3D PRINTING INFO

3D Printing Technology Choice: FDM v/s SLA v/s SLS

FDM, SLA & SLS technology

3D printing technology encompasses many different technologies within the broader term. FDM is the most popular 3D printing technology and most widely used technology across the world. According to the State of 3D Printing 2017 report, the top three 3D printing technologies in the world Are Fused Deposition Modelling (FDM), Selective Laser Sintering (SLS) and Stereolithography (SLA) respectively dominating 94% of the market.

Let us take a closer look at the three most popular 3D printing technologies for printing plastics.

FDM, SLA & SLS technology
Above: 3D Printed parts made in FDM, SLA & SLS technology (from left to right)/Image Credit: Formlabs

FDM 3D Printing Technology

FDM stands for Fused Deposition Modelling. It is also known as FFF or Fused Filament Fabrication, a name originating from the RepRap movement. FDM is the cheapest form of 3D printing technology accessible to everyone. It uses polymer materials in a filament form which are melted by a heater and then extruded onto the build platform in subsequent layers to form the final part.

The most common materials used are PLA and ABS. Other materials like Polycarbonate, Pet-G, Nylon, Exotic filaments like Glow in the dark, wood-filled, metal-filled are also used.

The FDM printers give a coarse finish to the parts as their resolution is limited to 100 microns. The layer lines are visible and rough on the touch. However, they can be post-processed for a finer finish.

FDM printed parts are dimensionally accurate and are recommended for fitment testing, shape test, proof-of-concept models or simple and quick prototyping but are not recommended for aesthetic testing, or complex parts or fine resolution parts.

The main challenge in using FDM printers is the print resolution and the use of supports. The supports are sometimes difficult to remove and leave a spot at the touch point. However, industrial FDM printers use soluble supports to eliminate the support issue.

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.

FDM, SLA & SLS technology
Above: Part Printed from an SLA 3D Printer/Image Credit: Sprintray

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.

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.

FDM, SLA & SLS technology
Above: Complex structure printed in SLS 3D Printer/ Image Credit: Sinterit

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.

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. Similar technique is used for metal printing called as DMLS, Direct Metal Laser Sintering.

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.

All the 3D printing technologies FDM vs SLA vs SLS can be summarized as follows:

A Summary of 3D printing technologies
Above: A Summary of 3D printing technologies

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