MJF 3D Printing
Multi Jet Fusion
Multi Jet Fusion (MJF) is an innovative 3D printing technology developed by HP that has gained significant attention in recent years, offering unique capabilities and advantages. In MJF, for each layer, a print head jets a binding agent onto a powdered material bed, selectively adhering the particles, and a heating element causes the fusion of the bound particles. With a moderate range of compatible thermoplastic materials available, MJF provides versatility for different applications. Post-processing steps can further enhance the appearance and functionality of MJF prints. Despite certain limitations, the speed, accuracy, and ability to produce complex geometries make MJF a compelling choice in the realm of additive manufacturing.
Materials
MJF and Selective Laser Sintering (SLS) share a common principle distinct from FDM, as both methods involve the deposition of a sintering of powdered material. Instead of using a heated extruder to deposit melted thermoplastic filament, MJF utilizes a print head that jets a binding agent onto a powdered material bed, similar to SLS. This binding agent selectively fuses the powdered particles, layer by layer, according to the digital design. Once a layer is complete, a heating element passes over the bed, causing the fusion of the bound particles and promoting layer adhesion. This unique approach facilitates the rapid production of precise, high-resolution parts with excellent dimensional accuracy.
Machines
MJF only offers a narrow range of material options, and HP manufactures the industry-grade machines for MJF printing, which are capable of large-scale production. Similar to FDM, thermoplastic materials are utilized in MJF printing. However, the specific powders used in MJF may differ. Common materials for MJF include Nylon 12, a versatile and robust thermoplastic that exhibits good mechanical properties and chemical resistance. Nylon 12 is suitable for functional prototypes, end-use parts, and applications requiring durability and flexibility. Other materials compatible with MJF include Nylon 11, Nylon 12 filled with glass beads or carbon fibers, as well as specialized powders for specific applications. The material selection depends on the desired characteristics of the printed object, such as strength, flexibility, heat resistance, and surface finish.
Post-Processing
Post-processing steps are also important in achieving the desired final results with MJF prints. MJF produces parts with relatively smooth surface finishes compared to FDM, but post-processing can further enhance their appearance and functionality, since most MJF parts are grainy before post-processing. After printing, excess loose powder needs to be removed from the printed object using compressed air or brushing techniques. Support structures, which provide stability during printing, also require removal. This process is typically facilitated by hand or with tools, ensuring minimal impact on the final part. Depending on the application and desired finish, additional post-processing steps can include sanding, painting, or applying surface treatments for texture and aesthetics.
Pros and Cons
MJF offers several advantages that make it a compelling choice for various industries. Firstly, MJF provides excellent production speed, permitting the rapid creation of parts, prototypes, and small production runs. This speed enables faster design iterations, reducing time to market. Secondly, MJF is capable of producing complex geometries and intricate designs with high accuracy and detail. This capability opens up new possibilities for customized and optimized parts with internal structures, such as lattices or honeycombs, resulting in lightweight and strong components. Moreover, MJF offers good surface quality and dimensional accuracy, minimizing the need for extensive post-processing. Finally, MJF benefits from the advancements in design and software tools, enabling seamless integration into digital workflows and enhancing productivity.