Photosensitive resin 3d printing

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.

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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Resin: 132 products

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• 3DJAKE Isopropyl Alcohol 1 liter
  • Isopropyl Alcohol 99.9%
  • Very effective
  • Good cleaning properties

• Anycubic Wash & Cure 2. 0
  • 2 in 1 solution
  • Easy handling
  • 360 ° treatment

• 3DJAKE Color Mix Resin Basic 500 g, 1.000 g
  • Pixel accurate 3D printing (4K compatible)
  • Hardly noticeable smell
  • Excellent material properties

• 3DJAKE ecoResin Light Grey 500 g, 1.000 g
  • Budget-friendly
  • Low odour
  • Fast curing

• Liqcreate Castable Wax 250 g, 1. 000 g
  • High precision
  • Wax-based
  • Clean and ash-free burnout

• Phrozen Aqua Resin Grey 4K 1.000 g
  • Low shrinkage
  • High resolution
  • Low viscosity and odour

• Liqcreate Premium Flex 250 g, 1.000 g
  • High elongation
  • Soft-touch
  • Easy to print

• 3DJAKE ecoResin Jet Black 500 g, 1. 000 g
  • Budget-friendly
  • Low odour
  • Fast curing

• Elegoo Mercury Plus 2.0
  • Cleaning and curing
  • Intelligent curing control
  • 360° treatment

• Phrozen Aqua Resin Blue 1.000 g
  • Low shrinkage
  • Low viscosity and odour
  • Fast printing

• 3DJAKE Resin Filter Set 1 set
  • Easy cleaning
  • Separates resin from particles
  • Easy to use

• Phrozen Aqua Resin Ivory 4K 1. 000 g
  • Low shrinkage
  • High resolution
  • Low viscosity and odour

• Liqcreate Premium Model 250 g, 1.000 g
  • Opaque resin
  • Matt colour
  • For all open source LCD & DLP 3D printers

• Liqcreate Flexible-​X 250 g, 1.000 g
  • High elasticity
  • Good tear resistance
  • Especially suitable for industrial parts

• 3DJAKE Resin Standard Black 500 g, 1. 000 g
  • For LCD / MSLA printers
  • Easy to use
  • Good adhesion

• 3DJAKE Resin Standard Dark Grey 500 g, 1.000 g
  • For LCD / MSLA printers
  • Easy to use
  • Good adhesion

• 3DJAKE Resin Cleaner 500 ml, 1.000 ml, 5.000 ml, 10.000 ml
  • Low odour
  • Ease of use
  • Suitable for ultrasonic cleaners

• Liqcreate Strong -​ X 250 g, 1. 000 g
  • High Strength
  • High Rigidity
  • High Temperature Resistance

• Liqcreate Composite-​X 375 g, 1.500 g
  • High rigidity and flexural strength
  • Excellent chemical resistance
  • Ideal for both industrial and private use

• Phrozen ABS-​like Resin -​ Grey 1.000 g
  • ABS-like
  • High resolution
  • High hardness

• Anycubic Wash & Cure Plus
  • For larger resin prints
  • 2-in-1 solution
  • Powerful cleaning device

• 3DJAKE Resin Colorant Transparent Red 12,50 g, 25 g
  • Transparent and opaque colours
  • Beautiful colouring
  • High quality

• Phrozen Aqua Resin Grey 8K 1. 000 g
  • 3D models in high resolution
  • Shore D85
  • Fast and precise printing

• Phrozen Water-​Washable Resin -​ Black 1.000 g
  • Washable with water
  • Robust
  • Universally applicable

All prices incl. VAT.

405nm photosensitive resin suitable for SLA, DLP, LCD 3D printers.

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