FDM vs SLA vs SLS

FDM vs SLA vs SLS

The term 3D printing is all encompassing. It describes a process – creating a solid object from a computer aided design file (CAD). However, there are three different methods consumers can use to complete this process. Each method is unique and requires users to consider factors such as cost, time, and materials. While the techniques aren’t tailored for a specific project, they do have their best uses, and, like all things, they each have their drawbacks. When selecting a 3D printer, the printing method should be one of the most important aspects to consider, as it will dictate how you use the printer.  In this article you’ll learn the differences between 3 popular printing technologies: FDM vs SLA vs SLS (Fused Deposition Modeling, Stereolithography, & Selective Laser Sintering).

Fused Deposition Modeling (FDM)

FDM Process Video by Solid Concepts, Inc

The most user-friendly of the three printing methods being compared here, fused deposition modeling is based on a fairly straightforward concept. The production material (often a variation of plastic – though more materials continue to be developed) is fed from a spool through the heated printer nozzle. As material passes through the nozzle, it melts into a semi-liquid state. The printer head then moves along a software controlled path (similar to the way a standard printer prints text & images onto a sheet of paper), extruding the semi-melted plastic onto the print bed. This process continues in a layered fashion, building the object by layering a series of stacked “slices”.

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Stereolithography (SLA)

SLA Process Video by Solid Concepts, Inc

In many ways, SLA printing works in a manner that’s almost opposite to the way that FDM printing works.  SLA printing begins with a tank of photopolymer resin – liquid plastic that has sensitivity to UV light.  The “printing” is controlled by an ultraviolet laser, which strikes the top layer of liquid resin – curing the liquid into a solid layer, in accordance with the shape of the 3D digital file being printed.  With each successive layer, the object being printed is raised out of the liquid (while the bottom of the printed object maintains contact with the top layer of liquid) – such that additional layers are added to the bottom of the object with each pass of the laser.  Viewed over time, it can appear that the object is rising (or being pulled) out of the liquid tank.  Because each layer is cured with the precision of a laser, objects printed using SLA technology are smooth to the touch and extremely high-resolution.

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Selective Laser Sintering (SLS)

SLS Process Video by Solid Concepts, Inc

Laser Sintering printers use powdered materials to create printed objects, rather than the solid or liquid raw materials associated with FDM and SLA printing.  Like an SLA printer, SLS printers use a laser to facilitate the printing process.  The powdered material is heated in this manner to temperatures either just above or below the material’s melting point, fusing the nearby powder together & forming a solid layer.  This layer is shifted down into the powder bed, allowing space for the next layer to be fused on top.  Additional powder is roll back over the object in progress, so the laser always passes over a flat layer of powder.  Once the print is complete, the printed object and loose powder surrounding it are pulled vertically from the powder bed.  The loose powder is manually cleared away from the now-solid printed object, resulting in the finished print – a generally porous, rough surfaced item inherent to the SLS process.  Due to the complexity and messiness of SLS, no desktop consumer models are currently available.

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Determining Your Printing Method:  FDM vs SLA vs SLS

The printing method that works best for you will depend primarily on your end goal. If you want to produce a more affordable prototype that can handle the stress of multiple different tests, FDM printing would be best. However, if you want to make smaller, more refined objects that don’t require any finishing touches, SLA would work better. Though SLS hasn’t yet become a personal printing method, it would be the go-to choice for quickly creating a limited run of prototypes in different materials. Other factors to consider include budget, timeframe, and safety. The uses for 3D printers are as varied as the people who use them. With their recent popularity spike and improved technology, 3D printers are changing the face of product manufacturing.

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