Ultimate Guide to Multi-Jet-Fusion for Additive Manufacturing
The majority of procedures for using plastic and metal and in additive manufacturing are well-known. But how do they function? What are their advantages and disadvantages? What aspects of component design should be taken into account? And what uses are they appropriate for? In this article we will show you the additive manufacturing technology of Multi-Jet-Fusion (MJF).
What is Multi Jet Fusion (MJF)
Multi Jet Fusion (MJF), a 3D printing method for producing plastic components, was introduced by HP in 2016. It does not require lasers even though the printing medium is based on powder. Infrared light and two liquids are utilized as an alternative. In the beginning, the powder bed in the build chamber is heated uniformly. The different powder coats are applied one at a time. To achieve fine detail and a smooth finish, a heat retardant, known as the detailing agent, is placed around the curves of each layer and a heat conducting agent, known as the fusing agent, is injected where powder is to be fused. The agendas work in tandem with infrared lamps that are guided over the powder bed's surface to precisely fuse the particles.
properties and application of Multi Jet Fusion (MJF)
Because of the procedure, MJF provides efficient scheduling: The printing procedure for each layer takes exactly the same amount of time because the melting process does not rely on a laser movement, which changes depending on the region to be exposed. The printing time can be precisely predicted in this way.
The layers fuse together better and have a much lower anisotropy compared to FDM and also have a tendency toward SLS. Therefore, it is less important which way the components are oriented in the installation area. The capacity to generate more components of appropriate quality in a single construction process and shorter lead times benefit users. The fine-grained texture of the powder employed is what gives the components made by MJF their strengths. It allows for 80 m thin layers. Components printed as a result have a higher density and less porosity.
Additionally, the surface of the pieces is generally smooth from the start, thinner walls can be printed, and details can be resolved better. Like SLS, MJF gives the design flexibility associated with 3D printing and does not necessitate any support structures. This streamlines the component design when coupled with the low anisotropy.
The components' already highly smooth surfaces and the absence of supporting structures also frequently cut down on the amount of time needed for post-processing. For instance, sandblasting is frequently all that is required for working parts. The size of the components that can be manufactured, however, is limited by the available space.
All in all, as the pieces also have mechanical properties that are comparable to those of injection molded parts, MJF is perfect for prototypes for suitability and functional testing. The method can be used to create limited runs of intricate functioning parts and, in some circumstances, can be a more affordable option than injection molding. It is also appropriate for the mass production of customized goods.
Materials of Multi Jet Fusion (MJF)
Currently, let's take a look at with the two plastic of 3D printing materials: Ultrasint TPU 90A.01, a thermoplastic polyurethane especially created for the MJF process, and Polyamide PA 12, which is already well-known from laser sintering.
Due to their great strength, stiffness, and resistance to stress cracking, components produced of PA 12 are extremely durable. Additionally, they are extremely resistant to chemicals like oil. Components that have not been treated have a soft surface, no discernible layers, and a stone-grey hue. The components are black on the inside, so if they are colored appropriately, they will overlook slight dings in later use. It is simple to impregnate the material.
The material Ultrasint TPU 90A.01 is extremely flexible, tear-resistant, and permanently elastic throughout a wide temperature range after processing. It also has a high level of wear and abrasion resistance in products made from it. In contrast to PA 12, the material can only be easily coated using spray paint.
Designtipps
Practice has shown that the ideal wall thicknesses for PA 12 and Ultrasint TPU are 2 to 3 millimeters and 1 to 2 millimeters, respectively. If thinner walls are needed, they should have a wall length of 10 millimeters and be at least 1 millimeter thick in polyamide or at least 0.8 millimeters in polyurethane, also feasible to have even thinner walls, for hinges, for example, however it is advised to keep the section's length under 10 millimeters.
Another suggestion is to hollow out the components as much as possible, including the wall itself, at least from a wall thickness of 20 millimeters. This lessens sink marks that develop when material accumulates as well as saving material and lowering weight. The cavities must have at least two openings in order to be able to remove the powder effectively and fully. These should be at least 2 millimeters in diameter for PA 12 and at least 10 millimeters for Ultrasint TPU.
It makes logical to fill big holes with lattice structures in order to provide a component enough stability. To make it simple to later remove the powder with PA 12, a spacing of 1 millimeter between the grid struts is sufficient. Contrarily, with Ultrasint TPU, the separation must be at least 5 millimeters.
The size of the surfaces must be considered while utilizing polyamide in the MJF procedure. Due to the heat process and component alignment, they frequently dent. No flat surfaces bigger than DIN A4 are allowed. Smaller portions frequently have a distortion that can be made up for by an appropriate alignment.
