What is Multi Jet Fusion? How it works?
Multi Jet Fusion or MJF is a 3D printing process introduced by HP in 2016. This is one of the newer additive manufacturing processes design for industrial and commercial production. It combines technologies and techniques of various older 3D printing methods, such as SLS and PolyJet, to improve the overall quality and characteristics of the parts printed. MJF promises better printing time, mechanical properties, textures, etc.
MJF is a powder-based printing method, similar to SLS printing process, and it prints Nylon materials which gives it certain advantages which we will go through down below. It uses fine grained PA 12 Nylon material as the powder. The printer deposits fusing material (also called ink agents) on the powder which then forms the solid layers. It is evident that MJF is, to a large extent, an amalgamation of SLS, PolyJet and Binder Jetting printing processes.
MJF printer has two carriages which are perpendicular to each other. One carriage, called the re-coater, spreads a uniform layer of powder across the powder bed or build platform. The other carriage has a bunch of ink heads on it which disperses ink agents across the build platform accordingly. MJF has two types of ink agents, namely fusing agent and detailing agent. Fusing agent promotes energy/heat absorption at the centre of the part while the detailing agent is spread at the boundaries of the part to improve texture and provide smooth finish.
The printing process starts with the re-coater spreading a uniform thin layer of powder across the powder bed. This layer is generally 80 microns thick, which is the resolution of the printer. After spreading a uniform layer, the carriage containing the ink agents move across the build platform and deposit the ink agents accordingly. The build platform is then exposed to energy which initiates a reaction between powder and the fusing agent, causing the material to selectively fuse together to form the solid layers.
The fusing process requires precise temperature control across the build platform for best results. MJF uses closed loop thermal control system to measure temperatures at multiple points all across the powder bed. This data helps the printer to regulate the temperature of each sections according to their status.
Once the fusing of a layer is successfully completed, the build platform moves down by one-layer thickness i.e. approximately 80 microns and the re-coater spreads a new coat of powder across the build platform. This entire process repeats continuously till the entire part is printed.
MJF printed parts are functional and can be readily used straight out of the printer however, further post processing can also be done according to the requirements. It is also designed to have fast build speeds as it is targeted for industrial and commercial application. HP claims it to be many times faster than the traditional printing methods although, it is difficult to give an exact number because printing speeds of 3D objects depend hugely on the complexity, size and geometrical design of the part.
This printing method also uses a separate detailing agent whose sole purpose is to provide a smooth texture to the parts. Needless to say, they work great and parts printed using MJF printer do have smooth texture. The parts also have low porosity and high density because the powder and fusing agent form a strong bond with very little space in between them. This also gives the parts almost isotropic mechanical properties in all directions.
One of the biggest advantages of MJF is the use of PA 12 powder and printing Nylon materials. It is an engineering grade material and the printed parts are tough as well as durable. This printing process provides improved surface finish to the printed parts along with almost isotropic mechanical properties in all three directions.
As mentioned before, parts printed using MJF are ready for end use right out of the printer. MJF printers also support colour printing and HP is expecting to print parts at very high resolutions in the near future, which will increase the vividness and colour reproduction of the parts significantly.
Practically speaking, MJF has very little drawbacks attached to it. The biggest drawback can be termed as the lack of material options as only PA 12 powder can be used for printing. As the powder is also a proprietary product of HP, it can affect the cost of printing to some extent.
MJF is one of the latest 3D printing around, which means it incorporates and improves upon the already existing techniques and technologies. Since it is developed by HP, which is a trusted brand worldwide in the printer market, it brings widespread availability and support across the world. It is no wonder that MJF is one of the most used additive manufacturing methods in the world with a market research placing it in the fourth position of most used 3D printing processes.