Without a doubt, additive manufacturing is revolutionising multiple sectors. More and more companies and users are joining the so-called 4th Industrial Revolution. Since its creation in the 80s, multiple 3D technologies have been developed, and new developments are emerging every year.
All additive manufacturing processes have in common the fact that they can generate very complex geometries in a very fast way depositing layer upon layer. In all cases, the objects have a material texture of very thin, almost imperceptible layers. However, each of these technologies carries its benefits and its drawbacks. Hence, before selecting a technology to run your project, it is essential to understand what suits your needs the most.
SLS (Selective Laser Sintering) Vs. SLA (Stereolithography)
While SLA allows printing in a wide range of materials, with good mechanical properties, the pieces manufactured with SLS offer greater resistance than those produced in SLA. The SLS prints objects resistant to high temperatures and with greater resistance to impacts. The SLA does not withstand high temperatures well, becoming deformed above 60 degrees Celsius, and is less re-sistant to impacts. Although this difference is reduced as the technology is being perfected in coor-dination with the materials.
Surface texture of the output of SLA 3d printed product is smooth and often shinny. However, the output of SLS 3d printing is slightly rough. SLA 3d printed parts are strong and brittle whereas SLS 3d Printed parts are strong and flexible.
Today many companies use SLA to make silicone moulds and make vacuum polyurethane castings, as a 3D model crafted with SLA technology, is produced on a perforated plate in the photo-polymer bath, which keeps the original identification of each layer unaltered. SLS 3d printed parts are used as functional parts in the automotive and aerospace industry.
FDM (Fused Deposition Modeling) Vs. SLA (Stereolithography)
The method of operation of both FDM and SLA is similar; Both types of 3D printing technologies manufacture the pieces layer by layer. The FDM deposits material throughout the area of the layer in which it is located, while the SLA solidifies the resin directly thanks to a laser beam. However, we can see a huge difference in both the products when it comes to materials used and colours.
The most commonly used materials with FDM printers are PLA and ABS. Although, if you are looking for some advanced materials, it is increasingly common to use materials such as PETG, Nylon and mixtures of materials such as PC-ABS or PLA with fibers.
While the variety of materials and colours used with FDM technology is becoming more extensive every day, in SLA, the variety is much more limited in both types of materials and colours.
We must also understand that with FDM printing it is normal to get good finishes with layer heights of 0.1mm only if the printed parts do not have parts with very complex shapes or small size. Most FDM printers use standard coil models that are supplied by manufacturers with filament diameters of 1.75mm or 2.85mm. The diameter of the filament is decided by the manufacturer of the FDM printers depending on the type of movement (Cartesian or delta) and the type of extruder.
In short, FDM technology is limited by the diameter of the nozzle to be able to realize the minimum thickness. When using supports of the same material as that of the piece, the surface finish is usu-ally not uniform, requiring post-processing in the contact area of the supports.
On the other hand, in printers with SLA technology the printing precision is very high, even with complex shapes because the diameter of the laser that solidifies the resin is very small. For exam-ple, the SLA printer can make pieces with layer heights of 0.025mm, getting final and functional pieces directly. The accuracy is such that SLA technology is capable of making jewellery and den-tal application models in complete detail.
When it comes to materials used for printing products, there is a wide variety of materials for FDM printers, hence, adhesion to the base is usually not a problem, especially since there are very effective products that help with adhesion. Even for materials very prone to warping, such as PP, there is already the Smart Stick that solves the problem without having to use PP sealing tape. The removal of any material from the base of an FDM printer is very simple, so much that the most it can be done by hand.
For supporting the FDM printing, usually soluble materials like HiPS or PVA is used, which are very easy to remove. HiPS is diluted in D-Limonene and PVA in water. These materials are very practical, especially when you want to make objects with complex shapes or internal conduits, where manual post-processing is not able to arrive.
In SLA printing technology, adhesion is never a problem, but more dedication is needed when re-moving parts from the printing base. These are usually so attached to the base that a special spatula is needed to take them off. After printing on an FDM printer, only the post-processing is necessary to remove the supports. However, when you finish printing a part on an SLA printer, you must remove the surface layer of resin without solidifying it in an isopropyl alcohol bath or in a washing centre such as Form Wash. Most resins can be sanded and painted once they are fully solidified.
FDM technology is ideal for economical and fast prototypes, which do not need to have a great surface finish or exact precision in their measurements. You should go for SLS 3d printing if you are looking for high precision functional parts. SLA 3d printing technology is recommended to use for pieces or objects that require a great finish with exact measurements, of the level of final pieces. When evaluating which of the two technologies is better, surely the answer depends on what you want.