PolyJet 3D Printing: Everything You Need To Know

polyjet

PolyJet is a 3D printing technology which has been around for 20 years and offers significant benefits over some other additive manufacturing technologies. But just how does PolyJet work? This guide is will explain the the technology’s history, preparation for printing, the PolyJet 3D printing process, post-processing, materials, applications, advantages and disadvantages, and more.

History of PolyJet

The 3D printing technology was developed by Israeli 3D printer manufacturer Objet Geometries back in 1998 in Rehovot. Rami Bonen, Gershon Miller and Hanan Gotaait collaborated to develop the technology. This led to significant investments in the company including a $15M investment in 2000 valuing the company at $36M. Objet Geometries has since merged with 3D printing giant Stratasys in 2011, who now offer PolyJet 3D printers as part of their range.

polyjet 3d printed parts
Parts 3D printed using PolyJet.

Preparation for PolyJet 3D Printing

As with all technologies, you need a 3D CAD file to 3D print. Usually an STL file, you will then need to send this file to a slicing program such as Cura or similar. These programs will then work out how to print your part based on the layer sizes and print settings you have chosen, including infill percentage, layer thickness, and more.

PolyJet Print Characteristics

PolyJet is one of the most accurate 3D printing technologies, with accuracy of up to 16 microns as well as the ability to create extremely smooth finishes. In addition, there are a wider selection of colors and materials available with PolyJet than other technologies. This means you can create multi-colored or even full-color 3D printed parts using PolyJet, and even have print parts with multiple different materials in different areas of the part!

Moreover, PolyJet is one of the fastest 3D printing technologies as, unlike Selective Laser Sintering for example, PolyJet prints as a line rather than at a fixed point. This also means PolyJet can print multiple objects in this line at the same speed as printing one object.

PolyJet uses the same liquid polymer resins as Stereolithography, which are jetted and then cured by being exposed to a UV light. This is somewhat similar to 2D inkjet printing, just with printing layers on top of each other to create a solid part rather than printing on paper.

polyjet uv light
PolyJet involves a UV light to cure resin, shown here.

PolyJet vs SLA

Since PolyJet uses the same resins as SLA, it could be said that the two processes are similar. SLA 3D printers however use vat polymerization technologies with far more heat than PolyJet, which uses lower temperatures and UV light to cure the resin.

PolyJet vs FDM

Fused Deposition Modeling is the most affordable and accessible 3D printing technology, whereas PolyJet is more expensive and industrial. A key difference is that parts created with PolyJet are noticeable less strong than those created by an FDM 3D printer. They lose strength over time, whilst FDM parts keep their strength and form. PolyJet is however much faster, offers better material and color options, and is more scalable.

PolyJet 3D Printing Process

The process is similar to inkjet printing, just instead of jetting drops of ink onto paper, PolyJet uses small nozzles to deposit droplets of liquid photopolymers onto the build tray. As it is being jetted, the material is simultaneously cured by a UV light. The polymers are heated to between 30-60°C to control their viscosity as they are jetted and printed.

Parts created using this process require supports if there are any complex geometries involved. These are required as otherwise the part can deform or warp, ruining the print. Supports are usually made from a different material which is designed to separate from the part when dissolved in water.

polyjet process

PolyJet Post-Processing

The supports used in PolyJet are more solid than supports used in FDM or SLA. This results in more material being used up than in these other processes, which can be expensive. The support removal process is very easy however, with supports being created from materials which dissolve in water.

Since no extreme heating is used there is very little warping or shrinkage of parts during the printing process. This helps reinforce PolyJet as one of the accurate and best surface finishes of all the 3D printing technologies. However, as parts get larger they can start to lose dimensional accuracy as the resins will start shrink as they cure. You must also take care when handling parts as they can easily warp due to exposure to hot or humid conditions.

Though PolyJet offers the best surface finishes of all additive manufacturing technologies, there are still a number of post-processing techniques available. These include sanding the part if the part is to be coated afterwards. Also, parts can be dyed and painted to change color.

PolyJet Materials

There are a huge range of materials available to be used with PolyJet, literally thousands. These range in color and chemical properties, from rigid, to flexible, to castable. To be considered a suitable material for printing, the material needs to have low viscosity and be able to be jetted in droplet form.

These materials aren’t cheap however. Resin cartridges can cost between $300 and $1,000 per kg. Ouch.

polyjet heart part
An accurate anatomical 3D printed model of a heart created using PolyJet.

PolyJet Applications

Since full-color and smooth surfaces can be achieved, PolyJet is the perfect method for detailed visual prototypes. This enables designers and engineers to see how their product looks up close, and assess the details. It’s often used in creating patterns for molds to be used in other processes such as injection molding. The original prototype is created using PolyJet, and is then used to create many more injection molded products.

Another common use of PolyJet 3D printing is to create realistic medical and anatomical models. These models can then be used to help teach students how to perform medical procedures on these models so they have more experience before performing real surgeries. This shortening of the learning curve is key in reducing fatality rates during surgeries.

PolyJet 3D Printer Price

Unlike FDM, PolyJet is mostly an industrial solution. PolyJet 3D printers start at around $6,000, and can cost up to $75,000 for the higher spec models. This, coupled with material costs, makes PolyJet an expensive 3D printing technology.

polyjet 3d printer
Well-known 3D printers include those made by Objet Geometries.

PolyJet Advantages and Disadvantages

PolyJet Advantages

  • The most dimensionally accurate 3D printing technology, up to 16 microns.
  • Smoothest surface finish, comparable to injection molding.
  • Fast and scalable. PolyJet can print multiple parts simultaneously without loss of speed unlike FDM or SLS.

PolyJet Disadvantages

  • Parts often have worse mechanical properties than parts creating with technologies such as FDM. They are vulnerable to heat and humidity, and can lose strength over time.
  • Expensive – printers are industrial machines and materials can cost $300-$1,000/kg.

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