After each layer is completed, the platform is lowered and more molten plastic is deposited, making the part grow vertically along the Z axis.

2.What is an SLA 3D Printer?

Stereolithography (SLA) entered the market in the 1980s and was quickly adopted by a wide range of service manufacturers and consumer product companies. Instead of filaments, SLA 3D printers use photopolymers, which are light-sensitive materials that change physical properties when exposed to light. Instead of working through an extrusion nozzle, SLA printers use lasers to solidify liquid resin into solid parts through a process called photocuring.
This unique printing process is able to produce high-resolution parts that are isotropic and waterproof. Photopolymers are thermoset materials, which means they react differently to thermoplastic materials. Similar to FDM, SLA printers are available in a variety of sizes, material compatibility, and price ranges.

2.2How do SLA 3d printers work?
SLA utilizes photopolymer resins as raw material for parts. Photopolymers require intense ultraviolet light from a laser to set, which is the core concept of SLA. The build occurs on a platform immersed in resin. A laser above the tank, guided by precision mirrors, cures the liquid resin layer - by - layer to form the desired part shape. First, support structures are created to fasten the part to the platform and provide proper support. After each pass, a recoater blade breaks the resin's surface tension above the part and supplies more material. The part is constructed from the bottom up.

3.Material Properties of SLA and FDM

4.Characteristics of SLA and FDM 3D Printers

4.1Features of SLA 3D Printers
Ultra-high precision:

SLA printers use ultraviolet laser technology with extremely high precision, and can accurately shape tiny features, with a processing level of fineness that can reach the thickness of printing paper. When making parts with a large number of fine structures, such as microfluidic devices and delicate hand-made models, it can perfectly present every detail, far exceeding other printing technologies.
High-quality materials:

It uses light-curing resin materials and is quickly cured and formed by ultraviolet radiation. However, this material is a thermosetting material, and the parts made are more brittle than thermoplastics. As the exposure time to ultraviolet rays increases, it will not only become brittle, but may also fade. The actual service life is generally about 8-12 months, and it is mostly suitable for short-term use or one-time production.
Excellent surface flatness:
The layer height of SLA printers starts at only 0.004 inches (0.102 mm), which is much lower than the layer height range of FDM. This makes the connection between layers during the printing process extremely tight, and there is almost no obvious layer line. The surface of the printed product is smooth and flat, and high surface quality requirements can be achieved without complex post-polishing.
Specific application advantages:
SLA printers have significant advantages in the field of prototyping, as they can quickly and accurately transform designs into physical models, meeting the needs of prototyping with high requirements for appearance and details. At the same time, SLA printers are also the best choice when making small and complex parts with strict requirements on accuracy and surface quality. However, they are not suitable for printing parts that need to be used for a long time and are frequently subjected to stress.

4.2Features of FDM 3D Printers
Rich materials and low cost:
FDM printers use a wide variety of thermoplastic materials, including ABS, PLA, PETG, TPU, and can also use PP or carbon-filled materials. The material cost is low, and there are many colors like ABS and PLA to choose from. No painting or dyeing is required after manufacturing, and filament materials are usually cheaper than the resins required for SLA.
Low infrastructure cost:
FDM requires almost no additional infrastructure except the machine itself. Unlike industrial SLA machines, which require processing stations to remove uncured resin and UV post-curing to lock in mechanical properties, FDM saves these steps and greatly reduces costs. FDM printing software supports hollowing out parts during the build process and replacing solid interiors with lattices, reducing material usage and reducing costs.
Durable parts:
When using materials such as ABS or nylon, FDM parts are more durable than those made by SLA. SLA parts are sensitive to light due to the way they are manufactured, and they tend to fade and become brittle when exposed to light, while FDM parts do not have this problem.
There are printing limitations:
FDM printing direction has a great impact on mechanical properties. There is no overlap between layers, and parts are prone to break along the layer line. When designing, it is necessary to understand the force direction to avoid the main force pulling the layers apart; the aesthetic performance is not as good as other 3D printing methods, the layer line is obvious, and post-processing is often required; wire cooling will produce geometric limitations, 90-degree angle parts are prone to warping, and low-angle overhangs are prone to peeling, resulting in a rough surface.

5.When to Use SLA and FDM

Introduce two technical features and applicable scenarios to provide reference for selection:

SLA technology:
Based on the principle of photocuring, ultraviolet laser is used to cure liquid resin for molding.
Advantages: high precision, excellent ability to present complex and fine geometry and tiny features, smooth surface close to the texture of injection molded parts, and fast short-term molding.
Applicable scenarios: manufacturing precision parts such as jewelry prototypes and microfluidic components; making prototypes or molds that display the appearance of products, such as product appearance prototypes and art sculpture models; suitable for short-term or one-time use.

FDM technology:
heating and extruding thermoplastic filaments layer by layer to build objects.
Advantages: rich material selection and many color combinations; low cost of printer equipment and consumables; high strength and toughness of printed parts.
Applicable scenarios: making multiple versions of prototypes in the early stage of product design; projects with limited budgets or requiring large-scale production of parts; manufacturing end-use parts with high durability requirements such as industrial fixtures and mechanical parts.
Decision-making advice: Choose SLA if you are looking for high precision, beautiful appearance and short delivery time; choose FDM if you value material diversity, cost-effectiveness and part durability; you can also use them in combination, such as using SLA for display prototypes and FDM for production test parts.