A Breakdown of 3 Affordable 3D Printing Techniques: FDM, SLA & SLS

We are living through a renaissance for prosumer 3D printing. The technology has become affordable enough that makers and small businesses can purchase very high-quality 3D printers. This is accelerating prototyping timelines and putting more power into the hands of the product developer.

“3D printing” is actually an umbrella term that encompasses a number of printing technologies. These technologies print using different materials and are optimal for different applications. A 3D printer that is good for a particular application, might be a very poor choice for a different application. This article provides a short summary of the 3 most affordable and accessible 3D printing technologies:

• Fused Deposition Modelling (FDM)
• Stereolithography (SLA)
• Selective Laser Sintering (SLS)

Fused Deposition Modelling (FDM)

FDM is the most common and inexpensive form of 3D printing. FDM consists of extruders that move back and forth on a gantry depositing layer by layer of molten plastic to build the 3D sample. Reliable FDM 3D printers range between $2,000 and $5,000. Popular brands are Ultimaker, Prusa Research, and Flashforge.

Pros:

• Low cost
• Low maintenance
• Use real thermoplastics
• Easy clean-up after printing

Cons:

• Low resolution (< 200 um)
• Parts are anisotropic (stronger in 1 direction than another)
• Poor surface finish (surface looks grainy)

Stereolithography (SLA)

While FDM prints from the “bottom-up”, SLA prints from the “top-down”. SLA printing starts with uncured liquid resin. A light source of a specific wavelength (often UV) is used to selectively cure specific regions of the top layer of the liquid into a solid. This process is called photopolymerization The now-solid, top layer is elevated out of the liquid and the photopolymerization process is repeated on the next layer. Reliable SLA 3D printers range between $2,000 and $3,500. Popular brands are Formlabs and Prusa Research.

Pros:

• Low cost
• Low maintenance
• Exceptional resolution (25 - 100um)
• Clean surface finish
• Isotropic properties

Cons:

• Available materials (plastic substitutes, not real plastics)
• Cleaning up the sample after printing is time-consuming

Selective Laser Sintering (SLS)

SLS uses a laser to sinter (“harden”) a polymer powder. The 3D sample is built from the bottom up, sintering powder into a hardened sample one layer at a time. The material used is typically a powdered Nylon which has good mechanical and chemical properties. SLS printers are available for around $10,000. This price point has been steadily coming down, so it will be cheaper in the coming years.

Pros:

• Reasonable cost
• Good resolution (100 um)
• Clean surface finish
• Stronger and tougher samples than FDM or SLA
• Isotropic properties

Cons:

• More expensive than other technologies
• Porous finish
• Lots of maintenance
• Lots of clean-up after printing

Conclusion

Thanks to these 3D printing technologies, researchers, inventors, and garage scientists can all experiment and prototype with greater ease.