Fastest 3D Printers: Compare FDM, SLA, and SLS 3D Printing Speed

Stereolithography is used to describe several different resin 3D printing processes that involve using light to cure liquid resin, most commonly through a tank with a transparent bottom, printing parts layer by layer upside down on a build platform that is lowered into the tank. These processes include: laser-powered stereolithography (SLA), digital light processing (DLP), or masked stereolithography (MSLA, also often used interchangeably with LCD 3D printing).

Typical print speeds vary by the type of resin 3D printing process, with the fastest type being MSLA and DLP technologies. The latest generation of MSLA 3D printers, like Formlabs’ Form 4, rely on a combination of a powerful print engine and advanced optics system to cure each layer almost instantly.

• SLA print speed can be similar for one part and a fully packed build. While the laser in laser-based SLA printers has to travel a large area to cure the resin, MSLA and DLP cure each layer almost instantly. Because entire layers are cured at once, there is almost no difference in speed between prints with many parts and prints that contain just one part, enabling a higher possible throughput.
• SLA print speeds are affected by printer components. The quality and performance of the print engine and optics system influence how much light reaches the tank and have a direct impact on print times. Also, other factors, such as Form 4’s dual-layer flexible film resin tank, Release Texture, high-speed automated resin filling, and fast resin heating, decrease overall print time.
• SLA prints require post-processing, but most of it can be automated. After printing, SLA parts need to be washed with alcohol or ether to remove any excess resin and some parts also require a post-cure to help them reach optimal material properties. Both of these steps can be automated with advanced post-curing solutions.

All 3D printing processes have become faster over time, but none can match the progress in resin printing. Advances in resin 3D printing technology have enabled blazing fast print speeds that, when combined with the scalability factor of the technology, can rival the throughput of traditional manufacturing solutions like injection molding.

SLS 3D printers are faster than FDM 3D printers because their high-powered lasers can be directed at each layer of powder and scanned across it faster than an extruder nozzle can move above an FDM print bed. However, the laser still moves slower than the light source flashing in MSLA or DLP resin 3D printing technologies. 

Though not technically print speed, SLS 3D printing processes also have to account for the cooldown time of the build chamber — because the laser sinters the powder at such a high temperature, the build chamber has to cool down before being post-processed, which can add to increased overall lead time for parts.

This combined print and processing time for SLS parts, however, is generally not a concern for production. Though print speed for single parts may be longer than with other technologies, overall throughput is excellent for SLS 3D printers because of their larger build volumes and the self-supporting print bed that allows parts to ‘nest,’ so that customers can fully pack the build chamber and reach production volumes, even with only one printer.

For example, a fully packed print job on the Fuse 1+ 30W can be completed overnight during ‘dead time’ and the cooldown can finish outside the printer during the day, enabling same-day parts and 24/7 throughput.

• SLS 3D print speed depends upon part size. Parts that are larger along the X/Y axes take longer to print as the laser has to trace a larger area. By optimizing the path of the laser on the Fuse 1+ 30W for efficiency, Formlabs managed to decrease print times by up to 25%.
• SLS print speeds are affected by printer components. Print speed is highly dependent on the laser power. For example, the Fuse 1+ 30W uses a powerful 30W laser to achieve high throughout. A typical print job takes just seven hours and 95% of fully packed print jobs can be completed within 14 hours.
• SLS parts require post-processing, but it is very efficient. SLS post-processing can be quite short, since many steps can be automated with machines like Fuse Sift and Fuse Blast, and there are no supports to remove, empowering users to go from printed to professionally finished parts in as little as 15 minutes.

While SLS 3D printing is not the best choice for producing a single part as fast as possible, the combination of low cost per part, high productivity, efficient post-processing, and established materials make SLS a popular choice for manufacturers and a cost-effective alternative to injection molding for low-volume or bridge manufacturing.

As each 3D printing technology produces parts in layers, the larger the print is along the Z-axis, the longer it will take to print.

However, bigger part size or more parts in a build along the X and Y axes don’t necessarily increase print time. 3D printing processes that cure entire layers at once (MSLA, DLP) will print large parts and fully packed builds faster than technologies where the nozzle has to travel longer distances (FDM) or trace parts individually (laser-based SLA, SLS).

Understanding how to measure resolution in 3D printing, particularly across a wide range of technologies, involves analyzing a printed part on 3 axes: Z (vertical) and X/Y (horizontal). The Z-axis resolution is heavily influenced by layer height, while the X/Y resolution is influenced by a number of different factors depending on the 3D printing technology you use.

Layer height (Z-axis resolution) affects speed for all types of 3D printers. If your print has thicker layers, it will require fewer overall layers to be printed, decreasing overall print time.

With FDM 3D printers, there is a significant tradeoff between print time and resolution. Thicker layers will require fewer overall layers to be printed, decreasing overall print time, but they’ll also result in more visible layer lines and a less smooth surface finish.

Some FDM printers offer users the option to increase the speed at which the extruder deposits filament or moves over the build area. Additionally, users can also install larger nozzles that can deposit more material faster, but decrease X/Y/Z resolution. However, each of these options results in lower accuracy and resolution, worse surface finish, and other undesirable outcomes.

SLA 3D printers offer high resolution regardless of the layer height. Resin printers can direct the light extremely precisely at the liquid resin, resulting in parts with superior surface finish even when printing thicker layers. While layer lines might be slightly more visible on curved surfaces, for most parts, there’s barely any visible difference between a part printed at 50 microns or 100 microns that would justify the 2X print time. X/Y resolution depends on the resolution of the projector or LCD screen, or the laser spot size and how precisely it can be controlled — which are defined by the hardware specs and generally superior to all other processes (50 microns or below).

Similar to SLA, resolution is less of a concern for SLS 3D printers. The laser used in SLS 3D printers can precisely fuse particles and printed parts generally don’t have any visible layer lines. Most SLS printers don’t even allow users to change the resolution — Z resolution is not adjustable, while X/Y resolution is defined by the hardware specifications.

Material selection can have a measurable effect on the overall time to print. FDM, SLA, and SLS 3D printers all print polymers, but heating/extruding, curing, and sintering are very different processes.

With FDM 3D printers, the type of filament can make a big difference when it comes to 3D print speed. In general, materials that are easy to print with, like PLA and PETG are the fastest printing filaments. The print speed for engineering materials like ABS and nylon is slightly behind. However, flexible materials like TPU need to be printed substantially slower to ensure higher print success rates.

When printing with an FDM 3D printer, it is always a good idea to start on a slower setting to ensure the first few layers adhere properly to the print bed (and each other) before increasing speed. Faster print speed is also more likely to result in failed prints and overall lower print quality — learning how to optimize for quality on a fast FDM 3D printer is a matter of trial and error.

In SLA 3D printing, the opacity of resins as well as the concentration of photoinitiators and other curing agents added by the resin manufacturer can affect the printing speed. 

For example, Fast Model Resin, Formlabs’ fastest resin, has a higher concentration of photoinitiators and is capable of printing at speeds of over 100 mm per hour on Form 4. This makes it possible to print smaller models in minutes and a fully packed build in less than two hours.

In general, clear resins print slightly faster because they have a greater cure depth, which means the light source must spend less time curing each layer. Additionally, high-viscosity resins, such as glass-filled resins or those used in dentistry for dentures, will typically print more slowly than low-viscosity resins. Similarly to FDM, flexible materials also print slower than rigid materials.

With SLS 3D printers, nylon 12 is the most widely used material and is also generally the fastest, but all other materials offer comparable print speeds, including flexible materials.

While the general perception is that complexity in 3D printing is free (compared to traditional processes like machining or injection molding), it’s not entirely the case when it comes to print speed.

Model complexity has a slight negative effect on print times for FDM, laser-based SLA, and SLS 3D printers. The reason is similar to why X/Y part size affects print speed more for some printers than others — these printers have to draw or trace the part geometry for every layer, which takes longer for more complex shapes. However, because MSLA and DLP printers cure an entire layer at one time, more complex parts do not equate to slower speeds. 

The other, generally more important aspect is support structures. In both FDM and SLA printing, support structures are often needed to successfully print more complex parts, like those with many overhanging features. After a print job is completed, support structures need to be removed and any irregularities in the finished part sanded down.

_{Formlabs SLA 3D printers use light-touch supports that are easy to remove, reducing post-processing.}

Not only do support structures add time to post-processing and use valuable material, but they can also add time to the printing process, particularly in FDM and single-laser SLA 3D printers.

SLS 3D printing does not require the use of supports because unsintered powder keeps the printed structure in place. As a result, SLS print jobs don’t waste any powder, or time, on creating supports.