Material Jetting (PolyJet) 3D Printing: Everything You Need To Know
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PolyJet / Material Jetting is a 3D printing technology which has been around for 20 years. It’s very similar to standard inkjet printing, just with each printed layer stacking up to make a 3D part. It’s also one of the only technologies that allows for full color 3D printing, and can also print multiple materials at the same time.
But just how does PolyJet work? This guide is will explain the the technology’s history, preparation for printing, the Material Jetting 3D printing process, post-processing, materials, applications, advantages and disadvantages, and more.
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An Introduction to Material Jetting & PolyJet
A Short History
Material Jetting 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.
The venture proved successful, and by 2000 had received $15M investment valuing the company at $36M. In April 2012 it was announced that Objet would merge with Stratasys to consolidate both 3D printer companies‘ printer ranges. Stratasys now offer PolyJet 3D printers as part of their product range.
Is it PolyJet or Material Jetting? And are there any differences?
Both PolyJet and Material Jetting are the same technology. PolyJet is the name patented by Objet Geometries back in the late 1990s, whereas Material Jetting is the technical name for the process. This is similar to how Fused Deposition Modeling is also sometimes called Fused Filament Fabrication: one is a patented ‘brand’ name, one is a technical name.
We will use both interchangeably during this guide.
Preparation for PolyJet / Material Jetting 3D Printing
As with all technologies, you need a 3D printer file. Usually an STL file, you will then need to send this file to 3D slicer program such as Cura. 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 / Material Jetting 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. Two aspects of Material Jetting heavily influence part quality: jet droplet size (similar to laser spot size in SLA); and layer height.
Material Jetting is compatible with a great variety of materials and colors. With PolyJet, you can create multi-colored or even full color 3D printer parts using Material Jetting, and even have print parts with multiple different materials in different areas of the part! PolyJet printers can print a near infinite range of colors since they’re compatible with Pantone color ranges, much like a high quality 2D inkjet printer.
This is because of the multiple print heads — like dual extruder FDM 3D printers — meaning multiple materials can be printed simultaneously. Material Jetting’s success in full color printing appears to have influenced the development of Multi Jet Fusion 3D printing.
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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 / Material Jetting vs SLA
Since PolyJet uses photopolymers like SLA, so 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 (30-60C).
PolyJet / Material Jetting 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. Material Jetting is however much faster, offers better material and color options, and is more scalable.
PolyJet / Material Jetting 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 to protect the part from deforming or warping, and are printed concurrently with the part. Supports are usually made from a different material which is designed to separate from the part when dissolved in water. Once dissolved, you can usually barely tell there were any supports in the first place, with Material Jetted parts known for their smooth surface finishes.
PolyJet / Material Jetting Post-Processing
Supports in PolyJet are printed solid, so more material is used up than in FDM or SLA. This adds to the cost of Material Jetting, which can be very expensive. The support removal process is very easy however, with supports being created from materials which dissolve in water, with little evidence they were ever there afterwards.
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. Therefore, consider using other technologies such as Binder Jetting for very large parts. 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. However, with the ability to print in full color anyway, this isn’t always necessary.
PolyJet / Material Jetting 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 / Material Jetting Applications
Full color prototypes: 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 and functionality. 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.
Realistic models for education: another common use of Material Jetting 3D printing is to create realistic models, such as accurate anatomical models of human organs. These models can then be used to help teach students how to perform medical procedures 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 3D printers, 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 Material Jetting an expensive 3D printing technology.
PolyJet / Material Jetting Advantages and Disadvantages
PolyJet / Material Jetting Advantages
- Accurate: the most dimensionally accurate 3D printing technology, up to 16 microns.
- Smooth surface finish: comparable to injection molding, hence Material Jetting has applications in injection molding prototypes.
- Fast and scalable: PolyJet can print multiple parts simultaneously without loss of speed unlike FDM or SLS 3D printers.
- Full color: not many technologies can produce full color prints — just Binder Jetting, PolyJet and some Multi Jet Fusion printers. Add in the fact that multiple materials can be printed in the same part, and Material Jetting really stands out. Moreover, the fact that nearly infinite shades of color can be used make this extremely versatile for color printing.
PolyJet / Material Jetting Disadvantages
- Poor mechanical properties: parts often have worse mechanical properties than parts creating with technologies such as FDM or SLS. Like SLA 3D printed parts they are vulnerable to heat and sunlight, and can lose strength over time.
- Very expensive: they are industrial 3D printers and materials can cost $300-$1,000/kg, with industrial Material Jetting printers sometimes costing $100,000+.