3D printing with laser

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.

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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.

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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.

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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.

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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.}

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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.

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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

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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

3D printing: Laser-based technique produces complex objects in any order

Existing 3D printers work by building up an object one layer at a time, making it difficult to produce some intricate shapes, but a new technique involving lasers could change that

Technology 20 April 2022

By Matthew Sparkes

A model of a boat printed using the new technique

Dan Congreve

A 3D printer that uses lasers to build up an object in any order, rather than layer by layer, could produce more advanced designs than is currently possible.

Existing 3D printers work by depositing layers of a plastic filament from a nozzle or by curing layers of resin with UV light. In both cases objects are built up one layer at a time, meaning that overhanging parts of a structure – the outstretched arms of a model human, say – must be propped up by temporary supports until printing is complete. These supports must then be carefully removed manually.

To get around this, Dan Congreve at Stanford University in California and his colleagues created a 3D-printing system that involves focusing a red laser at a particular point in a pool of resin. The resin is impregnated with particles 80 nanometres wide that convert red light into blue once the light hits a certain energy threshold, which only occurs at the point where the red laser is precisely focused.

When this happens, the surrounding resin reacts to the blue light, hardening. This means that individual points within the material can be fixed without curing the resin along the entire beam of light.

Over the past four decades, laser cutting machines have become a must-have tool for the vast majority of sheet metal fabricators.

From CO2 lasers to their newer and more capable solid-state counterparts, what began as a laboratory experiment in the 1960s is today the method of choice for quickly and accurately cutting virtually any metal less than 2.54 cm thick.

However, soon after lasers began to appear in workshops everywhere, another use was found for collimated light, which seems destined to play an equally important role in production.

In 1987, 3D Systems co-founder Chuck Hull sold the first SLA-1 machine using an ultraviolet laser to cure thin layers of photoreactive resin. Additive manufacturing (AM), better known as 3D printing, was born.

Since then, 3D printing has evolved from a photopolymer-only prototyping process to a viable method for producing final parts. With a variety of materials available, including engineering plastics, superalloys such as titanium and INCONEL, maraging steels, tool steels, and stainless steels, there is nothing that 3D printers cannot produce. And while laser light is not the only technology used to solidify, sinter, melt, or otherwise combine these various materials, it is definitely the leader in additive manufacturing. nine0006

Note: This article is a translation.

Long live the difference?

How is a laser capable of cutting through 18 mm thick steel different from a laser used to print tooling for press brakes, assembly fixtures and robotic end effectors?

"Metal 3D printing in industry mainly uses fiber lasers with a wavelength of 1070 nanometers, i.e. in the infrared range, while for cutting, a continuous solid-state fiber or disk laser with a wavelength in the range from 1030 to 1080 nm is usually used" , explains Dave Locke, Additive Manufacturing Sales Specialist at TRUMPF Inc. nine0006

Obviously the wavelengths are similar, but this is not the case for power. The power of lasers installed in TRUMPF printers for metal processing by powder coating (PBF) does not exceed 500 W. Lasers used for cutting, on the contrary, produce up to 6 kilowatts - 12 times more. If you put that much laser power into a 3D printer, it will burn a hole in the bottom of the machine.

However, it is important to understand that laser power is only one operating parameter of many, whether the metal is being fused or cut into pieces. In addition to power, manufacturers are also looking to provide versatility. For example, they go to great lengths to make their products "customizable" (adjustable to work with different materials) depending on the grade and thickness of the material being cut. nine0006

Fiber lasers are now able to effectively cut thicker materials that were previously reserved for CO2 lasers.

"bell-shaped Gaussian waveform, similar to that generated by fiber lasers provide very high spot densities, which is what gives them the ability to cut through thin materials,” explains Dustin Deal, product manager for Amada America's laser division. “However, this small spot size becomes less effective when you move up to 1.3 mm cm and above, and this is the reason why CO2 lasers have long offered better speeds and better edge quality on thicker materials."

"But as technology evolved, Amada (and other companies) found ways to adjust the laser beam diameter and waveform to create a larger spot - shaped like a hat. That's why, and for other reasons, Amada switched completely to fiber in its standard line of laser cutting machines,” says Deal.

Does this mean that CO2 lasers are going down in history? Hardly. "Polymers are basically transparent to shorter fiber laser wavelengths, so using them in 3D printing is like shining a flashlight through the snow," says Damien Gray, Principal Laser Optics Engineer at EOS North America Inc, Pflugerville, Texas. It goes right through. "The light from a CO2 laser, on the other hand, is strongly absorbed by most polymers." nine0006

This is good news for selective laser sintering (SLS), the plastic alter ego of PBF metal printing. But there is a caveat: CO2 lasers provide lower print resolution and cannot do the fine details that fiber lasers can.

David Cullen, Director of Application Engineering, 3D Systems Inc. in Rock Hill, South Carolina, explained that the CO2 laser used in his company's SLS printers has a wavelength of about 10,600 nm, which is 10 times longer than a conventional fiber laser. As the wavelength increases, so does the spot size. nine0006

"You get a print resolution of 475 microns, or about half a millimeter, which is much better than a powder coated machine," he says. "On a positive note, the SLS print speed is one of the fastest in the industry."

Two spots beat one

Like laser cutting equipment manufacturers, 3D printer manufacturers use advanced optics and electronics to change laser parameters on the fly - at least in some cases. nine0006

The detail layer is printed on an SLA 3D printer from 3D Systems, the inventor of the stereolithography system.

The SLS setup just reviewed has a fixed beam size, but Cullen said stereolithography (SLA), the technology his company was founded on, now offers two spot sizes.

"By adjusting the crystal orientation in the YAG laser, we can generate a large spot to quickly scan large areas on the inside of a part, and then dynamically switch to a small spot for fine detail and contour tracking," he said. "The result is better part quality and faster assembly." nine0006

Ankit Saharan, application development and R&D manager at EOS, agreed on the importance of spot size control, but added that in the case of additive laser manufacturing, there are many more characteristics than spot size and the wavelength or type of laser used for it. creation.

"A small spot size is better than a large one because the smaller the spot size, the smaller the melt pool, which means less stress in the workpiece," Saharan said. "We start at around 45 µm on small platforms and go up to 100 µm on large platforms. " nine0006

However, smaller spot sizes also mean slower settling rates, so a balance must be struck between process stability and cost. In addition, there are many other factors such as layer thickness, powder grain size, powder delivery and application mechanisms, feed material reflectance, and various equipment parameters.

Saharan says, "This is a very complex scenario, and a high-quality laser, although important, is only part of what is needed to create a stable additive process." nine0006

We advise you to read articles published in our blog earlier: “‎Need non-standard plate bending equipment? Print it on a 3D printer! [Part 1]"‎ and "‎3D Printed Press Brake Stamping Tools"‎.

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Selective 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. nine0006

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.

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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. nine0006

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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. nine0006

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.

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Watch our product demo to learn about Fuse 1 and SLS 3D printing from Formlabs. nine0006

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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.

Seal: 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. nine0006
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. nine0006

To learn more about the workflow, see the SLS 3D Printing Workflow section below.

Models created using SLS technology 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. nine0006

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. nine0006

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. nine0006

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. nine0006

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 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. nine0006

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. nine0006

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. nine0006

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. nine0006

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 provide a compact, self-sustaining ecosystem and complete powder processing capability, Fuse 1 is complemented by the Fuse Sift Station, a separate stand-alone device for model retrieval, recovery, storage and powder mixing. nine0006

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.

Cost 90AL Benefits

	Fuse 1 Industrial SLS Workshop Printer	Conventional SLS Industrial 3D Printers
from 18,500 US dollars	100 000 - 500,000 US dollars and more than
Press volume	to 165 x 165 x 300 mm		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. nine0006

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. nine0006

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. nine0006

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
Threads 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.}

9 J/m

40%
Extension when rupture, Z (%)	6%	3%
DISCOUSE	32 J/m	32 J/m	32 J/m	32 J/m	71 J/m
Bending temperature under load at 1. 8 MPa (°C)	87 °C	113 °C	46 °C
	170°C	171°C	182 °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. nine0006

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 (such as 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:

Prototyping of medical devices
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. nine0006

The Fuse 1 uses PreForm print preparation software (free 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. nine0006

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. nine0006

When printing is completed, 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. nine0006

Compared to other 3D printing processes, post-processing of SLS-printed models requires minimal time and effort. With no supporting structures, it is easy to scale and provides consistent results across batches of models.

After printing is complete, 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. nine0006

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. nine0006

Fuse Sift completes the Fuse 1 SLS printing 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. nine0006

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. nine0006

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 fabricators for its wide design options, high productivity, low model cost, and proven end-use materials. nine0006

Most additive manufacturing processes such as stereolithography (SLA) and 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. nine0006

Intricately patterned arm splint for weight reduction.

Engineers typically design models to meet the capabilities of the final manufacturing process, also known as design-to-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 manufacturing 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. nine0006

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). nine0006

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. nine0006

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. nine0006

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. nine0006

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. nine0006
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. nine0006

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

Selective laser sintering allows engineers to prototype parts early in the development cycle and then use the same equipment and materials to produce end-use products. SLS 3D printing does not require the same costly and time-consuming tools as traditional manufacturing, so prototype parts and assemblies can be tested and easily modified in just a few days. As a result, product development time is significantly reduced. nine0006

SLS 3D printing is great for creating durable, functional prototypes. They withstand rigorous testing and can be supplied to customers as spare parts or ready-to-use products.

Given the low cost per model and the durability of materials, SLS printing is an economical way to produce complex custom designs or batches of small components for final products.

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