SLA vs. PolyJet 3D Printing: In-Depth Comparison

While PolyJet and SLA 3D printers both create high-resolution resin parts, there are various benefits and drawbacks for specific applications. As such, it is helpful to evaluate their comparative strengths and weaknesses in a few key categories.

One of the main differences between PolyJet and SLA printers involves costs. As SLA patents began to expire at the end of the 2000s, and smaller format, desktop SLA 3D printers were introduced to the market, the cost of SLA printers decreased by 100x. Today, prices for professional SLA printers start at about $3,750, while large format benchtop printers start at $11,000. 

In contrast, PolyJet printers are substantially more expensive, with prices ranging from $30,000 to $500,000+. This is only the machine cost, compulsory service plans can cost up to 20% of the price of a PolyJet printer annually, which is enough to buy a fleet of SLA printers each year.

In addition, PolyJet materials are generally two to three times more expensive than SLA resins. As a result, the overall cost per part for PolyJet prints is many times higher than that of an SLA print. PolyJet printers also require more maintenance, increasing the amount of labor necessary to operate these machines. 

Thus, unless you specifically need PolyJet for a certain application, such as full-color models or multi-material parts, you are likely to see a higher return on your investment with an SLA printer.

Because 3D printing is an additive process, each layer introduces an opportunity for inaccuracy, and the process by which layers are formed affects the level of precision, defined as the repeatability of the accuracy of each layer. 3D printing tolerances, accuracy, and precision depend on many different factors: the 3D printing process, materials, software settings, post-processing, and more. 

Both PolyJet and SLA 3D printers are among the most accurate and precise 3D printing processes, with tolerances around ± 0.2% (lower limit: ± 0.1 mm). Thanks to the highly-precise light sources, these processes can achieve fine details and can consistently produce high-quality results. 

Depending on the model geometry, PolyJet and SLA 3D printed parts require support structures, which can be essential to achieve dimensional accuracy, especially with complex geometries or large and thin walls.

With SLA, supports are removed manually during post-processing. Formlabs LFS printers offer enhanced light touch support structures that detach from parts in seconds to save post-processing time. SLA printed parts are also known for their smooth surface finish, which, depending on the material, can be matte or glossy.

With PolyJet printers, support structures are washed away during post-processing with a water jet. This workflow exerts forces on the parts and can break intricate details or bend thin walls. PolyJet printers can print with a matte and glossy surface. However, glossy finish is only limited to sections of the model, where support material is not used.

One of the biggest differences between PolyJet and SLA is the availability of materials, which also defines the possible applications for these printers.

Depending on the printer model, most PolyJet 3D printers support around five to ten different materials. These range from standard prototyping materials, to materials in different colors, clear materials, and biocompatible materials. More high-end ​​PolyJet 3D printers also support printing with multiple materials at the same time, enabling novel applications such as printing multicolor and multi-material prototypes. 

However, PolyJet printers can only print with low-viscosity materials, which severely limits the range of properties available. PolyJet materials also have a low heat deflection temperature (HDT), generally around 45-50 °C, which means that they can even start to creep and lose shape under strong light. As a result, PolyJet printing is only ideal for concept modeling and non-functional prototyping applications, as well as some dental and medical applications that require biocompatibility.

SLA 3D printers support a much wider range of materials than a typical PolyJet printer, with up to 30+ materials for Formlabs 3D printers. SLA resins can be flexible or stiff, clear or opaque, heavily filled with secondary materials like glass, wax, or ceramic, or imbued with mechanical properties like high heat deflection temperature or impact resistance. 

SLA materials can closely match common end-use thermoplastic materials for rapid prototyping, with specific materials formulated to be soft-touch, thermally and chemically resistant, highly durable, or dimensionally stable under load. SLA 3D printing also offers the widest range of biocompatible materials for dental and medical applications.

The workflow for both PolyJet and SLA 3D printing consists of three steps: designing, 3D printing, and post-processing.

See how to go from design to 3D print with the Form 3+ SLA 3D printer. 

First, use any CAD software or 3D scan data to design a model, and export it in a 3D printable file format (STL or OBJ). 3D printers then require print preparation or slicer software to specify printing settings and slice the digital model into layers for printing.

Both PolyJet and professional SLA 3D printers come with their own proprietary software and predefined settings for each material that have been thoroughly tested to ensure the highest print success rate.

Setting up prints with advanced print preparation tools like PreForm is plug-and-play. PreForm is a free download, try it now.

Once the 3D printing process begins, 3D printers can run unattended, even overnight, until the print is complete. Both PolyJet printers and advanced SLA 3D printers like the Form 3+ and the Form 3L offer a cartridge system that refills the material automatically.

To post-process parts, you will need to manually remove support material from a PolyJet printed part using a water jet or a combination of chemical baths and peeling for thick supports. This can bend parts with thin walls and also easily break delicate features. PolyJet parts don’t require post-curing—the models come off the printer fully cured.

PolyJet printers often require more maintenance than a typical SLA printer. You will need to clean the print head, build tray, and roller after every use. In addition, you will need to clean the UV lamps and wiper daily and perform regular tests to ensure that your printer remains in working condition. 

PolyJet printers also require setup and training with on-site installation. The more complex workflow and the steeper learning curve mean that the system requires a skilled technician in-house to operate and maintain.

SLA parts require rinsing in isopropyl alcohol (IPA) or alternative solvents to remove any uncured resin from their surface. Using the standard workflow, this involves first removing parts from the build platform, then manually soaking them in a bath of solvent to clean off excess resin.

Professional solutions such as the Form Wash and the Form Wash L automate this process. Parts can be transferred directly from the printer to Form Wash or Form Wash L, which agitates the solvent around the parts to clean them and automatically raises parts out of the alcohol bath when the process is finished.

After rinsed parts dry, some SLA materials require post-curing, a process that helps parts to reach their highest possible strength and stability. This can also be automated with curing solutions like the Form Cure and the Form Cure L. 

Support removal for SLA parts requires cutting away the support structures and lightly sanding the parts to remove support marks. Formlabs’ Low Force Stereolithography (LFS)™ technology offers light-touch supports, which allow an entire object to be torn away from its support base in seconds, leaving minimal markings and reducing time spent post-processing.

Besides keeping the printer and the work area tidy, professional SLA 3D printers generally don’t require regular maintenance. The easy workflow also empowers anyone at a company to use an SLA printer independently after less than one hour of training.

When further post-processing is required, both PolyJet and SLA parts can be machined, primed, painted, and assembled for specific applications or finishes. 

PolyJet printers are available in various sizes, from smaller benchtop models to large multi-ton industrial machines. Due to the differences in technology, developing larger PolyJet machines is less complex. 

The first SLA 3D printers were mainly large industrial machines that offered large build volumes, but often at an even higher cost than PolyJet and with a much more complex workflow. However, thanks to the rapid development of the SLA printing technology, SLA printers are now available in both compact desktop and large format benchtop forms.

The inverted SLA process behind more accessible desktop and benchtop SLA printers reduces footprint and cost, but heightened peel forces introduce limitations around materials and build volume, and larger parts would require sturdy support structures to print successfully.

With the introduction of the Low Force Stereolithography (LFS) print process that powers the Form 3 and Form 3L, Formlabs has completely re-engineered the approach to resin-based 3D printing to drastically reduce the forces exerted on parts during the print process. Uniform linear illumination and the low forces from the flexible tank mean LFS technology can seamlessly scale up to a larger print area built around the same powerful print engine.

The first affordable large format resin printer, the Form 3L, delivers large parts fast, using two staggered light processing units (LPUs) that work simultaneously along an optimized print path. Delivering a build volume five times larger than current SLA printers, the Form 3L removes size restrictions that sometimes hinder workflows on smaller desktop devices, while maintaining a competitive price point.

Both PolyJet and SLA are considered some of the fastest 3D printing technologies. 

PolyJet 3D printers provide very fast printing speeds within a five-inch cube, but for larger models and builds the printing speed slows down significantly as the print head has to travel farther, which causes the layers to take a longer amount of time to complete. Lasers and galvanometers in SLA printers are just as fast for large builds as well as small builds.

PolyJet printers also have a limited range of automated post-processing solutions available, so while the actual printing process may be faster, post-processing is often slower and more labor-intensive with a PolyJet printer.

Speed can also depend on the material choice. Printing four times faster than Formlabs standard SLA materials, Draft Resin is a fast-printing resin that is ideal for initial prototypes, rapid iterations, as well as dental and orthodontic models. From fast print initiation speeds to minimal support removal, wash, and cure times, Draft Resin has an optimized workflow to truly maximize efficiency.

Each 3D printing technology has its own strengths, weaknesses, and requirements, and is suitable for different applications and businesses. The following table summarizes some key characteristics and considerations when comparing PolyJet vs. SLA 3D printers.

Both PolyJet and SLA 3D printing technologies have unique benefits, from high accuracy and precision, to a smooth finish, fast prints, and high-performance materials. However, SLA technology has evolved faster and provides unique benefits, especially considering the cost, ease of use, and the possible range of applications.

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. Curious to see the quality firsthand? Order a sample part shipped to your office.