NANO PARTICLE JETTING: the future of additive manufacturing?

In 2016, XJet introduced Nano Particle Jetting technology (NPJ), a platform which relies on inkjet print heads to deposit layers of a liquid material infused with

ceramics/metal nano particles. Haim Levi, vice president of the manufacturing and defence markets at XJet, examines its features and benefits


ano Particle Jetting (NPJ) is based on the direct jetting of the build

material – which can be either ceramics or metals – using inkjet printing heads and liquid dispersion containing a vast amount of suspended nano particles of material. Using this process, there is no exposed powder in the process at any time, the build chamber is operating in normal atmosphere, with no inert gas, high pressure or vacuum needed, and at normal temperature. It is therefore highly safe and simple, with no need for special uniforms, complex filtering and sieving systems, with costly removal of residual powders.

THE BENEFITS Another major difference from common powder bed technologies is that we are using two different materials simultaneously – one is the build material, the other is the support material. We do not build support structures, instead we just fill out all the voids, cavities, overhangs and undercuts with the support material, which is fully dissolved automatically later on. The immediate benefit is that there are no restrictions on the geometry of the part usually imposed by support considerations. In addition, the support cleaning process is fast, simple and hands-free. Of additional benefit, layer thickness

is typically 8-10 microns, meaning that a very good surface finish is achieved


right out of the process, even in inclined and curved surfaces. Along with the fact that we use nano particles of material, we reach an accuracy of ±50 microns on dimensions of up to 50mm, while for larger dimensions we reach tolerances of ±100 microns. Minimum feature size is typically 100-200 microns. The final effect of these capabilities

is the real near-net-shape parts produced, which minimises the commonly required post processing steps, saving time and lowering production costs significantly.

THE PROCESS With the process itself, there are 24 inkjet printing heads covering the whole area of the printing tray. Moving back and forth across the whole build area, they jet the build and support materials simultaneously, each from its dedicated nozzles. After jetting the liquid droplet, containing the material nano particles, it falls onto the hot building tray (250˚C) where the liquid evaporates, leaving behind just the particles coated with a small amount of bonding agent. This allows them to bond to each other in all three dimensions, creating a cross section layer composed of areas belonging to the part and areas filled by support. This continues, layer by layer, until the task is complete. A typical job can include many parts,

either identical or completely different, allowing for high productivity when

filling out the full tray area with parts. By the end of the printing process,

either the whole tray or any individual part is then moved to the cleaning vat which is filled with water-based solvent. This dissolves all the support material, leaving the parts clean and ready for sintering. In the oven, the parts undergo a

typical cycle of sintering according to the material. It is well known that the sintering process can create some shrinkage of the part. Since we use nano particles, which fill out the part volume to high packing level, and the minimal amount of bonding agent present, we achieve a significantly lower level of shrinkage compared with other technologies. This shrinkage is isotropic, accurate, repeatable and predictable, so we take it into consideration when preparing the part for production.

INTO THE FUTURE We strongly believe that our NPJ technology has huge potential. It is the only technology existing now that could one day print multi-materials at the same time, creating real digital alloys voxel by voxel, resulting in new materials we have not yet seen before. It won’t be easy, and there are some big hurdles on the way, but there are some innovative solutions we have already started to explore. This is the future.

XJet 

With the process, there are 24 inkjet printing heads covering the whole area of the printing tray. Moving back and forth across the whole build area, they jet the build and support materials simultaneously

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