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Complete guide to Selective Laser Sintering (SLS)

Introduction

The wide range of 3D printing materials and its excellent mechanical properties makes the  Selective Laser Sintering (SLS) technology attractive for businesses. Discover what selective laser sintering is, sometimes referred to as SLS 3D printing. Learn how SLS 3D printing functions and how this technology can help your business, either for rapid prototyping or small-run manufacturing.

What is Selective Laser Sintering 3D printing technology?

SLS (Selective Laser Sintering) is an additive manufacturing method. It creates parts additively by sintering fine polymer powder particles to fuse them locally. Your plastic piece will be created layer by layer, according to your 3D model. 

Now, a little bit of history. One of the earliest additive manufacturing techniques was SLS 3D printing. It was created in the 1980s at the University of Texas in Austin by Dr. Carl Deckard and Dr. Joe Beaman. To build the powder bed fusion technologies we are familiar with today, the manufacturing techniques they developed had to be modified to work with various 3D printing materials, including plastics, metals, glass, ceramics, and different powders of composite materials.

How SLS 3D printing works?

Let’s dive into more details to understand this direct digital manufacturing technique. To make it simpler for the laser to raise the temperature of the chosen regions to the melting point, the SLS machine preheats the bulk powder material in the powder bed just below its melting point during the 3D printing process. A layer of polymer powder will be applied with a roller, followed by the laser sintering of the powder by the 3D file (usually an STL file) and the build platform lowering before a new layer of powder is applied. Until the desired part is produced, the process will be repeated.

Selective Laser Sintering (SLS), in contrast to other additive manufacturing techniques like stereolithography (SLA), fused deposition modeling (FDM), or fused filament fabrication (FFF), does not require support structures because the powder works as a self-supporting material. This makes it possible to create complex geometries.

1 – Prepare your 3D file

The first step to start your 3D printing process is to create a digital 3D model of the part you need to create physically. You can do this by using a 3D modeling software to create your object. Discover our selection of free CAD software to develop your project.

Preparing your 3D file for 3D printing with SLS is crucial; you have to create a printable 3D file. As a 3D printing service, we see a lot of unique 3D printing projects, but we also see a lot of errors rendering some files non-printable. It’s possible for your file to be printable but your part can break in no time, be deformed, or not come out of the 3D printer as expected. In this article, we will help you with 3D printing troubleshooting for the most common 3D printing mistakes

2- Get the Selective Laser Sintering 3D printer ready to print

If you have your own SLS 3D printer, an operator must get the printer ready; the parameters differ depending on the system. Most conventional SLS systems involve significant preparation, equipment, and physical labor.

If you don’t have your own SLS 3D printer, you can use an online 3D printing service such as Sculpteo and any technical preparation will be done for you by our operators.

3- 3D printing process

Once all preprint checks have been made, the printer is prepared to print. Depending on the parts’ size, intricacy, and density, the SLS process can take anywhere from a few hours to a few days.

The build chamber must quickly cool inside the print enclosure once the print is finished before restarting. After that, the build chamber may be removed and a new one placed to run another pattern. The build chamber must cool down before post-processing to guarantee excellent mechanical properties and avoid any warping. 

4- Post-processing

If we compare it to other 3D printing methods, SLS requires the least time and effort for post-processing. SLS parts do not require support, making it easier to scale and produce consistent batches of parts.

An operator removes the finished components from the build chamber once a print job is finished, separates them, and clears away any extra powder. This procedure is carried out manually using pressurized air or a media blaster. 

Other post-processes can then be applied to the 3D-printed parts, such as polishing, dyeing, and many more.

What is Selective Laser Sintering used for?

If you want to improve your product development process, Selective Laser Sintering (SLS) is a great option. Since this 3D printing technology has many advantages for designers and engineers, it could be an excellent opportunity to try out efficient designs and manufacturing processes for your projects! 

Selective Laser Sintering process offers many different 3D printing materials allowing you to choose the material properties that best fit your projects. Medical tools, consumer goods, drones, robotics, specialized machinery, orthopedic technology, educational institutions, jigs, fixtures, or even promotional items: 3D printing can help you with these and many more. The additive manufacturing technique allows for the production of all the pieces you’ll need, from functional prototyping to mass production.

  • Rapid prototyping

SLS is a perfect ally for your rapid prototyping process. As this technique allows production parts close to the end-use quality, with a high degree of precious and sound design freedom, it is ideal for functional prototyping. You will be able to produce concept models and parts ready for testing. With SLS, complicated designs may be prototyped.

Technologies such as FDM or SLA, using little 3D printers, will provide parts with a low level of detail or high fragility. Otherwise, affordable options such as raw Nylon PA12 offer an attractive quality/price ratio. 

  • Low production run

Additive manufacturing is more often used for production. Selective Laser Sintering is an exciting technique to produce end-use parts and now represents a serious alternative to injection molding for production. It is possible to make parts with complex shapes and geometries, and features with interesting mechanical properties. 

You can also add surface treatments to your parts to get fantastic results. Thanks to the rapid evolution of post-processing, new finishes are constantly being released to give the desired look to your 3D-printed project.  

What are the SLS materials available?

Several parameters, including powder characteristics such as particle size and shape, density, roughness, and porosity, affect the quality of printed structures. The powder-based components utilized in SLS include polymers such as polyamides (PA), polystyrene (PS), thermoplastic elastomers (TPE), and polyaryletherketones (PAEK). Due to their perfect sintering behavior as a semi-crystalline thermoplastic, polyamides are the most often utilized SLS materials, producing components with desired mechanical qualities.

Sculpteo’s online 3D printing service offers a large variety of materials printed with Selective Laser Sintering for both functional prototyping and end-use production. Here are all the industrial printing materials we offer using SLS:

  • Nylon PA12: A versatile material, the most popular SLS material.
Nylon PA12
  • PA12 (grey): A grey version of the Nylon PA12 material.
Nylon PA11 12

Nylon Glass Filled

  • Alumide: A SLS material made with a blend of polyamide powder and fine aluminum particles.

Alumide

  • Ultrasint® PA11 CF: A bio-derived material with high flexibility, impact performance, and rigidity. 

  • Ultrasint® PA11 ESD: Another PA11 material with electrostatic discharging properties for increased process safety in advanced applications.

  • Ultrasint® PA6 MF: A reinforced PA6 combining superior thermal resistance with high isotropic rigidity.

 

What are the different SLS 3D printers available?

A wide range of SLS 3D printing machines are available on the market. Here are some of the most used Selective Laser Sintering 3D printers.

  • EOS Formiga
  • Prodways Propmaker
  • Sinterit
  • Formlab Fuse

However, these industrial 3D printers are expensive (from 20,000$ to 650,000$). If you are not willing to invest in such vital equipment to make your first 3D printing projects, prototypes, or small & medium production series, you can benefit from a 3D printing service to get your SLS parts. 

What are the advantages of SLS for your 3D printing projects?

There are very few disadvantages when it comes to using Selective Laser Sintering. This 3D printing technology offers flexibility with a wide range of materials. Among the most common SLS advantages, you will find:

  • Freedom of design

With Selective Laser Sintering, you can push the limits of production with the help of this technology, and you won’t be limited by the structural and design limitations of conventional manufacturing methods. Your parts can be modified to meet the needs and specifications of your company.

SLS is capable of creating parts with complex geometries. In this regard, the process allows you to create pieces with intricate designs that may have been difficult or impossible to manufacture by traditional manufacturing methods. Moreover, a key advantage of SLS 3D printing is that it needs no support structures. Indeed, with SLA or FDM 3D printing techniques, support might be required, which is not the case with powder-bed technologies.

  • Rapid manufacturing

Rapid manufacturing is one of the most exciting advantages of the Selective Laser Sintering (SLS) process. Traditional manufacturing techniques, such as injection molding, can’t compete with the short lead time that these SLS machines can provide. Using SLS will allow you to iterate or create parts on-demand in a short amount of time. 

  • Good mechanical properties

Parts manufactured with this technology have good mechanical properties, making them ideal for functional parts and prototypes. SLS is capable of creating parts with high strength and durability. For example, here are some specifications of our most versatile material, Nylon PA12: 

Tensile modulus (N/mm2): 1700 ± 150

Tensible strength (N/mm2): 45 ± 3

Elongation at break (%): 20 ± 5

  • High productivity

Selective Laser Sintering is excellent for producing end-use products for small or medium series. Thanks to high-performance materials and advanced post-processing, you will get the possibility of creating end-use parts.

  • Discover a natural ally for your supply chain

The use of this powder-bed technology can ultimately enhance your supply chain. You can produce your parts using additive manufacturing exactly when you need them, eliminating the requirement for a warehouse and inventory. You can rethink this procedure and obtain a digital list by producing on-demand parts. 

What are Selective Laser Sintering’s characteristics?

SLS 3D printing process offer great possibilities in terms of precision, shape and size for your 3D printed parts. Here are some characteristics for Nylon PA12. All SLS materials don’t have the same characteristics, make sure you check the design guidelines of the material your need to use before you order your parts!

Standard layer thickness: 100 – 120µm

Accuracy: ± 0.3% (minimum of ± 0.3 mm)

Maximum size (for white/unpolished parts): 675 x 366 x 545 mm

What are the the post-processing options got SLS 3D printing?

One of the strengths of SLS technology is the possibility to improve your 3D printed objects to a high standard using various post-processings, from polishing to dyeing. These finishing techniques are unavailable for all SLS materials; check out the compatibility between the post-processing and the material you need for your project.

  • Chemical smoothing: Chemical Smoothing allows for a smoother surface on plastic parts. This unique process enables a chemical reaction that creates a fully smoothed surface on your 3D-printed polyamide parts.
  • Polishing: Polishing is a process that makes the objects smoother to the touch, with layers that are still somewhat visible on rounded objects. At Sculpteo, the technique involves using small stones in a rotating/vibrating cauldron.
  • Painting: Painting is exclusively available for white plastic and cannot be applied to interlocking parts. The painting process gives color to the material in any available paints with specific RAL. The colors are spread on the fabric using a spray gun, allowing a uniform and smooth surface while maintaining every detail of the printed object: the paint layer only adds 200 microns of thickness on average.
  • Dyeing: The parts are immersed in a heated dye bath before drying. Dyeing reaches all part surfaces, including the most inaccessible recesses, resulting in a uniform finish.
  • Color Touch: This finish gives your 3D-printed parts a satin look so that they look like finished products. Applying the Color Touch finish on your 3D parts, they get resistant enough to be exposed to external conditions; they resist scratching and rubbing.
  • Color Resist: This post-processing gives your 3D-printed parts a matte look that resists friction. Thanks to the post-printing treatment procedure we follow before applying the Color Resist finish on your 3D parts; they get resistant enough to be exposed to external conditions and resist scratching and rubbing. 

Finish touch

Going further: What are other 3D printing technologies available for your projects ?

Multi Jet Fusion is the best alternative to SLS. HP invented the additive manufacturing process known as multi-jet fusion. It uses a multi-agent printing approach to manufacture pieces in an additive manner. A fusing agent is used in this procedure to fuse the particles where they are required by coating a material layer with it. Using a detailing agent, the fusing is then modified to produce fine features and smooth surfaces. Reactions between the agents and the component material are caused by the region exposed to energy.

Indeed, MJF and SLS are similar; they are both part of the powder bed technologies. But there are some differences regarding the printing process, materials available, surface finish options, and mechanical properties. MJF vs. SLS, discover the differences and advantages of these two 3D printing technologies.  

TPU

Are you willing to use Selective Laser Sintering ?

Benefit from Sculpteo’s expertise 

Upload your 3D file, choose your SLS material and get your instant quote! For your plastic parts, Sculpteo offers the best online 3D printing services. You may select from several polymers and coatings, obtain a price right away, and let us manage the manufacture in our ISO 9001-certified plant thanks to our knowledge of SLS technology. Contact our 3D printing experts if you have questions about SLS and all the possible applications. 

They use Selective Laser Sintering to 3D print their parts with us!

  • WE ROBOTICS creates cargo drones with professional quality thanks to Nylon PA12.
The goal of the cargo drone project is to develop a low-cost freight-transporting add-on module for consumer drones. WeRobotics was able to satisfy all of its production needs while being cost-effective, thanks to Sculpteo, with a little time commitment and a professional quality and surface finish. Discover their story
  • KOOVEA develops reliable sensors with Nylon PA12
To join the market with top-notch goods and technology, Koovea looked into 3D printing. Koovea underwent a rigorous iterative development approach to develop its temperature sensors to produce a trustworthy solution for its goods. Discover their story.
  • Daniel Robert Orthopedics uses 3D printing and Ultrasint® PA11 to create unique eco-responsible orthopedic devices.
To provide a distinctive and personalized device that promotes comfort, breathability, and lightness while keeping manufacturing and design flexibility, Daniel Robert Orthopedics investigated 3D printing. Discover their story.
  • GENERATION ROBOTS uses on-demand manufacturing to meet customers’ needs
The most well-known robot, Poppy Humanoid, comprises 33 different 3D-printed parts that can be altered to suit the customer’s needs. Generation Robots need an on-demand manufacturing solution to satisfy clients’ unique markets with a constantly evolving robot like Poppy. Discover their story!

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