Two main 3D printing methods, Fused Deposition Modeling (FDM) and Stereolithography (SLA), are popular in the industry because of their unique capabilities.
If you want to choose the best 3D printing technology, understanding the differences between FDM and SLA is important.
But what are the advantages and disadvantages of FDM and SLA 3D printing?
We compare the two processes based on:
- Print speed
- 3D printing materials
- Strength and durability
- Precision and quality
- Applications in various industries
What is FDM 3D Printing?
Fused Deposition Modeling (FDM), alternatively referred to as fused filament fabrication (FFF), is the most common 3D printing technology available on the market. Typically, FDM 3D printers operate with singular or dual extruders that are compatible with thermoplastic filaments. The filament is loaded into the machine via material spool, melted and deposited onto a heated build platform following a predetermined guide path. The materials simultaneously cool and adhere to another to create a 3-dimensional part.
FDM printers come in a variety of sizes and material compatibilities, and can range from $5,000 to $500,000. Materials may include plastics such as ABS, ASA, PLA and more advanced 3D printers are beginning to offer carbon filled and nylon materials that are stronger and longer lasting.
FDM is relatively inexpensive compared to alternate 3D printing methods and tends to yield the most consistent results when it comes to repeatability and strength. In addition, post processing with FDM is simple and most of the time, non-hazardous.
Printing with thermoplastic materials through extrusion nozzles leads to tolerance and resolution challenges. Compared to other 3D printing technologies, FDM may leave layer lines or slight build blemishes due to the heating and cooling of materials.
What is SLA 3D Printing?
Stereolithography (SLA) was introduced to the market during the 1980’s and was quickly adopted by many service manufacturers and consumer product companies. Instead of filament SLA 3D printers operate with photopolymers, which is a light-sensitive material that changes physical properties when exposed to light. Instead of an extrusion nozzle, SLA uses a laser to cure a liquid resin into a physical piece through a process called photopolymerization.
This unique printing process enables higher resolution parts that have isotropic and watertight properties. Photopolymers are thermoset materials, meaning they react differently than thermoplastics. Similar to FDM, there is a range of SLA printers available in the market with different sizes, material capabilities and price ranges.
Laser technology creates pinpoint accuracy which allows for higher tolerance parts with improved resolution compared to alternative technologies. If you require a highly aesthetic part, you may want to consider SLA.
What SLA gains in beauty it loses in strength. While some SLA materials are engineered to perform better in some scenarios, it’s almost impossible to replicate the same mechanical properties of ABS, nylon, and other FDM filaments. If your parts require functional testing, we recommend sticking with FDM.
FDM vs. SLA: Choosing the Right Technology
Printing large parts or need a large enough build platform for multiple parts/low volume production? It’s not easy to find a 3D printer capable of printing large pieces and of course, size is subjective so it’s important to determine what big means to you.
Since we are working in three dimensions, never underestimate Z height and always remember that parts can be built in different directions to optimize strength or finish. When comparing technologies, it’s important to determine what type of parts you intend to 3D print today and proactively plan for what may be produced in the future. The most common regret is lack of 3D printer capacity.
Finding a large format SLA 3D printer is very difficult and nearly impossible due the nature of the technology. First, there is more waste associated with a large vat of liquid resin. Second, individual part costs tend to be higher since materials will be more expensive. Finally, the pinpoint accuracy of a laser is certainly beneficial for higher resolution parts but that leads to much longer printing times.
★ FDM 3D printing is the ultimate choice when building large parts and has been for quite some time. The inherent benefits of FDM indicates that it’s much easier to have repeatable results, regardless of part or build platform size. Next, there is much less material waste and the time it takes to produce large or many parts is much shorter than many SLA alternatives. Simply put, it’s affordable to print big with FDM.
In our hyper competitive commercial and industrial marketplace, new product development and manufacturing speed is paramount to capturing early adopters and market share. 3D printing provides that edge and enables the overnight production of parts without operator oversight. Whether you are deciding between SLA or FDM technologies, speed may not be the most important factor since conventional manufacturing or manual processes take longer than both. With that being said, if 3D printing speed is a priority—consider part aesthetics or resolution.
SLA is famous for building parts that are cosmetically superior to FDM due to the laser technology capable of printing down to 25 micron layers. Taking part size into account helps to accurately determine how long the part will print. Compared to FDM, the speed is almost negligible.
★ However, FDM technologies are typically capable of offering several different nozzle sizes (.6mm, 1mm, 2mm) which provides flexibility for engineers to speed up the printing process. Compared to SLA, FDM is significantly faster but it comes with a compromise. Naturally, the larger nozzle sizes lead to thicker layer lines. Ultimately, you must consider your part requirements and balance between resolution and speed.
A 3D printer is useless without materials. What is your testing and evaluation process throughout prototype development? How important is it to prototype or produce parts that are mechanically identical to the end-use parts? Would it be advantageous to your engineering team to have parts with chemical resistance capabilities? Static dissipative advantages? There is so much to consider when determining the right 3D printing technology for you but none is more valuable than understanding the material capabilities and output.
SLA materials are ideal for niche applications but lack overall strength and functionality compared to FDM. For example, some SLA materials have biocompatible characteristics that combined with the high resolution capabilities make it perfect for some medical device prototyping and dental use cases. However, SLA materials hardly meet the mechanical properties required for the majority of commercial or industrial requirements.
★ If you require materials that are representative of the end product then you should consider FDM 3D printing. Standard thermoplastics such as ABS, PLA and nylon are commonly used throughout major industries and available on most FDM technology platforms. The strength and durability properties of FDM are superior compared to SLA. This improves product testing and will enable engineers to advance new product development with more confidence and accuracy.
*FDM 3D printing technology is uniquely beneficial compared to SLA because of the ability to build parts with varying densities. While retaining part functionality, it’s possible to create internal honeycomb structures that reduce overall weight and part fatigue. Learn more about how to optimize your designs.
Strength & Durability
Prototyping and product validation can be a rigorous process that includes a series of testing that puts a significant amount of wear and tear on a part. Every industry imaginable must ensure product performance to some degree and the great companies invest accordingly to make this possible. As previously noted, the strength and durability of FDM materials are superior to SLA. ASA materials printed on FDM 3D printers have UV resistant properties that make it ideal for outdoor applications (lawncare, homeowner equipment, etc). Nylon materials are oftentimes used for automotive aftermarket parts that require long lasting durability.
When prototypes or production parts must perform in harsh environments, SLA materials tend to degrade, break or deform simply because the mechanical properties are not completely representative of the end-use part. When determining which technology works for your application, remember to consider what type of environment these parts will need to perform in. It may look nice in the laboratory but it must function in the real world.
3D Printed carabiner carries the 500 kg wight of a large 3D Printer
Precision & Quality
Precision and quality are subjective terms that are informed by deisgn intent. For example, those operating in the consumer product and packaging industries require tight tolerances since they will inevitably move to injection mold tooling and are unable to sacrifice precision. Having a speedy printer or advanced material options is great but are your printed parts representing the design intent?
If your product development lifecycle inevitably includes mass manufacturing with injection molding, SLA may be the right option for you. However if you need high quality parts for industrial applications, consider FDM. For example, custom fixtures built to function in a production environment require ultimate functionality and do not necessarily need to have cosmetically clean features. By understanding the design intent of your part you can manage expectations and determine which 3D printing technology works for you.
Applications & Industries
According to AMFG, 3D printing adoption is growing across shop floors globally, evidenced by more than 70% of enterprises finding new applications for 3D printing (Sculpteo, 2019). In addition, the number of manufacturers using 3D printing for full-scale production has doubled between 2018 and 2019 and the overall market is expected to exceed $20 billion by 2022 with an anticipated CAGR between 18.2—27.2%. This represents a wide range of industries, applications and use cases that are pushing 3D printing further than ever before.
Encompassing aviation, space and satellite manufacturing, the aerospace industry is the most cutting edge when it comes to 3D printing and technology adoption. The strict requirements for functionality limit SLA 3D printing simply because the materials do not perform well in rugged environments.
However, advanced thermoplastic materials with FDM have improved strength or ESD properties have been utilized for prototype development and interior cabin components. As previously mentioned, the inherent benefits to create lightweight structures with FDM printing is uniquely advantageous to the aerospace market.
The automotive market is notorious for using ABS plastic and polypropylene for prototyping and end-use purposes. Since the majority of their applications require robust and durable materials, FDM tends to be the most common 3D printing technology for prototyping, jigs & fixtures, drill guides and low volume production requests. It’s common that automotive engineers require materials with advanced chemical resistant properties that continue to perform when exposed to gasoline and other chemicals, justifying the use of FDM. However, SLA does have an advantage printing clear parts used to test reflectors and lighting mechanisms.
The consumer product industry encompasses everything from kitchen appliances to toys, or handheld hardware equipment to electronic devices. Speed to market is imperative, therefore new product development requires quick iterations and immediate feedback. Oftentimes, products are introduced to consumers before product launch and require it to exceed form, fit and functionality.
It’s not uncommon that both technologies are used in the prototyping process or early validation testing. For example, a handheld device may have an ESD enhanced ABS plastic shell combined with a soft touch TPU grip printed on SLA. More often than not, the ability to print in high resolution with SLA is more attractive to consumer product manufacturers when compared to FDM.
The healthcare market includes medical device development, educational training aids and niche applications for the dental and hearing aid market. Typically, the medical device market requires prototypes and parts to be sterilized which means that the material must withstand certain temperatures through a process called autoclaving. SLA and FDM technologies offer the appropriate materials, but it takes some investigation.
Educational training aids typically require high resolution since they are used for communication purposes, making SLA ideal. The dental market is notorious for using SLA, and the hearing aid market is split between SLA and FDM. Due to the nature of the healthcare market and the importance of printing tiny details, SLA is most preferable.
Research and academic institutes across the world have adopted FDM and SLA technologies in droves. There isn’t a single university without a makerspace, and most secondary schools are beginning to position 3D printing in a variety of different ways. Typically, it’s used to motivate students to try new technologies and embrace their inner entrepreneur.
Many researchers have an interest in expanding material capabilities that make 3D printing a viable option for the future. Whether the purpose is research or student learning, most universities and teaching institutes lean towards FDM due to the relatively low cost and equipment simplicity. Post processing can be challenging with SLA, therefore FDM is a more student friendly option. In addition, the future of FDM looks brighter when it comes to material expansion for manufacturing purposes.
What is your design intent? What problems will 3D printing solve for you today? Tomorrow? What are the most important factors when determining a capital equipment expenditure at your facility (ROI, productivity, innovation)?
To quickly summarize the information presented above, FDM and SLA 3D printing technologies have their own advantages and disadvantages when it comes to specific applications or usage. When building larger prototypes or industrial parts, consider FDM for the size and cost benefits. When determining which materials mimic your design intent, take a hard look at the material compatibility and evaluate the benefits from each technology—FDM is more robust for functionality while SLA provides higher resolution and better accuracy.
There are thousands of examples where the aforementioned industries have adopted either SLA or FDM technology so although this comparison gives some information, it does not complete the entire picture. Not every industry, production facility or prototype department acts the same and not everyone fits into nice, neat check boxes. Therefore, we recommend speaking with the experts to determine what makes the most sense for you.
Talk to a 3D Printing Expert
Find out which 3D Printer is right for you.
FAQ: Short Overview
FDM stands for Fused Deposition Modeling, alternatively referred to as fused filament fabrication (FFF), is the most common 3D printing technology available on the market. FDM printers operate with extruders that are compatible with thermoplastic filaments. The filament is loaded into the machine via material spool, melted and deposited onto a heated build platform following a predetermined guide path. The materials simultaneously cool and adhere to another to create a 3-dimensional part.