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Choosing the Right 3D Printer: FDM vs SLA

Two of the most popular categories of desktop 3D printers right now are FDM printers and SLA printers. Read on to learn which is the best option for you and your 3D printing needs.

MakerBot 3D Printing Professional Solutions

FDM and SLA are two of the most popular 3D printing technologies available today / Courtesy: MakerBot and Formlabs

With the types of 3D printers now available, it has become quite confusing to choose the right 3D printer for a particular job. The fact that 3D printers are getting better and more affordable only increases the dilemma.

Here, we bring you a comparison of two of the most popular types of desktop 3D printers to help in choosing the right 3D printer for your needs & applications.

FDM PRINTER – EXPLAINED

MakerBot METHOD X 3D printer
MakerBot METHOD X 3D printer

FDM (Fused Deposition Modeling) falls under the material extrusion category of 3D printing technology. This technology was invented and patented by Scott Crump, co-founder of Stratasys, in 1989. An FDM printer uses a thermoplastic polymer in a filament form to create three-dimensional objects. 

In an FDM printer, the filament is pushed into the hot extruder. The filament is heated first and then deposited, through the nozzle, onto a build platform in a layer-by-layer process to form the complete object. 

SLA PRINTER – EXPLAINED

SLA 3D Printer / Courtesy: Zortrax
SLA 3D Printer / Courtesy: Zortrax

SLA (Stereolithography Apparatus) falls under the Vat Photopolymerization category of 3D printing technology. This was the world’s first ever patented 3D printing technology and was invented by Charles Hull, an American engineer, in the mid-1980s.

SLA uses a liquid resin material to print objects. This technology uses a powerful laser to form the 3D object. In this technology, a laser source sits at the bottom of the vat filled with liquid thermosetting resin. The laser is selectively flashed onto the liquid photosensitive resin and the exposure to the laser cures (hardens) the material. This process is followed until every single point on the layer is exposed and hardened. Once completed, the process moves towards the next layer and then to the next. This process continues until the entire model is cured and the resulting 3D print is ready.

COMPARISON FOR CHOOSING THE RIGHT 3D PRINTER

FDM 3D printing in process with MakerBot SR-30 material

The comparison points explained below will help the user in choosing the right 3D printer as per his usage and needs. 

MATERIALS - CHOOSING THE RIGHT 3D PRINTER
Nylon Carbon Fiber FDM Printer Material
Nylon Carbon Fiber FDM Printer Material

FDM: FDM printers use a wide range of thermoplastic polymers, but also composites in the form of a filament. Since the base thermoplastic materials are cheap, the filaments as well are quite affordable and can be found at comparable prices across the world. One kilogram of 3D printing filament can range from $24 to $99, depending on the material type and quality.

SLA: SLA printers have a more limited range of materials available for 3D printing. SLA uses photosensitive thermosetting plastics in a liquid resin form. The resins are costly and are mostly manufactured by SLA printer manufacturers. A one liter of resin costs approximately $100 to $200, depending on type and quality.

These are highly specialized materials used for specific applications like dental, jewelry, tough, high-temperature, etc.

COLOR & BLENDS - CHOOSING THE RIGHT 3D PRINTER
FDM materials come in a wide range of color options
FDM materials come in a wide range of color options

FDM: FDM’s material availability is matched by its color selection. Regardless of material type, dyes can easily be combined with the material in production to produce a full palette of colors giving designers and engineers lots of flexibility. With a wide range of materials suppliers comes even more variety in colors, with some manufacturers even offering custom color matching for selective customers.

SLA: SLA materials do not offer a large variety of colors and are generally found in black, gray and transparent colors. All the SLA materials however are blended forms of the original base material and so they are available as application-based materials. While colors are often limited, there are certain instances in which experimenters can mix in their own pigments to create various colors, though this can be a difficult process.

SURFACE FINISH - CHOOSING THE RIGHT 3D PRINTER
SLA is capable of producing jewelry-level detail / Courtesy: 3DPrintersShop
SLA is capable of producing jewelry-level detail / Courtesy: 3DPrintersShop

FDM: The surface finish achieved through FDM printers is coarse and the layer lines are clearly visible due to the minimum layer height. The line thickness as seen from above is typically around 400 microns (the bead resulting from the diameter of the nozzle). The line thickness as seen from the side can be adjusted typically from 50 - 400 microns - this is called resolution or layer height.

SLA: Because SLA printers utilize a laser for “drawing” each line of the part, the resulting lines can be much smaller and more precise resulting in a smooth surface finish. The approximate width of the laser and the resulting cured lines is 20 microns.

ACCURACY - CHOOSING THE RIGHT 3D PRINTER

FDM: FDM 3D printing achieves good dimensional accuracy for larger features. For smaller features, the dimensional accuracy is hampered and sometimes is not consistent. This can also be hampered depending on the 3D printer type (DIY, desktop, professional, or industrial FDM printer). Choosing the right 3D printer becomes a task because the accuracy also depends on other factors like the calibration and slicer settings. Materials also play a role in the accuracy through their shrinkage properties. One example of a precise 3D printer - the MakerBot METHOD - utilizes a unique heated build chamber allowing for a high level of dimensional accuracy.

SLA: As an SLA printer is able to achieve a very fine resolution, the dimensional accuracy is unmatched by most of the other 3D printing technologies. If the primary objective is surface finish and accuracy on fine features (such as in jewelry or dentistry), SLA is a great choice.

PART STRENGTH – CHOOSING THE RIGHT 3D PRINTER
3D Printed Bracket / Courtesy: 3DHubs
3D Printed Bracket / Courtesy: 3DHubs

FDM: FDM printers tend to have an advantage when it comes to producing durable, usable, long-lasting parts due to their ability to print in known polymers and composites. Printing in nylon carbon fiber, for example, will allow for a lightweight part that is incredibly strong.

SLA: Typically, SLA printers are known more for their creation of delicate and detailed parts rather than for strong parts. This is due to a combination of factors. For one, cured resins tend to be fairly brittle. Another reason is that unlike FDM prints, SLA prints cannot be printed solid as such parts will result in cracks, warping, and often print failure. There have been some new stronger resins in development, but they are far from perfect and have often not been proven in the field as have many of the known polymers and composites on the FDM side.

EASE OF USE - CHOOSING THE RIGHT 3D PRINTER
SLA printers use toxic resin and requires extra precautions when handling
SLA printers use toxic resin and requires extra precautions when handling

FDM: FDM printers are fairly straightforward - insert plastic filament in one end, and extruder out the other. This simplicity and relative cleanliness has made FDM printers a choice for those who want to use them in an open office or educational environment. The parts come out dry and clean, and often there is just the singular post-processing of removing supports by breaking them off. The remaining material is easily stored in hard plastic filament form for the next print.

SLA: While SLA printed parts can be nice looking, there is a little extra work that goes into the process. The nature of printing parts in a liquid resin can be too much of a hassle for some due to the resulting mess - parts come out sticky, and resin can find its way into the larger workspace. Also the resin can be highly toxic - requiring the use of goggles, gloves, and other protective equipment. 

Post-processing involves multiple steps - first washing the print to remove excess resin, followed by clipping off supports which requires clippers (be careful not to remove features that are actually the print!). Lastly, a further curing process using a UV lamp is recommended to finish the part. The remaining material of liquid resin must be kept in the tray away from light and has a short shelf life once in the tray.

This chemical-laden process means that SLA printers are most often found in closed labs.

3D PRINTING COSTS - CHOOSING THE RIGHT 3D PRINTER

FDM: FDM is the most affordable technology available in the entire space. It is not only inexpensive in terms of the actual machine but also in its operations as the materials are comparatively less expensive than those for other technologies. As a result, products manufactured through FDM 3D printing tend to be less expensive  than for comparative products.

SLA: The SLA printer is a costly machine. It involves the use of expensive parts like laser source and scanning mirrors. The materials are also expensive. Additionally, almost all the models require some amount of support structures and so 3D printed output also gets expensive. 

SIZE – CHOOSING THE RIGHT 3D PRINTER
Stratasys Fortus 900mc / Courtesy: Stratasys
Stratasys Fortus 900mc / Courtesy: Stratasys

FDM: FDM printers are available in a wide range of build volumes. From smaller desktop versions to large-format industrial versions, the build volumes can be manufactured as per the need of the user. The largest FDM printer packs a volume of approximately 2,475 liters.

SLA: SLA printers have a limitation on their build volumes. They are generally not very big. The largest SLA printer has a volume of approximately 618 liters.

SUMMARY

Jamco America use the MakerBot METHOD 3D Printer to bring complex aircraft parts to market faster.
Jamco America use the MakerBot METHOD 3D Printer to bring complex aircraft parts to market faster.

FDM printers and SLA printers have proven popular across many industries and their use continues to grow. While some may choose one technology over the other, many see the benefit of utilizing both alongside each other and benefiting from each technology’s strength. For example, a designer at a company might choose to use SLA to get a detailed look at a final part, while an engineer might use FDM to produce a part in a production material, such as ABS, for prototype testing. 

If you have to choose one or the other - ask yourself if you need a more robust part printed in more common materials, or if you need a highly detailed part that looks nice. If you need a stronger, usable part, an FDM printer might be the way to go, but if you just need a nice looking, detailed part, the SLA printer might be your choice. Either way, 3D printing is a great way to quickly take a digital design and make it a physical reality!

Want to find out which is going to be the best fit for you and your organization? Talk to a MakerBot 3D printing expert today!

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