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Fused Deposition Modelling vs Stereolithography

Fused Deposition Modelling - 19 October, 2022
Fused Deposition Modelling vs Stereolithography
Vicki May
19 October 2022
Fused Deposition Modelling

Introduced in the 1980s, Fused Deposition Modelling and Stereolithography 3D printers have been adapted using enhanced speed, materials, resolution capabilities, and size.

Both of these technologies have been refined and adapted over the last few years, which makes them easier to use, less costly, and more capable.

But what are the differences between FDM and SLA?

The FDM Printing Process

FDM is also referred to as fused filament fabrication. It is one of the most widely used consumer-level forms of 3D printing.

Most FDM printers operate by emitting thermoplastic materials/filaments, including Polylactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) through a hot extruder nozzle, but can also use carbon fibre.

It then melts the material and applies the plastic layer by layer to create a platform. A new layer is laid on top of the previous layer until the whole part has been printed.

FDM printers are ideal for proof-of-concept creations along with fast and low-cost simple parts prototyping, including parts that may eventually be machined.

The SLA Printing Process

Stereolithography, or SLA printing, was the first 3D printing technology to be invented.

Since its inception in the 1980s, it has remained at the top of the most popular technologies preferred by professionals. SLA printers are designed to use a laser that cures liquid resin into a toughened plastic a process called photopolymerization.

SLA printing has gained immense popularity for its capabilities of producing watertight, isotropic, and high-accuracy parts and prototypes using advanced materials with better surface quality and fine features.

Stereolithography offers a wide variety of thermal, mechanical, and optical properties that match those of industrial thermoplastics and standard engineering.

Resin materials for printing are considered an excellent option for highly detailed prototypes that require smooth surfaces and tight tolerances, including patterns, moulds, and functional prototypes.

Today, SLA printers are commonly used in various industries, ranging from product design and engineering to jewellery, dentistry, manufacturing, education, and model making.

So, how would you choose the right 3D printing solutions for your business? Here are some factors to consider when comparing FDM vs SLA.

The Differences Between Fused Deposition Modelling And Stereolithography

The differences between fused deposition modelling and stereolithography can be broken down into three main areas:

  • The Materials Used
  • Printing Process Accuracy
  • Ease Of Use

The Materials Used

FDM Materials

In all types of 3D printing, the print quality highly depends on the materials used.

FDM 3D printers normally use an array of thermoplastic polymers, but they can also use composites that come from a filament. Both the thermoplastic and filament materials bases are cost-effective, although ultimately the material costs depend on the application for the parts, quality, and type of the part being produced.

There are also several experimental thin filament blends that work with FDM 3D printers to create parts with metal or wood-like surfaces. Other available materials include engineering materials such as TPU, Nylon, PA, high-performance thermoplastics, and PETG; however, only a few professional FDM printers support these materials.

SLA 3D Printing Materials

SLA technologies come with a more limited variety of materials that can be used for the 3D printing process.

These printers use photosensitive thermosetting plastics that come in the form of resin.

These resins are expensive and mainly made by SLA printer manufacturers. They are highly specialised and mostly used for specific applications such as in jewellery, dental modelling, or high-temperature applications.

Printing Process Accuracy

FDM Parts Accuracy

While the print accuracy will vary depending on the 3D printer used, FDM 3D printing generally offers good print quality with excellent dimensional accuracy for larger features.

However, with smaller features, the dimensional accuracy can be restricted and may not be consistent.

Selecting the right 3D printer can also be challenging since accuracy is also dependent on other various factors, including print speed, slicer, and calibration settings, and the materials used can also have an impact on accuracy depending on their shrinkage properties.

SLA 3D Printing Accuracy

SLA machines can achieve extremely fine resolutions.

Their dimensional accuracy is greater than that of other 3D printing technologies, and that makes SLA print the best choice for 3D printing which requires accuracy and surface finish on fine features.

Ease Of Use

FDM Ease of Use

The FDM process is fairly straightforward, which is why most hobbyist 3D printers use a form of filament fabrication and have become the go-to for anyone who wishes to use them in educational and open office spaces.

The parts will then come out clean and dry and, in most cases, post-processing simply involves the removal of the supports by easily breaking them off. Any remaining material can be stored in a hard plastic filament form to be used for the next print.

SLA 3D Printers Ease of Use

Although SLA machines can produce detailed printed parts with much smoother surfaces, working with SLA resins can make the process more complex as resin can be poisonous and requires the operator to use gloves, goggles, and more protective gear.

SLA parts also require additional post-processing. Firstly, the print needs to be washed to remove any excess resin, and then any supports are removed while taking caution not to get rid of any print features.

The last step involves an extra curing process using UV light to complete the part. Any remaining liquid resin material needs to be stored in a tray away from light. Once in the tray, it has a short shelf life. Due to the chemical-filled process, SLA printers only really work well in closed labs.

Advantages and Disadvantages of FDM And SLA

Advantages Of FDM Printing

One of the main advantages of FDM printing is the printing speed. With an FDM printer, you can easily produce a 3D print in several minutes or various hours, which shortens the lead times of the prototyping process.

With FDM 3D printers, you can also print larger objects, and the printers come with a scalable design, which results in a low cost-to-size ratio.

FDM also offers more choices as the printers accept many filament materials, including nylon, polylactic acid, polyethylene terephthalate glycol, and acrylonitrile butadiene styrene.

Disadvantages Of FDM Printing

The major disadvantage of FDM 3D printing is the lower resolution compared to other printing methods.

FDM comes with not only a thick layer height but also its final products are likely to feature rough surfaces that require post-processing for a smoother end product. The thick layer height also means that FDM is unlikely to be suitable for any parts that have small details.

Although you can improve the appearance of the final product through gap filling, epoxy adhesion, and vapour smoothing, these processes will end up lengthening the production time.

FDM printing also requires support structures within the models, which can result in more time, material, and post-processing than when using another process that doesn’t require the same level of support.

Advantages Of SLA Printing

SLA 3D printing uses laser technology for increased accuracy, allowing for higher tolerance parts that come with enhanced resolution as compared to other technologies.

With SLA 3D prints, you can even achieve a higher print quality with resolutions as small as 25 microns. The final object is a smooth and detailed surface that looks like injection moulded parts.

SLA printers are the best option for proof of work or presentation models, complicated geometric parts, organic structures, and figurines, among other unique prototypes.

Also, due to their use of UV laser technology, the end product is not only extremely accurate but comes with more robust dimensional tolerances.

The process eliminates thermal expansion while the layers fuse, which makes it best suited for prototypes that require extreme accuracies, such as medical implants, complex architectural models, or small components.

Disadvantages Of SLA Printing

While SLA can produce beautiful models, they are structurally weaker than those made by other 3D printing methods. Although some SLA materials are designed to give better results in certain cases, it is a challenge to replicate similar mechanical properties of nylon and ABS, among other FDM filaments.

Since the cured resin material comes with brittle features, you can only use engineering-grade SLA resin formulations for cyclical loads and any parts that have to bear mechanical stress. However, most standard resins can be used for intricate and detailed structures meant for presentation use, including cosmetic prototypes.

SLA printing resin is also more expensive and gives you fewer parts per resin unit compared to FDM printing filament spools, and the printers come with smaller build volume in comparison with FDM printers, which is not ideal for high-volume jobs.

FDM vs SLA Printers

When it comes to choosing between FDM and SLA, you need to consider the benefits of each and what kind of printing work you have to do.

If your prototypes have finer features or are going to be used in the medical or dental sectors, then SLA is likely to be the better choice.

On the other hand, FDM printers are more versatile for production process parts for use in anything from maintenance to manufacturing.

If you’re unsure about which printing method would be best suited for your parts, get in touch today.

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