FDM vs SLA: How does 3D Printing Technology Work?

FDM vs SLA: How does 3D Printing Technology Work?

History of 3D Printing

3D printing technology has been around since the 1970’s but has recently been making headlines in mainstream news for it’s dramatic impact on engineering, research, and medical industries around the globe.  As the technology advances, a hobbyist community has emerged and desktop 3D printers are now available for people to use in their homes. So what is 3D printing all about and how do some of the main processes work? 

There are numerous types of printers that range from low-cost plug-and-play desktop 3D printers, to industrial $100k+ machines.  There are two main processes used among desktop 3D printers, Fused Deposition Modeling (FDM)and Stereolithography (SLA). Although they both serve to create a physical product from a 3D model, these technologies work quite differently. Let’s look at the main ways in which  FDM and SLA 3D printers differ. 

FDM Technology

FDM stands for Fused Deposition Modeling, which simply means that material is deposited in single layers that fuse together to create a 3D object.

How it works:

  1. A 3D model file (usually a .STL or .OBJ) is imported into a program called a slicer. Cura, Slic3r, and Simplify3D are all great examples of slicer programs. This program will “slice” the object into single layers and create gcode that tells the printer where to move and also controls parameters like print speed and temperature. 

  2. Gcode is sent to the machine

  3. The printing nozzle heats and melts filament that’s forced through the nozzle

  4. The object is built layer by layer with each successive layer fusing on top of the one below it until the 3D object is complete

Pros and Cons of FDM 

FDM printing is one of the most popular forms of 3D printing for home use. The mechanisms are simple and this allows FDM printesr to exist in an affordable price range, typically between $200 and $4,000.
Although they require a great deal of tinkering and calibration to print optimally, FDM printers can produce models with moderate amounts of detail and strength. FDM printers are limited in the intricacy of the details they can produce so for finer models or professional grade prototypes, SLA machines are a better choice.

SLA Technology

Stereolithography (SLA) printing was first invented in the 1980’s and works by curing resin with light. The light solidifies a liquid resin via a process called photo-polymerization and builds objects layer by layer. Currently, SLA is among the most accurate forms of 3D printing. 

There are two main types of SLA Technology: laser based (typically abbreviated as SLA) or projection based (abbreviated DLP for Digital Light Projection).

Laser SLA 3D Printing 

How it Works

  1. The 3D Model is imported into a slicing program like PreForm

  2. A tank is filled with liquid photo-polymer resin 

  3. A build platform lowers into the tank and one layer of the design is traced by a UV laser. The laser is positioned using galvanometers which are sets of mirrors that rotate and reflect the laser. 

  4. The liquid resin hardens into a solid creating a single layer of the object. This process is repeated and the build platform raises until the object completes.

Pros and Cons of SLA

SLA printers are known for their ability to create highly detailed and intricate designs. Layers are chemically bonded with each other rather than mechanically bonded as is the case in FDM which allows for isotropic parts with high mechanical strength. 

The resulting objects can be used for a variety of professional and functional applications. SLA can also be used with a variety of different kinds of resin which will produce objects of different physical and aesthetic properties. For example, Formlabs’ Tough Resin can be used for applications where a high degree of strength and mechanical resistance are needed.

Since SLA creates prints with superior accuracy and strength, it comes at a higher average cost compared to FDM printers. For a deeper dive into SLA technology, check out The Ultimate Guide to Stereolithography. 

Image Source: Formlabs

DLP Technology

DLP and Laser-based SLA are very similar with the major difference between them being the light source. Instead of lasers, DLP printers use a projector below the resin tank to expose the entire layer at once. Laser-based SLA has an edge on DLP as far as printing accuracy and finish quality goes, but DLP machines can come at a lower-price point due to the simpler mechanics involved. 

The Form 2 Desktop SLA 3D Printer


Historically, SLA printers have only existed at the industrial level and cost upwards of $10,000. Formlabs changed the industry with the launch of the Form 1 in 2012, ushering in a new era of low-cost and professional grade SLA 3D printers accessible to consumers. They’ve since developed two new iterations of their product and offer free sample parts for those interested in discovering the quality of SLA printing for themselves. 



Pinshape is a 3D printing community and marketplace where makers from all over the world can find and share their next great 3D print and help each other get the best results from their 3D printers.

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  • marco

    I do own a Kudo3D Titan and have been less than impressed by the manufacturing quality of this product. This is basically a PC tower case from Taiwan, fitted with a scrap chinese arduino compatible card, and a poor junior developped software to drive it.The red diamond like plexiglass cover – apart the fact it protects the prints from external UV light – is only there for the geeks and brings no more that headeaches when you need to put it on and off at each print. The only quality part of this printer is the Z-arm mechanism, made in Japan and the Viewsonic projector. Nothing that justifies the price though. Ok, now, let’s dive into the facts : THE BAD : lot’s (i mean plenty) of trial/error that sucks your available time even if you’re psychologically prepared to spend it (be prepared to purchase many VATs in advance to absorb the devastating errors of your learning curve, and a good stock of vitamins to help you keep your sleeping time minimal), a build plate which is impossible to make perfectly horizontal due to its pretty unreliable and cheap ball lock mechanism, a scrap software that does not always send the sliced images to the projector at start of sequence (lets be honnest, the culprit may well be windoz!), a software which only accepts sliced images (no STL), an arm mechanism that screams loudly when in operation – even when oiled or greased -, vibration and resonance in the whole assembly when operated, a software which does not save correctly your entries for future reference (exposure, lift height, lift speed etc.), the lack of obturator to protect your precious projector lens against resin spills, a basic threads/screws (and screwed-up) mechanism to adjust the projector height (and thus XY resolution) that makes any XY resolution change a not so human challenge when you want to keep calibration (dimension accuracy) ok. THE GOOD: the teflon FEP film on top of a transparent silicone gel seems to bring more reliability to this VAT design, Once you’ve captured the good settings, you can expect quality builds as advertized in their website, but the learning curve is much much too steep. To my observer eyes – intellectual value set aside – the value of this printer should be no more that 500 US$ in terms of assembly, electronics and software. I would not recommend it to anyone. My Kudo Titan1 will be on sale asap to be replaced with a more qualitative FormLabs2 (same price!). Fed up with poorly designed products and DIY trial & errors. Now, next step… it’s time for predictability and ease of use !

  • Sean

    the form 1 had the same problems as the kudos titan.
    The update kit for the titan 2 is like 300 bucks…
    And it seems to have addressed the same issues that were resolved with the form 2.
    Any new technology like this will have a steep learning curve. maybe you should have done a little more research before blasting a good product for the not equivalent from another company…
    Just sayin…