SLA vs FDM 3d Printing What Are the Differences and Advantages to Each
3D printing is a manufacturing process that converts a digital design into a physical model with the help of SLA and FDM technology. SLA (StereoLithography apparatus) and FDM (Fused Deposition Modeling) are two of the most popular printing technologies, and they’re entirely different. Each of them has its own workflow, methodology, and a series of advantages and disadvantages. Some applications yield better results with SLA printing, others with FDM. In this article, we’re going to explore the key differences between SLA and FDM and form a comparison.
FDM is the most common printing technology because it’s the most accessible. It’s user-friendly for beginners and pros alike, affordable to get started with, and reliable. It’s considered by many to be the gateway in 3D printing.
An FDM printer is simple to operate. First, it receives information from a digital file that says how the model should be printed. This involves the use of slicing software such as Cura, Simplify3D, or Slic3r. They provide us with all the tools we need to create the model digitally.
Then the slicer prints the object by using a thermoplastic filament. There’s a wide range of plastics and each one of them has different characteristics. Some of them melt at lower temperatures but are more brittle, others are highly resilient but require high melting temperatures. In either case, the filament is fed through the printer just like a wire and it’s heated until the melting point is reached. The filament is then extruded through the nozzle by following a specific pattern to form the physical model. The printer will build layer after layer on top of each other until the model is complete.
SLA printers build models layer by layer just like FDM printers do, but that’s where they stop having anything in common. This type of technology doesn’t use a thermoplastic filament, but liquid resin. This resin turns solid when hit by the printer’s laser.
The SLA printing process starts when the laser hits the resin in an accurately targeted location to solidify it. The printer knows where to hit the resin based on the information it obtains from the model’s digital file. Furthermore, under the targeted area, the printer has a build plate that moves inside the resin vat. As it moves and each layer is hardened by the laser, the plate starts rising and the whole process repeats itself until the model is finished.
Due to the nature of this technology, SLA printers enable us to print highly detailed models. The layers are also thinner than those generated by FDM printers, and they bind much better at a chemical level, not just physical. This way we end up with a more detailed model that requires less post-processing work. Once the model is finished, all we need to do is remove any excess resin with a chemical bath.
That being said, this technique doesn’t offer us as many building materials as FDM printers do. In fact, we’re quite limited, and the resin has to be carefully handled because it’s toxic. Due to these reasons alone, SLA printing is not recommended for complete beginners. In addition, an SLA printer costs several times what an FDM printer costs.
One of the first things we need to take into account is the material and how much it costs. This is where FDM printers shine. They are very popular and therefore there’s a wide variety of materials, such as PLA, PETG, ABS, nylon, as well as ceramics and metal. Additionally, these materials come in a lot of colors and diameters and some of them can even be custom made. Because of the popularity and affordability of FDM printers, there are plenty of materials to choose from based on the purpose of the model you’re printing.
As for SLA printers, the material depends on the manufacturer. In addition to having a much smaller choice, we should stick to the materials made by the printer’s manufacturer. Every manufacturer follows a specific design. Furthermore, the material color is just as limited but it can be painted or dyed in post-processing. As for material costs, SLA resin is more expensive than thermoplastic filament.
Just like with any other type of technology, there are various operating costs to consider. When it comes to FDM printers, most of the cost is sunk in thermoplastic filaments and nozzles. Remember that for FDM printers you have a wide range of materials to choose from and the cost will depend on the type. For example, PLA filament costs around $25 per 1kg spool.
As for SLA printers, the operating costs are higher, just like the initial investment is. However, due to the manufacturing technique, there’s more to consider than just material and cheap accessories like nozzles.
First, you need resin. Just one liter of it costs around $100 and it can easily go up to $150 or more. In addition, once you spend around 3 liters of resin, you’ll have to replace the resin vat because it becomes stained over time and the laser loses its accuracy as a result. If you keep printing this way, you’ll end up with less detailed models or even unusable ones. Therefore, replacing the tank is obligatory and it costs somewhere between $50 and 80$, depending on the manufacturer.
But the resin and resin vat aren’t the only things to consider. With time, the build plate becomes too worn out or damaged and it has to be replaced as well. This component easily costs $100 or more.
As you can see, there are far higher operating costs to consider when it comes to SLA printers, while operating an FDM printer is budget-friendly.
This is one of the most important aspects to consider when getting a printer.
FDM printers rely on the nozzle and the pattern in which the extruder moves vertically and horizontally. Depending on the diameter of the nozzle, and the accuracy of the extruder, we can print a quality model or something that goes straight in the recycling bin. It’s crucial to calibrate the printer correctly. However, the model of the printer will also determine the quality that can be produced. FDM printers differ from brand to brand, not to mention price category.
Furthermore, since FDM printers build the model from the ground up, several things can go wrong. The lower layers have to endure pressure from the upper ones. This is where your design choices and calibrations will have a lot to say. A lot of things can go wrong, such as warping, shifted layers, shrinking, misalignment, and cracking. The type of filament also has a role to play here. To obtain a quality print with an FDM printer you need to find the right balance between hardware, design, calibration, and choice of material.
That being said, here’s a summary of quality-related aspects of FDM printing:
- The nozzle determines the quality of the print.
- Warping can occur if the material cools off too quickly after being melted.
- The lower layers can be damaged when subjected to the weight of the upper layers.
- Bad calibration can lead to inconsistent delivery of material and lead to missing layers.
- Stringing can occur if the molten plastic flows in unwanted areas.
- The nozzle can clog and it requires frequent cleaning.
- Calibration is frequently needed. Sometimes this includes some improvisation as well.
On the other hand, with SLA printers we’re able to be more accurate and print finer details because there’s no nozzle involved. Instead, the quality depends solely on the quality of the optical laser. This also means that there’s a lot less stress on the lower layers so the risk of dealing with warping and structural problems is smaller. As a result, we can obtain smoother surfaces, thinner layers, and create far more intricate objects.
FDM printers can be faster than SLA printers if we set them that way, but that comes at a cost: quality. When you go for high-speed printing, you lose quality. But this is where calibration comes in to find the ideal balance. Furthermore, the printing speed of an FDM printer depends on the type of material and how much time it needs to melt and then cool off. These factors will slow or speed up the printing process.
On the other hand, SLA printers are quite fast without sacrificing quality. It all depends on the laser beam hitting the targeted sections accurately. The beam cures the material quickly, especially if it’s powerful. In addition, SLA printers don’t generate as much heat as FDM printers, and this gives them a speed boost.
Overall SLA printers can be faster than FDM machines while maintaining a good printing quality.
Print Bed Adhesion
Once the printing process is over, we still have to remove the model so we have to take adhesion into account when comparing SLA and FDM printers.
When it comes to FDM printers, it’s quite straightforward. If the model is stuck to the build plate and we can’t safely remove it by hand, all we need is a palette knife. On the other hand, SLA printers require more elbow grease.
SLA models will adhere with a strong grip. It will feel as if it’s glued to the build plate. Therefore, removing it without damaging it is a bit more difficult, especially because the residual resin will usually remain on the platform as well. Again, the palette knife should do the trick, but it will require more effort due to the accumulated material. However, more expensive models come with systems that prevent additional resin from hardening at the base of the model, thus making our job a lot easier.
Both SLA and FDM prints need to go through a post-processing phase that can take hours, but there are some differences between the two.
FDM prints sometimes come out with design mistakes. For instance, there might be holes that need to be filled with epoxy compounds or rough surfaces that require a thorough sanding. On the other hand, SLA prints require another step.
As mentioned earlier, some resin will harden at the base of the model, but this also includes the model itself. You will often have to remove the additional resin before going through the rest of the post-processing phase. To clean an SLA model, it has to go through a washing phase after printing. But that doesn’t mean scrubbing its soap. The residue covering the print has to be removed with an isopropyl alcohol bath. And that has to be done carefully because the substance eats away at the material. If you leave the model for too long in the bath, you will damage it or at least weaken its structural integrity. Afterward, you can sand and polish the surface of the model.
Mostly due to the price range, FDM and SLA printers are aimed towards different industries and types of users. For example, SLA printing is ideal for making jewelry and medical prosthetics due to the high accuracy and detail that can be achieved. On the other hand, SLA printers aren’t the best choice for creating products meant to be regularly exposed to the elements, especially the sun.
As for FDM printers, they’re more versatile. They can be used by hobbyists to design decorative models and by professionals who make functional products. They’re also an inexpensive manufacturing method when it comes to producing prototypes and items designed for outdoor use. The FDM printer’s versatility is mainly due to the large variety of materials we have access to.
Advantages and Disadvantages in a Nutshell
Both printing technologies come with their own advantages and disadvantages depending on how they’re used. Neither one is better than the other as long as we use them correctly as they were intended.
- FDM printers start at low prices making 3D printing accessible to anyone. For only a couple of hundred dollars, you can start learning and practicing.
- Materials come in a wide variety and they’re generally affordable. The material can be chosen based on the purpose of the model.
- The software is user-friendly, making 3D model designing highly accessible to beginners.
- FDM printers are easy to use and can be upgraded piece by piece. Improvisations can also be made by fans of DIY techniques.
- FDM models can be used for a wide variety of purposes, ranging from medical prototypes to chess pieces.
- FDM is the most popular kind of printing technology and therefore there are many sources for learning, as well as free open-source tools.
- FDM printers are not suitable for printing high-detailed models. Though professional-grade printing can be achieved with high-end FDM printers and a lot of calibration and fine-tuning, SLA printers are better in this area.
- FDM machines have to be calibrated properly based on many factors ranging from material type, filament diameter, ambient temperature, type of model, and more. They need to be fine-tuned for each project to achieve the best results and that can take a lot of time.
- The quality of the print depends on the quality of the hardware in a lot of cases.
- Should be used in a well-ventilated area due to emitting ultrafine particles which can be toxic over prolonged exposure.
- SLA printers are the ideal choice for highly-detailed complex models due to their accuracy.
- Layers are thinner and chemically bonded, thus reducing the risk of warping and structural weakening.
- The surface finish is smooth that sometimes sanding isn’t needed.
- SLA printers require no upgrades, modifications, or DIY improvisations. They are meant to produce high-quality prints as soon as they’re plugged in.
- SLA printers have a much higher cost and are usually not accessible to beginners.
- The SLA printing process requires more technical know-how.
- Operating costs are much higher than for FDM printers. Materials are more expensive, as well as regular maintenance.
- SLA printers are not generally recommended to beginners because they need to be carefully handled. The resin is toxic.
- Resin models are sensitive to the sun and prolonged exposure to it will ruin them.
Both SLA and FDM machines have their place in the world of 3D printing. It’s up to us to focus on each printer’s strengths. Cheap doesn’t automatically mean bad and expensive doesn’t always give the best results. Each project has different requirements and one type of printer will be a better choice than the other. So, if you’re wondering what printer to purchase or use, first spend some time thinking about what kind of projects you’re going to work on. And if you’re worried you’ll miss out by not having both FDM and SLA printers, you always have the option to use a 3D printing service.