Stereolithographic 3d printers

Stereolithography (SLA) 3D Printing Guide

Stereolithography (SLA) 3D printing is the most common resin 3D printing process that has become vastly popular for its ability to produce high-accuracy, isotropic, and watertight prototypes and end-use parts in a range of advanced materials with fine features and smooth surface finish.

In this comprehensive guide, learn how SLA 3D printers work, why thousands of professionals use this process today, and how SLA printers can benefit your work.

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Stereolithography belongs to a family of additive manufacturing technologies known as vat photopolymerization, commonly known as resin 3D printing. These machines are all built around the same principle, using a light source—a laser or projector—to cure liquid resin into hardened plastic. The main physical differentiation lies in the arrangement of the core components, such as the light source, the build platform, and the resin tank.

Watch how stereolithography (SLA) 3D printing works.

SLA 3D printers use light-reactive thermoset materials called “resin.” When SLA resins are exposed to certain wavelengths of light, short molecular chains join together, polymerizing monomers and oligomers into solidified rigid or flexible geometries.

A graphic representation of the basic mechanics of stereolithography (SLA) 3D printing.

SLA parts have the highest resolution and accuracy, the sharpest details, and the smoothest surface finishes of all 3D printing technologies, but the main benefit of the stereolithography lies in its versatility.

Material manufacturers have created innovative SLA resin formulations with a wide range of optical, mechanical, and thermal properties to match those of standard, engineering, and industrial thermoplastics.

Advancements in 3D printing continue to change the way businesses approach prototyping and production. As the technology becomes more accessible and affordable and hardware and materials advance to match market opportunities and demands, designers, engineers, and beyond are integrating 3D printing into workflows across development cycles. Across industries, 3D printing is helping professionals cut outsourcing costs, iterate faster, optimize production processes, and even unlock entirely new business models.

Stereolithography 3D printing in particular has undergone significant changes. Traditionally, SLA 3D printers have been monolithic and cost-prohibitive, requiring skilled technicians and costly service contracts. Today, small format desktop printers produce industrial-quality output, at substantially more affordable price points and with unmatched versatility.

Compare stereolithography 3D printing to two other common technologies for producing plastic parts: fused deposition modeling (FDM) and selective laser sintering (SLS).

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See how to go from design to 3D print with the Form 3+ SLA 3D printer. This 5-minute video covers the basics of how to use the Form 3, from the software and materials to printing and post-processing.

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 SLA printer includes software to specify printing settings 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.

More advanced users may consider specifically designing for SLA, or taking steps like hollowing parts to conserve material.

After a quick confirmation of the correct setup, the printing process begins and the machine can run unattended until the print is complete. In printers with a cartridge system, the material is automatically refilled by the machine.

An online Dashboard from Formlabs allows you to remotely manage printers, materials, and teams.

Once the printing is completed, parts require rinsing in isopropyl alcohol (IPA) to remove any uncured resin from their surface. After rinsed parts dry, some materials require post-curing, a process which helps parts to reach their highest possible strength and stability. Finally, remove supports from the parts and sand the remaining support marks for a clean finish. SLA parts can be easily machined, primed, painted, and assembled for specific applications or finishes.

Post-curing is particularly important for functional resins for engineering, and mandatory for some dentistry and jewelry materials and applications.

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Engineers, designers, manufacturers, and more choose SLA 3D printing for its fine features, smooth surface finish, ultimate part precision and accuracy, and mechanical attributes like isotropy, watertightness, and material versatility.

Because 3D printing creates parts one layer at a time, completed prints may have variations in strength based on orientation of the part relative to the printing process, with different properties in X, Y, and Z axes.

Extrusion-based 3D printing processes like fused deposition modeling (FDM) are known for being anisotropic due to layer-to-layer differences created by the print process. This anisotropy limits the usefulness of FDM for certain applications, or requires more adjustments on the part geometry side to compensate for it.

Read our in-depth guide about FDM vs. SLA 3D printers to learn how they compare in terms of print quality, materials, applications, workflow, speed, costs, and more.

In contrast, SLA resin 3D printers create highly isotropic parts. Achieving part isotropy is based on a number of factors that can be tightly controlled by integrating material chemistry with the print process. During printing, resin components form covalent bonds, but layer to layer, the part remains in a semi-reacted “green state.”

While in the green state, the resin retains polymerizable groups that can form bonds across layers, imparting isotropy and watertightness to the part upon final cure. On the molecular level, there is no difference between X, Y, or Z planes. This results in parts with predictable mechanical performance critical for applications like jigs and fixtures, end-use parts, and functional prototyping.

SLA printed parts are highly isotropic compared to those produced with fused deposition modeling (FDM).

Because they are isotropic, SLA printed parts like this jig from Pankl Racing Systems can withstand the variety of directional forces they undergo during high stress manufacturing operations.

SLA printed objects are continuous, whether producing geometries with solid features or internal channels. This watertightness is important for engineering and manufacturing applications where air or fluid flow must be controlled and predictable. Engineers and designers use the watertightness of SLA printers to solve air and fluid flow challenges for automotive uses, biomedical research, and to validate part designs for consumer products like kitchen appliances.

OXO relies on the watertightness of SLA printing to create robust functional prototypes for products with air or fluid flow, like this coffee maker.

Industries from dental to manufacturing depend on SLA 3D printing to repeatedly create accurate, precise components. For a print process to produce accurate and precise parts, multiple factors must be tightly controlled.

Compared to machined accuracy, SLA 3D printing is somewhere between standard machining and fine machining. SLA has the highest tolerance of commercially available 3D printing technologies. Learn more about understanding tolerance, accuracy, and precision in 3D printing.

The combination of the heated resin tank and the closed build environment provides almost identical conditions for each print. Better accuracy is also a function of lower printing temperature compared to thermoplastic-based technologies that melt the raw material. Because stereolithography uses light instead of heat, the printing process takes place at close to room temperature, and printed parts don't suffer from thermal expansion and contraction artifacts.

An example from the dental industry comparing a scanned component with the original CAD geometry, demonstrating the ability to maintain tight tolerances across an SLA printed part.

Low Force Stereolithography (LFS) 3D printing houses the optics inside a Light Processing Unit (LPU) that moves in the X direction. One galvanometer positions the laser beam in the Y direction, then directs it along across a fold mirror and parabolic mirror to deliver a beam that is always perpendicular to the build plane, so it is always moving in a straight line to provide even greater precision and accuracy, and allows for uniformity as hardware scales up to larger sizes, like Formlabs larger format SLA printer Form 3L. The LPU also uses a spatial filter to create a crisp, clean laser spot for greater precision.

The characteristics of individual materials are also important for ensuring a reliable, repeatable print process.

Formlabs Rigid Resin has a high green modulus, or modulus before post-curing, which means it’s possible to print very thin parts with precision and a lower chance of failure.

SLA printers are considered the gold standard for smooth surface finish, with appearances comparable to traditional manufacturing methods like machining, injection molding, and extrusion.

This surface quality is ideal for applications that require a flawless finish and also helps reduce post-processing time, since parts can easily be sanded, polished, and painted. For example, leading companies like Gillette use SLA 3D printing to create end-use consumer products, like 3D printed razor handles in their Razor Maker platform.

Leading companies like Gillette use SLA 3D printing to create end-use consumer products, like the 3D printed razor handles in their Razor Maker platform.

Z-axis layer height is commonly used to define the resolution of a 3D printer. This can be adjusted in between 25 and 300 microns on Formlabs SLA 3D printers, with a trade-off between speed and quality.

In comparison, FDM and SLS printers typically print Z-axis layers at 100 to 300 microns. However, a part printed at 100 microns on an FDM or SLS printer looks different from a part printed at 100 microns on an SLA printer. SLA prints have a smoother surface finish right out of the printer, because the outermost perimeter walls are straight, and the newly printed layer interacts with the previous layer, smoothing out the staircase effect. FDM prints tend to have clearly visible layers, whereas SLS has a grainy surface from the sintered powder.

The smallest possible detail is also much finer on SLA, given 85 micron laser spot size on the Form 3+, in comparison with 350 microns on industrial SLS printers, and 250–800 micron nozzles on FDM machines.

While FDM 3D printed parts tend to have visible layer lines and might show inaccuracies around complex features, parts printed on SLA machines have sharp edges, a smooth surface finish, and minimal visible layer lines.

SLA resins have the benefit of a wide range of formulation configurations: materials can be soft or hard, heavily filled with secondary materials like glass and ceramic, or imbued with mechanical properties like high heat deflection temperature or impact resistance. Material range from industry-specific, like dentures, to those that closely match final materials for prototyping, formulated to withstand extensive testing and perform under stress.

Rigid 10K Resin is a highly glass-filled material for industrial parts that need to withstand significant load without bending, including applications like injection molding.

In some cases, its this combination of versatility and functionality that leads to companies to initially bring resin 3D printing in-house. After finding one application solved by a specific functional material, it’s usually not long before more possibilities are uncovered, and the printer becomes a tool for leveraging the diverse capabilities of various materials.

For example, hundreds of engineers in the Design and Prototyping Group at the University of Sheffield Advanced Manufacturing Research Centre (AMRC) rely on open access to a fleet of 12 SLA 3D printers and a variety of engineering materials to support highly diverse research projects with industrial partners like Boeing, Rolls-Royce, BAE Systems, and Airbus. The team used High Temp Resin to 3D print washers, brackets, and a sensor mounting system that needed to withstand the elevated, and leveraged Durable Resin to create intricate custom springy components for a pick and place robot that automates composites manufacturing.

Engineers at the AMRC use a fleet of 12 SLA 3D printers and a variety of engineering materials to print custom parts for diverse research projects, like brackets for a pick and place robot (top), and mounts for sensors in a high-temperature environment (bottom).

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SLA 3D printing accelerates innovation and supports businesses across a wide range of industries, including engineering, manufacturing, dentistry, healthcare, education, entertainment, jewelry, audiology, and more.

Rapid prototyping with 3D printing empowers engineers and product designers to turn ideas into realistic proofs of concept, advance these concepts to high-fidelity prototypes that look and work like final products, and guide products through a series of validation stages toward mass production.

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Manufacturers automate production processes and streamline workflows by prototyping tooling and directly 3D printing custom tools, molds, and manufacturing aids at far lower costs and lead times than with traditional manufacturing. This reduces manufacturing costs and defects, increases quality, speeds up assembly, and maximizes labor effectiveness.

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Digital dentistry reduces the risks and uncertainties introduced by human factors, providing higher consistency, accuracy, and precision at every stage of the workflow to improve patient care. 3D printers can produce a range of high-quality custom products and appliances at low unit costs with superior fit and repeatable results.

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Affordable, professional-grade desktop 3D printing helps doctors deliver treatments and devices customized to better serve each unique individual, opening the door to high-impact medical applications while saving organizations significant time and costs from the lab to the operating room.

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3D printers are multifunctional tools for immersive learning and advanced research. They can encourage creativity and expose students to professional-level technology while supporting STEAM curricula across science, engineering, art, and design.

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High definition physical models are widely used in sculpting, character modeling, and prop making. 3D printed parts have starred in stop-motion films, video games, bespoke costumes, and even special effects for blockbuster movies.

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Jewelry professionals use CAD and 3D printing to rapidly prototype designs, fit clients, and produce large batches of ready-to-cast pieces. Digital tools allow for the creation of consistent, sharply detailed pieces without the tediousness and variability of wax carving.

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Hearing specialists and ear mold labs use digital workflows and 3D printing to manufacture higher quality custom ear products more consistently, and at higher volumes for applications like behind-the-ear hearing aids, hearing protection, and custom earplugs and earbuds.

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Many companies start using 3D printing via outsourcing to service bureaus or labs. Outsourcing production can be a great solution when teams require 3D printing only occasionally, or for one-offs that require unique material properties or applications. Service bureaus can also provide advice on various materials and offer value-added services such as design or advanced finishing.

The main downsides of outsourcing are cost and lead time. Often, outsourcing is a gateway to bringing production in-house as needs ramp up. One of the greatest benefits of 3D printing is its speed compared to traditional manufacturing methods, which quickly diminishes when an outsourced part takes multiple days or even weeks to arrive. With growing demand and production, outsourcing also rapidly becomes expensive.

Because of the rise of affordable industrial-quality 3D printing, today, more and more companies choose to bring 3D printing in-house right away, vertically integrating into existing shops or labs, or in the workspaces of engineers, designers, and others who could benefit from translating digital designs into physical parts or who are involved in small batch production.

Small format, desktop SLA 3D printers are great when you need parts quickly. Depending on the number of parts and printing volume, investment into a small format 3D printer can break even within months. Plus, with small format machines, it’s possible to pay for just as much capacity as a business needs and scale production by adding extra units as demand grows. Using multiple 3D printers also creates the flexibility to print parts in different materials simultaneously. Service bureaus can still supplement this flexible workflow for larger parts or unconventional materials.

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Fast turnaround time is a huge advantage to owning a desktop 3D printer. When working with a printing bureau, lead times, communication, and shipping all create delays. With a desktop 3D printer like the Form 3+, parts are in-hand within hours, allowing designers and engineers to print multiple parts in one day, helping to iterate faster and drastically reduce product development time and quickly test mechanisms and assemblies avoid costly tool changes.

Owning a desktop 3D printer results in significant savings over 3D printing service bureaus and traditional machining, as these alternatives rapidly becomes expensive with growing demand and production.

For example, to fulfill tight production deadlines, a process engineer and team at Pankl Racing Systems introduced SLA 3D printing to produce custom jigs and other low-volume parts directly for their manufacturing line. While in-house SLA was initially met with skepticism, it turned out to be an ideal substitute to machining a variety of tools. In one case, it reduced lead time for jigs by 90 percent—from two to three weeks to less than a day—and decreased costs by 80-90 percent.

	Cost	Lead Time
In-House SLA 3D Printing	$9–$28	5–9 hours
CNC Machining	$45–$340	2–3 weeks
Outsourced 3D Printing	$51–$137	1–3 weeks

Pankl Racing Systems significantly reduced lead times and costs by 3D printing custom jigs in-house.

With small format machines, it’s possible to pay for just as much capacity as a business needs and scale production by adding extra units as demand grows. Using multiple 3D printers also creates the flexibility to print parts in different materials simultaneously.

The Design and Prototyping Group at the University of Sheffield Advanced Manufacturing Research Centre (AMRC) runs an open-access additive manufacturing station with a fleet of 12 Form 2 stereolithography (SLA) 3D printers for hundreds of engineers working on diverse projects across the site.

Formlabs offers two high precision SLA 3D printing systems, a growing library of specialized materials, intuitive print preparation and management software, and professional services—all in one package.

To continue exploring SLA 3D printing, start with feeling the quality of SLA for yourself: Request a free sample 3D printed part in your choice of material to be mailed straight to your door.

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What is SLA 3D printing?

Get to know the basics of stereolithography, also known as SLA 3D printing. Find out why the original 3D printing technique is still so popular and cost-effective, learn about how SLA printing works and its parameters and discover which materials and options will best suit your custom part needs.

In this introduction to Stereolithography (SLA), we cover the basic principles of the process to determine whether it is suitable for your specific application. After reading this article you will be familiar with all the important aspects of SLA 3D printing.

If you are interested in Hubs' SLA printing processes, check out our SLA capabilities .

What is stereolithography?

Stereolithography (SLA) is an additive manufacturing process that belongs to the vat photopolymerization family. Also known as resin 3D printing , there are three main 3D printing technologies associated with vat polymerization: SLA, DLP and LCD. The three technologies all use a light source to cure a photopolymer resin but with the following differences:

Stereolithography (SLA) uses UV lasers as a light source to selectively cure a polymer resin.
Digital light processing (DLP) uses a digital projector as a UV light source to cure a layer of resin.
Liquid crystal display (LCD) uses an LCD display module for projecting specific light patterns.

SLA is one of the most widely used vat photopolymerization technologies. It is used to create objects by selectively curing a polymer resin, layer by layer, using an ultraviolet (UV) laser beam. The materials used in SLA are photosensitive thermoset polymers that come in a liquid form.

Patented in 1986, SLA was the first 3D printing technology. And even today, SLA is still the most cost-effective 3D printing technology available when parts of very high accuracy or smooth surface finish are needed. Best results are achieved when the designer takes advantage of the benefits and limitations of the manufacturing process.

What to watch: How do you print highly detailed parts with SLA?

Here's a short video that will teach you everything you need to know to get you started with SLA 3D printing in about 10 minutes.

How does SLA 3D printing work ?

SLA 3D printing works by first positioning the build platform in the tank of liquid photopolymer, at a distance of one layer height for the surface of the liquid.
A UV laser creates the next layer by selectively curing and solidifying the photopolymer resin.
During the solidification part of the photopolymerization process, the monomer carbon chains that compose the liquid resin are activated by the light of the UV laser and become solid, creating strong unbreakable bonds between each other.
The laser beam is focused in a predetermined path using a set of mirrors, called galvos. The whole cross-sectional area of the model is scanned, so the produced part is fully solid.
After printing, the part is in a not-fully-cured state. It requires further post-processing under UV light if very high mechanical and thermal properties are required.

The photopolymerization process is irreversible and there is no way to convert the SLA parts back to their liquid form. Heating these SLA parts will cause them to burn instead of melt. This is because the materials that are produced with SLA are made of thermoset polymers, as opposed to the thermoplastics that fused deposition modeling (FDM) uses.

Schematic of SLA printer

What are the print parameters of SLA?

Most print parameters in SLA systems are fixed by the manufacturer and cannot be changed. The only inputs are the layer height and part orientation (the latter determines support location).

Layer height: Ranges between 25 and 100 microns. Lower layer heights capture curved geometries more accurately but increase the build time and cost—and the probability of a failed print. A layer height of 100 microns is suitable for most common applications.

Build size: This is another parameter that is important for the designer. The build size depends on the type of SLA machine. There are two main SLA machine setups: the top-down orientation and the bottom-up orientation:

Top-down printers place the laser source above the tank and the part is built facing upwards. The build platform begins at the very top of the resin vat and moves downwards after every layer.
Bottom-up printers place the light source under the resin tank (see figure above) and the part is built upside down. The tank has a transparent bottom with a silicone coating that allows the light of the laser to pass through but stops the cured resin from sticking to it. After every layer, the cured resin is detached from the bottom of the tank, as the build platform moves upwards. This is called the peeling step.

The bottom-up orientation is mainly used in desktop printers, like Formlabs, while the top-down is generally used in industrial SLA systems. Bottom-up SLA printers are easier to manufacture and operate, but their build size is limited. This is because the forces applied to the part during the peeling step might cause the print to fail. On the other hand, top-down printers can scale up to very large build sizes without a big loss in accuracy. The advanced capabilities of these systems come at a higher cost.

The following table summarises the key characteristics and differences of the two orientations:

	Bottom-up (Desktop) SLA	Top-down (Industrial) SLA
Advantages	+ Lower cost + Widely available	+ Very large build size + Faster build times
Disadvantages	- Small build size - Smaller material range - Requires more post-processing due to extensive use of support	- Higher cost - Requires specialist operator - Changing material involves emptying the whole tank
Popular SLA printer manufacturers	Formlabs	3D Systems
Build size	Up to 145 x 145 x 175mm	Up to 1500 x 750 x 500mm
Typical layer height	25 to 100 µm	25 to 150 µm
Dimensional Accuracy	± 0. 5% (lower limit: ± 0.010–0.250 mm)	± 0.15% (lower limit ± 0.010–0.030 mm)

What are the characteristics of SLA 3D printing?

The main characteristics of SLA 3D printing are the necessary support structure, curling and layer adhesion.

Support structures

A support structure is always required in SLA. Support structures are printed in the same material as the part and must be manually removed after printing. The orientation of the part determines the location and amount of support. It is recommended that the part is oriented so that so visually critical surfaces do not come in contact with the support structures.

Bottom-up and top-down SLA printers use support differently:

Top-down SLA printers: S upport requirements are similar to those for FDM . They are needed to accurately print overhangs and bridges (the critical overhang angle is usually 30o). The part can be oriented in any position, and they are usually printed flat, to minimize the amount of support and the total number of layers.
Bottom-up SLA printers: Support requirements can be more complex. Overhangs and bridges must still be supported, but minimizing the cross-sectional area of each layer is the most crucial criterion: the forces applied to the part during the peeling step may cause it to detach from the build platform. These forces are proportional to the cross-sectional area of each layer. For this reason, parts are oriented at an angle and the reduction of support is not a primary concern.

On the left, a part oriented for a top-down SLA printer (minimizing support). On the right, a part oriented for a bottom-up SLA printer (minimizing cross-sectional area) A part printed in SLA after removing the support structures.

Marks on the locations where the support structures touched the part are visible

Curling

One of the biggest problems relating to the accuracy of parts produced via SLA is curling. Curling is similar to warping in FDM.

During the curing process, the resin shrinks slightly upon exposure to the printer's light source. When the shrinkage is considerable, large internal stresses develop between the new layer and the previously solidified material, which results in the part curling.

Support is important to help anchor at-risk sections of a print to the build plate and mitigate the likelihood of curling. Part orientation and limiting large flat layers is also important. Over-curing (for example by exposing the part in direct sunlight post-printing) might also cause curling.

The best way to prevent curling is to keep it in mind during the design process. Avoid large thin and flat areas wherever possible, or add a structure to prevent the part from curling.

Layer adhesion

SLA printed parts have isotropic mechanical properties. This is because a single UV laser pass is not enough to fully cure the liquid resin. Later laser passes help previously solidified layers to fuse together to a very high degree. In fact, curing continues even after the completion of the printing process.

To achieve the best mechanical properties, SLA parts must be post-cured, by placing them in a cure box under intense UV light (and sometimes at elevated temperatures). This greatly improves the hardness and temperature resistance of the SLA part but makes it more brittle. The results of the post-curing process mean:

Test pieces of parts printed in standard clear resin using a desktop SLA printer have almost twice as much tensile strength post-cure (65 MPa compared to 38 MPa).
Parts can operate under load at higher temperatures (at a max temperature of 58ºC compared to 42ºC).
The elongation at break is almost half (6.2% compared to 12%).

Leaving the SLA printed part in the sun can also cause curing. Although spray coating with a clear UV acrylic paint before use is highly recommended because extended exposure to UV light has a detrimental effect in the physical properties and appearance of SLA parts—they may curl, become brittle or change color.

Summary of the main characteristics of SLA 3D printing

The main characteristics of SLA are summarized in the table below:

	Stereolithography (SLA)
Materials	Photopolymer resins (thermosets)
Dimensional Accuracy	± 0.5% (lower limit: ±0.10 mm) – desktop ± 0.15% (lower limit ± 0.01 mm) – industrial
Typical Build Size	Up to 145 x 145 x 175mm – desktop Up to 1500 x 750 x 500mm – industrial
Common layer thickness	25–100 µm
Support	Always required (essential to producing an accurate part)

What materials are used for SLA printing?

SLA materials come in the form of liquid resins, which can be chosen based on the end use of the part—for example, thermal resistance properties, a smooth surface finish or abrasion resistant. As such, the price of the resin varies greatly, from about $50 per liter for the standard material, upwards to $400 per liter for specialty materials, such as castable or dental resin. Industrial systems offer a wider range of materials than desktop SLA printers, that give the designer a closer control over the mechanical properties of the printed part.

SLA materials (thermosets) are more brittle than the materials produced with FDM or SLS (thermoplastics) and for this reason SLA parts are not usually used for functional prototypes that will undertake significant loading. Advances in materials may change this in the near future.

The following table summarizes the advantages and disadvantages of the most commonly used resins.

Material	Characteristics
Standard resin	+ Smooth surface finish - Relatively brittle
High detail resin	+ Higher dimensionally accuracy - Higher price
Clear resin	+ Transparent material - Requires post processing for a very clear finish
Castable resin	+ Used for creating mold patterns + Low ash percentage after burnout
Tough or Durable resin	+ ABS-like or PP-like mechanical properties - Low thermal resistance
High temperature resin	+ Temperature resistance + Used for injection molding and thermoforming tooling
Dental resin	+ Biocompatible+ High abrasion resistant- High cost
Flexible resin	+ Rubber-like material- Lower dimensional accuracy

What are the options for SLA post-processing?

SLA parts can be finished to a very high standard using various post-processing methods, such as sanding and polishing, spray coating and finishing with a mineral oil. To find out more, read our extensive article on post-processing for SLA parts.

An SLA part printed in clear resin, each showing the different post-processing stages

What's the difference between desktop (prototyping) and industrial SLA 3D printers?

The two main types of SLA systems are desktop (prototyping) and industrial printers. Industrial SLA machines can produce more accurate components than their desktop counterparts (and maintain better accuracy over larger builds), and often make use of higher-cost materials. While desktop SLA can achieve tolerances between 150 and 300 microns, industrial printers are capable of tolerances as low as 30 microns for nearly any build size.

One of the biggest advantages of industrial SLA over desktop machines is the range of materials that industrial printers are able to print with. While desktop printers may use a flexible resin, industrial machines offer a large range of flexible resins each with varying mechanical properties.

One of the limitations of most industrial machines is that they produce parts using a top-down approach resulting in the need for large resin tanks (over 100L). This makes swapping between materials difficult and can increase lead time on parts. This also makes these machines more expensive to maintain.

For designs where cosmetic appearance is more important than function, desktop printers are generally adequate. If engineering properties like temperature resistance, castability and transparency are required, then industrial properties offer a greater range of solutions.

Compared to desktop printers, industrial machines are designed for repeatability and reliability. They can often produce the same part over and over again and do not need the high level of user interaction that desktop machines typically require.

Overall, SLA’s unique ability to batch produce intricate, customized parts makes it a popular method of manufacturing small parts, low-run production.

What are the advantages of SLA 3D printing?

SLA can produce parts with very high dimensional accuracy and with intricate details.
SLA parts have a very smooth surface finish, making them ideal for visual prototypes.
Speciality SLA materials are available, such as clear, flexible and castable resins.

What are the disadvantages of SLA 3D printing?

SLA parts are generally brittle and not suitable for functional prototypes.
The mechanical properties and visual appearance of SLA parts will degrade over time when the parts are exposed to sunlight.
Support structures are always required and post-processing is necessary to remove the visual marks left on the SLA part.

What are Hubs' top tips & tricks for SLA 3D printing?

Is SLA 3D printing the right manufacturing solution for your parts or products? These are our rules of thumb:

SLA 3D printing is best suited for producing visual prototypes with very smooth surfaces and very fine details from a range of thermoset materials.
Desktop SLA is ideal for manufacturing small injection-molded-like parts at an affordable price. Think "smaller-than-a-fist".
Industrial SLA machines can produce very large parts, as big as 1500 x 750 x 500mm).
Want to find out more? Read our complete guide to 3D printing.

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The Complete Guide to Stereolithographic (SLA) 3D Printing

Stereolithographic (SLA) 3D printing is gaining immense popularity due to its ability to produce highly accurate, isotropic and waterproof prototypes and models with fine details and smooth surfaces from various modern materials.

This comprehensive guide explains how SLA printing technologies work, why thousands of professionals use them today, and how this 3D printing technology can be useful in your work.

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The development of 3D printing technology continues to influence how companies approach prototyping and manufacturing. This technology is becoming more accessible, and equipment and materials are developing in accordance with the possibilities and requirements of the market. That's why today designers, engineers and others are integrating 3D printing into workflows at all stages of development.

3D printing is helping professionals across industries reduce recruitment costs, accelerate iteration, streamline manufacturing processes, and even discover entirely new business models.

Stereolithographic 3D printing technology has evolved significantly. In the past, resin 3D printers were monolithic and costly, requiring skilled technicians and costly service contracts to operate. Today's small desktop printers are highly flexible and produce industrial-quality products at a much lower cost.

Stereolithography is a type of additive manufacturing. It is also known as photopolymerization in the bath or 3D printing using polymer resin. Devices that use this technology have a common principle of operation: under the influence of a light source (laser or projector), a liquid polymer turns into a solid plastic. The main differences are in the location of the main components such as the light source, work platform and resin tank.

See how stereolithography 3D printing is done.

Stereolithographic 3D printers use light-sensitive curable materials called "polymers". When stereolithographic polymers are exposed to specific wavelengths of light, short molecular chains join together causing the monomers and oligomers to polymerize into either rigid or flexible patterns.

Graphical representation of the main mechanisms of stereolithographic 3D printing.

Models printed on SLA printers have the highest resolution and accuracy, the finest detail, and the smoothest surface of any 3D printing technology, but the main advantage of this method is its versatility.

Materials manufacturers have developed innovative formulas for stereolithographic polymers with a wide range of optical, mechanical and thermal properties similar to standard, engineering and industrial thermoplastic resins.

Comparison of 3D stereolithography with two other common plastic modeling technologies: Fused Deposition Modeling (FDM) and Selective Laser Sintering (SLS).

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Learn how to go from design to 3D printing with a Form 3 3D printer. Watch this 5-minute video to learn the fundamentals of using a Form 3 printer, from software and materials to processes printing and post-processing.

Use any CAD software or 3D scan data to design the model and export it to a 3D print file format (STL or OBJ). All printers based on SLA technology work with software that allows you to set print parameters and separate the digital model into layers. After the settings are complete, the model preparation software sends instructions to the printer via a wireless or cable connection.

More advanced users can design directly for SLA technology or, for example, print models with voids to save materials.

After a quick check of the settings, the printing process starts. The printer may run unattended until printing is complete. In printers with a cartridge system, material is replenished automatically.

Formlabs' online Dashboard allows you to remotely manage printers, resins, and employee access.

After printing is completed, models should be rinsed with isopropyl alcohol to remove resin residue from their surface. After the washed models have dried, some materials require final polymerization, a process that ensures the best possible strength and stability of the parts. Finally, remove the support structures from the models and sand down the remaining traces of the supports for a clean finish. Models produced with SLA technology can be machined, primed, painted or assembled depending on the intended use.

Final polymerization is particularly important for functional polymer resins used in engineering, dentistry and jewellery.

Engineers, designers, fabricators and others choose stereolithography 3D printing because it provides excellent detail, smooth surfaces, superior model fidelity, isotropy, and water resistance. In addition, it allows you to work with various materials.

Because 3D printing builds models layer by layer, the strength of finished parts can vary depending on the orientation of the part relative to the printing process: the X, Y, and Z axes will have different properties.

Extrusion-based 3D printing processes such as deposition filament modeling (FDM) are anisotropic due to a special approach to creating different layers during the manufacturing process. This anisotropy limits the application of FDM technology or requires additional changes in the design of the model to compensate for it.

Check out our detailed guide comparing FDM vs. SLA 3D printers to see how they differ in terms of print quality, materials, application, workflow, speed, cost, and more.

Stereolithographic 3D printers, on the other hand, allow the production of highly isotropic models. Achieving detail isotropy relies on a number of factors that can be tightly controlled by integrating the chemical composition of materials with the printing process. During printing, the components of the polymers form covalent bonds, but when creating subsequent layers, the model remains in an "immature" state of partial reaction.

When immature, the resin retains polymerizable groups that can form bonds between layers, giving the model isotropic and waterproof properties after final curing. At the molecular level, there are no differences between the X, Y, and Z planes. This results in models with predictable mechanical characteristics critical for applications such as jigs and fixtures and finished parts, as well as functional prototyping.

SLA printed parts are highly isotropic compared to FDM parts.

Due to its isotropic nature, stereolithographic printed models, such as this jig for Pankl Racing Systems, can withstand directional loads during the manufacturing process.

SLA printed objects are continuous, whether they are solid or have internal channels. Watertightness is important when it is necessary to control and predict the impact of air or liquid flows. Engineers and designers are using the water resistance of stereolithography printers for air and fluid flow applications in the automotive industry, biomedical research, and to test the design of parts in consumer products such as kitchen appliances.

OXO relies on the water resistance of stereolithographic printed models to create durable working prototypes of air and liquid products such as coffee makers.

Stereolithographic 3D printing is used to produce precise, reproducible components in a variety of industries, including dentistry and manufacturing. In order to produce accurate models during the printing process, many factors must be strictly controlled.

The quality of stereolithographic 3D printing is between standard and precision machined. SLA has the highest tolerance compared to other commercial 3D printing technologies. Learn more about tolerances, accuracy and precision in 3D printing.

The heated resin tank combined with the closed working environment provide virtually the same conditions for every model. The higher accuracy also depends on the lower printing temperature compared to thermoplastic-based technologies in which the raw material is melted. Because stereolithography uses light instead of heat, it prints at close to room temperature and models are not subject to thermal expansion and contraction.

Dental example (comparison of a scanned component with the original CAD model) demonstrating the ability to maintain tight tolerances for the entire stereolithographic model.

LFS stereolithography 3D printing involves an optic in a Light Processing Unit (LPU) that moves along the x-axis. parabolic mirrors so that it is always perpendicular to the plane of the platform, so it always moves in a straight line, ensuring maximum precision and accuracy. This allows consistency to be achieved as the size of the equipment increases, for example, when working with a large-sized Formlabs Form 3L stereolithography printer. The LPU also uses a spatial filter, which forms a clear laser spot.

The characteristics of the individual materials also play an important role in ensuring the reliability and reproducibility of print results.

Formlabs Rigid Resin has a high green modulus, or modulus of elasticity, before final polymerization, allowing you to print very thin models with high precision and reliability.

Stereolithography printers are considered the best 3D printers due to the smooth surface of the produced models, the appearance of which is comparable to parts produced by traditional methods such as machining, injection molding and extrusion.

This surface quality is ideal when a perfect finish is needed and also helps reduce post-processing time because these models are easy to sand, polish and paint. For example, large companies like Gillette use stereolithography 3D printing to create finished products such as razor handles in their Razor Maker platform.

Large companies like Gillette use stereolithography 3D printing to create finished products such as razor handles in their Razor Maker platform.

The Z layer height is often used to determine the resolution of a 3D printer. On Formlabs stereolithographic 3D printers, it can be adjusted from 25 microns to 300 microns to trade off speed and print quality.

FDM and SLS printers typically print Z-axis layers between 100 and 300 microns wide. At the same time, a part printed with 100 micron layers on an FDM or SLS printer is very different from a part printed with 100 micron layers on an SLA printer. Models printed on a stereolithographic printer have a smoother surface immediately after printing, because their outer walls are straight, and each new printed layer interacts with the previous one, smoothing out the effect of the stairs. When printed on an FDM printer, layers are often visible in models, and the surface of models printed on an SLS printer has a grainy structure due to sintered powder.

In addition, the stereolithography printer can print fine details: the Form 3 laser spot size is 85 microns, while industrial SLS printers have a laser spot size of 350 microns, and FDM-based devices use nozzles with a diameter of 250– 800 microns.

Models printed on FDM printers often show layer lines and may have inaccuracies around complex features. Models printed on stereolithography printers have sharp edges, a smooth surface, and almost imperceptible layer lines.

The advantage of SLA polymers lies in a wide range of formulations offering a variety of characteristics: they can be soft or hard, contain additives such as glass and ceramics, or have special mechanical properties such as high bending temperature under load or impact resistance. Materials can be designed for a particular industry, such as dentures, or have properties close to those of final materials to create prototypes that can be tested and run under stress.

Ceramic Resin can be 3D printed with a stone-like texture and then fired to create a ceramic product.

In some cases, it is this combination of versatility and functionality that is leading businesses to use polymer-based 3D printing in-house. After solving existing problems through the use of a certain functional polymer, other applications are usually quickly discovered. In this case, the printer becomes a tool for discovering the various properties of different polymers.

For example, hundreds of engineers in the Design and Prototyping group at the Advanced Manufacturing Equipment Research Center (AMRC) at the University of Sheffield have access to 12 stereolithographic 3D printers and various construction materials that they use in numerous research projects for these partner companies like Boeing, Rolls-Royce, BAE Systems and Airbus. They printed High Temp Resin washers, brackets, and a mounting system for a sensor that must operate in high temperature conditions, and used Durable Resin to create complex spring components for a material handling robot as part of a composite manufacturing automation system.

AMRC engineers have access to 12 stereolithographic 3D printers and various construction materials, allowing them to create custom-designed parts for a variety of research projects, such as brackets for a stacking robot (above) and mounts for an environmental sensor. high temperature (below).

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Stereolithographic 3D printing makes it easier for businesses across industries to innovate. Such industries include engineering, manufacturing, dentistry, healthcare, education, entertainment, jewelry, and audiology.

Rapid prototyping with 3D printing enables engineers and developers to turn ideas into working proofs of concept, transform concepts into high-quality prototypes that look and work like end products, and take products through testing phases to launch into mass production.

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By creating the necessary prototypes and 3D printing special tools, molds and production aids, manufacturing companies can automate production and optimize workflows at a much lower cost and in much faster time than traditional manufacturing. Thus, production costs are reduced and defects are prevented, quality is improved, assembly is accelerated and labor productivity is increased.

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Digital Dentistry reduces the risks and uncertainties associated with human error, enabling consistent quality and precision at every step of the workflow, and improving patient care. 3D printers can produce a range of high quality custom products at low cost, providing exceptional fit and reproducible results.

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3D printers are multifunctional tools for creating immersive learning and research environments. They stimulate creativity and introduce students to professional-level technology, enabling the implementation of the STEAM method in the fields of science, technology, art and design.

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Affordable, professional-grade desktop 3D printers help clinicians produce medical devices that meet individual needs and improve patient outcomes. At the same time, the organization significantly reduces time and money costs: from laboratories to operating rooms.

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High resolution printed physical models are widely used in digital sculpting, 3D character modeling and prop making. 3D-printed models have been featured in animated films, video game characters, theatrical costumes, and even special effects for blockbuster films.

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Professional jewelers use the power of CAD and 3D printing to rapidly prototype, customize jewelry to customer specifications and produce large batches of blanks for casting. Digital tools allow you to create dense, highly detailed models without the tedious, error-prone production of stencils.

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Hearing professionals and labs use digital workflows and 3D printing to simplify the production of high-quality custom and hearing aids, as well as to mass-produce behind-the-ear hearing aids, hearing protectors, custom earmoulds, and headphones .

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Many companies are starting to use 3D printing technology through service bureaus and laboratories. Outsourcing can be a great solution when the need for 3D printing is infrequent or you need to do one-off jobs using materials that have unique properties or produce special models. Service bureaus can also provide advice on various materials and offer additional services such as design or improved finishes.

The main disadvantages of outsourcing are the high cost and duration of production. Often, outsourcing becomes a step on the way to in-house production as needs grow. One of the main advantages of 3D printing is its speed compared to traditional production methods. But it is noticeably reduced when the delivery of the model produced by the involved organization takes several days or even weeks. As demand and production capacity increase, the costs of outsourcing are rising rapidly.

With the increasing availability of industrial quality 3D printing today, more companies are opting to bring 3D printing into their factory right away, vertically integrating it into existing workshops or labs, or providing printers to engineers, designers and other professionals who benefit from digital transformation. projects into physical models or are engaged in the production of products in small batches.

Compact desktop stereolithography 3D printers are an excellent solution for rapid model production. Depending on the number of parts needed and the volume of prints, the investment in a compact 3D printer can pay for itself in just a few months. In addition, compact appliances allow you to purchase just the amount of equipment you need to run your business and scale your production by adding more units as demand grows. Using multiple 3D printers also allows you to print models from different materials at the same time. And when the need arises for the production of large parts or the use of non-standard materials, service bureaus can come to the rescue.

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High production speed is an important reason to buy a desktop 3D printer. When working with a print bureau, there are delays related to the speed of production, communication and delivery. A desktop 3D printer like the Form 3 delivers models in hours, allowing designers and engineers to print multiple parts a day. This contributes to faster iterations and significant time savings in product development, as well as rapid testing of mechanisms and assemblies, avoiding costly tool changes.

Purchasing a desktop 3D printer saves a lot of money by eliminating bureau services and traditional processing methods, as their cost rises sharply with increasing demand and production volumes.

For example, the production engineer and others at Pankl Racing Systems used stereolithographic 3D printing technology to produce products on a tight schedule. This allowed them to independently manufacture custom-designed jigs and other small-sized components for the production line. While stereolithography was initially viewed with skepticism, this technology proved to be an ideal solution to replace the machining of a number of tools. In one of the cases, it made it possible to reduce the manufacturing time of conductors by $51-137

By 3D printing custom-designed jigs, Pankl Racing Systems has significantly reduced both order preparation time and production costs.

Compact units allow you to purchase just the amount of equipment you need to run your business and scale your production by adding new units as demand grows. Using multiple 3D printers also allows you to print models from different materials at the same time.

The University of Sheffield's Manufacturing Advanced Research Center (AMRC) has an additive manufacturing station with 12 Form 2 stereolithographic (SLA) 3D printers that hundreds of engineers working on various projects have access to.

Formlabs offers two high-precision stereolithographic 3D printing systems, an ever-expanding range of specialty materials, intuitive print preparation and process management software, and professional services, all in one solution.

To learn more about 3D stereolithography, experience it for yourself: request a free printed sample in your choice of material, delivered right to your door.

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