PolyJet vs. SLS: Differences and Comparison
Learn about the differences between these two 3D printing technologies.
PolyJet prints 3D files, by inkjet application and UV curing of acrylic resins in each printhead pass. This builds up a 3D outcome from 2D slices of a model. PolyJet makes models of high-resolution and fine detail. Meanwhile, SLS (Selective Laser Sintering) renders 2D slices of 3D models to build a 3D representation of the file.
The main difference when comparing PolyJet vs. SLS is in the part resolution, properties, and cost of producing parts. SLS parts offer poorer resolution/cosmetics than PolyJet, but greater strength. PolyJet parts, on the other hand, have poorer material properties but a wider choice of materials and better model properties.
This article will discuss in detail the differences between PolyJet vs. SLS, their alternatives, and the advantages and disadvantages of both.
PolyJet originated from Objet and was first marketed in 2009 as the Eden brand. Over the years, PolyJet equipment and resins have improved, allowing multi-material printing. PolyJet remains patent-protected, preventing direct competition. This resulted in a high cost of materials and machines. PolyJet works by jetting resin into the build platform using a printhead. A UV light is used to cure the resin into the final product.
Compared to SLS, PolyJet-printed parts have smoother surfaces and eight times higher resolution for finer features. The image below is an example of a PolyJet 3D printer:
PolyJet 3D printer.
Image Credit: Shutterstock.com/Moreno Soppelsa
Listed below are the advantages of PolyJet over SLS:
- PolyJet offers a wider range of material properties than SLS, which is limited to nylons.
- Resolution and speed can be selected in PolyJet while both are fixed in SLS.
- PolyJet offers the highest resolution, allowing fine features to be represented.
- Z resolution in PolyJet allows smoother surfaces.
- PolyJet equipment is safe, whereas SLS uses a powerful laser.
Listed below are the disadvantages of PolyJet compared to SLS:
- PolyJet materials are ten times the price of those for SLS.
- Resin is required to build support structures in PolyJet, whereas SLS powder acts as support and can be reused.
- PolyJet models are weaker than SLS equivalents.
- PolyJet’s regular head cleaning results in wastage, whereas SLS has zero waste.
- PolyJet requires skilled manual labor to remove supports, whereas SLS models are simply shaken clean.
- PolyJet requires constant, skilled cleaning and calibration, whereas SLS machines are very simple to maintain.
SLS originated at the University of Texas in the 1980s. It was early funded by Darpa, and brought to market by DTM Inc. SLS builds 2D slices of 3D models to print solid 3D representations of complex part files. The machines apply a layer of powder onto a build table. The particles are then fused together using a CO2 laser following a G-Code path to couple the powder both to itself and the layer below. This returns the powder to solid, much like molded material, but with resolution limited by light-beam diameter.
SLS material is nylon powder, available from multiple suppliers. This means the price is generally around $50 per kg. Unlike SLS, PolyJet offers lower material strength, a wider range of material properties, higher resolution, and high-quality finishing. Below is an example of an SLS 3D printer:
An SLS 3D printer.
Image Credit: Shutterstock.com/Moreno Soppelsa
Listed below are the advantages of SLS over PolyJet:
- SLS materials are 10% of the price of PolyJet materials.
- The powder bed acts as a support structure for free, as the material can be reused.
- SLS builds the strongest plastic models in the 3D printing sector.
- SLS processes result in near-zero wastage of build material.
- SLS parts cleanup is easy, simply by shaking off the unfused powder.
- SLS has lower machine servicing required compared to PolyJet.
Listed below are the disadvantages of SLS compared to PolyJet:
- SLS offers the narrowest range of material properties.
- SLS offers lower resolution in X, Y, and Z dimensions than PolyJet.
- SLS models are stepped, and the powder grain size makes the surface rough compared to PolyJet.
- SLS models have a sandlike surface that is impossible to smooth for cosmetic finishing whereas PolyJet can be polished.
- SLS uses hazardous equipment, with a high-power laser to fuse the powder.
Part wall thickness
0.2 mm walls are feasible
1.2 mm practical limit
Wide range of materials
Low support waste
Low process waste
High material strength
Smooth surface finish
Table. PolyJet vs. SLS Comparison
PolyJet is an intricate technology that delivers accurate 3D representations, including fine details. SLS is a simpler process that delivers the overall shape of 3D files but lacks fine detail. SLS is unlikely to get extensive further development. PolyJet has not reached its resolution limit and continues to develop.
PolyJet materials are complex resins, offering a range of properties. They are available in several rigid versions and hardnesses of rubber and also lens/light-pipe clear and biocompatible. PolyJet materials typically cost $200 to 500 per kg. SLS material is finely divided nylon powder. This offers few options in build but results in low porosity models that have the strength of molded parts. SLS materials cost ~$50 per kg.
PolyJet suits a very wide range of applications including: cosmetic and sanded/painted parts, engineering assessment models with all features present, flexure and compliant parts for spring/resilience evaluation, overmolds, lenses/light pipes, and rubber parts for seals.
SLS is ideally suited to the production of highly stressed parts for evaluation purposes – if cosmetics are not important. These models also serve well in design evaluation models for relatively simple and thick-sectioned parts.
The range of build volumes for SLS is limited. The largest SLS machine has a build size of 600 x 300 x 300 mm. The largest PolyJet machine, on the other hand, has a build size of 1000 x 800 x 500 mm.
PolyJet offers the best surface finish. Its parts are amenable to hand finishing and painting and can produce the highest quality cosmetics. SLS parts offer a poorer resolution. The powder process results in a sandy surface that does not suit post-processing.
PolyJet machines, materials, and processes are among the most expensive, and so the equipment is not widespread. SLS machines and materials are less costly than their PolyJet equivalents. This results in SLS parts being lower priced.
Various alternative 3D printing systems are also commercially available for both SLS and PolyJet, each with a group of beneficial characteristics:
- SLA: Stereolithography (SLA) uses a laser to fuse material, in a similar way to SLS. PolyJet and SLA, on the other hand, are both resin-based 3D printing options that deliver accurate end products.
- FDM: Fused Deposition Modeling (FDM) extrudes a heated plastic filament to “draw” a model slice – fused to itself and the layer below. Like SLS, FDM can rapidly produce parts for prototyping and proofs-of-concept. FDM also offers a range of material properties like PolyJet.
PolyJet and SLS have several similarities including:
- PolyJet and SLS share the same principle of z layering using an orthogonal printer transport mechanism and building with polymers.
- Both technologies produce isotropic parts, equally strong in all axes because of the nature of the material application and the quality of the intra-layer fusion.
- When correctly specified for the application, both processes make high-quality parts that are fit for service.
The following 3D printing technologies are also comparable to PolyJet:
- PolyJet vs. Multijet: Multijet is a similar process to PolyJet in that it also uses liquid photopolymers. These are cured by UV lamps to build parts for prototypes and proof-of-concept. For more information, see our article on PolyJet vs. Multijet.
The following 3D printing technologies are also comparable to SLS:
- SLS vs. DMLS: DMLS (Direct Metal Laser Sintering) is a technology used mainly for metal 3D printing. Like SLS, DMLS uses a powder bed fusion that produces parts with isotropic properties. For more information, see our article on SLS vs. DMLS.
This article summarized the differences between PolyJet and SLS 3D printing technologies.
To learn more about PolyJet vs. SLS and to help select the perfect technology for your products, contact a Xometry representative.
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