SLA vs FDM: Which 3D Printing Technology Should You Choose?

sla-vs-fdmAdditive manufacturing could be the technology that shapes the future of world economies. This technology is cost-effective, boosts productivity and enables inventors to transcend creative boundaries in design and style of concepts, prototypes, and end-user products. 3D printing finds use in a broad range of fields.

There has been increased adoption of 3D printers in both business and by domestic consumers. Technological advancement has made the printers more compact and budget-friendly. The only question one would ask is which among the 3D technologies is ideal for their intended use.

Types of 3D Printing Technologies

  • Fused Deposition Modeling (FDM)
  • Stereolithography (SLA)
  • Digital Light Processing (DLP)
  • Selective Laser Sintering (SLS)
  • Selective Laser Melting (SLM)
  • Electronic Beam Melting (EBM)
  • Laminated Object Manufacturing (LOM)
  • Binder Jetting (BJ)
  • Material Jetting (MJ)

The choice of your 3D printing technology should be informed by factors such as cost, materials and their availability, speed, and precision among others. This guide compares the two most established types of 3D printing technologies- FDM and SLA.

SLA vs FDM: The Difference in Printing Techniques

Fused Deposition Modeling is a 3D technique in which the printing material is well-deposited layer by layer to create the solid 3D object. The standard type of material used in FDM is thermoplastics. The process often involves feeding the material through the hot extruder to melt it so that it can pass through the print head.

There are many FDM 3D printers for every budget size. 3D printing enthusiasts can get FDM printers from prices as low as a hundred dollars. Similarly, filament rolls go from as a low as $25 per kilo. The fact that anyone can get into 3D printing without spending a fortune has made FDM printers the most popular consumer-grade 3D printers in the market.

Stereolithography Apparatus or SLA is a type of additive manufacturing where the models are constructed layer by layer using a photopolymer such as resin which is cured with UV light. With SLA printing, the solid object gets built from the top to the bottom.

In Stereolithography, the materials used are photosensitive thermoset polymers. Laser beams are commonly used UV light sources in SLA printing. SLA was the first functional 3D printing technology in the history of 3D printing. It is known for delivering smooth and highly precise finishes.

Materials and Colors

FDM printers use ABS, PETG, or PLA, filaments. The printers can handle materials such as nylon, TPU and PVA, TPU and of PLA blends of either wood, ceramics, metal, carbon or fiber. There are many filament colors to choose from, or you can have them custom made.

A typical FDM printer uses filament rolls of a diameter between 1.75 mm and 2.85 mm. These are standard filaments, but there are also some customized filaments that may be costly, but they deliver superb results.

Resin materials used in one SLA printer are exclusive; they cannot function in a different SLA printer from another manufacturer. The choice of material color is also limited to yellow, black, white, magenta and cyan. The upside is that these materials are usually high performing and durable making them suitable for industrial use.

Precision and Strength

With FDM printers, the precision of the machine is determined by the nozzle size and the accuracy of the extruder movements on both vertically and horizontally. FDM printers have a low-resolution and therefore might not deliver accurately shaped 3D models. That is a big problem when dealing with designs that involve complex geometry.

The nature of FDM printing (from the ground up) means that the weight of the upper layers compresses the layers below, leading to design flaws and weakness of the finished product. Users usually have to contend with warping, misalignment and also the smoothness of the 3D print will be of questionable quality.

To circumvent this conundrum industrialists employ supports to ensure high precision in the layering process. There are also some engineering thermoplastics that can deliver highly precise and strong parts. If need be, the final 3D print might have to go through a chemical or mechanical polishing process to fix up disproportionateness. The fact that one cannot get finely detailed 3D prints with FSM printers is the reason why industrialists prefer SLA printers.

It is possible to attain design accuracy and super strong parts with SLA printers because it does not use a nozzle to create the layers. In SLA printing the liquid resin material is hardened by a highly-focused laser, layer by layer. That helps to achieve accurate details and deliver quality and sturdier prints.

Layer Adhesion

Adhesion is another factor to consider when adopting a 3D printing technology. Adhesion refers to how easily you can remove the model from the print bed after the printing process. With FDM, it is relatively easy to remove the printed object. If it sticks, there is nothing that a decent palette knife couldn’t do.
When it comes to SLA printers, it is the exact opposite. The printed object adheres to the print bed like glue. It is usually difficult to remove 3D printed model from the print bed. One would have to remove the excess resin left on the platform using a pallet knife- but brace yourself for some hard work there

Post Processing

After the printing process, FDM printing would require you to smooth the edges by sanding. If you were using supports for a higher precision with dimensions, you would have to remove these too. You will have to take care to not to interfere with layer lines or leave marks and blemishes on the finished print.
Instead of manual removal, professionals use dissolvable supports that can be washed away. An improper dissolving could result in design deformities on the model. It is also a painstaking process that demands time and specialized equipment.

After removing the supports, the next step is the reconstruction of design flaws in the final print. You can fill holes with epoxy resin or ABS acetone compound. You will also have to polish the surfaces by sanding or vapor smoothing

With SLA printing, there is a similar post-processing process. You will start by first removing the sticky resin from the final 3D print. That is done by dissolving the parts in a bath of isopropyl alcohol. If you used supports, you would go about it the same way as with FDM printers.

The post-processing procedure for SLA printing is usually much longer than with FDM printers. That is because of the additional time required to cure the print with UV light beams. The resin dissolving process also needs the right laboratory conditions and the resultant wastes have to be disposed of in special containers.

For the dimensional precision, you can sand or polish the surface to acquire a smoother surface. You can also add some finishing with mineral oil which helps to hide discoloration. Mineral oil also lubricates the surfaces of the 3D print and reduces friction during the post-processing procedures.

Printing Costs

The accessories in FDM printing include nozzles and filament rolls. FDM printers use standardized filament rolls, and so they are exchangeable between printer models. The other good news is that these filaments accommodate those operating on a shoestring budget. A kilogram of filament goes at under $25. The reason for that is that there are many third-party suppliers selling the same interchangeable product which leads to reduced costs.

SLA printers have more consumables than FDM printers. For starters, the resin is more costly than filaments. One liter of resin costs about $ 150, but it could scale up to $250 depending on the model of your SLA printer. Then again, one would have to replace the resin tank after 3 liters of it have been printed. Here is why- after some time the resin smudges the transparent wall of the container thus blocking the UV light from passing through. The result is a drastic depreciation on print quality. A new resin tank is about $60.

The other accessory you need with SLA printing is the printing bed. Due to the adhesive nature of the resin, the printing bed gets spoiled in the removal process. A new printing platform costs about $100.
One should work with a 3D printing technology that makes the most economical sense. However, aside from the consumables, you will also have to look at the equipment costs. A consumer grade desktop
FDM printer cost about $ 2000, while the industrial-grade one costs from $15000. When it comes to the SLA technology, you will have to part with $3500 with a desktop consumer printer and from $80,000 for a desktop, industrial grade printer.

Printing Speed

SLA machines are fast because they use lasers focused on specific target areas. The fact that they use photopolymer means that the UV light can cure the material within a short time. The stronger the laser, the faster will be the curing process. There is also less heat emitted in the process.

FDM printers emit much heat, and it usually demands that the user allows time for the material to cool down and harden. The time required to heat the filament material and to cool it down makes FDM printers a tad slower than SLA printers.

The Takeaway

Both FDM and SLA have specific strengths and weaknesses. If you are looking for high precision and sturdy prints, then the best candidate for the job is the SLA printer. If you are looking to save on costs, the FDM technology is the ideal way to print your future in 3D.

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