3D printing technology encompasses many different technologies within the broader term. According to the State of 3D Printing 2020 report, the top three 3D printing technologies in the world are Selective Laser Sintering (SLS), Fused Deposition Modelling (FDM), and Stereolithography (SLA) respectively dominating the market. So, we pitch these three technologies against each other to bring you the FDM vs SLA vs SLS battle.
FDM v/s SLA v/s SLS
Let us take a closer look at the three most popular 3D printing technologies for printing plastics.
FDM 3D Printing Technology
FDM, or Fused Deposition Modelling, also known as FFF or Fused Filament Fabrication, is the cheapest form of 3D printing technology available to everyone. It uses polymer materials in filament form, which are melted by a heater and then extruded onto the build platform in subsequent layers to form the final part. Common materials used include PLA and ABS, while other materials like Polycarbonate, Pet-G, Nylon, and exotic filaments such as Glow in the dark, wood-filled, metal-filled are also used.
FDM printers are best suited for fitment testing, shape tests, proof-of-concept models, or simple and quick prototyping. However, they are not recommended for aesthetic testing or complex parts and fine resolution parts as the layer lines are visible and rough on the touch. FDM printed parts are dimensionally accurate and can be post-processed for a finer finish.
The main challenge with using FDM printers is the print resolution and the use of supports. Supports can be difficult to remove and may leave a spot at the touch point. Industrial FDM printers use soluble supports to eliminate this issue.
Another challenge is storage of filaments. Most of the filaments absorb moisture and thus have to be stored in a cold and dry place to safeguard against failed prints through errors like blobs while printing. Desktop FDM is still prone to failures and needs a lot of trial and error. So, getting a good quality print can take time and considerable effort. Moreover, the industrial printers are quite standardised and do not require such trial and error methods to get better results. They mostly hit the ground running but this means you’ll have to shell out more money to buy such a printer.
SLA 3D Printing Technology
SLA or Stereolithography is the world’s first patented 3D printing technology. It is one of the most rapidly growing 3D printing technologies in the world. The industrial 3D printers require huge investment but the desktop printers are far cheaper are provide closely resembling accuracy and perfection. SLA printers provide the highest resolution and accuracy out of the three types of printers. The resolution is as low as 25 microns. It also provides such a smooth finish that the layer lines are almost undetectable.
These printers use a UV laser which is flashed on the resin contained in a tank. On exposure to UV light, the resin hardens. The hardened resin is built up layer by layer to form the final object.
The materials used in SLA printers are photopolymer liquid resins. They are UV sensitive and harden when exposed to UV laser. The resins vary according to the application. The most commonly used resins are tough, castable, flexible, dental, etc.
Parts printed in SLA 3D printing technology are recommended for highly detailed parts which require smooth surface, tight tolerances and functional parts. The smooth finish and high resolution enables it to be used in mould & pattern making, jewellery, dental and model making industry.
The main challenge here is that SLA printing is messy and users have to deal with the sticky and viscous resin material. The maintenance is a tedious process with an additional consumable, the resin tank itself. SLA printing also requires additional equipment like the washing stating and the curing station. Without this the resin cannot be completely cleaned from the print and the part does not achieve full strength without curing it in an UV station. Cleaning the resin tank, the build plate, the scrapper and then also taking care of the resin by straining the remaining material back into its bottle, all takes a toll if you are not too keen on using 3D printers.
Some of these challenges may seem small but if you are intermittently using your printer then it can become strong hurdles. However, if you are continuously printing back to back parts, then the cleaning of equipment is reduced as you are just adding material and running new prints. Obviously, this is true unless you are not changing the material. If you change the material then you again have to follow the tedious cleaning process to avoid contamination or missing of two different materials.
SLS 3D Printing Technology
SLS or Selective Laser Sintering is a powder bed fusion 3D printing technology wherein the material is in a fine powdered form. This powdered material is melted at a particle level with a CO2 laser to fuse with the adjacent particles to trace out a layer. The object is built layer by layer to form the final object.
The powerful CO2 lasers fuse the powder particles together while the unsintered powder acts as a natural support to the printed part. Due to such a technique SLS can generate complex geometrical parts which are not possible in any other 3D printing technique. The elimination of supports is a big enough reason for the popularity of this technology.
Since the build platform is always completely filled with powder, numerous parts can be printed simultaneously. This helps in faster printing for multiple parts. SLS 3D printing technology is perfectly suitable for complex structures, thin walls, reverse features, etc. These parts have excellent mechanical and strength properties. It is a first choice for functional prototypes and is a cost-effective replacement for injection moulding for small batch productions.
The materials used in this type of 3D printing technology are polymer and namely, Nylon. Nylon has good chemical, heat and impact resistance. It is strong and flexible and this makes it the perfect material for 3D printing in SLS.
The challenges in SLS printing is that you cannot use it at home or in office environment (although some brands have a safer office version). The powder material is really fine and is toxic if inhaled and so you as an operator need to be appropriately clothed and must be using mask and gloves. Additionally, the powder can easily blow away with even slight air so you need to have an air conditioned room, proper HVAC system. The part taken out from the SLS printer has a lot of excess powder sticking to it and to remove this powder you will need a depowdering station. After this you will also need a sintering station to ensure the layers are strongly fused.
All these professional machines means you cannot effectively use it in office spaces, and need a lot of space, needs excess investment on supporting equipment. The unsintered powder is also a consumable and can only be used a limited number of times after which it has to be disposed-off adding to the overall cost of the printer maintenance.
Summary: FDM vs SLA vs SLS
All the 3D printing technologies FDM vs SLA vs SLS can be summarized as below
| Criteria | FDM | SLA | SLS |
| Material | ABS, PLA, Nylon | Photosensitive Resins | Polyamide (Nylon), Polystyrenes, Thermoplastic Polyurethane (TPU), Metal (ColdMetalFusion) |
| Layer Thickness | 0.5 to 0.127 mm | 0.05 to 0.015 mm | 0.05 to 0.01 mm |
| Surface Texture | Rough (can be post- processed for fine surface) | Smooth | Slightly rough |
| Support Structures | Required | Required | Not required |
| Post-Processing | Sanding, Polishing, Painting Smoothing (with acetone vapor) | Painting, Dyeing | Polishing, Varnishing, Dyeing, Painting |
| Cost | Cheapest | Medium Price | Costly |
FDM is the most affordable 3D printing technology from amongst the three. It has its limitation in terms of the surface quality and consistency in getting reliable results (at least for the desktop versions) but it is comparatively easier to operate. It uses thermoplastic polymers like ABS, PLA, PETG, PVA, Nylon, etc., that are widely available at affordable rates. It can achieve a resolution of 100 microns on desktop machines and a bit finer on costly industrial systems. It is a good technology for prototype manufacturing, simpler projects that aren’t affected by surface quality.
SLA is costly compared to FDM technology but cheaper compared to SLS technology. The technology requires costlier components like the laser, galvanometers, costly materials and also extra investment in equipment like the washing and curing stations. It uses thermoset polymers that are formulated for application specific usage. It can achieve the finest resolution of the three technologies and thus delivers the smoothest surface finish.
SLS is the costliest 3D printing technology from among the three technologies as the technology is much more complex, requires costly parts and even requires additional costly equipment. Therefore it is ideal for factory floor usage. It uses polymer materials like nylon in a powdered form and can achieve a maximum layer thickness of 60 microns and so the surface texture rougher than SLA but finer than FDM.
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