PolyJet vs. SLA: Differences and Comparison
Learn about the differences between these two 3D printing technologies.
PolyJet and SLA (stereolithography) are resin-based 3D printing technologies that use UV light to cure a liquid resin. Although both technologies print layer by layer, SLA uses a laser to outline a layer on the current surface of a tank of resin, while the platform drops deeper into the vat on each pass. PolyJet printers, on the other hand, build up a 3D model by spraying tiny droplets onto a dry building plate and a UV lamp is used to cure each layer as the model is printed. Other than the working principle, the key differences when comparing PolyJet to SLA lie in the materials they use and their applications.
The Polyjet process can print using a more versatile set of materials. Its biggest advantage is that it allows for multi-material printing – a part can be printed using multiple materials, at the same time. Although Polyjet can print small parts faster, this advantage disappears when the parts are larger than five cubic inches. PolyJet and SLA printers are similarly priced in terms of both raw materials and printing equipment. This article will further compare PolyJet vs. SLA 3D printers, including their advantages, disadvantages, similarities, and differences.
PolyJet Definition and Comparison to SLA
PolyJet 3D printing was developed by Objet-Geometries in 2000. A PolyJet printer functions a lot like an inkjet printer. However, instead of drops of liquid ink, the PolyJet works by jetting droplets of photopolymer, layer upon layer, to form a 3D model. Each layer solidifies when exposed to UV light as the model is systematically built up.
SLA and PolyJet have fast printing speeds. PolyJet is the fastest printer for models that fit within a 5’’ cube. The speed declines outside of these limits, however. The printing speed of SLA is not dependent on the size of the model. In other aspects, PolyJet has some distinct advantages compared to SLA. PolyJet is not restricted to only resin-based printing. It can print a range of materials with different properties. These printers are also capable of higher production volumes compared to SLA. Although, Polyjet is limited in terms of build volume -- it is not suitable for manufacturing large-format parts.
PolyJet printers have multiple heads that can simultaneously lay down the final part material as well as the support material. In many cases, the support material can wash off with a water jet– eliminating the need for a time-consuming post-production process. Depending on the thickness of the support material, a chemical batch or a combination of a chemical bath, peeling, and washing off the support may be required. SLA, on the other hand, is limited by breakaway support material and is overall a very messy process. Post-processing steps with SLA have to be done manually and are very labor-intensive. The image below is an example of a PolyJet 3D printer:
To learn more, see our guide on the PolyJet Process.
Advantages of Disadvantages of PolyJet Compared to SLA
- PolyJet is more versatile than SLA. It has multi-material and multi-color capabilities.
- PolyJet parts have good tensile strength. This process can produce strong, sturdy, durable products.
- PolyJet is better in terms of resolution offerings.
- PolyJet-printed parts are sufficiently cured after printing. SLA, on the other hand, needs a UV oven to fully cure the part.
- PolyJet is capable of higher production volumes compared to SLA.
There's one key disadvantage, of PolyJet over SLA, though - it is usually more costly because the materials used are often more expensive.
SLA Definition and Comparison to PolyJet
Invented in the 1980s, SLA was the world's first 3D printing technology. It was invented by Chuck Hull, who later became the founder of 3D Systems. An SLA printer uses a UV laser to outline successive layers of the desired part at the surface of a tank of liquid resin. The build platform gradually retracts down into the tank, exposing fresh liquid resin for the laser to trace on its next pass. Exposing the liquid resin to the UV laser beam solidifies and hardens the resin and joins the just-deposited material to the layer below. After the product is completely printed, the model is submerged in a chemical bath for cleaning. Post-processing is done by manually removing the breakaway support and placing the model in a UV oven to cure. Sanding may also be necessary to achieve a smoother surface.
Compared to PolyJet, SLA is more useful for large prototypes and hollow structures. SLA uses an internal honeycomb structure to form high-quality hollow parts. PolyJet, on the other hand, is more useful for printing smaller models or parts. SLA is also used for prototypes in various industries, including healthcare and jewelry. The image below shows how an SLA 3D printer works:
To learn more, see our guide on SLA Technology.
Advantages and Disadvantages of SLA Compared to PolyJet
An advantage of SLA over PolyJet is that SLA can print mostly hollow parts using an interior honeycomb structure. Compared to PolyJet, SLA has the following disadvantages:
- SLA printers are not as stable as PolyJet printers. This results in variations of duplicate prints.
- SLA is not as versatile as PolyJet printers. SLA does not include multi-material capabilities and has limited color options (gray, white, and clear).
- SLA layers are thicker than PolyJet, with a minimum layer thickness of roughly 50 microns. PolyJet has a minimum layer thickness of 16 microns.
- SLA products are known to be brittle and fragile and are therefore not ideal for functional prototypes.
- SLA is messy, in terms of resin spills and post-processing processes, and can give off an odor.
| Attribute | PolyJet | SLA |
|---|---|---|
Attribute UV-curable | PolyJet Yes | SLA No |
Attribute Multi-material capability | PolyJet Yes | SLA No |
Attribute Degrades over time with light and heat exposure. | PolyJet Yes | SLA Yes |
Attribute Good tensile strength | PolyJet Yes | SLA No |
Attribute Layer thickness | PolyJet ≥16µm | SLA ≥50µm |
Attribute Accuracy and detail | PolyJet Small detailed prototypes and intricate patterns | SLA Large models and intricate patterns |
Attribute Resolution | PolyJet Excellent resolution at 0.00063’’ | SLA Good resolution at 0.005-0.002 |
Attribute Color options | PolyJet All colors, opaque and translucent | SLA Gray hues |
Attribute Printing speed | PolyJet Very fast | SLA Very fast |
Attribute Cost | PolyJet $6,000 to $75,000+ | SLA $1,200 to $100,000+ |
Table: PolyJet vs. SLA Comparison
Other Comparisons And Things to Consider
Technology comparison: SLA is well-established, while PolyJet is newer. PolyJet printers work by spraying droplets of photopolymer, layer upon layer, to form a 3D model on a building tray. A UV light is used to cure the resin. SLA, on the other hand, uses a laser beam to print a 3D model from the resin tank.
Material comparison: PolyJet allows for a lot of versatility in terms of material selection. It can print rigid and flexible parts simultaneously in multiple colors. This is a unique feature that sets the PolyJet apart from most 3D printers. SLA, on the other hand, is limited to one material per printed object, with limited colors (gray hues).
Applications comparison: The selection of either PolyJet or SLA will come down to the end product and its applications. PolyJet is one of the only printer types that allows for multi-color, multi-material printing. It is unmatched in terms of versatility. When printing with comparable materials, SLA performs better in larger prototypes, whereas PolyJet is better for smaller parts with finely detailed printing.
PolyJet printers are used in various industries including medical, architecture, dentistry, and automotive. SLA printing, on the other hand, is used in industries such as jewelry, and healthcare.
Volume comparison: PolyJet has a higher print volume than SLA—it is capable of producing more parts. However, the actual print volumes of both these types of printers are dependent on the model of printer used. In terms of build volume, SLA is capable of larger build volumes, whereas PolyJet is limited to smaller-sized prints.
Surface finish comparison: SLA and PolyJet both produce parts with a smooth surface finish. The difference is that PolyJet-printed parts have a smooth surface right off the build. SLA, on the other hand, requires sanding to achieve a smoother surface finish.
Cost comparison: PolyJet and SLA are comparable in price. Although SLA has a broader range of available features, and therefore, a wider price range. In terms of material cost, PolyJet materials are typically more expensive due to their superior versatility and more expensive materials that cannot be used with SLA.
Mutual Alternatives to PolyJet and SLA
Some alternatives to PolyJet and SLA 3D printing include:
- FDM: FDM (Fusion Deposition Modeling) is a material extrusion method that is specifically suited to printing in plastic and requires support structure much like SLA. Its similarity to PolyJet is that both technologies use an orthogonal printer transport mechanism for Z-axis layering.
- SLS: SLS (Selective laser sintering) and SLA both use lasers to fuse material. PolyJet and SLS produce parts with isotropic properties.
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