(506) 2240-6804
Sls 3d printing materials
Guide to Selective Laser Sintering (SLS) 3D Printing
Selective laser sintering (SLS) 3D printing is trusted by engineers and manufacturers across different industries for its ability to produce strong, functional parts.
In this extensive guide, we’ll cover the selective laser sintering process, the different systems and materials available on the market, the workflow for using SLS printers, the various applications, and when to consider using SLS 3D printing over other additive and traditional manufacturing methods.
White Paper
Looking for a 3D printer to create strong, functional parts? Download our white paper to learn how SLS printing works and why it's a popular 3D printing process for functional prototyping and end-use production.
Download the White Paper
Selective laser sintering is an additive manufacturing (AM) technology that uses a high-power laser to sinter small particles of polymer powder into a solid structure based on a 3D model.
SLS 3D printing has been a popular choice for engineers and manufacturers for decades. Low cost per part, high productivity, and established materials make the technology ideal for a range of applications from rapid prototyping to small-batch, bridge, or custom manufacturing.
Recent advances in machinery, materials, and software have made SLS printing accessible to a wider range of businesses, enabling more and more companies to use these tools that were previously limited to a few high-tech industries.
Introducing the Formlabs Fuse Series SLS 3D printers, bringing high-performance SLS 3D printing finally within reach.
Webinar
Watch our product demo for a walkthrough of the Fuse 1+ 30W and SLS 3D printing with Formlabs experts.
Watch the Webinar
Schematic of the selective laser sintering process. SLS 3D printing uses a high-power laser to sinter small particles of polymer powder into a solid structure based on a 3D model.
-
Printing: The powder is dispersed in a thin layer on top of a platform inside of the build chamber. The printer preheats the powder to a temperature somewhat below the melting point of the raw material, which makes it easier for the laser to raise the temperature of specific regions of the powder bed as it traces the model to solidify a part. The laser scans a cross-section of the 3D model, heating the powder to just below or right at the melting point of the material. This fuses the particles together mechanically to create one solid part. The unfused powder supports the part during printing and eliminates the need for dedicated support structures. The platform then lowers by one layer into the build chamber, typically between 50 to 200 microns, and the process repeats for each layer until parts are complete.
-
Cooling: After printing, the build chamber needs to slightly cool down inside the print enclosure and then outside the printer to ensure optimal mechanical properties and avoid warping in parts.
-
Post-processing: The finished parts need to be removed from the build chamber, separated, and cleaned of excess powder. The powder can be recycled and the printed parts can be further post-processed by media blasting or media tumbling.
For the detailed workflow, see the “The SLS 3D Printing Workflow” section below.
SLS parts have a slightly grainy surface finish, but almost no visible layer lines. Media blasting or media tumbling SLS parts is recommended for a smoother surface finish. This example part was printed on a Formlabs Fuse 1+ 30W benchtop industrial SLS 3D printer.
As the unfused powder supports the part during printing, there’s no need for dedicated support structures. This makes SLS ideal for complex geometries, including interior features, undercuts, thin walls, and negative features.
Parts produced with SLS 3D printing have excellent mechanical characteristics, with strength resembling injection-molded parts.
Sample part
See and feel Formlabs quality firsthand. We’ll ship a free SLS sample part printed on the Fuse 1+ 30W to your office.
Request a Free Sample Part
FDM vs SLA vs SLS: Compare selective laser sintering (SLS) 3D printing to two other common 3D printing processes for producing plastic parts: fused deposition modeling (FDM) and stereolithography (SLA).
Selective laser sintering was one of the first additive manufacturing techniques, developed in the mid-1980s by Dr. Carl Deckard and Dr. Joe Beaman at the University of Texas at Austin. Their method has since been adapted to work with a range of materials, including plastics, metals, glass, ceramics, and various composite material powders. Today, these technologies are collectively categorized as powder bed fusion—additive manufacturing processes in which thermal energy selectively fuses regions of a powder bed.
The two most common powder bed fusion 3D printing systems today are plastic-based, commonly referred to as SLS, and metal-based, known as direct metal laser sintering (DMLS) or selective laser melting (SLM).
Until recently, both plastic and metal powder bed fusion systems have been prohibitively expensive and complex, limiting their use to small quantities of high-value or custom parts, such as aerospace components or medical devices.
Innovation in the field has surged recently, and plastic-based SLS is now poised to follow other 3D printing technologies like stereolithography (SLA) and fused deposition modeling (FDM) to gain widespread adoption with accessible, compact systems.
All selective laser sintering 3D printers are built around the process described in the previous section. The main differentiators are the type of laser, the size of the build volume, and the complexity of the system. Different machines use different solutions for temperature control, powder dispensing, and layer deposition.
Selective laser sintering requires a high level of precision and tight control throughout the printing process. The temperature of the powder along with the (incomplete) parts must be controlled within 2 °C during the three stages of preheating, sintering, and storing before removal to minimize warping, stresses, and heat-induced distortion.
Selective laser sintering has been one of the most popular 3D printing technologies for professionals for decades, but its complexity, requirements, and high price have limited its use to service bureaus and large enterprises.
These machines require special HVAC and industrial power, and even the smallest industrial machines take up at least 10 m² of installation space. Setting them up takes multiple days with on-site installation and training. The complex workflow and the steep learning curve also mean that these systems require a skilled technician in-house to operate and maintain.
With a starting price of around $200,000 that goes well beyond that for complete solutions, traditional industrial SLS has been inaccessible for many businesses.
Just like with other 3D printing technologies like FDM or SLA, lower-cost, compact SLS systems have recently started to emerge on the market, but initially, these solutions came with considerable trade-offs, including lower part quality and complex, manual workflows resulting from the lack of post-processing solutions, which limited their use in industrial and production settings.
The Formlabs Fuse 1 bridged that gap and created its own category as the first benchtop industrial SLS 3D printer that offered high quality, compact footprint, and a complete, simplified workflow at a fraction of the cost of traditional industrial SLS systems. Now, the next generation Fuse 1+ 30W extends that category with a more powerful laser, improved powder handling features, and new material capabilities for industrial quality parts and high throughput.
The Fuse 1+ 30W requires no specialized infrastructure, and can easily fit into your workspace.
Fuse Series SLS 3D printers use a single laser and a smaller build chamber that requires less heating. The lower energy consumption means that they can run on standard AC power without requiring specialized infrastructure. An optional nitrogen feature for the Fuse 1+ 30W printer creates an inert gas environment, preserving the quality of the unsintered powder for a lower refresh rate (more recycled powder than new powder in consecutive builds), minimizing waste, and enabling a better surface finish on sintered parts.
Fuse Series printers also feature a patent-pending solution called Surface Armor—a semi-sintered shell that keeps the area around the parts evenly heated as they print, ensuring great surface finish, consistent mechanical properties, high reliability, and better refresh rates.
To offer a compact, contained ecosystem and end-to-end powder handling, Fuse Series printers also come with the Fuse Sift, which combines part extraction, powder recovery, storage, and mixing in a single free-standing device.
Overall, benchtop industrial SLS 3D printing with Fuse Series printers offers a slightly smaller build volume compared to the entry-level traditional SLS systems, in return for a substantially smaller footprint, simplified workflow, and lower cost.
| Fuse Series: Benchtop Industrial SLS 3D Printers | Traditional Industrial SLS 3D Printers | |
|---|---|---|
| Price | Starting at $18,500 for the Fuse 1, $28,000 for the Fuse 1+ 30W | $200,000-$500,000+ |
| Print Volume | Up to 165 x 165 x 300 mm | Up to 550 x 550 x 750 mm |
| Pros | Affordable High-quality parts High throughput Multiple material options Simplified workflow Small footprint Low maintenance | Large build volume High-quality parts High throughput Multiple material options |
| Cons | Smaller build volume | Expensive machinery Large footprint Facility requirements High maintenance Requires a dedicated operator |
The comparison is based on the Formlabs Fuse Series benchtop industrial SLS system and traditional industrial SLS systems by EOS and 3D Systems.
A drill prototype printed on the Fuse 1+ 30W (left) and on an EOS printer (right), with comparable quality but a vastly different machine price point.
White Paper
In this white paper, we evaluate the value proposition of bringing SLS 3D printers in-house, in comparison with outsourcing SLS parts from a service bureau.
Download the White Paper
The most common material for selective laser sintering is nylon, a highly capable engineering thermoplastic for both functional prototyping and end-use production. Nylon is ideal for complex assemblies and durable parts with high environmental stability.
SLS 3D printed nylon parts are strong, stiff, sturdy, and durable. The final parts are impact-resistant and can endure repeated wear and tear. Nylon is resistant to UV, light, heat, moisture, solvents, temperature, and water. 3D printed nylon parts can also be biocompatible and not sensitizing, which means that they are ready to wear and safe to use in many contexts.
Nylon is ideal for a range of functional applications, from engineering consumer products to healthcare.
Nylon is a synthetic thermoplastic polymer that belongs to the family of polyamides. It is available in multiple variants, each tailored to different applications. Nylon 12 Powder and Nylon 11 Powder are single-component powders, while Nylon 12 GF Powder is a glass-filled composite, and Nylon 11 CF Powder is a carbon fiber reinforced composite. These composite materials are developed to optimize parts for higher strength, stiffness, or flexibility. With these two-component powders, only the component with the lower glass transition point is sintered, binding both components.
- High performance prototyping
- Small batch manufacturing
- Permanent jigs, fixtures, and tooling
- General SLS parts
- Impact-resistant prototypes, jigs, and fixtures
- Thin-walled ducts and enclosures
- Snaps, clips, and hinges
- Orthotics and prosthetics*
- Robust jigs and fixtures and replacement parts
- Parts undergoing sustained loading
- Threads and sockets
- Parts subjected to high temperature
- Replacement and spare alternatives to metal parts
- Tooling, jigs, fixtures
- High-impact equipment
- Functional composite prototypes
* Material properties may vary based on part design and manufacturing practices.
It is the manufacturer’s responsibility to validate the suitability of the printed parts for the intended use.
| Materials | Nylon 12 Powder | Nylon 11 Powder | Nylon 12 GF Powder | Nylon 11 CF Powder |
|---|---|---|---|---|
| Ultimate Tensile Strength X (MPa) | 50 | 49 | 38 | 69 |
| Ultimate Tensile Strength Y (MPa) | N/A | N/A | N/A | 52 |
| Ultimate Tensile Strength Z (MPa) | N/A | N/A | N/A | 38 |
| Tensile Modulus X (MPa) | 1850 | 1600 | 2800 | 5300 |
| Elongation at Break, X/Y (%) | 11 | 40 | 4 | 9 / 15 |
| Elongation at Break, Z (%) | 6 | N/A | 3 | 5 |
| Notched Izod (J/m) | 32 | 71 | 36 | 74 |
SLS 3D printing accelerates innovation and supports businesses across a wide range of industries, including engineering, manufacturing, and healthcare.
Take control of your entire product development process, from iterating on your first concept design to manufacturing ready-to-use products:
- Rapid prototyping
- Mockups of products for in-field customer feedback
- Functional prototyping
- Rigorous functional testing of products (e.g. ductwork, brackets)
Own your supply chain and respond quickly to changing demands:
- End-use part production
- Small batch, stop-gap, and bridge manufacturing
- Mass customized consumer products
- Replacement parts, aftermarket parts, spare parts
- Long-lasting, durable manufacturing aids, jigs and fixtures (e.g clips and clamps) and tooling
- Custom automotive or motorcycle parts, marine equipment, military ‘resupply on-demand’
Manufacture ready-to-use, patient-specific medical devices in-house:
- Medical device prototyping
- Prosthetics and orthotics (i.e. limb replacements + braces)
- Surgical models + tools
- End-use parts (Nylon 12 Powder is biocompatible + compatible with sterilization*)
* Material properties may vary based on part design and manufacturing practices.
It is the manufacturer’s responsibility to validate the suitability of the printed parts for the intended use.
White Paper
This white paper showcases the cost-dynamics for real-life use cases, and presents guidelines for using SLS 3D printing, injection molding, or both.
Download the White Paper
Webinar
In this webinar, learn how affordable industrial-quality SLS 3D printers are making additive manufacturing a viable choice for end-use production and mass customization.
Watch the Webinar Now
Watch this video to see the step by step process of using the Fuse 1 selective laser sintering (SLS) 3D printer and the Fuse Sift powder recovery station.
Use any CAD software or 3D scan data to design your model, and export it in a 3D printable file format (STL or OBJ). Each SLS printer includes software to specify printing settings, orient and arrange models, estimate print times, and slice the digital model into layers for printing.
Once setup is complete, the print preparation software sends the instructions to the printer via a wireless or cable connection.
Fuse Series printers use PreForm print preparation software (free to download) that allows you to seamlessly duplicate and organize multiple parts within a 3D grid to use as much of the build space as possible for a single print. PreForm automatically suggests optimal orientation and part packing, with the ability to manually refine as needed.
The workflow for preparing the printer varies by system. Most traditional SLS systems require extensive training, tools, and physical effort to prepare and maintain.
Fuse Series printers reimagine the SLS workflow for simplicity and efficiency, with modular components to enable nonstop printing and end-to-end powder handling.
On Fuse Series printers, you can load powder easily using the powder cartridge.
Fuse Series printers use a removable build chamber so you can run another print while a previous one is still cooling.
Once all preprint checks have been completed, the machine is ready to print. SLS 3D prints can take anywhere from a few hours to multiple days depending on the size and complexity of parts, as well as the part density.
Once the print is finished, the build chamber needs to slightly cool down in the print enclosure before moving to the next step. After that, the build chamber can be removed and a new one inserted to run another print. The build chamber has to cool down before post-processing to ensure the optimal mechanical properties and avoid warping in parts. This may take up to half of the print time.
On Fuse Series printers, the touchscreen displays a live stream of the print bed during printing so you can watch each new layer take shape. This camera view is also available from your computer in PreForm so you can monitor your print without leaving your desk.
Post-processing SLS parts requires minimal time and labor compared to other 3D printing processes. It is easily scalable and yields consistent results for batches of parts thanks to the lack of support structures.
After a print job is complete, remove the finished parts from the build chamber, separate them, and clean them of excess powder. This process is typically completed manually at a cleaning station using compressed air or a media blaster.
Any excess powder remaining after part recovery is filtered to remove larger particles and can be recycled. Unfused powder degrades slightly with exposure to high temperatures, so it should be refreshed with new material for subsequent print jobs. This ability to re-use the material for subsequent jobs makes SLS one of the least wasteful manufacturing methods.
A common theme in the SLS industry is to offer separate devices for reclaiming, storing, and mixing powder. In the Fuse Series workflow, a single device, Fuse Sift, handles the extraction of parts and unsintered powder, as well as storing, dosing, and mixing of streams.
For Fuse Series printers, Fuse Sift completes the SLS printing workflow. It offers a safe and efficient system for extracting prints and recycling powder.
Fuse Sift can dispense and mix used and new powder automatically so you can reduce waste and control your powder supply.
SLS 3D printed parts are ready to use after sifting. However, there are several other post-processing steps that you might consider for selective laser sintered parts.
By default, SLS 3D prints have a grainy finish. Formlabs recommends media blasting or media tumbling SLS parts for a smoother surface finish. Parts may be spray painted, lacquered, electroplated, and coated to achieve different colors, finishes, and properties, for example, watertightness (coating) and conductivity (electroplating). Formlabs SLS parts are dark in color, so they are not ideal for dyeing.
SLS part with hydrographics from Partial Hand Solutions.
SLS parts can be electroplated for a metal-like finish.
Engineers and manufacturers choose selective laser sintering for its design freedom, high productivity and throughput, low cost per part, and proven, end-use materials.
Most additive manufacturing processes, such as stereolithography (SLA) and fused deposition modeling (FDM), require specialized support structures to fabricate designs with overhanging features.
Selective laser sintering does not require support structures because unsintered powder surrounds the parts during printing. SLS printing can produce previously impossible complex geometries, such as interlocking or moving parts, parts with interior components or channels, and other highly complex designs.
Hand splint designed with a complex pattern to reduce weight.
Engineers generally design parts with the capabilities of the final manufacturing process in mind, also known as design for manufacturing (DFM). When additive manufacturing is used for prototyping alone, it is limited to parts and designs that conventional manufacturing tools can ultimately reproduce during production.
As selective laser sintering becomes a viable rapid manufacturing method for an increasing number of end-use applications, it has the potential to unleash new possibilities for design and engineering.
SLS 3D printers can produce complex geometries that are impossible or prohibitively costly to manufacture with traditional processes. SLS also empowers designers to consolidate complex assemblies that would normally require multiple parts into a single part. This helps alleviate weak joints and cuts down on assembly time.
Selective laser sintering can take generative design to its full potential by enabling lightweight designs that employ complex lattice structures impossible to manufacture with traditional methods.
SLS printing is the fastest additive manufacturing technology for functional, durable prototypes and end-use parts. The lasers that fuse the powder have a much faster scanning speed and are more accurate than the layer deposition methods used in other processes like industrial FDM.
Multiple parts can be tightly arranged during printing to maximize the available build space in each machine. Operators use software to optimize each build for the highest productivity leaving only minimal clearance between parts.
SLS allows operators to pack the build chamber with as many parts it can fit and print them without supports to save time in post-processing.
The key to SLS 3D printing’s functionality and versatility is the materials. Nylon and its composites are proven, high-quality thermoplastics. Laser-sintered nylon parts have close to 100 percent density with mechanical properties comparable to parts created with conventional manufacturing methods like injection molding.
Drill assembly printed in Nylon 12 Powder. Nylon parts can be easily post-processed to achieve smooth, professional surface finishes.
SLS nylon is a great substitute for common injection molded plastics. It offers superior snap fits and mechanical joints compared to any other additive manufacturing technology. It is ideal for functional applications requiring plastic parts that will last where parts produced with other AM methods would degrade and become brittle over time.
Calculating cost per part usually requires accounting for equipment ownership, material, and labor costs:
-
Equipment ownership: The more parts a machine can produce over its lifetime, the lower the costs attributable to each individual part.
Consequently, higher productivity leads to lower equipment ownership costs on a per-part basis. Given the fast scanning speed of the laser, the nesting of parts to maximize build capacity, and simple post-processing, SLS 3D printing offers the highest productivity and throughput of all plastic additive manufacturing techniques. -
Material: While most 3D printing technologies use proprietary materials, nylon is a common thermoplastic produced in large quantities for industrial purposes, making it one of the least expensive raw materials for additive manufacturing. As SLS 3D printing doesn’t require support structures and allows for printing with recycled powder, the process produces minimal waste.
-
Labor: The Achilles heel of many 3D printing solutions is labor. Most processes have complex workflows that are hard to automate, which can substantially influence the cost per part. The simple post-processing workflow of SLS printing means less labor is required and the process is easy to scale.
An SLS 3D printer represents a substantial initial investment, but it can often recoup the initial investment even faster than smaller machines. Benchtop SLS significantly reduces this barrier to entry and also the per par cost for most applications.
Outsourcing production to service bureaus is recommended when your business requires 3D printing only occasionally, but it also comes with higher costs and long lead times. One of the greatest benefits of 3D printing is its speed compared to traditional manufacturing methods, which quickly diminishes when an outsourced part takes a week or even multiple weeks to arrive.
| Cost | Lead Time | |
| Service Bureau | $118.33 | 7-10 days |
| Fuse 1+ 30W | $9.02 | 13 hours |
Interactive
Try our interactive ROI tool to see how much time and cost you can save when 3D printing on Formlabs 3D printers.
Calculate Your Savings
Selective laser sintering enables engineers to prototype parts early in the design cycle, then use the same machine and material to produce end-use parts. SLS 3D printing does not require the same expensive and time-consuming tooling as traditional manufacturing, so prototypes of parts and assemblies can be tested and easily modified over the course of a few days. This drastically reduces product development time.
SLS 3D is ideal for creating durable, functional prototypes that are ready to undergo rigorous functional testing or to ship to customers as replacement parts or products that are ready to use.
Given its low cost per part and durable materials, SLS 3D printing is an economical way to produce complex, custom parts, or a series of small components for end products. In many cases, laser sintering is a cost-effective alternative to injection molding for limited-run or bridge manufacturing.
Until now, industrial SLS 3D printers have been prohibitively costly for most businesses, with a single machine running over $200,000.
With the Fuse 1+ 30W, Formlabs is bringing the industrial power of selective laser sintering to the benchtop, offering high-performance materials at the lowest cost per part, with a compact footprint and simple workflow.
A new wave of independent manufacturing and prototyping starts now with the Fuse 1+ 30W.
See the Fuse 1+ 30W Benchtop Industrial SLS 3D Printer
What is SLS 3D printing?
Learn about the basic principles of selective laser sintering, also known as SLS 3D printing. Discover how SLS 3D printing works, the advantages of SLS techniques for rapid prototyping and low-production runs, and the various materials and options available that will suit your part or project.
Selective Laser Sintering (SLS) is an additive manufacturing process that belongs to the Powder Bed Fusion family. In SLS 3D printing, a laser selectively sinters the particles of a polymer powder, fusing them together and building a part, layer by layer. The materials used in SLS are thermoplastic polymers that come in a granular form.
A SLS 3D printing service is used for both prototyping of functional polymer components and for small production runs. Its versatility makes SLS a great alternative to injection molding for low-production runs.
How does SLS 3D printing work?
SLS 3D printing uses a laser to sinter small particles of polymer powder. The entire cross-section of the component is scanned, so the part is built solid. The process works as follows:
-
The powder bin and the build area are first heated to just below the melting temperature of the polymer.
-
A re-coating blade spreads a thin layer of powder over the build platform.
-
A CO2 laser then scans the contour of the next layer and selectively sinters—fuses together—the particles of the polymer powder.
-
When a layer is complete, the build platform moves downwards and the blade re-coats the surface.
The process then repeats until the whole part is complete. -
After printing, the parts are fully encapsulated in the unsintered powder. The powder bin must cool before the parts can be unpacked, which can take a considerable amount of time—sometimes up to 12 hours.
-
The parts are then cleaned with compressed air or another blasting media, then they are ready to use or further post-process.
Watch the SLS process in action in this 30-second video.
Can you use SLS 3D printing for rapid prototyping?
SLS is a great solution for the rapid prototyping of functional polymers because it offers a very high degree of design freedom and high accuracy. And unlike FDM or SLA 3D printing techniques, it produces parts with good and consistent mechanical properties.
This means it can be used to produce parts that are very close to end-use quality, so you can use it throughout the production process, from concept to trial models.
Can you use SLS 3D printing for low-production runs?
Its versatility makes SLS 3D printing an ideal alternative to injection molding for low-production runs. SLS can be used to manufacture parts with complex shapes and geometries, and with a wide variety of finishes and lead times.
How does an SLS 3D printer work?
Schematic of a SLS printerFor use of an SLS 3D printer, almost all process parameters are preset by the machine manufacturer. The default layer height used is 100–120 microns.
A key advantage of SLS 3D printing is that it needs no support structures. The unsintered powder provides the part with all the necessary support. For this reason, SLS can be used to create free-form geometries that are impossible to manufacture with any other method.
Taking advantage of the whole build volume is very important when printing with SLS, especially for small batch productions . A bin of a given height will take about the same time to print, independent of the number of parts it contains. This is because laser scanning occurs very rapidly, so it’s actually the re-coating step which determines the total processing time. The machine will have to cycle through the same number of layers regardless of the number of parts. Bin packing may affect lead times of small orders, as operators may wait until a bin is filled before starting a print task.
Layer Adhesion
The bond strength between layers in SLS 3D printing is excellent. This means that SLS printed parts have almost isotropic mechanical properties.
The mechanical properties of SLS specimens printed using standard polyamide powder ( PA 12 or Nylon 12)—the most commonly used material in SLS—are shown in the next table and compared to the properties of bulk nylon.
| X-Y direction | Z direction | Bulk PA12 | |
|---|---|---|---|
| Tensile Strength | 48 MPa | 42 MPa | 35–55 MPa |
| Tensile Modulus | 1650 MPa | 1650 MPa | 1270–2600 MPa |
| Elongation at break | 18% | 4% | 120–300% |
SLS parts have excellent tensile strength and modulus, comparable to the bulk material, but are more brittle—their elongation at break is much lower. This is due to the internal porosity of the final part.
Shrinkage & Warping
SLS parts are susceptible to shrinkage and warping. As the newly sintered layer cools, its dimensions decrease and internal stresses buildup, pulling the underlying layer upwards.
Three to 3.5% shrinkage is typical in SLS, but machine operators take this into account during the build preparation phase and adjust the size of the design accordingly.
Large flat surfaces are the most likely to warp. The issue can be mitigated somewhat by orientating the part vertically in the build platform, but the best practice is to reduce its volume by minimizing the thickness of the flat areas and by introducing cutouts to the design. This strategy will also reduce the overall cost of the part, as less material is used.
Oversintering
Oversintering occurs when radiant heat fuses unsintered powder around a feature. This can result in loss of detail in small features, such as slots and holes. As a rule of thumb, slots wider than 0.8mm and holes with diameter larger than 2mm can be printed in SLS without fear of oversintering. Read our article on how to design parts for SLS 3D printing for more DFM tips.
Powder Removal
Since SLS requires no support material, parts with hollow sections can be printed easily and accurately.
Hollow sections reduce the weight and cost of a part, as less material is used.
Escape holes are needed to remove the unsintered powder from the inner sections of the component. We recommend adding at least two escape holes to your design, with a minimum diameter of 5mm.
If a high degree of stiffness is required, parts must be printed fully solid. An alternative is to make a hollow design omitting the escape holes. In this way, tightly packed powder will be entrapped in the part, increasing its mass and providing some additional support against mechanical loads, without an effect on the build time. An internal honeycomb lattice structure can be added to the hollowed interior (similar to the infill patterns used in FDM ) to further increase the stiffness of the component. Hollowing a part this way may also reduce warping.
What are the characteristics of SLS 3D printing?
The main characteristics of SLA are summarized in the table below:
| Selective Laser Sintering (SLS) | |
|---|---|
| Materials | Thermoplastics (usually nylon) |
| Dimensional accuracy | ± 0. 3% (lower limit of ± 0.3 mm) |
| Typical build size | 300 x 300 x 300mm (up to 750 x 550 x 550mm) |
| Common layer thickness | 100–120 µm |
| Support | Not required |
What materials are used for SLS printing?
The most widely used SLS material is Polyamide 12 (PA 12), also known as Nylon 12. The price per kilogram of PA 12 powder is approximately $50–$60. Other engineering plastics such as PA 11 and PEEKare also available, but these are not as widely used.
Polyamide powder can be filled with various additives to improve the mechanical and thermal behavior of the produced SLS part. Examples of additives include carbon fibers, glass fibers or aluminium. Materials filled with additives are usually more brittle and can have highly anisotropic behavior.
| Material | Characteristics |
|---|---|
| Polyamide 12 (PA 12) | + Good mechanical properties + Good chemical resistance - Matte, rough surface |
| Polyamide 11 (PA 11) | + Fully isotropic behavior + High elasticity |
| Aluminium-filled nylon (Alumide) | + Metallic appearance + High stiffness |
| Glass-filled nylon (PA-GF) | + High stiffness + High wear & temperature resistance - Anisotropic behavior |
| Carbon-fiber filled nylon (PA-FR) | + Excellent stiffness + High weight-strength ratio - Highly anisotropic |
What are the options for SLS post-processing?
SLS 3D printing produces parts with a powdery, grainy surface finish that can be easily stained.
The appearance of SLS printed parts can be improved to a very high standard using various post-processing methods, such as media polishing, dyeing, spray painting and lacquering. Their functionality can also be enhanced by applying a watertight coating or a metal plating. For more details, check out this extensive article on post-processing for SLS parts.
What are the advantages of SLS 3D printing
-
SLS parts have good, isotropic mechanical properties, making them ideal for functional parts and prototypes.
-
SLS requires no support, so designs with complex geometries can be easily produced.
-
The manufacturing capabilities of SLS is excellent for small to medium batch production.
-
All remaining unsintered powder is collected and can be reused.
What are the disadvantages of SLA 3D printing?
-
Only industrial SLS systems are currently widely available, so lead times are longer than other 3D printing technologies , such as FDM and SLA.
-
SLS parts have a grainy surface finish and internal porosity that may require post processing, if a smooth surface or watertightness are required.
-
Large flat surfaces and small holes cannot be printed accurately with SLS, as they are susceptible to warping and oversintering.
SLS best practices
Is SLS 3D printing right for your part or project? These are the rules of thumb:
-
SLS can produce functional parts from a large range of engineering plastics—most commonly Nylon (PA12).
-
The typical build volume of an SLS system is 300 x 300 x 300mm.
-
SLS parts exhibit good mechanical properties and isotropic behavior. For components with special requirements, additive-filled PA powders are available.
Ready to transform your CAD file into a custom part? Upload your designs for a free, instant quote.
Get an instant quoteSelective Laser Sintering (SLS) 3D Printing Guide
Selective Laser Sintering (SLS) 3D printing is a technology trusted by engineers and manufacturers across industries to create durable and functional models.
In this detailed guide, we'll explain selective laser sintering technology, the different systems and materials on the market, the workflow and different applications of SLS printers, and when to choose 3D printing with this technology over others. additive and traditional manufacturing methods.
White paper
Looking for a 3D printer to create durable, functional models? Download our white paper to learn how selective laser sintering (SLS) technology works and why it is popular in 3D printing for functional prototypes and end-use products.
Download white paper
Selective laser sintering (SLS) is an additive manufacturing technology that uses a powerful laser to sinter fine polymer powder particles into a solid structure based on a 3D model.
SLS 3D printing has been popular with engineers and manufacturers for decades. With its low model cost, high productivity, and common materials, this technology is well suited for a wide range of applications, from rapid prototyping to low-volume production, limited trial runs, or custom-made products.
Recent advances in technology, materials and software have opened up the possibility of SLS printing to a wider range of companies. Previously, such tools were used only in a few high-tech industries.
Introducing the Fuse 1 high performance SLS 3D printer, finally available.
Webinar
Watch our product demo to learn about Fuse 1 and SLS 3D printing from Formlabs.
Watch webinar
Schematic representation of the selective laser sintering process. The SLS method uses a powerful laser to sinter small particles of polymer powder into a solid structure based on a 3D model.
-
Print: A thin layer of powder is applied to the top of the platform inside the working chamber. The printer preheats the powder to just below the melting point of the feedstock. This allows the laser to more easily raise the temperature of certain areas of the powder bed and monitor the solidification of the model. The laser scans the cross section of the 3D model, heating the powder to the material's melting temperature or just below. Particles are mechanically joined together to form a single solid object. The unsprayed powder supports the model during printing and eliminates the need for special support structures. The platform is then lowered into the working chamber one layer, typically 50-200 µm thick, and the process is repeated for each layer until the models are complete.
-
Cooling down: after printing and before post-processing, the build chamber should cool down a little in the printer body and then outside the body to ensure optimal mechanical properties of the models and avoid their deformation.
-
Postprocessing: finished models must be removed from the working chamber, separated from each other and cleaned of excess powder. The powder can be recycled and printed models can be blasted or tumbled.
To learn more about the workflow, see the SLS 3D Printing Workflow section below.
SLS models have a slightly grainy surface, but the layer lines are almost invisible. To achieve a smooth surface, SLS models are recommended to be blasted or tumbled. This sample was printed on a Fuse 1 industrial 3D printer with SLS technology for workshops from Formlabs.
The green powder supports the model during printing and eliminates the need for special support structures. This makes SLS ideal for complex geometries, including internal features, undercuts, thin walls, and negative draft features.
Models created using SLS 3D printing have excellent mechanical properties: their strength is comparable to that of injection molded models.
Compare Selective Laser Sintering (SLS) 3D printing with other common plastic modeling technologies: Fused Deposition Modeling (FDM) and Stereolithography (SLA).
Selective Laser Sintering (SLS) is one of the first additive manufacturing technologies developed in the mid-1980s by Dr. Carl Deckard and Dr. Joe Beeman at the University of Texas at Austin. Since then, the method has been adapted to work with a variety of materials, including plastics, metals, glass, ceramics, and various powdered composite materials. Today, all of these technologies are classified as wafer synthesis, additive manufacturing processes that selectively sinter regions of a powder layer under the influence of thermal energy.
The two most common substrate synthesis systems currently available are a plastic based method commonly referred to as Selective Laser Sintering (SLS) and a metal based method known as Direct Metal Laser Sintering (DMLS) or Selective Laser Melting (SLM). ). Until recently, both systems were very expensive and complex, which limited their use to the production of small batches of expensive models or custom-made products, such as aerospace components or medical devices.
Innovation in this area will make plastic-based SLS as affordable as other 3D printing technologies such as stereolithography (SLA) and Fused Deposition Modeling (FDM) and become widely available in affordable, compact systems.
All selective laser sintering 3D printers use the process described in the previous section. Basically, such printers differ in the type of laser, the volume of printing and the complexity of the system. Different solutions are used for temperature control, powder dosing and layering in different devices.
Selective laser sintering technology requires high precision and strict control during the printing process. The temperature of the powder and (incomplete) models must be controlled within 2°C during the three stages of production: preheating, sintering and storage before extraction, in order to minimize warping, stress and thermal deformation.
For decades, selective laser sintering has been one of the most popular professional 3D printing technologies, but due to its complexity, strict requirements and high price, only service bureaus and large enterprises could use it.
Conventional industrial SLS 3D printing systems have one or more powerful lasers. An inert atmosphere (nitrogen or other gases) is needed to prevent the powder from oxidizing and breaking down during the printing process, which requires specialized air handling equipment.
These installations also require special heating, ventilation and air conditioning (HVAC) systems and industrial power supplies. In addition, even the smallest industrial installations occupy an area of at least 10 square meters. m.
Due to the high initial cost of approximately $100,000 (and much more for complete solutions), traditional industrial systems with SLS technology were out of reach for many enterprises.
As with other 3D printing technologies such as Fused Deposition Modeling (FDM) and Stereolithography (SLA), more affordable, compact systems with SLS technology have recently begun to appear on the market. However, these solutions had significant drawbacks. These include low quality models and complex manual workflows due to a lack of post-processing solutions.
This severely limited their use in industrial production.
The Formlabs Fuse 1 printer is in a new category with these deficiencies fixed . It is the first industrial SLS 3D printer for the workshop, delivering high quality, compact size, streamlined workflow, and cost far less than traditional industrial systems of the same type.
The Fuse 1 printer does not require any special infrastructure and will easily fit into your workplace.
The Fuse 1 uses a single laser and has a smaller working chamber that requires less heat. The powder is exposed to elevated temperatures for a shorter period of time, so there is no need for inert gases and specialized ventilation equipment. Thanks to its lower power consumption, it can run on a standard AC power supply without requiring special infrastructure.
The Fuse 1 features patent pending Surface Armor technology. This creates a semi-baked shell that heats evenly around the models as they are printed. This results in excellent surface quality, stable mechanical properties, high reliability and a high material renewal rate.
In addition to providing a compact, self-sustaining ecosystem and complete powder handling capability, Fuse 1 is complemented by the Fuse Sift Station, a stand-alone stand-alone device for model retrieval, recovery, storage and powder mixing.
Overall, the Fuse 1 industrial 3D printer with SLS for workshops has slightly less print volume than traditional entry-level SLS systems, but is smaller, easier to work with and less expensive.
| Fuse 1 Industrial SLS Workshop Printer | Conventional SLS Industrial 3D Printers | 5 Cost | from 18,500 US dollars | 100 000 - 500,000 US dollars and more than | ||||
|---|---|---|---|---|---|---|---|---|
| Press volume | to 165 x 165 x 300 mm | 9010 x 550 x 750 mm 7509 Benefits | Availability High quality models High performance Simplified workflow Compact dimensions Low maintenance | High print volume High quality models High performance Many material options | ||||
| Disadvantages | Less print volume Limited material options | Expensive equipment Big sizes Infrastructure requirements Large amount of maintenance Special Operator Required |
The most common selective laser sintering (SLS) material is nylon.
It is a high performance engineering thermoplastic for both functional prototyping and end-use fabrication. Nylon is ideal for the production of complex knots and strong models with high environmental resistance.
3D printed SLS nylon for strength, rigidity and durability. The final models are impact-resistant and highly wear-resistant. Nylon is resistant to UV, light, heat, moisture, solvents, temperature and water. Nylon models printed on a 3D printer are also biocompatible and do not cause allergic reactions. This means that they can be worn and used safely in many situations.
Nylon is ideal for a range of functional applications, from consumer product design to healthcare applications.
Nylon is a synthetic thermoplastic polymer from the polyamide family. It is available in several versions, each designed to print different products. Nylon 12 Powder has a wide range of applications and is a general purpose, general purpose SLS 3D printing powder. Nylon 12 GF Powder is a composite material with a high fiber content, increased stiffness and heat resistance for difficult industrial conditions.
Nylon 11 Powder helps fill a gap in prototyping and end-use applications where increased ductility, impact resistance and the ability to withstand wear without brittle fracture are required.
- Impact proof prototypes, fixtures and fittings
- Thin-walled pipes and bodies
- Rivets, fasteners and latches
- Orthopedic products and prostheses*
- High Performance Prototyping
- Small batch production
- One-piece clamping and holding fixtures and tooling
- Conventional SLS models
- Heavy duty clamping and fastening fixtures and spare parts
- Continuous models
- Thread and sockets
- High temperature models
* Material properties may vary depending on model design and manufacturing method. It is the manufacturer's responsibility to confirm the suitability of printed models for their intended use.
109 40%
8 MPa (°C) Nylon 12 Powder and Nylon 11 Powder are one-component powders, but some SLS 3D printers can also use two-component powders, such as coated powders or powder blends.
Nylon 12 GF Powder is a composite material with a high fiberglass content, while other nylon composites with aluminide, carbon or glass are designed to increase the strength, stiffness or flexibility of models. In such two-component powders, only the component with the lower glass transition point is sintered, which binds both components.
SLS 3D printing accelerates innovation and helps businesses in a wide range of industries such as engineering, manufacturing and healthcare.
Manage the entire product development process, from iteration of first concept design to production of ready-to-use products:
- Rapid Prototyping
- Product mockups for user feedback
- Functional Prototyping
- Functional testing of products under severe conditions (e.
g. piping, brackets)
Manage your supply chain and respond quickly to changing needs:
- End-Use Manufacturing
- Small batch production
- Mass production of new customized consumer products
- Spare parts manufacturing, supply chain sustainability
- Durable, durable clamping and fastening devices (e.g. clamps and clamps) and accessories
- Custom manufacture of automotive, motorcycle and marine equipment parts, and restock military items on demand
Self-manufacturing of ready-to-use medical devices, taking into account the individual characteristics of patients:
- Medical device prototyping
- Prostheses and orthotics (e.g. prosthetic limbs and orthoses)
- Surgical models and instruments
- End use products (nylon 12 biocompatible and sterilizable*)
* Material properties may vary depending on model design and production method. It is the manufacturer's responsibility to confirm the suitability of printed models for their intended use.
Use any CAD software or 3D scan data to design the model and export it to a 3D printable format (STL or OBJ) file. All printers with SLS technology use software that allows you to adjust settings, position models, estimate print times, and layer your digital model. Once set up, the model preparation software sends commands to the printer via a wireless or cable connection.
The Fuse 1 uses PreForm print preparation software (free to download). It allows you to easily duplicate and place multiple models on a 3D grid to maximize your print volume. PreForm automatically suggests the optimal orientation and position of models with the ability to make manual changes.
The workflow for preparing the printer varies from system to system. Most traditional SLS systems require extensive training, tools, and physical actions to prepare and maintain them.
Fuse 1 redefines the SLS workflow, making it simple and efficient, as well as providing trouble-free printing and complete powder handling thanks to modular components.
The Fuse 1 can be easily loaded with powder using a special cartridge.
The Fuse 1 uses a detachable build chamber so you can start a new print while the previous build chamber is still cooling.
Once all pre-checks have been completed, the machine is ready to print. Depending on the size and complexity of the 3D models, as well as their density, printing using SLS technology can take from several hours to several days.
When printing is complete, the build chamber in the housing should cool down a bit before proceeding with the next step. To start the next print, you can remove the build chamber and insert a new one. Before post-processing, the working chamber must cool down to ensure optimal mechanical properties of the models and avoid their deformation. This can take up to half of the total print time.
Fuse 1 is equipped with a touch screen that allows you to see in real time how each new layer is formed during the printing process. This camera image can also be transferred to a computer using PreForm to monitor the print without leaving the workplace.
Compared to other 3D printing processes, post-processing of SLS-printed models requires a minimum of time and labor. With no supporting structures, it is easy to scale and provides consistent results across batches of models.
After printing is completed, remove the finished models from the build chamber, separate them and clean them of excess powder. As a rule, this is done manually at the cleaning station using compressed air or a jet apparatus.
The excess powder left after the creation of the model is filtered to remove large particles from it. After that, it can be recycled. Under the influence of high temperature, the properties of green powder deteriorate slightly, so for subsequent printing it must be mixed with new material. Due to the possibility of reusing materials, SLS technology produces a minimum amount of waste.
SLS technology typically uses separate devices for powder recovery, storage and mixing. The Fuse 1 workflow uses a single Fuse Sift to retrieve patterns and greens, store, dispense, and mix material streams.
Fuse Sift completes the Fuse 1 SLS print workflow. This system is used for safe and efficient model retrieval and powder recycling.
Fuse Sift automatically doses and mixes used and new powder, reducing waste and controlling powder delivery.
After the powder has been sieved, the 3D models printed using selective laser sintering technology are ready for use. However, there are a few more post-processing steps you can perform on these models.
By default, the surface of 3D models created using SLS technology remains grainy. To achieve a smooth surface, Formlabs recommends blasting or tumbling models made using this method. Models can be spray painted, lacquered, electroplated or otherwise to achieve the desired color, surface quality and properties such as water resistance (special coating) and electrical conductivity (electrolytic coating). Models created with SLS Formlabs are dark in color and therefore not well suited for staining.
Immersion printed SLS model from Partial Hand Solutions.
SLS models can be electroplated for a metal-like surface.
Selective laser sintering is preferred by engineers and manufacturers for its wide design options, high productivity, low model cost and proven end use materials.
Most additive manufacturing processes such as stereolithography (SLA) and Fused Deposition Modeling (FDM) require specialized support structures to fabricate overhang structures.
Selective laser sintering does not require support structures because the unsintered powder surrounds the model during printing. SLS printing makes it easy to create overhangs, intricate geometries, interconnecting parts, internal channels and other intricate details.
Intricately patterned arm splint for weight reduction.
Engineers typically design models in terms of the capabilities of the final manufacturing process, also known as design-for-technology (DFM). When additive manufacturing is only used for prototyping, it comes down to creating models and designs that can be replicated in the manufacturing process using traditional tools.
Selective laser sintering is emerging as a viable rapid production method and its application area continues to expand, so it can open up new possibilities in design and construction. 3D printers with SLS technology can create complex geometries that are impossible or incredibly expensive to manufacture using traditional processes. SLS technology also allows design professionals to combine complex assemblies into a single model that would normally require multiple models to be created. This helps avoid the problem of loose connections and saves assembly time.
Selective laser sintering can unleash the potential of generative design, as it allows the creation of lightweight models that use complex lattice structures that cannot be fabricated by traditional methods.
Selective laser sintering is the fastest additive manufacturing technology for making functional, durable prototypes and end-use products. Lasers used for powder sintering have much faster scanning speeds and are more accurate than the layering methods used in other processes such as Industrial Fused Deposition Modeling (FDM).
To maximize the available print volume in each printer, multiple models can be placed side by side. Operators can use the software to optimize print volume and maximize productivity by leaving only minimal clearance between models.
SLS technology allows operators to fill the build chamber with as many models as possible, as it allows them to be printed without supporting structures, saving time in post-processing.
SLS 3D printing requires the right materials for functionality and versatility. Nylon and its composites are proven, high quality thermoplastic materials. Laser-sintered nylon models have close to 100% density and mechanical properties that are comparable to products made using traditional manufacturing methods such as injection molding.
Screwdriver printed in Nylon 12 Powder. After a simple post-processing, nylon models have a smooth, professional quality surface.
SLS Printable Nylon is an excellent replacement for conventional injection molded plastics.
The latches and other mechanical connections produced from it are superior to products created using any other additive manufacturing technology. It is ideal for making functional plastic parts that will work and not break down over time like products created through other additive manufacturing methods.
When calculating the cost of one model, it is usually necessary to take into account the cost of ownership of equipment, material costs and labor costs:
-
Equipment cost of ownership: The more models a printer can produce over its lifetime, the lower the cost per model. Therefore, higher performance results in a lower cost of ownership per model. With high laser scanning speeds, the ability to produce multiple models at once to maximize the working volume, and a simple post-processing process, SLS 3D printing guarantees the highest productivity of any additive manufacturing method.
-
Material: Most 3D printing technologies use proprietary materials, while nylon is a common thermoplastic that is produced in large quantities for industrial applications.
This makes it one of the most inexpensive raw materials for additive manufacturing. SLS 3D printing requires no support structures and allows you to print with recycled powder with minimal waste. -
Labor: Labor is a disadvantage of many 3D printing solutions. Work processes in most technologies are quite laborious and difficult to automate, which can significantly affect the cost of one model. Easy post-processing with SLS printing reduces manual labor and allows for easy scalability.
A 3D printer with SLS technology is a significant investment initially, but this investment often pays off even faster than buying smaller devices. SLS for workshop technology significantly reduces initial acquisition costs and also reduces model costs in most applications.
If 3D printing is rarely used in your business, it is recommended to use the services of third-party service bureaus. But in this case, the cash costs will be higher and you will have to wait longer for the order to be completed.
One of the main advantages of 3D printing is its speed compared to traditional production methods. But this advantage loses its value when it takes up to several weeks for a third-party company to deliver a model.
REEKON Tools
In many cases, for the production of limited or small trial runs, selective laser sintering is a cost-effective alternative to injection molding. 
Selective laser sintering. 
Cooling down can take a significant amount of time, up to 12 hours. Then the resulting part is cleaned of powder residues with compressed air. The unsintered powder is collected for further reuse. 
Regardless of the amount of detail in the printable area, if the overall height is the same, printing will take the same amount of time. This is because it is the recoating step that determines the total print time ( the laser scanning and sintering itself is very fast ), and the printer has to cycle through the same number of layers. Also, you need to take into account the time for refilling the hopper with powder, because the same amount is poured into the chamber, regardless of the size of the printed part. 
This is due to the internal porosity of the resulting part. 
But still, the best way to reduce deformation is to minimize the thickness of the flat areas of the part, and add cutouts to the model where the design allows. These actions will also reduce the overall cost of the part, as less material will be used. 
Laying out the part in this way will also help reduce warping. 
