SLS vs FDM 3D Printing Comparison. Which to Choose & Why?

by Mike Brooks | Last Updated: June 25, 2022

The Selective Laser Sintering (SLS) and the Fused deposition modeling(FDM) are additive manufacturing technologies.

Additive manufacturing is a manufacturing process that creates functional prototypes and other objects, one material layer after the other.

SLS vs FDM Technology

Because SLS and FDM use the same manufacturing technology, you need to compare and contrast the two to identify their similarities and differences.

The Selective Laser Sintering printing process uses lasers as a power source that sinters and compacts powdered material into solid 3D model structures.

How does it work? The SLS printer aims lasers at parts defined by a 3D model. The lasers fuse the powdered material to form a solid 3D structure.

For its part, Fused deposition modeling (FDM) or Fused Filament Fabrication (FFF) refers to an additive 3D printing process that uses a thermoplastic filament material.

The filament moves into the extruder hot end before its deposition as molten plastic, layer by layer, on the build platform until the process is complete.

What Does SLS Stand for in 3D Printing?

Selective Laser Sintering

Selective Laser Sintering (SLS) produces functional solid prototypes and parts.

It is an additive manufacturing process where the SLS machine uses a high-power laser to heat tiny particles of plastic, ceramic, or glass, fusing them to form a solid 3D structure.

How SLS Printing Process Works

SLS Pre-Processing

Pre-processing is the first stage of the SLS 3D printing process.

Pre-processing takes care of any anticipated challenges during the printing process. For example, designers alter CAD programs that incorporate 3D objects with sharp edges and thin walls.

These alterations are essential as SLS 3D printing sharp edges and thin walls are unsuitable.

Step by Step SLS Processing

As an additive manufacturing process, SLS works in the following way;

• You’ll need to design your 3D model using the Computer-Aided Design (CAD) Program.
• Divide the design into thin 2D layers
• The CAD Program communicates the split 2D layers design to the SLS printer.
• Next, use a leveling roller to spread the layer thickness of powdered material on the print bed.
• After, a carbon dioxide laser traces a cross-section of the powdered material in the build platform, heating and fusing it.
• Upon completion of a layer thickness, the printer lowers the print bed to allow printing the next layer of powder.
• Recycle excess powder and waste material after completion of each layer
• Ultimately, you’ll repeat the SLS printing process by building layer after layer until you complete printing your 3D model.

SLS Post Processing

Post-processing is vital as it marks the part recovery stage. SLS 3D printing process covers the printed parts with support material. To get your final 3D printed model, break these porous cocoons covered with sintered powder.

To remove the support material during post-processing, break and open the support structures using a specially designed cleaning chamber or compressed air.

Finally, you need to dye and coat the SLS 3D printed model to prepare them for use.

What Are SLS and FDM?

SLS Technology

Selective Laser Sintering(SLS) uses a laser beam to heat up and build complex geometries from tiny particles of powder, preferably nylon. SLS prints by fusing polymer powder bonding it to form a solid 3D structure.

Advantages of SLS Technology

• High revolution levels
• Fast lead times
• High tensile strength and stiffness
• A wide range of material selection

Disadvantages of SLS Technology

• SLS 3D products are brittle
• Difficult post-processing

FDM (Fused Deposition Modeling) Technology

Fused Deposition Modeling (FDM) technology uses plastic filament as its primary building material in functional prototyping and creating 3D anatomical models.

FDM desktop machines prints complicated geometry designed 3D models using the CAD program. It would be best to put the FDM desktop printer in a workshop environment with sufficient ventilation.

More importantly, FDM printers print cost-effective 3D objects. FDM works through the extruder hot end extruding layer by layer of molten plastic on the heated print bed. It repeats the process until it completes printing the 3D solid mass.

Advantages of FDM Technology

• Affordable printers
• Use inexpensive and widely available material
• use precise coding to create quality 3D models
• Print durable objects
• Easy to operate FDM printer
• FDM printers are faster

Disadvantages of FDM Technology

• Minimum complexity in feature details
• You must use it in a highly ventilated space or room
• Important to calibrate the FDM printer appropriately
• Print quality varies depending on printer quality

Is FDM Faster Than SLS?

Comparing the speeds of these two benchtop industrial systems enables you to determine your choice if you need to 3D print objects in the shortest time possible.

The HP-made Multi-jet fusion 3D printer remains one of the fastest 3D printing technologies. As for the FDM printer, its speed averages 100 mm/h.

Therefore, it can deposit an average of 100 mm of plastic material per hour of operation.

On the other hand, the SLS 3D printer is slower than the FDM printer. It can only go up to 48 mm/h, meaning that it would have deposited 48 mm of molten plastic filament after an hour of operation.

Which Is Better SLS or SLA?

Stereolithography (SLA) remains the most common resin 3D printing technology. Also, hobbyists like using it because it can produce high-accuracy and watertight prototypes.

At the same time, it creates end-use parts with isotropic mechanical properties.

Additionally, SLA uses a range of advanced printing materials with delicate features and a smooth surface finish.

How Does SLA Work?

SLA printing works by positioning the build platform in the liquid resin polymer tank. You need to set the build platform at a distance of one layer height above the liquid surface.

Then, a UV laser beam creates the following layer thickness by selectively curing the photopolymer resin.

You’ll repeat the SLA process until the 3D object completes printing.

Advantages of SLA Printing Method

• Smooth surface finish
• Excellent for use in miniature printing
• Short lead time
• Offers a wide range of material choice
• Quite portable
• Prints compact objects

Disadvantages of SLA 3D Printing Technology

• Costly method
• Not recyclable
• Needs after-print curing
• Can’t print larger objects

SLA vs SLS

Both the SLA and SLS are additive manufacturing processes. Also, SLA is perfect for printing complex and minor features.

Still, SLS has a unique advantage over SLA in that it has surrounding unsintered powder that acts as support materials to the parts during 3D printing.

Both printing methods require post-processing material recovery. Equally, you can machine, sand, and paint finished 3D models in the same way, using either printing method.

Sanding and painting help you achieve a smooth surface as it removes signs of layers along the layer lines of the print surface.

Why Is FDM Popular?

Fused Deposition Modeling (FDM) technology uses thermoplastic filaments to create 3D printed parts.

Thermoplastics withstand chemicals, heat, and high mechanical stress making the ideal and most sought-after material for building functional prototypes that can cope with high-stress levels.

It is the preferred choice of engineers who want to create interlocking forms that encourage more fluent movements in mechanical parts.

Still, FDM parts need moderate training to build more complex additive processes requiring specialized training like printing the SLS parts.

What Are the Benefits of FDM?

Fused Deposition Modeling (FDM) offers 3D printing users several benefits;

Scalability

The only limiting factor to the scalability of your FDM printer is your build platform size and the length of the 3D printer’s arm. In other words, scalability is only limited to the size of your FDM 3D printer.

Ease of Use

FDM 3D printing technology is not complicated. You only require moderate training to handle the FDM machine operation.

You only need to calibrate your printer with the correct settings, and you’re good to go. Often, the manufacturer would have calibrated your FDM 3D printer at the time of purchase.

Connect the suitable plastic filament to the extruder as provided in the printer user manual and press the print tab to start printing.

Affordability

FDM 3D printers remain one of the most commonly used and affordable printers in the market. It enjoys a significantly lower entry cost compared to SLA 3D printers.

At the same time, the filament used is readily available hence providing you with a wide range of material choices.

Because of its ease of use, training for printer users remains cost-effective. Thus, attracting more hobbyists to the 3D printing industry.

What Is the Difference Between SLS and SLA?

Both the SLA and SLS printing techniques use the additive process. However, they differ in several ways;

SLA works purely with polymers and resins. It doesn’t print with metals. But SLS works with a couple of polymers like polystyrene and nylon and can also handle metals like titanium and steel.

SLS 3D printing technology uses a high-powered laser to aim and heat tiny powdered particles of nylon put in the build platform to melting temperature before solidifying it to a 3D model.

In SLA 3D printing, you first position the build platform in the tank containing liquid photopolymer.

The laser then creates layer after layer. Every time you complete printing a layer, you adjust the build platform by a layer height to enable the printing of the next layer.

SLS is more robust and lower in cost compared to SLA technology.

However, SLA produces 3D printed objects with tighter dimensional tolerance and better smooth surfaces similar to injection molded parts.

SLA can create small and well-defined features, something that is not easy to achieve when SLS 3D printing

SLS surrounding powder supports the printed layers, making them stable as the printing continues. Conversely, the SLA 3D printing technology requires that you have additional support structures instead.

When to Use FDM or SLS?

If you don’t have a big budget for your 3D printing needs, it would be helpful to opt for FDM 3D printing technology as it is cheaper than the SLS method.

Also, if you intend to get a printer that is easy to use and widely available on desktops, the FDM 3D printing printer fits the bill.

Equally, if you need a printer that prints faster, choose an FDM 3D printer over an SLS printer.

However, if you want to discard the need for using additional support structures that come at a cost, you’ll choose the SLS 3D printer.

It uses the excess powder in the build setup to support material for objects during the printing process.

SLS offers a better option if you need stiffness and high tensile strength in your printed parts.

Conclusion

The article provides you with a comprehensive guide on SLS vs FDM printing technologies. You now only need to choose the one that best suits your needs.

FDM uses the extruder hot end to deposit layer by layer of molten plastic on the printer bed until printing while SLS uses a laser beam to heat powdered nylon following a unique geometry and a powder bed.

It then solidifies it using liquid resin to form a robust 3D structure.

Michael Brooks is the founder of M3DZone.com. He sees a very bright future for 3D printing that's why his mission is to try and make this easy for everyone. Discover your hidden talent and creativity. You can follow here: Facebook, Twitter & Pinterest.