Polyjet vs. Inkjet: Differences and Comparison
Learn about how inkjet technology is used in Polyjet 3D printers.
Inkjet technology was first invented for use in 2D printers. This method deposits small droplets of different colored inks on a page to create an image. The 3D printing version of inkjet technology is not much different than the 2D version: it deposits multiple droplets of different colors or photopolymer materials onto a build platform and then cures the “printed” layer using a UV light. This process is repeated until the entire part has been printed, layer by layer.
Polyjet printing is a type of inkjet printing. It uses the same types of materials and the same type of curing process. Polyjet machines can print extremely quickly compared to other technologies and can create complex multi-material and multicolor parts.
This article will compare polyjet to basic inkjet printers as well as to laser-based printing technologies.
Polyjet Definition and Comparison to Inkjet
Polyjet is a trademark for a multijet, modeling-based 3D printing technology developed by Stratasys. The multijet process was first developed in 1998 by Object Geometries, Ltd., which was later acquired by Stratasys. The process makes use of a printing head that can deposit material on the build platform much like a normal inkjet printer would. Thus, polyjet printers are a subset of inkjet printers.
The materials printed by polyjet printers must be photopolymers. These polymers will solidify when exposed to UV light. The printer works by dispensing multiple droplets of photopolymer onto the build platform and immediately passing a UV light source over the deposited photopolymer. The UV light solidifies the print layer, after which the build platform moves down by one layer height, and the next layer is then deposited. Polyjet printers have multiple print heads, which allow them to print multicolor and multi-material parts.
When compared to inkjet, polyjet is its subset that is focused only on printing with photopolymers. However, these photopolymers can have a wide range of properties and colors. Inkjet refers to the process of jetting ink, cultured cells, or even conductive ink from a range of nozzles.
To learn more, see our guide on PolyJet Technology.
What Are the Advantages of Polyjet Compared to the Other Ink Jetting Technologies?
Listed below are some advantages of polyjet compared to other inkjet-type printers:
- Polyjet can produce full-color parts without any need for post-processing, like painting or dying.
- Polyjet can produce multi-material parts. This is because each independent inkjet nozzle can deposit a different material. No other technology is capable of this feat.
What Are the Disadvantages of Polyjet Compared to Other Ink Jetting Technologies?
Listed below are some disadvantages of polyjet compared to other inkjet-type printers:
- Support removal requires a water jet which is not part of the machine. So a polyjet printer must be installed near plumbing and must have its own dedicated cleaning station.
- While polyjet printers can have large build volumes, they cannot utilize the entire volume the way multi-jet fusion printing can, which stacks multiple parts on top of each other.
Inkjet Definition and Comparison to Polyjet
Inkjet is a technology originally developed independently by Ichiro Endo at Canon and Jon Vaught at HP to print ink on paper. The technology was then adapted to 3D printing in 1998 by Object Geometries, Ltd., later acquired by Stratasys. There are two main styles of inkjet printers: material jetting and binder jetting. Material jetting deposits multiple droplets of photopolymers from a range of nozzles to print multicolor and multi-material parts—polyjet printing is an example of this. Binder jetting, on the other hand, deposits a binder onto a plastic powder to bond the plastic particles together. Alternatively, a fusing agent is deposited onto the powder to help melt it when a heat source is used to melt the plastic, as with the HP multi jet fusion 3D printer. Inkjet technology is also used to produce meat by depositing cultured cells one layer at a time to print a piece of meat.
What Are the Advantages of Inkjet Compared to Other 3D Printing Technologies?
Listed below are some of the advantages of the inkjet method compared to other 3D printing technologies:
- Inkjet printers can make use of multiple materials such as inks for printing on food, cultured meat, binding agents, or fusing agents. Other printing technologies are limited to one or at most two different materials at a time.
- Inkjet printers can print parts much quicker than most other technologies. The jetting process has been adapted by many other printing technologies, like MJF, for example, and each of these adaptations has the advantage of speed.
What Are the Disadvantages of Inkjet Compared to Other 3D Printing Technologies?
Listed below are some of the disadvantages of inkjet compared to other 3D printing technologies:
- Polyjet can only make use of photopolymers. While material development is ongoing, photopolymers are not as capable as other standard thermoplastics used in PBF (Powder Bed Fusion) and FDM (Fused Deposition Modeling) printers in terms of mechanical strength, fatigue resistance, and general chemical resistance.
- The cost of advanced photopolymers is much higher than that of standard plastic filament for FDM or powder for PBF printers.
| Attribute | Polyjet | SLS |
|---|---|---|
Attribute Print Resolution | Polyjet 55 microns | SLS 100 microns |
Attribute Can print large parts | Polyjet Yes | SLS Yes |
Attribute Can print in multiple colors simultaneously | Polyjet Yes | SLS No |
Attribute Can print in multiple materials simultaneously | Polyjet Yes | SLS No |
Attribute Can print elastomeric materials | Polyjet Yes | SLS Yes |
Attribute Minimum feature size | Polyjet 0.2 mm | SLS 0.75 mm |
Attribute Parts need support structures | Polyjet Yes | SLS No |
Attribute Largest Print Volume | Polyjet 1 x 0.8 x 0.5 m | SLS 0.55 x 0.55 x 0.75 mm |
Polyjet produces parts with good surface finishes in a range of different colors and material types whereas SLS tends to have rough matte finishes with limited colors.
Inkjet vs. Laser Technology: Technology Comparison
Inkjet 3D printing technology is based on paper printing technology. It works by depositing multiple dots of plastic onto a build platform. A UV light is then used to cure the plastic before the next layer is applied. In some cases, a roller needs to flatten the layer before the next one is printed. Laser technology like SLS (Selective Laser Sintering), on the other hand, uses a laser as a heat source to fuse plastic particles. Alternatively, a UV laser is used in SLA (Stereolithography) printers to print with photopolymers.
Inkjet vs. Laser Technology: Material Comparison
Inkjet style printers either make use of just photopolymers as is the case with polyjet or they can use food, binding agents, or even cultured cells. These photopolymers can be rigid, clear, elastomeric, or specially formulated to mimic the properties of some thermoplastics like ABS. Other inkjet-style printers make use of a combination of a photopolymer binder with a thermoplastic powder base, typically nylon. Multi-jet printing is an example of this.
Laser printers typically print with thermoplastic powders. These printers fuse them by sweeping a laser across a thin layer of plastic powder to fuse the particles into the shape of the part layer.
Inkjet vs. Laser Technology: Product Applications Comparison
Inkjet printers, including polyjet, are primarily used for functional multi-material and multicolor prototypes. Inkjet parts are also used for more practical applications like dental molds, lenses, seals, and surgical aids but are not suited to hard-wearing industrial applications like gears, for example.
Powder fusion bed laser technologies can print in more functional materials like nylon and even metal. This allows for the manufacture of end-use parts as opposed to just prototypes. This technology cannot print in multiple colors or materials.
Inkjet vs. Laser Technology: Print Volume Comparison
Both inkjet and laser technologies can print large build volumes and are intended for series production. The largest polyjet inkjet printer has a build volume of 1 x 0.8 x 0.5 m. Selective laser sintering machines have somewhat smaller build volumes, 0.55 x 0.55 x 0.75 m.
Inkjet vs. Laser Technology: Surface Finish Comparison
Inkjet technologies can produce parts with very smooth surface finishes. This is why they are so well suited for one-off functional prototypes. Laser-based printing technologies produce parts with a matte finish. The surface of a laser-printed part is also difficult to post-process if coloring is required and can only be colored by dying it.
Inkjet vs. Laser Technology: Cost Comparison
Inkjet 3D printers make use of specialized photopolymers that can cost up to $500 per kg. Laser technology like SLS makes use of thermoplastic powders, which are much cheaper to produce, and cost only $50 per kg, on average.
What Are the 3D Printing Technologies That Use Inkjet?
Many different 3D printing techniques make use of inkjet technologies. The most common are listed below:
- Polyjet: Distributes photopolymer onto a build platform using multiple independent nozzles, thereafter a UV light cures the photopolymer to produce a multi-material, multi-color part.
- Multi Jet Fusion: Multiple nozzles distribute a fusing agent and a detailing agent onto a thermoplastic powder to facilitate melting when an infrared heater is passed over the layer of plastic. The detailing agent ensures sharp part edges are maintained.
- Binder Jetting: Distributes a binding agent over a layer of powder to essentially glue the particles together, as opposed to melting them.
What Are the Similarities Between Polyjet and Inkjet?
Inkjet is the fundamental technology employed by polyjet printers. Polyjet printing is simply a type of inkjet technology.
What Other 3D Printing Processes are Comparable to Polyjet?
Below is a comparable process to polyjet:
- Polyjet vs. Stereolithography (SLA): SLA is a type of 3D printing technology that makes use of UV light to cure a single layer of photopolymer at a time. It does not make use of jets to deposit the material but rather places the build platform into a vat of photopolymer and projects the cross-section of the part onto the build platform to cure all the plastic. For more information, see our guide on Polyjet vs. SLA.
What Other 3D Printing Processes Are Comparable to Inkjet?
Below is a comparable process to Inkjet:
- Inkjet vs. Multi-Jet Fusion (MJF): MJF makes use of jetting nozzles to apply a fusing agent onto a layer of plastic powder in the shape of the desired cross-section of the current layer. A detailing agent is applied on all the edges of the layer to prevent the melt pool from oozing outside of the part boundary.
Summary
This article discussed the differences between inkjet technology and the polyjet 3D printing process. To learn more about inkjet technology and polyjet 3D printing, contact a Xometry representative.
Xometry provides a wide range of manufacturing capabilities, including 3D printing and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.
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