Knowledge Base

Working of PolyJet 3D Printers

Introduction to PolyJet

Polyjet (short for ‘photopolymer jetting’) 3D printers are a subclass of the Material Extruding / Jetting 3D Printers category. Material jetting is the name for any 3D printing technology that jets a liquid (the build material) from a print head, which is then solidified by UV light. In most material jetting processes, the build material is a photopolymer.
Stratasys, which is the leader in FDM 3D printing technology the world over, has acquired Objet to offer PolyJet (or PolyJet Matrix) printers. 
PolyJet 3D printers deliver high quality, multi-material printing and that too in multi-colour format. 

Working of PolyJet 3D Printers
At the core of PolyJet printers are the jetting heads. The jetting heads deposit a single layer of the build material (typically photopolymers) by sliding to and fro along the X axis. The depth of each layer of photopolymer deposited by each jetting head is selectively controlled by software. Raster scanning the head across the build platform delivers the capability to produce precise models. 
There are many ways in which PolyJet printers work, but one of the most popular techniques is spraying a liquid photopolymer from a multi-nozzle, inkjet-style print head. As soon as the droplets of these liquid photopolymers are jetted, they are immediately cured and hardened by an UV light. Once a layer is complete, the build platform drops along the Z axis, and the next layer of photopolymers is ejected from the heads. The process is repeated till the object is complete.

The raw material is stored in cartridges and is directly connected to the nozzles.

There are four important advantages of PolyJet 3D printers:

i. There can be a number of jetting heads that allow different build materials to be ejected at the same time. This makes it possible for 3D PolyJet printers to produce an object with different levels of flexibility in a single build. PolyJet 3D printers hence are useful to build complex objects with a smooth finish.

ii. As 3D PolyJet printers have multiple jetting heads, they allow for using photopolymers with different colours in a single build. You can therefore build multi-coloured objects easily.

iii. Since the build platform is typically lowered after an iteration of layer, there is more control over accuracy. High quality 3D PolyJet printers have an accuracy of 16 microns (0.016 mm). This allows for excellent detailing. Once a model is complete, it is perfectly structured and does not require additional curing or processing. If a support material is used, it is easily removable. In most cases, it can be simply washed off with water.

iv. There is a wide choice of raw material that is available for printing. At present, there are more than 100+ types of build material available for 3D PolyJet printers, and their number is increasing.

Versatility of PolyJet 3D Printers
In addition to creating liquid pools of photopolymer resins cured from the top or bottom of the pool by using external light sources, there are different techniques that can be used for PolyJet printing. Objet now Stratasys, for example, uses inkjet applicators to apply the resins. A low level UV light then immediately cures the sprayed layer into a solid state. This technique allows PolyJet printers to mix a flexible material and a rigid one to create models with variable strength and flexibility. You can hence use PolyJet printers to print complex objects such as a prosthetic. A prosthetic is a flexible joint sandwiched between rigid, hard-plastic body components, and it can be printed in one go using PolyJet technology. You can even mix and match’ a variety of build material – part rigid and part opaque as an example - to create exact replica of real life objects that use such material. Educational aids, toys for kids, body and dental parts are only a few examples where the versatility of PolyJet printers can be utilized.

PolyJet Printers – Build Material
The range of raw materials available today for 3D PolyJet printers is simply amazing. Apart from the standard photopolymers, the build material now includes clear, rubberlike and biocompatible photopolymers, and tough high-performance thermoplastics.
A few of the popular 3D PolyJet printing materials are mentioned below.

  • Digital Materials
  • Digital ABS Materials
  • High Temperature
  • Transparent
  • Rigid Opaque
  • Simulated Polypropylene
  • Rubber-like
  • Bio-compatible
  • Dental Material
What are Photopolymers?

Photo means 'light' and polymers are formed by amalgamation of many molecules (monomers). A photopolymer is a type of polymer that changes its physical properties when it is exposed to light. Photopolymers are  very popular and popular build material used by 3D printers, especially the PolyJet printers. Typically, 3D PolyJet printers use liquid plastic resins (a kind of polymers) that harden when exposed to a light source like UV light, lamps, projectors, etc.

Applications of PolyJet Printers

PolyJet 3D printers find use in many sectors that require achieving complex shapes, intricate details and delicate features. Automobile, architecture, industrial and educational sectors lead in the use of PolyJet printers in India. However, a key application of PolyJet 3D printers is in the healthcare sector. PolyJet printers enable surgeons to produce exact replicas of the organs that need replacement. Prosthetic limbs and joint replacement are a few examples where 3D printing is used actively. Another important sector that leverages the benefits of 3D printing is dentistry. Using 3D printers, dental labs can produce accurate crowns, bridges and a range of orthodontic appliances. While the use of 3D printers for dental applications is common in the developed nations, it is just catching up in India. So, the potential for this type of service is huge.

With the expansion of exciting new built material that includes the likes of chocolate (yes, chocolate!), the market for PolyJet and other 3D printers is all set to expand.